Acceleration enrichment

[wake77]

i'm having a issue with an engine i am tuning it was a carby 308 converted to injection
engine idle's ok the problem is when opening the throttle i get a lean backfire in the inlet.
i have never had to change the acceleration enrichment on any of the engines i have done so far
and was wondering which is the correct table to change is it the AE Multiplier Vs Engine RPM table?

i think the problem is caused from the injector angle in the inlet manifold. they installed the injector at nearly 90 degrees to the inlet runner and i think the injector is just spraying at the opposite wall and pooling not spraying towards the back of the valve.

thanks for any help.

[Jayme]

yep, thats the table I use to change AE, I played with it once and halved it just to see what itd do and ended up with tons of lean backfires whenever the throttle was pressed. i'd times it by 1.5 to start with and see if it still backfires.

got any pics of the inlet manifold? got 2 x 308's that need converting (have to keep carby heads) looking for options.

[wake77]

Thanks for that Jayme i will give that a try.

haven't got any pictures at the moment but i will see if i can get some

[blownvp]

i know a 4 cylinder engine they did the same thing when they converted to efi.this thing would flat spot when you accelerate.i didnt finish the tune on it but the bloke that owned the car his brother finished the tune with a wideband.the bloke said uping the accel enrichment helps but would still have a slight flat spot if you nailed it hard from low revs.let us know how you go cheers darren.

[Holden202T]

yeah i was thinking about it before and theres just not enough low rpm air flow to make it happen quick enough, thats why carby's have the AE nozzles spraying straight onto the butterfly, means the AE gets there before the air!

[wake77]

thanks for the help
i changed the AE Multiplier Vs Engine RPM table and it fixed the problem
i did have to set it to maximum values though 2.55
still have a slight lean spot if you don't accelerate too fast but it's not too bad. and spot on when your really into it

haven't been able to get any photos as yet.

[VL400]

You also have the AE temp factors to play with, the calc is like this .... AE PW = [AE + IDLE AE] x Temp Correction Factor

So increasing the temp factors increases the overal AE, also helps with stumbles when cold/hot only.

[charlay86]

still have a slight lean spot if you don't accelerate too fast but it's not too bad. and spot on when your really into it

might be worth looking at the AE TPS multiplier & AE RPM vs TPS threshold, to fix up the light acceleration lean spot