Positively Displaced

[Xnke]

M62 will produce about 250RWHP, best case. M90 can do much more, but it's bigger and harder to fit into place.

 

Bernardd, If you want to try it after the supercharger...go for it. I tried, it tried to kill me multiple times, I moved it to where every single manufacturer puts it. It hasn't tried to kill me yet. Even using the bypass valve to dump the pressure didn't stop it from finding throttle positions that balanced the system, holding the throttle open and the supercharger in boost. I had to pull the throttle shut with my toes more than once!

[duragg]

I want to block off the silencer holes too... 

Weeeen// weeeeeeEEEEENNNN /// WEEEEEEEEEEEEEN

[Bernardd]

M62 will produce about 250RWHP, best case. M90 can do much more, but it's bigger and harder to fit into place.

 

Bernardd, If you want to try it after the supercharger...go for it. I tried, it tried to kill me multiple times, I moved it to where every single manufacturer puts it. It hasn't tried to kill me yet. Even using the bypass valve to dump the pressure didn't stop it from finding throttle positions that balanced the system, holding the throttle open and the supercharger in boost. I had to pull the throttle shut with my toes more than once!

Odd that it work on 280zedx's car without issue.  I've seen pics of others that worked as well.  Did you have a blowoff valve between the charger and throttle body? 

[Xnke]

Yes, two of them. Both 1" diameter, PLUS the bypass valve on the supercharger itself. I could STILL find load and throttle positions that would cause it...usually mid and high speed cruise. Not something you see in a racing car, like 280ZedX's built.

 

Ask any manufacturer of supercharger systems, they'll vehmently try to dissuade you from doing this for the exact reason of throttle damage/throttles blown open.

 

Blocking the silencer holes makes it quite loud, but can damage the blower if you weld the holes up, and can provide plenty of hard stuff for the engine to ingest if you use epoxy. You could machine the lower of the super for a block off plate and go that route, which is absolutely bulletproof.

[Bernardd]

280zedx's car must be a freak setup then.  He drove it on the street for several years before stripping it down to a race car.  I have no idea why his works but it does and he's never had any issue like that.  His megasquirt on the other hand has been and interesting war that never seems  to end.  But that's another story.  I'm confident that you'll figure it all out.  

[Six_Shooter]

I don't understand why you'd have issues with the throttle being blown open, when using a bypass valve.

 

Turbo engines don't have this issue, and I haven't known any supercharged cars that I have been around to have this issue either.

[Xnke]

A turbocharger or centrifugal supercharger is NOT going to blow the throttle open, as they are dynamic displacement compressors and vary pressure and flow based on demand. A roots or screw type postive displacement blower WILL have the ability to do so...either by having a pneumatic "balance" point in the system, or by just bending your throttle plate around the shaft. I have seen and suffered both, and the latter is a well know problem.

 

On a 6500rpm throttle closure, the supercharger displaces 62ci per rev and is turning 14,995rpm, moving roughly 460cfm of air. It doesn't stop on a dime, your engine takes a real number of cycles to decel, and with the throttle closed that 460cfm WILL find a place to go.

[Xnke]

Going to crib from the miata boys again...the car drives very nicely from 2krpm and up, but has the idle sag and stalls at lights if the idle is set lower. This is apparently caused by the very large throttled volume. Not sure hoe the Supercoupe got away with it, but one positive solution appears to be going back to the dual synchronised throttles, or back to the (imo dangerous) post supercharger throttle. I'll be setting up my old synchro setup again in the next few days and once that's done, tuning will take the priority.

[Xnke]

Things are good. New cam makes more power overall than the wide-lobe-seperation cam, but it breaths too good for the supercharger...Making 140kpA at 3800RPM but it falls off slowly to about 135KPA at 7300RPM. I'm moving as much air as the little M62 can move...and then a tiny bit more.

