help with keeping a9p in closed loop

Anything about Ford EEC tuning. TwEECer and Moates questions dominate, but there's some SCT and OBD-II knowledge too.

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area302
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Location: Maryland

help with keeping a9p in closed loop

Post by area302 » Fri Nov 10, 2017 12:13 am

I have an 1991 gt a9p installed in a e250 van.aod trans, 3.73 rear, quarterhorse, wideband.
Runs great, but what basic adjustments or scalars should I focus on to keep it in closed loop more?
I know the weight of the mustang compared to a 7400lb van is probably the reason, just not sure on adjustments.
1991 ford 302 gt mustang a9p, aod, moates quarterhorse,BE, EA, Innovate MTX-L
wideband, dataq di-145, gibson stainless exhaust, 3.73 rear.

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cgrey8
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Re: help with keeping a9p in closed loop

Post by cgrey8 » Fri Nov 10, 2017 7:11 am

I don't know this first hand, but I've heard from others here on the forum that it was/is common practice for Ford to run trucks Closed Loop all the way to WOT, which saves gas and improves HC/CO emissions, but doesn't give the best performance. The common tweak to truck tunes is enable an Open Loop WOT condition with more performance-oriented WOT AFRs.

In your case, even if you do maintain an Open Loop WOT, you probably still want to stay in CL a bit higher in the Load range before forcing OL given the weight of the vehicle.

Can you give us more details on the engine? For example:
CID?
Is it stock?
H/C/I mods?
Boosted?
etc

So the first thing I'd look for is the TPS scalar(s) that force OL based on Throttle Position. Up those to "near" WOT voltages to hold you in Closed Loop longer.

I don't remember if there are any scalars or functions that force OL based on Load, but it seems there is. I would think those would be prefixed as Fuel.

I'm sure others will have more specific info. I just don't have my laptop in front of me to go digging and getting more specific info.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA

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area302
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Posts: 19
Joined: Wed Mar 04, 2009 8:04 pm
Location: Maryland

Re: help with keeping a9p in closed loop

Post by area302 » Sat Nov 11, 2017 7:54 am

306ci, stock 1991 truck engine converted to mass air.
using maf and plumbing from a 1996 van.
only year ford made the 5.0 vans mass air.
a9p ecu.
does have the truck cam that matches the maf meter 1996.
roller cam and ford cobra 1.7 roller rockers.
your suggestion helped with the tp adjustment.
I completely forgot to check that.
I also picked up Don Lasota's book for tuning with moates and BE.
I'm starting to get the hang of tuning it, and can get good results.
had to pull a ton of timing out as heavy as this truck is.
The a9p is way to aggresive with the timing.
Thanks for the help.
1991 ford 302 gt mustang a9p, aod, moates quarterhorse,BE, EA, Innovate MTX-L
wideband, dataq di-145, gibson stainless exhaust, 3.73 rear.

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