STUPID QUESTION ( weight/hp vs 1/4 mile times )

[madman]

If my GSX weighs 3700lbs and ran a 13.2 in the 1/4 and a stock evo at 285hp weighs 3263 lbs and runs 13.3 1/4 mile, does that mean I was running more than 285hp on my GSX?

Or does things like clutchs, in which my GSX had an ACT 2600 compared to a stock EVO, make it an uneven comparrison?

 

[CanadianTSi]

Trap speed is a better way to compare Horsepower, too many variables affect ET.

 

[Black95TSIawd]

If your GSX weights 3700lbs, what the hell did you put into it? Theoretically, your assumptions would be correct, but as TY said, use the trap speed. ET has many other variables such as the driver skill.

 

[bullettdsm]

Can't do it. Example; A buddy of mine has about 540whp. He ran a 14.6 on his FWD (lots of traction problems). I ran a 14.3 with my NA but I sure don't have close to 540 whp. WAY too many variables. Driver ability, car set-up, track prep........the list goes on and on.

If the same driver drove each car, the exact same way, under the exact same conditions, using the exact same clutch set-up, with the exact same tires..........

MB

 

[drivemusicnow]

####. I had written out all the math to do this, and then the browser randomly went back. God Damn It.

Heres a much quicker shorter example of John Shepherd's Car:

Acceleration equals change in distance of Change in time
191 mph/ 7.70 seconds = 24.805 m/h/s. Converting this into ft per second squared is 16.913

Force equals acceleration times mass: 2100lbs * 16.913 = 35516 LbsF

Work equals Force Times Distance 35516 * 1320Ft = 46881818

Power is work over time, and 1hp = 33000 lb*ft/1min so we have 1420.7 HP.

Now this doesn't take into account rolling resistance of tires, air resistance, or drive train loss. SO

Air resistance equals 1/2*Cd*A*Rho*v^2
We're going to solve this at 0 (guess what, it equals 0) and at 191mph, and then average the two, and apply that as a HP correction factor
1/2 .27*20ft^2*0.075 lbm/ft3*280ft/sec^2=15876
Divide by gravity because lbm are lame units: 494.6 lbsF

(I Assumed both the coefficient of drag at .27, and his frontal area of 20ft^2)

Converting this into hp is as easy as multiplying by speed and divided by 550. We see that at 191 mph, we have a drag loss of 251 hp. Divide it by two and add it on: +125.9 HP

Drive train loss is assumed to be about 17% (I would bet Shep has it lower, but hey, lets just stick to a standard)

And I don't really know how to guess rolling resistance. It's dependant on velocity, but I have NO idea what the Cf of 4 slicks would be. Lets assume that it is about 8 times less than air resistance. (this is about 16 HP)

This means that to the wheels his car has about 1562hp (assuming no tire slip which we all know is not true) at the crank he has approx 1827.9hp

Yeah, somebody check my math cause I kinda threw these together after it deleted all of my calculations the first time around.

 

[yellowrs]

Or you can do it the easy way and just type in the factors http://www.dsm.org/tools/calchp.htm

 

[drivemusicnow]

Or you can do it the easy way and just type in the factors http://www.dsm.org/tools/calchp.htm

Maybe... but

Using the ET method, I come up with 909 horsepower
Using the Speed method, I come up with 1142 horsepower

Doesn't quite seem right for my example of 7.70 quartermile, 2100lbs, and 191 trap speed.

My math could be wrong, as I really didn't spend any time proof-reading/checking what I was doing.

 

[madman]

If your GSX weights 3700lbs, what the hell did you put into it?

3700lbs is what I found on the web for a stock 97' GSX. Now I didn't have my spare tire in the car but I bet my FMIC and Turbo added a little weight over stock. I know that I won't ever be exact figures because I don't have the exact weight of the car when I ran that time but I thought it would give me an idea of the power I was making.

 

[madman]

In simplest terms if a car at X lbs can go a 1/4 mile in y time at z hp then a car that weights >x and a 1/4 mile in =<y wouldn't it have to have >z hp?

When they report the EVO with a 13.3 1/4 wouldn't that be under best conditons?

So then with my time at 13.2, even at best conditions, in which I don't think my hot day in the summer and my limited driving abilites would be considered best conditions, and I still beat the EVO's time, wouldn't I have to be making more hp than 285?

If we look at euipment that will make a car quicker......TIRES, I'm sure my Sumoitomo HTR+ are not as good as the Yoko's on the Evo (EVO +1)......CLUTCH, I would guess my ACT2600 would be a little better than the stock EVO (my car +1)

 

[yellowrs]

Maybe... but



Doesn't quite seem right for my example of 7.70 quartermile, 2100lbs, and 191 trap speed.

My math could be wrong, as I really didn't spend any time proof-reading/checking what I was doing.

Your method does seem a little more accurate.

One question, is that what sheps car weighs for sure? And is that with driver?

 

[MrBoxx]

If my GSX weighs 3700lbs and ran a 13.2 in the 1/4

This link lists the corner weights and total weights of some cars, one of which is a stock 2g AWD. As it's listed there, the 2g only weighs around 3100 lbs, with no driver. You may want to recalculate.

 

[madman]

Or you can do it the easy way and just type in the factors http://www.dsm.org/tools/calchp.htm

So I tried this out and I think the speed method is way off but....
with my numbers it put me at 315hp (et formula)....I'm guessing this is not whp.

I put in CanadianTSI numbers since we have about the same car and it said 436hp ....which wouldn't that be close if you are making 395whp?

 

[madman]

This link lists the corner weights and total weights of some cars, one of which is a stock 2g AWD. As it's listed there, the 2g only weighs around 3100 lbs, with no driver. You may want to recalculate.

Ok 3110lbs actually....well that changes everything.
3110 + me 190lbs =3300
my car 13.242 104.99
Using the ET method, I come up with 281 horsepower
Using the Speed method, I come up with 298 horsepower

CanadianTSI figuring similar weight
11.88 120.91

Using the ET method, I come up with 389 horsepower
Using the Speed method, I come up with 455 horsepower

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