Having this issue where im breaking up under boost, around 4200 rpms to redline. Issue started after switching from TR6 to BR7EF plugs gapped at .021
Is the plug gap too tight? Timing is only 6 degs at WOT, AFR is 11-11.8:1 under boost, its on a conservative tune until i get everything sorted out. Ran real good with the TR6 plugs, gapped at .035, even lower boost (4.4psi) and lower timing (3-4 degrees). Initially thought too low of timing, added 3 degrees and still does the same thing. Both wideband and NB show no leaning out when it starts breaking up. Any ideas? Lost over a full second 0-60.

2008 NNBS 4.8 Stock everything
93 octane only
7875 turbo
80lb decapped flowed and leak tested
44mm wg
50mm BOV
3" downpipe


Here's a copy of the log

 

My first thought would be to switch back to TR6 plugs but maybe that is too obvious lol

 

Why'd you change plugs if the TR6 were working for you?

 

lol the thought has crossed my mind, I changed them because I plan on running higher boost in the future. I’ve heard mixed reviews on the projected tip tr6 plugs. Some say the heat range is too hot and some run high boost just fine, but those people are usually on e85. I wanted to keep this build as safe as possible until I get the motor built. So I went with br7ef plugs to be on the safe side.

 

Because I wanted to be safe. When I pulled them the timing mark showed a hair or two below the bend in the strap which suggests it’s on the hotter end. 🤷‍♂️ I just wanted to be safe with everything so I went with low timing, low boost and fat fuel until I get all the kinks worked out.

 

Switch back

 

Sounds like a plug issue to me but you could have a bad O2 sensor, I had one go out and it gave me a noticeable miss/stumble when in boost. I really liked TR7s in my 4.8 with 15+psi never had an issue with them.

 

I might end up doing that, going to check for spark arcing later tonight first

 

Tr6s or BR7?

 

99.9% sure they were TR7XI #3690 truck didn't make that much power cause TVS1900 turned way up on a stock engine is not that efficient but it never had spark issues on 93oct. When the belt didn't slip it would see 18psi on a cool day.

I also had no issues with TR6s at that boost level and according to my amazon history, I've purchased half a dozen TR6s and only 2 sets of TR7s so I vote to go back to the 6s and see if it fixes the issue.