Turbo BRZ Backfiring Under Boost

[Irace86.2.0]

Originally Posted by kobet7

Hi, Here are the logs.
Initial logs post turbo install (RICH): https://datazap.me/u/kobet7/2016-sub...tion-turbo-kit

Fullblown Rev 1 Tune after informing them of my issues (LEAN): https://datazap.me/u/kobet7/fullblown-rev-1-tune

I changed spark plugs and MAF sensor in an effort to cure the hesitation which I also thought was tied to the backfiring under boost. The MAF sensor change actually really helped the hesitation and it is basically gone, but the backfiring did not disappear. I had a shop change the spark plugs and they did not note and damage on the coils. The spark plugs that they returned to me were pretty black which indicated the rich condition which probably went on for months.

I do not believe it is the pump because we opened the basket with my tuner present, and the pump was still where it should be, and it currently has two O-rings.

It is definitely a possibility that the car cuts the throttle, but I would think the car would have rich readings following the loss of power which it doesn't. I can only assume the car gets too lean and the fuel doesn't completely burn which makes the popping. When I say "loss of power" it's not like the car starts decelerating, it's more like the car stops accelerating at the rate it was at and accelerates much slower, but you can definitely feel some sort of light wall it feels like its hitting.

I have now changed the WG spring to 7 PSI and the car does not backfire but that is likely because its running at a lower boost while being lean.

For the second one, the highest throttle angle was like 52%, so you never really accelerated at WOT to see what is going on. Cruising around is harder to analyze than doing a pull at WOT. The first datalog, I found the run below, but it wasn't very close to redline. Again, these are hard to analyze. If you are getting hesitation or breaking up during cruising around and light acceleration then maybe you have an issue with a leak or something. Where are you seeing this as being rich or lean? Can you zoom into a section and highlight what you are referring.

You never seemed to hit wastegate pressure, and you got to around 12psi at 4500rpms, and not going past 4500rpms is probably why you didn't hit wastegate pressure. You seemed to hit a max on the direct injectors and went lean and then the port injectors kicked on a little late. I don't know if this didn't happen before because your throttle position was more aggressive. I'm not sure if this is normal for the tune. Seems like the ports are just on standby until you are on aggressive throttle, but for the boost you are making, the stock direct injectors aren't sufficient without the ports, IMO.

I don't see throttle cut or ignition cut, unless I am missing something.

What fuel are you running? I'm assuming 91 or 93. I wouldn't run 12psi without E85 without knock concerns. Maybe you were having knock events that was causing backfiring-like effects. Looking at my past tunes on my old Harrop setup, my throttle angle at zero accelerator percentage was still 15%+, but yours is zero, or maybe it is calibrated to zero, but it is actually slightly cracked. I don't think it is ever suppose to actually be at zero, but take it for what it is, another thing to discuss with your tuner.

It would be nice to have a datalog from 2500-7k WOT the whole time on the 7psi spring. Chart misfire in cylinder 1-4, total fuel and whatever other parameters might be interesting from the optional menu.

https://datazap.me/u/kobet7/fullblow...zoom=5288-5467

[tomm.brz]

Bad bad bad tune

[AussieBRZ]

Log misfire counts per cylinder or roughness monitors all cylinders , check the di computer is well grounded with all three bolts and mount bracket

Afr target and actual are very different

Long term fuel trims very high over 20% positive

Check fuel pressure from in tank pump is stable at about 60psi