Ivoidwarranties

iTrader: (7)

Sam is correct on this. If your driveline sucks up let's say 18% then no matter what you have driving the engine the rear wheel hp will be 18% less than flywheel hp.

Seperately, I know what you are trying to say but I believe there may be some confussion somewhere. The power it takes to drive a supercharger can not be subtracted (or added) to that base hp number. You can say a supercharger takes "x" amount of horsepower to turn, but you can't say the engine would make "x" amount more if we just took away the parasitic losses. It just don't work that way (I don't know why, it just does). The hp it takes to drive the SC that you are trying to add to the overall hp number is not seen as power by the engine but more likely stresses. You can always try to make a more efficent SC and that's where the stresses (friction, heat build, etc.) are lessened and the end result converts back to (more) hp output.

G37Sam

See the power at the flywheel aka bhp is not the total power an engine makes in reality, and I believe this is what Modme is trying to say. The Gross Power an engine makes is the summation of the power delivered to the flywheel + power used to turn crank, alternator pulley and all the other fancy pulleys sitting in front of your car.

=> GHP = Bhp (power to flywheel) + Power to all the other pulleys listed in the diagram below:


In our cars, GHP = 350hp, bhp = 330hp I believe, meaning you will need 20hp to power all the other pulleys.

That is why when you replace the crank pulley with a lighter one, all you are doing is removing some of the power required to turn the crank pulley and sending it to the flywheel (Bhp), while GHP is still the same.

If you were to power a supercharger kit using your engine (adding another S/C pulley), but for some weird reason use the compressed air to dry your girlfriend's hair for instance rather than blow it back into the engine, the GHP again, will still be same = 350hp. However the bhp will now have to donate a little power to get the S/C pulley spinning. Assuming the S/C requires 30hp to spin, then your bhp will have to drop by 30hp to compensate.

So now we have, ghp = 350hp, bhp = 300hp, s/c_hp = 30hp and your other pulleys_hp = 20hp (everything should still add to 350 by law of conservation of energy, if you neglect frictional losses)

Assuming drivetrain losses of 18%, your whp should be bhp * (1-0.18) = 246whp.

Now let's say the S/C is blowing the air into the engine and dyno graphs show 450whp for instance, your bhp becomes 548hp, add to that the s/c_hp = 30hp and other pulleys_hp = 20 you are looking at almost 600hp gross.

Would this be any different from the gross hp number put down from a TT kit?

Depends on how much back pressure your turbine will put on your pistons, they should be more or less the same however (for the same compressor) since the piston is connected to the crank shaft via the rods. So you're applying the same force eventually, just on a different section of the body. Excuse my PS skills lol

Modme

iTrader: (17)

Let me ask you something then. Given the same boost pressure, should the same engine produce the same amount of GHP? If so, where did the power from the 2 extra psi go for the supercharger? It went to power the supercharger.

Like you stated: GHP - powertrain loss + crank loss = whp

Or GHP = whp + powertrain loss + pulley loss

So for turbos at 6 psi: 450whp + 81hp(18% loss due to powertrain and crank) = 531 GHP



For supercharger at 8 psi: 450 whp + 81hp (18% loss due to powertrain and crank) + 40hp to power blower = 571 GHP

Would the extra GHP produced by the supercharger engine not cause extra stress on the internals?

whiddles

iTrader: (2)

I think the people that are on the market for these SC kits are not your daily drag racers. We are daily drivers that like to know we have power if need be. So the little extra stress is not a big deal. Our cars will last just as long as a TT car would, because people with TT use their cars more for hard driving. Just my beliefs

WhosUrBuddiee

iTrader: (1)

No car payment

Vu37

I need to hit the lottery so I can say the same.

terrycs

iTrader: (37)

Some dyno plots to go with this table would be cool. That will tell a lot about how much/when the torque and power are applied. Peak also really does not mean much with a boost controller installed.

G37Sam

I don't know why you're assuming the "extra" 2 psi is going to power the supercharger, if you had a big compressor and a small compressor both pushing 10 psi, would your hp numbers be the same? never.. and that has to do with compressor efficiency

Also, there are other factors that come into play, like the tune to start with, how aggressive or conservative it is, pressure drop across an intercooler, pressure drop across piping etc..

djm17178

iTrader: (1)

What about warranties on the two kits? Is there a warranty on the SC itself, and does the warranty extend to the rest of the engine?

I seem to recall the Stillen thread saying that there would be an "optional" warranty available.

Also, how would a SC affect the factory warranty? I'm sure they would no longer do any warranty work on the engine, but would that extend to the rest of the car as well? I'm not a mechanic, so I'm debating whether it's worth it to put in a SC at all, due to the warranty/reliability issues that may come up.

whiddles

iTrader: (2)

stillen has 3yr/36,000

Modme

iTrader: (17)

None of the factors you listed matters because the pressure is measured in the manifold. Pressure drop across the piping and intercooler would've have already occurred. Tuning is done by the same person, I'm sure Sam is very consistent with his tuning methods.

What you're saying about compressor housing has no effect on the amount of air entering the engine. The engine volume is fixed.

The mathematical equation for Boyle's law is:

pV = k

where:

p denotes the pressure of the system.
V denotes the volume of the gas.
k is a constant value representative of the pressure and volume of the system.

Volume is directly proportional to the pressure. Inside the same engine, same psi = same volume of air. The turbine housing affects how soon and how much air can be delivered to the engine. However, these factors are controlled by the supercharger pulley sizes and turbo wastegates. In other words, the pressure and volume of air is regulated.

Therefore, at 6 psi, both turboed engine and supercharged engines are seeing the same amount of air. Given similar tunings, they should be making the same amount of gross horsepower. However, how they differ is how the power is distributed.

OMG37

iTrader: (2)

I believe the rotrex has a 3 year warranty as well.

Buddy Revell

iTrader: (2)

Anyone know how much Stillen's engine warranty is on the new kit? I think it was an extra grand in addition to the SC system to get the engine covered on the older G35/350Z kits.

G37Sam

Why thank you lol

Exactly, but those don't occur for free do they? Compressors would have to work harder to generate the same hp if your setup is less efficient. Meaning even though you're seeing 6 psi at the manifold, it could be up to 10 psi right at the compressor.

Actually according to your equation, they're inversely proportional

You seem to have ignored a very important factor in that equation, and that is Temperature, PV does not equal to a constant, but rather mRT (and that's assuming 100% Volumetric Efficiency, which we both know is not the case)

Boyle's law only applies when your temperature is kept constant bro

For a fixed amount of an ideal gas kept at a fixed temperature, P [pressure] and V [volume] are inversely proportional (while one increases, the other decreases).

WhosUrBuddiee

iTrader: (1)

I made my decision.........


(drum roll)