Oil pressure dropping

[Trip]

I have tested this again yesterday, and the problem wasn't related to oil. the car seems to drop the revs when coming off throttle and causes low oil pressure.

Did some more logging with datascan. It seems to be over fueling just after i release the throttle which could be the cause why it dropping revs.

 

[campbellju]

trip, as others said, it does sound similar to my problems. It will be the overun area of the map that is in correct. I just tweaked my map to solve it. I can't remmeber if this was around the same time I believe my inlet manifold was leaking. I'd reused it at the time as I read it would be okay. Nowadays I always put a fresh one in whenever I take the manifold off.

 

[Trip]

trip, as others said, it does sound similar to my problems. It will be the overun area of the map that is in correct. I just tweaked my map to solve it. I can't remmeber if this was around the same time I believe my inlet manifold was leaking. I'd reused it at the time as I read it would be okay. Nowadays I always put a fresh one in whenever I take the manifold off.

Thanks for your response Jim, My ECU is standard, so the problem should not be related to a tuning issue. I must have something else going wrong.

This week i will swap turbo, maf and lambda sensor and do some other testing on the system hopefully saturday I will test again. Its a big pain having the car not road legal since i cannot just test it as i go along.


Jim, I did not understand which part you change when ever you take off the inlet manifold.


Thanks

 

[Trip]

to verify that its over fueling, i downloaded the logs off my datalogger.

 

[campbellju]

Jim, I did not understand which part you change when ever you take off the inlet manifold.

Sorry Trip, I meant the "inlet manifold gasket"

Looking at your chart, It looks like you rev to 4.8K, back off and shortly after i stalls?

I'm assuming the wibbly line (technical term :-D) is where your engine is stalled and your turning it over on the key?

Can you walk us through what you are seeing in relation to the graph?

 

[Trip]

Taking this graph for reference (taken from a PLX devices R500) . For this particualr graph the engine does not stall
On 1038 on the X axis, there is where i let go the throttle and engage clutch. From there on the revs start falling and should stabilise to idle speed (900-1000rpm).
From 1063 on the X axis, you can pretty much see the AFR's going down to rich value and RPM dropping. the zig zak line area is RPM averaging around 600rpm where the engine is almost stalling try to keep alive at such low rpm.


----------------------------------------------------------------------------------------------



This graph is taken from Data Scan. The top blue graph is RPM which shows a similar pattern to the above graph.
The upper red graph is the Injector duty cycle where it shows that the injectors are dumping in fuel just as the rpm reach idle speed.
The Lower dark green graph is showing the MAF signal which is showing that it is sensing air in the system.

It clearly shows that when the MAf stops sensing the "extra air" in the system the injectors duty cylce drops and the RPM's stabilise to idle speed.

My conclusion: Since the MAF is sensing air, the ECU is compensating with fuel (to get a good mixture).. Since this air is not present in the engine, the extra fuel is turning my AFR's to RICH, disrupting the idle. The problem is either a leak and causing the MAF to sense extra air, or electrical problem between the MAF and ECU.


Coincidentally, yesterday I removed the inlet (again) and changed the plenum cover to a standard one since the one i was using had 2 vacuum sources and a AIT sensor bunge. I used liquid gasket sealer on both sides of the gasket hopefully for a better seal.

Today, i will pressurise the system and recheck for leaks.

 

[Trip]

This has been sorted

It turned out to be a stupid loose bolt on the compressor housing on the turbo which was allowing air to come in when off boost and triggering the MAF.