Technical 1.6 multijet 88kw engine compression

[tomicdd]

Hi guys,
Does anyone know what would be factory engine compression for 1.6 multijet 88kw 2008.y engine (in bar pls )
I did engine rebuild but I can't find anywhere those data. There is engine compression ratio which is 16.5:1 but that's a different story.
I need a pressure reading in cilindar.
What compression is considered as good before classifying engine for overhauling?
Thanks

 

[bugsymike]

Hi guys,
Does anyone know what would be factory engine compression for 1.6 multijet 88kw 2008.y engine (in bar pls )
I did engine rebuild but I can't find anywhere those data. There is engine compression ratio which is 16.5:1 but that's a different story.
I need a pressure reading in cilindar.
What compression is considered as good before classifying engine for overhauling?
Thanks

Seems hard to find the readings in my old trade books , the only thing I could find was old lorries with 16:1 stating a minimum of 300psi which if you divide by BAR @ 14.7psi(pounds per square inch) to one Bar gives around 20.4 Bar, the other one I had was for a lorry with 22:1 compression ratio stating a minimum of 400psi which would give a BAR reading of 27.2 BAR by my calculations.
Generally any white smoke on cold starting on a diesel engine was a guide to low compression due to unburnt fuel.
Just a rough guide if any help, the newer trade manuals don't seem to give any readings for engine compressions, probably because now days most mechanics wouldn't know where to start with engine total overhauls unlike when I trained over 50 years ago when every workshop rebuilt engines, gearboxes and rear axles and often had their own machine shops too. Mind you then you had engineers, mechanics and at the bottom fitters, where as now they are all called "technicians"?

 

[tomicdd]

Seems hard to find the readings in my old trade books , the only thing I could find was old lorries with 16:1 stating a minimum of 300psi which if you divide by BAR @ 14.7psi(pounds per square inch) to one Bar gives around 20.4 Bar, the other one I had was for a lorry with 22:1 compression ratio stating a minimum of 400psi which would give a BAR reading of 27.2 BAR by my calculations.
Generally any white smoke on cold starting on a diesel engine was a guide to low compression due to unburnt fuel.
Just a rough guide if any help, the newer trade manuals don't seem to give any readings for engine compressions, probably because now days most mechanics wouldn't know where to start with engine total overhauls unlike when I trained over 50 years ago when every workshop rebuilt engines, gearboxes and rear axles and often had their own machine shops too. Mind you then you had engineers, mechanics and at the bottom fitters, where as now they are all called "technicians"?

Many thanks for fast respond.
So, most likely I should expect not less than 20bar to be considered as minimum cylinder compression. Not a single word about factory compression/new engine for 16:1 ratio?
I've found this thread for 1.6 tdi

Cylinder Compression Specs for CBAA

Anyone know Cylinder Compression Specs for CBAA?? Hi all - need some help. Can someone with access to the right tech manual please post compression specs for the CBAA engine? I know nominal 16.5:1. (Edit) Please fill in: New Engine - high limit New Engine - low limit Difference between...

forums.tdiclub.com

And they are talking around 30bar range for the new engine and 19bar for rebuild limit. I suppose mjtd should be close?

 

[bugsymike]

So ideally 20 Bar as a minimum with a 16:1 ratio roughly.

 

[tomicdd]

Update,
I did compression test and it is 21 bar on all 4 cylinders when it is cold. I think that they did something wrong during rebuild of the engine...

 

[bugsymike]

Update,
I did compression test and it is 21 bar on all 4 cylinders when it is cold. I think that they did something wrong during rebuild of the engine...

The readings are all even which is good and modern engines get their power from higher revs generally and also higher turbo boost pressures which may compensate.
What was the reason for the enquiry in the first place, do you have a specific problem?
If you suspect the engine rebuild, it is possible to do a "leak test" (not a "leak off" test) this involves testing with compressed air which can show were compression pressure may have been lost.
Was it a full engine rebuild involving cylinder rebore and new pistons etc? If so has it been run long enough to bed in piston rings to the cylinder bores etc.?

 

[tomicdd]

Hi Mike,
It was full rebuild - cylinder head fuly rebuilt, cylinder sleeves, new piston rings but sadly old, but, good, pistons. It was impossible to find new ones, anywhere in the world. Rebuild lasted for an year ant they have had 3 times removed engine from engine bay, due to lack of compression - it was around 18 bar. Right now I have following problems - high fuel consumption, a lot of oil in air intake system - it comes from pipe which goes after oil separator to air intake before turbo, dpf is clogging very fast - regenerates every 60 km , doe diff pressure is fine - 4mbar at idle and around 90 mbar at 4000 rpm.
Before rebuild compression was 18,18,16,20 bar and that's why I was suspecting that something is wrong. So far I run around 4000 km after overhaul and everything is worse than before rebuild.
I had a conversation with one fiat official dealer garage and they said that factory compression should be 25-31 bar.
It looks like the same as 1.6 tdi which I have found so far but not a single data for multijet.

