S2kRob

Yep, looks to be. I think I can do a non intercooled version without moving anything, intercooled verion would need to relocate the alternator.

PilotKD

Magnuson's MP units are very efficient. If anything, you could install a water injection kit to kick in at high rpm if detonation became an issue. I think as long as you ran it low boost, 5-6psi, it'd be fine without an intercooler.

Kris

ultimate lurker

Rob,

A rough approximation of supercharger rpm required for a given boost level can be computed as:

1/2 engine displacement x [(boost level + 14.7)/(14.7)] = liters/revolution.

Divide this number by the displacement/revolution of the blower in question and multiply by maximum rpm. You have to throw in a bit of a fudge factor for inefficiencies in the system, as well as high VE engines and the like, I usually use 10% or so.

For an F20C, you'd be looking at 1.6+ liter/revolution, which would require 14,500 revolutions at 9000 rpm with an M62. I can tell you that the thermal efficiency goes out the window by about 12k rpm on an Eaton blower. A Whipple/Lysolm would be a better choice, but I don't know what they have for actual specs.

I would try and size the blower such that it spins close to a 1:1 ratio or slightly overdriven. Something in the 1.4-1.6 liter/revolution range would be ideal, if it will fit (which is an issue).

UL

CrazyPhuD

So for twin screw style superchargers whipple SC are made by lysholm....they have twin screw SC from 1.2, 1.6, 2.3 and 3.3 L/rev.

You can find the specs here and also the graphs of Thermal efficiencies


http://www.rotor.se/lysholm/en/p_1600.asp

Keep us up to date on your progress!!!

timg

IIRC, Whipple bought the rights to build Lysholm blowers a few years ago. Then, within the last year, Eaton purchased Whipple and now many Lysholm blowers on stock cars are straight from Eaton while they have left Whipple to cover the aftermarket.
http://www.whipplesuperchargers.com/news.a...sp?articleID=50

Tim

S2kRob

Hi guys,

Thanks for all the great feedback. UL, I figured out the formula on my own just by crunching the numbers, but thanks for confirming I was on the right track!!! Much appreciated.

What I found was that Whipple makes an SC that displaces 1.6 litres per revolution. Given a volumetric efficiency of between .8 and .9, that would mean that the SC would need to spin at around 9500rpm at redline for 7psi boost. Which sounds darn good to me.

If we knock the boost back down to 5-6psi, we can spin it slower and negate the need for the complexity of an air/water intercooler system.

Also, Whipple makes fully contained SC's that require no outside lubrication, which is a very nice feature.

jsalicru

I would be very interested in seeing someone develop this. Worst case, if you can't do an aftercooler, just setup a water injection setup. Make it come on at something like 4psi and up.. and you are cool.. Some water injection setups are actually very inexpensive. My friend built one for his turbo car for only $200

I think that this is something that can work. I dono why it hasn't been pursued at all, but it would be great. Consider this also just in case... The SLK has the Roots type installed like a Vortech SC is... they have it before the throttle.

ultimate lurker

Only problem with water injection on a PD blower is water distribution. Unless you're willing to go to one H20 injector per cylinder, its very difficult to get sufficient dispersion in a little manifold plenum (been there, didn't work well).

UL

CrazyPhuD

So here's my one big reservation about a PD SC. Since boost occurs early, won't we have many of the same tuning/reliabilty issues as turbos. One of advantages(for reliabilty) of the existing kits is that you get very little boost down low. Only at high RPM does your engine exhibit significant boost. Therefore there is less stress on the engine in the common case. Also since little boost occurs at low rpm's less tuning would be needed.

Will a roots/screw style PD SC introduce many of the challenges that exist with turbo setups?

S2kRob

What tuning/reliability issues related to boost at low rpms do turbo engines have?

Tuning is tuning, you either do it right or you don't, regardless of whatever you are running.

I'd probably go with an AEM EMS on this setup.