New Turbo Inlet - Engine Dying

[2.5T_/<ouki]

*** ATTENTION: This is NOT due to my BoV being vented to atmosphere. As i have ran my BoV vented for 2 years straight without this issue. This is an RB25 Series 1.

Hi All,

I'm experiencing a problem on my series 1 RB25 that is related to the turbo inlet pipe. I was currently running the stock accordion looking pipe, however i was not running any breathers to the inlet so the ports were blocked off with a MILK carton cap and a screw LOLOL, i know......Anyways, since my tune date is this saturday, i decided last week to "fix" the problem and purchase myself a 3" Aluminum pipe with a 45* bend so i would no longer be using that janky setup. I'm running stock turbo, stock injectors, stock MAF, greddy IM.

Anyhow, now when using the 3" aluminum pipe, my engine likes to stall when slowing down or coming to a stop. It doesn't happen every time, more so like 1 out of 20 times i come to a rolling stop. Now, why is this happening? Could it be that the turbo is just not sucking in hard enough and getting all the air that was just metered from the MAF? Is there a way to fix this problem?

I tested this out by putting back the stock inlet and could NOT make the engine stall, then drove back home, slapped the new 3" on and could make it stall on command.

Thank You.

STOCK ACCORDION

NEW 3" TURBO INLET

Edited February 6, 2013 by 2.5T_/<ouki

[GTSBoy]

Um....it is because you are not running a recirc BOV. What you had before was the stock pipe with a lovely bend in it, plus internal ridges and grooves courtesy of the accordian. What you have now is a nice smooth pipe that doe not follow the same curve as before (the old one bent further to the back of the engine bay). As such you now have a different airflow characteristic across the AFM when the reversion through the turbo happens and it is now shitting itself. Put the old rubber pipe back on and it will stop doing it. If perhaps you remade your metal inlet to mimic the curve of the old rubber one you might get away with it, or you might not - depends on how much the diameter change and ridges/grooves are responsible for the change in behaviour.

You're welcome.

[2.5T_/<ouki]

Um....it is because you are not running a recirc BOV. What you had before was the stock pipe with a lovely bend in it, plus internal ridges and grooves courtesy of the accordian. What you have now is a nice smooth pipe that doe not follow the same curve as before (the old one bent further to the back of the engine bay). As such you now have a different airflow characteristic across the AFM when the reversion through the turbo happens and it is now shitting itself. Put the old rubber pipe back on and it will stop doing it. If perhaps you remade your metal inlet to mimic the curve of the old rubber one you might get away with it, or you might not - depends on how much the diameter change and ridges/grooves are responsible for the change in behaviour.

You're welcome.

Thank you for your response. My BoV has NEVER been recirculated even with the stock inlet pipe so i know it has nothing to do with the BoV being recirculated; i don't even hit speeds/rpms for the boV to open up. Did you bother to read the entire post? I did state that i put back on the stock inlet pipe today as a test and could NOT get the engine to stall, but as soon as i put the new 3" pipe back on, i could make it stall on command.

So, I'm still unsure as to how a "smoother" pipe would cause this to stall? Can you elaborate? It just doesn't make sense to me how it could do this. I was almost certain the ridges were just there so the pipe was able to bend. Would a tune fix this problem as i am able to change variables and things in NIStune?

Edited February 6, 2013 by 2.5T_/<ouki

[scotty nm35]

If you know so much about reversion and it's effects then why ask for our help? What GTS said is spot on, you could possibly fudge the tune enough to get by but it will never work perfectly (and will probably cost you a few hundred in tuning time)

Either put the old rubber pos back on, or plumb back the bov to stop the stalling. Pretty simple. Make sure the bov return faces the compressor wheel.

[GTScotT]

What GTSBoy said is this:

This problem is caused by not having a recirc bov. It actually started happening after you changed the intake pipe because the stock intake pipe is designed to prevent this to some extent. So until you changed the pipe it wasnt bad enough for the car to stall.

The problem is called reversion. Reversion is when you lift off the throttle the turbo will start to slow down and 'flutter' (dose - whether you can hear it or not). The reversion is the soundwaves travelling back up the intake pipe and mucking up the AFM signal, making the engine stall.

