Studdering with FMU.....?

[SnakeIs]

I just finally got my 42# lightning injectors and matching Pro M in my car and untill I can get my wideband on and tune it, I am using my ATI FMU (adjustable bleed type) My car seems to have a really bad studder between 3500-4400rpm (just building decent boost) and then it seems to clear up and pull to redline. I have been told that it is the FMU causing this I have adjusted it both ways and the problem still exists, any of you guys have this problem? Any idea what else it could be? It will even hiccup through the intake every now and then...

[paluka21]

Originally posted by SnakeIs
I just finally got my 42# lightning injectors and matching Pro M in my car and untill I can get my wideband on and tune it, I am using my ATI FMU (adjustable bleed type) My car seems to have a really bad studder between 3500-4400rpm (just building decent boost) and then it seems to clear up and pull to redline. I have been told that it is the FMU causing this I have adjusted it both ways and the problem still exists, any of you guys have this problem? Any idea what else it could be? It will even hiccup through the intake every now and then...

What kind of fuel pressure are you seeing under WOT, and at idle? Obviously your gonna need less fp w/ the 42's than w/ your previous injectors.
Whats your plugs gapped at? The added fuel might be drowning out your spark.

just a few things to look at
DAN

[SnakeIs]

Dan, I have dropped the FP to around 38 at idle and I have turned out the adjustment on the FMU to where it only sees about 50-55psi under boost, I didn't think that seemed like too much. I have the plugs gapped at .035 and just put the full MSD 6AL on.

[paluka21]

Originally posted by SnakeIs
Dan, I have dropped the FP to around 38 at idle and I have turned out the adjustment on the FMU to where it only sees about 50-55psi under boost, I didn't think that seemed like too much. I have the plugs gapped at .035 and just put the full MSD 6AL on.

Try removing the FMU to see what happens. I had an FMU on my car w/ 50's via Laroccas suggestion. If I were you I would remove the FMU, run the base fp at 42-44 and see if that helps.

DAN

[SnakeIs]

I'm just scared of going lean without it, I do have the eec tuner but since the injector install I have went back to all stock fuel tables. You don't think I'll be lean without it? Are the 42's enough to feed it?

[paluka21]

Originally posted by SnakeIs
I'm just scared of going lean without it, I do have the eec tuner but since the injector install I have went back to all stock fuel tables. You don't think I'll be lean without it? Are the 42's enough to feed it?

Pull out some timing near peak torque as I am sure you are. Friend of mine is running 42's w/o fmu making 485rwhp and 450ft/lbs. Car seemed to have plenty of fuel, and he was only running a 190 intank and T-rex external.
He was tuned by jimmy c at laroccas
DAN

[WA2FAST]

I would suggest pulling your FMU out... with #42 injectors, you more than likely don't need it. I would set your base FP (at idle with vac. line off) at 42-44 (just as Dan said), drop your timing to 10 degrees base, and re-gap your plugs to .030... .035 is probibly a bit much even with a MSD ignition... there are people on here that will tell you .025 and the car has never run better since they re-gapped it there. You really shouldn't need a FMU with those injectors unless you are running a rather radical intake, cam, and head (especially) combo. Also, pull some timing out up top as Dan suggested as well. (is there an echo in this room? :p )

What exactly is your setup, what blower are you running, how much boost, do you have any dyno figures at all... N/A or boosted? This will help.

[SnakeIs]

Well, I was going to post this in a seperate thread altogether, but I'll go ahead and get it out here. I put it on the dyno (brand new 248C at a friends shop) for the first time this Saturday, he was doing a free dyno day to promote the shop and we got just 3 power pulls and no tuning. I was VERY depressed! But I am hoping its all in the tune! The best I could do was 255rwhp with a 10.0 AFR and only 20 degrees timing up top. This was with 9-10psi of boost.... Please tell me that I can tune this thing to my goal of 425-450!! I had the FMU on with the 42's but backed the bleeder screw all the way off and it still showed a 10.2afr at WOT. It was so rich that it began breaking up on the dyno and we only pulled it to 5800-6000rpm. I am ripping the FMU off this week and putting the wideband in and hope to get it sorted out. I am going to shoot for a 11.5 at WOT and maybe raise the timing up since the poor little P600 will only make 10psi on my motor. I was really trying to make this thing safe since I blew my motor last year, but I guess I got it wayyyyy to safe!

