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

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sailorbob
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Severe leaning problem under boost

Post by sailorbob » Thu Mar 08, 2007 7:21 am

Got a little problem here that I cannot figure out for someone and I have that annoying feeling I'm missing something very obvious. The car is a turbocharged 4 cylinder.

The problem is a severe leaning issue under high loads; the AF ratio is 11.5:1 at 4.7 volts/24psi boost at 5000rpm but leans way out to 14.9:1 at 4.9 volts/24psi at 5500rpm. It's reportedly like a switch.

The stock MAF's transfer table is scaled to 5.00 volts as standard but the MAF_Max_A-D_Counts is set to 4.9 volts. Changing the MAF_Max_A-D_Counts value to 5.0 volts does nothing to fix the problem and there are no error codes being thrown up.

Anyone have any ideas?

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Post by JuiceSC » Thu Mar 08, 2007 8:01 am

Pegged maf? I wouldn't trust it that close to 5 volts. What kind of pw are you seeing?
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Post by sailorbob » Thu Mar 08, 2007 8:07 am

The MAF's transfer table is untouched. When it goes lean, the injector pulsewidth drops to 8 mSecs. Prior to this the pw is 16 mSecs from about 4k upwards.

EDIT: Added last sentence.
Last edited by sailorbob on Thu Mar 08, 2007 9:30 am, edited 2 times in total.

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Post by JuiceSC » Thu Mar 08, 2007 8:10 am

sailorbob wrote:The MAF's transfer table is untouched. When it goes lean, the injector pulsewidth drops to 8 mSecs.
Ok, thats a problem (the pw). Are you logging maf? If so, what is the maf reading in the logs?

I still feel the maf itself is the problem, you have no room left up on top.
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Post by JuiceSC » Thu Mar 08, 2007 8:13 am

This wouldn't happen to be an SVO by chance? I'm still having a WOT issue on premium setting. (but I haven't really worked on it yet)
91 GT, A9P/A9M, E cam, windsor jr, systemax II, 75mm tb, AFP, 75mm Pro M, 42#, Vortech S trim, GT40 crate 5.0, BBK catted X, flows, Tremec 3550, Pro 5.0, 3.55s, global west 800/160 springs, koni yellows, front swaybar, panhard bar.

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Post by sailorbob » Thu Mar 08, 2007 8:33 am

JuiceSC wrote:Ok, thats a problem (the pw).
Yep, cannot figure out why it's dropping.

The MAF is going up to 4.9 volts and this is where the problem occurs. I'm not even sure it's MAF related but I'm beginning to think something else is the cause.

It's a European ecu BTW, circa 1995.

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Post by cgrey8 » Thu Mar 08, 2007 10:29 am

Does the MAF curve, as it is in the tune now, extend beyond 5v (i.e. to 16v)? Have you tried increasing the value 5v & 16v equal to about twice what it is now and see what this does? If you still drop like a switch, then I'd agree, this probably isn't a MAF issue. But the fact that the MAF is reading 4.9v is still an indication that the MAF is maxing out and should be replaced with something better sized for the air this engine is taking down.

Are you logging the closed loop status? If you can, run it just to make sure you are staying in OL/WOT mode the whole time. I have no clue why, but it would be interesting to know if the EEC is jumping back to CL for some reason. I can't imagine that it is, but being that it is dropping back to 14.9 range seems suspicious. Fortunately for the engine, it's not any leaner than that, but even at 14.9, I'm sure combustion temps are spiking something fierce.
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Post by 86GT » Thu Mar 08, 2007 10:50 am

Chris is right, if the MAF voltage steps over the curve limits then the EEC will go into limp mode and cause the PW to got hell. You have to make sure the MAF curve is not being steped over. Make sure the 16v row is there.

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Post by sailorbob » Thu Mar 08, 2007 10:59 am

The MAF transfer table top row is set to 16.0 volts with the airmass set to the same as the 5.0 volt row below. The transfer hasn't been altered because I'm not convinced it's a MAF pegging issue, there would be a gradual leaning off and not the sudden jump being seen.

