No boost after engine/turbo upgrade

[gmac78]

Evening all,

Adjusted my F96 yesterday as it was reading 650mb, tweaked it so it was reading 1030mb. Had another we play with the dizzy whilst the car was running and the Hall sender fault codes i've been getting can be triggered by moving the dizzy of timing either direction from the sweet spot. I had a good run out of it yesterday with no more fault codes but i'm still not getting full boost according to my gauge. The most i seen was around 1.65 bar.

I fitted what i believe to be a Motorola 3bar map sensor, it was new in a sealed wee tub but was so small i don't remember seeing any details on it. Is there any way to tell using VCDS etc if it is in fact a 3 bar sensor?

Because i've been resetting fault codes frequently over the last few days any fuel trim data will be be erased from memory. Not sure how long the car takes to adapt but do you think this would affect me achieving full boost?

[UrS4boy]

Because i've been resetting fault codes frequently over the last few days any fuel trim data will be be erased from memory. Not sure how long the car takes to adapt but do you think this would affect me achieving full boost?

Depends how you are "resetting fault codes". I think that to erase the adaptive memory, you need to pull the S27 fuse or disconnect the battery for something like 10 minutes.

[newsh]

No boost after engine/turbo upgrade

Faults can be cleared by removing the fuse for a matter of seconds, likewise adaptation is pretty much instantaneous and real time.
Try in in Vagcom, make a fault by unplugging something while the engine is running. Pull the motor fuse(s) and replace quickly. Check vagcom again, no fault.

[gmac78]

I'm using VCDS to clear the codes. I know when i would clear codes in my RS6 the fuel trim settings would also be reset. I assumed the S2 would be the same but possibly not?

So far with the little use i have had out off car it's not quite the step in power i had imagined over the homefry. I'm still not getting the full 1.9 bar i should be with the V Stream chipset so perhaps once thats sorted it will improve things. Hopefully anyway!!

[UrS4boy]

Faults can be cleared by removing the fuse for a matter of seconds, likewise adaptation is pretty much instantaneous and real time.

Said "10 minutes" to make sure that there wasn't a capacitor still bleeding out.

[newsh]

No boost after engine/turbo upgrade

Evening all,

I fitted what i believe to be a Motorola 3bar map sensor, it was new in a sealed wee tub but was so small i don't remember seeing any details on it. Is there any way to tell using VCDS etc if it is in fact a 3 bar sensor?

The code numbers are on the side of the wee sensor, they are very small aren't they.
It will have 300 written in small print. Anyway as long as you have the right one for the software you will be ok. If you have the wrong one you can get either too little or too much boost.

I think the next place I'd look is the N75 and associated plumbing.

The ECU controls boost by modulating the boost pressure applied to the wastegate lower chamber, if the N75 is sticking or won't open fully or the pipe to the MAF hose is blocked then you can get less than full boost.
The N75 should be plumbed bottom leg of T to cold side, long arm to MAF hose, short arm the WG.

It's always difficult to trace a problem with partly reduced boost, much easier if you're just seeing 0.5bar Spring pressure..

[newsh]

This is a 3Bar MAP
MPXH6300A

[UrS4boy]

G71 Manifold Absolute Pressure (MAP) sensor information

This is a 3Bar MAP

Not sure about that one. I do know this is a 300 kPa = 3 Bar MAP sensor, ala RS2 ECU and chipped AANs and ABYs:



This one too:

http://www.efiexpress.com/catalog/product_info.php?products_id=82&osCsid=1a045f03c0009dfc4c18419f06e962e1

REFERENCE: G71 Manifold Absolute Pressure (MAP) sensor information:

http://forums.quattroworld.com/s4s6/msgs/20417.phtml

[newsh]

No boost after engine/turbo upgrade

Not sure about that one.

I am, look closely you can read the numbers on it.

http://www.mouser.co.uk/Search/m_ProductDetail.aspx?NXP-Freescale%2fMPXH6300AC6U%2f&qs=sGAEpiMZZMvhQj7WZhFIALpLlyV3lh9LgZdi3njH%252bJU%3d

[gmac78]

Morning all,

Not been near the car in the last few days but last night i managed to get a few hours.

I think i've found the reason, or at at least i hope i've found the reason for the boosting issues. After coming back from a wee spin i checked measuring blocks on VCDS and my IAT was sitting at 103 degC. Wow!!!

I let it cool down for a bit then took in out for another spin. With ignition on it shows -49degC and on start up jumped straight away to 70 degC. Out on the road it climbs quite quickly to 97-98 degC and settles there, the temp doesn't drop slightly as you would expect whilst coming on boost either.

Once back from my second spin i checked the inlet manifold temp with a infra heat gun and it was showing 34 degC right beside the sensor, whilst the reading on VCDS was up at 97.7 degC or something.

Whats your thoughts on this? Is this the root cause of my problem?

If it is, can the sensor be calibrated or can a new one be purchased for a 3B?

Thanks
Gordon

[mike74]

I'll get in before Dave does :

http://forums.quattroworld.com/s4s6/msgs/20996.phtml

[K Simmonds]

That's all sounds logical, if your ECU thinks the inlet temp is that high then it's surely going to do something to try and keep the engine safe and have a serious effect on performance. The mid 30's is about right, 100 odd is way too high.

What reading do you get in VCDS if you simply unplug the sensor? I wonder if you see 0 or a default value.

I'm not sure if you can get the sensor new any longer or whether you'd be better off fitting an ABY one instead given that your now your using that ECU, regardless someone should have a good second hand one.

I'm sure Dave will be along with specific info regarding the IAT sensor....

[andy10v]

Glad you found an issue, I would imagine that would cause the ECU to hold back a bit!

3B IAT sensor is attached to the loom.

I would get an ABY IAT sensor, and an ABY connector, fit the ABY connector to the 3B loom and you can then just swap sensors without crimping or soldering in the future.

[gmac78]

Quick response lads, cheers. I've been observing the boost gauge when WOT is applied and you will see the gauge rise steadily to around 1.4- 1.5 bar, then there is a definite pause and a slight drop back by about 0.1-0.2 bar then a slow climb up to 1.6-1.7 bar. I think this is possibly where the timing/boost is getting pulled as you can feel and see it on the gauge.

Like you say, logically it all makes perfect sense and will be quite happy if that is all it takes to finally let me sample the full fat RS2 power. It was quite late when i was tinkering last night so never checked resistance across the sensor as a secondary check, perhaps i can do that tonight before i head offshore tomorrow.

Any other suggestions what i should try tonight with the limited time available?

Thanks

[gmac78]

Andy- Yeh good call with changing over to the ABY system, could do that no probs if i can source the correct bits and pieces. Or a 3B one could be soldered in i guess if one of them becomes available.