WA2FAST- I have a DSS 306 (less than 5000miles) out of the box GT40X heads, F303 cam, 1.6RR's, Upper and lower GT40 tubular, 42# injectors and matching ProM 75mm MAF, 70mm TB, 255lph intank and ATI inline, Full MSD, MAC shorties, X pipe, etc. P600 with 2 core and 14psi pulley seeing 10psi max. and probably a few other things that I missed.

[paluka21]

Originally posted by SnakeIs
Well, I was going to post this in a seperate thread altogether, but I'll go ahead and get it out here. I put it on the dyno (brand new 248C at a friends shop) for the first time this Saturday, he was doing a free dyno day to promote the shop and we got just 3 power pulls and no tuning. I was VERY depressed! But I am hoping its all in the tune! The best I could do was 255rwhp with a 10.0 AFR and only 20 degrees timing up top. This was with 9-10psi of boost.... Please tell me that I can tune this thing to my goal of 425-450!! I had the FMU on with the 42's but backed the bleeder screw all the way off and it still showed a 10.2afr at WOT. It was so rich that it began breaking up on the dyno and we only pulled it to 5800-6000rpm. I am ripping the FMU off this week and putting the wideband in and hope to get it sorted out. I am going to shoot for a 11.5 at WOT and maybe raise the timing up since the poor little P600 will only make 10psi on my motor. I was really trying to make this thing safe since I blew my motor last year, but I guess I got it wayyyyy to safe!

WA2FAST- I have a DSS 306 (less than 5000miles) out of the box GT40X heads, F303 cam, 1.6RR's, Upper and lower GT40 tubular, 42# injectors and matching ProM 75mm MAF, 70mm TB, 255lph intank and ATI inline, Full MSD, MAC shorties, X pipe, etc. P600 with 2 core and 14psi pulley seeing 10psi max. and probably a few other things that I missed.

255rwhp? Are you sure you dont mean 355? Even w/ the car that fat you should be making some decent power w/ 9-10#'s of boost showing. How does the car feel at WOT? does it feel as strong as it did prior to the injector change? Didn't you say the car went 117mph in the 1/4 a while ago?
Something definetly isn't right and to be honest I would not think that just tuning is going to give you 200rwhp, again are you positive that you are running on all cylinders? I am not being sarcastic, just looking at obvious things first. Please post more in regards to what is going on. I honestly think that the 42s are fine for your setup.
I had a very similar setup w/ the same amount of boost that you are making and made 464 to the wheels w/ an 11:1 a/f and 23 degrees of timing.

good luck and keep posted.

[WA2FAST]

I agree with Dan... entirely... doesn't sound right at all. I was at 255rwhp with a mild N/A setup a while back... I was actually over that power.

[SnakeIs]

Well, its a brand new DynoJet 248C and that was the biggest numbers it gave me. I'm thinking it was actually way richer then 10.0 though because the wideband only registers to a minimum of 10.0:1 afr and we think it may have been off scale becuase it actually spit black crap on the wall behind the tails when we pulled it and, it was breaking up rather badly at about 3800 and up.

It didn't just start this with the new injectors, it began this as soon as I did the A9L EEC swap....and I can't seem to tune it out. It actually ran good with the old injectors and the stock 95GT EEC.... I'm thinking something could be wrong with the eec swap but I have checked and double checked for any codes and get nothing at all and the car runs smooth and cruises very well. I am going to try and do a compression test soon just to make sure everything is kosher. But now that you guys have mentioned it, this all started with the new EEC. Any ideas what I could look for here guys? This is driving me nuts!

Dan-you heard the car just a few weeks ago at MD, did it sound fine to you?

[WA2FAST]

If it was that off and missing... why did you continue the pull? Especially if your numbers were that low for what you have... you should be making more than that N/A! Are you sure that the pin's are all moved over correctly for the A9L? I have done that conversion before... if you don't get it exactly right, then you are in trouble... the car is going to run like crap. Go to Pro-M's website... I'm not sure if they still have the conversion instructions there (you only have to move a few pins in the harness if I remember correctly) but those are the directions that I followed and it worked just fine. Make sure that the pins you moved over are not just floating around in the harness and actually locked into place... the red-plastic insert HAS to go back in as well otherwise you run into pins pushing out and not making good contact... sometimes depending on which pin is not right or making good contact, you won't get a code... so I would double check the installation. If your problems started then, I am willing to lay money down that your problem lies there somewhere.

