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Fitech tuning... acceleration issue

before I do too much further on adjustments, I need to check for/eliminate other issues Fitech told me to look for:

air leak... my header bolts need tightened up, got some of them but gonna have to figure something out for the remaining ones as nearly impossible to get to. gonna buy a cheap wrench and grind it to see if I can make something work. lesson: next time I install headers, gonna use Stage 8 locking fasteners

fuel pressure... guess I need to put a gauge on my fuel line somewhere to confirm the Aeromotive fuel pump is delivering what the fitech needs.
 
Stage 8 are great (I used 'em). I have yet to go back and install the locks because, in my case, they never loosened. I used Percy's aluminum header gaskets, which are simply awesome. Super thick and fix even the worst of flawed surfaces. Back to the Stage 8 bolts though. What is best about them is they feature a small 3/8" head combined with a 3/16" Allen head feature. Between the two its pretty easy to get bolts cranked down and torqued.

Why not swap out to them now?
 
Horseplay said:
I also noticed that depending on my driving habits I could develop a gas smell too. After logging quite a few trips of various driving styles I was able to go back and make some changes to my AFR settings and a few other things that resulted in slightly better "seat of the pants" feel while also leaning things out a bit and eliminating the gas odor.
Amazing what can be accomplished when I finally decide to actual do something! After all of this I am keeping things as they are. The unit I have gets the job done to my satisfaction. I will still get the car up on a dyno and let an expert play around a bit more at some point likely but its no where near the top of a to do list anymore.
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great you got it sorted out ! that has to be a great feeling.

Turns out that I DO have the PWM setting. I guess my unit is newer than I thought. I finally installed a fuel pressure gauge today and now I know my fuel pressure is dropping when I work the throttle... so I went back and adjusted my PWM setting from 2500 to 1500 per your suggestion. Too late tonight, hopefully get time to give it a drive tomorrow and see if it made any difference.

While poking around, I also noticed a fuel pump voltage setting. Currently set to 9 IIRC. With the Aeromotive pump, I wonder if that voltage needs to be adjusted at all? Don't want to burn up my pump, but don't understand why it would not be set to 12. I need to go double check that to see if I was reading it right..
 
I haven't read anywhere where that has been adjusted. I'd ask FiTech about that move before making an adjustment to it. My guess would be it's a baseline and the system adjusts it as required but that's just a guess.
 
thanks, yeah i need to cool my jets and work with one chnge at a time. hopefully have time to drive it today and see if there is any change.
 
You also need to just drive it and let it learn. It takes a while. I drove my car much of last summer and all this year quite successfully before finally chasing a few issues, mainly in the area of aggressive acceleration. Other than that, the system worked itself out quite well.
 
yeah I understand, and will let it do it's thing. but my issue was both hard and soft acceleration... it is/was the soft acceleration that has me concerned, going so lean on the afr, I am trying to debug that. even accelerating away from a stop light or lightly passing someone on the interstate was producing some bucking and drivability issues I did not have before.
 
Have you gone back and re-torqued your intake manifold? Made sure the FiTech is bolted down tight? In other words made sure you don't have a vacuum leak. Also, verified your timing? I know you already are looking at exhaust leaks but honestly that won't cause too much of an issue. Not like a vac leak. I suggest do all these basic things and then let the unit learn. It will stumble and such now and again as it learns and adjusts. Make sure you are varying your driving style a bit and also the conditions it sees. Find some hills and go up and down under different throttle actions. Ease the pedal out of corners (on and off the gas situations) and other times get a bit more aggressive, etc. You do all this and after a few hundred miles it should be good to go.
 
ISSUE RESOLVED.

it was my PWM setting. set at 70-something for frame mounted fuel pump. I had swapped out to in-tank pump. Found a forum talking about PWM and what it did... said to set to 40 for in tank pump. Set to 40, went for a drive... much better but still slight hesitation... dropped to 35... better... dropped to 30... PERFECT. runs like a raped ape. I backed down the accelerator pump adders I had put in trying to resolve it... knock on wood, it is running great now.

Thanks for all the ideas and suggestions which put me on the right path to fixing this !
 
