The truth about American's Horsepower

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super cirrus

super cirrus

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Kenkredible
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Kenkredible
Power ratings of the Big 3's supercars from the December issue of Motor Trend:


Chevy Corvette Z06
Claimed: 505 hp
Dyno: 453 hp
Actual HP Est: 530~ish


Dodge Viper
Claimed: 510 hp
Dyno: 447 hp
Actual HP Est: 530~ish


Ford GT
Claimed: 550 hp
Dyno: 535 hp
Actual Hp Est: 600 hp

Whoa...
 
Yep, funny thing is the Japanese always tend to dyno out a lot lower than they should...

Don't forget Ford's fiasco with ('99?) Mustang Cobras not putting out claimed horsepower though...
 
There have been reports that the new Civic Si is dynoing WAY high. Car is supposed to make 200hp at the crank, but they are dynoing at like 195-200. This happens a lot. The Evo 8 made "271hp" from the factory, and dyno'd at about 230. The Evo 8 MR, which made "276hp" from the factory, only 5hp more, they dyno'd at like 245-250. This is nothing new really.

Hilg
 
Why is the actual horsepower higher then the dyno horsepower?

But typically when they dyno cars they just dyno the motor itself not in the car.
 
The rated hp for a car is at the crank, just the engine with accessories. But, once in the car, the dyno hp at the wheels is less because of driveline losses. Take an old Integra GSR. They were rated at 170hp at the crank. But, once in the car, after the power gets through the trans, and axles and what not, you get about 150hp. The losses are more for AWD cars also, because of the ammount of driveline. Thats why you always see cars dyno less than rated power. But, as shown here, there are cars that the manufacturer rate low, which actually make much more power.

Hilg
 
Got it, I was figuring that what it was.

But ya I know all about drive line loss, my truck is rated at 190hp, but when I put it on a dyno it was showing a little under 160hp.
 
My Talon makes 564 to all 4 wheels. :D

As a side note to this, I read something very interesting about the new Veyron. The actual thermal power output of the engine is a shade under 3000hp. But, after 1000hp gets lost in the cooling system, another 1000hp is lost out the exhaust, leaving 1000hp to go through the axles. Thats a very extreme example, but it really shows you how much dynamic power an engine really makes.

Also, wherever I read all this, they said that all the Veyron engines so far, even though they're rated at 987hp (1000ps), they have made over 1040hp. Now, a 50hp jump isn't much for that car, when your talking in thousands. But, thats a lot of juice.


Hilg
 
Actually the ford GT's "supposed" HP is like 615 or believe..
GT is still the beast from states, I don't care what vette people say..

That 5.4L is freaking amazing..

P.S...all that came from a very interesting "motor trend"(I think) article this month...Would anyone like to post the article? because I didn't get a chance to read the last 2 pages.
 
Let's not forget that how well the Motor is broken in is a big factor here--I've seen 350Z's dyno at 221 & I've seen them dyno in high 240's as well<--all stock vehicles
 
Evo magazine have started to dyno test cars. It'll be interesting to see what results they throw up in the future.

Why do manufacturers quote at the crankshaft :irked: Couldn't they just make it law or mass agreement to show HP at wheels?
 
No, because different dynos show different ammounts. They just measure the power at the engine to keep it consistent. It makes you guess a little as to what the engine makes at the ground, but at least you know how they got the original number. If they were using power at the wheels, you'd have to factor in what kind of dyno they used, what conditions, what gear, all that. Just too many other factors to mess it up more.

Hilg
 
I have heard that gearing can help/hurt chassis dyno numbers, but I'm not clear on how that works. I would think taller gearing means less driveline power loss because they always do pulls in top gear, but why?

Can someone explain wheather taller gearing is good/bad and why?
 
skip0110
Yep, funny thing is the Japanese always tend to dyno out a lot lower than they should...

Don't forget Ford's fiasco with ('99?) Mustang Cobras not putting out claimed horsepower though...
Click to expand...


They made up for it with the 03+ cobras. "390" hp engine making 360-380 whp. Not to metion its easier to mod than an Xbox.
 
skip0110
I have heard that gearing can help/hurt chassis dyno numbers, but I'm not clear on how that works. I would think taller gearing means less driveline power loss because they always do pulls in top gear, but why?

