X64v Posted January 3, 2008 Share Posted January 3, 2008 Can I get someone to post a datalog up here that goes up to 6k or 7k rpm? I've been chasing down a slight high rpm miss for quite some time now, and I think it might be due to an inaccurate rpm signal above ~5k rpm, but I haven't been able to find any datalogs to compare my signal to. Thanks. Quote Link to comment Share on other sites More sharing options...
z-ya Posted January 3, 2008 Share Posted January 3, 2008 Have you data logged you car when the miss happens? Is the tach signal stable when the miss happens? Are you triggering off the coil directly? Quote Link to comment Share on other sites More sharing options...
Zmanco Posted January 3, 2008 Share Posted January 3, 2008 By "miss", do you mean loss of power? What does the injector pulse width look like when it occurs? If the PW from the log is reasonable, then it might be a fuel delivery or ignition issue. Quote Link to comment Share on other sites More sharing options...
X64v Posted January 3, 2008 Author Share Posted January 3, 2008 The miss 'feels' like just a single spark event being dropped, perhaps once or twice per second. For a little more info, I'm running spark control as well, firing the coil via the vb921, and triggering via an '82zx VR dizzy (from a N/A zx, not a turbo). It doesn't always miss at high rpm's, only on the freeway after perhaps an hour or two of driving. Attached is a datalog of a second gear pull. After 5k, is that rpm graph normal, or too rough? tune 4-c.zip Quote Link to comment Share on other sites More sharing options...
Zmanco Posted January 3, 2008 Share Posted January 3, 2008 I took your file and converted it to excel and then hid some unused columns to make it easier to read. I also highlighted in yellow the PW and RPM columns. On this pull, I don't see any significant drops in PW that would cause you to feel a miss. I did notice one event where your Batt voltage dropped to 9V (highlighted in red). Did you have a reset there? That would feel like a miss alright! FWIW, above 5k your rpm doesn't look any rougher (noisier) than my NA. Above 4k rpm the MAP reading seems to jump around a lot, but perhaps that's normal for a turbo? A suggestion: run a datalog with megatune. As soon as you feel a miss, hit the space bar on your laptop. That will mark the spot in the datalog where it occurred - offset by the time it took you hit the space bar of course. Then use megalogviewer to go back and find the marked event. Look for a reset, or anything out of the ordinary with PW, O2, and Battery readings. That might give you a clue. If everything looks good, you might need to look elsewhere. I'd check ALL my wiring for anything that could be intermittent. With the engine idling wiggle all your connections listening for anything that affects the idle speed, even momentarily. If none of this helps, I'll suggest something else: consider changing plug wires. I had my MS working pretty well with the exception of occasional resets when running at WOT for extended periods. I decided to stop using the MS PWM and instead added resistors to the injector circuits. I found I didn't get resets at WOT throttle anymore, but instead began to get them more often all over the rev range, even at idle. After a lot of research on the MS site, I decided to change to Magnecore wires since they seem to have the best suppression of RF energy. Since I installed them ~500 miles ago, I haven't had one reset. I'm not saying this is what's happening in your situation, but if you find the "miss" is really a "reset", then this is something to consider. 2nd gear pull.zip Quote Link to comment Share on other sites More sharing options...
X64v Posted January 3, 2008 Author Share Posted January 3, 2008 I think you may be on to something. Looking at that graph, along with all my other datalogs, with battery voltage plotted in the lower graph in megalogviewer, my battery voltage goes crazy as the revs increase. Is that normal, or is that a problem for me? Something else to think about: That 2nd gear pull didn't have any misses. These battery voltage spikes are always present as the revs increase, but I only get a miss after at least an hour or so on the freeway. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted January 3, 2008 Share Posted January 3, 2008 If your battery voltage gets noisier as revs increase, then something isn't right. You'll have some amount of noise no matter what, but if it's tied to engine speed, then I'd check all my power and ground connects. There's a lot of good info on wiring at http://www.msefi.com. I suppose you could try putting a noise filter inline with +12V to the MS box, but if the rest of your wiring is good, you shouldn't need it. But with regard to your miss, if the MS is resetting, your datalogs will show it. If they aren't, and the PW and timing values are staying consistent when you feel the miss, then I'd continue looking elsewhere. Quote Link to comment Share on other sites More sharing options...
