[NoTempoLimitN54]

My '09 N54 335i is stock. Getting ready to start the tuning process in the next few months.

I did WOT on the freeway on-ramp and some short pulls on the freeway last night at 50ºF ambient. My P3Cars gage showed that the boost didn't even get up to 7 psi. Max was about 6.8/6.9.

This is with a gallon of E85 added to about 3/4 tank 91 AKI. Based on my calculations, the blend is E10-E12 and this should result in 92-93 AKI. For those that don't know, CA 91 AKI is E 5.7

I've had the gage on the car for over a year. I normally get 8 psi when running E10. My car is just short of 6 years and 72k miles.

Could I be leaking boost from either the stock DV's or the stock charge pipe? Is there a way to confirm that?

Thanks!

[gtaccord]

A boost leak that large would register a code. Did you have traction control fully on?

[wgknestrick]

Make a boost leak test fitting. Need a hose coupler, clamps, plug, pressure gauge, and schrader valve. Use air compressor to boost it up to 20psi, and then spray soapy water over every joint. Bubbles are leaks. Just note that some air will likely leak through piston rings/valves, so it won't hold pressure forever. You'd be surprised how leaky the silcone couplers are if you don't test them.

Biggest source of leaks has always been textured powder coating on IC piping IMO. It's better to have smooth (non-powder coated) surfaces under hose couplers. Make sure you are using T-bolt clamps everywhere, (And not those crappy worm gear clamps shown in the picture). I just found that pic on the internets.

[gtaccord]

Originally Posted by wgknestrick

Make a boost leak test fitting. Need a hose coupler, clamps, plug, pressure gauge, and schrader valve. Use air compressor to boost it up to 20psi, and then spray soapy water over every joint. Bubbles are leaks. Just note that some air will likely leak through piston rings/valves, so it won't hold pressure forever. You'd be surprised how leaky the silcone couplers are if you don't test them.

Biggest source of leaks has always been textured powder coating on IC piping IMO. It's better to have smooth (non-powder coated) surfaces under hose couplers. Make sure you are using T-bolt clamps everywhere, (And not those crappy worm gear clamps shown in the picture). I just found that pic on the internets.

His car is stock. Most of what you mention does not apply.

[Dmacc]

Originally Posted by gtaccord

His car is stock. Most of what you mention does not apply.

Regardless it's still really good info. I've been dealing with boost leaks left and right on my fbo set up. I have anodized intercooler piping and can agree with everything mentioned.

[Jeff@TopGearSolutions]

There are only a few ways to confirm a boost leak.

Either by visual inspection: Obvious signs of cracks in vac lines, pipes or couplers or parts being physically detached or not squared up and tightened down fully.

or

Boost leak test: Applying air pressure to the cold side of the intercooler or cold side of intakes and raising the internal pressure of the system to about 15-20 PSI. A leak would expose itself after that. Generally you can hear it but on a small leak it may require a little bit of soapy water to find bubbles.

Boost Leak Test DIY

With a car like the OP's the first question I'd ask is if you ever replaced the vacuum lines? If not, you can start there as that is just good preventative maintenance regardless and can be done for under $20. Buy about 20 Foot of vacuum line at any auto parts store and replace each line one by one. They go from the turbo's under the engine cover and around to the intake manifold and DV area.

The above link also goes into how you can test the factory DV for a leak.

The boost leak test does require a large set up time so for most its overwhelming but it's the best way to find a leak all said and done. Otherwise if nothing is obvious you unfortunately need to start replacing parts.

A smoke test is no good because it doesn't pressurize the system. A smoke test would only find an obviously large leak. You need the extra pressure that boost pressure test creates as things expand under pressure. Certain rubbers, plastic and seals under pressure expand and only leak then whereas they may not appear to leak or be leaking under lower pressure or at normal atmospheric pressure.

[NoTempoLimitN54]

Great info, thanks guys!

No codes. But I recently got the water pump, thermostat and 6 fuel injectors replaced under CPO. Afterwards I felt like there was more turbo lag. I read up on that software update that increases the lag. I contacted my SA and she said that my software was not updated.

Normally, on our crap ACN91 gas here, I normally only get 7 psi, but adding some 100 AKI, E85, or a combination of both (best result), I'll see 8 psi.

It's possible that the P3Cars gage sensor is not super accurate, but it would be accurate to ITSELF and I thought it was strange that I could only see 7 psi even though I was running 1 gal E85 in about 12 gals of 91 AKI.

wgknestrick, where are you attaching the device in your photo?