Hold up a minute. I was suggesting you adjust the PWM RPM setting down to 1500. This is the point at engine RPM when the fuel pump gets full power. What you adjusted is the actual pulse width modulation of the pump electrical power. Lowering the value is slowing down the pump operation (reducing flow and possibly pressure). I did a quick Google search and think I found the page you were reading and it directed to drop that value from 70 (stand alone electric pump) down to 40 WHEN USING THE FITECH COMMAND CENTER. The command center is an intermediary fuel feed reservoir/pump so it makes sense you wouldn't need such a high constant flow volume.


No idea how this adjustment fixed your issue unless you were having a very serious over fueling condition which just doesn't seem right. Did you also adjust the PWM RPM as I suggested? Thinking you are making too many adjustments at once and are not able to know what is actually working for you.
 
I lowered the PWM RPM as you suggested, and ran it for a week. May have been slightly better, hard to tell, but stiill had the issue. I installed fuel pressure gauge and observed my fuel pressure dropping when I revved the motor. Replaced the header bolts with Stage 8 and retorqued the intake (2 bolts loose but that was all). No change. I figured would try lowering to 40 and see what happened. if better, good, if not, put it back to 74. Lowering to 40 it ran a lot better, not perfect, but way better. Lowered to 35 made a run... better... lowered it to 30 and seemed to pull like a freight train no hesitation or bucking. Whether that is right or not I dunno. I DO know it fixed my problem. I backed out the accelerator pump increases I put in there a couple weeks ago, and right now everything is running great. I'll put some more miles on it this weekend to confirm.

I did email fitech tech dept to ask them if setting to 30 will hurt anything since they recommended 40. My problem was maybe 80% better at 40, but it's running 100% better at 30. Fitcech confirmed what you said, 30 is lowering voltage to the fuel pump, but also said 30 would not hurt anything. I ran out of time to check fuel pressure while revving the motor or to monitor AFR when making aggressive runs but will do all that between now and the weekend.


Edit: Reading your doc above makes more sense than the one I attached below. I am going to try changing from 30 to 100 and see what it does. I do know that in my limited road test yesterday it ran good at 30, which after reading your doc I agree with you it does not make sense.

I am only changing one parm at a time and monitoring results... (except for retightening everything, which had no affect and needed to be done anyway)
 

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The FCC is basically a forward mounted fuel tank and electric pump. When using it you back off the normal, rear mounted (either frame or tank) pump so as not to push too much fuel forward. All it does in this case is fill the FCC. The FCC controls volume and pressure to the FiTech. Dropping the PWM value as you did when not using the FCC would even further starve the system for fuel. You wrote earlier you noted pressure loss when reving the engine even before making the PWM value change. Things would only be worse now if you slowed down the pump.

So that tells me a few things. One, you might be fighting a bog due to too much fuel in the first place rather than lean. Two, you have got some fuel control values set too high, such as the accel pump and fast accel pump, to start. Lastly, RUN A DATA LOG under all conditions so you can see what is really happening. A lean hesitation vs a fuel rich bog cannot always be deduced by the seat of your pants. Record some data runs and import them to a computer. The software does it all even putting the data in simple Excel spreadsheets. Then you can see EXACTLY what happens a full throttle hits, etc.
 
today I did data logging of a couple different pulls. Hopefully the links below work, this cloud sharing stuff is new to me.

file 1: PWM set to 100 https://drive.google.com/file/d/1zAHXc_RoAYNnhVatsw2r7p9mVKpAYg-7/view?usp=sharing

file 2: PWM set to 30 https://drive.google.com/file/d/1dDldOOAa6dGRHbDnV8an8M-to1Z0fnmr/view?usp=sharing

definitely a difference, runs better with PWM at 30, although I felt some slight hesitation today that I did not feel yesterday.

I am too dumb to understand what I am looking at. In both files, seems to go really lean at 2600 rpm, but more lean when pwm is 100. it doesn't make sense to me, if lowering PWM lowers fuel pressure.

if anything jumps out to anyone or anyone has any ideas, I welcome the input. Also going to see about fitech tuning forum where I might get some help.
 

