Header tube length

[std]

How important do you think equal length tubes are.

The reason I ask is that I built a motor that I thought would pull pretty good up to 7000rpm. The owner got a set of headers made. The tubes go straight from the port to the collector. As you can imagine, the lengths are not even close.

The motor runs good in 1st but falls off at the top of 2nd and 3rd. I've seen similar cam/head combo work well.

Do you think I need to rework the headers or look in other areas?

[shaun callaway]

my opinion would be to rework the headers first then look in other areas.

[Dynoroom]

It's not the headers.
Look at the basics, fuel delivery, etc.
Give us more details on how it's running.

[squirrel]

The music analogy will be sure to confuse people! but the rest of it sounds reasonable :)

[RacerRick]

If it runs hard in 1st, then fall flat in later gears, its definately not the headers. I would be looking at fuel delivery. Might be emptying the fuel bowls.

Equal length headers are only worth a few HP in 99% of situations.

[JeffMcKC]

I agree the headers are not it.

The gear multiplication maybe helping cover up problems in second and third. High gear is where you find out if your making any onions or not.

[std]

The other problem I should have mentioned is the top of the air filter is at most 1'' from the top of the carb. It has one of those K&N filter tops but the hood sits right on the top. It doesn't seem like a good thing so we're going to modify the hood to get more clearance.

Unfortunately winter is about here so I can't much til spring. I'm just trying to get ahead of things, trying to think of what we should do.

[JeffMcKC]

The K&N fitler top is ok on a FI motor but not on a Holley, they do not like air coming in from the top it will take about 25 HP from it at a High RPM

[blu65ramb]

Jeff, thanks for that, i was going to try that on my holley carbed 406

[Eric68]

I agree with the others that the headers are not the problem in this case, but wanted to tell you that for best performance having the correct tube length (not necessarily all equal) and proper tube diameter is key. Same with collector, you need the right diameter and the right length.

I built a set of "equal length" headers for my car last winter and got them within about 4" from longest to shortest -- the average length is the correct length for my combo.

[KeithTurk]

Funny how most of us that have actually tried some silly stuff with Headers know the same thing...

Equal length... Tube size and so on... is often on the wrong side of the decimal point... while it's better to be "right" it simply doesn't hurt as much as you might think to be wrong...

Freiburger made 1013hp to the rear wheels through a set of 1 7/8" tubes... that were basically junk...

K

[DanStokes]

And the tubes on Dave Maty's Top Speed Shootout winner were cobbled together. I know - I was there. But they sure seemed to work just fine. I'm hoping to build an equivalent set for my Six from a set of Cliffords designed for a pickup.

I guess we'll see if they are better than a stock integral head (hard to be worse!)

Dan

[72_Ventura]

std-
What transmission is the car running? It sounds a little like it could be a TV cable issue in a 700-r4 or 200-r4 set-up. The fall off could be caused by late shift points. If you are running something with a TV cable (not the same as a kick-down) I'd mess with that some.
Just a thought...

[TC]

I'm calling fuel as the problem. What fuel pump is he running and what does he have the pressure set at. Also what size/make motor are we talking about.

[JeffMcKC]

I would say we need a lot more info to tell where the problem is, at this point its all just keyboard geussing.

Come on, give it up what, you got. LOL CID,CAM Spec, give us a list, I am sure we all would like to give our opinons.

[Eric68]

If you have to choose between tube length and tube flow pick flow.

Its nice to have tubes that are near the correct length for the combo, but don't compromise flow with tight bends in order to make them the right length. In fact, in a V8 equal length headers tend to make good power at the tuned RPM, but unequal length headers tend to have a wider power band because of the difference in tuning between cylinders without much (if any) sacrifice in peak power.

That is how headers that look like junk with unequal lengths make good power . . .

PS. 4 cylinders are a different story -- they have equal firing pulses and equal length tubes help a lot.

[MyStylesTheBomb]

Howdy. If y'all want check out www.headerdesign.com, it has a free registration to their on-line header calculator as well as some good tech. FWIW, Scott (found out about it in from a zine that will not be mentioned here)

[JeffMcKC]

I tend to over header mine, because I leave the Mufflers on it, and figure the rest of the exhaust is restricted enough.

I am sure theres more to be had, but think its way over credited with all the other factors involved. If your down to the headers, and everything else is Maxed out potential wise, maybe but time is better spent in other places by most people

[std]

I can't find the exact specs right now but here's some
418 windsor
Edelbrock heads-Ported
Edelbrock victor intake-ported and matched
.260-.270ish duration @.050
.630ish lift
C4 trans-manual valve body
3800 stall
I remember the cam card siad 7200rpm

[Eric68]

I would use a 1-3/4" primary tube header 32-34" long with a 3" diameter collector and 3" pipes.

A header with 1-7/8" tubes would be little on the big side but could be made to work also at the expense of some lower RPM TQ.

[RacerRick]

I find that the collector design (including extensions) has more influence on torque and hp than the tube length or even size. As long as the tube size and length is in the ballpark you will do well if there is a good collector design. Even just a set of 18" extensions can make a world of difference.

[BillBallinger Sr]

I find that the collector design (including extensions) has more influence on torque and hp than the tube length or even size. As long as the tube size and length is in the ballpark you will do well if there is a good collector design. Even just a set of 18" extensions can make a world of difference.


