Don Terrill’s Speed-Talk

vortecpro wrote:Theres two answers on here I like a lot . Same exact curve except one is 900 RPM higher.

Same curve but more rpm, in this theoretical world the higher rpm engine wins - all else being equal shift recovery will be stronger with more rpm.

cjperformance wrote:

vortecpro wrote:Theres two answers on here I like a lot . Same exact curve except one is 900 RPM higher.

Same curve but more rpm, in this theoretical world the higher rpm engine wins - all else being equal shift recovery will be stronger with more rpm.

But is the torque curve the same? The 6200 rpm motor is making more torque than the 7100 rpm motor at lower rpms. If the 7100 rpm motor had the same torque it should be making more horsepower at 7100

Most Chevelles I've seen r heavy so the lower rpm motor with more tq down low wins. I run a 3690lb car so the more tq down low the better.

cjperformance wrote:

vortecpro wrote:Theres two answers on here I like a lot . Same exact curve except one is 900 RPM higher.

Same curve but more rpm, in this theoretical world the higher rpm engine wins - all else being equal shift recovery will be stronger with more rpm.

If the curves are the same ( e.g assume this means perfectly linear) and gearing optimised for each then it will be the same.

digger wrote:

cjperformance wrote:

vortecpro wrote:Theres two answers on here I like a lot . Same exact curve except one is 900 RPM higher.

Same curve but more rpm, in this theoretical world the higher rpm engine wins - all else being equal shift recovery will be stronger with more rpm.

If the curves are the same ( e.g assume this means perfectly linear) and gearing optimised for each then it will be the same.

That has to be the starting point for any sensible answer. There's a reason why those calculators that back out stuff from the trap speed mph number back out hp. They don't back out the rpm, or torque! But then let's also recognize that there may be some subtle practical issues beyond that starting point that make the question interesting, beyond determining who paid attention and who slept during the high school physics class.

Looks like there's going to be two factors (at least) in play here:

Rate of acceleration.

Stored momentum.

vortecpro wrote:I'am going to ask the same question I asked on the Chevelle forum.


"Which engine is faster down a dragstrip and why"




A 427 that makes 600 HP @ 6200 RPM
A 427 that makes 600 HP @ 7100 RPM

?

The one that gets to the finish line first..Why? Better combo and Because they get the win light.

How about a 73 Camero steel body a frame (certified) built into the bottom (kinda heavy). 427 SBC turns low 9s . 3.70 gears, 30" slicks. Shift point around 5800.

To me, in drag racing 'quicker' means E.T; 'faster' is MPH, so as per a couple of previous posts and dozens of well-proven calculators, all else equal the speeds will be the same.

turbo2256b wrote:How about a 73 Camero steel body a frame (certified) built into the bottom (kinda heavy). 427 SBC turns low 9s . 3.70 gears, 30" slicks. Shift point around 5800.

My question would be how does one compare that to a 3000 stock suspension Nova with a 306 and a 300 shot of nitrous running 6.15 at 114 in the eighth...roughly a 9.30 quarter maybe quicker due to it's desire for RPM.

MadBill wrote:To me, in drag racing 'quicker' means E.T; 'faster' is MPH, so as per a couple of previous posts and dozens of well-proven calculators, all else equal the speeds will be the same.

Assuming vortecpro allows our theoretical racer to run gears and convertor to match each engine i still say the higher rpm engine wins. Even with a theoretical MPH limit based simply off of HP ,, a Harder higher rpm hit on the convertor and lower gears will achieve said MPH limit earlier and then potentially carry this MPH for more distance down the track, more track covered at a higher MPH is a quicker ET.

According to quarter pro, the higher rpm engine would be a little quicker i increased shift point and converter stall and launch rpm all by the same 900 to try to duplicate the power curve that the car would see going down the track, and move gear ratio so finish line rpm was just over peak on both. i'm curious as to why its quicker you would think with everything spinning faster it would see more friction loss but i could be wrong or have the way that works backwards.

one thing I learned with the turbo small block 20 years ago when everyone was telling me to not put as much gear as a centrifugal, was everyone was wrong. even with a ton of tq you cant outrun a lack of gear. I would take higher rpm even with less tq because I can put more gear in it, and gear makes up for a lot of sins.

Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us





JOE SHERMAN RACING

AMXstocker1 wrote:According to quarter pro, the higher rpm engine would be a little quicker i increased shift point and converter stall and launch rpm all by the same 900 to try to duplicate the power curve that the car would see going down the track, and move gear ratio so finish line rpm was just over peak on both. i'm curious as to why its quicker you would think with everything spinning faster it would see more friction loss but i could be wrong or have the way that works backwards.

Im not familiear with the program BUT, it should be showing that you are reaching a higher MPH earlier on the track when adjusted for the higher rom engine, there is your faster car right ther, average mph across the track is higher, quicket et.
There is more than just friction here with the higher rpm. The way the convertor works, the way the lower rear gear works and the way the engine recovers on shift are all factors that allow slightly faster acelleration up to peak mph.