With all these dyno pics that i have been looking at from K&N and Comptech... it looks like the "Wheel" horsepower is about 200. So where does the 270 hp come from? Does this mean that the car only has 200 hp available when i'm driving... not the 270 that i expected? This affects competition against other cars doesn't it (like suppose the WHP of the 3 series is 200 even though it has 225 hp vs. the TL's 270)? So am i driving a 200 hp car instead of a 270?

 

The 270 is how much horsepower is being produced at the crank. The car manufacturers get this number from running a the engine alone on a dynamometer. Since it isn't practical to take the engine out of the car everytime you want to check its horsepower people run the car on the dyamometer to check its horsepower at the wheels. The horsepower at the wheels is lower because the drivetrain, transmission and other components steal power before it gets to the wheels.

 

Yes you have 270 hp at the flywheel you lose a percentage of that at the wheels. I don't know what the percentage is. The same thing happens with torque.

 

its usually 15-20% loss for manual transmissions and 20-25% for automatics.

 

You have to realize that the engine makes power (~270hp) As was said before, it takes some horsepower to turn the transmission, the power steering pump, the axles, the air conditioning compressor, et cetera, so the final number at the wheels can be a bit less. Automatic transmissions siphon away more hp than manuals, as well.

When I drove an automatic Camaro Z28, we estimated that the auto took away about 20% of the engine's rated hp, and the manuals roughly 17%, but those were just rules of thumb. My car dynoed 236 hp at the rear wheels for a V8 rated at 285hp, so my car was a little strong from the factory. Figuring 236 was 80% of the engine's output, m car actually kicked out 295 at the engine.
I hope this helps! Gimme some rep points!!

 

Hmm. The 02-05 auto Altimas dyno at 195ish. If an auto TL is dyno'ing at 200, then either the transmission is the worst in the world, or it's not really making 270hp.

 

so this means that if a car has all the exact same NUMBERS as the TL (curb weight, power, etc) it still may beat the TL in the straight because of a different (more efficient, less power-consuming) transmission or various engine components?

 

I'll give you some rep points just for spelling out et cetera.

 

Why do people insist on using a % lost to wheels. This does not make sense. If you unbolt the engine and turn the transmission input shaft it will require a certain force. If you go to the gym and get stronger (you make more crank horsepower) it still requires the same amount of force (no % increase because you got stronger).

The percentages work out simply by coincidence and the fact that higher power/torque motors require heavier/stronger gears.

Having said that, when I had a MK III Toyota Supra Turbo (284 RWHP) I could see a 7 or 8 horsepower increase with shaved racing tires (lighter rotating mass furthest from the axle). Wheel bearings, engine mounts, transmission lubricants, wheel diameter/weight, clutch slip - all these things take power from the engine before it gets to the pavement.

Don

 

According to vtech.net, the 5AT dynoed at 212 WHP on a Dynojet. The 6MT came in at 222. However, it was noted that the 6MT was not quite yet broken in so they expected to find a few more horses. They also mentioned that the 2G TL-S was had 200WHP.

dsc888

 

Man ... I lay down a good explanation and I get no rep points. But this guy gets points for spelling a word!

 

My '94 SHO puts down 182 FWHP. This coming from a car with a 220 crank HP. Why is there so much drivetrain loss in the TL?

BTW 6Mt G35's have been getting 230-233 RWHP numbers

 

Don, the correct way to use that percentage is per vehicle (e.g. the TL has a drivetrain loss fo 15%, the RSX loses 13%. It's incorrect to say "cars lose 15%" because of the varying efficiency of the setups from model to model. However, you can correctly say from your specific experience with different models that automatics tend to use more power than manuals; to quote a percentage should only be from your personal experience.

 

My 01 Maxima ( AE) is rated at 227HP...dyno showed just a little more than 190...so something must be funky with the TL's tranny...

 

Sorry, bro. Points to you too.

 

DITTO!!!!!

 

Understood. I just get sick of someone assuming a 20% driveline loss and reporting an 8 horsepower increase as a 10 horsepower increase because they're adding the factor in again.

IMHO, if you dyno x horsepower and a mod gives x + 10 horsepower; you just gained 10 RWHP and 10 Crank horsepower.

Don

 

The bottom line is regardless of what your marketed crank Horsepower numbers are, What really counts is how much horsepower is at the wheels.

When People ask me how much Horsepower my car has, I quote them Wheel horsepower. When they reply by saying oh my car has X amount of HP which I well know is a crank figure, I just smile and nod.

 

This is actually reassuring. I hadn't seen any dyno numbers whatsoever, and was quoting someone above who mentioned 190.

I sure wish I'd gotten a manual though..

 

I am just curious? Does BMW rate HP diffrent than ACURA. My dad has a 530 and my bro has a 330 and both say that just becasue they say I think 222hp that it is true HP unlike my TL??? Sorry love the car but know nothing about all this dyno stuff.

Thanks!!!

 

The HP numbers that manufacturers quote in the marketing in my experience as just that, marketing. These numbers play a very important role in the overall marketing and market segment placement of a new vehicle.

Using a dynometer to genericly quote that X vehicle makes Y power is flawed as well. The dynometer is an accurate tool when used to determine that X vehicles made Y power on a said dynometer. This data could also be used to compare power output of two like vehicles on a given dynometer with the same conditions or the lost/gain of power of a said vehicle after performance tuning.

The peak HP numbers that almost everyone uses to quote is a useless number in the rear world. The power curve of the HP and torque is much more important compared to the peak number and it's rare this information is presented.

The point really is I wouldn't worry too much about these numbers unless you're buidling and tuning a drivetrain all that really should matter is what your butt-dyno tells you.

 

They are not supposed to be rated differently, but the fact remains that BMW horses "seem" stronger than other manufacturers. For example, a 330ci can run 0-60 in 5.6 seconds, almost neck and neck with a TL 6spd and a G coupe 6spd?

Some manufacturers also underrate the hp ratings (i.e. the G sedan which is rated at 260 hp, but is probably making close to 280 hp like the coupe).

I agree with one of the above posters that wheel hp is the more relevant when comparing what two cars put down but even that figure can be affected by the weather, the number of runs, the type of dyno, etc. etc.

In the end, I put trust in my butt-o-meter. It sure as hell is not accurate, but it makes me feel better.

 

Dyno's should ONLY be treated as tuning devices. They are not the standard as far as performance or power is concerned. The dyno should be used to see relative improvements in power gains when mods are done, and to make sure the a/f ratio is within the correct parameters.

As a side note, my CL-S 6 speed made 218whp/206wtq, which is a 17% loss in hp, but only a 12% loss of torque. Since hp is simply a function of torque this isnt technically possible. Each car losses a certain amount of hp specific to that car only. Another CL-S6 exactly like mine may put down 215whp or 225whp, its just the law of averages. Engineering these days makes for more consistent power #'s, but that doesnt mean that every car makes exactly 270hp at the crank.

Just get some track times and then you'll know if your car is fast enough.

 

I have seen a figure of 229 HP at the wheels for an '04 TL. This would seem to be just about right when you factor in the "standard" 15% drive train loss for a front driver.