So, about the engine and the Megasquirt. It’s doing GREAT! I have almost 300 miles on the car now, just about a complete tank of gas gone. Seems to be getting good gas mileage, but this is definitely not the tank to be checking that on, since I’ve done so many WOT blasts and such checking out the new motor. I datalogged my trip to work the first time I drove the car to work, and viewed it in the Megasquirt log viewer when I got home. MS Log Viewer graphs any of the parameters you want, and then plays them back like a recording. Really really handy. My first morning’s trip showed me that I was remaining rather close to 14.7:1 at WOT when I merged onto the freeway. So I upped my 90 and 100kpa VE tables by 10% across the board. Datalogged again the next morning and checked when I got home. Perfect 12.6:1 give or take a hair here and there. BUT.. I discovered a big problem in the datalog. The injector duty cycle.. 98.8% at 5800rpm. The Megasquirt manual recommends never exceeding 85% duty cycle on the injectors. And if I ever plan to go above 5800 (yes, yes I do) safely, I’m going to flat out need bigger injectors. First thing I did was hook up a fuel pressure gauge and go for a quick blast up and down the street, just to make sure my fuel pressure wasn’t dropping off, and I had compensated for that. But no, fuel pressure is pretty well rock solid at WOT.
The injectors I’m running are from a Buick V6 originally. I picked them up brand new on Ebay. They were supposed to be 19lb injectors, 19lbs at about 40psi. Well at 55psi, they should have been about 22-23lb injectors. I don’t know why they can’t keep up with my setup. So I’m going to have to swap them out at some point soon. I may pick up a pair of ballast resistors and wire them up in series with my injector banks. That will let me run low impedance TD injectors. I have a multitude of used TD injectors. I’ll probably just grab the smallest ones I have (27lb T1 injectors) and run them. I’m all about being cheap, I’ve got kids to feed.
What sucks about changing the injectors out is I’ve finally got my cranking pulsewidths just about dialed in pefectly, and now I’ll have to start all over with them. I also don’t feel so comfortable using very old injectors. I’d like to be using nice new ones that I know the history of.
That’s about it.. I still haven’t really done any tuning to my fuel tables. It all seems to be working out just fine as it is. My AF ratios were really lean at idle, like 17:1, so I adjusted the tables there to bring it closer to 14.7:1. I still need to come up with some kind of fast idle valve, it’s hard to start when it’s cold simply because it’s not getting enough air to idle up. As I mentioned with the cranking pulsewidths, I’ve been playing with them and have them just about right now. As well as the after start enrichments. The warmup enrichments were very high, and I just turned them down this evening. I’ll have to wait till tomorrow to see if I can get away with that or not.
That’s it for this week. I’ll try to work on a project summary to wrap things up next weekend.