Just thinking about hp - FMVperformance.com : The site for all your Ford Mazda and Volvo needs
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post #1 of 24 (permalink) Old 01-19-2007, 10:45 AM Thread Starter
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Just thinking about hp

I'm a bit bored at work so I gots to thinkin'

How do car companies determine power at the crank? Do they go by whats on there and it's basically a good estimate on what it has and how it's tuned? I think the standard should be what the car is doing at the wheels. power at the crank does nothing for at least me cause a 300 at the crank car can be putting out only 235 at the wheels and a 260 at the crank car can be putting out 245 at the wheels and i would prob choose the 260 hp car (being it's the same car lets say). There is too much excitement about omg this car is 300 hp but who knows what it has at the wheels (if the car is "Coming soon" and the public hasn't dyno'ed it yet)

Like i said, I think companies should start advertising WHP and not at the crank.

thoughts? answers?


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post #2 of 24 (permalink) Old 01-19-2007, 10:54 AM
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Re: Just thinking about hp

I think it's kind of akin to advertising the purchase price, rather than the price with tax, title, license, etc. They could just as well tell you the higher figure, which is much more useful when trying to compare vehicles, but it's better advertising to go with the lower number. As long as they're not being intentionally deceptive, there's nothing technically wrong with it--it's just not as helpful to the consumer.

When you consider that at least 90% of people probably have no idea what their car puts out--to the wheels or otherwise--manufacturers only give out hp numbers as a sales pitch, rather than for any kind of hard and fast comparison.

Plus, nobody would buy an ATX when they saw the WHP numbers compared to a manual


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post #3 of 24 (permalink) Old 01-19-2007, 10:55 AM
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Re: Just thinking about hp

I think ATX loses about 10hp. Once your boosting it dosent matter. 8)
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post #4 of 24 (permalink) Old 01-19-2007, 10:56 AM
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Re: Just thinking about hp

I believe car companies would like to advertise the highest HP numbers possible, thus why hearing the crank numbers from the engine dyno. The drivetrain loss figure is normaly %14-6 for a manual and a bit more for a auto car (subject to change). I myself would like to see WHP figures vs. the crank hp figures but I don't think it will happen.


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post #5 of 24 (permalink) Old 01-19-2007, 10:57 AM Thread Starter
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Re: Just thinking about hp

really!?

I thought whp was the same...but MTX can get the revs up before moving for a better launch...I didnt think ATX looses power...that sucks!


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post #6 of 24 (permalink) Old 01-19-2007, 11:13 AM
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Re: Just thinking about hp

[quote author=saluteTOme link=topic=67339.msg1157599#msg1157599 date=1169221535]
I'm a bit bored at work so I gots to thinkin'

How do car companies determine power at the crank? [/quote]

SAE Net Horsepower is basically an expression of watts of power output... and can be expressed in watts (not a 1:1 conversion, obviously)

Crank horsepower is the theoretical ability of the engine, minus frictional loss from internal engine components, measured at the crankshaft.

Quote:
I think the standard should be what the car is doing at the wheels. power at the crank does nothing for at least me cause a 300 at the crank car can be putting out only 235 at the wheels and a 260 at the crank car can be putting out 245 at the wheels and i would prob choose the 260 hp car (being it's the same car lets say). There is too much excitement about omg this car is 300 hp but who knows what it has at the wheels (if the car is "Coming soon" and the public hasn't dyno'ed it yet)
There's pretty strict standards these days for advertised numbers, so you don't generally get LARGE variations. That being said, of course there are variations.

Should they advertise WHP and not Net HP? Probably... but there's so many things that effect WHP that they'd have to be constantly retesting, it'd be a major pain in the ass.
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post #7 of 24 (permalink) Old 01-19-2007, 01:07 PM
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Re: Just thinking about hp

[quote author=MZ6ZoomZoom link=topic=67339.msg1157647#msg1157647 date=1169223223]
[quote author=saluteTOme link=topic=67339.msg1157599#msg1157599 date=1169221535]
I'm a bit bored at work so I gots to thinkin'

How do car companies determine power at the crank? [/quote]

SAE Net Horsepower is basically an expression of watts of power output... and can be expressed in watts (not a 1:1 conversion, obviously)

Crank horsepower is the theoretical ability of the engine, minus frictional loss from internal engine components, measured at the crankshaft.

Quote:
I think the standard should be what the car is doing at the wheels. power at the crank does nothing for at least me cause a 300 at the crank car can be putting out only 235 at the wheels and a 260 at the crank car can be putting out 245 at the wheels and i would prob choose the 260 hp car (being it's the same car lets say). There is too much excitement about omg this car is 300 hp but who knows what it has at the wheels (if the car is "Coming soon" and the public hasn't dyno'ed it yet)
There's pretty strict standards these days for advertised numbers, so you don't generally get LARGE variations. That being said, of course there are variations.

Should they advertise WHP and not Net HP? Probably... but there's so many things that effect WHP that they'd have to be constantly retesting, it'd be a major pain in the ass.
[/quote]

Ding ding, well put!


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post #8 of 24 (permalink) Old 01-19-2007, 01:19 PM
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Re: Just thinking about hp

well.......also, and i was told by a service guy at my dealer....... and he is a BIG tuner, and is pretty knowledgeable about cars...

basically, the number that it is advertised as (our car being and example, or my car anyways, a speed 3). 263 HP is what the car has in Japan.... but due to emissions restrictions in the US, they modify the car a bit to meet the US emissions standards.

the guy said that when you have a FWD car, and the engine and tranny are sitting right on top of the front axle, you are not going to have a whole lot of HP loss from the crank to the wheels...


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post #9 of 24 (permalink) Old 01-19-2007, 01:44 PM Thread Starter
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Re: Just thinking about hp

what? No, they can't/wouldn't do that. Its like advertising for an applicance in the US when it has a european plug.


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post #10 of 24 (permalink) Old 01-19-2007, 01:56 PM
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Re: Just thinking about hp

well look at VW.....there numbers are Whp.....the gti is advertised at 200hp and that is what it gets to the wheels. I think alot of Euro's advertise with actually whp numbers

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