Strange BOOST behaviour

[Z-Kev]

Just fitted a mbc to stop wastegate creep and keep it at 7/8 psi, was setting it up and the first run was waaaaayyyyyy too high, in fact it boosted to 1.5 bar and didnt hit fuel cut at all, how is this possible?

[Nick Mann]

Fuel cut is time dependant in each load cell. If you were in second gear then there is a good chance that you were through the load cell quicker than the time setting needed to react. If you tried again in 4th it would almost certainly cut.

[Z-Kev]

I was doing it in third gear and held it for a few seconds as well?


Fuel cut is time dependant in each load cell. If you were in second gear then there is a good chance that you were through the load cell quicker than the time setting needed to react. If you tried again in 4th it would almost certainly cut.

[Davezj]

Maybe your fuel cut has been removed or raised via and ecu modification in the passed.

i have run 1.5 bar regularly in the past, as i have my boost cut raised.
but as i am told on a regular basis don't go above 1.2 bar as this is the top end of the efficient band of the turbos. Any more is a waste. you are only producing hot air that raises the boost artificially due to the expansion of the hot air. i will have to use a temp probe to prove it to myself though.
but i get told quite regularly that i produce a lot of hot air from both ends.

[Z-Kev]

thx dave, thought it was just strange no boost cut, raised it and now bov is leaking...sigh

[swinks]

If stock dv, then it's not leaking. Simply spring load is soft, pre-set to approx. 0.9 bar.
Go for Evo one or any aftermarket with adjustable spring load.

[Z-Kev]

Think something is leaking, yesterday I could boost to 1 bar easy, today its .7 bar and on gear changes it rises up to .9 bar then drops back down, I think its leaking out under pressure somewhere


If stock dv, then it's not leaking. Simply spring load is soft, pre-set to approx. 0.9 bar.
Go for Evo one or any aftermarket with adjustable spring load.

[swinks]

Yes, that may be boost leak somewhere.

Stock dv issue occurs when boost rises as should then slowly drops with increased revs. I.e. boost target is 16psi, then it will get to 16 psi at 3k, then will hold till 4.8k and since then slowly drops to 13psi at 6k onwards.

[Z-Kev]

Thanks swinks, am going to tighten all pipes tomorrow and change all small vac pipes for silicone



Yes, that may be boost leak somewhere.

Stock dv issue occurs when boost rises as should then slowly drops with increased revs. I.e. boost target is 16psi, then it will get to 16 psi at 3k, then will hold till 4.8k and since then slowly drops to 13psi at 6k onwards.

[Davezj]

Thanks swinks, am going to tighten all pipes tomorrow and change all small vac pipes for silicone

be careful not to loose the resticor pills inside the boost pipes near the boost solenoid.

[Z-Kev]

If I am running mbc do i need the restrictors?
the boost solenoid pipe is blocked off


be careful not to loose the resticor pills inside the boost pipes near the boost solenoid.

[Davezj]

there is one restrictor in the red tip pipe that comes off the big plastic elbow, this pipe goes down to the T piece which has one output to the factory solenoid and the other output goes done to the wastegates.
i think there is another smaller restrictor pill right by the T piece but i am not sure which pipe it is in, i think it could be in the wastegate out side but i am not 100 sure.

you should be able to find the pill by trying to squash the pipe and you should feel a small bump.inside the pipe. the pill is a small bit of metal or plastic with a small hole in it to restrict the amout of flow of air down the pipe.
If the pills are not in place then the boost solenoid can get over power by the boost pressure and not function correctly.

so it answer your actual question yes you should have the pills fitted with an MBC or EBC

[Z-Kev]

OK Thanks Dave


there is one restrictor in the red tip pipe that comes off the big plastic elbow, this pipe goes down to the T piece which has one output to the factory solenoid and the other output goes done to the wastegates.
i think there is another smaller restrictor pill right by the T piece but i am not sure which pipe it is in, i think it could be in the wastegate out side but i am not 100 sure.

you should be able to find the pill by trying to squash the pipe and you should feel a small bump.inside the pipe. the pill is a small bit of metal or plastic with a small hole in it to restrict the amout of flow of air down the pipe.
If the pills are not in place then the boost solenoid can get over power by the boost pressure and not function correctly.

so it answer your actual question yes you should have the pills fitted with an MBC or EBC

[Davezj]

as stated in the PM, here is what you need to reset the engine ecu without resting the A/T ecu and loosing you silky smooth gear shifts.

using this pin out
http://www.clubvr4.com/forum/attachment.php?attachmentid=47530&d=1313157046

you just need to be able to disconnect the wire to the ECU which is called "Backup Power +12V Constant" which is in the bottom section connector.
basically you switch the ignition completely off and then disconnect this wire for 30sec to make sure the power is completely discharged within the ecu. then reconnect wire and switch ignition back on and all fault code will be properly erased without loosing the A?T shift pattern.

personally i used a push fit inline connector on this power line to the ECU rather than a switch, then there is no real way of accidently switching off the backup power when the ignition is on. not that i think it would make a difference if you did turn it off when the car is running as the ECU is fully powered up anyway.

hope this helps

[Z-Kev]

Thanks Muchly dave, have some rep mate



as stated in the PM, here is what you need to reset the engine ecu without resting the A/T ecu and loosing you silky smooth gear shifts.

using this pin out
http://www.clubvr4.com/forum/attachment.php?attachmentid=47530&d=1313157046

you just need to be able to disconnect the wire to the ECU which is called "Backup Power +12V Constant" which is in the bottom section connector.
basically you switch the ignition completely off and then disconnect this wire for 30sec to make sure the power is completely discharged within the ecu. then reconnect wire and switch ignition back on and all fault code will be properly erased without loosing the A?T shift pattern.

personally i used a push fit inline connector on this power line to the ECU rather than a switch, then there is no real way of accidently switching off the backup power when the ignition is on. not that i think it would make a difference if you did turn it off when the car is running as the ECU is fully powered up anyway.

hope this helps

[Z-Kev]

Sorted , loost soft pipe to throttle elbow, back to a solid .8 bar now


Yes, that may be boost leak somewhere.

Stock dv issue occurs when boost rises as should then slowly drops with increased revs. I.e. boost target is 16psi, then it will get to 16 psi at 3k, then will hold till 4.8k and since then slowly drops to 13psi at 6k onwards.

[Nick Mann]

I was doing it in third gear and held it for a few seconds as well?

It still all depends on the amount of time spent in each load cell. It's quite common for people o experience fuel cut on a rolling road when they don't experience it on the road, as the rolling road keeps the car in the load cell for longer than it would do on the road. 3rd gear is where you potentially start to notice fuel cut. The first place to notice is 3000-4000rpm in 5th, then the rev range increases and you will notice it in lower gears as you get more into the forbidden zone!

[Z-Kev]

Thanks Nick


It still all depends on the amount of time spent in each load cell. It's quite common for people o experience fuel cut on a rolling road when they don't experience it on the road, as the rolling road keeps the car in the load cell for longer than it would do on the road. 3rd gear is where you potentially start to notice fuel cut. The first place to notice is 3000-4000rpm in 5th, then the rev range increases and you will notice it in lower gears as you get more into the forbidden zone!