Dry Sump

[Garry Sharp]

It's kind of quiet over here so I'll ask a question. Does our single stage oil pump scavenge oil out of the engine faster-ALOT faster-than oil drains in to the engine?(when running). It seems I am leaking oil from behind the pully on braking, even with a sand seal. If the oil pan is virtually empty, as I was told, there shouldn't be much oil up that high.

Thanks,
Garry

[sracing]

Gary,

The pickup stage of the pump is about 20% larger than the pressure side, so it has the capabilty to pump more oil. Thus scavenging the case. However there are some variances. The front of the case where the cam gear is has a cavity that can fill with oil sometimes under deacceleration. If you have a bit of blowby (leaking rings, etc) the case pressures can be higher than normal and force some oil out of the front crank shaft seal. It also it depends upon the location of your sump pickup in the case. Also your venting of the sump tank will play a role.

We really haven't seen it to much and by far the FST's come back in from a session with far less oil seepage from the case.

[Garry Sharp]

So when you park overnight and half of your oil tank drains back into the engine up to the pushrod tubes, with only a 20% difference, ALOT of oil remains in the engine oil pan during the race-it doesn't suck it dry immediately after starting That's what I thought was happening because if the oil pan was basically empty while running, there would be almost no leaks.

[rgu]

Gary

I certainly can buy into Jim's theory because its very probable if you are seeing blow by. When you are out on the track there is only about a quart of oil in the case but it can slop around quite a bit.

We have had a couple of things happen that have looked similar to what you describe. The sand seals are not very good. The sealing rubber is very thin. The rubber can come right off the aluminum housing. When it gets chewed up oil can come out which happened last season at Grattan. We had a spare in the trailer and put it in and the problem was solved. Many drivers now eschew sand seals for this reason.

Second, we have seen oil seepage up front that was pretty serious. The engine was a very good one but messy. We sent it back to our engine builder Dave Carr. He ran it on the dyno and found the same thing but could see seepage around the oil pump. He took out the pump and measured the pump body and the pump hole and found way too much clearance. He grooved the pump, installed a o-ring and that problem went away. One of the series drivers had exactly the same problem at the track and was losing a qt every session. He pulled his pump and just put an o-ring on the pump and bolted the pump back in place. Believe it or not it worked just fine.

Both these are worth looking into.

[problemchild]

Gary,
IMO, managing the oil inside the engine is critical for maximizing the performance of the engine. I continued to use a dropped FV-style sump and pickup on my FST engines and had extensive windage control including several dams to keep oil out of the cam gear area. I also had hinged windage panels to let oil into the pickup area but not move out into the pushrod tubes. It was all about keeping oil from the crank assembly .... which means removing as much oil as fast as you can. Evaluating performance of your windage control is very subjective as track forces are not present in dyno-testing.
Cheers!

[Garry Sharp]

Thanks for all the advice, I just wish I knew how to do any of that! I think I will work on the pump sealing first. Alot of oil seems to be dripping from the pump housing. I vent the crankcase twice. Once into the oil tank and once directly into the catch tank. Maybe I'll increase the hose size. Is there any reason you couldn't put a ball valve on the tank outlet to cut off oil drainage back into the engine when parked?

Thanks,
Garry

[problemchild]

Gary, you can reroute your lines to prevent the "drain back". You could also install a valve, but you would need to remember to open it before starting. If your system is not pumping out the sump, as you suggest, you have some problem in your system. While a poorly designed system will operate with more oil in the engine than a well-designed system, it should pump itself mostly dry sitting still. Perhaps your oil pickup tube has fallen out or you have some other physical issue in the scavenge side of the pump. Perhaps you are mistaken about the quantity of oil in the engine when running.

[Garry Sharp]

Like Greg said, I just hope I remember to turn it on. Should help leaking when sitting overnight etc.

Garry

[Bill Bonow]

Garry,

Be sure to safety wire and/or check the safety wire on the valve handle open before going on the track. Something goofs up and that valve closes, your motor is toast!

You could be just fine, but you are the only FST (or any dry sumped racecar I know) that has installed a ball valve in the dry sump suction line. I think it would be much simpler (and safer in regards to the potential for a major engine falure) to put a rag on the floor. Too big of a risk with a minor gain for my liking.

[Garry Sharp]

Yeah, I thought about all that, but decided to give it a shot. I'll do the testing and see what happens. As long as it doesn't leak (I got some high dollar thread sealant) and doesn't close, it should be fine. I am also going to modify the handle so straight DOWN is on.

Thanks,
Garry