Just curious as to how much HP is lost in the drivetrain?

 

11% I believe

 

TTT

 

20%
You add 20% to the RWHP to come up with the flywheel HP.

 

I dont think it's 20%. I thought it was around 11-15% only...
Shane

 

Divide rear wheel HP by .80 to determine engine HP- Kenne Bell

 

Negative.........

11-12% according to Gregg..........I trust his numbers since he actually is referring to our transmissions and not just using a general assumption like Kenne Bell is.

--Joe

 

I don't understand why it is always quoted as a percentage. If you double your engine's HP does that mean you now doubled the power loss through the drivetrain? If so, WHY?

 

Dirt bike,

In a word...yes but there are some caveats.

Let's take an engine that makes 250 true flywheel horsepower (using nice round numbers and assuming that all of the numbers are accurate, regardless of how they were measured). Let's look at two scenarios with 11% and 18% drivetrain losses.

With 11% you would see 222.5hp at the rear wheels for a loss of 27.5hp. With 18% you would see 205hp at the rear wheels for a loss of 45hp.

Now let's double the power that the engine makes and say it is now 500 true flywheel horsepower.

With 11% drivetrain loss now you would see 445hp at the rear wheels for a 55hp loss or double the amount of power that you lost when the engine had 250 true flywheel horsepower. With 18% you would see 410hp for a loss of 90hp or double the loss that the motor had when it only had 250hp.

It's simple math really...10% of 100 is 10. Now double that and 10% of 200 is 20. You're doubling the power, which means that you are also doubling the power lost with some exceptions...

In a perfect world, the drivetrain loss would always be a constant value. This may not actually be the case though, as the drivetrain losses may marginally drop at higher horsepower levels although not by a significant amount. So, for argument's sake with the assumption that drivetrain losses are constant regardless of power levels, than the answer to your question is yes.

 

Gregg said the trans absorbs around 11% (mostly due to the converter driving the pump), but the total drivetrain loss is greater than just the power robbed from the trans. You still have to spin the driveshaft, turn the ring and pinion, make a 90 degree turn (causing more friction) and spin the axles, rotors and wheel/tire. 20% seems to be a good estimate.

The percentage rule of thumb gets you in the ball park, but I believe it only takes a specific amount of horsepower to move a certain component. For example, it takes X amount of power to spin a 15lb driveshaft at 4k rpm and Y amount of power to spin at 9k rpm. Weather there's a 100hp engine or 1000hp engine spinning the driveshaft, it still causes the same resistance. Of course it would be very difficult to go through every component in the drivetrain from the converter to the asphalt and test how much power it takes to move, so we use a rough percentage that gets in the ball park for most cars. Results may vary.

 

HI!... This has been discussed over and over again. MIKE TROYER and SUPERCHIPS have already proven on SUPERCHIPS "EDDY" current dyno that a stock LIGHTNING with the 4R100 tranny loses 69-70H.P through the drivetrain. Other F-150's with the 4R70W tranny are losing 65H.P. Don't go by the baseline #'s the non accurate DYNOJET dyo's give you and less their "EDDY" current. Mike's seen bone stock (360H.P) "99"-"2000" LIGHTNINGS put doen over 330RWH.P on a DYNOJET and then run the same truck on SUPERCHIP's DYNO and it only makes 290-295RWH.P.

 

sponsered by superchips now?

 

The only number that is important to me is RWHP.

A better question may be how can I lessen drivetrain loss?

Manual Transmission. Don't want to do that in my lightning.

Synthetic Fluids in the rear end. That would be worth a test.

Posi without the limited slip. Seems too much for a daily driver.

any other choices to lessen the drivetrain loss.

 

HI!... PhillipSVT : Actually MIKE does sponser my truck. You got a problem with that? With the arrangment MIKE and I have had over the last 4.5 years, I hear info you would only wish you could hear. Mike shoots from the hip without all the B/S the other tuners get into.

 

first of all, maybe there is some history here that I don't know about, but it seems like you are being a little defensive?

aside from that, are you saying that the "eddy current" style dyno produces more accurate numbers than a dynojet?

if so then how exactly do you know this? I'm not attacking, just curious. I have wondered for some time now why the different dynos produce different numbers. well, I know WHY, because they use different methods to measure, but I wonder which one is correct. it's got to be one or the other.

a neighbor and friend of mine is about to purchase a dynojet to put in his shop where I do some work. we looked at a few different dyno's a SEMA. basically we settled on the dynojet because it is the most popular and we felt like it is the one that most people prefer to use.

of course most people prefer it because it produces higher numbers and because it seems to be the most widely recognized brand (this allows people more accurate comparisons with other enthusiasts numbers).

I haven't seen any proof to verify that one dyno is correct or more accurate than the other. but obviously only one of them can be correct.

as far as drivetrain loss, just using a different kind of dyno doesn't prove anything. you'd actually need to test the engine on an engine dyno and then install it into a truck and retest it on a chassis dyno to determine drivetrain loss.

which of course brings us back to WHICH chassis dyno?

later,
chris

P.S. I have always said that Gregg's 11% number is BS. just my .02 though.