Me too. The secondary system can really gain a lot. I have headers that have 4 tubes that are roughly twice the length of the other 4, but there are minimal bends to the collector, the collector is long with a 5" taper. When you put 26" of pipe behind them its like a freight train (which is the difference in the pipe lengths ironically). The front four are 52", the back four are 26".

[JeffMcKC]

I dont see those heads and cam making power to much over 6000-6300 on a 418 motor they are both to small for that CID. I would use the 1 7/8. I dont think you have the exhaust port or lobe to support it

[SpeedZealot]

I will say my headers on the sb2 engine were completely cobled, 2 primaries were really screwed, but I still think a better set of bend would have yeilded little more than what we were making. 650rhp out of a small block, is fairly stout. I will say my 383 used to have the same nose over problem, mainly in second, and I could never figure it out. pulled just fine in 1-3-4 shrug, doesn't matter now i suppose though... I would think merge though. I have seen different merge collectors pick up 20rwhp which is substantial. I was working at a shop where Kooks headers was doing testing for the new c6 zo6, and all they were doing was sending headers with various types of merges. 5 sets later gained 20hp. So if you have money to buy every set of merge out there, then I would try that, otherwise, its only 20hp, and a 25shot of nitrous is a pretty easy way to solve the problem

[joe_rocket45]

There's a great thread here, but you need to register...
http://speedtalk.com/forum/viewtopic.php?t=8305&start=0

the short story is these log headers lost 14 hp vs a set of well engineered nascar headers on a sb2

here's a pic of them:
http://exhaust.fastmail.fm/forumpics/logmanifold.jpg

[KeithTurk]

Joe that really was interesting... read all 5 pages of it... crazy ass folks...

So basically it's confirming my thoughts in that Headers are highly over rated as long as they are big enough. Just add a bit more Nitrous or 1/4 pound of boost and call all that thinking a day... make your exhaust as pretty or ugly as you want.. it's all just stuff that takes gases away..

The biggest reason I'm interested is that I'm trying to come up with something that is a bit different on the 32 roadster I'm finishing... and this is one of the area's that isn't done yet... so it's open for interpetation.

Keith

[SpeedZealot]

will bundle of snakes fit on the 32? :)

[RacerRick]

Go all out on the headers!

180 degree stepped anti reversion headers headers with a 4-2-1 merge reducer, and 12 degree cone collector! I bet they even make 1-2 more HP that a real good standard off the shelf header.

[BigBlockMopar]

I've been making my own headers for my '64 Chrysler some time back but couldn't help wondering about the length-difference I ended up with. Look at the far most right tube, and the 3rd from right.

If one tube scavenges the gasses better then the other, wouldn't it lean out 1 cylinder?


http://img.photobucket.com/albums/v628/BigBlockMopar/1964ChryslerNewYorkerSalon/Engine-Headers/AUT16601.jpg

[JeffMcKC]

Which comes back to my way of  thinking a little big will hurt some, but to small will kill you. Mine are 2 to 2 1/8 into 4 inches

[jimmy-six]

When you fimally use up all your ideas on how to get the exhaust out of a cylinder it will time to go to the pros. On my GMC 6 we have shared ports for part of the exhaust system. I swallowed my pride took out my plastic and had Burns Stainless design and build the headers for my LSR roadster.

One of the top inline guys in the country saw them and he stated to others looking in at my engine and said "when I run out of ways to get flow out the heads you do that" pointing at my exhaust system.
Triple step/double merge/megaphone is the right thing right now...Who knows what will be the next way.

The header design site helped me too...Good Luck

[Eric68]

If one tube scavenges the gasses better then the other, wouldn't it lean out 1 cylinder?


Not better, just at a different RPM. Length shouldn't lean out a cylinder, only give it a different "tuned" RPM.

Check out the great lengths I went through TRYING to get mine all the same length (as well as making them fit the chassis and have access to spark plugs) The number 7 cylinder was the real sun-of-a-gun. # 8 I just gave up on and left it a little short LOL

http://i29.photobucket.com/albums/c274/Eric68/IMG_0991.jpg?t=1195611062

[milner351]

eric68 you MADE THOSE?

that seals it - I've been working on cars since '85 and I'm a total freaking hack compared to you guys, I'm not even worthy to be typing on this thread with welders and fabricators of this magnitude.... sheesh!


I have a heckofa dilema - a ranger with a cleveland - I need to build a set of headers that go outside the frame rails.... the ones in it now are a bit of a mess though I'm sure they took someone a long time to build- it's just too tight to the frame and trans.

any suggestions on header hits? or is it best just to get a few sets and swap meets, cut them up and make it work?

What mig wire diameter and settings would you pro's recomend (lincoln SP200)

[std]

Interesting thoughts on this.

This sounds like a good dyno test for CarJunkie.

[Scott Liggett]

Interesting thoughts on this.

This sounds like a good dyno test for CarJunkie.


Yep, second that.

[BigBlockMopar]

I have a heckofa dilema - a ranger with a cleveland - I need to build a set of headers that go outside the frame rails.... the ones in it now are a bit of a mess though I'm sure they took someone a long time to build- it's just too tight to the frame and trans.

