If people can just grasp what these terms mean, it would open up
many eyes.

If the motor applies a power stroke 7000 times per minute...and
each power stroke has 1000 lbs of force behind it...

Why wouldn't you want to spin the engine faster? You are getting
7000 shots of 1000 lb forces.

Even if you sacrifice some torque to let's say 800 ft./lbs., getting
more shots of power strokes at 7000 RPM is moving your car much
faster in the same amount of time.

EDIT - than 1000ft./lbs. at 5500 RPM

 

You misunderstood my post. I was disagreeing with that.

I think I disagree with both peak torque and peak horsepower. Powerband and dyno sheet mean much more to me.

 

How exactly would 800 ft.# @ 7000 rpms be faster than 1000 ft# @7000? How can you get "more shots of power" if the rpms are both 7000?

I understand the balance between TQ and RPM... but the purpose of using engine HP is to elliminate those fluctuations and know that regardless of the rpm/gearing/torque adjustment you only have a certain amount of energy to use in a given time... hp.

Rear wheel TQ works to move the car... as produced by the engine's output hp divided by the rpms the wheels must turn (depending on tire diameter, final gear ratio, and tranny ratio).

For any given gear, the most REAR WHEEL torque you can put to the ground WILL be the most ENGINE HORSEPOWER you can make. That is why in engines: hp is king, and in drivetrains aggressive gearing is used to get the most rearwheel torque possible.

 

Ahhh.. I see. Then I definitely agree with your disagree.

 

Steve,

You'd have to read my wonderful response on Page 5 to make sense
of my masterpiece above.

Read up on my "Black Eye" theory and tell me what you think

 

Torque times RPM = HorsePower

HP = TQ * RPM * .0001904

========================================

Find out at what RPM your engine makes its Peak Torque

then go to DragStrip at shift your engine at that peak torque point


then make another run..this time shifting at peak HP point


report back here in this Forum
which method produced fastest ET down 1/4 mile DragStrip pass
===========================================

" Torque times RPM" (which is HorsePower)

if you don't think HorsePower matters
then go to DragStrip and shift at Peak Torque RPM

and post if you went faster that way

i haven't yet seen anyone take the "challenge" ??,
and post any dragstrip times

 

Yeah I don't think we ever get as low as peak torque on any of our race engines.

 

Yeah I don't think we ever get as low as peak torque on any of our race engines.
===================================

yes...i don't think Greg Anderson is "trying" to keep his ProStock engine at 7800 rpm (Peak Tq Rpm) ???

in other words..you won't see Greg Anderson shifting
at 7800 Rpms

and you won't see 7800 rpm very long on his Tach

 

Yeah maybe when he initially lets off on the clutch for .01 of a second! ....Or maybe never.

 

Of course it's not faster shifting at peak torque point, but it's probably not fastest shifting at peak hp point either, right, Larry?

Doesn't the car accelerate fastest when you keep the engine working in the maximum area under the hp curve, which is maximum area under the (torque X rpm curve)?

I suggest that transmission ratios are chosen to do just that. If a PS engine does get peak torque in the high 7s, (your number) and peak hp in the mid 9s, ratio steps of maybe 1.3 in the lower gears and 1.15 or so in the higher gears might keep the engine in the 7500-9800 (lower gears) and 8500-9800 area in the higher gears. Therefore the engine is shifted somewhere past the hp peak and drops to somewhere near/above the torque peak.

I've not seen recent PS dyno charts, but my guess is that if torque peaks in the mid/high 7s at 725 to maybe 750 lb-ft, it drops slowly and stays above maybe 700 to max engine speed. That would give a hp curve with a pretty flat peak and make the shift point somewhat insensitive, unlike a hp curve with a shaper peak that tanks imediately afterward.

As consistant as PS cars are, and with engines accelerating at maybe 3000 rpm/sec in the lower gears, a wide shift point range, say 4-500 rpm would help stay consistant even if the dirver missed his optimum shift point by a tenth or tenth and a half.

Even WJ or GA probably occasionally does that.

