Oil Catch Can - Is it Really Necessary?

[judasentinel]

I never had one on any of my R32s in the past, and on the R33 GTR now, I am having difficulty keeping the rear MAF clean even after driving for a day. Is there another solution to the blow-by, other than putting a catch can that is rerouted back to the pipe between the MAf and turbo?

What is the consequence of venting the fumes from exhaust valve cover into the atmosphere through a filter and just plugging the nipple on the rear MAF-turbo pipe? Will it affect performance or cause any issues with the running of the car?

Also, is there a way to prevent my dual BOVs (Blitz) from reciruclating, as they are causing a lot of surge before the turbos, and its escaping out through the MAFs. Wha point do I need to plug to vent them to atmosphere?

Thank you

[Skym]

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I never had one on any of my R32s in the past, and on the R33 GTR now, I am having difficulty keeping the rear MAF clean even after driving for a day. Is there another solution to the blow-by, other than putting a catch can that is rerouted back to the pipe between the MAf and turbo?

No.

Nismo sells a bolt on oil / air seperator kit for RB26 that drains to the sump.

Other than that you fit at least a 2 litre catch can with the out port recirculated via hose into intake before turbo. The catch can has to have a divider plate between in and out ports on catch can to make sure the oil turns 90 degrees and separates from the blowby gas.

But could have a compressor oil seal failure (common failure for stock turbo's). If pull intake piping off after the turbo compressor housing and find oil in the bottom of the intake piping, then you have your answer.

What is the consequence of venting the fumes from exhaust valve cover into the atmosphere through a filter and just plugging the nipple on the rear MAF-turbo pipe? Will it affect performance or cause any issues with the running of the car?

Engine runs leaner as more oxygen instead of dirty blowby gas enters the engine. Also it's similar to having a intake airleak, so engine might be a tad sluggish.

Also, is there a way to prevent my dual BOVs (Blitz) from reciruclating, as they are causing a lot of surge before the turbos, and its escaping out through the MAFs. Wha point do I need to plug to vent them to atmosphere?

Thank you

Fitting some decent Synapse BOV's fixes surging problem with compressor wheels (hitting the surge line on compressor maps).

[judasentinel]

Im not sure if I can confirm the compressor oil seal failure, if there is one. Any solution to it without replacing the turbo?

If one of the turbos fails due to compressor oil seal failure, will I still make the same amount of boost that I would be if both turbos were working fine. I am still able to make over 1 bar of boost.

The key thing is that there is oil in the piping between the rear turbo and the rear MAF. I have created my own catch can with a 1L bottle, with the exhaust valve cover outlet running into it, surrounded by steel wool, and there is another pipe running from that bottle into the intake pipe between the turbo and the MAF. But there is no pressure at all in either hoses (the exhaust valve cover or the turbo inlet one) on the catch can. Is that normal? I would think that there would be some "sucking in" happening at the hose that runs into the intake piping when thecar is idling or if I rev it, but there is nothing.

I am having a hard time getting to the BOVs as they are tucked inside the front bumper and the only access point is through the turn signal cover. Do I need to remove the bumper to access them and block off the recirc pipe? Could the BOVs be plugged up?

I still hear two sequential whoosh whoosh sounds from the MAFs when I rev the car at idle. I am wondering what causes this. If it is the sound of the recirculating air coming back into the MAF pipe, why is it escaping through the MAF and not going into and through the turbo inlet. Anyone know the causes for it? Could some kind of an issue be preventing the rear turbo from spinning freely that could cause this resistance? Or is what I am describing a normal thing for recirc systems?

[Skym]

Im not sure if I can confirm the compressor oil seal failure, if there is one. Any solution to it without replacing the turbo?

It fails due to out of balance compressor wheel which can be a result of bearing failure (hot shutdown and higher oil temps, bad / old oil or just age). Or maybe loss of exhaust wheel.

If one of the turbos fails due to compressor oil seal failure, will I still make the same amount of boost that I would be if both turbos were working fine. I am still able to make over 1 bar of boost.

Yes, just it makes a whislting sound around 0 on boost gauge (sometimes can be a intake airleak). Then wacking sound when it really starts to fail / fall apart.

The key thing is that there is oil in the piping between the rear turbo and the rear MAF.

Then it most likely is compressor oil seal failure. It gets into the intercooler as well and coats the inside of it.

I have created my own catch can with a 1L bottle, with the exhaust valve cover outlet running into it, surrounded by steel wool, and there is another pipe running from that bottle into the intake pipe between the turbo and the MAF. But there is no pressure at all in either hoses (the exhaust valve cover or the turbo inlet one) on the catch can. Is that normal?

There should be higher pressure at idle. The wool can be sucked into intercooler core / turbo which can do some damage, so not a good idea to use it.

I would think that there would be some "sucking in" happening at the hose that runs into the intake piping when thecar is idling or if I rev it, but there is nothing.

