Hi guys,

I'm curious what the typical drivetrain loss of an S5 N/A is? some ppl say its, 20-30 hp from fly-wheels.....some say its more, some say less. is there a percentage?

also, for those with dyno sheets, can u post ur findngs so i can get an average..................and what r some ways to reduce that wasted power?

thanks,
Carlos

 

To reduce drivetrain frcitional losses, reduce drivetrain friction. Only easy way to do this is using some more slippery tranny and diff fluid: synthetic gear lube.

I've only seen one engine brake/dynojet comparison for a TII drivetrain, sorry... doubt there's much out there for your N/A.

 

oh hey Sean......whats this talk about pulleys and such....and the electric fan

 

Underdrive pulleys spin the alternator & water pump slower. This helps reduce the chance of waterpump cavitation at high RPM, and reduces the physical drain of power from turning them as fast.

An electric fan removes the main fan & shroud, and puts on an electric fan instead. It takes power to turn it, from the alternator, but some people feel that this drain is less than the power spent turning the mechanical fan.

-=Russ=-

 

Underdrive pulleys have nothing to do with drivetrain losses. Drivetrain losses are from the tranny back.

Underdrive pulleys drive the alternator and waterpump more slowly, as each of the waterpump and alt have parasytic losses associated with spinning them. The power gain from underdriving is generally only a couple hp at best, and puts serious strain on the already over-worked alternator and waterpump.

The actual pulleys will weigh less, but this will not make the engine produce any more hp. It will merely reduce the inertial load on the engine and allow it to rev more readily. Lightweight pulley hubs manufactured out of aluminum and aluminum pulleys, in the stock sizing, would be a fantastic idea, with no negatives in using. (mostly for the main pulley... the alt and water pump pulley are already very light)

 

Since nobody has given you a percentage answer like you asked, I will give you the typical percentage = 18% loss between flywheel and tires on the ground. But this is an average of what's been measured - every car is a little different. If your 13B were stock, what's that, 140hp? So figure 26hp loss. More hp = more loss, simply becaue drag on the engine by the drivetrain increases with rpm - so the 18% +/- figure should hold pretty steady throughout the powerband. This is at least a ballpark for you.

 

Problem is: You can't apply a percentage. Countless Engine Brake to Rear wheel dyno comparisons have proven this.
Let's say that on a 100 hp engine, 15% is loss to the drivetrain, for 85hp to the tires.
Now, you throw in your Rat motor with your 8-71 blower and make a cool, even 1000 hp to the flywheel. Is the drivetrain going to rob 150 hp? No, but it will be higher than 15hp as well.

B/C of this, you can't give a stated percentage, b/c it completely depends on the power level of the vehicle.

As an example, on the 424 hp engine brake dynojet comparison I looked at, the total drivetrain losses were 12% on TII components. Do you really think it will be this low at stock power levels? Of course not.

To give such smart-assed remarks such as: "Since nobody has given you a percentage answer like you asked" is really quite poorly chosen as per reasons stated above, and b/c your answer of 18% is merely a guess, no better than anyone else's. Why not just state 20%, or 16%? We don't have a dozen brand new stock cars to do rear wheel testing on to calculate an average, so we can never know for sure. We also can't work backwards from a rear-wheel engine dyno, as these engines are not pumping out exactly their stock hp values; it won't be anywhere close to them.

The only valid answer that can be given is: It depends on far too many variables to give a solid answer to this question.