turbo scavenge pump question
 

can i loose the turbo scavenge pump if i drain my turbo (probably k27hf2) into the lower cam cover? am i right in thinking that the job of the cam powered pump was to suck the oil back into the engine and that the oil feed to the turbo came from the pressurized oil circuit?

Kevin at Alamo Turbochargers made an interesting observation on this matter. If an engine has blow-by in the cylinders, the crankcase will become pressurized, defeating a gravity feed type system. Other's swear by gravity feed.

On theory I heard that make sense was... if you have the old case where the drain plug is in the bottom, gravity would work as that's exactly where the oil pump is. If you have the newer case where the plug is on the side, now there isn't a "straight" path so there's much less suction power.

Why would you want to lose the scavenge pump?

Interesting therory Dave. Hobbieboy, ive never had a scavenge pump! i bought a case and crank and started from there so a scavenge pump was on my 'bits to buy' list. i spoke to a bloke over here who doesn't run a scavenge pump. his turbo oil feed is from the oil pressure switch and it gravity feeds into the bottom of the case somewhere. ive seen a couple of turbo installs on this board (i think). his reason was that its one less thing to go wrong....

how about a banjoe fitting instead of a oil plug??best of both worlds??

When I bought my car, it doesnt have a scavenge pump.
When I switched to kevin's K27HF, he strongly recommended me to get one to prevent drowning the turbo. I did. And mine leaks :( But I'm going to fix it somehow during this rebuild :)

afterburn, i don't get what you are saying, could you explain a bit more?

hobieboy, where does your turbo oil feed come from? and is the return to the scavenge pump a long braided hose or something like that?

sure-a banjo fitting (like on your rocker boxes) oil comes dwn and into your sump via this special fitting from your pump. You should have a suction going there in that area . So in more words here,, you have plumbed the return from turbo to bottom of crank case. that help??

Andy,
The oil feed comes from the front of the engine where the oil pressure switch is (beside breather cover).
The return is a combo of hard & aeroquip - factory + GHL setup. You could easily make the entire line with aeroquip hose.

I'm very interested in the result here. with a banjo to the drain plug would the foamed oil coming out of the turbo be able to go down and then up again a little into the sump? This also seems like a fairly vulnerable position for an oil line...?

Maybe Henry S. will chime in here...was a fleeting thought on my part. I can see some pros and cons to it. most of the oil in the sump got there under pressure any way . Its a dry sump system so it should not matter about foam as its on the back to the tank....the pick up (pressure side) for the bearings and such is not at the sump but in the tank..as far as vulnerability.......dont go jeepin.

My engine does not have a turbo scavenging pump and does not need one. Granted my turbo sits slightly higher than the stock 930 turbo position, but all you need is a short, slightly downward, unrestricted flow path that is large enough to keep the oil from backing up into the turbo.
Like Tyson says, it isn't rocket surgery.

Running the line to the drain plug might cause problems. While under boost there is a positive G force on the entire car, includuing any oil that is trying to drain through that hose. If it has standing oil in it (which it would) the G forces would slow down the flow and possibly kill moskitos.

If the proposed line to the chain cover is low enough to provide a downward slope it should work just fine IMO.

Sammy, do you have a photo of your turbo mounting and drain line? Are you using some BAE parts? early or late style heat exchangers? Thanks in advance.

cheers afterburn/hobieboy-sammy, what id pipe are you using? got any pics of the install?

You might be the proto R and d!! I have yet to complete mine yet, but as a rule of thumb dont step the size dwn any as its mostly a gravity situation there.
I was going to in the chain cvr, (In fact its all drilled and tapped now) but to swing it into the oil pick up area seems to be a good idea till proven other wise

hmm...tricky.....

I use 5/8" hose which may be overkill. basically I installed the largest size I could fit.
Prior to this, i tried using a drain hose from the turbo to the driver's side lower valve cover. It didn't work. Major smoke screen under full acceleration. My best guess was that the run was too long and didn't have enough slope, and that the G forces under acceleration prevented the oil from properly draining forward.
I moved the drain point to the lower corner of the chain cover and had no further problems or issues.

This has been discussed here and there. See these links.Gravity drain

Turbo oil pump

There's another thread on the Rennlist site, in the Turbo/930 forum, called "Let's talk about venting and breathing" The last post in that thread was 8/10/05. I would have posted a link to the URL, but for some reason, it doesn't show up for me. You can find it with a quick search.

Oh, and here's one more thread on this topic:


Oil line size for K27s

well, they are all gravity drain, but some use the factory pump (the small turbo pump) to get the oil out of there , others dont....so I can see no reason not to let gravity do the job,, the scavage side of the main oil pump is more then enough to get it back to the tank. (esp if you use restrictors)