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problem gasoline in the oil

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Hi everyone, I wanted to ask for info on what is happening on three identical engines with the same characteristics of modifications. 1800 cc 4-cylinder supercharged watercraft engine on which the vipec v88r plug and play ecu with g4 + link are mounted. All three have a very important quantity of petrol that drips into the oil: in fact an engine has broken due to a large quantity of petrol in the oil. What I have noticed for now is that afr is quite lean at 13.5, but the egt temperatures also confirm this. I state that I am now mounting the probe for afr reading in a more ideal place to see if there was perhaps a false reading: I also disabled the fuel trim of the two central cylinders because I thought it was this but it is always the same. I also have two same engines wired with the old vipec v88 with g4 links that work very well without contaminating the oil: the only difference is that the base maps given by them differ in petrol pressure: the v88r link g4 + works with injectors from 1000cc to 55psi static and VE quite large, instead the v88 link g4 works with the same injectors from 1000cc to 65 psi static and VE much lower and goes well with afr 12.5 without contaminating petrol with oil. Another difference that I noticed is that the link g4 + the sequential injector timing is 375-475, instead the link g4 is set to 100-100. Anyone have any advice to give me? thank you in advance I attach the base maps

Attached Files

Normally I would expect significant oil dilution to be from fuel leaking past the rings, but if it's that bad I would expect it to have shown up in other ways, like ring wear and cylinder leakage or even, if it's really bad, broken rings from hydraulic lock.

However, there may be a different route for the fuel to get into the sump - there aren't many options - if the engine is significantly inclined, and that is for a leaking injector, or several, to drain back into the intake ports and plenum and, from there, to drain into the sump. A bit of a long shot, but...

It might help if you identified the specific water-craft in question, and any other modifications that may have been made?

Oh, as it's a water-craft, there may be oddities in the various breathers to prevent fuel vapours building up, is it possible there is a problem somewhere on that side of it?

hello it's not a mechanical question because that type of ecu is mounted on three watercraft and all three have the same problem

Ah, sorry, re-reading the initial post, it is the engines, not the water-craft that are the same.

However, the basic point still stands in that the problem is common for all, and so my viewpoint is that all aspects should be considered and that is why the actual applications would have been handy - similar engines have also been used in ATVs and even Formula First/Student. If you are sure it is ECU related, fair enough.

However, if it is the Yamaha GP1800 engine, which fits the description, the latest version seems to be particularely prone to GIO (Gas In Oil) if the thermostat isn't correctly used, eg -

When you do figure it out, please update it as it must affect others, too.

mmm sorry but in my opinion it is not a question of engine cooling I handle many of these engines, I do not think that adequate cooling can evaporate all the oil that goes down. I think it is a question of electronic management of the ecu

No worries, you've got the machines and can be 'hands-on' and in a position to actually see what's going on.

If you'd update this thread with what you find, it may save some folks from having to chase down the same issue, thanks.

It sounds like you've identifed differences, but haven't tried changing them with your newer ECUs to see if that makes a difference.

I imagine the higher fuel pressure would improve the atomisation of the fuel and might make a difference.

The Fuel timing might also cause more fuel to hit hot valves, again helping the vaporisation of the fuel.

Let's us know what you find out. An interesting problem for sure.

hello surely if I find the problem I'll let you know, I was hoping for a lot of help anyway thanks.

translator. hello to everyone, I can say that I have solved the problem of the large amount of gasoline in the oil, I changed the sequential injector time from 375 to 100 and totally changed everything, no more gasoline in oil thanks to everyone. thank you

Cool, thanks for the update!