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Can anyone see a reason for this VX L67 with all the regular mod's to surge from around 3500 onwards, I've looked at various logs of it & can't see any real reason for it, it's like the fuel pump is cutting in & out on pressure but I would have thought the AFR would be showing signs?

In this log it does it at the 16:02 to 16:04 time marks, any thoughts would be appreciated.

too much timing can cause surging.

it's only got 9 to 10 degree's at that load point, should really be able to handle 15, but it is a bit lean at that point too around 12.5 to 12.8

what mods? just bolt ons? Whats the plug gap? could try closing it down a bit to say 1mm

it has 10Psi pulley, 1.9 ratio rockers, 69mm throttle body & internals stock.

yeah I'll check the plugs tomoz, I had 1 the other day with same mods less 1.9 rockers & had brand new 1.5mm gapped iridiums & didn't surge but had a miss under hi load/lo rpm.

I had issues with iridiums @ 8 psi with 1.5mm plug gaps. Closing up the plugs got rid of the hesitation/miss.

Yeah honestly if I'm doing the build anything around 10Psi I would go 1.0mm no matter what compound spark plug, anything over 12Psi 0.8mm & then 16Psi+ 0.7mm.

But generally I just tune how it comes in, then if there's issues then causes headaches, I really need to have a better layout as they come in.

but still doesn't really sort out what the surge could be.

L67 gods specify bpr6efs at 0.8 gap for anything over stock boost.

0.9mm gets us past 20psi no missfires turboed and rich

Yeah it's just sort of a rule I like to follow with the above faso I mentioned L67 or any forced induction, no matter what they say about iridium/platinum firing cleaner I don't believe makes that much difference.

Still doesn't really answer the surge, but I will check the gaps!