Thanks, Jeff, for the suggestion about replacing vacuum hoses. Anybody know where to get vacuum hoses that match the factory stuff (ID/OD, material quality, etc.)?

[wgknestrick]

Unfortunately, I haven't done a boost leak test on my 335 yet.... as I haven't started heavily modding (N55 and have only owned it for 2 months). I'm just talking from 10 years of experience with Subarus across 3 different turbo, IC, and manifold setups that I fabricated. It still applies though.

Ideally, the best place is the turbo inlet because you test the "most". On these cars, that isn't an easy thing to get to....what is, right? Testing at the turbo compressor inlet(s) tests the compressor backplate seal(s), all couplers, IC, etc....the entire positive pressure system. I fixed leaks at just about every connection on my Subaru when I'd test.

You just need to decide what you are willing to do, to perform a test. My motto is anything worth doing is worth doing right. You wouldn't bungie jump and only test the line, but not test your harness, would you? So you take the easy road and test at the IC. Say, The test comes out fine. Is your system without leaks? You don't know that. Was it worth the time to get questionable results? Generally, if you (or someone else) touched it after the initial factory install, you should be testing it....if you think you have a leak, or just want piece of mind.

I can tell you from experience, that a car performs much better with much less lag without leaks. The turbo has to work much less to reach target boost on a system that isn't leaking. You will have a more responsive car that makes more HP.

The O-ring connections that BMW uses on a lot of the fittings work really well though, so I don't want to start paranoia here. However, all O-rings can become compression set over time and cause leaks. Just check to make sure they are still round in cross section and haven't developed flat spots (called "compression set" failure). If you have a car around 80K+ miles, It would be a good idea to replace all of them (Buna N rings are fine) when you have things apart. Orings are cheap from Mcmaster.

Don't get paranoid about this. If you have the traditional silicone couplers and clamps, those have a much higher potential to leak....If you have an aftermarket turbo and had everything off you car, etc. If you are still stock, just check the old faithful suspects visually. I will also say that most systems easily hold 10psi, but few hold 30psi without leaks. If you run high boost on your car, this is something to think about. I'd test to 30psi on my STI because I ran 24psi on 93oct.

As for the IC piping. If you have the textured powdercoating (usually black) on it (note it's powder coat, not anodized) you can remove it via a brass brush grinding wheel. Anodizing is smooth and completely different, not to mention rarely done on IC piping). You just need to remove the coating around the perimeter of the piping where you use the clamps on the couplers to get a better seal. You can leave an overlap so that the bare aluminum is not visible under the couplers.

I have about 3 different sizes of test fittings in my garage, but don't know what DIA the BMW turbos are, besides "tiny". We need to share/post this kind of information once you solve a problem. That way the next person can quickly solve their problem by reading the forum.

The Subaru network was/is so much more advanced than the BMW network....the reason is that people shared information, helped each other, and weren't total assholes 100% of the time. I swear it's 5-10 posts until a BMW thread turns into E-peen comparisons.

[NoTempoLimitN54]

Great info, wgknestrick! Unfortunately getting to the turbine inlets on these cars would not be easy. Plus there are two, so you'd need to pressurize both at the same time.

[wgknestrick]

Originally Posted by NoTempoLimitN54

Great info, wgknestrick! Unfortunately getting to the turbine inlets on these cars would not be easy. Plus there are two, so you'd need to pressurize both at the same time.

I know access sucks....Like the worse setup of any turbo car. You would only need to pressurize one and plug the other though. They are connected. I speak from my perspective, N55, and sometimes forget yours, N54. I see how tight my car is and can't even fathom fitting yet another turbo and plumbing in the same space.

I still don't know why they put the hot side of the engine so close to the strut tower. The engine should be tilted toward the cold side, not the hot side...even better, no tilt at all like all other turbo I6s. I digress though.

[NoTempoLimitN54]

Originally Posted by wgknestrick

I know access sucks....Like the worse setup of any turbo car.

I was thinking something like the BMS dual-cone setup. Remove the air box, cap off and pressurize both turbo inlet tubes. Assuming the turbo inlet tubes are well sealed. I'll be in a position to do something in a few weeks.

They tilted the I6 (15º IIRC), I think to make room for the big complex intake systems on the NA cars. Also makes it a little easier to service the valves and change out spark plugs.

[Tiago@VRSF]

The intake tubes will probably blow off the turbos. I generally lower the passenger side of the intercooler, lower the inlet and run it from there off a 90 degree coupler.

