Rising rate fuel pressure

Discussion pertaining to positive pressure E28s.
BATESY
Posts: 428
Joined: Jul 06, 2008 8:42 PM
Location: Renton, WA

Post by BATESY »

here is both my spark map(stole from Brad) and my VE table that autotune made for me. I tried using brads ve table. cant even get the thing to idle. may have to play around with the number later tonight

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marc79euro645
Posts: 513
Joined: Dec 08, 2008 11:33 PM

Post by marc79euro645 »

yeah , I bet it is hunting!
Your spark looks pretty good, you may need to raise rpm bin to say 1100-1200 to create a stable idle plateau.
On the ve, I'd start over with a higher required fuel#, that will allow your ve #'s to be smaller & give you more discrimination as you tune, mines 7.4 req. fuel. This has me idling with a ve plateau of 36, yours will be different, i have 55# injectors.
good luck
marc
turbodan
Posts: 9217
Joined: Jan 09, 2007 10:19 PM

Post by turbodan »

marc79euro645 wrote:yeah , I bet it is hunting!
Your spark looks pretty good, you may need to raise rpm bin to say 1100-1200 to create a stable idle plateau.
On the ve, I'd start over with a higher required fuel#, that will allow your ve #'s to be smaller & give you more discrimination as you tune, mines 7.4 req. fuel. This has me idling with a ve plateau of 36, yours will be different, i have 55# injectors.
good luck
marc
It actually works better the way he has it. Smaller VE bins at low loads means you have less resolution. You have to take bigger steps and sometimes you have to settle for either too rich or too lean.

If I were starting over I'd use "Multiply MAP". My VE bin at idle is 13. Its richer than I'd like, but going down to 12 is too lean.

Regarding the posted VE table, it doesn't take much analysis to realize that the engine won't need almost twice as much fuel at 900 RPM than it does at 1000 RPM. I don't know if autotune did that or what but its all screwed up. VE tables should follow curves. You can have irregularities or bumps here or there but if you've got bins right next to each other that are vastly different its probably not right.
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