Peugeot XN1 compression test figures

Doush_504

Doush_504

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G'day everyone

Would anyone happen to know any official compression test results for the XN1 engine ?
I know that there are lots of cyl. heads' part numbers with different compression ratios like shown here.
There is a photo of mine (square port), attached, if it makes any difference.

Thank you in advance :)


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IMG_20210401_134759_GC6.1_GMM29h2-646_day - Copy.jpg
 
Have you done a compression test on yours (prior to disassembly) ?
 
Reasonable, could be better but probably not worth worrying about too much. Engine warm and throttle wide open?
 
GRAHAM WALLIS said:
Reasonable, could be better but probably not worth worrying about too much. Engine warm and throttle wide open?
Click to expand...
Engine was relatively warm, but I did not touch the throttle.
Someone just held the compression gauge while I cranked the engine till the reading kept still.
Is it wise for it to be warm in the 1st place ?
I always prefer to replace the spark plugs with the engine rather cold in order to avoid any damage to the aluminum thread.
 
Last edited:
Compression tests are always meant to be done hot & wide open throttle. Throttle closed doesn't give a reliable or accurate result.
 
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Hi Doush_504.

I am not familiar with your specific engine, but my comments are:
  • They were all taken under similar conditions.
  • At 140 PSI they are all even which is important.
  • I would have expected for an engine in good condition the cranking test pressure to be slightly higher.
  • Wide Open Throttle might result in pressures up to 10% higher, (that's a guess). PS: Using a small wooden chock between the idle stop and the throttle linkage, to move the throttle away from the closed idle position is all that is necessary.
As others have noted, it would have been useful to have known the before and after compression test results.
 
Engine warm, ignition cable from coil disconnected, throttle wide open (gas pedal to the floor), six cranks of the engine. Typical numbers are 170 to 180 psi, many around 200 psi after a rebuild with a light head skim . My guess is that your 140 psi will climb to 170 psi or even more with WOT. You cannot introduce a lot of air in the cylinders unless the throttle is wide open, so even if the engine is in perfect condition your numbers will be low. You need air to generate air pressure.
 
Is it safe/normal to remove the spark plugs from a hot aluminum cylinder head?

RINGER said:
Compression tests are always meant to be done hot & wide open throttle. Throttle closed doesn't give a reliable or accurate result.
Click to expand...
 
Thanks Thanos for your advice
Always appreciated.

To be honest, the test was done in a bit of a hurry, so I reckon numbers could get better.
I did not know about the throttle thing; but wouldn't that cause flooding ? since the fuel pump is mechanical & would keep delivering fuel to the carb ?

ThanosK said:
Engine warm, ignition cable from coil disconnected, throttle wide open (gas pedal to the floor), six cranks of the engine. Typical numbers are 170 to 180 psi, many around 200 psi after a rebuild with a light head skim . My guess is that your 140 psi will climb to 170 psi or even more with WOT. You cannot introduce a lot of air in the cylinders unless the throttle is wide open, so even if the engine is in perfect condition your numbers will be low. You need air to generate air pressure.
Click to expand...
 
Doush_504 said:
Thanks Thanos for your advice
Always appreciated.

To be honest, the test was done in a bit of a hurry, so I reckon numbers could get better.
I did not know about the throttle thing; but wouldn't that cause flooding ? since the fuel pump is mechanical & would keep delivering fuel to the carb ?
Click to expand...
Hard to flood a cylinder when the spark plugs are not there :)
 
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