Can someone explain wheather taller gearing is good/bad and why?
Click to expand...

Gears multiply the engines torque, so they always try to dyno a car in the gear closest to 1.00. Otherwise, the numbers will be less accurate idea of how much power the engine really produces. Or something like that.
 
neanderthal
torque can be mulitiplied with a gearbox. power cannot.

why they use a near 1:1 ratio i dont know.
Click to expand...
Thats what super Cirrus said, and what we're talking about. As far as I understand, the 1:1 thing is just to take the gearbox out of the equation. By taking a measurement at the wheels, you always have some unknowns. But, by using the gear that is as close to 1:1 as possible, it just takes that possibility for problems out of the equation. Thats what I understand is the reason, but I don't honestly know that I've ever heard a real solid answer to that.

Hilg
 
Driftster
Actually the ford GT's "supposed" HP is like 615 or believe..
GT is still the beast from states, I don't care what vette people say..

That 5.4L is freaking amazing..
Click to expand...
Why don't you care what Corvette people have to say? Is it because the Z06 surpasses the GT in nearly every peformance category while doing it at 1/2 the price?
 
Slick6
Why don't you care what Corvette people have to say? Is it because the Z06 surpasses the GT in nearly every peformance category while doing it at 1/2 the price?
Click to expand...

Don't forget the somewhat-more-practical part. :) 👍 I've never been a GM fan, or even an american car fan, but I'm very impressed with the C6 Z06. :)

As for the horsepower topic...

@JNasty: Those power drops you mentioned in your first response are simply drivetrain losses, as you later said, and have nothing to do with under/overestimated horsepower ratings.

Some of the recent hoopla with under/overestimated horsepower numbers is because of a change in the SAE standard. Japanese manufacturers exploited some loophole in the old standards, which has now been eliminated, so many Japanese engines have lost some power. Incidentally, some American engines gained from the new standard. Of course, American car fans have eagerly taken this as an opportunity to rag on imported makes...
 
Wolfe2x7
@JNasty: Those power drops you mentioned in your first response are simply drivetrain losses, as you later said, and have nothing to do with under/overestimated horsepower ratings.
Click to expand...
So, a new Civic Si making close to 200hp at the wheels, all while being rated at 197hp, that isn't an underestimated power output??? And, an Evo MR thats only rated at 5hp more than the standard Evo, but makes close to 20hp more. Thats not underestimated??? And, I suppose all the SRT-4s that dyno with more power to the wheels than the rated crank power is normal as well, right??? Ok, I must be mistaken. Those are right where they're supposed to be.

:rolleyes:

Hilg
 
JNasty4G63
As a side note to this, I read something very interesting about the new Veyron. The actual thermal power output of the engine is a shade under 3000hp.
Click to expand...

The most efficient engines would be lucky to get up to 50% thermal efficiency, I think a street car would be around 30%... so a 300hp car could be putting out 1000hp, 700hp being heat.
 
retsmah
The most efficient engines would be lucky to get up to 50% thermal efficiency, I think a street car would be around 30%... so a 300hp car could be putting out 1000hp, 700hp being heat.
Click to expand...
Right, I understand that much. But, its just amazing when you read that number. 3000hp worth of dynamic output. Thats a lot of engine, making a lot of heat.

Hilg
 
It would be easier if sports cars could have a claimed output of "lots".
 
Hehe that's the kind of crazy thing we do!

Lotus could quote for the Elise- "Not enough"

Bugatti could quote "More than Robert Mugabe, less the God".
 
super cirrus
Gears multiply the engines torque, so they always try to dyno a car in the gear closest to 1.00. Otherwise, the numbers will be less accurate idea of how much power the engine really produces. Or something like that.
Click to expand...

Isn't that 1:1 gear ratio you usually see on spec sheets just in the transmission? There is still a final gear to go through, plus the size of the tire will change what the dyno picks up.

My guess, without knowing at all how a dyno works, is that they run the car on the dyno and hook up a tach to the car. If you know how fast the car is going, what the force is at the rear tire, and what the engine speed is, then you can figure out gearing and get the power and torque curves.
 

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