Compression test results

[Smosh]

Home tested compression mine not long back for comparison, these are my results.
Front left: 160psi 11 bar
Read left: 180psi 12.2 bar
Rear right: 175psi 12 bar
Front right: 150psi 10.5bar
Similarly a vw supplied replacement engine, probably done 50k. I cant tell you what is good or bad though...

[itchyfeet]

my DG is higher than that, don't have the figures on me but can post later.

these were tested a few weeks ago

10 turns of the engine. (working temp)
#1... 12bar
#2... 11 bar
#3... 11.5 bar
#4... 11.5 bar

heads were last off and valves ground 3 years ago, it's done only 9k since tuen
Engine was reconditioed in 2002 and has around 85k on it.

Just after the heads were done 3 years ago I got readings of

10 turns of the engine. (working temp)
#1... 12.25 bar
#2... 11.75 bar
#3... 11.75 bar
#4... 12.25 bar

[itchyfeet]

Home tested compression mine not long back for comparison, these are my results.
Front left: 160psi 11 bar
Read left: 180psi 12.2 bar
Rear right: 175psi 12 bar
Front right: 150psi 10.5bar
Similarly a vw supplied replacement engine, probably done 50k. I cant tell you what is good or bad though...

Thats a DG right?
DJ has higher compression ratio so important to state engine.

[sarran1955]

Hello,

My 2 pence worth..

redo the test, then put a good squirt of engine oil.(your choice).. into each cylinder before re testing..

If there is no real difference then the valves may need attention..

if there is a big difference, then its time to look at the piston rings..

However.. the important thing is the balance between cylinders.. and I would say you don't have much to worry about...

If you start to get a mis fire on overrun, and you know your exhaust is good.. then think about dropping the motor.and sorting the heads..

Regarding 'lean running' on GPL.. we use at work several fork lift trucks.. all gas. all the Komatsus are fitted with an oiling device to overcome
the 'dry fuel' problems..seem to run better than the Nissans.

Maybe prepare a pair of heads in advance as an investment/precaution..

Cordialement,

[kevtherev]

Thank you sarran your advice is always appreciated.

[kevtherev]

I notice you used 10 turns itchy feet.
The readings are higher with ten.
What is the norm?

[itchyfeet]

I notice you used 10 turns itchy feet.
The readings are higher with ten.
What is the norm?

Dunno if there is a norm I think 10 is a nice round easy number to remember, it's what I use each time so my readings are consistent , as Sarran says the general rule of thumb is difference between cylinders rather than actual value. I have never had the luxury to watch the gauge while cranking, I assumed it got up there pretty quick but perhaps not.
Speed of cranking i.e battery & starter and connections condition may affect readings too. I always have all plugs out.

I must say when I first got the van with 50K miles befotre heads were changed( same rings)the readings were considerable lower, at 9.5, 9.5, 10, 8.5 indicating that valves are more likely the cause of low pressures but I have changed starter and battery too since then!!!

The old oil in the bore trick is good for vertical cyliners but not sure if it works with flat engines so well, I'd have thought oil spash onto valves may help them seal too so may not prove what's worn.

[Smosh]

Home tested compression mine not long back for comparison, these are my results.
Front left: 160psi 11 bar
Read left: 180psi 12.2 bar
Rear right: 175psi 12 bar
Front right: 150psi 10.5bar
Similarly a vw supplied replacement engine, probably done 50k. I cant tell you what is good or bad though...

Thats a DG right?
DJ has higher compression ratio so important to state engine.

Sorry! Ignore me!

[itchyfeet]

Home tested compression mine not long back for comparison, these are my results.
Front left: 160psi 11 bar
Read left: 180psi 12.2 bar
Rear right: 175psi 12 bar
Front right: 150psi 10.5bar
Similarly a vw supplied replacement engine, probably done 50k. I cant tell you what is good or bad though...

Thats a DG right?
DJ has higher compression ratio so important to state engine.

Sorry! Ignore me!

Not at all, it's relevant just need to state engine.

[ELVIS]

Just did my DJ on saturday before i pulled it out.

192/192/186/195

not bad against Bentley values of 145 to 195

[kevtherev]

Just did my DJ on saturday before i pulled it out.

192/192/186/195

not bad against Bentley values of 145 to 195

Just twist the knife a bit mate!

So I guessing that a good high compression ensures a clean efficient burn.
Ergo developing more power than a lower cylinder compression.

[silverbullet]

Indeed. Less piston ring blow-by makes your oil last longer too.
At the risk of blowing my own cornet...the MV I built for Aidan ended up in a Westy Cali syncro and it was a positively perky performer. And that is a 9:1 engine.

Sent from my Atari 7800

[kevtherev]

Got me thinking now.
When I fitted the engine I was initially surprised at the added performance against a DG, but against a similar DJ set up (shepsters) I was just a little short on acceleration.
The engine was from a syncro, the syncro was used as a car-a-van tug, never saw the road much, so presumably never saw a service like its predecessor perhaps?
Its not a dead engine it just needs rebuilding.
I might take it out myself and post it to some clever fella who can do that at some point in the future.

[bigherb]

As you have got lower compressions, if the timing has been retarded for 95 unleaded you can reset it to 10 deg might pep it up a bit.

[kevtherev]

Thanks Bigherb, timing is set at 10 deg.