I once bought a cheap set of headers at Summit which, at the time, where advertised for 'Big Chrysler', but turned out to be very wide Motorhome-headers.
Maybe these will give you a good start in the right direction?

http://img.photobucket.com/albums/v391/MoparHemi/440-Engine/AUT16253.jpg

[Eric68]

eric68 you MADE THOSE?

that seals it - I've been working on cars since '85 and I'm a total freaking hack compared to you guys, I'm not even worthy to be typing on this thread with welders and fabricators of this magnitude.... sheesh!


I have a heckofa dilema - a ranger with a cleveland - I need to build a set of headers that go outside the frame rails.... the ones in it now are a bit of a mess though I'm sure they took someone a long time to build- it's just too tight to the frame and trans.

any suggestions on header hits? or is it best just to get a few sets and swap meets, cut them up and make it work?

What mig wire diameter and settings would you pro's recomend (lincoln SP200)


Thanks, but I'm just a persistent hack -- nothing done with mine that you can't do. I used a 110V MIG (yes a MIG) with .030 wire. Just spent a lot of time getting fitment just right and grinding down welds when I had it fit up like I wanted.

I would highly recommend Nitroplate for header coating -- they did mine and they still look very nice after a year of use and abuse. The finish does naturally dull a little after seeing some heat.

I started with a box of bends and made flanges to fit my heads, that would work for your ranger but plan out your tube route carefully because it doesn't sound like you have much room. I used a piece of small copper tubing to help plan the route for my tubes.

[KeithTurk]

Eric's junk really is that nice... the whole car reeks of to much time on his hands.... or YEARS of whittling ...

Lots of attention to detail... ( which truly makes most cars.. )

K ( I've never seen Eric with a farm animal... )(notice the Mopar guys don't talk in Farm animals? )

[dieselgeek]

now, I am no exhaust guru. but in my short time in CA I saw two different people who are heavily into exhaust, doing dyno testing and definitley picking up power with different placement of components...


the first time, a guy was adjusting the location of the X-pipe on a 2nd gen camaro 400ish hp SBC and he was picking up 50+ whp on a legit chassis dyno with a new location... He was studying the "color" the exhaust turned, downstream of the x-pipe.

second time, Tom Habrzyk (wicked smart EFI guy) was doing a smallblock (super stocker?) in a car on a chassis dyno, and was taking EGT and AFR readings from every cylinder, with high quality equipment (not 8 LC1's), and was showing me *huge* differences in AFR at each cylinder because of the header design having drastic length differences. He showed me this because I shared the opinion exhaust wasn't that important. At peak HP he had some cylinders as rich as 11.5:1 while others were in the 13s. Sure you can tune an engine to run "safely rich" so no individual cylinder is too lean... but in his case, it was making a *huge* difference.

Now, I have no clue if/how that affects any of the applications we're talking about here, but I definitley trust what I was looking at.

Freiburger knows Tom Habrzyk, and would back me that this guy knows his sh|t

-scott

[RacerRick]

If you are running a car in the Superstock ranks where 20hp is the difference between low et and not making the field, I can see where intensive exhaust research has benefits.

Its just that in a $$/hp level, its very low on its return once you get past a decent set of store bought headers and a well thought out exhaust system.

Also, on a highly tuned exhaust system, components in the wrong place will kill it. On an average system, there is quite a bit of wiggle room. An H pipe can be quite a bit out from its optimal placement and still show an increase. The difference between a highly tuned system and a good average system is probably about 25hp and $4000. I can make a lot more than 25hp given $4000 since I do not have a strict set of rules I have to abide by. And by system, I mean everything from the exhaust valve to the exhaust tips.

A badly designed exhaust system is a badly designed exhaust system no matter what, and will cost you tons of hp.

[Eric68]

Yeah, for $4,000 you could put a big honkin' Procharger on it and make another 400 HP. LOL

[dieselgeek]

Yeah, for $4,000 you could put a big honkin' Procharger on it and make another 400 HP. LOL


This guy wasn't getting paid $4000, and a 400hp engine picking up 15-20% peak power just by playing with an X-pipe's location, sure seemed like it was worth the effort to me.
True, the guy (Tim Cottrel) was/is a header designer...

[JeffMcKC]

Peak maybe, but he may have just moved it, and lost average HP across the band, and did he take the time to optimize every change he made, if so thats a lot of Dyno time. 25-50 HP in Super Stock thats a ton. I would love to see what ET change it made at a track. I know a head guy right now, he gets 50 more HP on a SB2 head than CFE's do on a dyno, runs 5 MPH better at the track, no ET movement yet. I know it there, but you got to find it, and be able to use it. ET wins the race not Dyno's

[min301]

Some difference may be found in the collector type, length tuning, and the primary and secondary pipe diameters.

Headers work by lowering the restriction, and by scavenging the pulses.
Some designs work better than others, and some are strictly race only, such as 180 degree headers.

[dieselgeek]

Peak maybe, but he may have just moved it, and lost average HP across the band, and did he take the time to optimize every change he made, if so thats a lot of Dyno time. 25-50 HP in Super Stock thats a ton. I would love to see what ET change it made at a track. I know a head guy right now, he gets 50 more HP on a SB2 head than CFE's do on a dyno, runs 5 MPH better at the track, no ET movement yet. I know it there, but you got to find it, and be able to use it. ET wins the race not Dyno's


I'm not sure what your point is, I'm not claiming dynos win races... also, peak HP is peak HP and in a drag car that keeps the engine in the powerband the entire distance of the track, this is a case where "moving" or "losing down low" doesn't mean anything. Bear in mind that, for your comb, maybe exhaust is not a big deal. But for plenty of others that need to take their combination to the absolute maximum, header length, tuning etc. can make a huge difference.