[paluka21]

Originally posted by SnakeIs
Well, its a brand new DynoJet 248C and that was the biggest numbers it gave me. I'm thinking it was actually way richer then 10.0 though because the wideband only registers to a minimum of 10.0:1 afr and we think it may have been off scale becuase it actually spit black crap on the wall behind the tails when we pulled it and, it was breaking up rather badly at about 3800 and up.

It didn't just start this with the new injectors, it began this as soon as I did the A9L EEC swap....and I can't seem to tune it out. It actually ran good with the old injectors and the stock 95GT EEC.... I'm thinking something could be wrong with the eec swap but I have checked and double checked for any codes and get nothing at all and the car runs smooth and cruises very well. I am going to try and do a compression test soon just to make sure everything is kosher. But now that you guys have mentioned it, this all started with the new EEC. Any ideas what I could look for here guys? This is driving me nuts!

Dan-you heard the car just a few weeks ago at MD, did it sound fine to you?

Your car sounded/seemed fine to me a few weeks ago, however something obviously isn't right. Its possible what WA2FAST is saying about the A9L could be an underlying issue.
I am not sure when I will get the chance to get the car retuned, however I would like to say "mid summer." You are welcome to come to Laroccas with me to have him look over your tune, and throw it back on the dyno. I am sure he could pull quite a bit from your car.
Where did you made the 255rwhp? Was it around 3800rpm?

Dan

[SnakeIs]

WA2FAST- that is what scares me, I thought if something was wrong though, that I would get driveability problems or the CE light would have to come on. I had a hell of a time doing that conversion and couldn't for the life of me get that damn red plastic thing back on the harness. But the car fired right up and settled to a nice idle so I figured all was well. I still have the instructions from ProM and there is about 13 pins that you have to change and few wires to add (BAP, Fan control) The car drives great and seems to run smooth so I can't imagine somethings wrong with the conversion.

Dan- I'd love to ride to LaRoccas sometime. It just scares me to drive my car all the way up there and have something go wrong. isn't it like 4-5 hours from here (Winchester, Hagerstown)

I didn't even keep the graph so I'm not sure where it made the power really, I didn't want anyone seeing that graph! I have a few guys on one of my tuning boards telling me that the car may have been so rich that the WB wasn't reading it accurately(most only read down to a 10.0:1) and that all the fuel was blowing the spark out causing the misfire, hence the really low numbers. I am going to lean it out and start adding timing and get back on that dyno as soon as time permits. I can tell you that I took the FMU off and added about 3 degrees of timing from 3k-up and it really made the car feel better on the street, so maybe I was just killing it with my *safe* tune....

[paluka21]

Originally posted by SnakeIs
WA2FAST- that is what scares me, I thought if something was wrong though, that I would get driveability problems or the CE light would have to come on. I had a hell of a time doing that conversion and couldn't for the life of me get that damn red plastic thing back on the harness. But the car fired right up and settled to a nice idle so I figured all was well. I still have the instructions from ProM and there is about 13 pins that you have to change and few wires to add (BAP, Fan control) The car drives great and seems to run smooth so I can't imagine somethings wrong with the conversion.

Dan- I'd love to ride to LaRoccas sometime. It just scares me to drive my car all the way up there and have something go wrong. isn't it like 4-5 hours from here (Winchester, Hagerstown)

I didn't even keep the graph so I'm not sure where it made the power really, I didn't want anyone seeing that graph! I have a few guys on one of my tuning boards telling me that the car may have been so rich that the WB wasn't reading it accurately(most only read down to a 10.0:1) and that all the fuel was blowing the spark out causing the misfire, hence the really low numbers. I am going to lean it out and start adding timing and get back on that dyno as soon as time permits. I can tell you that I took the FMU off and added about 3 degrees of timing from 3k-up and it really made the car feel better on the street, so maybe I was just killing it with my *safe* tune....

Last time it took me about 4 hours to get there through p.a. I honestly didnt mind the drive, and actually drove the mutang up there.
I will probably do the same thing again, drive it up and drive it back. If you do a thorough inspection of the car and make sure there there is nothing wrong w/ the head gaskets, etc then you shouldn't have a problem on the dyno.
Its hard to say what went on w/ your a/f ratios and your power output. Since you said your car went 117mph in the 1/4, then you are definetly making more than 255rwhp.

Dan