yamaha6611

very strange... or maybe not.. it breaks up in 5th and 6th gear on the highway at like 6500rpm+

1,2,3,4.. all pull great, no issues at all.


i grabbed a .20 feeler and knocked them down from like .26 to .20 ... still same issue..



505hp, twin scroll manifold s366....
short 3inch fender exit exhaust.
upward hood exit twin wategates

IAT at highway speed is like 95-107
coolent temp is 174-185'
AFR is 11-3 to 12.1 ish



tuned by JK tuning... cant imagine something is wrong there lol


help! thanks

matt

AP1Chief

John is my MAN!!!! Hes a amazing tuner. learned alot from him my self


And its pretty normal to see higher gears have spark blow out, because you have a larger load.

I would try a .18/16gap honestly.
I run a 16/14 on high boost setups.

Also, if cylinders are still on the cooler side you can feel blow out.... sometimes i have to get some temp in the engine, like a pull or two before i start doing higher boost pulls.... I have been thinking lately of maybe doing a boost a spark to tackle this

spdracerut

What heat range plugs are you guys running? I'm building a 9.5 CR engine, 91 oct only. Think I need to go a step colder than stock?

outeiroj

running BKR8EIX gapped to .20 ... I had a similar issue in 5th & 6th when I was at .24 and shortening the gap corrected it

Mijae007

I'm at 0.17 on BKR8EIX no more breakup. My car too had some issues at 0.20.