Surge in L67 under hi load/hi RPM

[VX L67 Getrag]

I just pulled 1 of the harder spark plugs to get out, out & it is clean & measures around he 1.5mm mark!

I will try re-gap it but are pretty sure it won't fix the problem.

[ejukated]

Also check the cool terminals, seen a few corroded. Ok after a cleanup but it tends to happen again once the plating comes off

[VX L67 Getrag]

Looks like closing the gaps has fixed it, thank you to all!

The coolant readings seemed pretty steady at the point it was having the issue & the sensor not that easy to get so hoping that's ok!

Thanks again

[ejukated]

No worries, glad you got it sorted. Very common at around 3000-3500rpm to have spark break down when pushing more air on the l67. What gap did you end up with?

[VX L67 Getrag]

T.B.H. not sure as I did it at home before the trip to workshop & just used a hacksaw blade, so guessing about 0.8 & the plugs were the stock BPR6EF-13 so they had a bit of an angle to them!

Normally I'd suggest BPR7EF for anything over 10Psi & then gap them as mentioned previously depending on pressure!

[immortality]

TBH, I think I was having ignition issues with the iridium plugs gapped at the standard (NGK recommended) 1.5mm plug gaps on stock boost running a HSV tune.

I forgot about em as the previous owner had fitted them but it solved a few issues when I closed up the gaps. I only went to a 1.2mm gap as I'm still only on 8psi boost with a CAI and 69mm TB.

[TdracerTd]

Do you guys think there is power in getting the gaps as big as you can?

[Holden202T]

yeah theres a fine line, two small a gap and your wasting spark capacity to ignition the combustion charge, but then go too big and you are going to have opposite issue....

I reckon you need to find the point that is the biggest gap you can have with no missing or silly shit, and that will be different for ever more and every plug type and every coil etc

[ejukated]

Agree, largest gap with non issues would be best however the biggest gap u can run depends on your ignition system and cylinder pressure. I had a miss, at higher rpm full load and perfect afr's after closing the gaps down it reved cleaner and went 5% richer so it's making more efficient use of the air/fuel charge (also saves inj dc )

[immortality]

Yep, I seem to have lost a little fuel economy with closing up the plug gaps even though it now revs out cleanly. Doesn't seem quiet as punchy when you nail the throttle from a standing start either but I may be able to fix that by playing with the tune a little more.