924Board.org

[Keaton]

ok so what works better a "root" style or a "screw"? dont the screw type spin inwards and the root spin outwards, right, wrong, 50/50?

what about using a intercooler, how hot do the air temps get on a blower? and using an air-to-air- then into an air-to-water.

the average air temp were i live in around 110F for 6+ months.

[Raceboy]

Screw-type is more efficient and the most efficient one is twin-screw type, Lysholm found on Mazda Xedos/Eunos Miller cycle engines. Intercooler is a good thing especially when supercharging N/A pistons and head.
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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[Keaton]

well i was thinking of puting a 931 head with out changing the pistons to get a really low compression so i can run 12-14+ psi

[endwrench]

[leadfoot]

You should buy corky bells "supercharged" this will answer all your questions and give you a few ideas on setups...
Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[924er]

[Keaton]

[ESC944]

That is low compression - your off idle power/acceleration would be terrible. Way way to low - you would end up with basically an all turbo car - sucks under any other condition but boost- unless you built it so that you could have boost all the time - would royally suck!

Solution is either more compression - or boost off idle - which could be had with a supercharger - for off idle spool up then use a turbo for rest of the boost - you could gear the supercharger for boost off idle (roots or screw offer the easiest arrangement).

Something like the SC12 or SC14 units off a toyota - mated to a turbo system - clutch pulley to disengage the sc (already part of the setup) and a simple one way valve.

Eaton M62 off Mercedes units also feature this arrangement - of course you would need a cooler - to cool charge - roots and screw units do add heat - so feed to an IC then to intake.

This also would allow a much larger turbo to be used - for the boost range you are discussing.

You could also do the same thing with both a roots and Centrifugal- like a procharger - good for up to 30+ psi - problem - is space for a second supercharger.

One + turbo simple and effective - more so than it sounds.

Otherwise bump up compression and run whatever makees you happy for boost - keep in mind a roots or screw type - is only good for about 1 bar - with out serious risk of failure - most are not recommended to run over 12.

Centrifugal - depends on the unit and bearings it was built with - a unit capable of over 1 bar like the procharger unit - will be very very expensive.

Better off with a turbo for that kind of boost -

Even better if the engine is up to loads and the driveline - how you get those boost levels is up to you -

6.5:1 + 1.5 bar vs. 7.5:1 + 1.5 bar more power at 7.5:1 of course stress raises as compression or boost increases.