AAN in T3 Syncro 16 - misfire above 10psi boost

[twoqu]

So this is with the new ignition stuff? Thats encouraging other than issues mentioned which may be a consequences of running the automatic sw in a manual car. Not sure I have seen quoted boost figures for automatics although they are rated at the sme output, but typically the manual should be capable of 1.1bar and a bit more during overboost. So we are a bit short but have proved that for some reason the modified ecu/chip is the main cause of the issues.
Ideally we need to get the manual equivelent 551C sw in that standard ecu which means either getting the stock one socketed or converting the modified ecu to run the stock ecu 2.5 map sensor. Frankly a good quality chip for the 2.5bar map sensor will give you the results you want without any of the issues you are having.
I would run it round and see if any fault codes appear. If not then its a case of looking at what might cause loss of boost. Until you are getting repeated stock boost levels it seems pointless in adding to the problems with more power.
For example a member got a sizeable improvement recently replacing the BOV.

[twoqu]

Unfortunately these type of issues need physical examination and assumes that they are plumbed in correctly!
http://www.s2forum.com/forum/showthread.php?t=79611

[RS2]

I'm still with the original coil setup, not the aftermarket setup. I don't see any point in using it as the original setup is working better than the modern alternative.

I don't really agree that we've proved that the issues are caused by the chipped ECU.

The misfire fault only appear when boost is pushed over 18psi. As the standard ECU never gets near that, we haven't proved anything.

The original reason for my using the chipped ECU was that the engine wouldn't boost above 5-6psi. As I proved that the lack of boost was due to the dead MFTS, and now with the original ECU boosting up to 12psi rather than 5-6 psi, there are more things going on here than the ECU I think.

MG

[quattro-nick]

what about dwell time settings?
when you change your oem coils to tfsi coils,should you not change your dwell settings?
i did it with my vems "coil charge time@13.2v = 2.5ms
i dont know anymore what the standaard dwell time is

[twoqu]

As we have said previously the MFTS is not connected to the ecu on the AAN loom so it cannot have had any influence.
So the issue must have been something else. Anything that could cause the boost control system to shut down would have the same effect and it does not necessarily throw a code.
At least with a stock ecu you can work through some of the measuring blocks to see if they are within spec particularly the maf reading. Overboosting and the dreaded abrupt fuel cut are suggsetive of maf related issues.
You clearly have some fuel vapouration problems that might be contributing when demands are higher which is an installation issue.
The usual mantra of boost leak testing and code checking is always a good start.

[RS2]

As we have said previously the MFTS is not connected to the ecu on the AAN loom so it cannot have had any influence.
So the issue must have been something else. Anything that could cause the boost control system to shut down would have the same effect and it does not necessarily throw a code.
At least with a stock ecu you can work through some of the measuring blocks to see if they are within spec particularly the maf reading. Overboosting and the dreaded abrupt fuel cut are suggsetive of maf related issues.
You clearly have some fuel vapouration problems that might be contributing when demands are higher which is an installation issue.
The usual mantra of boost leak testing and code checking is always a good start.

It's very easy to say that (and I am not a specialist on these engines) but after talking to Doug at MRC Tuning, he suggested that the MFTS could be the reason for the boost being low.

Looking at the measuring blocks back then, I remember seeing that the engine ECU was showing a very low coolant temp all of the time. Whether it's supposed to or not, the ECU controls the level of boost in warm up so when the engine is cold, it gets less boost than when it's warmed up fully.

This is what I believe caused the low boost as caused by the fault MFTS.

I changed nothing else to go from very low boost to 22-23psi.

MG

[twoqu]

There are little pearls of wisdom all over the forum. Unfortunately you might have to wade through a few threads to find one using the search function.
http://www.s2forum.com/forum/showpos...3&postcount=17
So that confirms that the logic for the MFTS is in all the ecu's but it is not connected on the AAN models.

[twoqu]

Are you calling the ecu temperature sensor the MFTS? Thats the one on the back of the cylinder head.
The MFTS is the large sensor on the water rail under the inlet manifold that supplies the temp guage signal and overheat signals.

