Why round exhaust pipe?

[JeffMcKC]

Then just say you want the closest amount of back pressure to zero as possible....... Also I was under the impression that when using headers that a vacuum was being pulled in the header tube assisting in drawing the new intake charge into the cylinder during overlap, but how can this happen if there is back pressure in the header tube like you are saying??......... Vacuum, Pressure, you can't have both, or can you??...........

There is no such thing as vacuum, as the air goes out one tube it can lower the pressure in another tube, think pan evac on headers. This is why guy that buy firing order swaps without fixing their headers dont gain much just like those mag swaps you love, just swapping without optimizing does not get you far and makes everyone look good. Just like the carb swap one they are talking about right now.

[Bob Holmes]

Thanks.... I'll be around but I dont like getting into the pissin
matches that occurs on many boards

I certainly understand.

I don't spend my time arguing with folks. I don't find it fun. I know what I know, I know what I don't and I find that trying to help folks that don't want it is a waste of my time.

I hope we have the opportunity to learn something from 30 years of experience at that level.

[mike343sharpstick]

In the early 2000's the factory Honda 600 super stock race bikes had 4 into 1 exhaust systems with a square collector. After the collector it transitioned back to round tube. That obviously worked better at some point in the power band, Honda factory race hardware is serious stuff. The theory was that it reduced turbulence when the pulses came out of the individual tubes into the collector.
That said, it was a short lived design.

[SuperBuickGuy]

In the early 2000's the factory Honda 600 super stock race bikes had 4 into 1 exhaust systems with a square collector. After the collector it transitioned back to round tube. That obviously worked better at some point in the power band, Honda factory race hardware is serious stuff. The theory was that it reduced turbulence when the pulses came out of the individual tubes into the collector.
That said, it was a short lived design.

exhaust surge tank? lol hopefully it was shaped like a pipe bomb

and Randal, sorry, was too busy doing other stuff to actually get to checking flows.... tomorrow night, maybe.

[dieselgeek]

Thanks.... I'll be around but I dont like getting into the pissin
matches that occurs on many boards

More!! please share! OEM-level testing is as good as it gets!

[CDMBill]

As long as we're at this, does anyone know if merge collectors work as well in in full exhuast systems as they do in open exhuasts, and in header/merge/x-pipe congfurations.

[JeffMcKC]

well they seem to on Cup Cars........

I have a set of the Cup Take off Tri Y's for the next set up, very trick stuff going on with those exhausts

[MR P-BODY]

As long as we're at this, does anyone know if merge collectors work as well in in full exhuast systems as they do in open exhuasts, and in header/merge/x-pipe congfurations.

The merge length needs to be calculated into the length of the full exhaust and where
the muffler is located, so to just throw one on.... no it wouldnt help at all

[mike343sharpstick]

If I ever hit the big time, I’m going to buy a couple motors, a dyno cell, and pile of tubes, and not talk to anyone for months.
I'd love to see your findings on the tri-Y design!

[MR P-BODY]

Before I retired I did alot of work on headers on the dyno at Chrysler
using the Pipe Max program... also looking at the Pro Stock cars and
the headers they run... most over the counter headers are too long on
the primaries and too short on the collector... I still build all my own
headers.. mainly due to what I run and nothing is made for them

[JeffMcKC]

Using Pipe Max I would like to think ist somewhat dynamic, Larry says its based off a Pipe Organ tuning program to start with and seems to get very close right off the bat.

[TC]

Using Pipe Max I would like to think ist somewhat dynamic, Larry says its based off a Pipe Organ tuning program to start with and seems to get very close right off the bat.

They state on their website that it is 90% accurate.......... IMO that is leaving a lot on the table........ Though I might shit can the $45 to check it out........

[JeffMcKC]

Well as with everything TC if you give up some of your "Ideas". Larry cannot give a magic number and he is as Honest as they come. He did not build your engine to control everything with it with engines like yours that are peiced together with someones own magic brew . As soon as some one says its 100% they have lied. I will take Larry's Real World 90% any day and tune from there.

[MR P-BODY]

They state on their website that it is 90% accurate.......... IMO that is leaving a lot on the table........ Though I might shit can the $45 to check it out........

I have moved lengths and diameters to see if I could make it better
than what the program comes up with and on a couple of occasions
I did get a couple of HP... but nothing to right home about and I couldnt
verify that it wasnt the dyno conditions.... so after all the added work I
tend to just use the program numbers and try to keep the lengths as
close as possible .... lets face it... if you cant get them in the car they
are useless so you MIGHT have to sacrifice a little here and there

[Bob Holmes]

Larry's Pipemax is a hell of a deal at $45. He gets you close to the mark, then you need to test from there.

There are no silver bullets, unless you are going to pay big bucks for someone else to science it out, build it and test it.