Hey guys, I could use your thoughts and/or experience with your PCIII map/fuel trims.. My setup is unconventional as I have a 5th Gen motor (1998) in a microcar (wee!).. Both the intake and exhaust are "Open"; you can't get any less restrictive than what I'm running (wide open/huge intake filter, and an exhaust cutout (meaning no cat/no muffler/nothing...) right at the base of the custom headers (my one-off headers run 28" primary lengths- just as Honda set them up for the bike)... The map I'm running is the most aggressive from Dynojet.. I think they call it map #3 (inventive, I know!)... It's for an 'unrestrictive' intake/exhaust setup.. My concern/issue is that without an outright custom tune (which I may seek out at some point), that I may still be running a little lean.. So, has anyone played with the 3 fuel 'bands' <low/mid/high> that PC lets you add/subtract fuel from (using the buttons of the front of the PCIII unit)? I know it's a bandaid approach, but I'm wondering if I ought to add 2/4/6 percent to any of the 3 zones to get close to where I need to be (I'd imagine I'd only need to add to mid and upper ranges if anything?).. The car runs great as is, but I'm getting ready to really flog it on track days, and I'm worried about running too lean (dangerous for the motor), and just not getting all of the power that I could be making.. Thoughts? Experience? Thanks- -ccrunner
FYI some old related reading: http://vfrworld.com/forums/showthread.php/19036-Staight-pipe-exhaust-running-lean No experience in this area, just some thoughts, so take this for the two cents it is worth. You are right to be concerned about running lean. However without instrumental feedback from the system I do not think you can tell how it is running. Any advise someone gives you is from a significantly different vehicle that may not apply, but meanwhile your risk is serious engine damage. This engine is seriously overbuilt for a bike, but yours is a more stressful application. I am very concerned. Don't burn up your baby. It may run hotter than it would in the VFR because you are loading it down with a great deal more weight. That is in addition to heat caused by any lean condition. My uneducated opinion is that before you stress this engine it needs measurement of the exhaust gas temperatures, and whoever does that can also do a gas analysis and modify the mixture appropriately. Guessing with a richer mixture has risk but the risk is cylinder wash: You can set it to a richer setting and back it off based on performance issues. All the while monitor the oil for gasoline buildup. I couldn't tell which risk is worse, lean or rich, as both are bad if they go on long enough. Just an aside: Did you do any analysis of the pipe diameter? (Been a while since I read your build post.) When the exhaust is wide open it flows too slowly because the (standard) pipe is too large to maintain the pulsing throughout the entire pipe length. The solution is tuning it with smaller diameter pipes. The pressure is preserved end-to-end and results in the exhaust exiting quicker, allowing more overall flow.
http://georgedeanracing.com/index.html My advice if you make contact is to be very specific about the car, what it is exactly and it's overall purpose and use. Micro cars can be a shitload of things from hotwheels to sprints.
Thanks guys for the feedback.. I reached out to George and he got right back to me.. Bottom line, I need to verify what I have with either a tune (process of getting a tune) or use of an AF gauge and adjust from there.. Thanks again- off to do some fine tuning on this thing --ccrunner
