Engine compression

[Xti]

As I know a 155 Q4 engine compression should be at 8:1, isn't it?

Before starting the rebuilding project I have done also a compression test to my Q4's engine and I must say I'm a bit worried (11.2/ 10.7/ 11/ 11.1 if I'm correct). Please look the picture above.

Am I right to be worried? At least there are no big differences between cylinders...:confused:

What would be the most dangerous consequences of a higher engine compression considering to a OEM engine with no upgrades? Thanks a lot guys.

Cheers,
Cristian.

[Gery83]

The nominal compression ratio (8:1) is not the same as the measured.
The measured end-compression is in bars.
You don't have to worry, it's not too high. :biggrin:

[MaxiBoost]

@Xti ,
Q4 compression ratio is 8:1 (RATIO)

your test not ratio ,
your test is compression value in cylinder ,
test value 10-12 bar is good for q4

[Xti]

:doh: It seems like I've mixed terms, thank you both.
I have calmed down a bit now.

I thought that the engine cuts after 4000rpm occured due to "a higher compression"...

Need to read more but I'm willing to learn.

[Juan AR155Q4]

I thought that the engine cuts after 4000rpm occured due to "a higher compression"...


Check phase sensor, cause if disconnected or out of range, it takes the ecu to safe mode cutting @4000

[Xti]

Check phase sensor, cause if disconnected or out of range, it takes the ecu to safe mode cutting @4000

It's good to know so I'll keep that in mind when reassembling, thank you Juan.

Everyday I realize how much I can find from this special forum, from nice and cool guys experiences. Sharing is always very much appreciated.

Cheers,
Cristian.