Td5 overboosting.

**robbotd5** · 3rd March 2016, 04:46 PM

G'day all.
I've been a bit quiet on here for a while but now I'm using my D2a as my everyday driver again my overboosting problem has resurfaced (mainly through to much loud pedal exerting my authority over toyotas!).
It happens when I'm in 3rd and in 4th. The boost gauge bounces @ 20+ psi and the car bucks a bit. I have a BAS boost box wired into the ECU that is running a BD tune. Am I correct in assuming that the car should not overboost with a boost box fitted?
I don't think it's the MAF over ranging it is reading high 500's low 600's on the nano.
Would bypassing the turbo modulator Defender style proove anything?
I'm at a bit of a loss as to how to fix the issue. It is very annoying when it happens.
Any advice guys?
Regards
Robbo

**Disco Muppet** · 3rd March 2016, 05:40 PM

Bypassing the modulator is not the answer.
Acquire an IRB dual channel anti limit box, Ian from IRB is excellent to talk to, and you should solve your issues.

Sent from my HTC One using AULRO mobile app

**slug_burner** · 3rd March 2016, 05:51 PM

Do you know about what the boost box is meant to do? When does it start to fool the engine management system? When does the boost box allow an over boost condition to be presented to the engine management system? I am asking if you know the transfer function on the boost box.

Do you have a way to measure the actual boost?

**robbotd5** · 3rd March 2016, 06:16 PM

Originally Posted by slug_burner

Do you know about what the boost box is meant to do? When does it start to fool the engine management system? When does the boost box allow an over boost condition to be presented to the engine management system? I am asking if you know the transfer function on the boost box.

Do you have a way to measure the actual boost?

My understanding of the boost box is that is 'bleeds' overboost signal to ground hence tricking the ECU into thinking alls good.
No. I don't know what the transfer function is.
I have a boost gauge and a Nanocom.
Regards
Robbo

**sierrafery** · 3rd March 2016, 07:47 PM

Would be good to know what's the MAP reading on nanocom when it happens?

**robbotd5** · 3rd March 2016, 08:30 PM

Originally Posted by sierrafery

Would be good to know what's the MAP reading on nanocom when it happens?

Ok I'll have a look mate.
Regards
Robbo

**Dorian** · 11th March 2016, 12:59 PM

The ECU uses more than just your boost pressure to determine overboost. It will check that the Air Flow, Temp, RPM and boost pressure, etc "Line Up" , if they start to not line up enough the ECU will go into limp mode, so tricking the boost sensor will only work so far.
Have you checked that you waste gate is not sticking open.
Take the boost controller off the waste gate arm (being careful not to touch the adjustment) and stroke to waste gate fully open, do this a dozen or so times, you will feel if it's sticking. It must be common problem as British Off Road was able to help me over the phone when I had problems with mine several years ago.

Cheers Glen

**D110V8D** · 15th March 2016, 10:42 AM

Mine has also been doing this for quite awhile now, but not all the time.

I've checked stuck wastegate, checked wiring, maf, map, fuel pressure and the list goes on. Everything checks out, although it has been awhile since I last went through everything with the nano.

It feels like it's over boosting but like I said it doesn't do it all the time. On the same day I can pull away at the lights with full power and no symptoms, then, as an example, pull away from the next set of lights and it'll do it.

Have BAS boost box, BAS remap, Boost is set at 22psi and checks out on my gauge.

I've just learnt to live with it. I'd love to hear how you get on with sorting it out.

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