Remove catch can and run a hose directly to intake pipe infront of turbo and T in a pressure gauge (buy a fitting for it from a plumbing supply store or similar that sells brass fittings) on that vacuum hose to see if there is air getting to turbo. I would suspect something might be blocking the vacuum hose to catch can.

Or one turbo has lost it's exhaust wheel.

I am having a hard time getting to the BOVs as they are tucked inside the front bumper and the only access point is through the turn signal cover. Do I need to remove the bumper to access them and block off the recirc pipe? Could the BOVs be plugged up?

As far as I know, have to remove the plastic inner guard that runs into the bottom of the front bumper (bumper side of it via screws) to access the BOV's. Easier if car is on a hoist or off the ground.

I still hear two sequential whoosh whoosh sounds from the MAFs when I rev the car at idle. I am wondering what causes this. If it is the sound of the recirculating air coming back into the MAF pipe, why is it escaping through the MAF and not going into and through the turbo inlet. Anyone know the causes for it? Could some kind of an issue be preventing the rear turbo from spinning freely that could cause this resistance? Or is what I am describing a normal thing for recirc systems?

Most likely the turbo's shuffling. Basically 2x turbo's running at different speeds. Can be caused by the internal wastegates being at different psi. With some aftermarket ECU's you can control each cylinder, so can tune the shuffling out by varying exhaust gas to each turbo to even them out (same amount of exhaust gas).

Some put balance pipes inbetween the dump pipes or intake pipes to balance out the pressure.

Or one of the turbo's exhaust wheels has taken a wander down the exhaust system causing the compressor wheel to be off balance, oil seal to leak on compressor side.

[judasentinel]

I just disconnected the MAF pipe from the rear turbo and revved the engine to see if the rear turbo was sucking any air in....NOTHING!! Could it be a turbo failure, or a wastegate stuck open? The setup is all stock, and it is quite difficult to ascertain....how do I troubleshoot this?

There is no pressure in the intake pipe from the MAF to the rear turbo, and it makes me think that the rear turbo is not spooling at all. Am I running on a single turbo then? Why is there is still 1.2 bar of boost, even though I have the Apexi boost controller set to 0.8 bar? Is it possible that the wastegate is stuck open? How do I check that and how do I fix it?

I am feeling a bit depressed now. Somebody please help.....

Munib

[judasentinel]

Update...

Just did the following:

Disconnected the rear MAF plug with the car running....no change in revs at all. Put the MAF plug back in, the revs dropped and the car almost stalled but didn't. Tried to do the same with the front MAF and the car would stall. Rear turbo failure? Or is it the MAF failure? Could it be blown rear cylinders? I cant do compression test, but the plugs looked fine, and there is no coolant/oil mixing in the engine or in the rad.

Could this be caused by the wastegate failure/stuck open on the rear turbo? Why would the car not stall when I disconnected the rear MAF plug, and why would the revs drop when I plugged it back on? Correct me if I am wrong, but I feel that when I disconnect the rear MAF plug, the ECU doesnt register any change in the airflow, as there is no air flowing through that MAF. And when I plug it back in, the ECU tries to read from the signal it gets from the MAF and thinks there is more air coming in, but there isn't, so the revs drop and then stabilize. Does that make sense?

All signs are pointing towards rear turbo failure to me, unless I am missing something really innocuous and straightforward.

[Skym]

We always worry with these cars, always something going wrong.

Like I said in the other thread, it could be blowby / oil in the intake piping and dropping the booost level might help. Even if there is a oil seal leak on compressor side, dropping the boost level (rpm of turbo drops) would help.

But if there is no pressure then it could be exhaust wheel or failed internal wastegate.

When the internal wastegate fails (wastegate spring has gone soft) you'll hear a rattling sound from the back of the turbo as the wastegate hat moves around and the max boost level will be lower.

To test the internal wastegate you'll need to T in a boost gauge inbetween internal wastegate bulb, compressor housing and add compressed air slowly to the internal wastegate bulb vacuum hose to see if the wastegate opens at the correct boost pressure (as shown in the GTR workshop manual). You should do this with the internal wastegate off the turbo, but can do it with it installed (results / psi the wastegate opens at might be slightly different). There's many how to's on Youtube if unsure how to do it.

With GTR MAF's, as far as I understand the stock ECU sees both voltages and uses the middle ground between the voltage from MAF 1 and voltage from MAF 2. I think that's why you'll find the MAF voltages at slightly different voltages while idling.

If you disconnected one MAF the engine would still start, idle with one MAF. If disconnected the other MAF as well before starting engine the ECU goes into limp mode where it limit's rpm to around 2500-3000rpm via a fuel cut rev limiter and uses a default voltage value (programmed into ECU software by the factory). Only the stock ECU has this feature.

You'll get a MAF error code on ECU if unplug one of the MAF's. Pulling the negative cable on the battery, pressing the brake pedal a few times to drain left over voltage and reconnecting negative battery cable can clear the sensor error code on engine ECU (also resets the dash clock, radio, other devices if they work that way).