jacob80 Posted April 26, 2009 Share Posted April 26, 2009 Hey guys, we have MS1 V3 board with MSnS. We're trying to tune our L28ET but are having a little issue. Under load, at about ten miles an hour, the RPMs are good but once you trying to start accelerating at all it goes way lean and sound like it cuts the fuel or something, pauses, back fires, then comes back. Could this be caused by our pulse width? We are literally going from ~14 AFR to like 8 within 100 RPM increase. If anyone could suggest anything, it would greatly appreciated. Thank you! Quote Link to comment Share on other sites More sharing options...
essdeezee Posted April 26, 2009 Share Posted April 26, 2009 An AFR of 8 is crazy rich. http://en.wikipedia.org/wiki/Air-fuel_ratio Quote Link to comment Share on other sites More sharing options...
jacob80 Posted April 26, 2009 Author Share Posted April 26, 2009 Uhhhh.....ok? I know that, can you help me resolve this issue? Quote Link to comment Share on other sites More sharing options...
jacob80 Posted April 27, 2009 Author Share Posted April 27, 2009 Ok so our distributor shaft was off, which we fixed, and seemed to help nothing. Here is the issue: The car revs to 6500 rpm easily while not under load. First gear, just engaging the clutch, going about 10 mph and slowly climbing RPMS, 1000, 1500, 2000, 2500, all the sudden, the car seems to have no throttle response and seems to almost die, and a backfire immediately follows if you don't take your foot off the gas. The AFR shoots through the roof for a moment and then comes back down. Now, back down to 1000rpm. What is our issue? Is it something with the injectors? We have 42 lbs.hr Bosch 400s running PWM. Could comething with the PWM be causing something like this? Any help here is greatly appreciated, the car sounds GREAT, but doesn't like to go over 3000rpm. Quote Link to comment Share on other sites More sharing options...
cockerstar Posted April 27, 2009 Share Posted April 27, 2009 What do your fuel tables look like? Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 27, 2009 Share Posted April 27, 2009 You said in the first post that the car goes lean during acceleration, but you said the AFR goes to 8 which is rich. Would you clarify if the car goes rich or lean under acceleration, that will make all the difference on what could possibly be wrong. If the car is going lean it could be a bad fuel pressure regulator. I had a bad one and the car would rev in neutral fine, but at about 3000 rpm when boost would just start to build it would fall flat and run out of fuel. Quote Link to comment Share on other sites More sharing options...
jacob80 Posted April 27, 2009 Author Share Posted April 27, 2009 Ok, hold the phone! I believe it is our fuel pressure regulator. It is a megan racing RRFPR, which I believe is our whole problem. I think that we've been setting our fuel pressure around 40 at idle and when under load, accelerating, it is increasing fuel pressure in excess and dumping in more fuel than needed and creating a rich mixture. Yea, i meant rich, I only said lean because the AFR gauge would go lean AFTER the event, so it wasn't ever lean. We're about to find out if that was our problem. Should we even attach the vacuum line or can we just run the fuel pressure regulator at a set PSI and let the computer adjust the fuel flow through the injectors?? Thanks everyone! Quote Link to comment Share on other sites More sharing options...
jacob80 Posted April 28, 2009 Author Share Posted April 28, 2009 Ok, I take back what I said, sorry. Went for a test run and the FPR seemed to have no effect on our problem. The datalogging is showing when reaching ~2300 RPM from a slow, slow climb in first gear, it completely falls on its face , a slow pause, then followed by a backfire out the downpipe. We are running 440cc injectors with pulse width modulation, could this be a factor at all with the stock turbo? I'm sure the size isn't the issue but maybe the pulse width and/or duty cycle? Here is a pic of the datalogging where the event occurs: Any help would be appreciated, hopefully we can get a response tonight and see what we can do, thanks guys! Quote Link to comment Share on other sites More sharing options...
slown280z Posted April 28, 2009 Share Posted April 28, 2009 What are you using for reading AFRs? Can you post your engine setup and fuel and spark tables? Even an MSQ and datalog would be helpful. Quote Link to comment Share on other sites More sharing options...
