Van

Doh! Missed that.

bad_monkey

@ van: Yeah - the change in bore is not helpful to those looking for factory FI bits. However it does mean that an S2 head (maybe even 968?) would drop straight on. That's another story...

@rogue: The Eaton M90 has a helical rotor - adiabatic efficiency is higher than most Roots type superchargers, nominally around 60%, but that changes through the RPM range. Poor mans solution would be the unit fitted to the Mazda Millenia as standard - but more a twin screw design than the "twisted rotor".

Rogue_Ant

Monkey,
Yep I'm familiar with the Eaton units. You could probably even get an HH unit (high helical), if you want. I also have a lysholm twin screw from a millenia waiting for a rebuild sitting here...

Regardless both units offer lower adiabatic efficiency then a decent centrifugal compressor. I would plan on using an intercooler. The stock 951 piece would serve you well.


-Rogue

RC924

Yep, an M90 would be the minimum choice of the common available blowers for your engine capacity and the boost you`re aiming for. From a commy/buick 3.8 V6?

Has a reasonable adiabatic efficiency for a rootes type although not as efficient as a lysholm or whipple. Problem with the later however is their capacity and the speed they need spin to achieve your goal.

Depending on your particular goal, be it XXX Hp, 1 bar boost, or more mid range torque and resultant driveability
for a street car it may be worthwhile considering a centrifugal SC. They have a much greater efficiency at higher RPM, but obviously the compromise is low and midrange. With my basic SC14 on a 2.0L the boost is fairly linear from 1400 to redline. However the goal was not max HP but rather smooth useable torque throughout the entire rev range. Acceleration is virtually instant, well < 200 ms, and has similar to V8 grunt driving around town. Not a race car, merely an enjoyable and quick street car.

Perhaps I may have done mine **** about, but IMHO considered it wiser, safer, and likely cheaper in the long run, to commence with a programmable and fully controllable ECU (MS2v3) with feedback from a WBo2. Stock FP should cope, injectors won`t, AFM??, and no need for old tech bandaids like RRFPRs.

How do you intend controlling the ignition curve with a stock ECU?

An IC is an absolute necessity at any usable boost level IMO. Data logged IATs over 60*C above ambient with just a quick blast off the lights with no IC. A major contributing factor to detonation. Sure that`s on a SC14 (82 CID) at 8PSI into 2.03L but a M90 overdriven to produce 15PSI into 2.7L won`t run any cooler.

Can well appreciate the countless hours of research and fabrication involved and also your desire to achieve something unique rather than "just buy a turbo". My point was that if the BEST option is to spend say US$1K on custom forged pistons that will in reality be a small price to pay in the overall scheme of things. Custom gaskets, head swaps, chamber machining or whatever has its costs too. Not only economic. Depends if you wish to make decisions from an engineering or economic perspective.

Fair enough. They must have the dies/tooling already and be in a viable position to do one offs on the 2.5,2.7,3.0 platform. Over on 924 board.org we attempted a group buy of 50 units and they are still refusing and citing a minimum order of 100.

Sorry if I came across as a nay-sayer. On the contrary.
Of literally hundreds of posts commencing "I want to SC or turbo my NA" there is only a handful of guys that have actually brought it to fruition. Sincerely wish you success with this project and will be following your progress.



Roger

Van

I was thinking, you'll probably need an adjustable cam gear, since the valve timing will change as the pulleys move farther apart (because of the fixed tooth spacing on the timing belt.)

Jeremy Himsel

You are correct which is why many of the OEM applications run a water to air intercooler. I personally never consider a roots supecharger when someone mentions supercharging. To me the low end gains are not worth the top end losses....which is why I have a turbo car I guess. My reference to efficiency had me thinking Vortec, Paxton, ATI, Powerdyne.

The roots type are pretty popular these days and the Vette crowd has been eating them up. I personally do not want full boost on my ZO6 @2K rpm's since it makes more low end TQ then is reasonably usable which is why I'm going a single turbo route. Maybe it would be nice on a 44 but then you have intercooling difficulties that eat up dollars quickly to resolve.

bad_monkey

Well, the Cometic gasket tech replied and said he'd recommend up to 0.08" thickness. That's 0.04" ~= 1mm over stock, which equates to about 9.5:1 CR.

So, a reduction, but perhaps a better compromise.

I'll post more when I'm not at work!

V2Rocket

this is what i am going to use..have one apart in my garage...

V2Rocket

we aren't so fortunate to have 350cid...

we could use the torque

gux944

Any progress?