Mythbusters - engine & dyno edition

[Caveman Tony]

so Jeff, lemme ask this:

What is the lower rpm range for low gear on one of your runs?

And I wonder what the dyno would say is better for THAT lower rpm at that timing setting vs. that same rpm at #max# timing....

[JeffMcKC]

The motor does not see under 6500 stall, and 33* timing, we have not played with the retard on this one, but I had it in 07 on the 18* engine. I geuss someone on drag week thought the button on the shifter in high gear turned on the spray for the N/A class when it took 2* out in high. and also in high going down the road it took 4* out. Using a Holley Ign system

[TC]

It gets a bit confusing.

I talked to scot on the phone I think he understands what we do better now.

If the best tune came off the dyno at 38* then we "IF IT LIKES IT" put 40* in on the line for low gear, and my even pull back the 2* to 38* in the upper rpm range of low gear. Then run 38* the rest of the way. Then to throw a wrench in that a lot of cars require a different timing and jet at the track than the dyno. Its all relitive to what makes the best run.

ET is chassis and MPH is power. Spinning a tire will and 1 to 2 mph to a car also. I dont want to confuse it more so I will stop at that LOL

The term for me of pulling 2* comes from not many ign systems will let you add timing. So you put it at 40* and then pull2* so it may sound odd to someone not in the loop for the term, I did not invent it, but learned it from the "Da Grump" in 1978 we where cutting out one set of points in my car to change the dwell ( which changes timing ) from some research on Grumps stuff.

How much does 2 degree of timing equate to in HP output?? Meaning what HP figure are you making at 40 degrees compared to 38 degrees??

[Deaf Bob]

Thanks Jeff..
Makes sense now..

[JeffMcKC]

How much does 2 degree of timing equate to in HP output?? Meaning what HP figure are you making at 40 degrees compared to 38 degrees??

Its not about HP, its about getting down the track the quickest. The first part of the track is the slowest, N/A the race is over at 330'

[A/Fuel]

Its not about HP, its about getting down the track the quickest. The first part of the track is the slowest, N/A the race is over at 330'

This is an intresting subject.
I know most people will disagree, but an a/fuel car runs just like an n/a car. If it's not getting it before the 330' it's probably not going to go anywhere. Max power on one of these cars now a days is around 70*, but you have to leave around 50* so it gets down the track and ramp it in as fast as the car can handle. We used to take out a few degrees at the end, not to mph more, but just so the thing will live and not tear itself up. Parts and and the way things are done have been getting better lately and there seems to be a whole lot of cars running 270+ mph, thats because the timing isn't being pulled anymore and cars are crossing the line with 70* and maybe more.....and staying in one piece.

[JeffMcKC]

If its running over itself, & tearing up, it has to lose power/MPH

[A/Fuel]

If its running over itself, & tearing up, it has to lose power/MPH

It sure does!
A car I was working on a few years ago used to toss the balancer right around the 1000' or about 4.5 seconds in almost everytime.
It would take the crank triggers off with it, along with the starter dog. Sometimes the crank bolt would be gone too, other times half of it would be stuck in the crank. The only way we knew how to fix it was to take some timing out at 4.2 seconds. Come to find out we wern't the only ones having this issue. After spending some time discussing this with a friend he devoloped a new washer and bolt for the crank. The secret was the rockwell in the washer so the bolt could go to 450ftlbs. Once we had the confidence to keep the timing in, the car picked up over a .1 and almost 5mph. it went from 5.50's at 250 to 5.40's at 255.

[TC]

This is an intresting subject.
I know most people will disagree, but an a/fuel car runs just like an n/a car. If it's not getting it before the 330' it's probably not going to go anywhere. Max power on one of these cars now a days is around 70*, but you have to leave around 50* so it gets down the track and ramp it in as fast as the car can handle. We used to take out a few degrees at the end, not to mph more, but just so the thing will live and not tear itself up. Parts and and the way things are done have been getting better lately and there seems to be a whole lot of cars running 270+ mph, thats because the timing isn't being pulled anymore and cars are crossing the line with 70* and maybe more.....and staying in one piece.

You guys are running 70* of advance??....... I thought when I talked about running that much you guys thought I was nuts..........

[TheSilverBuick]

You guys are running 70* of advance??....... I thought when I talked about running that much you guys thought I was nuts..........

Were you talking about a nitro car or one of your cars?

[dieselgeek]

If 70 is good, then 80's gotta be better! turn it up Alex!

[TC]

Were you talking about a nitro car or one of your cars?

I was talking about a guy I talked to at one of the last Cruise's on Central that ran a blown Alcohol truck, he said the nostalgia guys told him to run 70* of advance he said they were crazy but he did bump it up to 50* and he said it made the motor rpm a lot faster and they went quicker in the quarter........ I wouldn't recommend it on a gas motor, but apparently on a Alcohol motor the increase in timing was worth some power.........

[A/Fuel]

I know some people that run blown alcohol engines and never heard of anyone running anywhere near 70*

[TC]

This is the Truck I'm talking about....... He said the other guys he races with are running as much as 70* of advance, like I said he thought they were crazy, but he did say he turned it up to 50* and ran a faster time.......

[TC]

Also total timing is going to be different for every motor for the simple fact that all motors are built differently, so saying what works for one motor is going to work for the next is just, well, not the way it works....... Your max timing should be set where peak cylinder pressure is produced, anymore or any less than that number will cost you power..........

Over the weekend I talked with my friend Larry about one of his buddies cars that was at the car show.....The car is a 70's Nova that is tubbed and runs 11.0's with a small block..........The owner decided to have the car "dyno tuned" to see how much HP it was making, they did some tuning and were able to get about 20hp more out of his combo with adjusting the timing and fuel mixtures, he took the car back to the track and the car ran SLOWER!!!!...... They switch the timing and jetting back to were they had it and the car started running it's normal times again....... I guess there's a reason NHRA doesn't race dyno's.............

Fact is all the speculation and dyno time in the world, doesn't mean squat when the car hits the track........