How to rig a twincharger up?

[chuntington101]

right again steve! but a well mached roots blower can be VERY effetive!

there is a guy with on the corvette forum thats running a 2.8ltr Kenne Bell (twin screw) on a 402 ls2 and hes making about 850rwhp on pump with meth (91 octane!!). makes avout 700lbsft at 2000rpm!!!

Chris.

PS i think he was running 18psi from it!!!

Edited by chuntington101 on Friday 1st September 20:04

[love machine]

stevieturbo said:

mave said:

Turbochargers tend to heat the air more than superchargers, so for a given boost level at supercharger exit, the air temperature will be higher, so the density (and hence mass flow)lower.

I dont think that statement is true at all.

depends on turbocharger used, and supercharger.

Lets see a crappy old Rootes blower with no IC pump 20psi for example, compared to an efficient turbocharger at the same boost level.

In general, turbocharger compressors are a LOT more efficient than rootes superchargers.

IIRC, an average turbo gives a peak AE of about 82%, this is similar to a Lysholm compressor (82%) apart from the turbo has no drive belt. Vane types are about 70%, roots 4th gen are about 64% and old straight lobed roots a lot less. This is for about 10PSI and standard conditions.

[GreenV8S]

mave said:

What I was thinking about, is that the supercharger is also constant exit flow volume (isn't it?). Turbochargers tend to heat the air more than superchargers, so for a given boost level at supercharger exit, the air temperature will be higher, so the density (and hence mass flow)lower.

I assume we're talking about an Eaton. These have almost constant volumetric efficiency at the inlet regardless of the back pressure; it's the intake pressure which matters. They are also relatively inefficient compared to turbos, and the efficiency drops off appallingly as the pressure ratio across the blower rises. Eatons definitely wouldn't be the weapon of choice for anything producing lots of boost - but they're not a bad way to kick-start your more efficient turbo, if lag is really important to you and you don't care how difficult the engineering is.

Edited by GreenV8S on Saturday 2nd September 00:02

[Pigeon]

chuntington101 said:

right again steve! but a well mached roots blower can be VERY effetive!

there is a guy with on the corvette forum thats running a 2.8ltr Kenne Bell (twin screw) on a 402 ls2 and hes making about 850rwhp on pump with meth (91 octane!!). makes avout 700lbsft at 2000rpm!!!

Chris.

PS i think he was running 18psi from it!!!

Twin screw != Roots...

[chuntington101]

Pigeon said:

chuntington101 said:

right again steve! but a well mached roots blower can be VERY effetive!

there is a guy with on the corvette forum thats running a 2.8ltr Kenne Bell (twin screw) on a 402 ls2 and hes making about 850rwhp on pump with meth (91 octane!!). makes avout 700lbsft at 2000rpm!!!

Chris.

PS i think he was running 18psi from it!!!

Twin screw != Roots...

yeah it does, but these things are pushing wnumbers that no true "roots" as we know it would make! i will try and get the dyno graph for the engine, its simply outstanding.

Chris.

[mave]

stevieturbo said:

mave said:

Turbochargers tend to heat the air more than superchargers, so for a given boost level at supercharger exit, the air temperature will be higher, so the density (and hence mass flow)lower.

I dont think that statement is true at all.

depends on turbocharger used, and supercharger.

Lets see a crappy old Rootes blower with no IC pump 20psi for example, compared to an efficient turbocharger at the same boost level.

In general, turbocharger compressors are a LOT more efficient than rootes superchargers.

Interesting, I thought that while the rig AE of a turbo compressor is better than a rootes (for example) conducted heat back from the turbine wheel into the compressor made the actual heat input into the charge higher?

[Pigeon]

chuntington101 said:

Pigeon said:

chuntington101 said:

right again steve! but a well mached roots blower can be VERY effetive!

there is a guy with on the corvette forum thats running a 2.8ltr Kenne Bell (twin screw) on a 402 ls2 and hes making about 850rwhp on pump with meth (91 octane!!). makes avout 700lbsft at 2000rpm!!!

Chris.

PS i think he was running 18psi from it!!!

Twin screw != Roots...

yeah it does, but these things are pushing wnumbers that no true "roots" as we know it would make! i will try and get the dyno graph for the engine, its simply outstanding.

That's because they are not Roots! Roots do not have internal compression. Twin screw ones do, so they are more efficient. I've just checked the Kenne Bell website and they are definitely twin screw, not Roots. And they're at twin screw prices too

Some Roots blowers (eg. Eaton) have twisted rotors that look a bit like a twin screw (and further confuse the issue by having a port layout apparently like a twin screw) but they are not twin screw, they're still Roots with no internal compression.

[GreenV8S]

mave said:

Interesting, I thought that while the rig AE of a turbo compressor is better than a rootes (for example) conducted heat back from the turbine wheel into the compressor made the actual heat input into the charge higher?

Is that a guess, or does this effect really matter? I'd have thought that the thermal contact between the gases and the turbines would have been so weak and brief that the amount of heat transfered would be relatively little, compared to the effect of friction and adiabatic heating.

[chuntington101]

Pigeon, are we trying to arguee the same thing??? lol

Chris.

[Pigeon]

chuntington101 said:

Pigeon, are we trying to arguee the same thing??? lol

Chris.

Hmm. Possibly... Re-reading your reply it seems that I perhaps assumed too wide a familiarity with C syntax

!= means "is not equal to".

Sorry to you!

[chuntington101]

haha no problem mate!

i think we both agree that a twin screw is much better than a roots style blower, but will cost more!

but i still think a turbo is the better power addrer, esp. on smaller engines.

Chris.

[mave]

GreenV8S said:

mave said:

Interesting, I thought that while the rig AE of a turbo compressor is better than a rootes (for example) conducted heat back from the turbine wheel into the compressor made the actual heat input into the charge higher?

Is that a guess, or does this effect really matter? I'd have thought that the thermal contact between the gases and the turbines would have been so weak and brief that the amount of heat transfered would be relatively little, compared to the effect of friction and adiabatic heating.

Yeah, OK, this was based on what someone told me. I should know better than to listen to people against my judgement.... Just did some hand calcs, even if you could get 1000C difference between the compressor and the turbine wheel, the energy conducted along the shaft is only a few percent of the energy going into the air flow!