Excessive Blow-by on Kama 554

[greg_g]

The diesel engine, while less prone to backfiring, nonetheless can happen.

Let me try this again.

Bob - I'm not sure I've ever heard a diesel backfire. But I think you're saying that - despite the fact that diesels are less prone to backfiring - use a PCV valve anyway? I ask this, because I mentioned a check valve in one of my earlier posts. I just wasn't sure at that time if it was appropriate to call it a PCV valve

//greg//

 

[Bob Rooks]

Greg,
Yes, they can backfire but not in the traditional sense of miss-firing. Over-fueling caused by a badly dribbling injector can create a situation where the combustion continues even after chamber scavenging. This occurs most often in two cycle diesels that are port scavenged, but the same bad injector together with improper valve lash and/or injector timing in a four cycle diesel will produce similar negative results.

I would personally use a Positive Crankcase Ventilation (PCV) (check valve) valve regardless. It's pretty cheap insurance even if it's never called upon. Most automotive types of PCV valves will have a (light) spring loaded ball check that has a threshold of around 1" Hg so that there is no free flowing volatile air after the engine is shut down.

Of course the obvious reason for PCV is to evacuate the crankcase vapors and make them go out the exhaust, after they've been burned, again.

 

[Dave_Lilly]

You're doing it again Dave. All I did initially was address your suggestion that Rob replace his breather. I thought you might be interested in learning what the TEPM version of the FeiDong 395/495 breather looked like, and how it worked. That should have been the end of it. You're the one who keeps straying down these other side streets. So let's just drop it, shall we?

Moving back on topic, I agree with your recommendation to Rob that he NOT procede with this return hose idea. Although having said that, some variants of the YangDong Y85 engine actually had a return hose. But it was between the valve cover and the crankcase, rather than between the breather and the intake manifold. Not sure, I think there may have been a check valve involved too.

My Mercedes turbo diesel on the other hand, does actually route valve cover emissions directly into the air filter housing (bypassing the paper filter). Perhaps heat from the turbo incinerates it, because Mercedes engineers were apparently not concerned about engine runaway from crankcase fumes.

//greg//

Why do you try to compare apples with oranges? Your "Mercedes" is a smart vehicle that should have a computer, many sensors, a PVC valve and other German engineering devices that would prevent any possibility of engine destruction.
A Chinese tractor is basically a dumb machine that has no sensors, computers or special valves. The compression relief system is a manually operated cable system that opens the exhaust valves, which not only makes a diesel tractor easier to start but also functions as a relief (If applied in time) to prevent a diesel engine from destroying itself by using it's own oil as fuel in case of a catastrophic breakdown in the valve\piston\piston ring assembly.
By the way, I Wikipediaed knickers and this is a very old term for underware. If you were in the US Navy you should know that US naval personnel use the the term "Skivvies" for their their Bloomers.
Adios Admiral!

 

[Egon]

I have a pair of well worn Knickers! They are pants worn when skiing, hiking or engaging in other such outdoor sports.

 

[greg_g]

Why do you try to compare apples with oranges? Your "Mercedes" is a smart vehicle that should have a computer, many sensors, a PVC valve and other German engineering devices that would prevent any possibility of engine destruction.

Quit before you get any further behind Dave. I shouldn't have to justify the reference to my Mercedes. But I have the classic old 617 turbo-diesel, which has roots in a 1953 engine design; no computer, no sensors, no PCV valve, no special valves at all. This engine no "smarter" than is Rob's FeiDong 495. Just like on his KAMA, my engine management system sits in the driver's seat.

//greg//

 

[greg_g]

Of course the obvious reason for PCV is to evacuate the crankcase vapors and make them go out the exhaust, after they've been burned, again.

Understood, and thanks. The fact that my Mercedes doesn't have a PCV valve must then be related to the turbo-charger. Besides the incineration factor, perhaps it also functions to maintain lower pressure in the intake than in the crankcase.

//greg//

 

[Flyhiflylo]

Understood, and thanks. The fact that my Mercedes doesn't have a PCV valve must then be related to the turbo-charger. Besides the incineration factor, perhaps it also functions to maintain lower pressure in the intake than in the crankcase.

//greg//

A tubro creates more static compression... Thus more blow-by... So a turbo actually needs a PCV system more than a N/A engine.

 

[greg_g]

A tubro creates more static compression... Thus more blow-by... So a turbo actually needs a PCV system more than a N/A engine.

I think what you mean is that turbo boost adds to the static compression, but I understand your point. Thanks.

Take my word for it though, the 617 engine has no PCV valve. Even if I bought an aftermarket valve, there's noplace to install it. Nothing but a large PVC tube between the valve cover and the air cleaner housing. That's why I tossed out that idea that - in this case - perhaps the combustible component of the blow-by is incinerated before it is introduced to the intake valves. Oh, and there's a vacuum EGR component as well - which might raise the post-intake temperature even more.

//greg//

 

[Dave_Lilly]

Quit before you get any further behind Dave. I shouldn't have to justify the reference to my Mercedes. But I have the classic old 617 turbo-diesel, which has roots in a 1953 engine design; no computer, no sensors, no PCV valve, no special valves at all. This engine no "smarter" than is Rob's FeiDong 495. Just like on his KAMA, my engine management system sits in the driver's seat.

//greg//

I hereby kneel to the lord of all diesel tractor knowledge and admit that I have been put in my place by a God of all things diesel tractor. I realize that it was a grievous error on my part to question your all knowing, all seeing knowledge by such a God of tractor problems that you are. Please accept my humblest apologies for ever questioning your ultimate knowledge of all things concerning diesel tractors. Oh why, oh why, did I think that I could contribute to this forum without first consulting you about your wealth of knowledge since you are the ultimate go-to guy?
I am sure that all of the people on this site will avidly await your solutions to their diesel tractor problems.
As far as me, I don't feel that I could ever post anything here that would be of use to anyone, due to your superior knowledge.
Please forgive for questioning your vast knowledge and kindly kiss my posterior.

 

[Flyhiflylo]

I think what you mean is that turbo boost adds to the static compression, but I understand your point. Thanks.

Take my word for it though, the 617 engine has no PCV valve. Even if I bought an aftermarket valve, there's noplace to install it. Nothing but a large PVC tube between the valve cover and the air cleaner housing. That's why I tossed out that idea that - in this case - perhaps the combustible component of the blow-by is incinerated before it is introduced to the intake valves. Oh, and there's a vacuum EGR component as well - which might raise the post-intake temperature even more.

//greg//

Well since you are talking to me, I don't have a clapped out 35 year old Mercedes like yours. So I may be a bit out of date. But, my 2006 SUPERCHARGED Mercedes does have a PCV valve.

Maybe Rob would like examples of modern technoloy.

P.S. So what do you do with all your time now that you are retired? (Besides repeat what others have already said on message boards)