Okay, so a few of you know my story, supercharged my sunfire, and for the past month it has acted like it is not. I have checked and fixed/replaced so many things: new by-pass, gutted stock cat out, replaced injector orings, reinstalled mainfold, and replaced the alternator. My fuel pressure is fine, and thee engine passes compression, but I have not watched one of the sensors' readings this entire time.. The MAP sensor, while being read by a craftsman OBD 2 scanner, reads an averaged 10 inHG while idling. Now, just as my boost gauge says 5 PSI or so, when I go into boost, the sensor shoots up to 36 inHG. Ive read that 36"HG converts to 3.5 PSI or so.. Thats pretty low. I dont have any boost leaks. I have never heard or seen a supercharger before, so I do not know how one acts, but honestly, I dont hear it until about 4 or 5k RPM. Although, lol, I have no resonator, no cat, and a Pacesetter muffler, which is pretty much straight through, so granted I may not hear it as much. But anyways, how can I check/inspect my M62? When I recieved it, it was dry, no oil at all. And the stock pulley was hammered on, therefore I slightly hammered it off. Yes, I do have a ZZP pulley puller, now at least. Im getting upset of how it isnt performing as it did day one..

Fml.. reading about how much oil I was supposed to put into the blower, I used 6oz. I used 2, 1.5 bottles of GM supercharger oil. The forum I got this info to fill it, was wrong. This may be the problem?

your math is wrong. i think you should take the blower off and spin it by hand and see how it sounds...it should create a sucking sounds at rotors, should not be loose or jingly at all and have no rattles.

Lol wouldnt suprise me, cause it wasnt my math. I got it from another site, but it sounded right. And also, what would too much oil have done? Ruin the couplers or bearings?

what method did you use to determine you don't have a boost leak?

Ugh.. My ears.. And carb cleaner. And since I have already redid my entire intake, I pretty much excluded a boost or vacuum leak as an option anymore. Plus vacuum is perfect at idle. I have two questions though, what are the effects of too much oil in the M62? I cant find that answer anywhere, and I dont know about superchargers.. Secondly, if you manually close the by-pass at idle, by removing the vacuum hose and plugging it, should my gauge/MAP sensor read vacuum still?

in theory, too much oil will cause foaming and ultimately poor lubrication within the supercharger which can lead to failure. I would recommend removing and refilling to the proper amount.

not sure on the bypass at idle. I would assume you could still read vacuum as the charger may not be moving that much air at idle. I would expect that you would see the needle move more towards atmospheric when you have the bypass closed but I could be wrong.

how much is an m62 to the older m62 and m90s take 6oz. 6oz isn't much and i bet the m45 and new m62 take the same i bet your problem is something else cause i put 8oz in mine and i have had no issues.

start looking into other things and have someone that know that stuff help cause it sounds tgo me like your blaming something that isn't likely the problem to make you feel better

boost is also a measurement of restriction if you have less restriction in the head and exhaust you will run less boost. i put a ported manifold on and dropped 1lb of boost. seeing as you have a gutted cat and a straight through muffler what are you running for a header



JBO since July 30, 2001

yeah, I have a large LSJ header, full 2.5" exhaust (with high flow spun cat) and i max at 8lbs of boost. Even verified with multiple boost gauges, all consistent. So a well flowing system = more efficient (more power from less boost is always a good thing!) Up until this post, I believe I have the lowest psi number from the stock M62 blower...making the same if not more power than others over all on this setup (most get 10+). I would think however that 3-5psi is definitely too low to be getting potential power. I also noticed a very slight increase (like MAYBE .5 psi) upon removal of one of my Phenolic spacers (due to bolt issues).


04 Cav. 2dr. 5spd. My DD. 'Nuff said.

Idk I keep checking and replacing everything, Im not sure what it is, but I know Im getting low boost. I have a stock pulley on a stock M62, Pacesetter header, gutted stock cat, Pacesetter cat back exhaust, with its straight through muffler, and for the intake I ran it to my existing AEM intake. I have a dual pass endplate installed, but my heat exchanger is not running, and I have the injector cups that Jason made for me, all with the GM reflash.

