Can overboost fault / fuel cut be caused by manual boost controller ??

[EvenM]

Hello

Been spending a lot of time trying to fix my boost problem. The fault code is the max boost exceeded code and it cuts the fuel. Checked pipes and hoses for leaks. Tfsi coils and new ngk plugs.

The car is chipped and has a manual boost controller installed by the tuner 3 years ago. Today I took it off and replaced it with a straight pipe, and the car didnt cut, but only boosted 0,4-0,5. Now I consider to just drop the mbc and refit the n75 properly and see how that goes, any thoughts ?

[UrS4boy]

No mbc and no N75 = WG spring boost only = 0.4 Bar (ish)

[Error404]

Yes get rid of the MBC **** and find a new tuner!
Only two things cause boost to be pulled - knock / knock sensor fault and over temp signal from MFTS.

[newsh]

Have you actually done a boost leak test with bungs and compressed air?

[newsh]

Yes get rid of the MBC **** and find a new tuner!
Only two things cause boost to be pulled - knock / knock sensor fault and over temp signal from MFTS.

Or excessive boost or a boost leak.
But anyway, boost will not be pulled with an MBC as the ECU has no way of controlling boost without the N75.

How much boost does the car run with the MBC working?

What MAP sensor is in the ECU?

Any mods or changes to the car since it was tuned?

[EvenM]

The connector is on n75, so I believe it has ran with both n75 and mbc, which is an option have read here somewhere. Tried to clean the maf connector without any improvements

The boost peak was about 1,4-- 1,5 bar and then it dropped to 0.8-0,9 on the red line when it ran fine. Had 250kps map sensor untill yesterday, when I changed to 300kps, did not make any difference. It now boost up to 1,2 bar ca for two seconds and then it cut and I get the fault code. I have adjusted the mbc to give much less boost, but makes no difference. Also notice that the boost /spool up is very late


Yes, it now has a oem rs2 turbo, manifold, intake manifold, intercooler and the tfsi coils instead of the original bits. It could be valid reason for it to cut? But it has been working fine for some time after I changed all this. I will have it remapped on dyno, but I want it to run well first.




[/B]

Or excessive boost or a boost leak.
But anyway, boost will not be pulled with an MBC as the ECU has no way of controlling boost without the N75.

How much boost does the car run with the MBC working?

What MAP sensor is in the ECU?

Any mods or changes to the car since it was tuned?

[newsh]

You can't change the MAP sensor without changing the software.

[EvenM]

No mbc and no N75 = WG spring boost only = 0.4 Bar (ish)

Yes, I read that in one of your threads. Will that say that it is the mbc to blame. Or is it maybe a fault that need more boost to be triggered?

[EvenM]

You can't change the MAP sensor without changing the software.

I understand, just tried to change it yesterday to see if there were any difference, but it was not.

[newsh]

If you have software for a 3 Bar sensor fit the chipset, remove the MBC, connect N75 correctly and check that it actually works (blipping the throttle at idle should make it click or do an output test)
If you don't get more that 0.4 Bar Spring boost then disconnect the MFTS and see if it comes back.

Have you checked for a boost leak with compressed air and a bung in the MAF hose??

[EvenM]

Have you actually done a boost leak test with bungs and compressed air?

No, but I have visualy looked at the hoses, taken them off and bent them and seen everywhere for splits and cracks. I know you guys will say I have to do that and I have seen UrS4boy thread about doing it, but I need to buy some stuff and get some help to do it.


The strange thing is that the car can hold boost for two - three seconds and then cut. If it had been a boost leak, wouldnt the boost just peak and cut?

[newsh]

You need to test it with air

[EvenM]

You need to test it with air

I know But will test without the mbc and mfts first. Need to study the thread and buy some stuff to make the air test


Thanks for great advice som far You guys

[Error404]

Or excessive boost or a boost leak.

Neither of these will cause the ECU to disable boost control though

[newsh]

Neither of these will cause the ECU to disable boost control though

That is not my experience