-scott

[RacerRick]

Yeah, for $4,000 you could put a big honkin' Procharger on it and make another 400 HP. LOL


This guy wasn't getting paid $4000, and a 400hp engine picking up 15-20% peak power just by playing with an X-pipe's location, sure seemed like it was worth the effort to me.
True, the guy (Tim Cottrel) was/is a header designer...


Dynotime around here is about $800 a day, plus the labour and materials...it adds up real fast when designing an entire exhaust system and testing it for optimum power. It would take a week to come up with optimum header size and length, collector size and design, and then the actual exhaust pipes, mufflers, crossover, etc for an exhaust system at a minumim. So your are in $4000 just for the dyno time on the chassis dyno!

And for an engine to pick up 20% power by *just* changing the location of the X-pipe means that most likely he was tuning out a resonant wave in the exhaust system that was causing reversion. He was tuning the wave to help scavenging instead of causing reversion

Anti-reversion headers, a 4-2-1 merger collector design, resonators, or any myriad of other ways would have caused a similar power increase. The way the guy you are talking about did it is a really good way, because as long as it doesn't open up a hole in the torque curve by overscavanging and sucking the A/F mix right out into the exhaust during overlap, it will help power by reducing pumping losses.

Thats a sharp exhaust guy.

[dieselgeek]

well, I was the guy running the dyno for the camaro that was picking up 50+whp... and it took them three hours including the time he spent moving the X pipe. You are correct though, the whole thing started with a comment (while the car was already on the dyno) about "the X-pipe is killing your power the way it's set up" and thus, the tuning experience...


as for Tom at A.P.E. (I'm surprised he's not on here yet), his case was the NHRA stocker where unequal lengths were giving him huge AFR differences.


Those are really the only two times I've ever observed someone *practicing* exhaust tuning, as opposed to discussing it during bench racing or online - and both times looked like good reasons to pay attention to header & exhaust tuning to me! As for myself, I don't even have a project but I spend a lot of time tuning other peoples' projects, and when they ask me my opinion abotu exhaust I simply share my two factual experiences and move along... :)

[Eric68]

BY the way while we're on the subject of dyno's vs ETs . . .

Keep in mind that dynos load an engine differently than they are loaded while running down the track. Not saying dynos aren't useful or don't show reality, just that there are some subtle differences between best numbers on the dyno and best numbers in a car going down the track. A couple components that I personally believe act differently on the dyno vs reality are headers, carb sizes, and rotating assembly weight.

PS. thanks for the kudos Keith. And yes, I am obsessive compulsive.

[RacerRick]

well, I was the guy running the dyno for the camaro that was picking up 50+whp... and it took them three hours including the time he spent moving the X pipe. You are correct though, the whole thing started with a comment (while the car was already on the dyno) about "the X-pipe is killing your power the way it's set up" and thus, the tuning experience...


as for Tom at A.P.E. (I'm surprised he's not on here yet), his case was the NHRA stocker where unequal lengths were giving him huge AFR differences.


Those are really the only two times I've ever observed someone *practicing* exhaust tuning, as opposed to discussing it during bench racing or online - and both times looked like good reasons to pay attention to header & exhaust tuning to me! As for myself, I don't even have a project but I spend a lot of time tuning other peoples' projects, and when they ask me my opinion abotu exhaust I simply share my two factual experiences and move along... :)


And this bring us back to a previous statement where highly tuned exhausts have to be just right or there ends up being huge power losses...while "good" exhausts have lots of wiggle room without loosing (or really gaining) power.

Still - 3 hours to move one component, and then the rest of the system needs optimzing again...you can see how with testing it can easily take a week.

I did all my testing at the track, and have found measurable gains in exhaust tuning, but as you can guess my gains where getting rid of problems more than tuning the system. I reached a plateau after a while. And an off the shelf TTI exhaust system ran exactly the same as the one I spent an entire summer testing and tuning at the strip. Same MPH almost exactly.

[DanStokes]

eric68 you MADE THOSE?

that seals it - I've been working on cars since '85 and I'm a total freaking hack compared to you guys, I'm not even worthy to be typing on this thread with welders and fabricators of this magnitude.... sheesh!


I have a heckofa dilema - a ranger with a cleveland - I need to build a set of headers that go outside the frame rails.... the ones in it now are a bit of a mess though I'm sure they took someone a long time to build- it's just too tight to the frame and trans.

any suggestions on header hits? or is it best just to get a few sets and swap meets, cut them up and make it work?

What mig wire diameter and settings would you pro's recomend (lincoln SP200)


Mil -
I have a buddy in Romulus (or is it Taylor - they all melt together over around the airport) who makes headers, and he's WONDERFUL. His name's Steve Smith, and the company is Specialty Fabrication. He did a bunch of work for me when I was at the EPA, and he's one of the few people in the world who can make double wall headers that won't crack. Give Steve a call and see what he'd charge you. The headers will be pretty when done. He usually makes them out of stainless. BTW - he built headers at Watson Engineering for years, but left to start his own shop.

