xpuser8334

Active Member

• Feb 13, 2018

• #1

Guys...
Does anyone know what the healthy compression test reading should be on the M47R engine.
I'm pushing 171 - 171 - 171 - 170 @ no.4
Searching the internet doesn't bring up any decent PSI or BAR reading any where!
Cheers

 

Nodge68

Well-Known Member

• Feb 13, 2018

• #2

It's pretty simple to work out the compression pressure so you'll get a rough idea of what to expect.

Just take the compression ratio and multiply by atmospheric pressure of 14.7 PSI.

You're average turbo diesel is around 18 to 1 CR. So 18 X 14.7 = 264.6. So that's the sort of pressure you'll be expecting.

Edit:

The TD4 CR is 18.1 + or - 0.5 to 1.

So you should see compression pressures of between 259 and 273 Psi.

There will be some variance due to wear, which should be under 10% or so.

 

Last edited: Feb 13, 2018

xpuser8334

Active Member

• Feb 13, 2018

• #3

OH :-( that means I need to do a wet test too.. but I will double check my readings tomorrow to be sure.
Thanks Nodge68

 

xpuser8334

Active Member

• Feb 14, 2018

• #4

Ok... I must have been drinking of something.... re-did the Compressions - shame I couldn't type them up properly in the first instance...
271 (well just under - maybe 270.5 or .6) On 1,2 and 3 - 4 is at 269 almost touching 270.
So if this is right... I've got excellent compression on this 89,000 mile engine.... not even going to do a wet test....
Thanks @Nodge68

 

Nodge68

Well-Known Member

• Feb 14, 2018

• #5

You're well within spec, so nothing to worry about there.

 

xpuser8334

Active Member

• Feb 14, 2018

• #6

for Info... The engine bay was smeared in oil.. turbo has gone, but the crank case breather wasnt modded and blocked solid - so no power..
was hopping for good compression, before I stripped the injectors out, took the top off and inspected the cam / chain etc. then fitted another low mileage turbo.
Anyway @Nodge68 do I bump into you on any of the facebook groups at all?