Hey guys, I been street tuning my car and I ran into a problem with it breaking up. I have an ls vtec, 9:2.1 cr, garrett gt3076r, 13psi, on e85, spark plug gapped to .025", AFR is read 11.2-11.7 in boost and car is breaking up. I read my plugs and they are perfect, I'm running 18.25* full boost timing. I do see a problem with the datalog tables because my tps is only reading 2.68v (62%0) when I'm flooring it while the car is moving but if I stop the car and floor it, it will read 4.43v (98%). I believe this is my issue but I want to see if anyone might think this is causing my break ups? I tried 2 brand new tps and still nothing, datalogged with my ecu in a buddies car and his reads perfect WOT, so I'm thinking something's wrong with my harness.

 

I dont think your TPS is to blame. Did you calibrate the TPS voltage? 18.25* table timing or actual timing? Your ignition system might not be up to the task regardless of the plug gap. Whats the condition of your distributor and coil?

 

Ignition system is your issue.

 

I calibrated it and still nothing. I will try another distributor and 18.25* is my table timing

 

But what's also weird is if I give it 50-60% throttle, it will not break up at all even to redline. But anything pass say 75% throttle it will break up. Both are in 13psi

 

+1 vote for the ignition system being the issue. This very same thing happened to me a couple of summers ago. I could not get above ~13-15 psi on my OEM ignition setup on e85.

I researched everything for weeks, tried new distributors - OEM and otherwise - replaced the ICM inside the distributor, tested, tested and tested some more. (If you want to see your spark strength, an inline spark tester really helps.)

You have some options here and maybe a combination of these will help:

1) Incrementally add more timing - listen carefully for your breakup to be resolved & check your plugs as you go. I found E85 to have a pretty forgiving detonation limit.
2) Gap your plugs down more - OEM ignition systems are only so powerful and can only send the spark across the gap up to a pressure point. The more boost, the more pressure the spark has to fight through in the cylinder to jump the gap. At some point it just wont - hence breakup! Some guys run down to .18 to resolve breakup. This will only bandaid your breakup woes for a little while.
3) Upgrade your ignition system. This is what I finally did because 13 PSI was just not an acceptable limit. I went with the Summit/Crane coil/ICM delete setup that you can find well documented around honda-tech. I can now run pretty much whatever gap I choose due to the stronger spark.

I'll leave you with this: Whereas many guys can squeeze more performance out of the OEM system than it was originally designed to give, once the engine heat soaks all of the components underneath the dist. cap (ICM, coil etc.), the spark weakens. Period. I used my inline tester to personally witness this happening first hand. When the engine was cold, or just barely cranked, the spark was decently strong and blue-ish. After driving in the summer heat, the spark became a weak orangey color and would breakup badly once I reached that invisible boost ceiling. After I installed the new ignition setup, the spark was blue healthy and strong all the time. I have since run the car up to 30 psi on e85 beautifully.

Read the following thread thoroughly, this was me and I got some great answers from HT heavyweight champs such as Muckman, theShodan and Turbo-LS (thanks again to everyone, car is still running strong):

https://honda-tech.com/forced-induct...3152918/page3/

 

My first thought is it's too rich. Only 13psi on E85 you should be closer to 13:1 AFR, assuming you're using the gasoline scale.
If you changed your lambda scale to E85 then 11.2:1 AFR is way too lean - you would want to see about 8.4:1 AFR.

You should be targeting inside 0.75-0.86 lambda, to be more precise.

Sometimes I'll get a false wideband reading on E85. It says it's a stable AFR, say .8l but it's actually .6l and the plugs are soaked.

BUT as far as the TPS issue goes, if your ECU is datalogging fine in your buddy's car then you ruled out the TPS and ECU, it's probably wiring. Don't think that's causing your misfiring though unless the ground on your thermostat is corroded or loose. You should take that off and scrub the contacts regardless.