Anyone know how an EFI fuel map really works ?

I have installed the Holley 950 MPI system on my 1982 308, and it runs, but very rough.

I had the system on a thunderbird before, so I know that it does work well, when tuned, but that was only after trying every fuel map I could find.

I spent a lot of time tweaking that system, and tweaking never helped. Only trying every fuel map in town (about 20) until I finally by chance found one that worked.

For the Ferrari, I would like to cut to the chase quicker, but still I have this problem. All the fuel maps I try, it just runs really rough.

Is there anyone out there who really knows how fuel maps work ? If so, I would like to hear from you.


Andy

 

Is this a trick question? ... you mean at the quantum level?

The way a fuel map works is basic in it's nature ... how you measuruing a/f ratio? If you're not you need that tool or you don't stand a chance IMO.

cheers

 

You've got so many threads I'm getting confused

I still need to know what numbers are on the fuel map....MAP and VE? MAP and injection time?

I also still need to know if this is a sequentiall system, semisquential or multipoint??

Luckydynes and I and some others are busy designing/building/programming an ECU from scatch so any of us can give you the help you need, but we'll need more info before we can help. If you don't know the answers a link to the manual for the systen oyu have should have the answers.

 

Not nearly as confused as I am. I have started different threads because the problems seems to be changing over time.

I am running the (version 1.2) Holley 950 ECU, and according to the manual, the numbers in the Speed Density fuel map are MAP vs. RPM (y and x axes) and values in the cells are injector on-time.

The system is "batch" only, not sequential.

By the way, yesterday the car ran like crap, so badly I was about to give up, and today the car ran much better. Not sure why, maybe there is some "voodoo" element in the Holley system I have not decoded yet.

I have read a lot of complaints about the Holley system on other EFI forums, but I like it so far, because it's simple to install, and it was really cheap when I bought it.

I do like the idea of a dedicated 308 ECU though. After spending 2 years fooling around with EFI systems, I appreciate how simple the hardware it, it's ALL in the software.

 

OK, here’s what you want to do I think.

For starters I recommend setting the injection time at full vacuum to 1.3ms, at idle vacuum 1.6ms, and full power to 4.6ms and use the linearize feature (if the software has this)to connect these 3 points with straight lines. Make it the same for all rpms and you will be very close. You will probably find you want to add some fuel in the 4000-6000 and maybe pull some out down below 2000 rpm, but you will be very close and it should run pretty well with 24lb injectors and 42-45pis fuel pressure.

Going beyond this you will need some way to measure A/F ratio as Sean said or spent a lot of time doing plug reads. I’ve never had any problem tuning with a narrow band O2 if your system has one, but be sure to tune off any closed loop control stuff until you get the tuning done. Also on the closed loop topic be sure your maps are rich if anything and the closed loop is pulling fuel out and adding….you don’t want a failed O2 sensor causing the engine to run lean.