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

General engine tech -- Drag Racing to Circle Track

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gvx
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Re: Which Is Faster

Post by gvx » Tue Sep 19, 2017 4:16 am

Engine power is measured in torque. Horsepower is the sum of a mathmatical calculation. RPM is the WILDCARD above 5252 RPM. SO like Ms Vitto says this is a trick question, there is no correct answer without more information. Anyone who has an answer is making assumptions by inserting superimposed data from there real life experiences
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Re: Which Is Faster

Post by digger » Tue Sep 19, 2017 6:14 am

gvx wrote:Engine power is measured in torque. Horsepower is the sum of a mathmatical calculation. RPM is the WILDCARD above 5252 RPM.
this is completely wrong

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Re: Which Is Faster

Post by joe 90 » Tue Sep 19, 2017 6:32 am

Just what I was thinking too.

If you just ignore torque and RPM and think that the rate of burning fuel relates to HP, then given the correct gearing for each, they're equal.
There's a few variables left out which might make a difference either way.

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Re: Which Is Faster

Post by novadude » Tue Sep 19, 2017 6:57 am

Isn't the answer simply "The engine and converter / gear combo that makes the highest average RWHP over the length of the 1/4 mile wins the race"?

If you have an engine that has a flat HP curve past peak hp, and your converter / gear combo keeps the engine right at that peak / flat curve for the length of the track, I would guess you'd probably be faster than the guy with the same peak hp and a curve that drops off fast past peak.

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Re: Which Is Faster

Post by dualquad » Tue Sep 19, 2017 7:17 am

I would bet on the car with the highest skilled tuner.

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Re: Which Is Faster

Post by vortecpro » Tue Sep 19, 2017 7:56 am

MTENGINES wrote:
GARY C wrote:So a 357 making 530 horse at 7700 out runs a 331 making 529 horse at 6500 regardless of combo or the fact that the 331 makes 81 more ft lbs?
We usually don't race at peak torque. Most drag racing engines I do, the stall ends up being around 500rpm less than peak horsepower rpm of they are NA. Who cares about torque. An engine that loses torque the slowest usually wins.. because it will rpm.

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I never race @ peak TQ......ever
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Re: Which Is Faster

Post by vortecpro » Tue Sep 19, 2017 8:10 am

bigjoe1 wrote:Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us





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RPM is wheel speed. The higher the RPM at launch, the faster things happen. But at the same time power carry has to be considered when designing an engine.
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Re: Which Is Faster

Post by vortecpro » Tue Sep 19, 2017 8:17 am

cgarb wrote:Playing the devils advocate here...how is it that there are fast diesel powered trucks then? Does rpm have that much to do with it?
Glad you asked. My example was NA, theres not a diesel in the world as far as know that could do anything without a turbo. In drag racing 4500 RPM will not make any kind of racing TQ converter work without a power adder, the power adder makes the low RPM combo work as always. NA drag racing is about RPM and TQ multiplication and power carry.
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Re: Which Is Faster

Post by vortecpro » Tue Sep 19, 2017 8:19 am

vortecpro wrote:
cgarb wrote:Playing the devils advocate here...how is it that there are fast diesel powered trucks then? Does rpm have that much to do with it?
Glad you asked. My example was NA, theres not a diesel in the world as far as know that could do anything without a turbo. In drag racing 4500 RPM will not make any kind of racing TQ converter work without a power adder, the power adder makes the low RPM combo work as always. NA drag racing is about RPM and TQ multiplication and power carry.
NA drag racing is always about moving the power up, more gear-more multiplication
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Re: Which Is Faster

Post by The Radius Kid » Tue Sep 19, 2017 9:13 am

GARY C wrote:
The Radius Kid wrote:
GARY C wrote:So would an engine with a better tq curve not take advantage of the fly wheel effect?
I would think so,but it would depend on where the shift occurs.
IIRC,most guys shift near peak torque as a general rule.
Forgive me I don't know what IIRC means but I thought you normally shift about 700 rpm past peak horse power?
I believe you are correct.I thought about it later and .. oops!
I don't know about 700 past,but staying above the peak torque point is what I was thinking.
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Re: Which Is Faster

Post by turdwilly » Tue Sep 19, 2017 9:46 am

cgarb wrote:Playing the devils advocate here...how is it that there are fast diesel powered trucks then? Does rpm have that much to do with it?
Big difference in pulling a heavy load & accelerating a light car.

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Re: Which Is Faster

Post by Abbottracingheads » Tue Sep 19, 2017 9:50 am

RPM wins evertime. Perfect example--- This weekend in Dallas in Top Sportsman our Pro Stock truck with a 565 NA engine outran several 665,632, and even a 704 ci engines with probably comparable power, but we were turning 8800 and they were turning 7000-7500 rpms. RPM increases power pulses to the tires and is always faster.
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Re: Which Is Faster

Post by Daniel Jones » Tue Sep 19, 2017 12:12 pm

> Does rpm have that much to do with it?

The physics is straightforward and easy to derive. Torque is the rotary equivalent of force and is what accelerates a vehicle but it's the torque at the rear wheels that accelerates the vehicle, not the torque at the crankshaft. Horsepower (at the crankshaft) is the measure of how much RPM can be traded for rear wheel torque via gearing. Assuming you have sufficient traction, it's the average of power between shift points (including the down time for the shift) that is important, not a single peak power point. Also, it's the overall gearing provided by the transmission, rear end, and tire diameter that is important. Furthermore, it's the total inertia of the vehicle that has to be accelerated. That includes not just the weight (mass) of the vehicle but also the inertia of all the rotational bits (flywheel, crankshaft, driveshaft, axles, wheels, tires, etc.).

> RPM is the WILDCARD above 5252 RPM.

The 5252 RPM cross-over (of the torque and HP curves) has no significance whatsoever. It's just an artifact of the units chosen. Change the units to newton-meters and the cross-over point changes to a different RPM.

> Big difference in pulling a heavy load & accelerating a light car.

The physics are the same. A truck with 1100 ft-lbs of torque but only 200 HP average between shifts will be beaten by one with 300 HP average and 300 ft-lbs of torque (regardless of load) if both are geared optimally for their respective power curves.

> RPM wins every time.

There's an optimum RPM range for a given power curve. Operate above (or below) that range and you'll slow down (assumes no traction issues and optimal gearing).

> IIRC,most guys shift near peak torque as a general rule.

For maximum acceleration, you generally shift beyond the peak HP RPM. The idea is to maximize the area under the HP curve, including the down time for the shift.

Dan Jones

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Re: Which Is Faster

Post by cgarb » Tue Sep 19, 2017 1:37 pm

That somewhat makes sense to me, but by that logic, the more you rpm a car the faster it should go. My car I shift at 6800, I had also tried shifting at 7500 and it ran almost the exact same slip. One hundreth faster, but that could have been a weather change. Why would more RPM not net me a gain in that instance then?

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Re: Which Is Faster

Post by 77cruiser » Tue Sep 19, 2017 1:58 pm

cgarb wrote:That somewhat makes sense to me, but by that logic, the more you rpm a car the faster it should go. My car I shift at 6800, I had also tried shifting at 7500 and it ran almost the exact same slip. One hundreth faster, but that could have been a weather change. Why would more RPM not net me a gain in that instance then?
Where does it make peak HP at?
Jim

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