Here's the deal. I built a 3.4 Whipple Crusher '03 Cobra (60lb SD injectors, OEM Ford slot style MAF, return style fuel system) and I'm trying to get it running right. I built a base tune (SCT PRP) with forced open-loop and it fired right up. Just runs rich at all RPMs. So I thought no problem, I'll adjust the MAF curve accordingly to command less fuel. But it runs at exactly the same AFR and nothing changes. It runs as rich as 10.8-11.5:1 at any RPM from idle on up. I noticed that it leans out on tip in, but stabilizes at the after mentioned rich AFR as soon as the throttle stops moving. Then it'll get super rich when I tip out! Almost like it's backwards lol. The ONLY thing that changed the AFR was backing off the fuel pressure, but I had it set at the standard 40 psi base pressure with the car off. So I was thinking maybe the injector settings were way off, but I used the latest SCT value files for ford racing 60lb injectors and scaled the breakpoint and slopes accordingly with the MAF, so I don't know what could have gone wrong there. I've retained the FRPS so there should be feedback to the computer to adjust pulsewidth for pressure drop variations. The AFR is similar bank to bank, so I don't suspect a bad injector. All the sensors seem to read correctly when I data log. Needless to say it's frustrating and I can't figure it out. It's like something is overriding the MAF transfer function but I don't know why that would happen. I'd really appreciate some input! Let me know if you need more info.
AFR not responding to tune changes!
- Thread starter xtreme_exploder
- Start date
What else was done? Aftermarket cams? Did you make the changes needed for the return style set up?
Figured it out! Engine is stock, save for the pistons. Yes the changes were made for the return style. So I set the scalar "ACDC Switch" under the MAF section in SCT PRP to 0 from 1. All it says in the software is that it's a "switch to turn on/off ACDC transient fuel compensation". I'm not sure exactly what this function does; I haven't found any information in my searches. What does ACDC stand for? The only thing I can surmise is that it enables use of the Load w/ Failed MAF table. But idk why it would mess with steady throttle position AFR like it was. Anybody have knowledge on this item?
This is information that is not widely know for mysterious reasons, but make sure you are deleting tune files off your sct device prior to loading new ones. What can happen (because it's software) is it may just make changes to the old file. It's called hybrid tunes. Very bad.
I personally had this experience tuning a 2013 SHO with sct x3 device. fyi
I personally had this experience tuning a 2013 SHO with sct x3 device. fyi
That's weird. I've never deleted old tunes before loading them on my Xcal2. The newer hand helds seem to be a lot more finicky.
I did delete all my old tunes out before I uploaded my new tune. Figured there's no sense in having tunes on there for a setup I don't have anymore lol. I'm also running a trusty ol' xcal2.
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