Holy post resurrection batman. Well 37% would mean I make 634fly wheel horse power LOL! I seriously doubt that. My trap speed is a much better indicator, which is about 121 and when I enter it into the mighty power calculator based on 3400 pounds including myself I get 550 hp. That would mean I lose 150 hp to the driveline according to the DD soooo that means 150/550 = 27%. That sounds at least a little more realistic.

 

It was an unwritten agreement. It was something that was simply understood, although they (the Japanese manufacturers) have cast it aside, and are now posting the true hp ratings of their cars, and actively trying to build more powerful cars.

Look at any late 90's/early 2000's Japanese performance car... Evo V, VI, VIII; Toyota Supra TT; the later Subaru WRX Sti; Nissan Skyline GT-R (R32, R33, R34)... all of these cars posted the same horsepower: 276hp (280ps). The most telling was the R34 Skyline... with the "same" horsepower and more weight, it was faster than the R33.

Basically, these manufacturers were underrating their power outputs to keep to the agreement.

 

What the percent of loss compared to a dynojet to mustang dynamometer?

 

Sure, here ya go...

 

20% is FAR more realistic than the 37% number that has been bandied about. If the driveline losses were that great, the drivetrain would be so inefficient that it couldn't help but have the fuel economy of a Hummer.


The 550hp estimate is inflated. EVOs are getting to that trap speed on the factory turbo, which cannot deliver nearly enough air to generate that much power. EVOs that register 370whp on a DJ (which gives liberal readings) are seeing trap speeds of 117. Plugging 121mph and 3400lbs into a calculator I referenced yields 470hp, which is much more believable.

I believe the true drivetrain loss figure to be around 20%. Furthermore, if the losses were as significant as 27-37%, we would be seeing injectors running out of steam far earlier than calculated, and this is not happening. Think about it.

 

lol, Wednesday motor!!!!

 

I I am just telling you what the calculator pushed out for 121 mph and 3400 pounds. Was that 470 hp crank or whp? the 550 I referenced was crank. To hit 10.9 I am pretty sure you would at least have to put out 550 and that has been done on the stock turbo. You just crank the boost up and pray your turbo doesnt blow up.

Oh and assuming my power loss is a constant which it isn't then stock my car dynos 215 on that dyno and it made 190 more hp. Right there 55/270 = 20.3 % at stock levels. So add 190 to 270 and you get 460 and that is assuming power loss stays constant from stock power to over 400 hp.

Now lets assume it's a percentage as everybody wants to advertise. Now even at a low percent like 20% you take 20% of that extra 190 hp I am making and add that onto that 460 number and wala you get the crank assuming your power loss which is right about 500 even.

 

My point was that hp estimators provide a rough estimate at best, so the results obtained from them cannot be assumed as gospel.

A stock turbo car running 10.9 more than likely doesn't weigh in at 3400lbs (which throws that hp calculation off). Weight reduction is no secret and is common practice.

I see your point regarding drivetrain losses, and no one can assume that the rate of drivetrain loss to be a constant, simply because the mass of the drivetrain is a constant. In fact, drivetrain losses may not even reach as much as 20% at any significant point in the power curve even at the stock power level. For example, an 18% average at the 271hp yields an indicated ~230whp (sounds familiar?), and that percentage almost certainly becomes markedly reduced as the power increases. This implies that as power is increased, the difference between the indicated whp figure and actual crank bhp becomes progressively smaller.

What this means in real world terms is that even if we knew the actual drivetrain losses (best calculated on a stock car because we have a good idea of the cank bhp), this percentage cannot be accurately applied once we change the engine's power, simply because the only change in the power it takes to turn the drivetrain is the additional power needed to accelerate the reciprocating parts of the drivetrain in less time as a result of the increased engine power.

 

I think your oversimplifying on drivetrain loss I can almost gaurantee it's not constant no matter the power you make. How else could 800whp cars be claiming over 1000 to the crank. And BTW 205-215 is more like it on a DD I am not talking about the glory dyno (dynojet). On that dyno I would be over 450 whp.

 

I don't see where I'm oversimplifying anything, and I'm not saying it is constant. What I am asserting is that the actual losses almost certainly do not increase at a rate that matches a constant percentage of overall power production.

Regardless of engine power, it requires the same amount of power to turn the drivetrain any static speed. Therefore, if the drivetrain absorbs 20hp at 60mph in 5th, whether the engine is 100hp or 1000hp, it's a constant 20hp loss. No difference there.

What changes where drivetrain losses are concerned amounts to the difference in power required to accelerate the reciprocating assemblies (e.g. tranny, diffs, wheels) at a faster rate. This specifically refers to the effort required to turning the tranny, diffs, wheels, etc. more or less in free space (i.e. independent of vehicle load - which is remains unchanged).

Claiming an 800hp car makes over 1000hp at the crank essentially claims that if one were to put that car on a lift and spin the wheels in the air, it would require a 200+hp engine to rev the engine through the gears at roughly the same rate as the 800hp car accelerates on the road. If that number seems excessive, it should.

Finally, where dynos are concerned, an independent test demonstrated a Mustang dyno to be perhaps the most accurate where actual wheel hp is calculated. As you know, the DJs give numbers that please the ego, while DD numbers appear to be conservative (albeit consistent). Mustang numbers fall somewhere between the two.

 

Additional power also will put additional fictional losses into play. more power applied through the gear sets increases the side loading on bearings holding the shafts becuase we have bevel tooth gearsets, not strait cut gearsets. same in the front diff and rear diff.

This would be pretty minor imho, but should contribute to increasing drivetrain loss with increasing power.

 

ok i will say this just like everyone else is, 37% is a huge amount of loss. the only way u could measure drivetrain loss is if u dynoed your engine to the crank then put it back in and dynoed it in the car. that will give u the difference and the percentage. now who here has actually done that? from what i have expierenced and herd, about 23-25% loss for an awd is about as close as u can get. not only that but every cars' drivetrain will be different so there is only one way to tell, and its what i said above.

 

I agree with your above statement, we just weren't on the same page initially.

 

got you covered...

 

Damn those 05s put out a lot stock.

I went to the same company ill be damned

Here is the difference between 18 psi and 27 psi on a gt35r.

Before my turbo upgrade and cams my number was 271whp.