Leak Down Test Results

[No Crust Racing]

Hmm I was sure I'd seen people plumb catch cans back into the sump, maybe it was after an oil air seperator.

Oil is just shell helix HX7 10-40, might be too thin?

That's not going to account for air in the sump, would a blocked pcv cause that though?

[51NNA]

Yes it would be the catch can plumbed back to the sump with a breather on top, maybe try 10-60 or 15-60, a blocked or broken PCV might be the cause especially on turbo cars, at least its easy to check it!

Edited May 22, 2012 by 51NNA

[No Crust Racing]

How do I test it? It's just a one way valve isn't it? So apply vacuum to one side and see what happens?

[51NNA]

Take it out and try to blow into it, you shouldn't be able to, only suck.

Edited May 22, 2012 by 51NNA

[No Crust Racing]

OK on the valve cover pipe side I can blow through it and when I suck it seals, the opposite is true for the plenum side, suck through OK blow seals it up.

[No Crust Racing]

OK more info on this.

Replaced the leak down % gauge with a regular 0-150psi gauge.

Dialled in 20-40-60-80 and 100 psi inputs and no matter what input I put in, when connecting up to the spark plug hose BOTH gauges would always drop 5psi, as per usual the air can be felt leaving the dipstick.

This doesn't make sense to me, 5psi of 20 is a huge 25% drop but 5psi of 100 is obviously only 5%. Further to that, both gauges dropped down by the same amount, I'd have thought that the input pressure gauge should stay at the set pressure but how can that ever work if both gauges on the spark plug side of the regulator.

Of course the gauge is going to drop in pressure when connected as you've just opened up a larger volume of space for it to pressurise. Should both gauges be dropping like that?

[51NNA]

Just buy a compression tester, rip all the plugs out first, start at 1 and work you're way back, crank it over 3 or 4 times and write down the results. Should be around 140-160 if a cyl is leaking it will show.

[No Crust Racing]

I did that already, came up as 155-160 all pots

[STATUS]

i bought a few of the leak down testers off ebay and they all were faulty.... 3 in fact. It turns out they were calibrated for "small engines" and the seller in china just thought removing the sticker would make it suitable for your average motor car..

bought one locally from snap on and it works perfectly.

[51NNA]

Well im not sure, apart from a rebuild hows you're catch can setup?

[No Crust Racing]

Status I was thinking the same thing, low input pressures to set it implied it was for small engines, but I've replaced the leak down % gauge with another -150psi gauge so calibration is not an issue now.

A mechanic on another forum is telling me that on a good engine there should not be really notable air flow into the crankcase so that's enough info regardless of what the gauges say.

I'll have some more good data hopefully this evening when I can leak down test another mates rebuilt CA which makes good power so we know it's tight enough.

From there I can make a call, and it may just be turn down the boost a touch, run thicker oil and modify the catch setup to keep driving it.

As for the catch setup it's a standard exhaust cam into catch, catch into intake setup, no venting. (I have baffled it so it actually catches the oil...)

If I modify it I'll delete the PCV, pipe the intake into the catch also, plumb a drain into the catch back to the sump and vent the catch to atmo so the engine can breath back through it as needed.

I'm also considering one of these little guys to help sealing.

http://moroso.com/catalog/categorydisplay.asp?catcode=13023

[No Crust Racing]

My mate was a no show tonight, trying to line him or another mate with an SR20 up for Tuesday night.

[No Crust Racing]

OK more info.

Had my mate come over, and to correct a mistake I made earlier his SR only has fresh bearings, rings are 106ks.

We leak down tested his and then switched the second gauge on the tester and pumped 80psi into a cylinder, his came back with the same results mine had, about 20% on the leak down and notable air escaping from the dipstick/oil filler hole. Though I noticed his took a few seconds of pressuring at 80psi before the air escaping the dipstick etc was noticeable.

We warmed mine up and tested it again, same results as his. So I can only conclude that there is not enough solid data to pull it down.

On the catch can front, I've had an idea. As my can has an input into it from the exhaust side rocker and exits out into the intake like the factory setup, I'm wondering if the reason it's filling so quick is that the GT2560 on 17-18psi is generating enough vacuum in the intake pipe (where the catch can feeds back into) to draw more oil heavy vapours out of the rocker cover than it would with a factory turbo on stock boost.

I will test this by blocking that feed back into the intake and throwing it on the dyno with an empty catch.

[STATUS]

^^ just had a thought... did you remove the big black baffle box that connects the crankcase to the rocker cover vent? if so put it back.

[femno]

The water is probably leaking externally somewhere. CAs are notorious for headgasket water leaks.

[No Crust Racing]

^^ just had a thought... did you remove the big black baffle box that connects the crankcase to the rocker cover vent? if so put it back.

To be honest, I'm not sure what that is or where it would be on a CA, I don't recall seeing anything matching that description. The factory breather setup on a CA just goes from the exhaust rocker to the intake pipe in front of the turbo. Mine now has a baffled catch can between those points.

The water is probably leaking externally somewhere. CAs are notorious for headgasket water leaks.

I've had a solid look but that's not to say it isn't weeping onto the exhaust manifold and burning off or leaking down the back of the engine where it's impossible to see.

I had an oil leak at the back of the engine from the half moon seal and that's been fixed now so hopefully if it's leaking down the back I'll see it.

Any thoughts on my oil comments? turbo creating vacuum in the catch?

[No Crust Racing]

Ok update time and good news.

I think my theory about the turbo creating vacuum in the catch can might be on the money.

I disconnected the pipe from the catch to the intake pipe and went for a blast after emptying the catch. Came back with a clean catch this time.

So I'll get a filter for the exit of the catch can and block the intake port. Job done

[mico]

will that stop it using coolant tho ?

[No Crust Racing]

If it is using it, then of course it wont.

I'll be watching it very closely to see if the level is dropping and requiring top up.

I'll also lay something down underneath it to make it easier to spot leaks.

[MrStabby]

I think my theory about the turbo creating vacuum in the catch can might be on the money.

If that's the case, then maybe a there's a few kws to be had by improving the intake/filter. If the compressor sees a vacuum then it has to overcome that to get back to atmospheric pressure before it can make boost, so there'll be more heat in the compressed air and spool will be slower.