Is there any way to calcualte friction loss without dynoing the motor, then dyno the car and get the difference?

Are aftermarket parts, even is they are beefier, less prone to loose power?

I have a T-56, then an Aluminum driveshaft, into a Moser 12 bolt.

Is there anyone out there with a similar set up that can tell me how much HP/TQ I will loose at the wheels.

My motor is a soon to be done 383 500 HP screamer that will make power from 3500-to 7000 RPM. I am kinda nuts and am gonna be running this on the street all the time. The car will be babied 90% of the time. I wannna see how close I can get to 500 HP at the wheels. I also have a hitman system that can help me out.

Thanks guys.

 

There is absolutely no way to "calculate" that. There are far too many differences from one setup tp another. Things like how tight the bearings are set up, the gear ratios (and the teeth friction that results), the fluid used, driveshaft angles, etc. etc. etc. all will affect the losses.

The aluminum driveshaft has no effect, by itself. It will make a car read higher on a DynoJet dyno, however; the dyno measures how fast the car accelerates the rollers, so decreasing the rotating moment of inertia affects the reading, even though if you were using a steady-state dyno such as a water brake or an electrical generator type, there would be no difference.

A 12-bolt has higher losses than a 10-bolt, and the T-56 has higher losses than a T-5. Lower than an auto though, I would expect.

I had a friend who had a chassis dyno (Mustang .... accurate), and one of his friends had an engine dyno (DynoFlo ... water brake). They had a number of friends in common that would get their motors dyno'ed at the one place, then put them in their cars (asphalt circle-track racers; not high-loss street cars) and bring them to the chassis place. He said that the lowest difference between the 2 that he ever saw, was about 22%. More typically it was around 28% difference for stick cars and as high as 35% difference for auto cars. Now mind you, that's the difference between the 2 readings, which is not necessarily the same thing as "loss"; but that should give you an idea of the variability involved.

He also described how 2 people would take motors with nearly the same power on the chassis dyno, put them into 2 more or less identical cars prepped for the same class of racing, and come up with wheel readings that were 10% or more different. His specialty, as far as his friends were concerned, was finding where those missing HP went. He found them in too-thick lubes (very common in novice street "racers", hallucinating that they need 50 weight motor oil and 85W-140 gear oil), u-joints that had too much angle, gears and bearings set up too tight, "drop-base" breathers whose lids were too close to the carb air horns (very very common power killer in street cars), and a plethora of other lack of optimization.

Keep in mind, that there are 3 main factors causing those readings to be different. One, is power-dependent losses. Gear friction is in this class: gears have very little loss when transmitting no power, but the losses go up in proportion to the power they are transmitting (and are therefore pretty much a % type loss). Another, is bearing losses, and fluid losses: to spin a shaft in a bearing, or to sling some fluid around, it doesn't matter very much what the power being transmitted is, so those are just a fixed loss. And finally, there are things that are totally unrelated to the drive train itself, but are simply "different" between an engine dyno and a car: like, an alternator, exhaust system, air intake system, water pump, and so forth.

Bottom line is, if you want 500 HP at the wheels to spank off over, you need to be shooting for at least 650 HP at the flywheel at the engine shop; and then you need to make sure you get every one of those you can to still be there even after you put the motor in a car; and then make sure you get as many of them to the wheels.

 

Good to hear someone that has experience in this. I am aware of all those "typical" losses that you mentioned. I also understand and have understood the things that have to do with % loss as power goes up and such. Nothin' new yet.

What I guess I am mainly lookin' for are testimonials of guys dynoing their motors and then dynoing their cars.

I guess I will just use 22% loss for now.

By the way stuff like....... Bottom line is, if you want 500 HP at the wheels to spank off over, you need........is just not needed.
Why try and make someone's goals sound stupid?

 

About 99% of the time, when somebody says something like that ("I'm gonna put a twin-turbo ZZ572 and a Jericho and a ford 9" in my 91 Firebird V6 so I can beat the kid next door's Honda") it's just that.... spank-off.

It's all numbers. A small motor like a 383 that will do 650 HP at the crank is not a trivial matter. Consider that a high-compression 383 will do around 500 ft-lbs of peak torque, and HP = torque x RPM / 5252. That means that to make 650 HP, it needs to be making that 500 ft-lbs at around 6900 RPM. (since 500 ft-lbs * 6900 RPM / 5252 = 656.9 HP); and in general, people who are prepared to build AND DRIVE AND MAINTAIN a motor that will produce that kind of power at that kind of RPM reliably (ON THE STREET ALL THE TIME, aren't posting on these boards asking how to do it. They also understand clearly that a motor that will do that, will be making about 100 foot-lbs at 3500 RPM if it's lucky, and won't be making 80% of peak torque (i.e. into its usable power band) until 5000 or 5500 or the like. Now using nitrous or a blower or something, is a whole other matter; but for N/A, that's how the numbers work out. But of course you knew all that.

So I don't want to come across like a jerk or whatever, all I do is call em as I see em.

 

I DID know that allready. But I am not realy looking for 650HP at the crank. Someday I would like to get a motor that can do taht but for now I AM having a forged 383 built to make 500 HP at the crank. And for that it is not too hard to do.

I guess I learn a new TGO lingo word everyday. (spank)


I do plan on driving this car a lot, but not ALL the time. No winters, and only the nice days for the rest of the year as long as it is not a long trip.

I am not racing people all the time or anything, it is just gonna be a car to drive around, and it is gonna be kinda out of the ordinary to have a motor like mine on the street very frequently.

I was just cuiouse about the friction loss, not to take the info I learn here and apply it, just curiouse. My engine builder (thebigwelsh) is the one who knows all about the " trivialness" about making that kinda power. I am also going to have the spray in there. Mostly just for fun, if i go to the track, and I got it cheap.

 

A N/A 500HP at the crank 383 is a whole lot more practical than a 500 HP at the wheels one, that's for sure. And probably still plenty fast enough to put a smile on your face. So whoever that is that's doing the work for you, at least has a manageable goal to shoot for.

It's a sort of exponential curve, you might say, of practicality vs power, as the power goes up. To get a motor to 1 HP per cu. in. isn't too tough. 1.1 HP is a little tougher. 1.25 HP is REALLY tough, and still have it "streetable" (and I'm not talking about an exclusive Sat night boulevard killer... I'm talking about drive it to work every day type of street use). 1.5 HP per cu. in. is, well, in a whole different league. That's higly unlikely to run on pump gas at all, and even more unlikely to survive for very long in between major failures, in daily-driver terms.

Some of the senior members refer to "monkey-spank" from time to time.... poor monkey

 

Well this motor is going to be used how I stated earlier. Chances are never gonna go to work with me. Maybe a few times. And it is being made to run pump gas. CR around 9.75. Something in that ball park.