Crankcase pump, Anyone run one? Options

[BMXerror]

Hey all. Anyone here run a vacuum pump one their crankcase? I've been thinking about doing it on my tenner, but I don't know what to use. I would like to go with an electric pump for ease of installation and for minimal horsepower drain(because of no belt drive). Just an idea. I don't know much about this at all, so I'm open to any advice/criticism...... Of course, maybe I should actually get my car RUNNING first. (IMG:style_emoticons/default/dry.gif)
Mark D.

[davep]

What are you trying to accomplish? So far this does not make sense to me.

[JPB]

I was looking into EV's electric vehical sites and remebered that they used an electric vacuum pump to run breakes with boosters. Its been many years since I have searched this info but you should find some products fairly easilly.
Got a big breather box for all your case/highrev preasure issues?

[Mark Henry]

What are you trying to accomplish? So far this does not make sense to me.

(IMG:style_emoticons/default/agree.gif)

[BMXerror]

What are you trying to accomplish? So far this does not make sense to me.

On any engine your crankcase will build pressure due to blowby. The crankcase breather is supposed to deal with this problem, but on stock cars they're rarely up to the task in extended high performance situtations, thus, the large breather box that JPB mentioned. However, some people prefer to run the crankcase under vacuum, the most notably being dragbike teams who are pushing over 350 RWHP out of 1500 CCs. Now, you would think that any advantage gained by the piston being assisted downward by a vacuum would be nulified by the piston pulling against a vacuum on the way back up. This would be correct if you're thinking in terms of a one cylinder engine, but that's not the case. As one piston goes down, another will be concurently going back up, balancing the volume, and thus, air pressure in the case. With that being said, the theory that those drag bike teams opperate under is that by running the entire crankcase under vacuum, the pistons will have less air molecules to push against, freeing up horsepower to turn the wheels, instead of to turning the engine. I hope I explained that right.
So, some people run a belt driven pump where their breather would normally be. Others hook a breather into their headers, so that the exhaust velocity creates a vacuum without draining engine power with a belt drive. This works but is difficult to do right without interfering with the proper exhaust flow, and ussually doesn't create as great of a vacuum as a pump. Still others run an electric pump, which is what I want to do. This doesn't pull from the engine, and also is easy to install because it can be put anywhere with no need for a drive from an external power source. Some people use smog pumps off of GM cars, but they don't produce much vacuum. My question was if anyone knew who makes an electric pump that can handle this job. It's an open question since it doesn't have to be MADE for a crankcase pump, it just has to work. Open to suggestions.
Mark D.
PS Another thing you do have to worry about is the vacuum dropping your oil pressure. It is a ligitimate problem, but it's aleviated with a larger oil pump

[davep]

Well, first off the electric pump will run off the engine; via the alternator and with two additional losses of power due to the efficiencies of the alternator and the electric motor. Better control of the blowby by the rings would be my first choice; rule #1 minimise the problem first, then optimize the solution.

The breather tower atop which the oil filler resides is a pretty good size. Your engine iteself is a pretty good vacuum pump. Connect the two with nicely sized tubing and I think you would do well.

IMHO the cost/benefit ratio is far too high. How much energy do you think it takes to push those pistons against the air? If you were pulling 15000 RPM and if you were making 200 hp/liter, then maybe there would be some benefit.

To be perfectly honenst, I think you are (IMG:style_emoticons/default/dead horse.gif) Sorry.

Resident Mad Physicist

[Aaron Cox]

isnt this kinda what a dry sump scavenge pump does???

[john rogers]

The three stage Autocraft dry sump oil pump I had on my stroker four created a very healthy vacuum in the main case at high RPMs. Was it good for any power, not sure, did it suck the oil out of the valve cover area, you bet. The drag racers use an "exhaust sucker" and I actually tried one but it left a slight trail of oil smoke from the exhaust which I did not like and neither did track officials. I guess if the car had been English, it would have been okay them??!!

[Brett W]

There is five to 15 HP to be found in oil control in the T4 engine. What you are trying to do is faily common in certain forms of motorsports. Many types outlaw it, though. You could do a cheap and dirty exhaust extractor type of breather. Run a tube into the header collector and you connect it to the breather on the engine. It can work better than nothing, but for the most part you will find it is not really worth the trouble.


Until you have maxed out the other parts of the engine system, you won't gain much. Now if you are ready to play with some two ring gas ported pistons, dry sump, maximum effort race engines we can talk.

[Aaron Cox]

hey brett,

im interested in what your talking about. not to implement, simply to learn.

so you use the exhaust to scavenge your crank case pressure?

[Brett W]

in the collector, actually at the far end of the collector there is a pretty decent degree of velocity. It can be used to pull a vaccum on a tube put there. You will have to play with the angle of attack to get the maximum pressure drop inside the tube. But this tube can be connected to a sealed crankcase setup to help pull crankcase pressure out through the exhaust. It will never pass any kind of emmissions test but if you are exempt you can play with it. You will have to install an anti-backfire check valve to keep it from working in reverse if there is a backfire in the exhaust system.

I wanted to try it pulling through a breather box/reservoir and directly from the crankcase to see if there was a way to keep oil out of the exhaust line.

This setup works really well with a true merge collector with a tapered cone on the exit side of the collector. It helps speed up exhaust velocity.