Strange LMAF Issue

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panabax
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Strange LMAF Issue

Post by panabax » Fri Dec 04, 2015 4:45 pm

I am tuning my '96 Bronco 5.8 with BE and a Mongoose. I use Core Tuning's AGANF strategy. I have a custom intake which mates an Eaton M112 from an '04 Lighting w/intercooler to my 351W. I am running 80# Deka injectors.

I have the published numbers for both the injectors and MAF. Neither have actually been flow tested by me. I am using the entire Lightning intake from the base of the SC to the inlet of the MAF. I have a Specter cone filter hanging off the inlet of the MAF.

If I plug in the LMAF transfer function so frequently cited on this site and the published slopes for the 80# Deka injectors, the engine is so rich it will not run. In order to dial the AFR in using my wideband, I have basically cut the MAF transfer function in half. That actually makes the transfer function lower than the stock transfer function for this truck. I have run like that for the past year on my old motor without problems. However, I have a new motor running now and I would like to correct this problem and it is a problem. "Scaled" like this, my truck sees a maximum load before boost of only about 28%. Now that my new motor is in, I would like to really dial in my fuel and then my timing but my load numbers are stupid low. I have tried scaling the injectors, but there is not enough room. The slope maxes out at about 120. The low slope on these injectors is already 110, so I cannot increase it enough to get the AFR down.

Does anyone have any ideas why I would be SO rich? Is there a multiplier somewhere that could be throwing the tune off this much? I simply can't understand why, with published numbers for both the injectors and the MAF, I can't get it to run unless I scale the MAF by 50%.

Any help would be greatly appreciated. Thanks.

Baxter
'96 Bronco, 351W, Trick Flow TWFAC 170 Heads, Eaton M112 SC, Comp Cams 35-306-8, Lightning 90mm MAF, 80# DEKA injectors, AGANF EECV, EDIS w/ Megajolt

decipha

Re: Strange LMAF Issue

Post by decipha » Fri Dec 04, 2015 6:13 pm

yeah something is definitely wrong, it shouldn't be anywhere near that far off at all

have you verified fuel pressure is 40psi with the vac line off?

what is your mafv at idle and at wot ?

panabax
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Joined: Thu Jun 19, 2014 12:27 pm

Re: Strange LMAF Issue

Post by panabax » Fri Dec 04, 2015 6:39 pm

MAFV at idle is about 1.2v. At WOT (supercharger on but not hooked up with belt - so zero boost) 3.3 volts. I have the supercharger unhooked right now because I am trying to establish a baseline VE which is what led to all this hubbub.

According to the pressure gauge on my regulator, the pressure is 39psi with the vacuum line disconnected. Something is clearly wrong. In no particular order of likelihood:

1. The MAF is screwed up and reading way low. This doesn't make sense because the load numbers support that the MAF transfer function is driven too low suggesting the MAF is not the problem.

2. The injectors are screwed up and putting out way too much fuel. I don't know how that could happen unless . . .

3. The pressure gauge is screwed up and reading way too low and I actually have the rail pressure jacked way up and don't know it. I'm not sure how likely that is either. I'm also not sure how to test it. I guess I will need to attach another pressure gauge directly to the rail. Of course, it's an after market rail. It does not have a pressure hookup (though it does have unused connections). What a PITA. I was really hoping I screwed up a global air charge multiplier or some such.

Any other ideas? I really do not want to just throw parts at it. These parts are expensive.

Baxter
'96 Bronco, 351W, Trick Flow TWFAC 170 Heads, Eaton M112 SC, Comp Cams 35-306-8, Lightning 90mm MAF, 80# DEKA injectors, AGANF EECV, EDIS w/ Megajolt

decipha

Re: Strange LMAF Issue

Post by decipha » Fri Dec 04, 2015 6:50 pm

your mafv is perfectly in line with what i expect it to be

its definitely a fuel issue and not air

can you take a stock tune and copy over your maf transfer and 4 injector parameters to verify its nothing else screwy in the tune?

post back with the maf transfer from the stock tune

panabax
Gear Head
Posts: 30
Joined: Thu Jun 19, 2014 12:27 pm

Re: Strange LMAF Issue

Post by panabax » Fri Dec 04, 2015 7:42 pm

That is a great idea to rule out any tuning anomalies. Unfortunately, when I tried to write the stock tune to the EEC, BE did not recognize it as the same and wanted another token. I will have to sort through all my tune files and see if I have another stock file that will write without a token. Otherwise, I will be forced to do a compare to the stock tune and make all the changes back manually. OMG.

Baxter
'96 Bronco, 351W, Trick Flow TWFAC 170 Heads, Eaton M112 SC, Comp Cams 35-306-8, Lightning 90mm MAF, 80# DEKA injectors, AGANF EECV, EDIS w/ Megajolt

decipha

Re: Strange LMAF Issue

Post by decipha » Fri Dec 04, 2015 10:20 pm

yea that token crap really sucks it limits you from doing diagnostics unless you want to spend $50 to test it out

good luck with it, your gonna need it

panabax
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Posts: 30
Joined: Thu Jun 19, 2014 12:27 pm

Re: Strange LMAF Issue

Post by panabax » Mon Dec 07, 2015 11:10 am

Well, it was a busy weekend, but I was able to do a little more troubleshooting. The problem is clearly a hardware related fuel issue. I suspect I may have a bad fuel pressure regulator. I have set the regulator to as low as it will go. The gauge on the regulator reads about 15 psi with the vacuum pump removed. At that setting, and using the flow tested LMAF curve, the AFR gets very near to correct. It is still rich, but very drivable. I ended up setting both low and high slopes on the injectors to 100 and it got VERY close. I then tweaked the MAF curve slightly and not I am in closed loop running just as expected, except for the fact that my regulator shows 15psi.

Either the regulator is toast, the injectors are really 300# injectors or there is some restriction in the return lines. I plumbed the fuel rail myself with steel braided hose, 8AN on the supply side and 6AN on the return. The supply line splits and feeds each of the rear of the two rails with an 8AN line then a 6AN line comes off of the front of each rail and feeds into the regulator which, in turn, returns the excess fuel to the fuel tank. Have I plumbed it right?

I really need to get a pressure gauge on the rail itself, but I have not had time. That would answer the question for sure.

Baxter
'96 Bronco, 351W, Trick Flow TWFAC 170 Heads, Eaton M112 SC, Comp Cams 35-306-8, Lightning 90mm MAF, 80# DEKA injectors, AGANF EECV, EDIS w/ Megajolt

AussieSOHC
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Posts: 12
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Re: Strange LMAF Issue

Post by AussieSOHC » Fri Mar 31, 2017 10:42 pm

Yes this is an old thread but it was left open and I have some info that will help.

DEKA 80 are BIG and in some versions of the software the slopes present a value outside what the SW thinks is suitable.
Or overflow of a variable causes double of the fuel calculation.

The solution is to Scale: that is halve the MAF, halve the slopes,halve the displacement and all is well.
All the load numbers now look sensible the load related tables are indexed correctly.

It happened when I used them on my mechanical returnless system which infers the pressure drop across the injector by calculating the pressure in the manifold.
4.0 SOHC V6 (2005 Ranger) | SCT X4 | FBHO (PYCN0) | MPx90-MODDBOX | 80#[M-9593-LU80] | [Epman] gss340 255lph | 91% MAF Scaling | Thermal Coated Pacesetter Headers | 2.25 engine pipes single 2.5 exhaust

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