Smoking issue when using oil pan as return location for turbo oil drain.

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  • This info is for anyone that is using the oil pan for the drain location on their turbo setup. It is not just Alpha systems because I know there are some Hahn systems that used the pan as well. It was just easier to swap an oil pan then for some to drill and tap the block. And I know there are many many many many running their systems with the return in the pan that have had no issues. So this is not a "you must change it now or doom and gloom will happen" thread. This is a simple and informative thread that illustrates what we have found out and how I am going to fix my issue. (Longest sentence i have ever typed coming up :):D .) So if you are reading this and you have a turbo system that has the drain located in the oil pan and you have never had to add oil because it was low after a day of riding OR you have never had it to smoke when you rev the engine up after sitting a minute and you have put many thousands of miles on the system this way then you may want to ignore this post. I cant explain why you haven't had any issues. But here is what I found out today.


    FIRST,,,,I cant take credit for discovering this. @iNewton and I were talking the other day and I mentioned to him that my Slingshot was running great and the only weird issue I was having was some oil smoke when sitting still for a min or taking off from a stop. I told him it was perfect when I first started the engine. But after blipping the gas a few times it would puff oil smoke from the exhaust. It would clear up once I was moving (or at least I cant see it once Im moving). Then at the next stop light I could sit there all day at idle and it would not smoke. But as I would get ready for the light to change I would mash the gas pedal a few times and the exhaust would get progressively smokier. But only when the engine was revving up. After it idled back down the exhaust was clear.


    Well after explaining this to @iNewton he asked me where my oil drain was located. I told him I was still using the Alpha custom header and muffler. So the turbo sits a bit lower than my Hahn system I used to run. This makes using the factory block bung almost impossible to use. So I use the oil pan location.


    He told me that I shouldn't use that location because it was below the oil level in the pan. And that oil was not able to freely drain back into the pan. He said it would stack up in the drain line and finally push past the sealing rings in the turbo and this would cause it to smoke just like I had described. (Which made sense). However,,, me being the way I am, I argued with him for a minute and told him that my return port was welded into my pan so high up that their was NO WAY my return line was sitting below the oil level..... And with his persistence he got me to questioning the whole issue.


    SO, I went to the garage and checked my oil level and it was 1/2 way up the area on the dipstick that its supposed to be in. Basically perfect. I looked around and grabbed the first small container that I could find to catch any small amounts of oil that might come out of the oil drain return hole. Well in this case it was the cover to a 25 pack of blank CD's. I figured that would be easy to hold with one hand while I undone the hose.


    When I unscrewed the hose oil poured out like I had just unsecured the pan drain bolt. It had to have 1.5 to 2 quarts of oil above the fitting. As you can see by the pictures the floor of my shop is covered now. That is a lot of oil.......


    You can't have your oil return line below the oil level. It just wont drain. Now that I know this I can see why it was smoking. When you are running the engine takes about 3/4 or maybe even 1 quart out of the pan. This would lower the level a bit. But it would still cover the return hole in the pan. However when your driving the oil is being moved around and there is also vibration. So it should be able to keep the oil flowing back into the pan. However once you stop the return hole would be covered by oil. And this would mean that as you sat at idle the oil would be running slow enough to kinda drain and not smoke. But once you rev the engine and the oil pressure comes up the oil would not have anywhere to go. It would essentially stack up in the return line and the only place it can go is out into the turbine side of the turbo. And burn up as smoke. Depending on how you drive you can see how some may not really notice this. And I'm sure as the turbo gets some age the ring seals would probably get weaker and leak more.


