backfiring under boost. NANDO HELP!!!!!

[mikeedler]

any ideas here? car runs great until it starts building boost-- then-- it will backfire and sputter--HARD!(backfired so hard it spit all the insulation out of the resonator)
I can give full throttle until it comes onto boost, then I can only give it about a max of 1/8 throttle to accelerate.

I have tried 3 different sets of NEW plugs, and no luck.-- running them all at the stock gap out of the box. last year I had the same problem when I got the car together- changed the Bosch plugs to NGK-- and problem gone.

yes, I am a ms retard-- motor is 2.7/2.5 head with MSII
what plugs are recommended and to what gap?
thanks.

[Rolla1990]

Do you have overboost protection turned on? Depending on how you have your MS set up overboost protection sometimes acts like a series of backfires.

[weaksauce]

timing?

[mikeedler]

where exactly do I see if the overboost protection is on. I imagine it isnt-- the car ran fine last year, and cant see how it could just turn itself on.-- also when i try to datalog, it locks up my laptop when the backfiring starts.

with the timing-- I havent adjusted anything either-- can it be some sensor???
checked all the plug wires, they are all at about 5,2- 5,6 ohms

[weaksauce]

fuel pressure?
fuel pressure regulator?

[gorilla]

.025 sounds like exactly the symptoms I had my problem was the rotor button on the front of the head under the distributor cap

[nando]

responded to your PM, hoping you can send me a datalog. you said it locks up your laptop? it's likely the USB adapter. any way you can log with the actual serial cable? that always seems to be more reliable.

[coolasacuc]

Do you have overboost protection turned on? Depending on how you have your MS set up overboost protection sometimes acts like a series of backfires.

OFF TOPIC (rolla1990) is that Blackhawk in your sig?

[mikeedler]

repalced the spring in the BOV-- returned it back to 0,5 bar-- runs fine-- no problems.-- well one-- the 10 miles or so i drove it-- killed the headgasket!! i hate this car--fixed now though.

could it be that the maps arent set up to go up to more than 0.7 bar???

[nando]

yeah, probably, don't you have the map issac ran on his stock 200,000 mile 2.5?

the thing that is probably most important is getting laptop communication with megasquirt. It will be much easier to diagnose and fix problems that way, and me or any number of people could help you tune it above .5 bar.

[gorilla]

What its Mike the E30 3.5l turbo how is the bmw mine screams on only 7lbs plan to put megasquirt in from ely

repalced the spring in the BOV-- returned it back to 0,5 bar-- runs fine-- no problems.-- well one-- the 10 miles or so i drove it-- killed the headgasket!! i hate this car--fixed now though.

could it be that the maps arent set up to go up to more than 0.7 bar???

[gorilla]

you usin arp studs