SBC Dyno results, where to go from here

[rustbucket79]

Stan, would you clarify what your math is saying?

[rustbucket79]

You need to be looking at your drive line instead of the engine. How come no one does this?
133 MPH @ 3250=589 HP

Not mentioned yet is I am showing the best pull of a combo that is corrected. Track can see 3500’ days, and even within these tests we are talking 25, maybe 30 corrected up over what the engine made with my carb/header/full exhaust/etc

[Stan Weiss]

Stan, would you clarify what your math is saying?

Based on calculations using the 4 column as A/F ratio I do not come up with some of the other data shown on the dyno sheet. If I use that other data on the dyno sheets I can get everything to come out the same but A/F ratio. Using the other fields I get 13.14:1 as the A/F ratio for the first line on the dyno sheet.

Stan

[6.50camaro]

I come up with around 12.7% converter slippage for 7200 rpm @ 134 mph with tire and gears listed. More gear will pick up converter efficiency with out raising rpm much.Dan

[vortecpro]

You need to be looking at your drive line instead of the engine. How come no one does this?
133 MPH @ 3250=589 HP

Not mentioned yet is I am showing the best pull of a combo that is corrected. Track can see 3500’ days, and even within these tests we are talking 25, maybe 30 corrected up over what the engine made with my carb/header/full exhaust/etc

I understand what you are saying.......but heres the problem, which comes back to the car setup 1320/133=9.92

[rustbucket79]

Stan, would you clarify what your math is saying?

Based on calculations using the 4 column as A/F ratio I do not come up with some of the other data shown on the dyno sheet. If I use that other data on the dyno sheets I can get everything to come out the same but A/F ratio. Using the other fields I get 13.14:1 as the A/F ratio for the first line on the dyno sheet.

Stan

Then this will explain your discrepancies. Our O2 sensors are a few years old and are due for replacement due to lead contamination. The other O2 reads a solid 1 to 1.5 numbers leaner, and swapping the leads side to side swaps the readings too. Some of the pulls showed as lean as 13.6 on the other channel at certain points.

[rustbucket79]

Not mentioned yet is I am showing the best pull of a combo that is corrected. Track can see 3500’ days, and even within these tests we are talking 25, maybe 30 corrected up over what the engine made with my carb/header/full exhaust/etc

I understand what you are saying.......but heres the problem, which comes back to the car setup 1320/133=9.92

Without a doubt the car is undergeared. When I originally built this engine I had 4.56's in the car but magnafluxing the gears showed cracks in the crown. I had a set of used 4.10's so that's what went in. I had planned to step up to 4.30's long before the dyno opportunity presented itself, but ultimately I'm gambling by staying with the 10 bolt diff, so an upgrade is happening in that department before the car hits the track again. Somewhere around 4.56's is what I'll use, it may well be faster with more, however I don't have national event track prep at my home track, so traction is of concern.

[rustbucket79]

I come up with around 12.7% converter slippage for 7200 rpm @ 134 mph with tire and gears listed. More gear will pick up converter efficiency with out raising rpm much.Dan

You are correct, the variable is how much. I can tell you that my converter with 4.56's and a lower HP engine gave me around 5% slippage

[rustbucket79]

I just recently had a customer dyno a 13-1 421 with a 227cc head. I would post up the sheet if you would like to see it as long as folks don't think it's some sinister plot. lol

Feel free to do so.

[rustbucket79]

Prior to the dyno, I had no clue just how well the power would hold on above 7000. I should probably pull it higher to see what happens at say 7800.

[6.50camaro]

I come up with around 12.7% converter slippage for 7200 rpm @ 134 mph with tire and gears listed. More gear will pick up converter efficiency with out raising rpm much.Dan

You are correct, the variable is how much. I can tell you that my converter with 4.56's and a lower HP engine gave me around 5% slippage

This past year I went from 4.56 to 5.13 gears , converter slippage went from over 19% to 11% this is for the 1/8th . Rpm went up 100 rpm at the stripe from 6600 to 6700. I don't know if I can go 5.38's and still stay below my self imposed limit of 7000. Dan

[statsystems]

I come up with around 12.7% converter slippage for 7200 rpm @ 134 mph with tire and gears listed. More gear will pick up converter efficiency with out raising rpm much.Dan

You are correct, the variable is how much. I can tell you that my converter with 4.56's and a lower HP engine gave me around 5% slippage

This past year I went from 4.56 to 5.13 gears , converter slippage went from over 19% to 11% this is for the 1/8th . Rpm went up 100 rpm at the stripe from 6600 to 6700. I don't know if I can go 5.38's and still stay below my self imposed limit of 7000. Dan

Seen this many, many times. Most,guys don't run near enough gear. Had a customer go from 4:30 to 5:13 with the same results you found. He really needed 5:38's but all the fence leaning bleacher preachers told him he was crazy and pretty much called him a liar.

[rustbucket79]

I wouldn't think .25 of a point would represent 300 RPM, but let me ask you this. Would the world end if you shifted at 7000 and crossed at say 7050 RPM?

[randy331]

You'd be surprised how deep of gear and how much converter you'll end up with if you chase ET only.

Most won't treat their engine the way it takes to produce lowest ET.

Randy

[6.50camaro]

I wouldn't think .25 of a point would represent 300 RPM, but let me ask you this. Would the world end if you shifted at 7000 and crossed at say 7050 RPM?

No I don't think it would. I have 4.56, 4.88, 5.13 gears on hand . I would have to buy the 5.38's . I was really looking to pick up converter efficiency to cut down on unnecessary heat in the trans fluid. I picked up a little mph .5 or so as an added bonus . If the 5.38's got the slippage down to 7-8% I'd be really happy with that. The thing is right now because the way the car is safety equipment wise I'm limited to no quicker than 6.50 in the 1/8th . The car went 6.43 first run off the trailer with this new combination. A couple changes to slow it down it went 6.31. Best the car did on the old motor was 6.96. Trying to be happy going 6.50 till I can upgrade the safety stuff. Then I won't need the 5.38's. Dan