I get into boost at any gear, my MAP sensor reads 36"HG and does not change much. Its about 60 degrees in Ohio now..

im thinking you need to look at all your vacuum hoses and check any o rings that you have installed related to the SC install. if it runs just has low boost then your leaving somewhere and i highly doubt its the SC itself

proper diagnostics is far greater then the guessing parts replacement



JBO since July 30, 2001

I have been told that many times.. I have. I get my head right up against everything and sprayed carb cleaner everywhere. Okay, considering I have a "boost leak" it would only be in the intake manifold and the injector orings (past the blower). I have just replaced and properly installed new orings, so that is eliminated. I have replaced my by-pass, and no difference so that is eliminated as well. I really wish I didnt have to eplain myself through all of this but everyone insists that I missed something.. I have removed the intake manifold, and resealed the gasket with gasket sealant, no difference. I have also removed the stock endplate and removed the 2 cores for a dual pass endplate, and still no difference. The only other places for air to get out would be the nipple on top of the manifold which goes straight to the FPR. Unless the FPR lets boost out, its highly unlikely. The last and only thing I didnt check is the PCV check valve built into the intake manifold. Does someone assume it is that? Cause I dont. But id love to get a new intake manifold too yeah.. Just kidding.

Update: plugged my boost gauge back in (i didnt have a permenant place for it in my interior so I didnt always have it on) and it reaches about 9psi when in 2nd, about 4-5k rpm. Obviously when at low prm it reads a minimum of 3-4psi.. But that surprised me. Why is the MAP sensor reading 36inHG? I looked up a conversion of 36inHG to psi and 2 sites said 17.something psi. Clearly thats wrong. Lol highly confused, but relieved that I may not have as big of an issue as I thought..

So it sounds like it's actually working just fine then. That's good news.


"In Oldskool we trust"

Well I really hope so but it feels like its lagging.. should the boost vary that much? From 2k rpms with 3psi to about 5k rpm with 8psi? I feel silly thinking theres something wrong, but wouldnt anyone get bothered by that? Anyways, I guess this is how it feels, and I must have assumed it was stronger and its just my imagination.. Lol I can sleep better knowing theres not a problem.

the only time boost will be instant and constant is when you go and stay WOT. other then that, seeing anywhere from 1 to whatever your max boost is is perfectly normal
depending on engine load and TPS. its not all boost or no boost. there will be times its only 2 or 3 psi.

Okay, cool I didnt know that. Haha well.. I guess its just mods and fixing cosmetic things from here on.. Thanks guys

pyromechanic wrote:Well I really hope so but it feels like its lagging.. should the boost vary that much? From 2k rpms with 3psi to about 5k rpm with 8psi? I feel silly thinking theres something wrong, but wouldnt anyone get bothered by that? Anyways, I guess this is how it feels, and I must have assumed it was stronger and its just my imagination.. Lol I can sleep better knowing theres not a problem.

With my Harrop i see(via boost gauge) 5-6psi at 2k, ~9psi at 2500, etc all the way to ~16psi at 7k. It is how the blower works, the higher the rpms, the faster it spins and the more air it moves.

Jesus I didnt know you have a TVS.. Yeah but I always thought that as the blower's revolutions increased, as did the engines, therefore the engine is demanding more air at the same time, balancing the increase in blower speed.

If that was true then you wouldnt be "supercharging" the cylinder and you would never see any "boost".

think about it this way
2000rpm engine speed, blower speed is X with 3PSI
increase engine speed (Blower speed will GO UP)
5000rpm engine speed, blower speed increases thus causing it to compress more air thus meaning more boost. my car hits 6PSI at WOT then about 3500hits 10 then creeps up to 12-13 pending outside temp



JBO since July 30, 2001