| Re: Spectator-Racing is off to the National Championships |
Subject: Re: Spectator-Racing is off to the National Championships by SpectatorRacing on 2008/9/15 20:18:09 Quote:
Great question. I've been asking that over and over. Really "these things" have been the optispark problems again and again.. And each time I think I've got it permanently fixed - spending $500 on an MSD, carefully assembling each one with loc-tite, etc. Still not good enough. This fuel issue actually was a surprise, and I would never have found it had I not dyno'd the car. I have changed absolutely nothing which would affect this since my last dyno (last season), where the A/F ratio was a comfortable 13.2. The motor was running hot (about 10* over normal) on Thursday, but I assumed I was running hard on a hot humid day - it's never been a cool running car. I would not have linked this to a lean condition, but rather a cooling issue. The only two things done to the motor since the last test were the addition of the dynaspark and the change back to a stock throttle body. I can't see how either of those would affect A/F, with the possible exception of the computer misreading something and leaning out the mixture. In fact, logically, the smaller TB should have made the car run rich, as less air was drawn in at the same throttle position. I transferred the sensors from one TB to the other, so it's not like one was bad on the new TB. The logical explanation is that the fuel filter change was the problem, as pressure was more stable after the new one went on. However, it's not a very old filter and the car really doesn't have many miles since it was changed. Unfortunately, due to the circumstances I couldn't make one change at a time, so I don't know which fixed it. I still think the pump may be weak, which is not something I would expect as it was replaced last year (Walbro 255 l/hr). And lastly, it could be getting poor voltage, this has not yet been checked. I keep thinking I've finally made the car reliable, but keep getting bit. I'm really struggling with what else can be done, there is no good solution for stuff like this. It appears that the dynaspark has ended my optispark woes, although I did have a check engine light on the whole race...it's gone now so I can't check what code was set, I think I have to pull of the "opti" again and inspect it just to be safe. Perhaps the fact that the car runs hot is exacerbating an already harsh environment. My plan is to improve that over the winter. But aside from that, it's tough to anticipate anything other than wheel bearing or dirtributer problems. The rest should be a bit more robust. One final comment: keep in mind that there is really no way for me to test changes other than fire the car up in the garage with no load. I can't take it out on the street and see if it runs hot or fails under high RPM's. I'm sure that's a big reason why I find my problems at the track. I will definately end some of these woes once and for all this winter, the stock 1993 computer and harness are GONE. I'm not sure if I'm going to add a '94+ computer or something else altogether, but the simple ability to tune the car on the fly and see what's going on via laptop should alleviate many of these types of problems. |
