Hi Folks,
I have an 89 gta with the 5.7 in her..Motor has been rebuilt with all eagle products on the lower end.compression remains stock..Heads are the stock 083 cast ..has the comp 2032 cam , shorty headers , borla catback exhaust..I put a set of bosch 3 24lb injectors in it..I de screened the maf..160 thermostat and fan switches..Hypertech comp..OK My question is, Now that i have put the bigger injectors in it should i buy a junkyard ecm and send it to Fastchips to have a custom tune on it..Or will the ecm i have recognize the injector difference without me spending more money...P.s my fuel pressure is set at 47...
Thanks in advance

 

Yes,

Your car is probably running rich since the injector constant that has been set in the computer is for 22 # injectors. The MAF system can compensate for some modifications, but a wide band tune would help a lot.

 

A couple of things require a tune...

First of all you have a MAF TPI which means it will compensate for certains mods, to a certain extent.

For example, de-screening the MAF will require a tune. There is a thread on here explaining how to get the MAF to read air properly after descreening it. Check it the DIY PROM section.

Changing the internals won't make much difference if they are not changing compression or the bore/stroke (it's still a 350ci 5.7L). BUT you changed the cam which means you might have to tune the idle to get it to not idle rich or lean (depending on what the engine is doing). You could probably gain a bit of power on the top end as well from tuning the fuel (via MAF tables in tuner pro) and perhaps playing with SPARK ADVANCE in the PROM (not on the distributor).

As Saculia said, changing the injectors from 22lbs to 24lbs alone will require a tune to change the injector constant in the PROM from 22lbs to 24lbs (this is actually fairly easy to do once you're all setup for tuning).

I recommend that this be posted/moved in the DIY PROM section because you will get more help from the guys over there. Also, for more info read all the stickies in the DIY PROM section pertaining to tuning if you are interested in gaining more knowledge on this subject.

 

to keep it simple, when you change your hardware, you gotta change your software

 

That depends on the hardware You don't always have to change the tune because the MAF compensates well with mods, unlike speed density systems that need a tune every time.

 

Thanks guys i appreciate the input. I went over to the diy section alot of interesting reading there..I wish there was a cheap way to tune these things...