930 - Pressure Testing

[henrymfisher]

Hey guys,

So I just got my fresh 3.0 motor running last week. Lots of very sweet new goodies inside and outside (993 super sport cams, tial 1.0 wastegate, Garrett GT30R turbo, Rarlyl8 headers and tailpipe) . So I always wanted to pressure test my system so I made a pressure tester and hooked it up last night. I found a few interesting things.

1. My Aux Air Regulator was leaking like a sieve next to the electrical connector. Luckily I had a spare AAR that is pressure tight.

2. I hear a small amount of air leaking a little further back in the motor but so far cannot find it. Will investigate to see if it is where my C2 IC connects to the TB, or maybe the cold start valve.

It is losing about 1 pound every 2-3 seconds.

Questions:

1. Why is the AAR leaking? Can the seals/gaskets be replaced (drilling out the rivets)
2. I know this is a setup question, but what amount of leaking boost is "normal"? Can you expect to have a system that is close to 100% leak free? Or is it like a cylinder leak down where anything less than 3% is great?

I have all new rubber sleeves, nice T clamps (threaded type).

Thanks for your insight.

Henry
'76 930

[turbobrat930]

? for ya... Why not just deleate your AAR valve? You have a idle adjustment on the Throttle body.. I deleated mine when I had my old CIS system, and never missed it....

[henrymfisher]

That is on the table. My car also has the old style manual throttle adjustment next to the heater controls.

I kind of didn't want the wires to the AAR tied off, but it is a consideration.

Thanks,
Henry

[T77911S]

Originally Posted by turbobrat930

? for ya... Why not just deleate your AAR valve? You have a idle adjustment on the Throttle body.. I deleated mine when I had my old CIS system, and never missed it....

i took mine off for a few months, and even though it does not get that cold here, i did not like it and put it back on.

i am interested in your results. boost leaks can also = vacuum leaks, which i have been dealing with.
how did you seal it up? did you losen all the intake rockers to close all the valves?
if not, sounds like you are doing a leakdown test on the entire engine at one time.
if so, you may be hearing air leaking past the rings and coming out of the engine case vent at the rear.

[henrymfisher]

Here is a step by step post that I read on how to pressure test the turbo system.
Obviously air will escape past open valves. What is clear and audibly easy to hear are leaks coming from places where the turbo system flows externally. IC to TB, Up piping from turbo to IC, IC through the Aux Air Reg, and intake manifold leaks. They suggest spraying soapy water to see where the bubbles originate. I had no idea that a AAR could really leak air. I thought the hose connections would be suspicious but never the electrical connector (air was whistling by it). I watched the pressure gauge go from 12-13 psi to 0 very quickly.

HOW TO BOOST LEAK TEST 101 by turboboostleaktesters.com

Here is a picture of the device I made. Super easy. I connected it to the steel inlet pipe after the C2 pop off rubber elbow. Much easier than disconnecting the rubber sleeve on the inlet side of the turbo.

[voitureltd]

I use a smoker. low psi with visual shows every little leak.

[356911930]

I am interested in your results too. Please post power imrovements when you get them.

Thanks,

Rahl