Bmw e46 1JZ bog at high boost

Hi Guys,

Looking for some help please.

It's been a while since I did my tuning course, I purchased a vehicle and due to time constraints on my end I elected to send my vehicle to a reputable and well renowned shop to tune it.

The car runs great, boosts hard and is really enjoyable but I've been experiencing an issue that I'll explain below and the tuning shop does not want to help with resolving it. I've chosen not to pursue further with them and maybe get some advice from the more knowledgeable out there (this forum).

I come from the world of reflashed vehicles so this would be my first entry in to the world of standalones and engine swaps so bear with me please if I'm missing something important.

Vehicle specs:

Bmw e46 1JZ swap on a standalone

GT35 Turbo, bosch 700cc injectors, bosch 044 fuel pump.

Boosting at 1.4 Bar (20 psi)

When coming on to high boost and throttle is flat, occasionally the car will bog down mid pull and then come back alive again - this all happens very quickly, at times it'll buck back and forth and I'll release throttle then it comes fine again. Say I use 90% throttle, the car performs absolutely flawlessly all the way to redline.

I know it's hard to diagnose over the internet but is there anything I can check or a starting point to resolve the problem?

Hi. First of all you need to make some logs - as you know without them it's just guessing rather than analyzing... Out of my experience it can be FPR- there is a couple FPRs of small size that just don't work properly on jz engine for some reason. Also it can be some wire or some sensor. Anyway it's better to get some logs done first.

Muhammed,

As Shota mentioned, a log would help narrow things down. Otherwise the list of possibilities is very long and the more we can shrink it down, the more useful the suggestions will be to you.

Could it be traction control activating?

As said, there are a LOT of things it could be - spark plugs failing to ignite the mixture, over-boost limt, wiring, sender(s), loss of crank'or cam' signal, fuel pressure irregularities - that's from pick-up to return, etc.

Get logs on everything you can and work from there. If you can't log, for some reason, old-school is to use a 'phone to record the display/instruments.

Make a note of ambient variants, too, such as air temperature, altitude, relative density and humidity if available, time running and/or sitting in the staging lanes beforehand, etc.

I'm currently getting a lot of cars from South Africa that have been 'tuned'.

Firstly, which ECU are you running?

Every single one of the cars I've had runs very rich and has very little ignition timing added. I'm guessing this is because the ECUs they have all been running do not allow for fine-tuning but that is a guess

Thanks for the responses and sorry for my delayed response.

The car is running a locally made ECU, spitronics venus.

As I understand it, it's a very very old system.

I'll revert back with logs asap.