Differences between engines. Concern or not?

[Deleted User YDKXO]

I'm looking at a technical report on various tests carried out by a Cat dealer on two Cat 3196 engines in the same boat. These tests were carried out during a seatrial and there is very little difference between most of the parameters measured except in one area. At max rpm, the port engine appears to be consuming about 10% less fuel in terms of litres/hour than the starboard engine. In addition, the measured fuel pressure in the port engine is abour 10% higher than starboard and, similarly, the turbo boost pressure is 5% higher. The measured rpm of both engines at max speed were virtually identical.
Is this variation acceptable or should I be concerned? Could the variation be caused by differences between the props?

 

[Nick_H]

I can't help on the technical issue i'm afraid, but when do we get to find out what tub of plastic they're fitted in, given that this was a sea trial?

 

[gjgm]

How is the LPH being measured? Given the way a fuel curve looks, I'd guess at anything less than max revs, you wouldnt even spot a difference. I think my first question would be the accuracy of the measurements...maybe they are 100pct true, but if each engine LPH is calibrated, I guess it wouldnt be hard to end up with two readings ?

 

[Deleted User YDKXO]

I can't help on the technical issue i'm afraid, but when do we get to find out what tub of plastic they're fitted in, given that this was a sea trial?

They're in a Ferretti 53 I'm thinking about p/xing my 46 for. Money is agreed in principle and we're at the checking out each others' boats stage. I haven't done a sea trial yet. The figures come from an engine survey carried out last year and which the broker has given me

 

[Adrianwool]

Unlikely to be the props or they would not 'pull' the same engine rpm. Whats the accuracy range of the test equipment (i.e. it experimental error range). Were engine revs measured with seperate equipment (other than that shown at the helm station)?. You would need to factor these figures in to ascertain the true difference in the measurements obtained. I would expect some minor differences between two different engines in any case, and by the time you factor these in you may find it is nothing to worry about.

 

[Deleted User YDKXO]

How is the LPH being measured? Given the way a fuel curve looks, I'd guess at anything less than max revs, you wouldnt even spot a difference. I think my first question would be the accuracy of the measurements...maybe they are 100pct true, but if each engine LPH is calibrated, I guess it wouldnt be hard to end up with two readings ?

The report was done by a Cat dealer in Italy. I guess they all have standard issue Cat diagnostic equipment. Yes, the differences I describe are across a range of test results between 2100 and 2300rpm so there is a consistent difference between the 2 engines. More than that I can't say at the moment because the report wasn't done for me but the existing owner and I've been given a copy by the broker

 

[aquapower]

The fuel burnt info is measured and stored on the ecm, this is how some users work out what needs servicing, i have tested several pairs of engines over the last couple of years as the owners have been concerned about the differences in fuel used and for some reason it has usually been the star engine to use more, i have tested using measured cans of fuel as well as using electronic information and the two never match, there is often a difference but the manufactuters have never given an answer and have asured us its nothing to worry about as its within the limits, however I have not investigated this problem on cat engines, I will make sure next time I trial a boat with 3196 cats to check the readouts.

 

[splosh]

For piece of mind with Caterpillar installations on one hand is that they are actually matched and calibrated at the outset for a twin instalation meaning all parameters are checked and dyno'd as a pair, and when comissioned also so that you have the same output from both engines.

But, looking at my gauges whilst running the parameters on the port engine are always lower than the starbord, i.e Oil pressure, fuel consumption, and coolant temperature - but when I interogate the Cat Messenger Displays their readings are practically accurate within a few percent even down to the Fuel temp, Gearbox oil temp and pressure and engine load.

Incidentaly, I would imagine your engine numbers are sequential to each other?

FWIW they are beautiful reliable lumps as long as they are maintained correctly and the pencil anodes checked and replaced in the engines.

Are your engines on V.Drives?

 

[jfm]

I'm looking at a technical report on various tests carried out by a Cat dealer on two Cat 3196 engines in the same boat. These tests were carried out during a seatrial and there is very little difference between most of the parameters measured except in one area. At max rpm, the port engine appears to be consuming about 10% less fuel in terms of litres/hour than the starboard engine. In addition, the measured fuel pressure in the port engine is abour 10% higher than starboard and, similarly, the turbo boost pressure is 5% higher. The measured rpm of both engines at max speed were virtually identical.
Is this variation acceptable or should I be concerned? Could the variation be caused by differences between the props?

I'd be concerned that it needs fixing, but not that it's unfixable

10% is much more than the normal tolerance of a pair of modern engines. Both my current and previous D12s, for example, never showed more than 1 litre per hour of fuel burn diference, when burning 50-100 litres/hour each

So the question is why the 10%? What's busted or out of tune? I dunno, and from your data all one can do is guess. The port engine seems the non-busted one. The stbd engine's system is squirting more fuel in to get the same rpm and hence the same power (if the props are matched well). Reasons for that? From the limited info you have to hand a duff turbo bearing is a possible cause. Or something bad with the injectors. Or something wrong with the airflow to that engine. Some of these as you can guess are in the order of €2-3000 repairs

Latestarter could add some better guesses I bet

Are these electronically governed engines?

