OBL1V1ON

THis is just something that i have always wondered. I know that there are alot of angles from the crank to the wheels and i always wondered how much power we loose going though all that redirection of force. I have a '79 (fully indpendant suspension) and i estimating that i have around 350hp. I havent dynoed or run the car at a track so i dont know. Does anyone have some knowledge on how much power a typical c3 can get to the wheels? I guess im just looking for a percentage here....


[Modified by OBL1V1ON, 10:15 PM 9/14/2003]

Shark Racer

Chuck Harmon's L-88 made 480.

Les's previous setup in his 427 made ~360.

Motorhead made 290.

I'll be happy to hit 200! (Doubtful, though :( )

Some guys dyno as low as 120!

As you can see, it's really hard to say what "typical" is.

rob75383

Work in progress, but I have #'s from the 2002 Bloomington Gold show.
see my sig.

WA 2 FST

I think with cars that are 20-30+ years old, you're going to get very wide ranges... and that's just with bone stock cars. The ones that were stock rated at ~200hp probably are making no more than 150rwhp. The BB's that were rated at the crank (and not like they are today using SAE net flywheel numbers) at 435hp, were more like 300rwhp. Then you have the L88s which were underrated, so they could be way up there.

It's a crap-shoot.

What I have found, for reasons unknown to me, is that 90% of the people on this board who have never dyno'd their cars over-rate their HP. I don't think its intentional, but that's what I've seen. These people put their combo in DeskTop Dyno, or just gave a rough estimate and honestly do not have the car tuned properly, etc. Obviously the only way to really know is to dyno it, either on on an engine stand or with a chassis dynomometer.

I just know there are guys with near stock, rebuilt BB's saying they make 500hp and their car runs mid-13s at 104mph. Sorry, but that isn't remotely close to 500hp. :)

On average, it is probably fair to say that a stick trans will suck up 12-15% through the drivetrain and an auto will be 18-20%. However, with a good non-lockup converter, the auto will show a higher peak TQ number due to its effective TQ multiplication through the driveline.

Just lots of factors here.

If yours is making an honest 350 at the flywheel, then I bet you are in the 285-295rwhp range.




[Modified by WA 2 FST, 10:31 AM 9/15/2003]

1979toy

Using a qtr mile MPH to HP calculator my rear wheel horspower is 255.
Desktop dyno gave me something like 340 HP (don't have the numbers in front of me). That would work out to 25% loss in the drivetrain, a number that I do not find surprising.
My sig will give you the mods to my 350.

OBL1V1ON

Well its just that according to what some pretty experienced mechanics tune it and tell me i should have around 350hp but i just dont feel it when i hit the gas.

I have some 4.11s ready to put in though :cool:

Corz

Remember, wieght plays a factor too. if you trap 100 mph in the 1/4 and you hit the scales at 3500lbs, you have about 280 at the wheels.. if you hit 100 mph at 3200lbs you dont have as much hp because you dont need that much to move 300lbs.. I hit 99.8 mph in the 1/4 wieghing in at 3250lbs (me in it) That would suggest I had about 260rwhp.

:cheers:

MotorHead

One way to measure the seat of your pants HP is put your car to the mat and if you say to yourself, "There ain't no way they are making anything ( besides Vipers and new Corvettes and the odd other car I can't afford ) this fast in production trim you are probably at or surpassed 350HP at the flywheel.:lol:

If on the other hand you say to yourself "Gee this doesn't feel that fast", then it probably isn't

Rule of thumb is 18-20% drivetrain loss for C3's :D


[Modified by MotorHead, 4:44 PM 9/15/2003]


[Modified by MotorHead, 4:45 PM 9/15/2003]

Turbo-Jet

aside from mechanical friction and inertia, there is zero energy (aka torque) loss when transmitted through proper shaft geometry that uses two in-phase u-joints or CVs. any loss from the transmission angle through the first joint is reacquired at the second joint. assuming the input and output shafts are parallel, but they need not be collinear.

my stock 454 did 230/320 at the wheels (MD-250), which are good solid numbers.

KJL

My 355 with a mild cam has 250/330 at the wheels.

Chuck Harmon

Turbo-Jet,

I'm not sure what you are describing? If you are saying that the drive shaft has minimal loss because it is virtually a straight shot between the trans and differential, I would agree that there is isn't much loss. But, are you aware that the internal drive gears have a very significant power loss? The reason the transmission and the rear end get so hot is the result of this power loss. "Energy can neither be created nor destroyed, it only changes form."

The rwhp of my ZO6 was 350, a 13.5% reduction from the 405 net rating. The 480rwhp of my L88 is just about exactly the same difference from the most often quoted 550-560 gross rating the L88 was claimed to make at the flywheel. For the L88, the net and the gross is virtually the same. Gross rating were made with open headers, I ran open headers, ~70 degree intake air (I have real fresh air hood) and no accessories. Only power robbers were alternator and water pump.

Chuck

Turbo-Jet

yeah, just refering to a driveshaft or halfshaft as a closed system. in summary, there is no net loss of force due to transmission angle issues :cheers:




[Modified by Turbo-Jet, 11:19 AM 9/16/2003]

Chuck Harmon

:cheers:

Chuck