to big of injectors?
Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
to big of injectors? I've been having issues with idle that my tuner cant tune out. I believe it may be something mechanical. I installed an msd atomic airforce intake, 102 tb and a tsp maf. along with 78 lb/hr injectors. The issues only happen at idle and no throttle the car runs very rich 12 afr rich... The injectors are 78# at 42 psi, I believe they are around 90# on 58psi that my stock pump runs. would too large of an injector make the idle that rich and erratic, Surging and stalling? Cruising and letting of the throttle also causes rich afrs then lean tip when I get back on the throttle immediately sometimes causing a misfire or sputter. I have a set of 62# at 58psi injectors I can buy but want to make sure I'm not wasting money to have the same issues. I've heard a good tuner can tune large injectors to run like stock but im still not certain. would ipw adjustments help idle with out messing with any part throttle or wot fueling?
Depends on the injector, and I've never heard of a 78lb injector before so you will have to be more specific. Larger injectors very commonly ride their minimum pulse width at light part throttle cruise and decel so it's normal to have many types of larger injectors be rich in those areas. Of course it could be tune related as well by not modifying your minimum allowed pulsewidth or having injector data that is not modified correctly or accurate. Without a tune file posted and without knowing what kind of injectors they are specifically it's anybody's guess. I would have to question why you put such large injectors in what is essentially a heads/cam car however. You surely won't use the full dynamic range of that large of an injector with your combo.
Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
Depends on the injector, and I've never heard of a 78lb injector before so you will have to be more specific. Larger injectors very commonly ride their minimum pulse width at light part throttle cruise and decel so it's normal to have many types of larger injectors be rich in those areas. Of course it could be tune related as well by not modifying your minimum allowed pulsewidth or having injector data that is not modified correctly or accurate. Without a tune file posted and without knowing what kind of injectors they are specifically it's anybody's guess. I would have to question why you put such large injectors in what is essentially a heads/cam car however. You surely won't use the full dynamic range of that large of an injector with your combo.
If your math is right about 78# at 42psi and 90# at 58psi, then 1.0ms minimum PW will definitely give a rich idle. I'm guessing these are high impedance injectors, and may be untuneable at the short pulse required for low rpm operation. It also sounds like you may end up needing to adjust some DFCO values, but I would definitely look at injectors first.
Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
If your math is right about 78# at 42psi and 90# at 58psi, then 1.0ms minimum PW will definitely give a rich idle. I'm guessing these are high impedance injectors, and may be untuneable at the short pulse required for low rpm operation. It also sounds like you may end up needing to adjust some DFCO values, but I would definitely look at injectors first.
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Thread Starter
Staging Lane
Joined: Jul 2014
Posts: 95
Likes: 2
From: Northern Michigan
For what it is worth we changed the injectors to a set of 65# at 58psi ls3 style injectors and the issue disappeared. no more rich cruising or idle, still some lean tip but we still haven't tuned the car yet. bank 2 ltft are 10-20% higher than bank one though. i will be changing plugs to see if that will help.
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