Here's a brain teaser for you guys

Frogman

Frogman

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This question is more for the guys who have done more than "RimZ" so please bear with me.

We still can't get my Mark to tune for crap. If we change on setting, another setting in a totally unrelated part of the tune gets automatically changed by the computer. Something that should not happen.

Right now, we can get the car to start. It's a rich start though. The injector pulsewith on startup is damned near turned off. The car will idle like junk until the computer sees the O2 sensors warm, and switches to the closed loop tables.

Even then, it likes to hunt quite a bit. The lowest RPM we can get the car to run is at 800RPM. 790RPM, the car does not like. Once the car is in closed loop it drives like a bat out of hell though.

The dashpot seems to work fine. On deceleration, it brings the RPM down to commanded RPM. Most of the time... A few times, it just didn't respond quickly enough, and let the motor die.

There is a tune for just about every state the car can be in. Cold idle, warm idle, cold and warm drive, cold and warm neutral, and we also found out on friday there might be a damned table for Reverse as well.

The main problem we're running into is the computer changing values as it desires. Whether it's supposed to or not.

Any ideas I could pass onto my Dyno guy? Yes, the guy is good. He tuned the fastest... contour? escort? hell, I don't remember no more. So he does know his stuff.

We're going to swap the computers and see if that will change anything. For the guys with the Cobra manifolds, did you use the Lincoln IAC or the Cobra IAC?

My dyno guy just doesn't understand WTF is going on.

75Lb/hr injectors.
SCT maf (the biggest one they sell)
98 Cobra manifold (no holes in it like the 96, and it has the correct plastic with rubber insert gaskets)
No vacuum leaks.

Again, thoughts or ideas would be welcome.

Thanks.
 
The injectors are under control. We thought it was them at first, but no dice.

Why sp big? 800+ motor horses need lots and lots of fuel. And since I don't want to run say, 60# injectors at 100% duty cycle, I got the 75 pounders.
 
I guess we're to assume that it's an 800hp motor. Gotcha.

No idea why the tune keeps changing, obviously it's not from the injectors. Was just curious why the 75 #ers when there was no other mods mentioned.

Do you get any codes? Or can you monitor the IAC and ECT sensors? The car runs off the ECT until it goes closed loop, I believe, so maybe it's sending out wacky signals..?
 
Frogman said:
The car will idle like junk until the computer sees the O2 sensors warm, and switches to the closed loop tables.
Click to expand...
Maybe I'm wrong but I didn't think this had to happen anymore? I thought the newer cars didn't need to warm up the 02's, hence why no one has problems with high flow cats anymore.

Frogman said:
The main problem we're running into is the computer changing values as it desires. Whether it's supposed to or not.
Click to expand...
That's extremely odd. Any way to track what is changing it? I'm thinking there's a sensor(s) that are trying to correct parameters based upon what its reading. The computer is constantly altering things to get the best drivability. I assumed this was turned off when someone added a chip or went it and altered things?

Frogman said:
We're going to swap the computers and see if that will change anything. For the guys with the Cobra manifolds, did you use the Lincoln IAC or the Cobra IAC?
Click to expand...

I would think the Cobra IAC has different parameters but again, nothing you shouldn't be able to fix with tuning.
 
Sounds like you flux capacitor is going out... you might want to get that checked
 
mespock said:
I'd suggest use the @#$%ing Search Function...:D
Click to expand...

Oh yeah, yeah, you're right! I forgot about the search function. I mean, I'm sure this topic has come up a ton of times seeing how all of my fellow Mark VIII owners on here are running stroked, forged and force inducted motors in their cars. I shall try the search funtion. :rolleyes:

mespock said:
Then add a set of 20's on her... That should solve the problem..:cool:
Click to expand...

20's? Screw that. I'm going to 26" RimZ, y0!

mespock said:
Sorry just had to do it....:rolleyes:
Click to expand...

I understand, me being a n00b and all that just signed up a couple of days ago to ask this question.. :rolleyes:

Jibit said:
Well, sometimes a fuel pump always solves the problem :p
Click to expand...

