TheDonEffect

Let me preface by saying this is not an ap1 vs. ap2 debate or anything along those lines. I want to keep this as objective as possible.
My question is this: is having a higher redline necessarily better? or can gearing wipe out any inherent advantages of the higher redline? My question is specific to just that, I do understand that F1 for example use higher rpms to juice out as much ponies out of smaller engines as possible in an effort to keep weight down, but my question is more if these same f1 folk could achieve their same power goals from teh same engine while keeping the revs down and gear it accordingly, is there a downside?
My take on it is that there is no real benefit besides the idea that you could get more out of a smaller engine, but otherwise there is no benefit. I do understand (and subscribe to) that it is more exciting and fun(which is subjective) but not necessarily effective and really forces the engine to operate within strict tolerances leaving less room for error.
I guess you could compare something like a BMW v10 out of the m5 to the small block v8 out of the corvettes for instance, or f1 engines to audi's formula tdi.
I hope that you engineering folks could shed some light on this, just something I ponder during my long drives.

Penforhire

I see a benefit to avoiding shifts in some racing circumstances. Shifts, time not on the throttle plus drop in powerband when you pick it up again, are "bad" in racing.

DavidM

Gearing and redline are inherently linked. There is no 'overal' benefit of shorter gearing unless you do extend the redline. Shorter gearing (without extended redline) will show acceleration gains only in some particular ranges of speed (eg. between 40 amd 60mph), but at the same time will show negative effect on acceleration at other speeds (eg. between 60 and 80mph).

If you could elimitate/limit the shift time, then you can get benefits from shorter gearing if you add more gears to the car. That should give you an improvement in 'overal' acceleration. To take it to an extreme, a constantly variable gearing that holds the engine at exactly the same/perfect revs at all times, no matter what the speed would give you the most optimal acceleration. Though, even here a higher redline would change what the optimal/perfect revs are and improve acceleration.

ps. When I say 'increased redline', I'm pressuming (for the purpose of this discussion) that the increase in redline does bring increase in power in the extended revs.

tarheel91

That's something I've been wondering about. Say I have a car with a 6500 rpm red line. I can use shorter gears and I understand that it would create more torque down low, but not noticeably decrease the time it takes me to go from 0-60 or w/e. If I were to extend the redline proportionately (i.e. gears that multiply torque by 1.07-1.08 and increasing the redline to 7000), would that have a noticeable effect?

brockLT1

lets break it down to the fundamentals....

gearing multiplied by torque gives you your horsepower. the ability to keep torque as high as possible higher in the revs, gives you more horsepower.

but then again, you can have a diesel rev to 4000rpm and run a 9 second quarter mile, so its all about the execution.

wills2k106

There is definitely more than one way to skin a cat. GM LSX V8 and Ferrari V8 make around the same power but because the Ferrari can rev another 2500 rpm higher it can use shorter gearing. Theoretically, the Ferrari can use a 4.10 rear to get to 180 mph while the Vette would need a 3.50 to do the same. It doesn't make one better than the other, just different.

I made all these numbers up since this is only a theoretical discussion, but it is the principals we are concerned with.

TheDonEffect

Thanks everyone for their input. I guess this theoretical discussion is difficult since certain things are linked with certain things like higher redline=higher relative power, and then it's inevitable that you will need to compare two different engines from two different ways of thinking.
I guess what it really comes down to is this: is making 200hp at 5000rpms comparable to making 200hp at 10000rpms? Does the fact that there is more revolutions make those 200hp better? Of course if the 200hp 5000rpm engine weighed 500lbs vs. the 200hp 10000rpm engine weighing 200lbs (we'll call it engine a and engine b respectively), the answer is very clear, but if A maintained all 200hp from idle to 5000 and engine by progressively got to and peaks at 200hp at 10000, I would presume a is better.
I remember reading an article a while back in sport compact car where they were doing their ultimate street car thing, and was comparing a viper and a ferrari. The ferrari won the engine comparo test despite the viper making a ton more power. They compared dyno charts and said the area under the curve of the ferrari was greater than the viper despite the higher output because of the higher redline, therefore it wins. Then I thought what good is that if the viper's gearing is taller? Shouldn't it be the area under the power curve relative to mph?

DavidM

is making 200hp at 5000rpms comparable to making 200hp at 10000rpms?

Pressuming that they are both in exactly the same car, of exactly the same weight, with power curve of the same 'shape', and they are both geared to the same speeds - then they will accelerate the same.

The hp peak number already takes into account the revs, and it should be pressumed that the gearing will be matched to the engine.

A maintained all 200hp from idle to 5000 and engine by progressively got to and peaks at 200hp at 10000, I would presume a is better.

That's right - the 200hp across the whole rev-range (no matter how low the redline) is a lot better than 200hp 'peak'. That is no matter what the redline, and it'll be progressively worse the higher the peak/redline.

funat9000rpm

scenario: lets say car A can out accelerate car B, yet car B, at least on paper, has more "standard horsepower" than car A. The untold truth is that car A makes similar power to car B but at a lower RPM... therefore, car A is faster even thought B would be faster on paper....

ts80

200hp at 5,000rpm is no different than 200hp at 10,000 rpm.

HP is a function of torque and rpm.


So just an example using your numbers:
For the 200hp at 5,000rpm...
(200 x 5,252)/5,000 = 210.08 lbs tq @ 5,000 RPM

(200 x 5,252)/10,000 = 105.04 lbs tq @ 10,000 RPM

So in general, a lot of torque is good and lot of RPM is good, a lot of both is better.
Gearing affects the RPM of the equation, so it's effectively altering which RPM you're operating at the moment.

However, RPM is not always a good thing, it depends on your torque curve. If your torque curve starts dropping after 3,000 rpm then there may not be a benefit to increasing RPM on that engine depending on how much tq gets dropped off.

High RPM is just to compensate for lack of torque. If your engine makes very little torque, you don't make much HP at low RPM, but if you can at least maintain the same amount of torque while raising RPM you can increase HP.

Let's say a car with pathetic torque...5 lbs of torque at any RPM range...it will make:
0.952 HP at 1,000 RPM
4.760 HP at 5,000 RPM
9.520 HP at 10,000 RPM
19.040 HP at 20,000 RPM
47.601 HP at 50,000 RPM
476.001 HP at 500,000 RPM

So even a car which makes as much torque as a 90 lbs girl can have 476 hp if it revs high enough.