A turbo unit is an obstruction to the exhaust, so it also "robs" power from the engine. The key to both turbo and supercharger is they produce more power than they consume!

 

[QUOTE]Originally posted by Garyj
[B]

A turbo unit is an obstruction to the exhaust, so it also "robs" power from the engine.

 

no free lunch

 

I think it's pointless arguing about power loss when comparing turbo vs. supercharger. But that's just my opinion. Both draw power to make power.

The key advantage of the turbo over the supercharger is the ability of the turbo to be on near full boost at low rpm. This only holds true for a small turbo running moderate amounts of boost (eg, audi S4).

But, of course, with a supercharger, you get much more predictable power delivery, which is safer and more 'trackable' on a road course.

 

speaking of turbos - anyone go to the turbo-netics conference last weekend in los angeles? (8-18) - I was invited, but had the irvine s2k meet.

 

The impeller (I think that's what it's called) is actually placed in the exhaust path. Exhaust gasses must turn it, thus turning the fan that forces air into the engine. Larger pipes will help exhaust gasses get out, but the obstruction remains.

I'm not sure which is most efficient - turbo or supercharger. I do know that in the "old days" the DISADVANTAGE of the turbo was it's slow response. Roots turbos did not have this LAG. I'm assuming the Comptech (centrifugal I think it's called) may not do the same.

I'm enjoying this thread!

 

The inducer and exducer on the hot (turbine) side does not *rob* power on a turbo. The A/R chosen by the builder does. The A/R is the calculation of the scroll opening which the exhaust gas moves through to create velocity. On the other side (compressor) the scroll is used to create positive pressure to force air into the plenum. A/R on the compressor side isn't as important as the turbine side. As the gas moves through the scroll, the opening becomes larger and the gas hits the inducer turbine blades. An A/R of .48 is more restrictive than an A/R of .72.
Lower A/R = fast spooling turbos = less to no lag = running out of steam faster = lower efficiency (maybe 72% or so)
Higher A/R = less responsive turbos = more lag = more power potential = higher sweet spot = more efficient.
Efficient = heat = detonation. Larger turbos = more efficient (generalized).

A simple way to look at it - choose A/R with disp of the engine. A lot of other factors involved, but you get the point. A T04E, 60 Trim, .72 A/R on a S2000 would be very laggy, but super efficient, and could spool to 9K. A small T25 or Audi A4 size turbo would spool low, but would be very inefficient, max out around 6K rpm and probably would cause the S2000 to detonate (<< lots more factors involved here too).

I personally belive the S2K will run best with a full bearing cartridge GT series (HKS) turbo, decent sized intercooler and thicker head gasket w/ optimized cams and lower vtech transition.

 

Forgot to mention - most turbos are much more efficient than a SC. As I said, efficiency directly relates to the *heat* of the intake charge or air coming into the motor. Higher intake charge temps lead to detonation. Basically because choosing an efficient turbo is important, you can effectively reduce the intake charge temps and run higher boost levels safely (generalization).
A supercharger with no intercooler and high boost levels matched to a motor with high compression is a deadly mix. Comptec's SC is truly an amazing piece of work and certainly took lots of R&D and maybe a few burned pistons to iron out. But the potential for more torque and power from our motors is there. Gobs more torque. Next year we will see 12 sec daily drivers.

The reliability of the diff and tranny is another issue