flyrotary@lancaironline.net Mailing List Archive

Lynn,

If you have a picture of the Mistral modification that would be good.

I don't need the info on modifying the pump, however your trumpet end on the pick-up tube is a good idea, perhaps a bigger plate and screen would be a good idea, as well as the baffle.

Tell me does the FD have twin inlets for the oil pump, I seem to remember something like that OR it could be something Mistral made up? Perhaps they used the FD housing?

George (down under)

I'm with you on that memory thing, sadly my memory has never been that good to start with.

I digress - again. I spoke to Gordon at Mistral and they felt that the pick-up was causing a vortex, pulling in air, that would account for foaming.

Certainly a possibility. That flat plate that the screen attaches to, has two jobs. Hold up the screen and increases the distance from the tube opening to the surface of the oil in the pan. This is called by some: the vortex plate. Some are quite big in racing and seldom have a bug screen attached. The Mazda engines have always had dismally small vortex plates and shamefully little bug screen area. The suction tubes are too small and no effort is made to smooth the edges of the tube opening. I brazed on a giant thick flat washer to the end of that tube and used a die grinder to produce a big radius into the tube end. Like a small trumpet bell. The oil velocity at the edge of the big washer is much lower than at the edge of the bare tube, so the washer alone cures the vortex problem.

I replaced the vortex screen with one from a Pontiac. Real big. Never a problem. That vortex problem goes South real quick if some foam gets into the oil. So the bigger plate, or since racers use a baffle to keep the oil in the pan, the baffle serves as the vortex plate. I ran the oil level about 1/4" above that baffle.

I can't quite remember but didn't they use a 2 tube arrangement, you mention feeding the rear rotor?

They made up a real nice cover and pickup. I had a picture a couple of computers back. If it is on a memory stick I will post it. It was a long way to go, but it did the trick.

Question what is the FD twin turbo?

The first model was the FA the second model was the FC and the last US model 93-95 was the twin turbo FD.

Body styles I think.

I didn't know about the flat screen in the baffle plate, I just thought it was a bigger screen, I don't know why I thought that.

Why was Mistral having these problems, they weren't running the engines hard or expecting too high HP from them.

I don't know if they started out with a full baffle or not. With the oil level just a hair below the baffle, oil from the rotors (falls out of the center iron drain-back hole) lands on the baffle and gets a few seconds to dump off some foam bubbles. Even with racing oil and the baffle, there will be some foaming. So you might see the peak oil pressure drop off about 6 to 8 pounds. Not a problem. Just normal. The stock pump is just a bit small in displacement. Stock pressure until the FD came along was 71.9 pounds. So, 55 to 71.9 pounds is fine from an early engine. I like 85 from the stock pump, but you have to screw with it too much to get it.

I can detail that if you want.

The FD relief valve is set at 115 pounds.

When the driver sprang for a real race engine $14,000.00 it had a Peterson 3 stage dry sump pump mounted on it, so we used those for a while. The square ones split open the pressure section, so I bought a Moroso dry sump pump. Works great. Tall skinny reserve tank takes out the foam. Pump is externally adjustable. Set at 100 pounds. Idle at 2,200 RPM it has 80 pounds. At 3,000 RPM 100 pounds.

Speaking of baffles, in the racer, the entire oil supply will fit in the front cover under hard braking. The baffle eliminates this. So think about that when doing stalls and such. Less so with the full width mounting plate. The only 2 gages in the drivers line of sight are the tach and oil pressure.

Cars don't cruise at 6,000 RPM. Cars don't use multi grade aviation 50 weight oil. So, in a car (or airplane with the right oil) there is no problem. Once the oil is foamed and starts to overheat (air in the oil is an insulator) so the coolers quit working, and the oil quits cooling the things oil is supposed to cool. A little air gets that vortex thing started. Very bad mojo. Never leave the pattern bad mojo.

We should remember that very available non synthetic racing oils have extra anti-scuff zink compounds,

and anti foaming additives. A straight weight racing oil (No polymer strings) burns clean enough for rotary use. If you get all of your top oil as a premix, you can use a 40 wt. synthetic racing oil in the sump, and get the anti scuff, the anti foam and astounding film strength. Or you could install one of Richard Sohn's gizmos and run a synthetic racing oil in the sump, and an ash free 2 cycle top oil through the OMP. No premixing at all.

Tracy sells them for Sohn.

I would premix just a bit anyway. The later OMP lines favored the apex seals and not the side seals.

Why is it no one else is having these problems OR should they be anticipating problems.

Well we all have to on guard for the Spanish inquisition, and Obama, but mostly, it's because everyone reads this forum, and that other one, and knows that at least 1/3 of the total cooling required is going to be oil cooling. Start off with too much cooling and add additional cooling from there.

Lots of this data is in Racing Beats catalogue. Available for free down load from their web site.

You can download the Mazda Competition manual from the "Nopistons" web site for free. Lots of good stuff there about computer maps. Dyno passes. Water injection and so-on.

George (down under)

There you go.

Lynn E. Hanover