Drivetrain losses?

[68corvette]

Hi.

There is much arguing about drivetrain losses.
How much have you seen betveen motor / rear wheels.

I'm mostly interrtested about street gears like Munchie, T5, TH350, TH700, T4 etc. and gera ratios near 3.5:1.

Some people say that they can losta something like 35% with stock TH350 + stock converter and some dynos calculate as low parastatic losses as 10% or lower..

what have you seen?

[shawn]

I seem to remember a test that superflow did a few years back where they had a big chev and dyno'd it on one of their dyno's then put it in a super gas car to see what the actual difference was. If my memory is correct it was a turbo 400 with 9inch rear and on a 700 hp motor they lost 140 hp at the tires. You could probably call them and they could give more detail on it.
Shawn

[kdrolt]

www.sae.org

Search through their publications. There are many items having to do with drivetrain, or powertrain, loss.

Each document cost $$ so it's helpful to use the SAE search tool and then visit a nearby college library to read the article. HTH.

[jacksoni]

I think you have to consider that every car and every dyno will give somewhat different numbers. Most reports I have seen suggest 15% for a manual and 20% for an automatic. That 140 out of a 700hp engine auto trans =20%. But is really someones guess most of the time. Above gets you ball park.

[ClassKing]

For what it's worth - the Pontiac 350 that was in Car Craft lost 118 hp going from Westechs Superflow dyno to Westechs new Superflow chassis dyno. That was a T400 and a nine inch.

[SupStk]

I had my first experience with a dyno many years ago. When I was in school they had an old Clayton rear wheel dyno. After beating my brains out trying to observe a power increase by jetting, timing ect. the instructor pumped the rear tires to 50PSI. Presto instant HP. But to answer your question about drivetrain losses..... I don't have a clue.

[Ron E]

I know there has always been talk about the 9 inch and it's low pinon location soaking up more power. I wonder if it's ever been measured against a 12-bolt or any with a higher pinon? Is this one of those theory points (like rod/stroke ratios) where the only measurable energy waisted is from arguing about it.

[MadBill]

Someone builds a Ford 9" pumpkin that takes GM 12 bolt gears, claims 1-2% better efficiency, as I recall.

[hsutton]

Someone builds a Ford 9" pumpkin that takes GM 12 bolt gears, claims 1-2% better efficiency, as I recall.

That's an easy one. Strange Engineering makes a drop out 12 bolt center section for the Ford 9" but then your back to having basically a stock 12 Bolt. You lose the best 9" feature which is the pinion being supported on both ends which stops the gears from spreading under extreme loads. This is the primary reason the 12 bolt breaks the ring gear & pinion gears in the first place. The Dana 60 is also quite a bit stronger than a twelve bolt and is supposedly more efficient but every car that i ever saw try one slowed down about 1 1/2 tenths. My sons 9" has been dead reliable for about 10 years of constant quarter mile action with engines ranging from 500 H.P. up to the monster he has in it now that has over 1100 H.P.

[Ron E]

Someone builds a Ford 9" pumpkin that takes GM 12 bolt gears, claims 1-2% better efficiency, as I recall.

That's an easy one. Strange Engineering makes a drop out 12 bolt center section for the Ford 9" but then your back to having basically a stock 12 Bolt. You lose the best 9" feature which is the pinion being supported on both ends which stops the gears from spreading under extreme loads. This is the primary reason the 12 bolt breaks the ring gear & pinion gears in the first place. The Dana 60 is also quite a bit stronger than a twelve bolt and is supposedly more efficient but every car that i ever saw try one slowed down about 1 1/2 tenths. My sons 9" has been dead reliable for about 10 years of constant quarter mile action with engines ranging from 500 H.P. up to the monster he has in it now that has over 1100 H.P.

I do know of a well flogged S/S car that made the change from a Dana to a 9". He had to add the bit of weight difference back. The net change in ET was nothing. So, it seems a 9" gives up little if any REAL efficiency to a Dana.But,that Dana loss of .1-.15 seems severe with no other changes. I wonder why such a loss in the ones you observed...maybe unsprung weight was a critical factor?

[prochamp]

as far as going from 12 bolt to dana goes i would think you would lose alot of et due to rotating weight(alot heavier components).i think as far as the 9 inch goes i wonder if the location of the pinion would soak up some power much like helical gears do compared to straight cut gears in a transmission.

[Ron E]

Yea, I can see a Dana losing some ET compared to a 12 bolt, or 8-3/4 mopar. And, maybe the extra mass of the Dana and the geometric problems with a 9" equal them out. But, if they leave a tenth, or more on the table, I'd think it would be exploited by any class that can, even with high upkeep, get by with a different rear end. And, do 'cup cars maintain OE geometry with 9" rears? There is no way they will give up such a loss to a rear end.

[Cobra]

Simply put: Manual transmissions will absorb 15%-17% of engine horsepower and automatic transmissions will absorb 20%-25%. Let's examine this a little deeper without making this an engineering treatise. Horsepower loss is directly related to rotating mass and frictional losses. Many Gm racers use 200 size automatics over 400 size to minimize loss caused by heavier parts in the 400. Torque converter slip absorbs horsepower, which is why many car makers switched to lockup converters. Manual transmissions typically have less rotating mass and friction than automatic transmissions. The lesson is: Minimize rotating weight and friction in your drivetrain while maintaining parts capable of handling the weight and horsepower of your combination. Add horsepower to your car and drivetrain losses will increase as well.