So I've come to the conclusion that im gonna go back down to 42 pound injectors but i want to keep my 2.7 inch pully. now ik this is where the debate comes in. heres my logic, looking for someone to either back me up or inform me otherwise. with a 2.7 pully i should be round 18 psi. heres the thing i have a catless dp, and a ported supercharger. ill have a ported head by the time this winters over. with all the lack of restriction i know i wont be up at 18 psi. when i had the catless dp on i was only hitting bout 16 psi yet it pulled harder then my stock one back on at 18 psi. so im thinking with the ported head i should be at least another pound or two less. so with less pressure and air flowing more smoothly do you think i could get away with 42# injectors without them going static.

 

logic makes sense to me

 

your still flowing more air. Remember psi is just a measurement of resistance

 

if you flow more air your car will have to compenstate with more fuel to command the same afr. Change the pulley if you don't want problems down the road. 2.9 is the smallest i would go on 42's.

 

Just because your car has less restriction now doesnt mean your not flowing the same amount of air. You still have to add the extra fuel to keep your afr where you want it. Which means your still going to need the 60's. Now you dont have to use 60's you could go with something a bit smaller but like lsjwannabe said, 2.9 is the smallest i would go as well on 42's.

 

eh. well see. iknow CA sells a kit with a 2.7 and 42s but i also know that its not the best idea. well see.

 

trust me im one who likes to push the limits with my car, but i would not do something like that, just buy a bigger pulley or buy 60's. CA is dumb for doing that and probably has some pissed customers that blew up.

 

I believe thats a mixup. I remember someone saying that kit actually comes with 60s but they never fixed it on the site. And i believe their 2.8 pullied kit also comes with the 60's.

 

already have 60s and im guessing you meant smaller pully with 60s and bigger with 42s

nope got there kit along time ago. it comes with 42s and a 2.7 pully.

 

then why do you want to go back down to 42's

 

cause i was going for power. but know i dont care. got my hands on a 75 stingray. so thats going to be my all out power car. so turning the cobalt into more of a show car. im just turned off right now with the 60's because of the fact i lost almost 100 miles a tank when i switched. not worth it to me on such a small tank. im more annoyed then anything on how often i have to fill up. prolly gonna go to a 2.8 with 42s like italian joe. we basically have the same exact setup nitrous and all. if only we werent seperated by almost 30 hours of driving lol.

 

by adding exhaust mods you are lowering your PSI.
but that doesnt equal lowering your fueling requirements.
in fact likely the opposite.


PSI is not directly proportional to Injector Duty Cycle.
2.8 is pushing it.
2.7 is a blown motor, it just doesnt know it yet.

 

thats in your tune and right foot then buddy, i run my car hard and i get 23~26 mpg all city driving. Im making more power and dumping more fuel to trust me go over your tune and im sure something is wrong. I get better gas mileage then i did stock

 

Most of the posts in here I agree with. By haveing less restriction you lower PSI and flow MORE air. When you flow more air you need more fuel not less fuel. Just remember this - anytime you are making more power you need more fuel.

 

not my right foot at all. i drive fairly conservative. i think its my tune. im throwing a 172 code. its too rich so im pretty sure thats gotta do alot with my tune. not a 100% sure though.

 

are you close to anyone with hpt? get to them and have them log the car to see whats going on, im sure its not to big of a fix

 

i've had it tuned by smg autosports but hes too far away. im gonna order hptuners and me and a feiend are going to tune it. dont worry i've got the experience tuning a little myself and plus my friend thats gonna do the majority of it has been working with hp, emange, and aem standalone units for the last few years. ill try the tune with 60s and see from there

 

may wanna check your tune then... with my 60# and 2.8 i get about 37-38 mpg highway @ 80mph and then 28-30 city

 

^do me a favor then. next time you fill up tell me how many miles you get on a tank.

 

more air requires more fuel.

 

may be a stupid question, but your car did get tuned when you dumped the 60lb injectors into it, right???

 

no why should i have lol.....no seriously should i have.....yea i had it tuned by fred from SMG autosports. i changed the injectors up at his shop

 

Holy crap thats good mpg!

 

i get the same thing. it's not hard to do. if you know where to look. you can see how i did it.

 

If I am good I get 25-30 on average.... If I drive more highway than city I get that!

Which I don't 95% of the time for me I usually see 22-25!