    So what is the fix? Well I am typing this at 4am in the morning and sometime today I am going to go back out to the shop and see if their are any fittings that will allow me to use the factory bung in the block of the engine. Fortunately for me I always drill and tap that hole in my engines before they are dropped in. The last engine was no exception. It has a 3/8 NPT plug screwed into the factory bung hole. I figured I might use it one day so I always drill and tap it while they are on the engine stand. If I remember correctly the Alpha turbo sits low on mine and their will not be a lot of slope in the return line. And it seems like I only had 45 and 90 degree fittings to work with when I tried to make it drain into factory block location. I have some 22.5 and straight fittings now and some black hose that is 3/4". So when and if I get it to work I will post pictures of what I did. The only other way would be to use a scavenge pump. The good scavenge pumps are $400.00 and that would just introduce another part that could fail into the system. So I want to try the factory drain line location first.


    Ill post more info and pics later. Hopefully i will get it figured out early so I can ride locally and test my new fix out...


    Just remember when you look at these pictures. There should be NO oil that comes out of the drain hose when you unscrew it . Maybe a teaspoons worth but no more.... So this in my opinion is bad.... And I will also include the Precision Turbo installation information. Seems like they would agree........







  • @VIPNiSS - Hey Smokey
    This may be for you scroll up!

    THanks for tagging me. You have no idea how much this irritates the hell out of me and I been trying to chase the problem. @rabtech described my exact issue. During cold startup it was fine and never smokes. I do smoke a little when I am at a stop light and get on it from a stop. However the most smoke is when I turn off the bike and fire it back up after going in to a store or filling up gas. It's a big cloud of smoke and then goes away. My initial thought was I was letting it idle too long before turning off to cool turbo. I used to idle for about a minute or so but cut that down to about 30 seconds and same thing. I'm looking forward to rectifying this with the knowledge of this group. Thx rabtech and all the contributors to hopefully fix this issue once and for all.

  • when I was running alphas original turbo setup I never had any smoke issues but since I installed top mount with side exit exhaust and ddm oil cooler kit and relocation I have a smoking issue especially when on an incline I also get more of an oil smell hear and there and no leaks.

  • Well I have actually torn it down to the point where I can see what I'm working with. Its not looking good. Unless they make some kind of close ratio drain adapter for the turbo side its going to be hard to make the smooth flowing angle over to the drain side. Especially with the engine mount in the way. I will look around and see what I can find on the web. I really don't want to run a scavenge pump and container.







  • I beleive it will drain into the block bung hole if i get a close ratio 90 degree flange for the turbo and a 3/8 npt -10 90 degree fitting for the block. I may have to apply a smidgen of a bend on the block side fitting but i think it will all work. And i may have to slightly clock my center of the turbo toward the engine. I checked and we can safley have the turbo at 30degrees. The main thing is that the oil gravity feeds back into the block. So you can almost turn the center toward the bung hole in the block.




  • I do not know if this will help but there is a machined brass 90 degree fitting male pipe on one side and female on the other. On the 1/4 inch npt fitting it will only take up I think less than 5/8 of an inch above what it is screws into. I just looked it up, in the one company it is called an extruded 90 degree street elbow

  • The thing that puzzles me the most is why doesn't all the alpha guys have the issue that's running same or very similar setup.

    Not sure. I know that there are several that have this issue and one fix that was thought to have relieved the issue was to drill the hole in the intake.


    The one thing i am sure of is that to be reliably smoke free and to satisfy the turbos requirements you can NOT drain it into a hole that has almost 2 quarts of oil above the drain hole.


    Everyone will have to read through this thread and decide if they want to change the drain location and give it a shot... I will have mine swapped over to the bung in the block in the next two days. Im going to overnight 2 or 3 different "extruded" 5/8 fittings and out of those two im absolutly positive i can make a dependable sloped drain toward the proper bung in the block. I have determined today that it CAN be done and will drain the oil much better than where it was in the pan. When I finish with my setup I will post my results and all the parts and pictures here. So bear with me till i get mine completed.


    I have a friend that could make my fittings and weld the angles that I need to the flanges. However today I decided against that it because it wouldn't help anyone. Members couldn't easily duplicate that type of fix. So im sticking to orderable parts.