rwhp loss through the drivetrain

98stangv8 · Dec 26, 2008

Ok...I have a 5 speed...how much horsepower loss is generally accepted as to being lost from the engine to the rear wheels?

Thanks!

BurningRubber · Dec 26, 2008

Around 15% of your flywheel horsepower for a 5 speed. That is not exact, but a fairly common figure.

texas01gt · Dec 26, 2008

these engines are rating at 260hp at the flywheel...i had my car dynoed STOCK AS A ROCK!!...save for some SLP mufflers...stock H pipe with all 4 cats though..and i put down 230hp to the wheels, thats with a 5 speed.

98COBRA281 · Dec 26, 2008

BurningRubber said:
Around 15% of your flywheel horsepower for a 5 speed. That is not exact, but a fairly common figure.

i hate when people say a percentage, because its not true at all, so 1000 crank hp, would mean 150hp loss throught the drive train, which is crazy..

manual 30-35hp loss

98stangv8 · Dec 26, 2008

98COBRA281 said:
i hate when people say a percentage, because its not true at all, so 1000 crank hp, would mean 150hp loss throught the drive train, which is crazy..

manual 30-35hp loss

the guy above was at at 12% loss...I have heard 10-15%....if you are running 1000 hp at the crank...you are going to lose more than a guy running 260 hp at the crank...so it should be more of a %age than a number...

98COBRA281 · Dec 26, 2008

98stangv8 said:
the guy above was at at 12% loss...I have heard 10-15%....if you are running 1000 hp at the crank...you are going to lose more than a guy running 260 hp at the crank...so it should be more of a %age than a number...

why would you lose more hp just because you make more power? theres no difference.......

CobraRed_96_GT · Dec 26, 2008

98COBRA281 said:
why would you lose more hp just because you make more power? theres no difference.......

Move an oar through water, then move it 5 times the speed through water. Notice a difference? Relate to oil respectively.

It's %

98stangv8 · Dec 26, 2008

anyone else have some insight into this?

CobraRed_96_GT · Dec 26, 2008

98stangv8 said:
anyone else have some insight into this?

i usually say 14-15% through a 5 speed or 6 speed, and 18.5-20.5% on a 4R70W depending on build.

98stangv8 · Dec 26, 2008

CobraRed_96_GT said:
i usually say 14-15% through a 5 speed or 6 speed, and 18.5-20.5% on a 4R70W depending on build.

I agree with your %age analogy...nice

96SCstang · Dec 27, 2008

it is a very true statement to say you will lose more power if you make more power. the general rule of thumb as stated is 15%. that goes for if your making 100 hp or 2500 hp. it's just the way it is.

Nitrous03GT · Dec 27, 2008

People like to say 15%...but that is a generalized statement that doesnt take into effect many variables..such as rotational mass, gearing, car weight and such...but honestly what does it matter? its not so much the power that the engine makes, its the power that is effectively put to the wheels as they push the car forward. but if you really wanna know what kind of loss YOUR particular car has and if you want an ACCURATE number, take the motor out of the car and have it engine dynoed, then put it back and do a wheel dyno....but even that isnt that accurate because different dynoes will give you different numbers...so...yea.

5.0Torx · Dec 28, 2008

98COBRA281 said:
i hate when people say a percentage, because its not true at all, so 1000 crank hp, would mean 150hp loss throught the drive train, which is crazy..

thats actually exactly how it works

NitroDuck · Dec 29, 2008

98COBRA281 said:
why would you lose more hp just because you make more power? theres no difference.......

Because the transmission causes an operating loss of roughly 10-15% due to heat & friction. Its not like it arbitrarily saps 30hp no matter what, just "cause it wants to."

LaserSVT · Dec 29, 2008

Yep, everybody is right on with the hp % loss. I have dynod 9-10 or the cars I have owned and two were engine dynod and then chasis dynod. My 94 LT1 Formula lost 21% through its Auto and my 300Z TT lost 16% through its 5 speed.

When I first got into modding it took me a bit to wrap my head around the percentage loss wrather then just a base number but thats how it is

BTW, my Z was making 421 rwhp and 501 fly wheel hp. When the car was stock it did 254 rwhp and they are rated 300 stock. And that was ZERO mods. So it appears the numbers are right

JBVobra · Dec 29, 2008

my 04 cobra dynoed 379rwhp sae. car was rated at 390 crank hp. 2.8% loss?

actually, of all the other cars I've owned and had dynoed showroom stock, the loss was pretty much in the same percentage ballpark:

98 cobra - 264sae/305crank = 13.4%
01 bullitt - 240sae/265crank = 9.4%
02 z06 - 353sae/405crank = 12.8%
06 z06 - 453sae/505crank = 10.3%

the 06 z06 was also under the new, more conservative sae J1349 crank certification that I guess all engines are rated today. so 505 is really conservative for that ls7

the bullitt? don't know on that one....it was just freakishly fast. Dynoed on at least 3 different houston area dynos and just laid the wood everytime. This was one instance where dyno numbers really did equate into street warrior. I use to destroy other gt's and bullitts at HRP. that car was the poster child for factory freak

hotmustang331 · Dec 29, 2008

98COBRA281 said:
i hate when people say a percentage, because its not true at all, so 1000 crank hp, would mean 150hp loss throught the drive train, which is crazy..

manual 30-35hp loss

So if we stuck a 35HP 4 banger engine into your car all you would get is 5RWHP? What happens with a 20HP engine? Are you now in the negative?

Its a PERCENTAGE bro 12-15% on average as others have stated

Purostaff · Dec 29, 2008

Here's my dyno graph: 700 miles on the car 100% stock w/ air silencer removed

So it's about 12-13% loss.. for my case

joshheat25 · Dec 30, 2008

JBVobra said:
my 04 cobra dynoed 379rwhp sae. car was rated at 390 crank hp. 2.8% loss?

lol yea I'd say the 03-04 Cobras are a tad under rated!

It is a percentage of loss! one thing to help is to add a lighter Driveshaft, because it is ligher there is less rotating mass and less energy is needed to rotate it.

EPIK · Dec 30, 2008

I have always heard the same thing about the percentages too. The higher HP #'s the car has, the more power it loses to the wheels, but the percentage is always about the same give or take....

Since my math isnt that great, what do u guys think my hp & tq numbers are @ the crank on my mach that puts out 315rwhp & 327rwtq???

Mach 1's were rated @ 305rwhp & 320rwtq from the factory(IIRC). My car dyno'd 278rwhp & 294rwtq when it had nothing other than an MRT catted H, bassani catback, & C&L maf... What is the crank hp & tq #'s on that also??? Sorry guys, I am horrible @ math....

rwhp loss through the drivetrain

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