Two things that help prevent reversion is A: the stock recirc bov (because it cuts out as much flutter as possible) and B: the stock accordion intake pipe (because the shape/design of it helps stop the soundwaves getting to the AFM).

The stock recirc bov and the intake pipe are both very good at preventing this, and the stock bov also opens with VEEEERY little effort/boost. You would find that putting an atmo bov would cause this problem even when your not hitting boost. its that sensitve.

on my car I have a 3" metail intake pipe, one 90 degree bend and two opposing 45s. I get very little reversion, it runs fine. No bov at all.

[2.5T_/<ouki]

What GTSBoy said is this:

This problem is caused by not having a recirc bov. It actually started happening after you changed the intake pipe because the stock intake pipe is designed to prevent this to some extent. So until you changed the pipe it wasnt bad enough for the car to stall.

The problem is called reversion. Reversion is when you lift off the throttle the turbo will start to slow down and 'flutter' (dose - whether you can hear it or not). The reversion is the soundwaves travelling back up the intake pipe and mucking up the AFM signal, making the engine stall.

Two things that help prevent reversion is A: the stock recirc bov (because it cuts out as much flutter as possible) and B: the stock accordion intake pipe (because the shape/design of it helps stop the soundwaves getting to the AFM).

The stock recirc bov and the intake pipe are both very good at preventing this, and the stock bov also opens with VEEEERY little effort/boost. You would find that putting an atmo bov would cause this problem even when your not hitting boost. its that sensitve.

on my car I have a 3" metail intake pipe, one 90 degree bend and two opposing 45s. I get very little reversion, it runs fine. No bov at all.

OK now there is an explanation i can understand. Thank you for that.

I am not running a stock BoV. Currently, and for 2 years i have been running an atmospheric HKS BoV without it being recirculated and have never had this problem, i guess due to the accordion shaped pipe cutting out most of the "reversion".

I'm pretty sure a recirculated BoV system is out of the question for me as my BoV is REALLY far away from the turbo inlet pipe. It's currently by the battery tray on the Cold pipe. That would mean running a 3-4' hose across my engine bay. Would it be best to put the BoV on the hotpipe and run a short tube from the BoV to Turbo inlet? I've heard it was best to have it closest to the TB......

[Dose Pipe Sutututu]

or just get a new ECU that doesn't use a AFM... problem solved..... less stuffing about..

[2.5T_/<ouki]

I just read a whole article about reversion and looks like you guys are spot on. It said that moving the MAF further away from the turbo would greatly reduce reversion. My new 3" pipe is actually further away from the turbo than the stock accordion pipe, but i guess the ridges in the stock pipe help reduce this. It also said, that people get reversion from plumbing the BoV in the wrong way as it should plumb in a way that the air being recirculated is flowing towards the turbo. Would putting a better screen on my MAF help this problem? My screen is pretty ripped/torn.

I do not have the funds for a stand alone ECU. I will be tuning with NIStune.

[Dose Pipe Sutututu]

If you're using NIStune, then there's another option.. that is moving your AFM into the intercooler piping.. It won't initially run properly, but once you rescale the AFM and adjust the injection table to suit the new readings it will work just fine...

Not to mention you can flutter, atmospheric BOV it's mum and it won't stall.

[Hanaldo]

Easiest/cheapest/best solution is to put the stock bov back on.

[2.5T_/<ouki]

Easiest/cheapest/best solution is to put the stock bov back on.

I do not have a stock BoV. I am thinking about putting my HKS BoV on the Hotpipe and recirculating it back into the turbo inlet AFTER the MAF.

Can someone explain how adding a port on my turbo inlet to recirculate my BoV would help reduce/remove the reversion i am getting? I'm not understanding.

Also, with NIStune running an RB25 I am using a z32 ECU and the z32 ECU's have a "cut fuel" when throttle is closed. Would this stop reversion?

Thanks.

Edited February 7, 2013 by 2.5T_/<ouki

[TTT]

Stock rubber intake is not going to be an issue for the stock turbo.

