What is a "REAL" boost leak test?

howslowcanyougo · 08-04-2005

Been trying trace down a boat load of Boost leaks after I installed a new FMIC and a small 20G.

@ WOT the car sounds like a broken gas main, and gives off a gaint PSHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH, sound like I've never heard before?

Why now, does this thing sound like it's leaking so bad?

And the car actualy fells a bit SLOWER than before?.....:-<

I've found a leaks off the the IC pipe, and the PVC valve and corrected or blocked them off.

The car still won't hold Boost, it leaks out almost as fast as I can pump it in with the compressor?

Cause I'm now finding leaks on biss, injector and TB shaft seals?

I've talked to a local un-named "DSM Guru" and he said that I'm being "anal" by doing the boost leak tests, and that these smaller leaks, like on th TB shaft, biss and injector seals, are too small to even matter, and that the turbo should "make up" for these kind of leaks?

My questions is what is a "REAL" boost leak test?

I've read else where that it should be able to hold it at whatever the amount of LBS od boost, that you plan on Boosting at WOT, and it should hold there for about 30 seconds?

Is this "anal" or not? Are the "smaller leaks" imporatant or not?

Many Thanks in Advance................

Howie

**Shane@DBPerformance** · 08-04-2005

The BISS and TB shaft are common leaks that often aren't worth fixing, since they are tiny and sometimes hard to fix. You should fix any leaks at the injectors, leaks there can be fixed and they can turn into large leaks quickly.

Are you using an air compressor? It should be able to maintain a decent boost level for a bit, unless it's a small tank.

Alpine TSi · 08-04-2005

Keep in mind with new hard pipes and a bigger turbo you will actually hear the air moving through the IC/pipes and actual spool up. I remember that when I got my car back from QPR last summer and I thought it was a big ass boost leak but was actually the sound of air moving through 2.5 stainless pipes. Later that season we did a boost leak test and only found one at where I blocked off the PCV fitting on the intake manifold.

howslowcanyougo · 08-04-2005

Quote:

Originally Posted by ecoli

The BISS and TB shaft are common leaks that often aren't worth fixing, since they are tiny and sometimes hard to fix. You should fix any leaks at the injectors, leaks there can be fixed and they can turn into large leaks quickly.

Are you using an air compressor? It should be able to maintain a decent boost level for a bit, unless it's a small tank.

Yep I'm using a compressor. So should the "boost system" HOLD the pressure I'm putting in with the compressor on the Turbo inlet for like 30 seconds or not?

The car does spool ~3600, and hold 20lbs on the gauge to redline?

But I does seem a like fair amout of air is leaking out of the TB Shaft and Biss seals?

Guess I can start with the Injectors first?

Do I need to release the fuel pressure some how before removing the fuel rail to replace the seals? Do I need to buy new insulators as well as the seals?

Any links to a good tech articles or walk throughs for this n00b, who has never installed a fuelrail or injector seals?

TIA......

howslowcanyougo · 08-04-2005

Quote:

Originally Posted by Alpine TSi

Keep in mind with new hard pipes and a bigger turbo you will actually hear the air moving through the IC/pipes and actual spool up. I remember that when I got my car back from QPR last summer and I thought it was a big ass boost leak but was actually the sound of air moving through 2.5 stainless pipes. Later that season we did a boost leak test and only found one at where I blocked off the PCV fitting on the intake manifold.

Thanks for your input!

If there wasn't a big boost leak "somewhere" I probably shouldn't have a problem with DSMLINK reporting that I'm ok running at a ~18/1 A/F, but when I richen it up to where DSMLINK reports close to 11/1 the car bogs and back fires?

This leads me to believe that the Mas is measuring Air that never makes it to the motor, there by giving the symptom of running ok while that lean?

Does this make sense, or am I way off base?

I'm really trying to diagnose the weak power, strange loud noise and weird DSMLINK reading symtoms to get this car back on base?

TIA.....

**Shane@DBPerformance** · 08-04-2005

I never tried the pump it up with a bicycle pump or whatever method for checking boost leaks. I can't imagine it works the best or gives you the best idea of how bad a boost leak exactly is without some actual CFM going through the system. Don't expect it to hold perfect pressure though, even with no boost leaks, it will all eventually get out in the motor anyways.

Insulators are the seals. Buy new ones from Mitsu, they get old and hard over time causing leaks. You can try to relieve the pressure one way or anything or just pull the fuel rail off and be ready for fuel. There will be fuel no matter what you do. Just don't drop the 3 black fuel rail spacers, they can get lost in the 2G intake manifold, you might want to tape them to the head before pulling the rail off.

howslowcanyougo · 08-04-2005

Quote:

Originally Posted by ecoli

I never tried the pump it up with a bicycle pump or whatever method for checking boost leaks. I can't imagine it works the best or gives you the best idea of how bad a boost leak exactly is without some actual CFM going through the system. Don't expect it to hold perfect pressure though, even with no boost leaks, it will all eventually get out in the motor anyways.

Insulators are the seals. Buy new ones from Mitsu, they get old and hard over time causing leaks. You can try to relieve the pressure one way or anything or just pull the fuel rail off and be ready for fuel. There will be fuel no matter what you do. Just don't drop the 3 black fuel rail spacers, they can get lost in the 2G intake manifold, you might want to tape them to the head before pulling the rail off.

Shane, I have a Big tank craftsman compressor, NOT a lame bike pump man!

Thanks again for the good tips!

Dinkpit · 08-04-2005

try soap/water mix, should work at any psi, just watch for the bubbles. :P cheap too, also on ur tb, injectors spray the area with carb cleaner......idle goes up... leak

howslowcanyougo · 08-04-2005

Quote:

Originally Posted by Dinkpit

try soap/water mix, should work at any psi, just watch for the bubbles. :P cheap too, also on ur tb, injectors spray the area with carb cleaner......idle goes up... leak

Soapy water is how I found the Injector and Biss leaks, carb cleaner on the injectors is a good idea too!

