diabolical1

Hi All,



I've finally broken in my latest motor and I'm ready to start high RPM use. However, I'm running out of ideas for one major concern. I did many things to it during the building process, one of which was drilling the e-shaft jets a little larger. Now my oil pressure doesn't seem to want to move higher than say 60 to 80 psi (on the stock gauge) in the 4000 to 5000+ RPM range. I am a bit reluctant to run any higher RPM now, just in case the gauge is close to actual pressure. I'm thinking i should be up to 100 psi by then. My idle pressure is still pretty good though - I'd guess 40s to 50s. I've already changed the pressure sender, too.



Here's a run down on my oil mods. The motor is a streetport 12A with a hardened 17.5 mm pump, ported and polished pump passages, REW rear regulator, shimmed front regulator (3 instead of 2), teardrops on the e-shaft, race rotor bearings, 3-window mains and, as I said, I drilled the stock jets on the eccentric shaft.



My question how much do the e-shaft jets affect pressure. From what I gather, my extra shim in the front regualtor should have yielded higher pressure, which is what I wanted to use to offset the ported passages and larger e-shaft jets. At least, that was my thinking ...



Any ideas, anyone?



Thanks.

Lynn E. Hanover

[quote name='diabolical1' date='Feb 17 2007, 01:24 PM' post='859534']

Hi All,



I've finally broken in my latest motor and I'm ready to start high RPM use. However, I'm running out of ideas for one major concern. I did many things to it during the building process, one of which was drilling the e-shaft jets a little larger. Now my oil pressure doesn't seem to want to move higher than say 60 to 80 psi (on the stock gauge) in the 4000 to 5000+ RPM range. I am a bit reluctant to run any higher RPM now, just in case the gauge is close to actual pressure. I'm thinking i should be up to 100 psi by then. My idle pressure is still pretty good though - I'd guess 40s to 50s. I've already changed the pressure sender, too.



Here's a run down on my oil mods. The motor is a streetport 12A with a hardened 17.5 mm pump, ported and polished pump passages, REW rear regulator, shimmed front regulator (3 instead of 2), teardrops on the e-shaft, race rotor bearings, 3-window mains and, as I said, I drilled the stock jets on the eccentric shaft.



My question how much do the e-shaft jets affect pressure. From what I gather, my extra shim in the front regualtor should have yielded higher pressure, which is what I wanted to use to offset the ported passages and larger e-shaft jets. At least, that was my thinking ...



Any ideas, anyone?









I just got back from the shop where I tried to dig my way in, with no success. Ice has filled in around the base of the man door and glued it shut. Same for the overheads, but they only open from inside anyway.



So back to memory, I was going to measure the stock jet opening and compare that to a 200 Weber main jet and a 180 Weber main jet (What I use). Or sombody out there could do it????



Anyway the stock jets with ***** and springs in place, are good for cooling the rotors when the engine is operated at sane RPMs and the stock 71.5 PSI rear relief pressure setting. And nobody here wants to do that,

so we jack up the stock 12A rear iron relief to 100 or 110 PSI and lock out the front temperature relief so it never opens.



So if the oil pressure is well over 100 PSI, then the stock jets are too big and provide a bit too much cooling oil to the rotors, and extra foaming results, as well as reduced oil pressure at idle with the ***** and springs missing.



Let us think about this a bit................



The two notches at the end of the stock jet that stops the ball when centrifugal force lifts the ***** off of the port in the jet well are many times the size of the stock jet and the new racing jet you might want to install.

So the ball cannot interfere with oil flow to the jet...........................



So, the ball and spring can be left in place if you want stock idle oil pressure. The only possible advantage might be to avoid passing a piece of the spring into a rotor or the sump should the spring break. I have never seen one broken, so I would discount that idea.



So, there are a number of oil leaks in the oiling system. Two main bearings, two rotor bearings, the two oil jets, the OMP (very slight) and the spray hole under the thrust bearings.



The OMP and thrust spray are microscopic, so forget them. Look at a 3 thousandths thickness gage and imagine a tube that has a .003" wall thickness and as tall as the main bearings. That is the film of oil you need to supply with pressure at both ends of the crank. Same thing for each rotor, about .0035". If that was it you could live with it. But there is more. The rotor bearings must be fed from this supply as well.



So, those two bearings are in series with the pump not in parallel. So, you see the multipal windows in the bearing face, and that big oil pressure should be available right there at the crank face, so there shoud be plenty of flow for the rotor bearings, right?



WRONG...........



Notice that main bearings seldom fail but rotor bearings do often? More stress, I know.............



Because a bunch of that oil pressure is cancelled by the centrifugal load in the oil gallery into the crank center from the main bearing. And now you think about that a bit and say hey, we get that back in the column going from the crank center to the rotor bearing and then some because of the greater distance from the crank center to the oiling hole in the rotor bearing throw. Right?



Wrong.....................



A few years back the guy who built the first 12A Pport national champ engine kept loosing front rotor bearings on the dyno. So owning this big machine shop, he wanted to know how much pressure was getting to the front rotor bearing.



There is a tough one for you . How would you do it?



They had done the normal things like higher oil pressure all around and bigger bearing clearance on the front rotor bearing, and oiling the front main bearing directly and in parallel with the upper dowel holes and so on the usual stuff.



Still when they were working above 10,000 RPM for any length of time, poof there she goes. No front rotor

bearing.