[wgknestrick]

Originally Posted by Tiago@VRSF

The intake tubes will probably blow off the turbos. I generally lower the passenger side of the intercooler, lower the inlet and run it from there off a 90 degree coupler.

I agree. Intake tubes are not designed to take pressure. Let me warn all you, right now. 20 PSI is nothing to take lightly either. When things pop off at these pressures, they do so violently and dangerously. Be cautious and safe when testing.

Like I said, the best place to test is the compressor inlet on the turbo housing. It's not easiest on our cars. You cannot test through inlet pipes because they will blow off at about 5-10 psi. I know that is not the answer you wanted.

[Jeff@TopGearSolutions]

Originally Posted by Tiago@VRSF

The intake tubes will probably blow off the turbos. I generally lower the passenger side of the intercooler, lower the inlet and run it from there off a 90 degree coupler.

Yea, the guy who did the boost leak test via the intake tubes even said after 10 PSI they won't hold pressure.

They are not made to be pressurized and it's also important to note the rear turbo inlet is typically prone to falling off and can be a pain to get back on. Especially with folks who have wrestled with that rear turbo inlet before while installing intakes.

Best method is as you said, lower the passenger side FMIC and do the boost leak from the cold side of the intercooler.

Getting access to the turbo inlets direct is too hard on this car.

Originally Posted by wgknestrick

I agree. Intake tubes are not designed to take pressure. Let me warn all you, right now. 20 PSI is nothing to take lightly either. When things pop off at these pressures, they do so violently and dangerously. Be cautious and safe when testing.

Like I said, the best place to test is the compressor inlet on the turbo housing. It's not easiest on our cars. You cannot test through inlet pipes because they will blow off at about 5-10 psi. I know that is not the answer you wanted.

This is true. Even at 5 PSI you might be able to find a boost leak elsewhere though. So it's really up to the person doing the work if they want to go through the trouble or not with that method. They will never get to 20 PSi for sure with the inlet method.

[NoTempoLimitN54]

Since my last post I noticed that when my engine was off, my P3Cars gage on boost mode was showing about -0.4 psi. That means it is miscalibrated and showing about 0.4 psi less that the boost that really there.

I'm looking for information on how to reset the boost gage.

Also I noticed that after running an entire tank of gas with 1 gal 100 AKI race gas and 1 gal E85 as octane boosters, I finally starting seeing around 8 psi boost again. Maybe it just too a really long time for the DME to recalibrate to the higher octane fuel?

I also got misfire codes on cylinders 4, 5 and 6 and the MIL light illuminated. But there were no noticeable driveability issues. Fortunately I had just passed smog days before. Otherwise this would have caused a delay.

My engine is still stock, it has 6 new fuel injectors and 4k miles on new OEM spark plugs. The dealer recently tested the coils because of another MIL light that happened right as I was picking up the car, and said the coils were OK.

So is this just the DME being overly sensitive to misfire? Also, its been 22k miles since I had my intake valves cleaned. But I've been told that's only needed every 30k. What do you guys think?

I'm going to try again today and clear my adaptations after putting in some race gas and see how she runs.

[cadenceE92]

Originally Posted by Jeff@TopGearSolutions

Best method is as you said, lower the passenger side FMIC and do the boost leak from the cold side of the intercooler.

Getting access to the turbo inlets direct is too hard on this car.

Can I ask what may be a dumb question.

I am considering doing a boost leak test on my N54. You say the best method is to lower the passenger side of the IC and do the boost leak test from the cold side of the IC. Isnt the cold side of the IC the driver side (In the states anyway).

I am just asking for specific clarification on what and where to test.

EX// If I am just pressurizing from the HOT passenger side of the IC inlet then I am not testing the factory couplings that come off the turbo to the IC or the turbo seals. If I do this.. do I not have to plug the TB as well? I did not think the TB was an air tight seal.

Conversely, if I want to test the entire system, will I need to plug one of the turbos inlets, and possibly the TB or CP connection to the TB in order to hold positive pressure?

I guess what I am looking for is what pipes are you adapting to in order to introduce positive pressure. And what connections need to be plugged.

Sorry if this seems rudimentary. I understand how the system works and the concept of pressure testing the system. Your quote above just confused me.

Thank you for any clarification.

[Jklad]

Yes do it through the passenger side fmIC inlet. What I think he means is that through this method you are testing the 'cold side' or everything after the IC.

[mojobmw_e90]

Your running e85 mixture without any tuning. U didn't mention if you had a tuner or not, but if you don't, don't expect more than 8psi out of a stock car