Tell him I sent you, and he'll charge you double
Dan

[dieselgeek]

Keep in mind that dynos load an engine differently than they are loaded while running down the track. Not saying dynos aren't useful or don't show reality, just that there are some subtle differences between best numbers on the dyno and best numbers in a car going down the track. A couple components that I personally believe act differently on the dyno vs reality are headers, carb sizes, and rotating assembly weight.





well, to continue the theme of taking this thread waaay off toopc, I thought I'd point out that your info is correct only in the world of Inertia chassis dynos. And frankly, I wouldn't recommend someone waste the time on one.

Loadbearing dynos, like a Mustang or superflow or new dynojet with PAUs... different story altogether. YOu can hit *every* possible load/rpm combination you'll see on a track, including differing manifold pressure...
-scott

[min301]

Off topic, what's that? :D

[std]

What was my question?

[BillBallinger Sr]

::) Hmm. Its in there somewhere.


In my experience the primary tubes in a perfect world would be perfect, straight out no bends and four feet long tapering to a cone with complimentary scavenging 360° cylinder pulse phased exit. Well that chassis doesn't exist, or a V8 even that makes that possible. Anything you do will be a compromise.

My position is that you need to get the exhaust to the collector as quickly as possible. If you make two pipes for a pipe organ, one twice as long as the other, they will make the same note, so in sonic terms they are equal. The octave may differ, but sonic resistance to the air moving will be in tune.

At the secondary where they join, the signal will be the same, but the stack heat of the shorter pipes will be higher, this is where secondary tuning comes in. The extensions and the X pipe allow the gasses to equalize, and the scavenging of the whole bank is made stable by this allowance.

I call it an allowance, because that is what it is. You are equalizing a compromise to eight perfectly tuned pipes in unison, from eight pipes that have differing heat and sonic signatures. Tuning the pipes to twice or half length (however you want to look at it) are a device to make a sonic signature that is equal, and leave the heat signature to the secondary. The Pythagoreans quantified this phenomenon mathematically, but It would take me days to find it. It applied to pretty much any sound at pitch.

[DanStokes]

Dang, Bill, you is a bright guy! I tend to forget my music/sound physics when thinking about air flow (either in or out) and of course they apply perfectly. Thanks for the input.

Dan

[dieselgeek]

Any bench racer who cites Pythagoras has my attention. Definitely!

[cudadon]

The K&N fitler top is ok on a FI motor but not on a Holley, they do not like air coming in from the top it will take about 25 HP from it at a High RPM

That may be the problem. I had a solid lid too close once, and it would launch ok. But when it needed more air at the top of the gears it would choke it down. Took the lid off and it was fine! Don

[p302stang]

timing? is it getting full advance? Alsoi would try running the car san hood to see if your choking it like you think you may be. a friend of mine had that problem with a big block mustang the hood was to close to the carb killing power big time.as for the k&n air filter lid and loosing 25 hp what was this on i ran my old mustang with the k&n lid with a regular lid and with no air cleaner at all at the track and the only change was with no air cleaner it went a bit faster with nothing and ran the same with either filter setup.

[Eric68]

Keep in mind that dynos load an engine differently than they are loaded while running down the track. Not saying dynos aren't useful or don't show reality, just that there are some subtle differences between best numbers on the dyno and best numbers in a car going down the track. A couple components that I personally believe act differently on the dyno vs reality are headers, carb sizes, and rotating assembly weight.





well, to continue the theme of taking this thread waaay off toopc, I thought I'd point out that your info is correct only in the world of Inertia chassis dynos. And frankly, I wouldn't recommend someone waste the time on one.

Loadbearing dynos, like a Mustang or superflow or new dynojet with PAUs... different story altogether. YOu can hit *every* possible load/rpm combination you'll see on a track, including differing manifold pressure...
-scott


Well, we'll have to agree to disagree because I do not believe and cannot be convinced that a dyno can EXACTLY simulate actual track conditions and loading. It just isn't the same as driving it down the track no matter how hard you try. Sure you can come reasonably close, close enough to make it worth while, but it still isn't exactly the same. I'll stand by my original comment and insist that my statement and my info IS correct.

If you are not convinced yet, here are some things for you to think about.

What about simulating tire spin on a dyno? We all know that all cars spin at least a little when launching.

What about simulating the effects of airflow through the engine compartment on a dyno? ie: air flow across a carburetor or through an airfilter at different speeds.

What about simulating different gears and loading from the TQ converter at launch?

What about simulating G forces? Simulating oil slosh in the oil pan, fuel slosh in the float bowls, and fuel slosh in the tank?

Hope you see where I am coming from now . . . its a lot more complicated than "inertia vs. load bearing"

[dieselgeek]

Keep in mind that dynos load an engine differently than they are loaded while running down the track. Not saying dynos aren't useful or don't show reality, just that there are some subtle differences between best numbers on the dyno and best numbers in a car going down the track. A couple components that I personally believe act differently on the dyno vs reality are headers, carb sizes, and rotating assembly weight.





well, to continue the theme of taking this thread waaay off toopc, I thought I'd point out that your info is correct only in the world of Inertia chassis dynos. And frankly, I wouldn't recommend someone waste the time on one.

Loadbearing dynos, like a Mustang or superflow or new dynojet with PAUs... different story altogether. YOu can hit *every* possible load/rpm combination you'll see on a track, including differing manifold pressure...
-scott


Well, we'll have to agree to disagree because I do not believe and cannot be convinced that a dyno can EXACTLY simulate actual track conditions and loading. It just isn't the same as driving it down the track no matter how hard you try. Sure you can come reasonably close, close enough to make it worth while, but it still isn't exactly the same. I'll stand by my original comment and insist that my statement and my info IS correct.

