Leakdown testing, ring suggestions?

[NickB]

What pressure do you usually start a leakdown test at, and how long do you let it sit before taking the second reading?

I put pressure to the cylinders on my chrysler 2.2 turbo last night to see where i'm losing compression. Nothing came out the intake or exhaust valves, there was a small breeze out the oil filler cap though. I had the head off the motor about 3 months ago, and the bores looked perfect. They were bored/honed in october, new pistons/rings installed. Has about 20,000 miles on it right now. I know i'm looking at putting rings in it, but i'd like to do a proper leakdown to test to see just how bad things really are. Plugs all have a full ring of colour on the base, and the insulators are a very light orange. EGT's are typically around 1350 while cruising, 1450-1500 under high boost. Nothing appears to be broken, just worn rings.

The rings in there right now are Hastings Moly rings. Any suggestios for the next set? These ones didn't impress me.

 

[MaxRaceSoftware]

Hastings has a pretty good oil ring design , but from past experiences , the compresion rings aren't the best .

i like SpeedPro Plasma Moly rings with their Oil Ring design
there might be newer better ring designs now , so maybe ask around ??

a LeakDown test will quickly spot valves leaking
and give you a general idea of ring seal, but the best way to tell ring sealing , is to measure BlowBy CFM on dyno under full-load acceleration test


some of the SS Chevys and Chrysler SS Hemi with Dykes top rings might show you pretty much leakage on a static leakdown test , but once the engine is running under full-throttle , full-load the CFM leakage is 2 to 4 CFM
even though it looked pretty bad on a static leakdown test

you can sometimes be fooled by the static leakdown test
especially if you have a lot of piston-to-wall clearance,
type of top ring, piston alloy material, to name a few

what really counts is what the engine's BlowBy CFM is under full-load

other possible sites of BlowBy might actually be from leaking headgaskets into lifter area ...this too will showup as BlowBy CFM , but it won't be coming from rings


Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

Support Israel - Genesis 12:3

 

[NickB]

I remember you talking about blowby CFM on the dyno. I don't have any way to measure this though, or i would have tried it already

I borrowed a MAC leakdown tester from a friend at the local chrysler dealer, and it came out at 10,4,3,8% across the motor.

It's a SOHC engine, there's no lifter area.

Nothing came out the intake, exhaust, or the cooling system.

I did do a little more playing with the tuning tonight, i'll post tomorrow about the results after my drive to work.

 

[comnean]

Hy,
First I suggest to make a simple compression test:
1. Pull out all spark plugs
2. Temp. of oil arround 40 C
3. Pull out the main fuel pump relay
4. With appropiate compression gauge check pressure on each cylinder with throttle open at maximum untill the measured pressure are stabilised
5. Readings must be not more 0,5Bar different betveen cylinders and in neighborhood of values prescribed by manufacturer
6. In aim to determine if rings or valves are leaky you put a mixture- 50ml. (70% motor oil and 30 % fuel)in each cylinder just before compression checking. If pressure drop up significant -1-1,5 bar.(compared with first measurement)is a ring problem. If measured pressure is similar with that first measured is a valve problem (not tightening of valve, oil leaks on valves guides or valve sealant rings).
Sorry for my bad english.

 

[MaxRaceSoftware]

Nick , the 0 -to- 10 CFM BlowBy Meter is available from
Dwyer Instruments

its about a Foot long , pretty good quality piece

i forgot to mention that you don't really need the dyno
some of my customers hook one up and just go againt the
converter with TransBrake to load engine and take a reading

but with a Manual Trans, it would be dangerous
because you would have to glance at Meter during a run
but its been done at the track .

Or you could do something like what Comnean posted
in combination of leakdown test .

i'd look for 7 (min.) to 10 pulses of needle movement , then note reading , but you would have had something to compare it to previously because its not OEM stock anymore
..maybe next time check when fresh as referrence point
to compare against
Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

Support Israel - Genesis 12:3