New ct20b record. 365rwhp @ 22psi. Gen2 3sgte

[Rookie]

The only accurate way to measure power is to know the weight of the vehicle and run it down the quarter, then calculate from trap speed.

[sergei]

The only accurate way to measure power is to know the weight of the vehicle and run it down the quarter, then calculate from trap speed.

too many variables. (Atmospheric pressure, humidity, air temperature, traction, driver, wind, etc.).

[Lith]

Who cares how much power something supposedly has, dyno is a tuning tool for measuring what effects various power making related changes have - at the end of the day those specific numbers mean nothing compared to what happens when you put the combo to a real test, whether it be on the track or on the strip

[Al]

The only accurate way to measure power is to know the weight of the vehicle and run it down the quarter, then calculate from trap speed.

too many variables. (Atmospheric pressure, humidity, air temperature, traction, driver, wind, etc.).

Not really.

Say your GT4 usually traps 100mph in the 1/4. If you just roll off the line cleanly, chances are you will still run 100mph rather than dropping the clutch at 6000rpm.

If you can get the car off the line cleanly, and not miss any gear shifts, you will be quite consistent with your trap speeds. An amazing driver isn't going to get faster MPH than an ok driver.

Trap speed = horsepower.

It goes without saying that not so favourable humidity and air temps will have an effect on the trap speed, because you aren't making the hp, so you don't pull the numbers.

[iOnic]

Who cares

[Grrrrrrr!]

The only accurate way to measure power is to know the weight of the vehicle and run it down the quarter, then calculate from trap speed.

So big wings = -20HP and a tail wind = +20HP in your world?

[headshotnz]

The only accurate way to measure power is to know the weight of the vehicle and run it down the quarter, then calculate from trap speed.

Hmm, I would have thought thats what an engine dyno's for.. but whatever

[strx7]

Trap speed = horsepower.

so what happens if say you trap at say 100mph in a GT4 with a 3.9:1 RC box in it, ya then fit a 4.9:1 rav 4 box, go to the strip again and trap at 115mph because you can accelerate faster, you are still making the same power at the motor.......

[RedMist]

Trap speed = horsepower.

so what happens if say you trap at say 100mph in a GT4 with a 3.9:1 RC box in it, ya then fit a 4.9:1 rav 4 box, go to the strip again and trap at 115mph because you can accelerate faster, you are still making the same power at the motor.......

And this is why my dyno plots are used with tire diameters and gear ratios to calculate torque at the wheels. I then modify the ratios to maximise wheel torque all the way to maximum speed.
But even that isn't a full measure of engine performance. Throttle response, torque curve, rev through, etc.

[Al]

Trap speed = horsepower.

so what happens if say you trap at say 100mph in a GT4 with a 3.9:1 RC box in it, ya then fit a 4.9:1 rav 4 box, go to the strip again and trap at 115mph because you can accelerate faster, you are still making the same power at the motor.......

No you would go slower if anything. The taller gears would keep you in each gear longer, allowing you to get more speed per gear, and potentially not have to shift into 4th gear before the end of the 1/4.

[strx7]

No you would go slower if anything. The taller gears would keep you in each gear longer, allowing you to get more speed per gear, and potentially not have to shift into 4th gear before the end of the 1/4.

i only have one responce to that reply

if that is what you honestly think, you have NO idea.

[kim0663]

This whole debate and conception of a dyno is redundant and WRONG imo.
It's a relative measurement tool, not absolute...

[Lith]

No you would go slower if anything. The taller gears would keep you in each gear longer, allowing you to get more speed per gear, and potentially not have to shift into 4th gear before the end of the 1/4.

i only have one responce to that reply

if that is what you honestly think, you have NO idea.[/quote]

Actually I'm leaning towards the contrary on that one, especially if you actually think you'll gain anywhere near 15mph on the strip by doing that!

I actually feel that trap speeds on drag strips are a more consistant way of getting an indication of relative power than dynos, different dynos can read up around +/- 7% for a given car. I found at least using my Skyline that my trap speeds ranged from 110mph-113mph depending on a good or bad day weather wise, tyres, how good I drove so long as there wasn't a complete epic fail resulting in excessive "coasting". I changed tyre size, tyre pressure, tyre type, and rims on a variety of those... everything from 255x40x17 Nankang NS2s running 32psi to 26x11.5x16 MT ET Streets running 12psi.

Using my own car as an example - my dyno results deviated by as much as 10% with no changes between dynos, while my trapspeeds deviated by about 3%.

[strx7]

that diff ratio gives 25% more applied torque at the wheels and it accelates like you have 25% more torque. perhaps it wont gain 15mph but it would sure gain, and it sure as hell wouldn't go slower. working on the "it would go slower" logic, why do cars even have a 5 speed box? might as well just have a 2 speed box with a low and a high as some people think it would accelerate just as fast.........

what diff ratio is your skyline? a 4.1 or there abouts? put a 5.1:1 in the back there and tell me you aint going to get down the strip faster. you'll probably get closer to running out of rev range in 5th gear.....

[saft]

i only have one responce to that reply

if that is what you honestly think, you have NO idea.

now this is an interesting one, because its a great candidate for calculation and comparison.

it depends on on the power/torque curve and gear ratios amoung other things.

i remember back in the day you had something like "torque is cheap, power costs money" in your sig on sdu? i still dont agree with that

[Lith]

why do cars even have a 5 speed box? might as well just have a 2 speed box with a low and a high as some people think it would accelerate just as fast.........

Funny you should say that! Ever heard of a Powerglide?? Here's one of the worlds fastest Supras ... it runs a 2speed gearbox:
http://www.youtube.com/watch?v=rBSU-vQ1pAQ

Should teach them a thing or two?

[saft]

just for fun i tested out some numbers in Cartest
http://www.cartestsoftware.com/index.php

Its not the be all and end all but it lets you make simple comparisons.

1990 Celica All Trac was already in the database, so i used that.

4.29:1 final drive: 15.43 @ 87.57
5.29:1 final drive: 15.47 @ 86.84

[Grrrrrrr!]

why do cars even have a 5 speed box? might as well just have a 2 speed box with a low and a high as some people think it would accelerate just as fast.........

Funny you should say that! Ever heard of a Powerglide?? Here's one of the worlds fastest Supras ... it runs a 2speed gearbox:
http://www.youtube.com/watch?v=rBSU-vQ1pAQ

Should teach them a thing or two?

Bit of a difference between something that has enough power to smoke the tyres at 100mph and the other 99% of cars out there.

[Akane]

Sums up this thread.

[Al]

You are just jelly Akane