Is there a way to leak test the exhaust system?

[infinite_kaos]

I've done a blt all the way up to 25 psi fixed all leaks, and it bleeds off 1psi every 1-2 seconds and holds at 10psi for a while.

I'm trying to figure out why when I have my mbc set at 18psi it goes down to 10psi.

In 1st and second it goes to 20 psi and 3rd it only goes to 15 then down to 10. If I get off the throttle then back on it it will go up to 18psi then bleed off.

So I'm wondering if there is anyway to pressure test the exhaust for an exhaust leak either at the manifold or o2 housing or even downpipe.

I'm not sure if those areas would effect the turbo pressure or not, but I really can't figure what else it could be.

This is on a freshly rebuilt (by me) engine, compression is good as well.

I don't know if this sounds stupid or not, but I was thinking about putting my blt on my exhaust and pressurize it that way for leaks. Would that be dumb?

 

[jking29]

Seafoam the motor. If you have any exhaust leaks, they will most definitely show up.

 

[dylnwit]

Are you M/T or A/T? If your A/T with larger injectors and the stock turbo, you could just be running out of turbo. Generally, 3rd and above 'use' more air and fuel, which would explain why you can only build to 15psi, with it falling to 10psi. What's happening is your using the air faster than the turbo can pump it to give you that 20psi. Exhaust manifold leaks cause the car to be more sluggish in all gears normally, and wastegate issues would also be reflected in all the gears. Pull the heat shield from above the exhaust manifold (if you still have it) and wave your hand around close to the manifold when the car is running, normally, you can feel the warm exhaust coming out.

 

[Burnett03]

Seafoam will show visible leaks.

 

[DSMunknown]

http://www.dsmtuners.com/forums/newbie-forum/268323-smoke-test-exhaust-leaks.html

 

[PIMking]

well you could also have someone put their hand over the exhaust tip and then you can hear the links alot better.

 

[infinite_kaos]

Well I'm just gonna order a new exhaust gasket set, if that doesn't cure the problem, then ill do the boost leak test way.

 

[95blackGsTurbo]

First of all you shouldn't have your MBC set at 18lbs if you are on a stock setup, which your profile states. One of your issues is you are probably pulling massive timing trying to run 18-20psi and it is killing your boost. This is a very common problem. Although the 14b is good for 18psi and even 20psi in some instances, one stock injectors and a very lightly modded car I would turn it down. If you adjust it down to 15psi you shouldn't have any problem holding that amount. You are spiking to 20psi because of the lack of restriction in the exhaust so that is the reason for that problem. But not holding boost is most likely due to the car pulling timing from running to much boost on stock injectors.

 

[infinite_kaos]

ive tried it 15psi and get the same results. It always bleeds down to 10psi, unless of course I have it set lower. even with the vac line connected straight to the wg actuator (its shimmed) its still bleeds down to 10psi.

I ordered a complete turbo gasket kit from autozone should be in tomorrow. If that doesnt fix it then it has to be the turbo.

I dont think it was due to the high psi that it bled off like that, I have a Maf translator gen2 which is basically an afc, and adjusted it to where my o2 voltage was at .98 give or take, through out the rpm range. I dont hit fuel cut either.

Im getting Evo9 injectors tomorrow, getting rid of the translator and getting a 2g maf instead. As well as changing out all the gaskets, I think i should be able to figure this thing out, if not? well then youll see me back on here .

 

[infinite_kaos]

Ok I figured it out. It was an exhaust leak. I switched out the gaskets with new ones and it was better, but there was something still wrong. In between shifts it would take forever to build boost back up.

I then remembered my friend telling me that there needs to be a vent hole in my mbc otherwise the air that goes to the wg actuator has no where to go and leaves the flapper opened. So at work last night I drilledd a small hole in the back of my mbc, and what do you know, its like a completely different car.

Only thing I have to do now is readjust the mbc, with that hole in the back some of the air escapes and the actuator doesnt open till way later.

I haven't installed the evo injectors although I might do that today. Thansk for the help and advice guys.

 

[97gstnick]

Or if your cheap, you can run water into the engine and watch the vapor and droplets come out of your leak areas. Works for me. Just be careful to slowly ingest it.

 

[infinite_kaos]

That's gotta be the absolute worst idea, ingesting water into an engine is just wrong.

 

[the_mork]

Actually it is just fine in small amounts and extremely beneficial when done right (water injection).