If you are not convinced yet, here are some things for you to think about.

What about simulating tire spin on a dyno? We all know that all cars spin at least a little when launching.

What about simulating the effects of airflow through the engine compartment on a dyno? ie: air flow across a carburetor or through an airfilter at different speeds.

What about simulating different gears and loading from the TQ converter at launch?

What about simulating G forces? Simulating oil slosh in the oil pan, fuel slosh in the float bowls, and fuel slosh in the tank?

Hope you see where I am coming from now . . . its a lot more complicated than "inertia vs. load bearing"



I'm not talking about oil slosh in a sump, we're talking about tuning for maximum power through the RPM band. I can assure you, a knowledgable tuner and dyno operator can and will make sure that every possible load combination that your engine can ever see, is seen on the dyno. I am talking about any combination of manifold pressure (load) and RPM. The most important part is the ability to "hold it there"

I know what you mean, however, about other things we "can't" simulate, for example an auto trans with a drag-style torque converter will read WAAY low power numbers (who cares IMO)... but as far as power tuning, I can guarantee you from thousands of dyno pulls and much experience, that if you can tune your carb or EFI setup for proper AFR and timing at all possible loads, the car is going to be quicker at the track. I've never had it not work out this way.


I wish I had CDMBill's dyno sheet where we compare AFR to RPM. Interesting things going on there during transitional throttle. Now, to be able to fully map his EFI combo, we had him install the manual transmission so that we had no converter slip to deal with for tuning, and ask him if it made a difference. Beside the top end power he gained, there was a large torque increase. The idea that you can tune a combo finer ont he track than at the dyno - with regards to power - is definitley incorrect. I'm not saying you can "simulate all conditions" you'd see at the track, on the dyno - but that also means you can definitely not "simulate" all the conditions the engine sees on the street, at the track either. FOr example, if you're all tuned and great for a quarter mile pass in a given density altitude, what happens on the street if you're running WOT in a slight downhill or uphill grade? the engine will see load conditions it won't see at the track. So if your presumption is that track tuning is the best thing goin, well, that's fine if you always race on perfectly level conditions, at the exact same barometric/weather conditions, etc. which never happens. Thus, in my opinion, dyno tuning allows you to place varying loads on your powertrain (and hold it there long enough to tune it there), better than any track conditions.

If it weren't for 40+ cars I've dynod in the past year ALL picking up trap and ET improvements after steady state tuning, I'd be inclied to take your side, but the experience doesn't lie. Every single car we tuned on the loadbearing dyno this past year, picked up ET. Some of them, a lot. Ask Chad.

-scott

[TC]

I'll add a little to this, how about tuning for the effects of a ram air set up. You sure the hell aren't going to be able to do that on a dyno. Now I'm not saying dyno's aren't good, IMO you can use them to get your car to a baseline starting point and then do the fine tuning at the track.

And one more thing what good is a dyno anyways, since different dyno's will give the same car different HP figures. To me if you really want to know how much HP your making, it's all in your trap speed and MPH. Cause that my friends tells exactly how much HP your putting to the ground. Remember HP isn't everything, because if you can't put it to the ground, your just loosing time.

[dieselgeek]

I'll add a little to this, how about tuning for the effects of a ram air set up. You sure the hell aren't going to be able to do that on a dyno. Now I'm not saying dyno's aren't good, IMO you can use them to get your car to a baseline starting point and then do the fine tuning at the track.

And one more thing what good is a dyno anyways, since different dyno's will give the same car different HP figures. To me if you really want to know how much HP your making, it's all in your trap speed and MPH. Cause that my friends tells exactly how much HP your putting to the ground. Remember HP isn't everything, because if you can't put it to the ground, your just loosing time.



None of us here are arguing about measuring horsepower on a dyno - a dyno is a tuning tool.

So, what good is a dyno? real simple: if you can take your car to one, do some tuning, and pick up ET and trap speed - then it's good right?

Perhaps we should qualify this thread by first asking, (a) who here has tuned their car on a loadbearing dyno and (b) was it worth it? Because I have yet to tune a drag / street car in the past couple years, that didn't pick up ET/trap when we were done with it. Unless it was a car that wasn't trying for better WOT power, etc. (i.e. testing an intake, etc.). Perhaps your personal experience varies, which may mean you should seek out a different tuner. but anyone in this thread whose going to argue that dyno's aren't worth the $$$ better have some *serious* experience to back up that comment. Same thing with the headers, seems all the people who don't think exhaust tuning is an important part of powerband tuning, have any significant examples why they can show us it's a waste of time. Meanwhile, everyone I've seen take a serious approach to exhaust tuning, benefitted. So perhaps this is one of those "exhaust and dyno tuning sucks because I never tried it" things... you decide. but for the guys reading this wondering if they should try dyno or exhaust tuning, I think they should make sure whomever's opinion they believe, has test results to back up the claim.

[Eric68]

I think you are putting words in my mouth -- I never said dynos suck or are not worth the $s. In fact I said the opposite -- I said that they ARE worth it. I only said that there are some subtle differences that dynos cannot simulate -- and that is FACT. No need to get your panties in a knot over that . . . and I would agree that most people that go to the dyno will pick up ET, I won't argue that.


