Blow Bye tube hooked to exhaust?

[AKimmel]

I'm wondering if I can attach my blow bye tube to my exhaust pipe with a small tube aimed toward the rear so that it will pull from the blow bye tube and not try to send exhaust back up it? The reason I want to do this is, everything under my truck is painted nice and over time I get an oily film on my transfercase and rearend on the left side. And no its not excesive, but it shows up on any thing painted gloss black. I know most people wouldn't care, but it would be easier to keep clean if it didn't get there to start with.

 

[Greenleaf]

Use the sock method used by the 24 valve guys.



BTW I have two (12 valve) trucks and they don't have blow by oil mist covering anything. Hmmmmm... ... ... What do YOU consider exessive blow by??? All I gets is a drop of oil from the tube time to time.

 

[AKimmel]

What do the 24 valve guy's do? I only see a drop hanging from the tube once in a while. I don't think you would see it on a stock truck (maybe), but black shows everything, and you see it because its not as shiny were the film is. Is there a down side to hooking it to my exhaust? How can I check for too much blow bye, can you see it sitting still, or is it only under a load when it would do it?

 

[AKimmel]

Sorry I just realized you said "sock" method, I read it as stock method.

 

[Greenleaf]

Blow by is checked with a monometer. Not that which is used to test women for cancer either. It's a tube with water and marked in inches. I **hope** I got that right.....



The book lists a spec. for inches of water. It's pressure basically. I "could" go look it up. It probably gives a description of said tool.



The sock method is pictured in issue #50 maybe? Not too long ago.

 

[1stgen4evr]

I am pretty sure you know that crankcase ventilation is conventionally done by connecting to a vacuum source, ie intake. That insures that whatever vapors/hydrocarbons do exit the crankcase get burned and not dumped into the environment. While you might devise a venturi action into the exhaust, I can see where that would have the potential for trouble if it didn't function correctly at all throttle levels.



But thinking outside the box is something first genners are well known for. Certainly the desire to contain the drip has merit. With higher miles, lots of folks are going to want something to help with the drip. If you make it work, give us the details.



What would be the effect of a catch canister on the vent tube?



James

 

[AKimmel]

I don't think it could be hooked to the intake because of the boost pressure. It would have to be connected preturbo, and that would put oil all in the intercooler and such. I know its bad to send oil into the enviroment, but its already blowing around as it is, so going out the exhaust can't be any worse. If I do attach it to my exhaust, I'm thinking an elbow inserted into the exhaust pipe with one leg inside the pipe toward the rear and the other sticking through to attach to the blow by tube. This way the passing exhaust should create a vacuum, and not tend to pressurise the tube. I know that some drag cars do this, but I'm not up on the specifics.

 

[keimmmo]

Even for your proposed modification to work on a Drag vehicle, two things are required. First, there can not be any back pressure in the exhaust system. If there is, it will still back up through the tube even though you have it pointed to create a vacuum. Second, you need to add an "anti backfire valve" between the motor and exhaust. If you don't, the exhaust could potentially ignite the vapors in the crankcase... really bad news!



If you have a fairly large exhaust with a straight pipe or at least a big straight through muffler, it might work.



Steve Keim

 

[RailroadJim]

Someone has tried that before

It's been tried before or atleast talked about, I read about a guy doing that either on here or dieselram.com(org?) maybe?

 

[TBurow]

all you need is an air tube check valve from an old gasser, and a piece of 3/4-1 inch diam. pipe 6-8 inches long (the longer it is the longer the check valve will last because it will be cooler) cut at a 45 degree angle welded into the exhaust pipe. the check valve prevents exhaust pressure from getting pushed into the crankcase, and the angle cut causes the exhaust passing over it to pull vaccuum sucking vapors out of the crankcase( by the way the angle cut end goes into the exhaust with the opening facing the rear of the exhaust system so air flowing over it will draw out of the engine).

 

[AKimmel]

Thanks for the replies, I have some air valves from my 89 that I took off, so I might try that. I noticed Milodon sells what they call "vac-u-pan" and its nothing but a breather and an air valve with an angle cut tube attached. And I do have a 4" straight pipe, so I shouldn't have much if any back pressure.

 

[keimmmo]

Sounds interesting! Let us know how if works.



Steve Keim

 

[CLiberty]

A fella by the name of hohn on the DTR tried it IIRC, give it a whirl I say, just make sure you have a one way type valve in there to prevent popping seals etc if it doesnt do as expected.

 

[cojhl2]

My opinion,, I would not do this. I dont think it's good to have a vacum in the crankcase.



One of the posts discussed this but remember on a SI engine there is a spring loaded check valve called a (darnit can't remember the name) to keep backfire from entering the crankcase and also to keep from creating a vacum in it.

 

[AKimmel]

I know on a gas engine, vacuum in the crankcase is a good thing, it makes the rings seal better creating more horsepower. I know people run vacuum pumps on some race cars for this reason, but I don't know about vacuum in a diesel engine. Whats a SI engine?

 

[HRDROKN]

I am pretty sure you know that crankcase ventilation is conventionally done by connecting to a vacuum source, ie intake. That insures that whatever vapors/hydrocarbons do exit the crankcase get burned and not dumped into the environment.

Our trucks vent the crankcase directly to the atmosphere, it was even that way with my 2001... so would putting the vent under some vacuum i. e. sticking it into the exhaust hurt the rings ability to seal under boost?



I am getting quite a bit of blowby with my motor now that I've turned it up. The biggest reason in my opinion is that I have 280K+ on the motor.



I have thought about just running my vent hose all the way out back or running it to a catch bottle down by the transfercase...



.

 

[TBurow]

i seem to remember seeing it somewhere that the new cummins got some type of pcv system? off the vac. pump?

 

[cojhl2]

PCV Valve thats it!!!! (Positive Crankcase Ventilation) SI engine == Spark Ignition Engine. .

 

[1stgen4evr]

High boost on the various bombing project will increase blowby NOT as a function of high miles but rather squeezing by the intake valve stems. As the valves begin to wear more, the blow by will become more noticable. The loss at the stems will also take a bit of oil with it and one might think that the engine has poor rings. Not so generally. Back pressure from a tight turbo will also push some gasses by the exhaust valves (which rather quickly become worse). All contributing to more blowby than a stock engine with equal miles.



There is no doubt in my mind that a devise near the end of the exhaust pipe would provide constant vacuum.



James

 

[HRDROKN]

OK then....

OK so with that being the case (makes complete sense to me). Wouldn't putting the crankase under vacuum now increase this problem? Pressure on one side and vacuum on another.....