weird MAP sensor reading

[Josip]

hello

i have problem with built in MAP sensor readings, we tried different filters but it didn't helped
it happens at about 5500 rpm



car is peugeot 106 gti turbo (TB2538)

log and map are attached

did you have similar problem?

Regards, Josip

[astra vxr]

looks like slight boost spike to me

[Jadzwin]

Make log without MAP filtering. Too much filtering is not good in aspects of engine throttle response.

There are two possibilities: boost spike or ground problem. However the most probably case is the boost spike.

[Josip]

without MAP filtering it is even worse
this is happening always at that RPMs

[Jadzwin]

Please attach the full log here.

[Josip]

log with filter is in first post
in case you need full log without filter i can attach it later

[Jadzwin]

I've checked your log. It looks like boost spike. Maybe there is a problem with the wastegate ?
It is not connected to grounding. Is it internal MAP ?

[Josip]

i am using internal wastegate without boost solenoid at the moment and built in MAP

i wouldn't say that problem is with the wastegate because in those RPMs I can feel lack of power instead more power (rich mixture in that moment) and MAP readings are little different every time on that RPMs

[astra vxr]

i still say its boost spike its not that rich 11.7 at the spike just after that it settles down again

could be a week actuator at them rpm the sorts its self out

[Jadzwin]

I can't see any other reason that the pressure changes in your intake manifold.

The MAP sensors readings look ok and it doesn't depend on the RPM.
I would be nice to see the problem without filtering.

[PSI-Motor]

No missfires? Your running pretty rich for 0,6 bars of boost. Try to get it around 12.2-12.4 in afr or 0.83-0,84 in lambda.
Also post a Scope.

[Josip]

here is log without MAP filtering but i forgot to turn off boost control

look only the first 15 seconds of log because after that I switched to second table



how to post a scope? i only see signal from primary trigger (i don't have secondary trigger or CAM #2)

[Jadzwin]

Where did you connect the vacuum hose from MAP sensor ?

[Josip]

here

[Jadzwin]

I think it is the problem. Try to connect into throttle body to get average pressure for all cylinders.

[Josip]

vacuum hose is now connected to throttle body (where is one screw on picture above) but it didnt helped

then i put fuel filter on vacuum hose like people did with same problems on Megasqurit and now it is ok

[ktsirigotakis]

I like you filter! you can find on junk yards much smaller filter from toyota. they have a small filter between map and intake. any way yesterday i was tuning my friend saxo vts 16v stock turbo with det3 and my map readings were very stable. i toke map reading from the same location that you used

[WHPZach]

How long was the vacuum line to your MAP sensor? The change in pressure due to individual intake events will produce a resonance in the MAP sensor line that's RPM dependent, so your vacuum line was long enough that you saw the signal oscillate at that rpm. Lengthening the line would produce the behavior at a lower rpm, and shortening it would shift the behavior to a higher rpm. As was mentioned, Toyota used a damper on the line to the MAP sensor on many of their engines, so that's a perfectly suitable fix. You can also enable the map filter to a certain degree around the rpm where the oscillation happens.