The idea that you can tune a combo finer ont he track than at the dyno - with regards to power - is definitley incorrect.

Again, we'll have to agree to disagree. When I switched to E85 I put it on the dyno and found the AF that made best power, YES it went faster at the track. THEN I tuned some more with my LM1 at the track and it went quicker yet. By the way, the AF that made best power on the dyno DID NOT go fastest at the track!!! By the way, there are plenty of reputable DYNO TUNERS that will tell you the same thing.

You never bothered to address any of my questions from my previous post which leads me to believe that you cannot. I will ask one more time . . .

How do you simulate RAM AIR on a dyno?

How do you simulate the effects of G forces on the fuel and oil system on a dyno?

What about simulating the effects of tire spin and TQ converter loading on a dyno?

[dieselgeek]

I think you are putting words in my mouth -- I never said dynos suck or are not worth the $s. In fact I said the opposite -- I said that they ARE worth it. I only said that there are some subtle differences that dynos cannot simulate -- and that is FACT. No need to get your panties in a knot over that . . . and I would agree that most people that go to the dyno will pick up ET, I won't argue that.


The idea that you can tune a combo finer ont he track than at the dyno - with regards to power - is definitley incorrect.

Again, we'll have to agree to disagree. When I switched to E85 I put it on the dyno and found the AF that made best power, YES it went faster at the track. THEN I tuned some more with my LM1 at the track and it went quicker yet. By the way, the AF that made best power on the dyno DID NOT go fastest at the track!!! By the way, there are plenty of reputable DYNO TUNERS that will tell you the same thing.

You never bothered to address any of my questions from my previous post which leads me to believe that you cannot. I will ask one more time . . .

How do you simulate RAM AIR on a dyno?

How do you simulate the effects of G forces on the fuel and oil system on a dyno?

What about simulating the effects of tire spin and TQ converter loading on a dyno?


I can assure you it's not my panties that are in a bunch. I wear boxers! I think one thing we can agree on is miscommunication here.

I said clearly above, "with regards to power" - I don't remember claiming to be able to simulate G-forces on a chassis dyno, what's your point? Do you think that I am saying we should all not go to the dragstrip anymore?!? please, clarify.


Also, I'm not answering your "other questions" up until this point because they're completely unrelated to what I am arguing here, which is, Chassis dynos are great tools for tuning power. You seem to agree with me (now), so what are we arguing again?


I'll take a shot at them anyways, since you "called me out:"

Ram Air: every car I've ever seen with the capability to build any kind of manifold pressure with a Ram Air setup has been tested on a dyno. It's not hard to get enough fan in front of the car, or even pipe pressurized air into an intake, if you're that serious about ram air. I had a fan that would do a decent 130mph breeze, but never ran into anyone who complained about an inability to test that on a chassis dyno (until I met you anyways)

G-forces. How do you simulate these? Tip the car on it's rear? hell if I know. Last time I checked, we used dynamometers to maximize power at all points in the RPM/load range. Which is what I have been arguing the whole time. I think someone here just likes to argue - and this thread is getting tiresome.


One more question though, what brand of dyno did you use for your " best AFR didn't make best power" reference above?

[dieselgeek]

oops, forgot the "Tire Spin / torque converter loading"

Again, loadberaing dynos allow you to set the load the converter sees. It took me a while to learn how to do this properly (ask GoatRacer), but a simple sweep rate adjustment allows you to set the load... as for tire spin, what does that matter if the quest is simply to maximize power throughout a load range?

All a good dyno is doing, is verifying (and letting you tune for) operation at as many loads as you can find. I didn't say they're better than the track, I sad - for maximizing power - they're better than track tuning. Sure, some guys are wizards (you) and may not need them. Also, in my post above where you told me I was "putting words in your mouth" - take a look more closely BEFORE clicking on the reply button, I wasn't even quoting or replying to you. Don't worry, I have plenty of respect for you - if that's what this is about. Or is it a redux of the "sandbagging" post? sorta starting to sound like it to me :)

[Eric68]

I'll remind you what my original post said.


Keep in mind that dynos load an engine differently than they are loaded while running down the track. Not saying dynos aren't useful or don't show reality, just that there are some subtle differences between best numbers on the dyno and best numbers in a car going down the track. A couple components that I personally believe act differently on the dyno vs reality are headers, carb sizes, and rotating assembly weight.

Notice I said subtle differences.

You seemed to take offense to that post and called me out by stating I was incorrect. I merely stated multiple times that we would have to agree to disagree.

Dynos are a good tool and I never said otherwise, again my POINT is that there are subtle differences between dynos and actually running a car at the track. Not sure why you seem to take that post as some kind of attack against the "dyno industry" -- it is not.

Case in point. The fan idea is good -- you definately go further than most dyno operators. But airflow is dynamic at the track and I doubt you go through the trouble to synchronize a variable speed controller on a fan to match wind speed with a cars simulated MPH. Now you may think I am being completely anal here, but I am because my original point is that there are SUBTLE DIFFERENCES between the two and that is a prime example of a subtle difference.

I personally don't care about measuring g forces at the dyno or how one would try to simulate that. I'll continue to get my junk close at the dyno and fine tune at the track which is what I believe dynos are best used for.