X64v Posted January 3, 2008 Author Share Posted January 3, 2008 Hmm, battery voltage stability is definitely tied to rpm in my logs. Perfectly steady at idle, increasingly noisy as revs climb. Could this be an alternator problem, or just a wiring thing? My datalogs of the problem don't appear to contain any resets (everything is continuous and consistent). Quote Link to comment Share on other sites More sharing options...
Zmanco Posted January 3, 2008 Share Posted January 3, 2008 A poor ground connection or not grounding everything to the same point can lead to noise. A bad alternator could do the same as well. This is a hard one to trouble shoot without a lot of trial and error. But if you're not seeing resets and the PW and ignition advance values are consistent when you feel the miss, then I don't think you're going in the right direction. Think about it: to oversimplify things, MS is just telling the injectors when and how long to fire, and the ignition systems when to fire. If the logs don't show any anomalies with them when the miss occurs, then it's likely coming from something else. My own experience with misses (different from hesitations) is they are usually spark related. Often one of the spark plug wires has an intermittent open (broken conductor) that's not visible because it's covered by the insulation. It sounds like you only experience it after driving for an extended time. As the wires heat the insulation will expand and could intermittently allow the open to drop the spark. You'd notice it most when accelerating hard. Do you have a spare set of wires to put on? What is the condition of your distributor cap and rotor? Like I said above, my own experience is that these are the more likely culprits, not to mention they are a lot easier to check. Quote Link to comment Share on other sites More sharing options...
X64v Posted January 4, 2008 Author Share Posted January 4, 2008 Everything's connected to a single good ground. I do not have a spare set of wires to check with. Cap and rotor are fairly new, and it's done this since they were brand new. Come to think of it, it's only done this since I started using spark control with megasquirt. When I had megasquirt running fuel only, with a pertronix ignitor in the stock L24 dizzy for spark, I never had this problem. Quote Link to comment Share on other sites More sharing options...
X64v Posted January 7, 2008 Author Share Posted January 7, 2008 Ding ding ding, I think we have a winner. I just commented that it started when I switched to spark control. Well, when I did, I switched dizzies, and while moving spark plug wires from cap to cap, I broke one. I substituted in a fairly new taylor I had from something else that fit just fine... Taylor wires have been a bane for some MS users. I'll be ordering a new complete set of NGK wires and we'll see if that fixes it. Quote Link to comment Share on other sites More sharing options...
niner11 Posted January 8, 2008 Share Posted January 8, 2008 All things being equal I don't think that you could do better than a set of Magnecore wires. I searched a while back and had no idea that taylor wires were so bad. Quote Link to comment Share on other sites More sharing options...
X64v Posted January 8, 2008 Author Share Posted January 8, 2008 So I hear, I'd love to try some, but really I can't afford to drop $80 on a set of wires right now. The NGKs worked before, and at $25 I can give them a shot. Quote Link to comment Share on other sites More sharing options...
z-ya Posted January 10, 2008 Share Posted January 10, 2008 Good yto hear you found your culprit. So I hear, I'd love to try some, but really I can't afford to drop $80 on a set of wires right now. The NGKs worked before, and at $25 I can give them a shot. NGK makes some of the best quality OEM replacement wires you can get. I would use them in all L6 applications where you retain the distributor. For L6s with DIS (no disty), I've used Jacobs and Summit universal kits with great success. Quote Link to comment Share on other sites More sharing options...
X64v Posted January 10, 2008 Author Share Posted January 10, 2008 Good to hear you found your culprit. NGK makes some of the best quality OEM replacement wires you can get. I would use them in all L6 applications where you retain the distributor. For L6s with DIS (no disty), I've used Jacobs and Summit universal kits with great success. Good to know. I always liked the fit and quality of them, hopefully they will fix the miss as well. My fuel pump (OEM junkyard pump) just went out the other day though, so we'll have to wait until my Walbro 255 gets here to see. Quote Link to comment Share on other sites More sharing options...
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