Kind of intresting no?

If you know what your car weighs..and what power it makes..you can figure out how much weight = how much power.

My car made 171 WHP and 144 TQ. At 2366 LBS..thats a ratio of 13.83:1 HP/16.43:1 TQ.
If you drop the weight to 2266..and divide by the HP/TQ..the ratio drops to 13.25:1 HP / 15.73:1 TQ.
Plug the new ratios in and you get 178.3 WHP and 150.5 TQ.

Kinda neat huh?

 

WOW, thats sweeeeeet

time to visit the recycling center to weigh my car

oh and i need to dyno to see where im at

 

Where do you get the 100lbs = 7.3 whp?

 

I thought I explanied it?

Ok..so if I made 171 WHP...you take 2366 LBS and divide it by 171 and you get 13.83. So..that means every 1 HP has to move 13.83 LBS.
If you drop 100 LBS and divide by 171...you get 13.25:1

So..then you start "guessing" how much HP does it take to get a 13.25:1 ratio with a car that weighs 2366 LBS.
Divide 2366 by 178.3 and you get roughly 13.25.

So...a car weighing 2366 and making 178.3 WHP is the same as a car weighing 2266 and making 171 WHP.

Make sense?

 

great...now all I gotta do is dyno the car........



Good info HX....!

 

I got it now. I'm slow today. Pretty smart.

I always heard 10lbs = 1hp. Which I guess is probably about right if you're talking flywheel hp.

 

Good thought but, but lbs is not equal to HP - Ever. What you have discovered is the power to weight ratio.

You don't gain HP, you loose weight, and your power to weight ratio will decrease. Meaning it takes less power to achieve the same performance. That's how murdercycles go so fast, they onyl weight 600 lbs, and have 140 hp.

P-W ratios = (600 +my big but ~200)/140 = 5.7

As you can see this is not linear. Meaning the murdercycle should be 2.3 times faster than the R if it was linear. It is not because many other things need to be accounted for that are beyond the realm of this conversation.

BTW a full tank of gas wieghs ~ 100 lbs. So don't fill it before you go racing, but remember you will get ~ 11mpg in VTEC so don't run out.

Have a good weekend

 

I totally agree. And he shows that by saying that his ratio has dropped from 13.83:1 to 13.25:1
Also, you say it takes less power to make the same performance, and likewise (his point) same power in lighter car = more performance.

Now I have a question. This difference only shows up when measuring whp and not crank, correct? It makes sense in my head that it would only be whp, but I have a cold and am drugged up on Nyquil.

 

Yes I realize that actual HP isnt gained..duh.

My point was..that losing 100 LBS is like gaining 7.3 WHP...not that you actually gain it...theres a differance.

WHP or crank HP..doesnt matter what figure you use.

 

By explaining it this way , yes it makes sense. Above makes it seem as though you thought you gained power by taking away wt. good post though !

Bryan

 

Way to figure it out Bryan. Now hit the weightroom so your fat *** can get out of turn 8 quicker!

Hey HX Guy - I have a stock ITR, more or less. with my mods, it has 171whp and 125wtq. I weigh 130 lbs soaking wet. With spare removed, which is how I run, what's my pwr/weight ratio? Im only asking cause I dunno how much a stock R or spare tire weighs.


[Modified by Ross1013, 7:10 AM 9/29/2001]

 

In other words, he is try'n to say he is HALF of a man "130lbs" is gonna be soaking wet, and 10 extra pounds in his pocket!!

Oh, and for the record, im 6ft and weigh 180, maybe a few more whats "my : power the weight ratio? lol

Bryan


[Modified by VAtypeR00, 8:15 AM 9/29/2001]

 

Power to weight ratio is only one part of the equation. The engine of a car has to do two things:

1) Accelerate the mass of the car; and
2) Fight against the drag of the car.

As the speed of the car increase, the engine fight more against the drag and less to accelerate the mass…

So, given the same power to weight ratio, and given the same drag coefficient, a heavier car with more power would be faster (on a straight line, don’t want to talk about handling here) than a lighter one with less power. And that just because the power to drag ratio would be better on the heavier car. The top speed on the heavier car would be higher also for the same reason…

Thats also the reason why its not linear...

 

I don't think it would make much of a difference, but from my limited understanding you should loose a percentage through you drive train. Whether that is linear or not I don't know. This could change depending on RPM, heat, oil viscosity, material used, miles on the gear box, clucth, etc...

I figure the ITR is probably about 8-9%. Based on 195 @ the crank and 170 @ the wheels. RWD cars are typically higher, drive shafts suck up a lot of power! I would guess as high a 15-20%. That's one of the reasons a FWD car gets better milege.

All this discussion is nice, but I still say learning to truely push your car to the limit is the way to go faster. Chances are, if your not pushing your car, you probably won't notice 100 lbs difference. I've hear many people say the "push" their car, but do they? I find the R way too fast to really push in the street.

The rule of thumb for my CRX was double the speed sign. So if an off ramp is marked 25 I could usually go 50. The R seems to be closer to 3x! Sorry drifting 70-75mph through a clover leaf to a blind corner in the street is just a little too exciting for me! Save it for the track.