More importantly, does it have Sat TV?

 

[Deleted User YDKXO]

More importantly, does it have Sat TV?

Yup, thats why I want to buy it

The measured fuel burn figures were as follows

RPM Port Starboard

2000 70 85
2100 83 95
2190 98 105
2330 101 117

I believe the rpm figures must be accurate as I guess these must have been measured electronically so that can't account for the difference. What is a bit odd is that the % differences are not consistent so now I'm starting to wonder how accurate the fuel burn measurements can be but, even so, the s/b engine seems to burning quite a bit more fuel. I've raised my concern with the broker so we'll see what they say.

 

[Deleted User YDKXO]

splosh, the engine nos are 3 digits apart so I guess that means the engines were nearly but not quite sequential. No, the F53 is one of the few Ferrettis that has straight shafts and not V drives which is good because there's one less gearbox to worry about and also the V drive boxes must consume a little power

 

[Deleted User YDKXO]

aquapower, I've posted the reported fuel burn figures in my reply to jfm. What do you reckon? Within acceptable limits or not?

 

[jfm]

RPM Port Starboard

2000 70 85
2100 83 95
2190 98 105
2330 101 117

Summink is up Deleted User. I spent 250hours last summer looking at electronic gauges reading something like

1800rpm 70 71

so if I saw what these CAT3196 readings are saying I'd definitely think something is busted on the starboard engine. The non constant % difference is quite surprising as you say

Not of course a reason not to buy the sat dome (with freti 53 attached)

 

[MapisM]

The measured fuel burn figures were as follows

RPM Port Starboard

2000 70 85
2100 83 95
2190 98 105
2330 101 117

E rating (660hp), I suppose?
If so, imho the main reason why there's no need to worry is that the port engine reading is probably the wrong one.
Those babies should burn 125 l/hr @2300, according to Cat specs.
No way the port engine can drink 20% less at max rpm, unless unloaded.
And btw, also at the other RPMs, it's the stbd engine which is more consistent with official Cat numbers.

PS: on a more serious note, how large is the dome? You know, at southern Med latitudes, the bigger the better!

 

[Bilgediver]

I'm looking at a technical report on various tests carried out by a Cat dealer on two Cat 3196 engines in the same boat. These tests were carried out during a seatrial and there is very little difference between most of the parameters measured except in one area. At max rpm, the port engine appears to be consuming about 10% less fuel in terms of litres/hour than the starboard engine. In addition, the measured fuel pressure in the port engine is abour 10% higher than starboard and, similarly, the turbo boost pressure is 5% higher. The measured rpm of both engines at max speed were virtually identical.
Is this variation acceptable or should I be concerned? Could the variation be caused by differences between the props?

Were the tachos both calibrated or did you use the SAME hand tacho on both engines. Did anyone calibrate the boost gauges.

These differences are more likely to be due to unmatched tachos.

 

[jfm]

No way the port engine can drink 20% less at max rpm, unless unloaded.

PS: on a more serious note, how large is the dome? You know, at southern Med latitudes, the bigger the better!

Hmmm. It is entirely possible that the engine is not fully loaded, by virtue of having too-fine props. You'd expect Ferretti to do better, but it's possible

That prompts another line of thought. Maybe it hit a rock and someone changed just ONE propeller, and it has different pitch from the other one. Or it was built with a badly matched pair of props (unlikely with a Freti). These things would explain different fuel burn rate for the same rpm and also the different turbo pressure, on a pair of engines that have nothing wrong with them. You'd also expect the boat to drive in circles, but of course you wouldn't notice becuase the rudders and a/p would correct it. So, I would ask if both props are original or if one/both has been changed, for a start (is it one owner?)

 

[aquapower]

aquapower, I've posted the reported fuel burn figures in my reply to jfm. What do you reckon? Within acceptable limits or not?

I will have a look when I get to work tommorrow if the figures are listed in the manual I have, am currently carrying out a full service to a pair of c12 cats which are as good as the same as the 3196

 

[aquapower]

Were the tachos both calibrated or did you use the SAME hand tacho on both engines. Did anyone calibrate the boost gauges.

These differences are more likely to be due to unmatched tachos.

the rpm is measured from the ecm so there is no tacho to calibrate, if speed sensor was faulty its unlikely engine will start

another reason for excess sonsumption can be a tight cutless, has boat been sitting idle for a while?

 

[benjenbav]

another reason for excess sonsumption can be a tight cutless, has boat been sitting idle for a while?

Funny you should mention this, I had a brake caliper seize on the car recently and the first thing I really noticed was that after 50,000 miles of averaging 24.3 - 24.5 mpg, I was suddenly getting figures in the 23 range (on the same equipment).

Subsequently noticed a certain lumpiness, a scored disc and excessive heat emerging from the wheel in question but that's another story.

 

[Nick_H]

They're in a Ferretti 53 I'm thinking about p/xing my 46 for. Money is agreed in principle and we're at the checking out each others' boats stage. I haven't done a sea trial yet. The figures come from an engine survey carried out last year and which the broker has given me

Great stuff, hope the engine issue proves to be minor, and you can proceed with the deal.