 

[bugsymike]

Hi Mike,
It was full rebuild - cylinder head fuly rebuilt, cylinder sleeves, new piston rings but sadly old, but, good, pistons. It was impossible to find new ones, anywhere in the world. Rebuild lasted for an year ant they have had 3 times removed engine from engine bay, due to lack of compression - it was around 18 bar. Right now I have following problems - high fuel consumption, a lot of oil in air intake system - it comes from pipe which goes after oil separator to air intake before turbo, dpf is clogging very fast - regenerates every 60 km , doe diff pressure is fine - 4mbar at idle and around 90 mbar at 4000 rpm.
Before rebuild compression was 18,18,16,20 bar and that's why I was suspecting that something is wrong. So far I run around 4000 km after overhaul and everything is worse than before rebuild.
I had a conversation with one fiat official dealer garage and they said that factory compression should be 25-31 bar.
It looks like the same as 1.6 tdi which I have found so far but not a single data for multijet.

Cylinder sleeves? I thought it was a cast iron engine, do you mean they fitted dry liners?
If I was rebuilding an engine with old pistons but new rings I always lightly honed the bores, this allowed the new piston rings to seal better as they bed in. I also always measured every piston ring gap with a feeler gauge with rings in the cylinder bore before fitting them to the pistons.
If I had suspicions regarding the engine rebuild I would do a "leak test" as I mentioned earlier, this would tell you where the loss of compression was from. What you describe makes me suspect the piston /bore seal, i.e. piston blow by. (leaking power down the sides of the pistons) in which case it needs a proper engine rebuild.
The 21Bar (300psi approx ) is not good for an engine after an expensive rebuild and run in (bedded in) for 4000 km.

 

[tomicdd]

Yes, new sleeves because they have tried with +0.4mm 1st special and 0.4mm new pistons but after failure they have fitted new standard size cylinder sleeves. Thay did hon all cylinders doe. I didn't pay anything so far that's why I am doing this research so I have a proper data to rise a complain about rebuild. So, next step is compression leak test and then we'll know what's going on... Strange and frustrating. I'd like to find factory compression values as a crucial pruf that they have had rebuild bad...

 

[bugsymike]

Yes, new sleeves because they have tried with +0.4mm 1st special and 0.4mm new pistons but after failure they have fitted new standard size cylinder sleeves. Thay did hon all cylinders doe. I didn't pay anything so far that's why I am doing this research so I have a proper data to rise a complain about rebuild. So, next step is compression leak test and then we'll know what's going on... Strange and frustrating. I'd like to find factory compression values as a crucial pruf that they have had rebuild bad...

If a proper "leak test" is done it will show the % of loss via pistons, valves etc.
If the Fiat Dealership can put in writing what the recommended compression readings are, then you can show that to the engine builder.

 

[tomicdd]

Hi Mike, small update... I've got info from garage which was doing leak test and they said that air is leaking via pistons.
They couldn't tell me which percentage doe...

 

[bugsymike]

Hi Mike, small update... I've got info from garage which was doing leak test and they said that air is leaking via pistons.
They couldn't tell me which percentage doe...

% is important, as is difference across pistons/cylinders.
There will always be a certain amount of loss past pistons when compared with valves etc. However poor piston/cylinder seal does point towards the issue you originally were concerned with. Oil/fuel consumption, oil blowing into air intake from engine breather etc.
I would suspect either piston size doesn't match bore, poor boring/liners etc, or broken piston rings on fitting.

 

[tomicdd]

Thanks for fast reply.... Bad luck for my car, I would say...

 

[tomicdd]

Hi Mike, I've got video recording from leakdown test an I did ss of readings - 80% all cylinders. It's single gouge device and i don't know if input pressure was as supposed to be. I guess if input pressure is lower than it should be, air blowout might show high?
With this readings engine shouldn't be able to start at all? And yet I have 21bar compression and no issue with engine start...

 

[bugsymike]

Hi Mike, I've got video recording from leakdown test an I did ss of readings - 80% all cylinders. It's single gouge device and i don't know if input pressure was as supposed to be. I guess if input pressure is lower than it should be, air blowout might show high?
With this readings engine shouldn't be able to start at all? And yet I have 21bar compression and no issue with engine start...

The equipment I was first introduced to was a Sun Tuning Diagnostic Leak Down Tester on petrol engines and later I bought a Bosch machine for diesel engines, both worked well in locating where a loss was happening.
I have also found a basic test can be accurate without the gauge reading etc. simply a high pressure air line 90-150 psi (10Bar? I always used 150 psi) using a suitable air tight adaptor to fit the heater plug or injector thread in cylinder head, and then locking the engine from turning once TDC has been reached on the firing stroke of that cylinder, as if engine turns a small amount the valves start to open and the result is wrong.
Your 80% reading actually indicates a 20% loss on each of those cylinders tested. I believe the idea was if it reached 25% then attention was required on a worn engine. In your case with a reconditioned engine the loss figure should be much less than you report especially if it the loss is all past your pistons which would indicate a poor seal between cylinders and pistons, which you are seeing as high fuel and oil consumption, oil in air intake etc.
I am not saying you don't have a problem with DPF Regens etc. However it is necessary to start with a good efficient engine before correcting faults on things bolted onto the engine.
Regarding compression readings for a good engine I would agree with the 31Bar your local Fiat Dealer mentioned as a good reading.
In simple terms if you look at your engine as a bicycle tyre pump with the rubber seal gone faulty, it may blow up the tyre but you have to work twice as hard to do the job.