2eighTZ4me Posted March 24, 2011 Share Posted March 24, 2011 After 4 laps at Road Atl, the car started missing. Water temp never went above 185, oil temp never exceeded 210. At lap 4, the car would start to miss under accel at about 7psi. Next lap, about 5psi, and for the rest of the session, it would miss at 3psi (and above) and would not accel any faster until I let off the throttle (at which time, all cylinders would fire properly). Car has just been professionally tuned by DIY AutoTune, and it runs flawlessly on the street. It wasn't until I got it on the track where I was hammering it constantly that the problem showed itself. Thinking the spark was getting blown out, I dropped plug gap from .030" down to .025". It ran great for the first 4 laps again in my second session, and started the missing thing all over again. I'm running NGK BPR7ES plugs. I can not for the life of me get it to reproduce on the street (without spending a potential night in the pokey), and I've beat the hell out of it on the street to no avail. DIY wants me to pull logs when it does it, but I can't get it to reproduce anywhere (it seems) but on the track. SCCA tends to frown upon laptop passengers on the track. I'm in a bit of a pickle here.... Looking for any possible things to try or look at to mitigate this for the next track day. Suggestions??? Quote Link to comment Share on other sites More sharing options...
Cannonball89 Posted March 25, 2011 Share Posted March 25, 2011 Strap the laptop securely under your seat and don't tell the SCCA its there? Its kinda hard to say where the problem is coming from without data. Could be ur boost control solenoid creating interference at high duty cycles not seen on the street or something like that. Or it could be that MS reset on track under boost. I've heard that when MS resets the MAP sensor reads whatever pressure it is seeing as atmospheric, meaning that if you reset at full boost it would see 3 PSI as vacuum. Quote Link to comment Share on other sites More sharing options...
stagefumer11 Posted April 12, 2011 Share Posted April 12, 2011 check your alternator. Could be heating up under the loads and dropping voltage, This with a worn/tired battery could be causing weak spark.. Another one is a bad ground, Over time with the larger that normal loads in track work the battery to chassis, or to block ground is failing, Causing resistance though the heat build-up. I know it sounds weird, But ive had similar things happen.. Current makes heat, Heat can cause resistance. = low voltage Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 12, 2011 Author Share Posted April 12, 2011 Alternator is good. It's a GM conversion - I think the 90A model. Battery is a less than a year old DuraLast that tests out fine. Also have a voltmeter in the car that's showing +/- 14.5 volts at just over 1000rpm. Plenty of juice. There's also more grounds on the car than I can even count. At least 6 to the chassis and cage at different points, as well as a big junction at the front AC compressor mount bolt. I do see your point though, although I'm inclined to believe the spark is getting blown out. Only happens at a certain MAP point (which varies according to # of laps run). I have a test I'm going to try out. Since I can't get it to fail on the street, I'm going to gap the plugs at .040" and see if I can replicate it on the street. Barring results there, I'm going BACK to the track on May 22nd and hiding my laptop under the seat!! Quote Link to comment Share on other sites More sharing options...
tvgz28 Posted April 21, 2011 Share Posted April 21, 2011 What kind of coil are you running and what are your dwell settings? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 21, 2011 Author Share Posted April 21, 2011 TEC3 DFU coil packs - I'd have to check to see what the dwell is set at. I just got a new laptop and it doesn't have a serial interface, so I need to run by MicroCenter and pick up a USB to serial adapter. That's on tap for the weekend... Quote Link to comment Share on other sites More sharing options...
roger280zx Posted April 27, 2011 Share Posted April 27, 2011 Did you get to the bottom of this? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted April 27, 2011 Author Share Posted April 27, 2011 Nope - not yet. Can't replicate on the street. Will be at the Mitty this weekend and in the studio Sunday, so won't have time. Have another PDX event on 5/22 that I intend to find a way to secure my laptop and pull data logs. Always somethin' eh? Quote Link to comment Share on other sites More sharing options...
skirkland1980 Posted July 7, 2011 Share Posted July 7, 2011 This thread is kinda old but here is some experiences I've had. I had a similar problem which was fixed by increasing the injector currents. Also don't overlook cracked coils or wires. I don't know what type of trigger your using for MS but make sure the sensor is positioned properly and not loose. Also make sure the CAS wires are shielded/twisted and away from the ignition system. good luck! Quote Link to comment Share on other sites More sharing options...
Zmanco Posted July 7, 2011 Share Posted July 7, 2011 Just saw this thread and I had the exact same issue running MS2/Extra and a Blaster II coil on the track. I could not replicate it on the street. I dataloged and found it was going completely lean when the power fell off - which can mean there is no spark. I narrowed it down to either the transistor/driver in MS or the coil overheating. I figured I was eventually going to go EDIS anyway so used this as the reason do it. I haven't had an issue since. Quote Link to comment Share on other sites More sharing options...
Tony D Posted July 7, 2011 Share Posted July 7, 2011 "Thinking the spark was getting blown out, I dropped plug gap from .030" down to .025". It ran great for the first 4 laps again in my second session, and started the missing thing all over again." That would indicate to me something heating up and dropping efficiency. I can't believe Coil-Packs would be overheating in those circumstances, and the dropping of the gap didn't change the onset of the phenomenon so it doesn't look coil-voltage related. As for laptop passengers, there are some Dell, and other NETBOOKS that are cheap with a gob of memory that are small enough to literally screw to the side of the transmission tunnel under some cushioned straps. The all solid-state units could write directly to drive as well for the datalog and not have the possibility of write-errors. You can strap an ECU in, make a computer platform and screw it down the the floor and there shouldn't be an issue. I would look internal to the box, I would think the coil driver is heating up under the extended higher RPM loads you're experiencing, or some other nebulosity. This may sound completely bizarre, but have you got a fitting in your inlet between the inlet filter and the turbo? Ventilate the MS Box and run a tube to continually suck air through the box (or maybe operate it with the cover off, or will a small computer fan blowing on the internals with the cover off.) If this improves it, then you know the heat related problem is inside the box. When JeffP was having issues with the Nissan Box just for S&G we shot a thermal scan of the kickpanel inside his ZXT...damned if it wasn't 150+ behind that plastic! We left the cover off and drove around then tried again and the problem went away. Ventilating solid state components is a good idea, regardless of their 'service rating'---a box at 70 degrees works more reliably, long term than one at 140! If you can find them 'temp-a-cals' (don't know if that is the right term) are a great way of determining maximum temperatures of hard-to-get-to components. They are temperature-indicating decals that turn 'red' to indicate the maximum temperature encountered. We stick them on some starter cubicles in a concealed spot to verify ambient rise in case of warranty. "Silent Sentinel" kind of theory. You may be surprised to see how hot some items are getting when at the track compared to leisurely driving on the street! Quote Link to comment Share on other sites More sharing options...
Pyro Posted July 26, 2011 Share Posted July 26, 2011 In racing conditions, could be the gas is leaving the tank too fast. So a vacuum in the tank is created which makes it hard for the fuel pump to pull fuel out of the tank. Quote Link to comment Share on other sites More sharing options...
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