HP Rating NOT Really Overrated As Some Think

ZKindaGuy · 11-07-2009, 02:25 PM

Quote:

Originally Posted by vash_241987

ssoooo the fatter you are the more HP your car will have

at my weight a 370z would have 5000000hp

........but on a serious note what is with the extra weight and the extra 2hp?

HP is actually a function of weight. I know its confusing but think about it this way. The heavier the total load that is moving the greater HP is required to move the load in that given time over that given distance. It isn't that the engine is manufacturing more HP....its that the calculation formula figures the vehicle's HP to be "x" given the stated weight, time, speed and distance traveled. That is why the 1/4 mile is the truest indicator of what a car's HP is on any given run.

Modshack · 11-07-2009, 02:38 PM

Quote:

Originally Posted by ZKindaGuy

The heavier the total load that is moving the more HP is required to move the load

Here's a great (funny) article on the whole concept of weight Vs. speed....

SCC Technical Assistance Program

gleonard · 11-07-2009, 02:25 PM

it means the extra weight would need 2 more hp to go that fast in the 1/4 mile

Z eliminator · 11-07-2009, 04:11 PM

Go to the drag section My 370 7 At ran 12.8009. on street tires. 19's/
i just missed 12.7 the car has bolts ons and i dynoed at 291.6 RWHP.
The dyno read low.
What horse power would you rate myt car at/

semtex · 11-07-2009, 04:23 PM

Quote:

Originally Posted by Z eliminator

Go to the drag section My 370 7 At ran 12.8009. on street tires. 19's/
i just missed 12.7 the car has bolts ons and i dynoed at 291.6 RWHP.
The dyno read low.
What horse power would you rate myt car at/

How do you figure the dyno read low? Dynos measure HP at the wheels, not HP at the flywheel.

MightyBobo · 11-07-2009, 04:30 PM

Quote:

Originally Posted by semtex

How do you figure the dyno read low? Dynos measure HP at the wheels, not HP at the flywheel.

I think he means the dyno reads low compared to other dyno's.

Either way though, depending on the boltons, seems like about right to me, though...

ZKindaGuy · 11-07-2009, 09:11 PM

Quote:

Originally Posted by MightyBobo

I think he means the dyno reads low compared to other dyno's.

Either way though, depending on the boltons, seems like about right to me, though...

No Semtext was right... I too think the guy wasn't thinking dyno RWHP v. track crank-HP.

ZKindaGuy · 11-07-2009, 09:31 PM

Quote:

Originally Posted by Z eliminator

Go to the drag section My 370 7 At ran 12.8009. on street tires. 19's/
i just missed 12.7 the car has bolts ons and i dynoed at 291.6 RWHP.
The dyno read low.
What horse power would you rate myt car at/

Your crank HP would be as follows:

Assuming:
180# body weight
assuming 1 gallon fuel and mods equal to OEM parts in weight
= 3465 lbs total weight

343 crank HP which means your mods are netting you a real +10 HP gain at the flywheel. Forget the dyno crap because they are estimates at best. The track HP is the real truth of the matter as it is a test based on the real loads experienced by the vehicle.

kannibul · 11-07-2009, 09:58 PM

Quote:

Originally Posted by ZKindaGuy

Just for the heck of it I decided to run some 370Z 1/4-mile track numbers I found on the Internet to see what the HP numbers calculate to using a HP calculator. Here is what I started with:

Best 1/4-mile time I found:

13.1 @ 108.9 MPH

370Z spec:

Bone stock
MT-6
Spec weight
car is 3278 lbs empty
car is 3285 lbs assuming 1 gallon of fuel.

Best 1/4 mile time found: 13.1 seconds

Assuming driver #1 weighs 180 pounds (the weight of an average man) the total weight at race time is: 3465 lbs

Assuming driver #2 weighs 200 pounds (an above average weight) the total weight at race time is: 3485 lbs

Calculation results:

HP with driver #1: 326.94 HP at the flywheel

HP with driver #2: 328.83 HP at the flywheel

So my conclusion is that given the stated Nissan spec rating of 332 BHP the 1/4-mile track numbers tend to support such an OEM rating by +/- 4 HP.

You might have to account for drag and tire slip, and it'll probably tie out.

ZKindaGuy · 11-08-2009, 08:44 AM

Quote:

Originally Posted by kannibul

You might have to account for drag and tire slip, and it'll probably tie out.

Very true! Thanks!

j.arnaldo · 11-08-2009, 11:22 AM

I read somewhere else in these threads that they did a dynamometer test on a GT-R, and the results were 510hp, instead of 480!!! Hard to swallow, man!...???

vipor · 11-08-2009, 12:46 PM

Quote:

Originally Posted by j.arnaldo

I read somewhere else in these threads that they did a dynamometer test on a GT-R, and the results were 510hp, instead of 480!!! Hard to swallow, man!...???

that's what she said

Z eliminator · 11-08-2009, 12:52 PM

My base line dyno was 260.5 RWHP. with a warm engine. It made 266 on a cool engine.
all my #s are RWHP.

11-07-2009, 04:11 PM	#4 (permalink)
Z eliminator A True Z Fanatic Join Date: Jul 2009 Location: Ontario Canada Posts: 1,660 Drives: 370 Z 7AT Sports Rep Power: 20	Go to the drag section My 370 7 At ran 12.8009. on street tires. 19's/ i just missed 12.7 the car has bolts ons and i dynoed at 291.6 RWHP. The dyno read low. What horse power would you rate myt car at/ __________________ 12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

11-08-2009, 12:52 PM	#13 (permalink)
Z eliminator A True Z Fanatic Join Date: Jul 2009 Location: Ontario Canada Posts: 1,660 Drives: 370 Z 7AT Sports Rep Power: 20	My base line dyno was 260.5 RWHP. with a warm engine. It made 266 on a cool engine. all my #s are RWHP. __________________ 12.343 @114.14 . 4.5 stroker motor is now being built. Dec 1 2015.

11-07-2009, 02:25 PM	#3 (permalink)
gleonard Base Member Join Date: Jul 2009 Location: Los Angeles Posts: 196 Drives: 370z Touring/Spt 6sp Rep Power: 17	it means the extra weight would need 2 more hp to go that fast in the 1/4 mile

11-08-2009, 11:22 AM	#11 (permalink)
j.arnaldo Banned Join Date: Oct 2009 Location: Puerto Rico Posts: 937 Drives: Nissan 350Z, 2004 Rep Power: 0	I read somewhere else in these threads that they did a dynamometer test on a GT-R, and the results were 510hp, instead of 480!!! Hard to swallow, man!...???