So, there is a family of rotating flex seals that lubricate rotating shafts like on big presses. They force oil into the shaft through the end. So they drill through the end of the crank and into the oil gallery and with this engine and the rotating front seal they can measure the oil pressure in the center of the crank and calculate the oil pressure at the rotor bearing by adding the gain from crntrifugal force.



And what is the oil pressure in a 12A crank with 100 PSI on the gage? 10 PSI. So we get that back and more from the column going to the rotor bearing, right? Well yes, but the longer arm of that column gives you back more than the 100 PSI and at a much higher flow rate, (because that bearing has more clearance and is much bigger than the main bearing) and whatever foaming is present expands in the lower pressure of the crank center and the drag from the razor sharp drilled corners adds to that problem, then collapses again at the bearing face.



I note here that the **** Gemans have been known to oil high output engines from the center of the front pulley with a similar nose seal system with great result, and you only need 40 or 50 PSI to race on..



So, now the new Mazda engine is running 115 PSI of oil pressure stock, and turning 9,000 RPM with no problems at all and it only took 30 years.



Racing Beat uses about 160 PSI on their 900 HP three rotor airplane engine. Starting to see a pattern here?



And now you have made the two biggest oil leaks in your engine even bigger than stock. And jacked up the relief pressure, so the flow rate to the rotor cooling jets is now really high and is robbing the main bearings of a higher percentage of the available oil. But the number is still too low to be using the engine real hard. They all used to come with 71.5 PSI and would do 8,000 RPM with no damage at all. But 60 PSI is not enough, But 80 PSI is OK.



The oil pressure you read is the rear main bearing pressure.



So, rebuild with smaller than stock jets and leave in the higher oil pressure, or , put in a 8,000 RPM rev limiter chip and just drive it that way. A straight weight racing oil will help with foaming and the engine will probably last forever.



If you have no Weber jets, just braze the stock holes shut and drill the hole to .180 or .200.



Your pump is OK with the ***** and springs out, but for a stock pump you could leave them in.





Lynn E. Hanover





Picture is an aluminum housing with a replaceable wear surface.

diabolical1

Once again, Lynn, you amaze me with your vast knowledge and random memory ... it's pretty cool - at least, to me it is.



Thank you dear sir. I think I'll just *****foot this engine then and not try to see where the revs stop - just my luck, too. I think this is my best in terms of porting and workmanship. However, since the Rx-7 is now a daily driver again, I can't just pull the motor apart again and swap shafts or mess with these jets. I think I'll just put some .180 jets on it whenever I do get to pull it apart again since I can't weld ... yet. It's all good though, it was just a temporary motor swap until I get the chance to port, upgrade and rebuild the 13B it replaced.



I like this part, "And now you have made the two biggest oil leaks in your engine even bigger than stock." Never quite knew to think of it this way, but I guess all that matters is I've learned now.

diabolical1

By the way, I can't be sure about the actual numbers until I get an aftermarket gauge, so I may be reaching 80 psi - stock S3 gauge. It's on the list of things I need to get.

j9fd3s

stupid question; so car and driver tested the rb imsa car and they mention revving the thing to 12,000rpms, this is in 1980, so its dry sump, mfr 12a with the lucas injection.



how did they do it? or were they just saying 12k...

heretic

What you do is calibrate your tach to read a bit too high, so when your competition find out about "how high" you spin the thing, they go and try it too and blow up left and right.



Not that I've ever done this, or anything.



I remember an article where someone tested an IMSA RX-7, and their max revs were "only" 10k, but they were looking into roller bearings so they could get up to 11. This was around 1980-1981.

j9fd3s

yeah i used to have that one too, dave kent, i think

Lynn E. Hanover

When there is no rules restriction on the intake side then there is power available at the higher revs. This is mostly drag racing stuff and more recent. There were few carbon fiber drive shafts available back then, and with your top gear turning the drive shaft the same RPM as the engine, the drive line takes on a life of its own, and that life tends to be short and unhappy. So then you get away from the aluminum quick change rear ends and go back the the very stable but heavy iron Ford 9 inch. Same as NASCAR.



The most I have heard of is 10,700 for sprint racing and 10,300 for long distance racing. If Racing Beat said they used 12,000 RPM for road racing, then they probably did. But us earthbound racers cannot rebuild an engine after every weekend. Those engine have very light rotors with short lives. (they crack).



My personal best was just under 16,000 RPM. The driver was coming down the hill at Road Atlanta when he selected 1st gear while trying to select 3rd gear. The Hewland went right into gear of course, and it was a clutchless downshift, pitching the car sideways, and alerting the driver that an error had been made.



The Smiths Chronometric tach had numbers only to 10,000 RPM and that number was at the one oclock position on the face. The tattletale needle was stuck against the back side of the start post at the six oclock position. The engine was damaged but kept running. Another pickle bucket rebuild and we raced the next day.



Lynn E. Hanover

Lynn E. Hanover

You simply must learn to weld and braze. Then TIG and MIG.



My mother was a welder at Curtis Wright here in Columbus during the war, and welded aluminum with a gas torch and blue glasses.



I was 25 before I laid down a weld bead she approved of.



Lynn E. Hanover





Picture is an Emco 5 speed and half shaft ends from a Daytona Prototype after 24 hours at Daytona.

rotaryinspired

Lynn,



Where did you find someone to manufacture the irons like the one shown above. Thank you.

Brad