We cannot datalog on this ecu but can read 'live data' from the DCL line. I'll see if the eec is dropping out of either WOT or OL mode.

Another thought I've had is whether it’s exceeding 200% load, not come across this before and I have no idea what happens when this occurs.

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Post by cgrey8 » Thu Mar 08, 2007 11:07 am

You can test that pretty easily by putting a larger number into the CID field (say 25-30% larger) and see if this fixes the problem or delays the problem. If it does make a difference, that would indicate you are on the right track that Load has something to do with this.

Of course the rest of the tune's load-dependent settings will be shot to hell once you do that since the load calculation will be too low for any non-WOT running condition. But as a quick test, you can try that just to see what happens.
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Post by EFIpunk » Thu Mar 08, 2007 9:13 pm

Mr. Bob

Can you email me the tune?

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Post by 2Shaker » Thu Mar 08, 2007 9:38 pm

When I pegged the MAF in our car it absolutely was like a switch - nothing gradual about it.

I remember other posts here that said the voltage readings for the MAF beyond the 4.75 value were unreliable. I dunno... :?:

Dare I ask could you be hitting the 1/2 fuel rev limiter?
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Post by stangfreek94 » Fri Mar 09, 2007 5:46 am

Yep, sounds like a pegged maf. I have been over 200% several times in the past, while dialing in other stuff. No effects of that nature. You need a new maf, or a MAFia.
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Post by sailorbob » Fri Mar 09, 2007 5:47 am

I just cannot see it being the MAF that's being pegged; the stock transfer table is scaled to 5.0v and the MAF_Max_A-D_Counts is set to 5.0v too whilst the MAF is only reading 4.9v. I might be wrong but my gut feeling is that something else is affecting this unless the DCL live data readout is delayed enough for it to go over 5.0v.

I don't believe it's a 1/2 fuel limit thing either as half fuel alternates injectors to limit revs and doesn't cut the pw in half.

To add to the the problem the clutch is on it's way out now :roll:

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Post by JuiceSC » Fri Mar 09, 2007 6:41 am

Maybe your reference voltage is 4.9 or a little less? I know, I'm reaching here.
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Post by sailorbob » Fri Mar 09, 2007 6:50 am

Could be, I thought of that too yesterday and I'll look into it. Any and all reaching appreciated :)

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Post by cgrey8 » Fri Mar 09, 2007 7:52 am

After answering a different thread a few seconds ago, I wonder if Clint might be on the right track, that you are entering limp mode when your MAF goes over 4.9v. If you max MAF voltage (VMAMAX or equivalent in your tune) is set to 4.9v, then that would be a trigger to the EEC that you are in an error condition and thus turn the CEL on if that condition sustains for more than so many clock cycles (no clue how many). Once the EEC determines that you are maintaining above 4.9v, the engine may be going "limp." :(

Does the CEL light turn on about the time the engine goes lean? If unsure, try bumping the VMAMAX to 6v and see what happens. Since the MAF physically can't deliver a 6v reading (because it is only given 5v to start with), then you ensure the engine doesn't go limp...at least not because of VMAMAX. :?

...and I deny the insinuation of any innuendo at all. :)

If this does end up fixing the problem, then ultimately it was an undersized MAF that caused all this (i.e a larger MAF wouldn't have allowed this to happen).
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Post by sailorbob » Fri Mar 09, 2007 8:03 am

The MAF_Max_A-D_Counts has been raised to 5.0v (from 4.9v) and no error codes are getting spat out. The MAF_Max_Volts is already set to 5.0v as standard.

I'll try setting both of these to 5.12v, which is the maximum value the parameters can be.

