Took my car to the dyno for some base numbers before I tore it down. I made right at 240 RWHP. My goal is to make around 400 RWHP. I plan to build the motor, but was also interested in ways that I can reduce drive line loss. I know autos suck up more HP, but is there a better trans, rear axle or both I can install to help reduce loss. I would like to stay with an auto. Below is the set up I have now.


425 BBO Toro, TH400, 10 bolt 8.5 posi rear with 3.73s

 

How did you calculate the crank HP at 410?

Were the numbers you used for those calculations accurately measured?

What sort of formula did you use for the calculations?

- Eric

 

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Others know more about this than I do, but that sounds wrong based on my knowledge of physics.

If anything, it would seem to mean that you only had 170HP at the wheels .

- Eric

 

Agreed

 

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Tough. This is the internet. I have no idea what the answer to your question is, and nobody else is coming up with anything right now, either. I'd be interested in hearing their answers if they were to respond.

What I can say is this: The consensus seems to be that there is less loss through a TH350 than a TH400, though a 350 has to be built heavier to take as much torque as a 400 can. Obviously, a manual has fewer losses than that.

I have never heard of any particular rear losing less power than any other, though I am sure that there is some variation at the extremes (super-heavy-duty vs super-light-duty).

I am still concerned about the driveline loss calculation.
Logically, power used to brake the drivetrain in neutral will measure drivetrain inertia, and not drivetrain resistance, which would actually make it slow down faster.

- Eric

 

Is this better? I took out the confusing stuff. Any discussion on a new set up would be appreciated. You can start a new thread on how dynos work somewhere else.

 

Test any three dynos and you'll get three different readings for the same engine. That's just the way they are. I've seen losses from 10% to 40% between an engine dyno and a chassis dyno but then again it depends on the dyno. Not to say one is wrong or different than the other it's just the way it is.

As far as drive line drag, friction, HP absorption or what ever you want to call it some parts are more efficient than others. A TH400 will eat up more HP than a TH350 because of the heavier internals but the numbers aren't huge, maybe 10 HP. A 12 bolt Chevorolet rear end is more efficient than a 9" Ford due to the height of the pinion gear but obviously not as strong. The Dana 60 falls in between the two if I remember right as far as efficiency but is the strongest of them all and heaviest.

I would shoot for a loss of 25-30% as probably an average figure. With that in mind you'd need about 600 HP at the flywheel to get 400 HP to the wheels. This isn't hard science it's a best guess.

I can't comment on manual transmissions

 

But you really shouldn't estimate the drivetrain losses as a percentage. The losses will be pretty much a constant, fixed number regardless of whether you put an 800 HP race engine or a Briggs and Stratton in front of it.

Timmy T,
Since people who are interested in increasing horsepower (aren't we all?) typically want to do so for purposes of acceleration, not stump pulling, you should be as concerned with inertial drivetrain losses as with static losses. It takes a lot of horsepower to accelerated any part that rotates. You can increase the horsepower applied to the ground by making every rotating component lighter. We're talking parts inside the engine, inside the transmission, the driveshaft, the axles, and the wheels. Of course, as they get lighter, they have to remain strong (or even stronger). If you're serious about this, look into all the companies which cater to serious drag racers.

There was a previous comment about losses in one rear end vs another. I've read that the geometry of pinion and ring gears used in the GM rear ends inherently has less loss than that used in a Ford 9", for what it's worth.

 

A good article on 12 bolt vs 9" from Car Craft:

http://www.carcraft.com/techarticles...ord/index.html

 

I've heard that the Ford 9" takes more HP to turn than a GM rear, however the Ford 9" is a really good rear.

You're looking at 20% drive line loss. Accpet it

 

Except, in his pre-deleted post, he was talking about having 41% driveline losses, which is 1½ to 2 times more than the generally-accepted 20-30%.

It's hard to build for a specific rear-wheel HP goal (in this case, 400HP) when you don't know exactly how much power you're losing between the flywheel and the rear wheels.

In this particular case, the entire thread (pre-deletion) was based on the premise that the chassis dyno measured 240 RWHP, then measured "170HP" to brake the rolling wheels to a stop in neutral, and that that 170HP represented an accurate measurement of driveline losses, yielding a flywheel HP of 410. The OP is planning a rebuild, and wants to know how to reduce driveline losses, at least in part because the driveline loss model he presented puts him in the position of having to build a 564HP engine in order to reach his goal of 400RWHP.

If we had a better idea of what ACTUAL non-inertial losses were in the driveline, we would be in a better position to help, but, as I have observed in the past, other than having some vague idea of losses through different transmissions (I've seen a variety of values posted, with no objective sources to back them up), it doesn't look like anyone really knows (which is reasonable, because how many of us does a dyno pull, changes out the trans., then does another one?).

Meanwhile, the OP will be chasing after 170HP worth of driveline losses that he may not have in the first place.

- Eric

 

Yes, I deleted my original thread and re-wrote it. I thought by doing this you might stop trolling on this thread, but I guess I was wrong. I don't ultimately care what precent loss I have, I'm asking for suggestions on how to reduce it....aluminum driveshaft, disc brakes, electric fans, electric water pump, different trans. Unless you have some suggestion to make please go the **** away!!

 

Wow, ok I'll try. Lose rotational mass and friction. The less the better. There is no one answer to this. Every car and set up is different. No one can tell you that 'X' transmission, drive shaft, rear end or what have you is going to lose a specific amount of power and give you a definitive answer. It doesn't work that way. Any given day will give you a different variable every time. Even two exact engines off an assembly line are not the same. Blueprinting them will get you close. You want black and white in a gray world. People are trying to help you with an answer and you aren't listening. Don't know what more you want.

 

Yes, with my 2,615 posts to your seven, I am clearly a troll.

I'm trying to help you here, by clarifying exactly what you want or need, and trying to correct what I believe to be inaccurate information.

This thread has been up for over 48 hours now, and has had a number of responses, all trying to help, but none which has provided the information you're looking for.
Maybe someone will pop up with the right answers soon.

Also, an aluminum driveshaft will reduce inertial resistance, but will not affect power transmission - two different things, disk brakes have more rolling resistance than drum brakes, and electric accessories may reduce load slightly, but in the end, the energy for the work that they do has to come from your engine, unless you run them from a battery and charge it when you get home.

And please watch your ******* language.

- Eric

 

http://maximumperformance.biz/dyno_detailed.htm

Read this and specifically the last paragraph, kinda sums up where I was going with this.

 

Thanks, George. Saves me from going into the "Inertia vs Power" diatribe that's been brewing in my diseased mind.

- Eric

 

Lol, I hear ya Eric. I had a whole diatribe planned but this was easier on so many levels. Buddy must have been reading my mind. I'm glad I stopped by there today

 

http://www.popularhotrodding.com/tec...nos/index.html

Another great article on dynos, engine and chassis.