Also noticed that doing back-to-back-to-back-to-back, i.e., just drive back to the starting line and stage up again, 1/4 mile drags, the IAT's and coolant temps get lower each pass...started at 122* IAT and 181* coolant temps...8 full-throttle passes later IAT was 109* and coolant temp was 166*. No time slips, we were running untimed tonight. Was crossing the markers at 5200RPM in 4th gear, so that's just about right.

Found out what happens if you overfill the gearcase on the super though...the slightly higher hot pressure will force out the excess all over the engine bay.

 

Don't worry about blocking the silencer holes...at WOT it'll still drown out the exhaust.

Edited June 2, 2014 by Xnke

[Xnke]

Started work on the M90 case this weekend...I would say it will be simpler by far to work with a supercoupe M90 than any of the GM blowers.

 

GM blowers are FAR cheaper, though....

[Xnke]

Started with a standard GM Series II 3800 M90 supercharger, gutted the case and started chopping. Got it cut down, then went to the stock shelf and started fitting stuff up.



All cut down on the back end, anyway. Getting things cleaned up and this made it VERY easy to do the intake side porting.

Now you can see how we're going to work this. Raising the inlet up and opening the bore from 65mm to 83mm.



Getting things sealed back up on the inlet side, all the intake porting is done, just need to run over things with a cartridge roll or two and clean up the burrs and divots from the carbides.



Much more direct path into the rotors, will be noisier but that's easily dealt with for 99c at the shooting store.



A few good shots of the porting, both inlet and outlet ports. It doesn't take much to push an M90 up to 600CFM inlet flow, but it does take some work to get one higher than about 650CFM...Stock this housing pushes 520-540CFM.





Not much to it, a little cleaning in the case and all those "score marks" wipe right out. they're not even deep enough to catch a fingernail, but the carbon and oil deposits make them look like someone went at the case with 36 grit paper!

Might try to find another rotor pack, as this one has some miles on it. They're not terribly hard to find and this one will work for a while yet. It's not leaking nose drive oil, so the front bearings are still tight enough to keep the seals from going to shit. I've rebuilt the rotor pack in my M62...it's a shit job unless you've got the special jigs to do it. I probably would be money ahead to pay the 500$ to have a rotor pack re-coated and rebuilt. However, good condition M90 rotor packs are all over and are far less money than a newly rebuilt one.

I still need to cut down the nose drive to the proper length, then it's two ball bearings, one snout seal, and two case bearings to replace. A new baseplate will have to be cut and I will be refining the method used to make the charge pipe, hopefully making it flow better than the current charge pipe and also lower profile...that way I can get it up off the lower radiator hose and alternator.

[Xnke]

Progress on the M90 front.

Had to do a little sculpture to get the case in place.



The old PCV tower had to come off, and be blended in.



Now the snout was too long, so I mounted it up and turned it down to the proper length, and cut a new bearing recess.






Nearly finished...need to replace that seal. It's got a big cut in it right across the lip; that isn't going to fly.



Yes, that is the shaft from the M62...I am having a custom hub cut for an interchangeable pulley system, since the M62 keyed shaft is pretty much unsupported by anyone.

[Xnke]

Wow, haven't updated this thread in a long while.

 

Haven't driven the car much, it's developed some suicidal tendancies, problems like electric fan relays rusting up and not turning the fans on and the like.

 

That and completely bald rear tires that need to be replaced...at 9lbs of boost it was plenty of fun.

 

Now it's time to work on the NVH problems...mostly the incredibly intolerable whine of the supercharger, and fitting a complete interior. Right now, I'd never want to drive this more than an hour at a time...I'd be deaf by the time I got anywhere.

[seattlejester]

Would you happen to have a sound bite? I absolutely love a good super charger whine, granted living with it would probably get quite tiresome I imagine.

[yellowoctupus]

Wish I had followed this thread earlier, it's was a good read.  Something I started doing back about 9yrs ago, and ditched the project to put in my 4.6.   Probably a better decision in the long run for me, but I kinda regret not finishing up the M62 setup.