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Ok, to start with perfect AFR would be 14.7 or so. To be safe you should be wanting to see your AFR values in the upper 13 range maybe even into low 14s in normal driving. When you hit it hard, full throttle fun romps you should be setting it to be in upper 12s and maybe into very low 13s. I am see all kinds of lean to serious lean in both those logs. Anytime you getting much above idle speed things go from normal into lean and quickly dangerously lean.

Adjusting the PWM doesn't lower pressure it lowers volume which can also result in low pressure if your system runs out of volume. It is slowing the speed at which the pump is running.

Also, you don't need to be adjusting the Accel Pump values those should be fine in the base program. What likely needs adjusting is the Fast Accel values (at least at 170 degrees) which is the pump shot when you stab the go pedal.

What you are judging by your seat of the pants is misleading you. You've got the engine running so lean by default you have eliminated a rich bog you had prior but at the risk of detonating your engine to oblivion. My suggestion is to set it to go back to the default settings and see how it does and then start to make adjustments slowly from there. Going back to the original settings, re-entering the engine basic info like you did at first, will not impact what the system has already learned but it will get you back to a safe starting point. Driving around with an engine routinely in the 16-20 AFR range will not end well.
 
Share those logs with FiTech and also any online communities specific to FiTech. I know there is a big one on Facebook but I'm not a FB kind of guy so never went there. There are plenty of people out there WAY SMARTER than I on tuning these things that can help. Don't get discouraged but absolutely get it running richer before you hurt it. You could also seek out a tuner in your area who could sort it all out.
 
I just wanna be clear... I was not mucking around with any of the settings. prior to this issue all I had changed was the DFCO setting per Fitech instructions for manual vs automatic trans to keep it from stalling when pushing in the clutch at a stop. The issue may be because of me switching from frame mounted pump to the in tank pump, I dunno. The issue showed up sometime after that but not exactly sure when. The accelerator pump settings I changed to try to resolve it have been changed back. I have messed with the PWM setting per the article (40/30 and 100) and dropped the rpm for pump on to 1500, but that was all.

my regular mechanic is good and he has installed several of these systems, will review the logs with him to see if he has any ideas and also send to Fitech. cause I am out of ideas. I do appreciate all the suggestions and help.
 
Horseplay said:
Share those logs with FiTech and also any online communities specific to FiTech. I know there is a big one on Facebook but I'm not a FB kind of guy so never went there. There are plenty of people out there WAY SMARTER than I on tuning these things that can help. Don't get discouraged but absolutely get it running richer before you hurt it. You could also seek out a tuner in your area who could sort it all out.
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,
Terry - just to let you know, I am officially AN IDIOT and my problem is SOLVED.

It was hardware not software. the bronze filter on the inlet side of the throttle body was nearly completely clogged with some kind of fine black crap. cleaned that out, and the car has never run better.

I did not figure it out... I called my mechanic late this afternoon and he said bring it over. in 10 mins he knew what the issue was, and another 5mins he had it fixed. of course, he just went thru the same exact issue on an el camino he put a 383 and fitech in, so he had a clue. I never thought to check those cause I don't have but maybe 1000 miles on my car, my bad. I think it has been partially clogged from day 1... it has always had a very slight stumble when working the throttle under the hood... now even that is gone. the car is running better than it EVER has.

THANK YOU for all your suggestions and ideas. Sorry to be a PITA, I kept thinking it was more complicated issue than it was. Hence I AM AN IDIOT. I'll get there eventually. I hope others can learn from my stupidity.

to anyone else reading, check the simple things first.
 
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That's awesome, Steve. And for the record I never thought you an idiot. I save that title for our friend {.}.

I have to ask though, being a brand new build where did the "black stuff" come from that caused the filter clog? You used a new tank and lines, right? Did you run SS lines or steel? Or hose? Has me wondering if even after blowing out the line stock I used if I shouldn't pull mine apart and see if I find some of the same. I used some sections of Russell hose near the engine for routing ease. Seems to me hose makes the most sense especially since it's black.

Looks like I have a weekend task to get after.
 
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