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Spark plugs only last 100km then misfire? HELP!!!!

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Hi Fellas,

So a bit of background. The Engine is a VVTi 1JZGTE with a Precision 6866 on e85 making 450HP @27psi using Adaptronic 440 ECU. I chose to run Yaris 1NZ coils with NGK BKR7E plugs gapped to 0.7 on a set DWELL of 2ms for direct fire (as VVTi is wasted spark) as we have had good experiences running this setup until now.

The problem arose on the dyno after about 2 hours of heavy tuning. The engine only misfires (feels like spark blowing out) on load after a certain time or distance traveled. It is minor at first but continuing to drive or tune and the problem quickly worsens. Running less boost lessens the threat but the issue still arises, just later on.

Change the plugs and problem goes away...... Drives just as it should, that is until 100kms down the road or 2 hours of tuning on load, then the problem reappears. We are happy to change the plugs as they are cheap and easy to fit however we have an issue here I would like to fix.

Plugs show no signs of fouling or damage. AFRs are 11.8 at their fattest.

Any Ideas?

Cheers, Chad.

What sort of AFR are you seeing on cruise?

Is there any difference to appearance between the plugs when you pull them out?

Could you tell us more about your fuel setup? Fuel pump, injectors, regulator and fuel line material?

Are you monitoring fuel pressures?

Yeh it could be fuel is heating up or pressure drop,

Did you try smaller gap and dwell like 3 Ms,I run 3 Ms fine on these coils.

Power numbers seems low for turbo size boost and e85

I believe this to be the correct dwel settings for those coils

I'm having trouble posting it lol

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