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Discussion Starter · #1 ·
I have a 331 with aluminum heads, performer rpm intake, comp xe274xe (224/232 @ .050 & .555/.565), 24lb injectors, and 75mm tb. I programmed a DIYPNP on my own fox body, plugged it in, and it runs but needs tuning, I haven't driven it much but noticed that it idles at around 65% fuel load. The only info I was able to weed out about that was the VE table needed adjusted, so I used the VE table wizard and was unable to get it to start, basically all my VE settings in the bottom left quarter were 24. I raised them up to 40 and got the car idling, but the fuel load was similar, so I went back to the table I've been working with. Am I missing something or should I just keep working with this table? The only problem I could see is having to adjust the timing and AFR tables to compensate, but it would seem simpler in the long run to just get the VE table to start at that point.

Thoughts?
 

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I would look at your base fuel setting. The one calculated by your basic engine size and number of injectors, size, quantity and number of injections per cycle. This is commonly called "required fuel" or Req_Fuel. Req-Fuel is a calculation factor, and is sort-of like an "overall richness" knob. If you raise Req_Fuel, you will effectively richen the whole fuel map. If you reduce it, you will lean it all across the range. I beleive you have un-set or incorrect setup numbers, because a fresh install should fire-up on whatever the program gives you for VE table and Req-Fuel.

If I understand your situation, it's running OK, but showing a large number for your low-load fuel. That isn't a problem, except that at high loads, you will have ridiculous numbers for fuel, possibly beyond what the system may be able to calculate properly. Whenever possible, you want your max fuel demand (WOT)to be roughly 100 on your VE table, also making idle something like 20 or 30, and cruise 40 or 50. The VE Wizard should give you a VE table like this.

If you use the VE Wizard to set your table, then you need to also set your Req_Fuel by setting your fuel info (injector size, number of injectors, number of injections per cycle, etc.). This will reset your Req-Fuel and provide the correct fuel at that new "24" or whatever idle number. Does that make sense? If it does and it works properly, skip the next paragraph.

I don't want to get you off-track unnecessarily - but if it does make sense, then the alternative (only if you don't have injector info or other info to set your Req_Fuel automatically) is to simply change the entry in your Req_Fuel box rather than calculating it. Run the new VE table with the smaller numbers, crank the car and raise the Req_Fuel until it fires-up. Generally adjust the number as it warms-up. When fully warmed, roughly set the Req_Fuel at something of a reasonable idle AFR, like 14.0:1 just to get going. Note that your idle will be tuned after a short drive as with a hotter cam, idle will be tuned separately. Go for an easy drive. Tweak the Req_Fuel for a good basic AFR number (14.5 to 15.0) at a steady cruise and leave it there.

Tune it. Switch to your VE table, idle down if or as you can, and roughly tune your VE numbers as you go. As you idle-down, just note your AFRs and tweak the VE numbers as you go until you have a solid idle at a good (greatest vacuum/lowest kPa). Believe it or not, that's the hard part. The rest of tuning will be fairly easy from there. At this point, you should have a run-able idle and basic map that will make the car move forward. ;) Start using VE Analyze and tune the mild sections of your table. Go back and tweak accel shot and verify timing is good. Finish-up with tuning the rest of the table.

David
 

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Discussion Starter · #3 ·
Well I gave it a shot this morning, I did the VE generator, then raised my req fuel up until it ran. I actually kept raising it until it maxed out at 65.5, but it only dropped the load % about 5-10%. Seems like it ran better around the parking lot, and I have a feeling this VE table will work out better. I think the top end fuel is there now but I haven't had a real go at it, just free revving.

I will search the internets at lunch and see if I can find some specs for these injectors, and possibly a better estimate of peak hp/tq and rpm. I noticed the rpm drastically changes the ve table. Thank you for the guidance.
 
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