[RS2]

There are little pearls of wisdom all over the forum. Unfortunately you might have to wade through a few threads to find one using the search function.
http://www.s2forum.com/forum/showpos...3&postcount=17
So that confirms that the logic for the MFTS is in all the ecu's but it is not connected on the AAN models.

I think that you're missing the point here...

I'm not doubting what you or this website is stating.

Does the MFTS tell the ECU the coolant temperature?

Is the boost level controlled by the ECU?

Does the boost level go up progressively dependent on coolant temp?

MG

[RS2]

MFTS...



MG

[RS2]

There are little pearls of wisdom all over the forum. Unfortunately you might have to wade through a few threads to find one using the search function.
http://www.s2forum.com/forum/showpos...3&postcount=17
So that confirms that the logic for the MFTS is in all the ecu's but it is not connected on the AAN models.

Reading your link, it states that '3) MFTS fault does not just reduce boost, it drops it to spring pressure.'

This is what I will have been living with, with the old MFTS so it does directly influence the boost level.

MG

[twoqu]

The ecu use a seperate sensor to measure engine temperature.
The temperature guage uses the MFTS on all S models. On The S2 another function (multi) was to tell the ecu of an overheat condition which would drop boost back to mechanical spring level. This function is not used on AAN models as the wiring loom does not connect the MFTS to the ecu.
Thats the point you are missing. If you don't believe us pull the ecu and check to see whether the wiring connector has a wire in Pin 46 position. If you do then you don't have an AAN loom but an ABY loom, and the MFTS would effect boost,
Yes the ecu controls the additional boost level on top of the mechanical level of the spring subject to various imputs. If its satisfied you get extra boost if its not you don't. If you aren't getting enough boost then there is another issue.
We appreciate its frustrating not to have a definitive answer but the help the forum offers is well meaning and above all largely experienced based. There is no obligation to follow any advice given.

[UrS4boy]

Live version of the engine bay device map for AAN, ABY and ADU info

Are you calling the ecu temperature sensor the MFTS? Thats the one on the back of the cylinder head. The MFTS is the large sensor on the water rail under the inlet manifold that supplies the temp gauge signal and overheat signals.

But only the ABY and ADU Engine ECUs receive that overheat signal directly

I think that you're missing the point here...
I'm not doubting what you or this website is stating.
1. Does the MFTS tell the ECU the coolant temperature?
2. Is the boost level controlled by the ECU?
3. Does the boost level go up progressively dependent on coolant temp?
MG

1. NO. The white 2 pin G62 temp sensor at the back of the head tells the ECU what the coolant temp is. ECU does not get that info from the MFTS
2. Yes, via the N75 WGFV
3. Not sure. When coolant is cool, the ECU enriches the air/fuel ratio.

Click on the appropriate label in this live version of the engine bay device map to learn more: http://members.shaw.ca/ajmills/UrS%2...ice%20Map.html

[twoqu]

Anyway lets move on. We are now looking for the lost boost.
Have you actually done a boost leak check? That is pressurising the boost side to ensure its leak free.
Have you checked that the TPS reads at least 90 in the relevant value block at WOT. Do this with ign on and stationary! You will not get full boost otherwise.
Warm the vehicle up and post the 10 basic measurement blocks in case there is a clue there, temperature or maf related.

[twoqu]

The fuel pressure you have mentioned was that with the vac pipe connected or not?
The specs are 4.0-4.2bar without vac and 3.4-3.7bar with vac connected.

Whilst we are on the subject of fueling, what fuel pump are you using and have you changed the supply/return pipes to the 20V turbo sizes or are you running the stock lines?
Essentially the 20V turbo needs high volume/lower pressure than say a K jet pump which uses higher pressure/lower volume. The mininum flow is dependent on battery voltage but you need at least 650cm3 at 12V and 750cm3 at 13V per 15 sec of fuel pump operation.
Just wondering if this is actually a fuel supply issue which is just barely adequate to run the stock engine but runs out of head room when the boost is turned up. Other than that there is the BOV which is probably past its best and the altitude sensor to rule out.
Hopefully some food for thought there for you!