Rsfours Strange Boost Issue

[Sunkist]

block the vacuum lines going into the boost solenoid.

problem solved.

its noticing a difference in the way the car ramps its boost, and limits it.

hope im right.

[flapsIOW]

Tried to post this earlier, had a few issues with my computer, I apologise if it is a double post.

Been scanning through the topics, and I can't really find a definative answer.

I have a 1998 Series 2 Nissan Stagea RS Four S(neo engined).

It has developed a strange boost issue, after using the turbo for a short period, it will go from making full boost to making only half boost.

If I stop the car and switch the ignition off, start it again and drive down the road, I will get full boost again for a short time, then the issue will return.

The car is standard apart from an apexi air filter.

Always run on 99 ron petrol.

When the car recieved a full service the mechanic noticed, the recirculating dump valve had been disconnected and blanked off. He reconnected it and plumbed it back in, however I didn't experience the boost loss immediately after this had been done.

Is it safe to run the car without the recirculating dump valve? I experienced no issues before the car was serviced, apart from coilpack failure, the car mis-fired and shuddered from 3800rpm to 5000rpm.

I have checked all the hoses and can't find any leaks.

I have been told it could be a temp sensor, near the top radiator hose.

The recirculating valve could be leaking.

The turbo actuator, could be sticking open.

Does anyone else have any suggestions, or let me know if you have experienced this problem.

Cheers everyone

[Chris_Beli]

I'm sure someone will be able to clarify this, but I used to have the same issue, it happened when I ran less then 98 octane fuel, engine would knock and computer would retard boost to factory 7 psi instead of the 11 that it normally ran, so if ur running increased boost on factory computer it could have something to do with this? Like I said I'm no expert just saying that was the case with mine, only use 98 octane and problem has not resurfaced

[Sunkist]

block vacuum lines to boost solenoid.

its for cold start boost and warm boost. it will also revert if boost is increased for whatever reason.

just bypass it by removing and blocking boost solenoid.

[KiwiRS4T]

block vacuum lines to boost solenoid.

its for cold start boost and warm boost. it will also revert if boost is increased for whatever reason.

just bypass it by removing and blocking boost solenoid.

???what??

Test temp sensor by disconnecting the one that goes to the ecu - the three wire one not the two wire one (or the two wire not the one wire - don't have a car to look at just now).. The ecu will revert to stored maps. If it runs better that way get a new sensor. The sensors are relatively expensive and you don't want to replace it just to see.

[Sunkist]

???what??

Test temp sensor by disconnecting the one that goes to the ecu - the three wire one not the two wire one (or the two wire not the one wire - don't have a car to look at just now).. The ecu will revert to stored maps. If it runs better that way get a new sensor. The sensors are relatively expensive and you don't want to replace it just to see.

isnt there a line into a boost solenoid fron the wastegate vacum line. goes into a elctric module, and exits a vacuum line into the suction pipe(filter to turbo)

i saw a thread somewhere in the DIY section explaining how to bypass it to avoid that low boost setting, and runs all the time on hi boost.

i dont think i made sense.

[KiwiRS4T]

You mean like this:

This is the 10 minute no cost boost to 0.5 bar rerouting of the vacuum hoses [thanks to SK]. Disconnect the two vacuum hoses from the solenoid. Then connect the boost feed (from the cross over pipe on the left of the picture) to the standard T piece. Connect one side of the T piece directly to the wastegate actuator (on the right of the picture). The remaining connection on the T piece goes back into the inlet via the BOV return pipe (on the standard fitting). Make sure to put the standard brass restrictor in that vacuum hose to bypass the desired amount back into the turbo inlet. The standard bypass hole of 1.25 mm bypasses enough air flow for 0.5 bar. (See photo)

PS: If you want more boost you can drill out the bypass, 1.5 mm = more boost (around 0.7 bar) 1.75mm = a bit more (around 1.0 bar).

[Sunkist]

yeh thats the one. but thats if he's not running a boost controller and the solenoids just faulting and going back to low boost mode.

[QWK32]

there is no such thing as cold start / warm boost levels on the C34 stagea's, and for the RS4-S there is only one setting, 7psi (it does lift a little more after a fmic and exhaust is fitted). the auto's have the 2 stagea boost switching from 5 - 7psi. i'd say the solenoid is working perfectly fine considering your getting high boost, and that something is triggering it to turn off giving only safe low boost, my bet is with what Chris_Beli said, you are getting some knock causing the knock maps and low boost settings to kick in. turning the car off for a bit resets this.

