rb20 low boost problem

**evolution23** · 05-02-2011, 04:36 PM

Update:

Found my problem, it was a split line.

Have yet another new problem.... On start up, immediately after the car starts theres a loud sound (sounds like some sort of gearbox or small motor spinning) its very loud and stops after 2 seconds. Sounds like its almost in the dash, maybe it is? Only thing i can think of is the ventilation door moving when the car starts?

**Skym** · 05-02-2011, 06:03 PM

Don't use carb cleaner or brake cleaner. It can damage the MAF sensor.

Use CRC MAF cleaner (link below explains why you don't use carb cleaner) -

http://www.youtube.com/watch?v=vPT8rL0noYg

Or at least use electrical contact cleaner.

With battery, resetting ECU, only need to remove negative cable. But if want to be 100% sure, pull both cables in correct order and stomp on brakes to remove any left over charge.

Oil in rubber intake pipe infront of turbo is normal. It's blowby gas + oil being ejected from exhaust camcover via rubber hose of camcover breather, hardpipe that connects to rubber intake pipe infront of turbo when engine is under boost and at higher rpm. If you want to stop this from happening, fit a oil catchtank.

BOV releasing to atmosphere can make engine run rich after it goes off, best to recirculate when engine has MAF. With aftermarket ECU + MAP sensor, etc, can run it either way.

I would think MAF is making ECU hit boost cut (used when turbo overboost's). Airleak between airfilter, MAF can make this happen, especially if airfilter clamps onto MAF adaptor that bolts onto MAF. Bolt on airfilter (dry type airfilter that has no oil, like Apexi, etc) is usually best to avoid this problem. Or faulty MAF due to using carb cleaner might make it do it.

Rough idle could be due to airleak in rubber intake pipe infront of turbo or airleaks in intake piping. But it's normal for idle to be a little bit rough due to stock o2 sensor. Especially when engine has mods and is untuned or there's a airleak. A long trip on motorway helps to clean sparkplugs, etc and idle is usually smooth afterwards.

Sometimes the airleak can be the gasket under BOV, as it's a use once only type of gasket.

**evolution23** · 05-02-2011, 10:21 PM

YTes my air filter is bolting directly onto the MAF. i took it all off, cleaned the MAF with MAF cleaner today, let it dry then put everything back together as best i can. I am now getting about 5.5 PSI boost, its not bad but i would still like atleast the full 7 PSI. Im looking to get a front mount intercooler and actually i want to replace the turbo with something a bit bigger/better. I was thinking T3 but not sure. And also get a new rad cause mines plastic. Hopefully i get good boost if i replace the turbo, add a front mount intercooler and change over to a metal rad. I will get a new MAF just incase thats my issue and replace the filter as well when i change everything. Any ideas on what type of turbo to go with? The car is for everyday use but i like to have a little fun now and then so i wouldnt mind having more boost. I was thinking around 12 PSI with a new turbo.

Originally Posted by Skym

Don't use carb cleaner or brake cleaner. It can damage the MAF sensor.

Use CRC MAF cleaner (link below explains why you don't use carb cleaner) -

http://www.youtube.com/watch?v=vPT8rL0noYg

Or at least use electrical contact cleaner.

With battery, resetting ECU, only need to remove negative cable. But if want to be 100% sure, pull both cables in correct order and stomp on brakes to remove any left over charge.

Oil in rubber intake pipe infront of turbo is normal. It's blowby gas + oil being ejected from exhaust camcover via rubber hose of camcover breather, hardpipe that connects to rubber intake pipe infront of turbo when engine is under boost and at higher rpm. If you want to stop this from happening, fit a oil catchtank.

BOV releasing to atmosphere can make engine run rich after it goes off, best to recirculate when engine has MAF. With aftermarket ECU + MAP sensor, etc, can run it either way.

I would think MAF is making ECU hit boost cut (used when turbo overboost's). Airleak between airfilter, MAF can make this happen, especially if airfilter clamps onto MAF adaptor that bolts onto MAF. Bolt on airfilter (dry type airfilter that has no oil, like Apexi, etc) is usually best to avoid this problem. Or faulty MAF due to using carb cleaner might make it do it.

Rough idle could be due to airleak in rubber intake pipe infront of turbo or airleaks in intake piping. But it's normal for idle to be a little bit rough due to stock o2 sensor. Especially when engine has mods and is untuned or there's a airleak. A long trip on motorway helps to clean sparkplugs, etc and idle is usually smooth afterwards.

