SAE Driveline Power loss

[Fultz1275]

Can anyone definitively tell me what the SAE (industry standard) drivetrain power loss for both a manual and Automatic transmission setup.

I have heard the following:
Manual - 12-20%
Automatic - 15-25%

The reason I ask is because I just erertia chassis dyno'ed my car and it put down 327 hp and 366 tq on a DynoJet. That means that there would have had to of been 50% driveline loss to see the target flywheel hp of 500. NOT POSSIBLE, in my opinion.

I told my engine builder that my target HP at the motor was 500. He guarenteed that we were between 475-500 when the motor was done. Now that I showed him the dyno sheet, he is saying that he has seen as much as 45% drivetrain loss. I think this is complete BS. Espically considering that my entire drive line is brand new and inculdes new 12 bolt, new aluminum driveshaft, and TKO 5-speed. I have been told by many other people that with my setup I should expect between 12-15% loss.

Does anyone have any SAE specs that talk about industry accepted driveline losses so I can bury this jack-a$$

[Madspeed]

First off your eng builder is full of crap.
Second off... what is the COMPLETE engine combo and I can tell you what it would make within 30 hp. I must have a cam grind number and make..

500hp at the crank is gonna need some pertty good flowing heads with Efficient chambers,
a single plane intake, with a rather large carb, A roller cam will help a lot...
Youd get better results with a 383 cid or larger and 10.5 or more comp....

I just built a 383 w 9.8:1 comp 6 inch rods edelbrock performer rpm heads with a perf rpm intake comp cams 240 246 @ .050 507 510 lift hyd flat tap cam and this combo makes 390 hp 390 roughly IICR

with a victor intake a roller cam and some port massaging (or diff heads) I can get just shy of 500 hp.

GL Ken F @ MAdspeed

[ProdigyCustoms]

Well, you do not say what your enginge combo is, so it makes it difficult to determine wheater this looks right or not. But you are asking about specific drivetrain loss. I can tell you this as a fact. In just the last couple weeks we have had the chance to engine dyno, then imediatly chassis dyno cars. And twice now I watched 3 different 602 /634 / 620 FWHP combinations make 414 / 400 / 440 RWHP. And 2 of these cars are manual transmission cars.

One of them, the 602 FWHP / 414 RWHP is my street racer which runs consistant 10.70s @ 126MPH @ 3450LBS, which is said to take 600 FWHP to do. So I would not sweat the numbers just yet.

What is your exact combo?

Also, you are not lookig at a 50% loss. It is about a 30% to 35% loss, which probably does not make you feel any better.

[rohrt]

One of the car magazines did a article on drive train loss. All I remember was it was not uncommon to loose 100hp through the drive train. A Th400 tranny and a ford 9" robbed the most hp. A manual tranny with a gm 8.5 took less hp.

[67ragtp]

Not to steal the thread, but I have a question for Frank, how many mph does your car pick up between the 1/8 and the 1/4? Is it automatic or clutch and what kind of 60ft times are you getting?

The reason I ask is my 67 camaro ragtop(540cuin.) runs right around 126mph but I cant seem to hook the car since it is a 4 speed. the 60s are 1.8seconds but the strange thing is I pick up 30 to 32 mph From the 1/8 to the 1/4. Im a bit puzzled with whats hapening at the top end in relation to how much power the motor is making.

Thanks Rich

[ProdigyCustoms]

My street racer is considered a strong finisher and picks up 25MPH on motor and spray. Assuming the track is on the money, On the motor, depending on density altitude, the street racer will run 100 to 102 MPH in the 1/8th and finish 25 to 25.5 more MPH out the door. This 25 MPH is considered the upper end of MPH gain in this level of car. Super stockers that cut incredible short times for their given ET with loose converters do not pick up nearly as much.

For what it is worth, no matter what amount of spray I hit it with, the MPH picks up the same 25MPH. So the for,ula seems to work deep into the 9s, the highest ticket example I have seen was 121MPH with a 146MPH out the door.

The car is a TH350 conventional automatic (to reverse valve body), 8" super tight ATI converter, 4.10 12 bolt with 29" tires. Short times on motor when the track is real tight will be in the 1.48 range on motor, 1.32s on the giggle.

Assuming you are on some type of hooking tire, I would consider a looser converter to shoch the drivetrain and plant the tire. it would seem you converter it tight based on the MPH gain. of coarse some of that comes from no hooking. What are the ETs? 11.40s or so? The 126MPH says it has the horsepower to run 10.90s in decent air.

[67ragtp]

Yes frank, 11.40s the only problem with your solution is the car is a clutch - 4speed. I imagine it would run similar times to yours if I went with an auto trans. So if I got the car to hook in the 1.6s the 1/8 mph would be a little higher and the amount of mph between the 1/8 and the 1/4 would probably drop a bit. I run hoosier QTPs 28 tallx13 widex15 rim, If I launch the car anything over 3200 rpms it blows the tires off. I run caltracs and the ranchos are set on 5, it just dosent seem to transfer the weight quick enough when launching. Thanks for the info on your car- Rich

[ProdigyCustoms]

4 Speed. See, I knew it was tight, LOL! Yeah, if you pick up .20 to .30 up front, you will gain .4 to .60 out the dorr, and cut that second half MPH.

[MuscleRodz]

I dyno'd my 97 Crew Chev Dually with 454/4L80E/4.10 rear and had 25%torque and 33%hp driveline loss. Published hp was 300 and had 200, torque was 400 and 300. I can't see a vehicle having anymore driveline loss than this truck. I have heard different dyno's will also give different results. Mine was done on a Mustang dyno.

Mike

[68sixspeed]

My old motor did 530hp on the engine dyno (flywheel); 435hp on an electromagentic (mustang) chassis dyno, 17% loss, with a ford 9" rear and with the tranny in 3rd to keep the wheel speed down. I think we could have hit 450 at the tires if it was in 1:1 (gain another 2% anyway) But Frank has a good point, his actually chassis dyno'd low probably due to the tranny and torque converter, but the 1/4 mile dyno (trap speed and slide chart) does not lie on flywheel hp- the only corrections needed on the slide chart are for altitude/weather. -Dan

[MuscleRodz]

Question: Do you know if they dyno'd in 4th or 5th gear. If they did it in overdrive, which they shouldn't of, it will give a false reading.

Mike