Spark Blowout

[ghx407]

Two days ago I got on the 240's pedal WOT and when it hit about 12 psi, it hesitated pretty seriously. Since the car was tuned in Puerto Rico and had never before been boosted in 40 degree weather, I immediately thought that the AFRs had leaned.

So I upped the the fuel about 10% with the SAFC and turned boost down from 15 to 10 psi.

The problem persisted, so I returned the SAFC to its normal settings.

I then removed the plugs, which looked normal. They're about 1.5 - 2 years old, NGK R5671A-8 gapped at .042. (Up until now they had performed flawlessly, including about 10 track days.)

I also tested cylinder compression and got 155 - 160 across the board with 8.8 pistons.

I lowered the spark plug gap to .032 and was able to maintain 10 psi at WOT. When I increased boost to the regular 15 psi, the problem came back.

Tomorrow I'll lower the gap to .028 and give it another go.

Besides violent hesitation on WOT at boost over 10 psi (any RPM), the car runs great. Are my spark plugs on their last leg, or does cold weather affect adequate gapping?

[esahuque]

if the car hasn't had a tune up in about 2 years it wouldn't hurt to go ahead and do a simple tune up, spark plugs (ngk bkr7e), wires, cap, and rotor. also if the car came from Puerto Rico, I would try to get it in a dyno just to see whats going on.

[ghx407]

With the .028 gap the car is occasionally holding 15 psi. I'll give it another go tomorrow with fresh plugs and see what happens.

Between an e-fan motor and tires I just spent about $250; hopefully the new plugs alone will do.

[ghx407]

Tried new plugs @ .042; cutting out between 8-12 psi.

I'll bring them down to .032 and do another run to see if it'll hold 15 psi.

This is what the car is doing:

http://www.youtube.com/watch?v=nFyGbLgA47A

[biggie]

Possible the FP is too high cause too much fuel to go in at high boost?

[ghx407]

FP is at 35 psi under vacuum, 43 - 44 psi with no vacuum.

Lowering the gap to .032 made a huge difference. The car is now consistently holding 15 psi on WOT 5th gear pulls at low and mid range RPMs with only an occasional misfire. Still have to test in lower gears at high RPMs.

Almost there...

[ghx407]

It occurred to me that the blowout might be due to a current/voltage issue, so I unplugged both e-fans and did some pulls again with the .032 spark plug gap. The occasional misfires were still there, so that possibility is eliminated.

Plugged in the e-fans and lowered the gap to .028... Running perfect.