Question for 95 GSX racer or anyone else

[metalhedskater]

Ok so i was reading the HP doesnt win races thread and i have a question for you.

Okay so i suck at math and physics, but let me try to understand what yoy are saying. Okay so read this thing online where it said Gsts have 214lbft Tq @3000rpms, and 210 HP @ 6000rpms. Which equals 122 hp? Does that mean if we maximized our RPMS to 6000 when driving, we would have 244 hp. Im lost help. ALso is that why when you highly modify your car you need to cange the gears and gear ration or whatever. WHy do that? How can we maximize our RPMS?

Please help i am confused and i wanna know more.

[JoeWagon]

although i can assure you i HAVE read the truth about power, ive never heard any of that crap about coming up with a new number of power, and i dont plan on looking at that thread to find out. i cant remember the specifics of what i read, but it was that torque is power, and something about horsepower in relation to being able to hold torque longer in a gear. the larger the rpm range that you can hold a near-peak torque at, the better. if that makes sense, add it to your knowledge base

[kjewer1]

Good summary of that concept

What you can assume is that at 214 ftlbs at 3k rpm, you have 122 hP like you said. At 6k rpms you musthave ~185 ftlbs to have 210 HP. So thats actually a pretty decent tq curve, and not uncommon for a turbo car. And you are correct in saying that if you could make that 214 ftlbs at 6k rpm, youd have 244 HP, or a 34 HP increase for a 30 ftlb increase. The further above 5252 rpm you get, the bigger the impact on HP a given increase in TQ will give you. You are also correct in the issue about cams and gears. Cams will move the peak airflow per revolution (or intake event) higher in the rpm band, increasing torque (torque follows airflow per rev). And higher rpm torque makes more power. Interstingly enough, HP tends to follow your airflow per time curve, like lbs/min, so increaseing your airflow per rev at higher rpm also increases the airflow per time at that point. This corresponds to the HP increase you see. It all works out If you drastically change the rpm characteristics of the motor, a change in gearing may be necessary. A motor that ends up with a very narrow power band will do well with a close ratio gearbox to avoid dipping below the power band. A motor with a wide torque range (like a turbo 4g63) will do better with a regular, wider spaced set of gear ratios so you have more time spent in gear (turbo stays spooled as well).

SOme of this stuff is almost worthy of a whole other novel, but I hope it answers some of the questions.

[metalhedskater]

okay cool.....thanks a lot for the info....But i have another question....why does it say the eclipse only has 210 horse power? why dont they measure the torque at higher RPMS? why do they do it at lower RPMs? i dont get it.

[kjewer1]

210 is all that motor makes. It just happens to peak at 6k rpm. Ad tq just happens to peak at 3k. They measure all rpms, then give the highest tq (and what rpm its at) and highest HP (and what rpm its at) Moving the tq up, or increasing it, is why we mod the car.

[EclipseRST]

so let me get this straight, it wont make anymore than 214 ft lbs of torque from 3k rpms and up? if not then isnt the other 3500-4000 rpms to redline a waste of power then? i'm lost, sorry.

[JoeWagon]

I just got done reading the hp vs torque article in this month's hot rod magazine.. i suggest you go check it out for that, and also J. Shep's car is featured!! a must read!

For your prev. question, they measure torque and horsepower at peak because it sells cars.

Note that torque is always greatest at low RPM because it has plenty of time to fill the cylinder, where at higher RPM the opposite is in effect; not enough time.

EDIT>> The only answer that I can come up with in response to prev. post is that if torque dropped SEVERELY after the peak, it would be geared around that RPM as you suggested, however, DSM's aren't considered (in comparison) to have a narrow enough power band to want such a thing, and i'm almost positive that even though there is less torque at higher rpm, it would still be faster in the quarter to forfeit shifting so much and wait out each gear. Also take into consideration that peak torque is probably with full boost, and you wouldn't have that at such low rpm.

Alas, i'm positive there's a fundamental concept that would answer it, but i think those are two reasons in non-technical terms.

[kjewer1]

Originally Posted by JoeWagon

Note that torque is always greatest at low RPM because it has plenty of time to fill the cylinder, where at higher RPM the opposite is in effect; not enough time.

Exactly. Volumetric Efficiency. I said in this thread or another that torque peak will be at your airflow per rev peak. And airflow/rev is just a measure of columteric efficiency essentially. And just as you said, its better at low rpm, and worse at high rpm. The turbo car has one other oddity about it. Our airflow/rev peak will actually be as soon as boost peaks. So if you get full spool before 3k rpm, thats where your torque will peak. The lowest rpm, but the highest boost, is your VE peak.

EDIT>> The only answer that I can come up with in response to prev. post is that if torque dropped SEVERELY after the peak, it would be geared around that RPM as you suggested, however, DSM's aren't considered (in comparison) to have a narrow enough power band to want such a thing, and i'm almost positive that even though there is less torque at higher rpm, it would still be faster in the quarter to forfeit shifting so much and wait out each gear. Also take into consideration that peak torque is probably with full boost, and you wouldn't have that at such low rpm.

Alas, i'm positive there's a fundamental concept that would answer it, but i think those are two reasons in non-technical terms.

This is that fundamental concept: Since torque is multiplied by rpm (Then divided by the constant, 5252), torque can be falling, but because rpm is rising, HP is also rising. Now if the torque increases with rpm, or even just stays flat HP will rise quickly s well, since its multiplied out. Look at a number of dyno charts and you will see this in action. Torque is falling, but HP is rising. At the point that torque drops faster than rpm is rising, HP will flatten out and start to drop off as well.

[95_GSX]

since VE was bought up i have a question, at what CFM and PSI can you essentially double your displacement? i also understand that there are two variables so it can occur in many different ways. thanks.

[kjewer1]

With a free flowing intake system, if you double atmospheric pressure, you have effectively doubled your displacement. So at 15 psi (stock 2g is 14) you basically have a 4 liter. At 30 psi, its basically a 6 liter. As I have said before the amount of power you make is directly proportional to the amounf of air you flow (well tuned). So if you move 50 lbs/min you'll be making about 500 whp. Wether you move that 50 lbs because you have a 5.7 liter motor, or because you cram the same amount of air into a 2 liter, its the same thing effectively.

[95_GSX]

Thanks this was a concept me and a friend were always throwing around, but i wasn't ever sure exactly how it works.