Thx!

**Shane@DBPerformance** · 08-04-2005

Quote:

Originally Posted by howslowcanyougo

Shane, I have a Big tank craftsman compressor, NOT a lame bike pump man!

Thanks again for the good tips!

Yea, I read that wrong the first few times.

Dinkpit · 08-04-2005

btw, make sure to lube the inj. O-ring before reinstalling them... and check for cracks, breaks..etc.

howslowcanyougo · 08-04-2005

Any comments on this???

If there wasn't a big boost leak "somewhere" I probably shouldn't have a problem with DSMLINK reporting that I'm ok running at a ~18/1 A/F, but when I richen it up to where DSMLINK reports close to 11/1 the car bogs and back fires?

This leads me to believe that the Mas is measuring Air that never makes it to the motor, there by giving the symptom of running ok while that lean?

Does this make sense, or am I way off base?

I'm really trying to diagnose the weak power, strange loud noise and weird DSMLINK reading symtoms to get this car back on base?

TIA.....
__________________

Alpine TSi · 08-04-2005

What kind of MAS are you using?

howslowcanyougo · 08-04-2005

Quote:

Originally Posted by Alpine TSi

What kind of MAS are you using?

OEM 2G Mas, with the default 2G MAs setting on v2.5 of DSMLINK.

Alpine TSi · 08-04-2005

Ok, so if you were to have a boost leak, since your MAS is before your turbo and IC, you would be losing metered air. Therefore the ECU will add more fuel than is actually needed, which would create problems while under boost, bucking, backfiring, etc... I had a similar problem when my ECU was acting up last summer and I would go under 10:1 with any amount of boost than the car would hate me and buck real hard for a moment until all the unburnt gas got out of the cylinders. Now when you add fuel by richening the sliders on DSMLink, yes you would be adding even more fuel and not helping anything at all, and causing the symptoms you list. So yes, your thinking is correct in your situation. For those of us that have MAF-T's in blow through it doesn't matter because the air doesn't get metered until it going into the TB, so there would have to be a pretty big leak there to cause anything. Not that buying a GM MAS setup is the fix, as it only hides a problem, but just the other scenario, which obviously doesn't apply to you.

Get those leaks taken care of and go from there. Also, are you using a wideband O2? Or are you just going off of the claculation that DSMLink makes for you? If using DSMLink, do you have its individual settings set right? Then also you have to realize it is going off of data that also involves your MAS, which isn't telling the ECU the right info with all those boost leaks. Plus in the end the AF ratio function built into DSMLink is just an estimation, not something I would completely rely on. IE to get the backfiring and such you are now, you are probably going a lot lower than 11:1 like it said.

Hope this helps.

howslowcanyougo · 08-04-2005

Quote:

Originally Posted by Alpine TSi

Ok, so if you were to have a boost leak, since your MAS is before your turbo and IC, you would be losing metered air. Therefore the ECU will add more fuel than is actually needed, which would create problems while under boost, bucking, backfiring, etc... I had a similar problem when my ECU was acting up last summer and I would go under 10:1 with any amount of boost than the car would hate me and buck real hard for a moment until all the unburnt gas got out of the cylinders. Now when you add fuel by richening the sliders on DSMLink, yes you would be adding even more fuel and not helping anything at all, and causing the symptoms you list. So yes, your thinking is correct in your situation. For those of us that have MAF-T's in blow through it doesn't matter because the air doesn't get metered until it going into the TB, so there would have to be a pretty big leak there to cause anything. Not that buying a GM MAS setup is the fix, as it only hides a problem, but just the other scenario, which obviously doesn't apply to you.

Get those leaks taken care of and go from there. Also, are you using a wideband O2? Or are you just going off of the claculation that DSMLink makes for you? If using DSMLink, do you have its individual settings set right? Then also you have to realize it is going off of data that also involves your MAS, which isn't telling the ECU the right info with all those boost leaks. Plus in the end the AF ratio function built into DSMLink is just an estimation, not something I would completely rely on. IE to get the backfiring and such you are now, you are probably going a lot lower than 11:1 like it said.

Hope this helps.

Thanks much for verifying my thought and troubleshooting process on this issue.

I'm going to fix all the leaks, <have a new 63 mm TB ordered to take care of the TB Shaft and Biss leeks, and then I'll need to buy and install new injector insulators and seals> THEN I can take this AWD A/T car to RS Racing PREPARED for some Dyno/Wideband time.

A//// Guy · 08-04-2005

I wouldnt order a TB, if it is leaking it is very minor, like Ecoli mentioned. Most Boost controlers have a bleed hole that will leak out more than the TB will adn its not a big deal.

If you care that much just order the TB shaft seals and a new BISS screw.

TheBlizzard · 08-05-2005

Have you checked your intercooler for leaks? Just because its brand new doesn't mean that a a weld didn't break open.

howslowcanyougo · 08-05-2005

Quote:

Originally Posted by CRAIG

Have you checked your intercooler for leaks? Just because its brand new doesn't mean that a a weld didn't break open.

I haven't heard any from that area, buy also haven't sprayed it with soapy water yet either? I'll try that as well, Thx.....

howslowcanyougo · 08-05-2005

Is there a cheaper Wideband system that lets you use the wideband O2 sensor as the cars front O2 sensor, or do you have to put in another hole into your O2 housing?
Is there a system that can dump the wideband A/F data off to the DSMLINK as well? What's the best value in onboard Wideband systems right now?

TiA