J-Ville VR-4

Crankcase pressure is a bit of an annoyance on VR-4's, and I was thinking about it the other day. Then somehow a TII air pump popped in to my head around the same time.

Has anyone tried hooking up the intake side of the air pump to the crankcase on an RX-7? It would be a stock vacuum pump. My VR-4 doesnt have one, so I cant try it. But vacuum in the crankcase kicks ***, and this sounds like it will be way better than the stock PCV system on your cars.

Your comments on this?

NZConvertible

Rotaries don't have a crankcase to pressurise. All the sump needs is a little ventilation, which the stock set-up does fine.

yearrgh

Before you get flamed for not knowing the difference between a rotary and a piston engine, thanks for taking the time to offer us something that you thought might have been helpful to us. Now prepare for others to call you an idiot and ask if you're aware that a rotary doesn't have a crankcase, crankshaft, pistons, valves, camshaft, etc...

Drifter101

hahaha.... let the flames begin!

Center of The Universe

I think we should go eazy on him. It's not like he knows about the magic triangle engines. I mean. The guy has a 3000GT.

rxse7en

What happened to the guy who wanted to use the airpump as a supercharger?

Terrh

iTrader: (7)

something happened to his airpump and he gave up. Too bad, really.. I never thought it would work, but at least he tried!

Cory Simpson

WTF, how would that work, you wouldn't even get 1 psi of boost, or would you.

Jaared

he was gonna boost a gokart engine


jaared

FC3SPORT

My airpump makes an excellent rust experiment in my basement..

FC3SPORT

What about the guy that wanted to buy a plastic electric impeller turbo?

Jaared

plastic impeller turbo...... HA!

bad idea... well unless you like plastic impeller fins in your engine.

jaared

Bigretardhead

I think I'm going to try to mount the air pump where the A/C used to be so that I can keep my TID mod, and still pass emssions.

in evil circle engines, why does vacuum in the crank case kick ***?

Jaared

damn.. if my ac is broke im gonna do the same... well do hi flow cats need the airpump?

hmmmmmmm ahh yes... hmmmm indeed!

jaared

Cory Simpson

You know I should try to fro tech that up to the go-kart that we have in our garage, that would be awsome if if worked. Although I think the go-kart pulls more air than that thing can pump.

J-Ville VR-4

I know how a rotary engine works, my dumbass mind was too into my 3L piston engine at the time I posted that, and it was very very late, insomnia does that to ya.

OK, PCV 101
Let me start by saying basically all engines have blowby. That is, pressure that leaks out of the combustion chamber. Compression tests are done to see how good your engine's compression is - the better the compression, the less blowby. If you have bad compression, a leakdown test can be performed to find out exactly where the pressure is blowing by, but this doesnt really apply to rotaries, and I'm getting off topic. On rotaries, the blowby gasses that get by the apex seals simply escape to another side of the rotor and either become part of the next combustion cycle, or flow out the exhaust. On piston engines however, the blowby gasses can get past the piston rings and enter the crankcase, which pollutes the oil and builds up pressure where there shouldnt be any. Pressure in the crankcase makes it harder for the piston to travel down, which equates to a loss of power. Also, if too much pressure builds up in the crankcase, oil can be forced from the crankcase past the piston rings into the combustion chamber, and burning oil means a lower octane mixture which will lead to detonation.

Sooo, we need to keep the crankcase from being pressurized. The simplest way is: vent the crankcase to the atmosphere. Works great for keeping the crankcase non-pressurized, but the blowby gases are still chillin in the crankcase contaminating the oil because theres no vacuum to suck them out. This works good, but you need to change your oil a lot to keep it clean. So, a better idea is to put a vacuum on the crankcase. Most cars simply put a vacuum line from the crankcase to the intake. Works pretty good, but on my car (and many others, forced induction screws this up) vacuum turns to boost, and the crankcase is pressurized again. A PCV valve is used to work with this. Its basically a check valve. Under boost, no vacuum is present in the crankcase, and the gasses, and even oil will get pushed into the intake track, gunking everything up.

So, vacuum at all times kicks ***. If theres enough vacuum, it keeps your oil really clean, and it actually helps pull the pistons downward, increasing power. Serious racecars use vacuum pumps, usually electrical, but I thought why buy one if your car has one on the beltline?

Sorry for the long post

Jaared

sounds like a good idea.. dunno if it will do what you are tryin out.. but hey there is one on ebay for like $10..
check it out.

jaared

dr0x

Lots, and I mean *LOTS* of experience rotary people will call it a crankcase. e-shafts and cranks have the exact same operation. Cranks are just more common so people will know wtf you are talking about. Hell when people ask what my CAS is I just tell them its a distributer..