Shaun, assuming your only running the stock boost control setup, first thing i'd be checking is the base timing with a timing light. it is possible that it has been set a little bit too high, therefore adding a few degrees to the stock timing maps and causing it to knock on load. is the apexi air filter you have a pod filter, if so do you have a heat shield around it? if not sucking in hot engine bay air wont be helping.

running the car with no recirculating BOV and stock ecu in most cases is a real pain in the ass because nissan uses a mass air flow meter to calculate load. with no BOV, when you back off your essentially stalling the airflow meter, no airflow across it means no fuel injected, which leads to constant engine stalling. thats just the main issue, there are others associated with it, do a search of SAU and you'll find tonnes of threads about it.

[lachlanw]

your car is trying to tell you something is wrong .

my car would do that some days if i launched it and wound out 3rd .

there is a big matrix in the manual for symptoms and possible faults .

solenoid off = 7 psi . solenoid on = 10/11 psi . it is on all the time unless something goes wrong .

unfortunately "boost solenoid remains off " come up very often in the chart so it doesnt narrow it down to much .

most likely too much boost . boost on my car became unstable with a fmic and cat back exhaust . could peak to .9 bar .

[Punk72]

I had very similar problem, I bought a turbo tech boost controller and put new spark plug in, never happend again :-)

[flapsIOW]

Thanks for all the suggestions, I am not running any sort of EBC, I added the airfilter after the problem had already started to happen. It is an apexi cone filter, fabricated my own heat shield, and left the airduct on the grill in place.

I will have the timing checked, however I have no idea what the standard timing should be.

Thanks for your help guys.

If anyone else has any ideas let me know.

[QWK32]

I will have the timing checked, however I have no idea what the standard timing should be.

15 degrees BTDC

[bubba]

running the car with no recirculating BOV and stock ecu in most cases is a real pain in the ass because nissan uses a mass air flow meter to calculate load. with no BOV, when you back off your essentially stalling the airflow meter, no airflow across it means no fuel injected, which leads to constant engine stalling. thats just the main issue, there are others associated with it, do a search of SAU and you'll find tonnes of threads about it.

Umm no...

Running no bov means you get reversion through the airflow meter.. air moving through piping gets to closed throttle body, bouncing back through piping and gets chopped up by the air still exiting the turbo, this is the TU-TU-TU sound that VL boys crave so badly.

What happens when this air passes back through the airflow meter is that it gets read again, the afm doesn't know which way the air is moving, just that there is air moving over it. So what happens is, the stock ecu sees more air and throws in more fuel. It is this over fuelling that causes the engine to stall.

[lilcrash]

I had the same problem. Its the boost control. Just buy a boost t and wind it up to 10psi or what ever amount you want.

[lilcrash]

Just to add, having the dump valve open to the atmosphere instead of plumbed in will cause your car to use excessive fuel as the ecu is programed to use the air that gets recycled and pumps fuel in. Unless you mean it was blocked off at the intake pipe side so the valve didn't work, then that will cause back spool and early failure of turbo.( topic for discussion, not everyone will agree to this as there was a few cars factory with out them.)

[QWK32]

Umm no...

Running no bov means you get reversion through the airflow meter.. air moving through piping gets to closed throttle body, bouncing back through piping and gets chopped up by the air still exiting the turbo, this is the TU-TU-TU sound that VL boys crave so badly.

What happens when this air passes back through the airflow meter is that it gets read again, the afm doesn't know which way the air is moving, just that there is air moving over it. So what happens is, the stock ecu sees more air and throws in more fuel. It is this over fuelling that causes the engine to stall.

i understand what turbo reversion is, i ran may car for 6 months or so with it after my turbo upgrade. however i experienced the complete opposite to running rich and stalling. i could have worded it better than saying it stalled the maf completely, my maf output voltage would become very unstable and lower than normal idle time output voltage (so to me thats as good as a stalled meter) and the wideband O2 readout would lean out causing an engine stall.

thats just my experience and hence why i wrote it. i personally haven't seen an engine run rich during reversion, running an atmo bov i have though. i guess afm placement would have an impact on it and could give a different result, my afm/intake setup is very similar to stock in shape and distance from turbo.

anyway in either case it will cause the same result and i regards to the OP's original question the answer is still yes, it is a bad idea to run without a recirculating BOV.

[bubba]

I had no bov for a couple of days (while piping was being fab'd) and it acted pretty well the same as when running the atmo bov (my tune was well on the rich side anyway and you could see big clouds of black smoke heh).

It's interesting that the maf voltage was all screwy, unfortunately I didn't have my carpc at the time so no idea what maf voltage was doing.

[GoldZilla]

Sorry kids, tried to merge the two threads and some weird stuff is happening - flapsLOW's post should be the first post, but isn't...

Hope I haven't upset the flow.