Which Is Faster - 600hp@6200 or 600hp@7100

[user-17438]

Back to which is faster, unless you are severely limited by gearing options, as in DV's example, rpm wins EVERY TIME!
Before the gear rule, we would sometimes sacrifice power to be able to turn more rpm.

Yes sir, I had that very thing happen during testing at Daytona with my first ever restrictor plate build. Engine made good horsepower and torque.. it was a turd. Found out we had less gear than everyone else. it slowed down with more gear. Came back with a new intake manifold, headers, cam and less power but more rpm. we geared it more and it actually qualified. of course we were'nt in the front of the pack. but it showed us rpm was king.

Similar situation i built and sb2 for a customers drag car. it made 40 more horsepower and 100 less ft/lbs of torque than his original engine. with more gearing the car went .40 faster in 1/4 and gained 2mph. explain that.. the engine with way less torque beat the old combo.

torque is an excuse for not enough horsepower

[digger]

In answer to the question,
If we convert the motor that spins at 7,100 back to 6,200 you get a torque number of 689 Nm for both motors. If you convert the 6,200 torque number to 7,100 you get both motors generating a torque number of 601 Nm. So no surprise there.
The speed down the drag strip is all about the amount of torque being applied to the wheels at a given speed. So based on my calc's that amount of torque will be exactly the same. As mentioned before there maybe some gains in the lower friction number but that's the limit of the difference.
Tony


PS
Hi DV I am the guy you meet in Sydney with the new intake design.

This is still the right answers as the curves normalise out if stay within the bounds of the question , but in reality you care about how far you can go beyond peak hp rpm how long the power hangs on for as you don't develop gearing on peak hp rpm or shift at peak hp and you are trying to maximise area under the curves but this stuff is not posed in the original question and why people have seen different results either way due to the specifics of their application.

[Desertrunner]

I have a question Tony:


Would you run a engine that the peak HP occurs @ 5800 RPM, and turn it 7000 RPM through the lights in a drag race situation?

I think its a really good question, as we are talking about drag engine I would rather the 7,000 rpm. When I was at DV course the other week the question was asked about fly wheels, does a large one give you better times. I think the answer to your question is similar.
So you are sitting at the start waiting for the lights to change and you have the engine reving to 7,000 rpm or 5,800 rpm. Logic would tell you that any energy you have used to get the engine to 7,000 rpm (it would take more energy to get the engine to 7k then 5.8k) before the green light is free power. To explain to move a drag car down a strip in a given time requires a given amount of energy. If you have stored some energy before the light went green then the equation or calc is
Energy created before the green light plus energy created in the time between the two point on the drag strip.

Think of one of the kids toy cars were you run the toy on the ground till the wheels spin up then you put it down, it shoots off with out any more added power because it is using what was created before the lights turned green?

[RDY4WAR]

I just ran both engines through a simulation based on an excel spreadsheet calculation. Figuring a 1.76 glide trans, 30" tires, rear gear adjusted so the car crosses the 1/4 mile at peak hp (6200 and 7100 rpm respectively), and same drag coefficient, same weight, etc... with identical horsepower curves with the torque peak at a good spread of 1200 rpm below peak hp which is also the launch rpm. Both shifting at the rpm that provides the best average acceleration gear to gear.

600 hp @ 6200 rpm w/ 3.55 gear = 9.941 @ 136.4 mph
600 hp @ 7100 rpm w/ 4.04 gear = 9.941 @ 136.4 mph

Same horsepower, same ET, same mph.

[digger]

I have a question Tony:


Would you run a engine that the peak HP occurs @ 5800 RPM, and turn it 7000 RPM through the lights in a drag race situation?

if the hp falls off a cliff after the peak hp rpm then you probably wouldnt rev it that high unless you wanted to go slower, sometimes you rev the engine a bit higher than ideal if you want to avoid a gear change at the wrong "time"

[vortecpro]

I just ran both engines through a simulation based on an excel spreadsheet calculation. Figuring a 1.76 glide trans, 30" tires, rear gear adjusted so the car crosses the 1/4 mile at peak hp (6200 and 7100 rpm respectively), and same drag coefficient, same weight, etc... with identical horsepower curves with the torque peak at a good spread of 1200 rpm below peak hp which is also the launch rpm. Both shifting at the rpm that provides the best average acceleration gear to gear.

