Airman21

what is the problem with having 24lb injectors on the 4.6's? i heard i cant do it unless i have the maf dyno tuned? i put 24lbs in and the engine light hasnt come on so i guess i am just confused why we cant use them? my friend said it should be fine but i am worried it wont be cause i am told other wise on this forum can someone please tell me why it is bad to use 24lbersand if i do what will happen to the car if i dont get it dyno tuned? run crappy? loss hp? thanks

John

LetThePoniesRunFree

Curious, why did you feel the need to change to a larger injector?

You do not "tune" the MAF. Youre-program the ECM for drastic changes that the factory programming can not compensate for. Like larger injectors.

Airman21

i had to take out the old injectors and when we did that we notice they were real rusty and looked like crap and since i had already upgraded the fuel pump thought why not upgrade the injectors then i was told i shouldnt have done that... so what is the problems i will have if i dont reprogram the ECM? thanks for the quick responce

LetThePoniesRunFree

If it was me, I'd either put 19lbers back in or have the ECM programmed for the 24's. The car is just going to run really rich and not perform like you think it should. The ECM still thinks you have 19lb injectors and isn't going to be able to adjust the pulse width far enough to compensate for the larger injector. If you're in the market for a tuner, (here comes the shameless plug), contact Don at Lasota Racing Technologies. he'll hook you up.

Airman21

ok i will talk to my buddy about that

Airman21

would a hand held tuner work?

LetThePoniesRunFree

Soyou have currently a MAF and injector combination for 24-lb/hr injectors, and you installed that into an original 19-lb/hr setup, with no other changes. You can get an aftermarket MAF "tuner" and it somehow magically works without having to reprogram the ECM. How it really works is by fooling the ECM. The recalibrated MAF sends roughly2/3 the voltage signal to the ECM, causing the ECM to "think" only2/3 the air is flowing into the engine. If there's only2/3 the air, then only66% of the fuel flow is required, so the ECM will command roughly2/3 the injector pulse width. This works out fine with the 24-lb/hr injectors because they flow about1 1/3what the 19-lb/hr injectors did, and in the end, roughly the same amount of fuel still flows into the engine. The problem with this approach is the inaccurate load calculation, which can screw up the spark advance and desired A/F ratio. In theory this technique sounds great and there are many manufacturers out there that would love to sell you their product to "tune" your MAF. Coughghghghghghgh, Diablo, couuugghhh.But there really is no substitution to properly tuning the ECM.

LetThePoniesRunFree

Absolutely.

You have to understand though that the company/person you buy the hand held from has to pre-program a tune(s) on it before they even ship it out to you. Those so called "canned" tunes can get very close but there really is no substitution for a tunecreated with your caron a dynometer.

Airman21

ok thanks for the help i am going to pick up my car from my buddies today when i go to work and drive it to work and back and see how it does if it seems weak or runs bad i will have him put the 19lb back in

01Steed

Regardless of how it "feels", you need to correct the issue.