i am buying 42lb injectors and im wondering if i have to do a bigger mass air flow as well if so what size is reccomended? 90mm? i have a 70mm tb

 

No, you do not need to upgrade your MAF simply because you install bigger injectors. The computer will need to be tuned for the new injectors though.

You might need to upgrade your MAF depending on how much power you are putting down. I'm assuming there is a good reason for the new injectors, most likely a blower. In that case, you will need a bigger MAF around 400rwhp.

 

What mods do you have that make you believe need higher capacity injectors?

As to the stock MAF on your '04, it's good to over 2700 lb/h which at 12.5:1 AFR = 216 lb/h of fuel. which running n/a = over 432 flywheel HP.

If you want to spend money, open up the exhaust and then buy a tuner...

 

I have 42's with a 75mm tb/plenum, and stock maf. At my power level it works fine.

 

hey i have heads,cams,rods,bored .30 over,headers,tb,exhaust cam...et cfull bolt ons plus heads and cam and its tuned on sct now and im running 90shot of nitrous im upgrading to a 125shot and buying 42lb injectors and a 90mm mas air. will i need the mass air? when parts get here i am having SGS tune my car

 

Probably not, however it's easy enough to find out--just data log the MAF kg/h and if it goes flat at 1200 kg/h or so then you are pegging the MAF.

BTW--1200 kg/h = 2640 lb/h, at 12:1 AFR you'd mix 220 lb/h of fuel with that air, running n/a and assuming BSFC of 0.5 lb/HP that's 440 fwHP...

 

ok thanks and my sct tune is just the chip? how can i data log it?

 

If you are having someone else tune the engine then just let them make the decision-they will have the equipment to data log and make sure the MAF is not pegging...