I recently bought a 2006 cobalt ss Stage 3 supercharged. I bought it with a hole in one of the pistons. I replaced the piston and gaskets for about $300. The car was making about 20 lbs of boost. I put about a thousand miles on the car and then one day when I was pulling onto the highway I hit the gas and I heard metal spray from out the bottom of the car. I took the car home I sent the number 2 rod through the engine block. Prior to this happening I noticed that the engine had a lot of blow by. there was a puddle of oil in the intake and my dipstick kept blowing out of the tube. Why did it blow up?

 

Knock.

 

Isn't 20 pounds of boost way inefficient for the stock supercharger?

 

Yes, extremely so.

It sounds like either the intercooler pump wasn't working or here was WAY too small of a pulley for the setup on there. Or both.

You never want to be on 20 pounds on the m62. Usually 12-17psi is where you always want to be.

 

what mods did you have?

pulley size? Who tuned it?

Where you logging your IAT2 at any point to make sure it was ok?

 

You bought a used car with an engine that was already modded and beat on by the previous owner. There was a reason he sold it and sadly you found out the hard way what that reason was.

 

yeah that sounds like a disaster. 20lbs on an m62? www. heatcity dot com

 

This. Your $300 fix wasn't the right way to go.

I ran 19psi on my 2.6" pulley M62 meth set up without issue. Boost is just a measurement of restriction. But a "stage 3" set up shouldn't make 20psi.

 

well, if you really want some help with it you are going to need to post some more info on the engine setup so we can figure out whats going on. pics of the engine bay will help.

and $300 wasnt enough to properly fix a piston with a hole in it. im gonna guess you reused the head bolts (a big no-no) cause they are close to the total of what you spent.

 

Bolts are not any where near $300. The piston was $60 for a used set. And a new timing chain was around $100. I was just asking if the blow by could have blown it up. It is now going to be swapped with a saab 9-3 engine.

By the way the car was only $600 with 60 k miles

 

thats rediculously cheap price for what all is there. wow, so i stand corrected lol.

the blow by could possibly contributed to it. id bet the rings didnt seat and you were burning oil, and burning oil causes detonation. detonation hammers rod bearings, and that can result it throwing a rod out of it.

im more interested in the 20lbs boost. does the car still have a cat? aftermarket exhaust? what pulley is on it? any clue what injectors it has? id hate to see it all happen again with another engine.

 

Okay it was definitely burning a little bit of oil. But it had a lot of blow by. It has the 2.6 pulley with the bpv disabled. that could have contributed to my problem.

 

also it had 60lb injectors and no cat zzp exhaust and header

 

does it have any cooling mods? id drop that pulley back to a 2.8 or 2.9 and hook the bypass valve back up just as a start and go from there

 

It has the zzp heat exchanger and the stock heat exchanger with a inline intercooler pump the stock pump was dead.

 

id think about a dual pass end plate and "option b", easy mods while its apart.

like i said, id turn it down till you make sure the tune is safe. the saab engine has different cams than the lsj, so the tune may need to be modified.

 

a "stage 3" set up shouldn't make 20psi.


^^^^^^^^^^^^^^^^^^^^

This

 

Sounds like the catalytic converter is plugged up.

 

Yes I'm planning on using a megasquirt ecu with a bigger turbo or taking it to zzp for a tune

 

no reason to use a megasquirt, in fact i can think of a lot of reasons not to. the factory ecu is leaps and bounds above a megasquirt as far as technology goes. the stock ecu will give far better cold start, driveability, fuel economy and diagnostics. its also fully tuneable with hp tuners. dont get me wrong, i like the megasquirt, ive done several cars with them in the past (have an ms2 sitting beside my desk), and in the right application they work great, however i see using one in a cobalt as a step in the wrong direction.

if your close enough to zzp where you can take the car to them to tune, do it.

 

What piston had the hole in it? was it the same one that the rod let loos on?


If it had a hole it probably had some detonation going on and this wrecks havoc on rods/rod bearings anyways. Sounds like the damage was already done and you just put a bandaid on the first problem only to discover the second one.

 

I agree with your comment with the stock ECU being a better option than a megasquirt. In terms of tunability HPTuners has only provided access to the "tip of the Ice berg." Basically most bulk things you will need to adjust are accessible like spark map and a few modifiers for example. But a typical Bosch ECU can easily have well over 20,000 tunable variables and maps, yes 20K+. But in terms of the project at hand, I agree, keep the stock ECM, it will be more reliable and you will be able to keep fault reactions and diagnostics.

 

This is actually quite a problem with these cars, especially in the rust belt. My opinion would be to investigate the intercooler pump from a 2016 Polaris RZR Turbo. It is a brushless rig and way more reliable than the cobalt one. I am not 100% sure on wiring but, it will outperform the cobalt one in every aspect except weight.