[Eric68]

Don't worry, I have plenty of respect for you - if that's what this is about. Or is it a redux of the "sandbagging" post? sorta starting to sound like it to me :)


What the hell are you talking about? What sandbagging post?

[dieselgeek]

Eric - I am responding, in my posts, to more than just you. Check some of the other replies.


If you forgot the sandbagging post, that's good then!



The only question I still have (again) is your comment about peak power after a dyno session, did not make the car quicker. What kind of dyno did you run on?

-scott

[Eric68]

Oh yeah, sorry. Mustang dyno. Here is the guy's website (he's sharp by the way, and I would highly recommend Kaz to anyone in the GR area) http://www.ayaracing.com/

[dieselgeek]

Oh yeah, sorry. Mustang dyno.


that's interesting!

so, you found the best power AFR (and timing, presumably) but at the track, it went quicker with a change - what was the change? were there any other things that might have affected the outcome?

typically I deal only with EFI. Fuel system problems, generally, aren't an issue (sloshing fuel in float bowls, or whatever else you might run into). Did you ever come to a conclusion about what was different? I realize much of this is theory... but.. did anything else change? is this a case where g-forces might have affected the tune?

[Eric68]

Accelerator pump change was the first improvement. It wanted more pump shot out of the hole. Went up on squirter size from .042" to .045"

Leaning the jetting 2 sizes in front was the other that netted more MPH. Timing down from 34* to 33* total made a marginal improvement at the track (difficult to prove)

PS. Two years ago I went through the same thing with gasoline on the chassis dyno then track -- I missed the fact the car needed jet extensions on the chassis dyno and it bogged horribly at the track.

[Rickracer]

Obviously there are some subtle differences that cant be duplicated at the track, but in terms of getting a car dialed in, it seems to me that one can get a lot further along with a few hours on a dyno than in several trips to the track. 8)

[dieselgeek]

Obviously there are some subtle differences that cant be duplicated at the track, but in terms of getting a car dialed in, it seems to me that one can get a lot further along with a few hours on a dyno than in several trips to the track. 8)


I think you're right... in eric's last post he mentioned "pump shot" and THAT is a good example of something you can't do on a dyno, recently a customer of mine picked up ET by increasing the EFI-equivalent of "pump shot" on his car...

My main point in all this confusion is that a good chassis dyno lets you put the powertrain into, and hold, a given RPM/load as opposed to "passing through" that point in rapid transition, and that technique has helped everyone I know that's tried it, improve their ETs.

[Dynoroom]

And I'll add that if you had run on the dyno and made good power then had a problem at the track you would look at little details like pump shot or fuel bowl slosh or ??? instead of chasing other phantoms...

Oh, and as for ram air, if you are running efi that's what a MAP sensor is for. You can even use one to see "if" your building intake pressure with your hood scoop design and make changes accordingly on a carb system.

[JeffMcKC]

Dynos are just another tool in the box. The sad fact as I have seen over and over, is if a guy spent 1/2 the time on his chassis tuning as he did picking up 30 HP on the Dyno, his ET would be reduced by a lot more than the Dyno picked it up. If you pick up 30 Hp on your Dyno thats .015 on a 3500 lbs car. Take the same average car and tune the chassis and you will pick that up in a snap. Chassis dyno's are the new it thing, guys compare their dyno sheets like ET slips. I know guys who go to a different dyno just to get a bigger # without even touching the car.

Now I am not saying a Dyno does not have its place, because it does, I prefer engine Dynos, so I can get close on convertors first.

Its like Cams, 5 cams there may be 20 HP between them, but if you find 50 or 75 then you missed it by way more than you should have to start with, and you dont need a Dyno to tell you that.

[DanStokes]

I know squat about tuning, as I've started before. But I DO know dynos, both chassis and engine. Let me assure you that Scott's basic assertion is correct - there's a huge difference between an inertial dyno (older DynoJet, for example) and a dyno with a PAU. It's not that the inertial dynos are useless, just that they are very limited, and especially for full range tuning. All they really can do is measure the rate at which the subject car can accelerate a fixed inertia weight, which limits their use only to WOT operation. Is track tuning necessary? Of course. As others have said, there are small tweaks that can only be made when the vehicle is under motion and subject to the physics of a body in motion.

A note on engine dynos. Even a basic Superflow hydrokenetic (water brake) can provide extensive useful data. However, given a choice, I'd take a flux-vectored AC or DC dyno, which can provide a full range of simulation, including motoring of the engine (picture the car coasting down a hill). These later types of dynos are, unfortunately, very pricey. The down side of engine dynos is that they can't provide ANY info on the assembled vehicle - just the way it is. A chassis dyno can at least fill in a few of those blanks on your spread sheet.

The usefulness of either chassis or engine dynos is largely determined by the accompanying instrumentation. The more the better. AFR (Lambda) for each cylinder is doable. Data logging of temps all over the engine and cell is necessary. And when was the last time the equipment was calibrated? Lots of shops don't even own the equipment to calibrate their load cells. At the EPA lab, we spent about 1/4 of our time calibrating and documenting.

Folks who don't know dyno testing often do go shopping for the highest number, which is, of course, just plain silly. That's like me saying I have a bigger 9/16 wrench than you have. The point is not the size of the tool, but what you can do with the resultant effort. (That wasn't meant to sound sexy, but it kinda does.....)

For more info, see my dyno article on the September 2000 issue of Hot Rod.

Later
Dan