2G Boost leak test

[regulator213]

i attempted a boost leak test today and i could only get the system pressure up to like 7psi. Plus when i took the air hose off all pressure dropped within a minute. There are no huge boost leaks anywhere and the car builds 30lbs of boost no problem. Did i do the boost leak test wrong?

The other thing is the car is cam'd. At idle the vacuum is between like 10 inHg and 13 inHg. Will the cams cause it to have low vacuum?

 

[RadDsm]

Yes cams can cause lower vacuum.

Here are a couple links that will help you with the BLT
http://www.dsmtuners.com/forums/art...-boost-leak-test-how-boostpro-net-tester.html
IC Pipe Tester
2G Turbo DSM Boost Leaks -How to test and fix

 

[pboglio]

I've been recommending to people to physically rotate the motor at the crank damper pulley so that the intake and exhaust valves will be closed during the boost leak test. On my HKS 264 cams, I have maybe a 5-10* window to keep everything sealed. On more aggressive cams, I could see a static boost leak test being alot more difficult.

 

[My1GLaser]

Yeah I do the same thing as him ^^^ with my 272s. Here is a pic of my tester. I find it easier to track down leaks when the airline stays attached and keeps the system up to my test pressure. Then I can just shut the ball valve and time how long it holds the pressure. I made the other one with the tire valve, but it was such a PITA to hold the hose on there and track down leaks.

Pressure could be leaking thru your PCV valve. Do you have your MBC line plugged? The bleeder hole lets out pressure during a test. Are you using a decent sized air compressor? Some real small ones can't get the pressure up high enough to compensate for leaks.

 

[Rob10_99]

Remember kids, 30psi for checking leaks, not the 140psi line pressure!

 

[regulator213]

Remember kids, 30psi for checking leaks, not the 140psi line pressure!

it was a shop that i was at on the base im stationed at. And im told that the line pressure is like 150 psi and i still couldnt get it past 7 psi. Although that is good thinking about the MBC. didnt think about that. And i thought the throttle plate should hold most of the pressure. I was testing a car with 272's in it. at least higher than 7 psi.

my1glaser i like your idea about the on/off valve instead of a tire stem. Did you use a metal end cap to screw the valve in to? Where did you get the ball valve from?

 

[My1GLaser]

my1glaser i like your idea about the on/off valve instead of a tire stem. Did you use a metal end cap to screw the valve in to? Where did you get the ball valve from?

I used a PCV end cap, drilled a hole and used a 1/4" pipe tap (IIRC) for the ball valve and threaded in the air fitting. I got it at Lowes in the air tool section for about $8. I test to 30 psi and its held fine for 2 years. I would recommend t-bolt clamps at that pressure, since I have heard of testers shooting off the turbo with regular worm gear clamps.

 

[regulator213]

sounds good man, thanks for the info. Did you use any thread sealer or plumbers tape or anything on the valve end in the end cap?

 

[My1GLaser]

I just went out and checked and I JB welded it.

 

[regulator213]

awesome. thanks again man.

 

[steve]

And i thought the throttle plate should hold most of the pressure.

If the throttle plate sealed the intake the car would never idle because no air would reach the cylinders.

To pressure test you have to turn the crank to make sure that no cylinder has it's valves in overlap (both intake and exhaust open) or the system will never pressurize.

 

[darkhorizon]

I have seen turbo compressor covers leak fairly significantly before.

 

[9!'clipseDOHC]

If the throttle plate sealed the intake the car would never idle because no air would reach the cylinders.

To pressure test you have to turn the crank to make sure that no cylinder has it's valves in overlap (both intake and exhaust open) or the system will never pressurize.

Where should the crank be to keep the valves closed? I'm having trouble due to this.

 

[GSXeclipsePSI]

Where should the crank be to keep the valves closed? I'm having trouble due to this.

+1 one on this cause I need to boost leak test bad. I'm pulling 50lbs/min of air and only making 344hp and I need to know where also. I have 272s also

 

[9!'clipseDOHC]

I've got stock cams. Say the timing mark on the crank pulley is the hour hand. Where on the clock would be the proper point to have all the valves closed?

 

[92DSMErdrick]

Put your cams up at TDC first, rotate them 6 teeth marks, all valves should be closed. Remember one will be on the actual tooth and the other came gear the mark will be between the teeth.

 

[blade970]

How do you find TDC?

 

[9!'clipseDOHC]

Rotate clockwise? Also 6 full teeth (if that makes sense)?

How do you find TDC?

TDC is when the #1 cylinder (driver's side) is at the very top. Pull out the spark plug and insert and long screwdriver or similar device and rotate your crank clockwise by hand until it is all the way at the top, just before the piston starts to drop. That is top dead center (TDC).

 

[92DSMErdrick]

Well truthfully it doesn't have to be at TDC. As long as you start with the cam gears aligned. Yes it is 6 full teeth. count 6 teeth from the marks on the cam gears in the direction that they will turn