hello, i have an issue which am loosing boost at around 5500 rpms to shifting time, from 16-17 psi down to about 11 psi. does anyone know why this might be happening??
year :2006
cobalt ss s/c
yellow
Mods: 779 pulley, stage 2 belt, cold air intake, heat exchanger. no injector upgrade yet.

 

What size pulley?

Are you using the stage 2 belt? It's possible you're belt is slipping over the supercharger pulley causing it to not spin fast enough. Hence the loss of boost pressure.

 

were going to need some more information, we are not mind readers. Year, make, model, mods, color just for the hell of it and anything else you can think of.

 

hey guys yea I was in his car the other day and around 5500 it drops from full boost(16) to about (10-11) n just stays there n when u shift gear, it gets full boost again n then drops again. He does have the stage 2 belt on it

 

what kind of tune are you running on the car? could be that, or maybe something to do with a sensor.

 

the big question

are you noticing any power loss?

 

Car has stock tune, but it's weird becuz with stage 2 pulley I don't think ur suppose to boost 16-17

 

he just said no injector upgrade? did i read that right? and a 77.9mm pulley is stg2 on already maxed out factory injectors?

 

x2 could be a faulty boost gauge if your not losing power!

 

oh god, stock tune and stg 2 pulley? :palm face:

 

N the car does lose power

 

it's his car telling him he's an idiot, and is about to blow up. take the pulley off immediately, or get a tune and bigger injectors. he'll be lucky at this point if there's no serious damage done. i sense a "help, my car won't start" post very soon.

as far as the high boost #'s, could be a clogged cat, or if he's running on stock exhaust that will give him higher boost #'s.

 

Stock tune! Stock injectors!

 

*facepalm*

 

yea, that's great. his engine is gonna pop. it's probably already fucked.

 

Nuthin is gonna happen to his car becuz I been running my car with 42 lb injectors on gm tune n a 2.7 pulleys n nitrous for about 2 years almost n my car runs fine n hard and I race my car like almost everyday.

 

Stage 2 injectors > stock injectors.

 

yeah thats cool. tell that to my motor that just popped thats tuned and has proper injectors.

thats just stupid dude im sorry, it just is theres no other way to say it.

 

They are only 35# iirc... which is not nearly enough for a 2.9.

 

probaly cus your taken forever to find gears and your car gets sick of waiten on you and just goes to sleep

 

Wow... just wow. You shouldn't be modding your car if you don't understand the basics of a gasoline engine. Let me put it this way.

AIR + FUEL = GO

AIR + NO FUEL = A tow truck dragging your car to the shop.

Get 42s or 60s, and a proper tune. Don't be ******* cheap.. You either do it right and pay a bit more, or you cheap out now and you pay a LOT MORE for it later.
Those injectors you have in there are maxed out way before you hit 5500... you're just killing that engine.

 

keep telling yourself that. you can't always tell that damage is happening. don't take this the wrong way, but neither of you understand basic modding concepts. if you think STOCK injectors can handle a 77.9mm pulley, not for nothing, but you don't know anything about the stock injectors. then your friend makes a post and says "the car is loosing boost" we tell you that what he's doing is very, very bad, and you just say "no, it's not a problem running a small pulley on stock tune and injectors". so what kind of answer do you want to hear?

at least you have bigger injectors and a tune. your probably doing damage to your car as well, but not as much as your friend. but if you think it's safe to run a 2.7 and nitrous on 42# injectors and nitrous, you really, really need to do more research. your car is most likely not in as good condition as you think.

 

am getting the injectors this weekend. so u people think thats the problem...well thankfully nothing has happened to it cuz i dnt run it as much but ive had it that way for about a year n nothing has gone wrong with it but thanks for all the comments anyways... any other suggestions???

 

I really don't car I make the car run hard n if it blows, it's blow I take motor out n build it n come bak running harder

 

let me rephrase that... nothing has gone wrong THAT YOU KNOW ABOUT.

bad, bad idea. Honestly I would stop driving the car. and your friend too, with the 2.7 & nitrous on a stage tune.