I have stock pulley and etc. on the Cobalt.

What's the boost at on the stock pulley?
I've heard 12.5 or something along those lines.

Is this the MAX boost possible on the stock pulley, or is the BPV bleeding some off? I want to tune for some 42s but I'm not going to waste my time if I can't generate more boost.

And FYI, no recommendations to get a smaller pulley. Pulley size will change my class in AutoX and I'm not trying to race in street mod.

 

ya it runs about 12

 

12.5 MAX psi at sea level.

It will vary depending on engine speed, load, and (of course) # of feet above/below the ocean.

 

im only hitting about 13psi on 2.8 pulley and 60's, why?

 

^^maybe bc your a 2.2 and have lower compression
just a guess tho

 

many things affect boost, more boost doesn't necessarily mean more power.

and to answer the OP's question: pretty sure the biggest injectors you wanna run on stock pulley is 39#, and this will give you more power. but i don't think it increases your boost

 

Does it run about 12psi or is possible to over that amount? I'm clueless to if the BPV is bleeding it. =(

I know this, but in order to get more power out of 42# injectors with out changing pulley sizes, you need to be able to create more boost.

 

i edited my first comment.

 

Its because your a 2.2 stock pulley you have 9lbs or so,
So 13 on a 2.8 is normal for you

 

sub'd

 

i've heard 12 or 13 for stock boost. but i've had a couple ppl tell me they've seen my car hit 14 or 15lbs on a night with a good low air temp. i've also noticed during colder nights in the summer or fall nights when i go out with friends it pushes more towards 13.5lbs. call me crazy but just saying what i've seen happen in my car.

 

Just get a custom on the stock pulley so you can rev to 7000rpms and turn off torque management. Then above 6000rpms or whenever it is the BPV wont bleed out your boost. It wont make a huge difference but it will help out

 

I only see about 10lbs but I have a header/dp/catback on an otherwise stock car.

 

At this level of boost, does it max out stock injectors?

If so, at 12.5, I might as well increase airflow. I.E. Non-restrictive filter, ported charger, wider TB, ported intake mani, etc.

 

Don't port anything, you'll just ruin it. If anything have the head professionally ported.

 

Looking at less inexpensive options. Ported head is way too much work and will put me with out a car.

Porting either of those will not be detrimental if tuned correctly, and ported correctly.

 

Whatever you say.

 

12.5 is stock you can 42lbs injectors just need to tune for them the stocl injectors are close to being maxed out at 12.5 lbs if you want to help your performance do exhaust and cooling mods

 

I'm in the stock AutoX class, so I'm limited to what I can do.

Exhaust is a given. I have a set of 42's, and was looking to use them in some way.

I can't even have a CAI or I get bumped =(

 

wat about modding the stock airbox will that bump you

 

can you change you crank pulley running a larger crank pulley will up the boost a little
and a tune will give you more power by adding timing a leaning it out

 

I believe i was at like 15 with stage 2 and 42lbers. but then again im in colorado, mile high baby! lol sike, altitude sucks for racing!

 

I'm sure you can get some 42lb/hr injectors w/ a custom tune, and be fine for your AutoX class. GMS1 is 42lb/hr injectors, and the same tune as GMS2. You may want to look into that if you want to bump up the power a bit w/o messing with pulleys.

 

do 42s and a tune 235 240 crank should be more then doable the gm tunes suck

 

Right. That's what I am talking about. But I know from people who have dynoed on the GMS1 with diminishing returns. Like a 5HP gain, primarily because they weren't creating enough boost to really put the 42s to work.

And I already have a set of 42s, just looking to see what the best route would be in trying to make them useful.

You can only swap air filters with the airbox. You cannot change it in any way.

About the crank pulley, I'm not sure. I'd have to check. Didn't really think of that.