My $.02

 

Of course it's not faster shifting at peak torque point, but it's probably not fastest shifting at peak hp point either, right, Larry?
=======================================

usually "quickest ET" shift point is from around Peak HP RPM to as much as 300 to 500 rpm above Peak Hp RPM

also, fastest ET possible => engine RPM at finish line is "above"
Peak HP RPM point

ProStock Peak Torque numbers are around 800 to 825
@ 600 Rpm/Sec ...more at slower test rates
7500 to 7800 rpm

1300 to 1330+ Peak HP 8800 to 9000 rpm
@ 600 Rpm/Sec ...more at slower test rates

i'll post a Link to "old" ProStock Graph later on

========================================


Doesn't the car accelerate fastest when you keep the engine working in the maximum area under the hp curve, which is maximum area under the (torque X rpm curve)?
---------------

yes, but most RaceCars are quickest crossing Finish Line well above RPM point of Peak HorsePower ,
and on some RaceCars you have to account for HoodScoop Ram-Air effects influences on power curve -vs- dyno


the DragStrip Simulator on this website might be using
Lagrange Interpolation to generate a curve from HP/TQ inputs
..i use my own Algorithm to generate a Torque Curve -vs- RPM points , then calculate Tractive Force (minus rotational inertia and other losses) ...to findout RaceCar's acceleration at each .001 second time increments

i'm pretty positive "every" ET Prediction program available
is really generating a Torque -vs- RPM curve from
User inputs of HP and RPM (like Quarter Jr)

..there is no Torque input in Quarter Jr.
but behind the scene, Quarter Jr is generating a Torque -vs- RPM curve (HP) and applying this Force thru Trans and Differential Ratios to calculate acceleration.

the RaceCar accelerates the fastest/quickest
with the "greatest" amount of net Tractive Force possible...within the operating RPM range, within a span of a Quarter Mile.

but the Tractive Force is mainly result of
Torque times RPM ..(which is HorsePower)
working thru effective gear ratios

 

I still say it is trq. Isn't it trq that the dyno uses to calculate what hp is? HP is just showing how efficent the motor is. If hp is more important then trq, then why is it that peak VE happens at peak trq and not hp? Logic would say that if hp is more important to ET and to an engine, that an engine should produce peak VE at peak HP. Another point is that if HP is more important to running low ETs, then it shouldn't be very hard for a desiel to run low 11s or even 10s, but we have all seen several that prove other wise. Since a F350 can run 11s then it would seem to point that it isn't neccesay to spin rpms just to build hp to get good ETs.

 

from what i understand, you can't compare the 2. i'm often wrong so please step in. from what i remember from the last time i was in here, there were 2 different equations for finding tq and hp.

the way i see the equations is that if you take a car and give it a perfectly flat hp curve (not really a curve since its flat) at say 400hp. (for the 1st car) and like a flat 100 tq line
then you get a tq curve (actually straight as well) across the 400 tq mark. (this is for the 2nd car) and like a flat 100 hp line
ok, now that you have the cars specs
from the way i see it, the faster car will be determined by the shift points. (not measuring their speeds from a stop, but lets say we tow them up to 50mph then let them race it out)
(on both cars the redline is at 10,000rpms)
like i said the winner will be who shifts at the ideal spot for their car. but if we made both cars shift so that they finished dead even then we would have a baseline. you can use the baseline for whatever you want, but you will know more how the equations relates to your power numbers and time.

now since the equation isn't based off of a 10000rpms it would be a bit harder to see on these 2 engines, which power numbers would make their performance equal. but if we made a new formula for finding hp and tq (we would have to call them something else though since they would be different units) and if we made this formula to be based off of the 10,000prm limits, just like we are using, in theory, if one car shifts at 5k (high tq car)and the other at 10k (high hp car )their times should be identical.
this is not taking a "launch" as in drag racing, as a factor since you could put a stall and all that whatnot to introduce more variables, but does this make sense to anyone?

 

Seriously, why are we shifting at 5800+ RPM in our street cars if
it's all about the Torque peak?

I like Larry's advice. Take the car to the track and shift your car
at the torque peak.

Before you go, run out and add a few more OD gears to the transmission
because shifting at 2500 RPM wont get you too far in each gear.

If you can understand that Horsepower is a measure of how many times
Torque is getting punched out per minute, then you'll see that
you want the engine spinning faster to get more events of
torque per minute.


You can move 2 pounds of dirt, 7000 times per minute

or

You can move 5 pounds of dirt 2000 times per minute


What scenario completed the most work in the same amount of time?

 

But, what is doing the work? I agree that you will go faster shifting around hp peak, but without good lowend trq and proper gearing, you won't get off the line well enough to use that peak hp. Again, I go back to the desiel. If rpms are so important, as you put it, then the desiels shouldn't be able to go as fast as they are with only about 3k rpms max.

By that description you are descibing wrok down over time which is trq not hp. A desciption of hp using your exampe would be:

You can move 2 pounds of dirt, 7000 times per minute and you move it 5ft

or

You can move 5 pounds of dirt 2000 times per minute and you move it 10ft.

While you are doing more work with the first one, you are also being less effecient, less work done with is hp, than compared to the second one.