600 hp @ 6200 rpm w/ 3.55 gear = 9.941 @ 136.4 mph
600 hp @ 7100 rpm w/ 4.04 gear = 9.941 @ 136.4 mph

Same horsepower, same ET, same mph.

Theres a big problem here, 9.94 is way high for 136 MPH, you are not utilizing the power, more RPM allows better utilization of power. And you are always looking to show dyno HP, this is when you know you have it right.

[vortecpro]

I have a question Tony:


Would you run a engine that the peak HP occurs @ 5800 RPM, and turn it 7000 RPM through the lights in a drag race situation?

if the hp falls off a cliff after the peak hp rpm then you probably wouldnt rev it that high unless you wanted to go slower, sometimes you rev the engine a bit higher than ideal if you want to avoid a gear change at the wrong "time"

I have a peanut port Chevelle 3720 pounds, 454 9.3 comp 228 @ .050 hyd cam, dual plane. HP peak was @ 5800 RPM, But I run it 7000 RPM through the lights, it shows dyno HP given the conditions, which means the combination is very close to optimized.

60 1.30
1320 10.34-10.36 @ 126.07
1450 DA

[cjperformance]

I have a peanut port Chevelle 3720 pounds, 454 9.3 comp 228 @ .050 hyd cam, dual plane. HP peak was @ 5800 RPM, But I run it 7000 RPM through the lights, it shows dyno HP given the conditions, which means the combination is very close to optimized.

60 1.30
1320 10.34-10.36 @ 126.07
1450 DA

And in this instance did you run this engine on the dyno up to or at least near 7000 and observe what hp its making there?

[vortecpro]

I ran it only to 6400 thinking that would do it, I was wrong, power was down 13 HP @ 6400 RPM.

[cjperformance]

I ran it only to 6400 thinking that would do it, I was wrong, power was down 13 HP @ 6400 RPM.

So this is a good one for the camp saying it will run the same or faster using less rpm. Have a look at a dyno graph, TQ peaks then drops off then HP peaks then drops off. So why do us drag racers rpm past peak HP where the graph shows LESS TQ then shift or cross the stripe when we could shift say at peak HP, rpm will drop on shift to a point where prehaps HP is the same as where we shift past peak but TQ is higher!

[vortecpro]

Because we make it up on the bottom side of the track.

[KnightEngines]

For drag racing ignore TQ & where peak TQ occurs - it's irrelevant.
Shift at the point where HP before the shift = HP after the shift.
That point will be a little different for each shift - which is why you *usually* shift a couple hundred rpm sooner on the 1-2 shift than you do on the 2-3 shift with a 3 speed.

If both motors (as an example) are making, say 560hp on the way down after peak & both make 560hp on the way up below peak after the shift then the rpm that that occurs at is irrelevant, they will run the same.

[cjperformance]

For drag racing ignore TQ & where peak TQ occurs - it's irrelevant.
Shift at the point where HP before the shift = HP after the shift.
That point will be a little different for each shift - which is why you *usually* shift a couple hundred rpm sooner on the 1-2 shift than you do on the 2-3 shift with a 3 speed.

If both motors (as an example) are making, say 560hp on the way down after peak & both make 560hp on the way up below peak after the shift then the rpm that that occurs at is irrelevant, they will run the same.

Yes mate, this is what im getting at, if TQ was the be all in the drag race scenario we'd be shifting to run in the rpm range where we would achieve the highest average TQ, but really we want the highest balance of HP v RPM. This means a different shift point for each engine combo even with the same ratio change between gears dependent on how quickly the hp curve drops off after peak hp.
For an engine that drops quickly over say 500 rpm after peak hp we would not rpm as far past peak as an engine that hangs on well for 900 rpm past peak hp.
If peak hp was for eg 600 @ 6000 and either side was 570 at 5500 and also at 6500 (just example numbers) i would rather be applying 570hp @6500 than 570hp@5500

[Warp Speed]

Nobody has yet said how they'd build the 2 engines to make the quoted numbers .

As I said a few pages back, the one that makes the power at lower revs has boost.

The one that makes the same power at higher revs has a hot cam.


Boost always wins.

That is incorrect.

Going to extremes, say you have a boosted combo that makes a peak of 800whp at 7000, and a NA combo that makes a peak of 800whp at 9000. That higher rpm combo is gonna spank it, both having optimized gearing.

[user-23911]

It's a bullshit question because if you were clever you'd have a hot cam AND boost.


But anyway??????



How would you propose to build an engine to make the said numbers.

No, it's not using a simulator programme, they're BS too.