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Post by cgrey8 » Fri Mar 09, 2007 8:19 am

If its already been raised, then that's probably not it. But I wanted to bring it up just incase it hadn't been thought of.
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Post by sailorbob » Fri Mar 09, 2007 8:24 am

You know when you run out of ideas and get to that 'clutching at straws' stage I have a horrible feeling this will end up like this :D

Anyway, just to eliminate the MAF being pegged (and just incase the boost get upped again :twisted: ) does anyone know the part number for the ZA0 Cobra R 5.8l MAF? This MAF is the next logical size step up with about 20% more flow.

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Post by cgrey8 » Fri Mar 09, 2007 8:27 am

I don't know the numbers, but what MAF are you running now?
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Post by sailorbob » Fri Mar 09, 2007 8:42 am

It's the stock MAF (reads up to 935 kg/hr), it's marked with the following part numbers on the electronics housing;

91GB-12B579-BA
AFH55-07A
4H01

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Post by cgrey8 » Fri Mar 09, 2007 8:57 am

I imagine a blue-tube 73mm C&L would do fine. That curve runs up to around 1325kg/hr@5v. That would put you 1000kg/hr@4.68v. 1150kg/hr is 4.85v. Unless you think the engine is pulling down more than this, I imagine this would be sized about right for you.

I'm thinking a used C&L might be cheaper than a Cobra R factory sensor.
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Post by po-po 5.0 » Fri Mar 09, 2007 9:11 am

I think you'd be amazingly lucky to turn up that Cobra R MAF. A better choice might be an LMAF. I know its massive compared to the stocker (reads to 1800) but I can't think of much in the middle?

Maybe an 80mm MAF off a 99-01 cobra?
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Post by sailorbob » Fri Mar 09, 2007 9:20 am

Just been doing some googling and looks like the 4.6l 4v Cobra and the Lincoln Mk VIII use the same MAF as the 5.8l Cobra R so I'll see if I can find their bins to verify this.

Found the MAF Transfer for a Mk VIII and it is virtually identical to the ZA0 bin. The input volts column is the same and the top two output values are too. The remainder of the output values only vary from the ZA0 bin by abround 0.5 to 1.5 kg/hr which is probably because of the different inlet tracts.

EDIT: Added the Mk VIII MAF comparison results.

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Post by 2Shaker » Thu May 01, 2008 2:14 pm

Sailorbob,

What ever became of this? I'm working with stanger007 developing a supercharger template for a blower CBAZA car and see that the template has this value changed to 5.12.
94 GT, CBAZA/J4J1, 347 (on a R302 block), F303 cam, Performer II Intake, 1.7 Crane RR's, 1 5/8 Shorties, 70MM BBK TB, C&L 85mm Tuner MAF, Pro-Charger D1SC, 60#'s, TKO 600. Runs 11:80's

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Post by sailorbob » Thu May 01, 2008 3:23 pm

Not sure what you mean, I do not understand the question :?

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Post by 2Shaker » Thu May 01, 2008 4:15 pm

Ooops, sorry about that, I should have been clearer. :oops: The start of the thread has a lot of discussion about the role of VMAMAX and the value(s) that should be used. I couldn't see in the thread where there was a conclusion about VMAMAX and its relationship to the leaning problem you reported at the outset of the thread. The thread sort of took a few different twists as it went on. I'm trying to nail down a VMAMAX value to put in the template we are creating.
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Post by sailorbob » Thu May 01, 2008 4:39 pm

The guy's head gasket went (110k odd miles of 'spirited' driving probably help this) and so the work on this engine finished before the problem was sorted out. He has been spending his time on uprating the engine and fixing the cars bodywork etc and the last I heard he is nearly done so I may get to revisit this problem in the future.

In GUF*, 'MAF Max Volts' (aka VMAMAX) is the limit indicating short circuit and is checked during normal running and the KOEO test. If the error is reoccurring then the ecu uses one of the MAF failure tables as appropriate.

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Post by cougarnut281 » Thu May 01, 2008 5:16 pm

I have heard of problems on newer vehicles, mostly 99+ having problems if you don't set the air charge wot multiplier and the correction for max aircharge to the max and it would cause similar issues. It's a little late now but is something to look into when the time comes.

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