joela Posted April 28, 2009 Share Posted April 28, 2009 Attached are the datalog and .msq files Jacob used tonight. The O2 sensor is an Innovate LC-1. Thanks for whatever assistance you can provide him. [EDIT] Ended up with a zero-length .msq in the previous zipfile. It is corrected here. datalog200904272016.zip Quote Link to comment Share on other sites More sharing options...
jacob80 Posted April 28, 2009 Author Share Posted April 28, 2009 Stock rebuilt long block L28ET Stock T3 turbo MSA downpipe Performance products front pulley Fidanza Flywheel Bosch 440cc 42lb/hr injectors (using PWM on megasquirt) Throttle body space with 240sx throttle body Front mount intercooler Megan Racing RRFRP Pallnet fuel rail Walbro 255 lph fuel pump MSnS (v3 board, IGBT triggering enabled) with relay board Upgraded Alternator (280zx turbo alternator) with MSA wiring harness plug Quote Link to comment Share on other sites More sharing options...
slown280z Posted April 28, 2009 Share Posted April 28, 2009 Did you setup the WBO2 right? I don't know if it has changed, but before you had to reprogram an LC-1 (I think 0v=10:1, 5v=20:1 AFR, which is NOT default by Innovate), then setup MegaLogViewer to Innovate 0-5v. This setup does not register anything lower then 10:1 AFR. Quote Link to comment Share on other sites More sharing options...
essdeezee Posted April 28, 2009 Share Posted April 28, 2009 Uhhhh.....ok? I know that, can you help me resolve this issue? I apologize if I sounded like a smart-ass, but I hoped you'd be able to either re-evaluate your situation if you meant what you wrote or notice the typo and correct it so the resident ms experts (aka not me) would be able to help you more effectively. Either way, it was meant to be helpful. Sorry if you don't feel that way. Best wishes in resolving the issue. Quote Link to comment Share on other sites More sharing options...
joela Posted April 28, 2009 Share Posted April 28, 2009 slown280z -- I helped Jacob reprogram his LC-1 prior to this run (and log), which was required as one of the analog inputs (the one feeding megasquirt) had been set as a narrowband output. All is good there now, and it is logging nicely to the file. After the change the cockpit gauge agrees with what the megasquirt is reporting now. Thanks! Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 28, 2009 Share Posted April 28, 2009 Why is the throttle position dropping when this event occurs? Are you just letting of the pedal as soon as it happens? Quote Link to comment Share on other sites More sharing options...
joela Posted April 28, 2009 Share Posted April 28, 2009 Yeah, he's jumping off the throttle as soon as the stumble happens to avoid the big KA-BOOM. Probably wise, as that just can't be good for the turbocharger... Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 28, 2009 Share Posted April 28, 2009 Post the msq file if you get a chance so we can take a look at it. EDIT: nevermind, I see it is coupled with the datalog Quote Link to comment Share on other sites More sharing options...
joela Posted April 28, 2009 Share Posted April 28, 2009 I have attached it with the datalog in a zipfile in post #10 of this thread. I have all of the files from Jacob's config on my laptop, so let me know if there is anything else that might be of use. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 28, 2009 Share Posted April 28, 2009 I looked over the msq file and I only see a couple general things. One I am not sure if it is real or just didn't load correctly when I opened you msq, but the setting for overboost rev limit was 0 kpa which is not valid, it should be something like 200kpa or were you want spark cut on too high of boost. These probably don't have any impact but just observations: the spark angle is low for idle for an L28ET, you have 15 it is more like 23 on the stock setup. The fuel table only has a couple bins beow 100kpa. You will probably want something like 20,40,60,80,100 etc or you will have a lot of trouble trying to tune for cruising which is were you spend most of the time driving on the street. Maybe this is causing too big of a jump and causing some of the problems with it going rich, I am not sure. Quote Link to comment Share on other sites More sharing options...
joela Posted April 28, 2009 Share Posted April 28, 2009 I don't think that we set up the overboost limit, so I assumed that 0 disabled that function as in many other places in megatune. Do you think that this might be the root cause -- spark being cut right out of the gate and fuel being dumped into the exhaust, then ignited once the spark resumes? Quote Link to comment Share on other sites More sharing options...
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