Backfiring after 650 install

[dirtbike_79]

I decided to put my 650 injectors in yesterday, and I spent about 30 minutes or tuning the low throttle point on my afc. I tuned it using low fuel trim and o2 trim, and I have my throttle points set at 30% and 70%. The car runs great at low throttle but I can't go above 30% throttle without it starting to backfire and buck. I have tried setting my high throttle point to the same as my low throttle point, same thing. Tried setting it to 0 and the same thing happens, but if i change the low throttle point to 40% then I can go to 40% throttle before this starts happening. Any ideas?

 

[DSM_PWR]

what are you using to tune it with? wideband/logger/narrowband?

whats your a/f ratio at wot? your either going to be running really rich/lean obviously so just find out which one and +/- the % on the afc

 

[Dave532]

Backfiring is generally caused by 2 things...timing is off or too much fuel igniting near the exhaust manifold on the exhaust stroke.

Assuming your timing is fine, I would assume your dumping too much fuel into the cylinder and all of it is not igniting. Can see your A/F ratio? Can you pull your plugs and see if they are lean or rich? It might also be an injector(s) stuck open.

 

[dirtbike_79]

I am using a data logger and I have a narrow band(waste of money), at wot the car barely wants to run, and there is no knock.

 

[bastard dsm]

did you pull 30-40% of fuel out on the afc?your low and hight points arnt the problem.

 

[dirtbike_79]

I had between -20 to -30 all the across the board on the high throttle

 

[dirtbike_79]

I used http://ca.geocities.com/[email protected]/1GSAFCtuning.htm to tune my car

 

[dirtbike_79]

Can anyone give me a recomendation at what to set my high setting to, so the car will at least run to WOT. I have tried everything from -30 to 0.

 

[kmoore]

Do you have any settings for the high throttle at all?

 

[dirtbike_79]

I have tried setting them from -30 to 0, and I always get the same result. I reset the afc so now i do not have and settings.

 

[bastard dsm]

pull 40% out on high and see if that works,you need to take out more than 30%

 

[dirtbike_79]

So I just took my car for a rip and I ended up making the low throttle -22 across the board. My fuel trims and o2 trim are very close to 100% all the way. I then set my high throttle to -17 across the board and the car would just gurgle and spit at wot after 3500 rpm. Then i decided to try it at 0 across the board same, then +15 and the same thing happened. Then I decided to try -30 across the board, same thing. My o2 voltage was consistently between .80 and .90 on all of then runs, and no knock. Any help would be greatly appriciated! Is 650 injectors and the stock maf just to much for the afc?

 

[dirtbike_79]

I also tryed -40 across the board and I did a WOT pull and the same thing but this time when i was watching my narrowband it basically stopped reading(no blinky lights) while the car was sputering and gurgling.

 

[dirtbike_79]

I also want to mention that when the car is sputering at WOT i am only building about 10 psi of boost, should I try and crank my mbc to about 20 psi and see if that helps?

 

[dirtbike_79]

So i just cranked the boost to 20psi and ended up lowering the settings to 3000/-35 4000/-42 4500/-43 5000/-43 6000/-43 7000/-43, just to get it to run. My data logger went dead so i couldnt log anything, is it safe to run at -50. I am planning to get a 2g maf very soon but I would like to know for now.

 

[pdc]

I'm running 650's in my 2g. I have my high throttle settings in the mid -20's. It is a bit on the rich side but runs strong at WOT. I think it is something beyond your SAFC settings. I'm running 23psi of boost.

 

[dirtbike_79]

I just took my car out for another drive and at the settings that i can get my car to run at im getting 43 counts of knock and if I richen it up it wont even run at wot. Any help would be greatly appriciated.

 

[dirtbike_79]

Any Help?

 

[pdc]

Have you tested for a boost leak? I'd start there.

 

[JG63]

what does you timing curve look like anyways.. and or whats your base timing set at?

 

[JayRolla]

Boost leak test it, and recheck the plugs and wires, running rich like you where may have fouled them. Get a wbo2 as soon as possible, it will take all the guess work out of tuning. Best investment for a dsm.

 

[dirtbike_79]

I did a boost leak test and it had quite a few leaks. So after I fixed them, I took it for another rip and its almost the exactly the same thing

 

[kmoore]

You change the plugs lately? Is the S-AFC hooked up correctly?

 

[dirtbike_79]

The plugs were new when I rebuild the engine, less than 1000 miles on them. My afc is hooked up just like they show on vfaq.

 

[tenn-gsx]

Dude even though you only have 1000 miles on your plugs, they are probably very fouled out from running so rich. Its 12 dollars. Just change them out and eliminate them as a variable.