Put it back on.

cost = free

problem = fixed.

negatives - no hektik metal intake brah

[Dose Pipe Sutututu]

another negative - not 'as' hekkk induction noise

[2.5T_/<ouki]

Stock rubber intake is not going to be an issue for the stock turbo.

Put it back on.

cost = free

problem = fixed.

negatives - no hektik metal intake brah

The stock rubber intake has (2) ports on it. These are plugged with a screw and a bottle cap...........

This is the reason for getting a new turbo inlet pipe.

Can someone please explain how recirculating my BoV into my metal inlet pipe would stop the reversion? If this is the case, I'll recirculate it.

[Dose Pipe Sutututu]

decreases the flutter which disturbs the AFM

decreases/suppresses the reversion/acoustics which disturbs the AFM (same as point 1)

stops your car leaning out like a fat slart on deceleration, the ECU expects this <----> much air going in so it adds this <--> much fuel, if you're just dumping all that air out it riches out the mixture on decel which adds to more stalling

[2.5T_/<ouki]

decreases the flutter which disturbs the AFM

decreases/suppresses the reversion/acoustics which disturbs the AFM (same as point 1)

stops your car leaning out like a fat slart on deceleration, the ECU expects this <----> much air going in so it adds this <--> much fuel, if you're just dumping all that air out it riches out the mixture on decel which adds to more stalling

Thank You.

As of right now, my BoV is vented to Atmosphere on the Cold Pipe side. Wouldn't a vented atmosphere BoV reduce flutter moreso than a recirculated one as a recirculated one is just pumping air back into the system whereas the vented is venting it? I know it will cause my car to run RICH as hell (which i don't like).

So, still using my newly added 3" turbo inlet: Adding a port to it to recirculate the BoV back into it will reduce reversion?

I truly appreciate your guy's help. I am trying to NOT use the stock inlet and just make the modification needed to this new inlet to get it to function properly. I think i will recirculate my BoV if you guys think it will reduce the reversion.

[Dose Pipe Sutututu]

Plump it back, it will make your idle a 'tad' better and won't rich out on decel.. but ideally you want the BOV as loose as possible and with just enough load to close on boost.

The more air is sent back the better...

Or like i said previously, relocate your AFM into your FMIC (post intercooler) and get the NIStune tuned and AFM scaled to suit. Flutter and Atmo BOV all you want...

[2.5T_/<ouki]

Plump it back, it will make your idle a 'tad' better and won't rich out on decel.. but ideally you want the BOV as loose as possible and with just enough load to close on boost.

The more air is sent back the better...

Or like i said previously, relocate your AFM into your FMIC (post intercooler) and get the NIStune tuned and AFM scaled to suit. Flutter and Atmo BOV all you want...

I think i will plumb it back into the inlet after the MAF as recommended. I'm gonna have to have a HUGE ASS hose running about 4' across my engine bay! Going to look so ugly (( My BoV is sooooo far away lmao.

SO FAR AWAAAAY

[GTScotT]

I wouldnt bother plumbing back unless your going back to stock bov in stock position dude.

the aftermarket bovs will require more force to open them and the turbo will still create reversion when the throttle snaps shut, before the bov has a chance to do its thing.

If you are truly limited to the Nistune then your best idea would be to move the AFM to the cold side cooler pipe. Do this before the tune and your tuner should easily be able to rescale the AFM so that it works properly. The problem will be solved and you can keep the HKS BOV and the better intake pipe make sure your AFM is in good condition and doesnt leak.

I wouldnt go back to the stock intake pipe as you will probably end up with a bigger turbo regardless and the AFM will need to be moved anyway. So may as well move the AFM now.

[TTT]

The stock rubber intake has (2) ports on it. These are plugged with a screw and a bottle cap...........

This is the reason for getting a new turbo inlet pipe.

Who cares man... Function over form.

If you don't like the bottle cap and screw, find something more suitable to plug the holes.

Look at all the trouble you have gone to and looking to go further, just so you can have a metal intake pipe which is not giving you ANY benefit what so ever.

Edited February 7, 2013 by TTT