Walbro 255LPH HP with less than 30 hours on it. :D Pump's keeping up with demand... at least according to the fuel pressure gauge mounted on the FPR.
 
Right now, we can get the car to start. It's a rich start though. The injector pulsewith on startup is damned near turned off. The car will idle like junk until the computer sees the O2 sensors warm, and switches to the closed loop tables.
Click to expand...

Hmmm... I wonder if it's related to my issue with the dynotune the other day. My oxygen sensors apparently aren't functioning at idle??? This causes a rich condition. I've been told it can be due to the O2 sensors' position in the headers and can be accounted for in the SCT tune. :confused:

Bear in mind I have no stroked, forged and force inducted motor in my '93. ;)
 
My dyno guy touched on that very same issue last time I saw him. I can't remember if he said he compensated for it or not.

However, that still doesn't explain why the car idles badly once it's warmed up though... :(

We'll see how the spare computer behaves. If the same thing happens with the new computer, then we'll know it's something else.

I really doubt its the injectors. I mean, hell, the High HP 4 cyl crowds are running 100+ lb/hr injectors just fine.
 
Frogman said:
My dyno guy touched on that very same issue last time I saw him. I can't remember if he said he compensated for it or not.

However, that still doesn't explain why the car idles badly once it's warmed up though... :(
Click to expand...

Warm or not - mine was still rich at idle with no O2 feedback.
 
I would suspect the MAF feed back or leak/short from what I am reading. I am running the SCT 2400
 
MAF Feedback? Pardon my ignorance, would you please expound on this?

The MAF graph was fairly smooth. I would think if the MAF was bad, the graph would look like a porcupine. Either way, please enlighten me, RB. Thanks.
 
You are running a return style Walbro pump in a hybrid return/returnless variable voltage fuel system. Even though your fuel pressure seems fine it could be causing problems. You need to get a Lincoln Aviator fuel pump or modify a Ford GT fuel pump to fit. I'm not sure this is what's causing your problems but if it's not the Walbro can cause new problems down the road.
 
No I'm not. I'm running a return style fuel system, just like the OEM setup. The fuel system past the fuel filter is an aeromotive setup. 98 Cobra rails and Aeromotive regulator. Return Style, not 98 1/2+ Cobra returnless.
Note the Fuel return block on the upper right hand corner of the package.

There is nothing hybrid about it. The fuel pump is the same pump most Mark owners use... The upgraded 255LPH HP pump. Well.. to a degree, it's actually a 255LPH HP Walbro designed to fit a cobra canister, but I've already modified the canister. It ran just fine before the motor was pulled.

As I said earlier, the fuel pump is keeping up with the demand just fine, according to the fuel pressure gauge I have on the Regulator.

Aeromotive.jpg
 
I was being sarcastic when I said a fuel pump, didn't think anyone would take me seriously :shifty:
 
As in the reprogrammed computer changes the values all by itself?

For something like that, i dbout it would be mechanical. I'd seriously take a 2nd look at that computer, and maybe even spring for a megasquirt...:D
 
OK well I wasn't aware of what fuel system setup you had going... I would go to a different tuner who deals with lots of 4.6 DOHC setups if possible. Your guy might be good with tuning but a person who has seen lots of modular forced induction applications would be better.
 
I would... But most of the cars in his shop are modular Rustangs. Mostly Cobra Flavors. The guy drives an 06 GT. ;)

And I think you misunderstand. It's not boosted yet. I want to break in the motor a bit before boosting it. A thousand miles or so ought to be good enough.
 
A 255lph Walbro isn't enough pump to keep up with 800hp. That isn't your real problem, but just something you need to know.

Also, with injectors that large you will likely have idle issues. Log the injector stuff at idle and you will see what I mean.

It will be rich.

Just for S&G, swap in a smaller set of injectors for idle only testing. It might surprise you what you find.

Darrin
 
The fuel pump is FINE! As I have mentioned in my previous post, it's NOT YET BOOSTED.

I had thought about swapping the injectors to a smaller set, and see how that works out. But my question still remains. How is it that the 4 cylinder crowd can run 110+ Lb HR injectors just fine then?
 
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