Sometimes the airleak can be the gasket under BOV, as it's a use once only type of gasket.

**beacher1B0** · 05-02-2011, 11:08 PM

What are you using as a Boost reference? Factory or Aftermarket guage? If you r refering to the boost guage in the dash, its not in PSI.

That little Black box where you fixed the vacuum leak I believe is the factory boost guage sender.

Do a boost leak test and see what happens.

**evolution23** · 05-02-2011, 11:17 PM

Yeah im referring to the factor guage, i thought it was in PSI cause it says PSI on it lol. hmm and yeah that little black box that has a small air line run in by the throttle body? Thats the line that keeps breaking on me causing a hissing sound.

I am getting aftermarket guages soon. And sorry this is my first turbo and first JDM vehicle so im not sure on how to do a boost leak test. Im about to start googling it and see what i find.

Originally Posted by beacher1B0

What are you using as a Boost reference? Factory or Aftermarket guage? If you r refering to the boost guage in the dash, its not in PSI.

That little Black box where you fixed the vacuum leak I believe is the factory boost guage sender.

Do a boost leak test and see what happens.

**Skym** · 05-03-2011, 10:31 AM

I thought you were looking at aftermarket boost gauge with psi.

Stock R32 boost gauge uses mmhg. Basically it means mm (millimeters) hg (mercury).

If you look in the right bottom corner of stock boost gauge, it has x100 mmhg. That means you X the reading on the boost gauge by 100.

So +7 (max on stock boost gauge) x 100 = 700 mmhg

and 1 mmhg = 0.01934 psi

So 700 mmhg x 0.01934 = 13.538 psi (roughly)

12psi = 3inch exhaust from factory dumppipe, BOV, podfilter. For 13.5psi add a FMIC. Can retune stock ECU with Nistune.

**evolution23** · 05-04-2011, 12:56 AM

Well thats interested, i thought it was in psi.. lol. Hmm well then i guess the car is running at just over 10 psi currently, it used to run at about 13.5. Could it be the new fuel filter by any chance? Maybe its causing a restriction on fuel delivery?

Or perhaps i messed up the MAF when trying to clean it? there was a fairly large hole in the filter side wire mesh, maybe it got damaged by something or maybe the cleaner i used at first messed it up..

Or maybe its a coil or plug? restriction somewhere before the spark?

Not really sure where to start with this, 10 psi isnt bad but i wouldnt mind having all of the boost back. (i am getting an aftermarket boost guage soon so is i still have the problem in a week or two i can give better readings, also i am going to try and do a leak test if i can locate a shop with the testing equipment)

Originally Posted by Skym

I thought you were looking at aftermarket boost gauge with psi.

Stock R32 boost gauge uses mmhg. Basically it means mm (millimeters) hg (mercury).

If you look in the right bottom corner of stock boost gauge, it has x100 mmhg. That means you X the reading on the boost gauge by 100.

So +7 (max on stock boost gauge) x 100 = 700 mmhg

and 1 mmhg = 0.01934 psi

So 700 mmhg x 0.01934 = 13.538 psi (roughly)

12psi = 3inch exhaust from factory dumppipe, BOV, podfilter. For 13.5psi add a FMIC. Can retune stock ECU with Nistune.

**beacher1B0** · 05-04-2011, 09:34 AM

10 psi is roughly where you should be with a nearly stock Gtst. Exhaust and FMIC will get you up around 12psi. You wont be able to get any more boost out of it without a boost controller.
However a stock rb20 turbo wont last long over 10psi as it will blow out its exhaust wheel into pieces. Ive done it twice.

You were probably getting a reading of "7" becuase of the vacuum/boost leak you had but now fixed.

**DreadedFist** · 05-04-2011, 10:21 AM

RB20 turbos get a bad rap, imo. They will actually hold more than 12psi so long as you keep EGT's under control. It's ultimately the heat from the exhaust gas the weakens the bond that holds the wheel on, which causes it to fail. Run a richer tune under boost to keep EGT's lower.

Of course, it also depends on the turbo itself. Some are in better shape than others.

**M13** · 05-04-2011, 05:12 PM

Originally Posted by DreadedFist

RB20 turbos get a bad rap, imo. They will actually hold more than 12psi so long as you keep EGT's under control. It's ultimately the heat from the exhaust gas the weakens the bond that holds the wheel on, which causes it to fail. Run a richer tune under boost to keep EGT's lower.

Of course, it also depends on the turbo itself. Some are in better shape than others.

they get a bad rep because they suck.