IT Rotary Engines

[Ron Earp]

I was looking through the GCR, specifically the ITCS ITS section, and noted that there is no hard data on the RX7 13B motor with respect to critical power producing specifications – mainly port sizes. Piston engines listed in the ITCS have the majority of the key specifications listed and, for the most part, some of them can be fairly accurately checked at the track with a micrometer or even a good measuring rule. Valve diameter along with bore/stroke are easily checked and with a few more simple tools the compression ratio can be measured. But with a GCR in hand there are no specifications on a rotary engine that can be evaluated.

In the paddock I have heard it rumored that there is no definite port size on the 13B rotary engine and thus a specification in the ITCS cannot be listed. I might certainly believe that some castings have a more desirable specification but then the dimensions of this particular port should be stated since it would be the maximum size. As it stands there is no way to inspect a 13B at the track unless you have a factory casting from Mazda. And even then there would be suspicion cast upon the bearer of the factory part that might nullify an inspection result.

If it is indeed true that there is no factory specified port sizes on the rotary engines then we’ve got a problem as the cars won't have confining specifications on a critical aspect of the motor.

If there is a factory specified port size it would seem to me that we might want to get some port size dimensions put into the GCR in the form of text, or if some sort of irregular shape, an engineering drawing of the port(s).

[GKR_17]

What is needed are 'lollipops'. The SE div had a set for the 12a a while back, don't know if they're still in use.

We have a set for the 13b, but the stewards would not even look at them when they were provided in a protest (at the ARRC). In that case they only allowed visual inspection of the ports, just how much is that worth?

Where no specs are available, the GCR requires the club to determine the allowable specs. That should clearly apply here.

[GKR_17]

On another note... the ITCS allows the rotary to be bored .040 over. Clearly that's ridiculous, but I got a lot of rolled eyes when I suggested it be fixed.

[Jeremy Billiel]

Unforunately guys who run the 13B have been running with no fear or any inforcement for years.

[JeffYoung]

Not true down here. One legal RX7 has managed to keep the others in line, and that is much appreciated.

Just checked -- the 89-91 motors (the S5 that I think everyone runs) has exhaust baffles that prevent use of the lollipop.

[GKR_17]

Just checked -- the 89-91 motors (the S5 that I think everyone runs) has exhaust baffles that prevent use of the lollipop.

That depends on how the lollipop is made. As I said, we have a set (made from castings with the baffle).

[JeffYoung]

We were told there was no way to "lollipop" the 13b. Don't remember why, but that was the word. You physically have to take it apart and compare what is in the protested car to a stock housing.

Mr. Eckerich has a new in the box sealed up rotor housing. I think we just take a measurement, get it confirmed, and ask that it be added to the notes/spec line on the 13b.

What is needed are 'lollipops'. The SE div had a set for the 12a a while back, don't know if they're still in use.

We have a set for the 13b, but the stewards would not even look at them when they were provided in a protest (at the ARRC). In that case they only allowed visual inspection of the ports, just how much is that worth?

Where no specs are available, the GCR requires the club to determine the allowable specs. That should clearly apply here.

[Ron Earp]

We have a set for the 13b, but the stewards would not even look at them when they were provided in a protest (at the ARRC). In that case they only allowed visual inspection of the ports, just how much is that worth?
.

Doesn't surprise me that the tech folk wouldn't want to use lollipops that you provided. Or a stock rotor housing. That's the core of the problem - only the party competing against the rotary that is torn down is interesting in having stock parts or lollipops. But, those items would be ignored in a protest due to conflict of interest.

Visual inspection - not much use. The ITCS says:

2. Rotary engines (only)
a. Any porting or polishing is prohibited.

But in this day and age it wouldn't be too hard to port and make it look like it was never touched, at least for a visual inspection.


From the ITCS on specs:

Where factory specifications are absent or unclear, e.g., cylinder head thickness and/or combustion chamber depth, etc., the Club may establish an acceptable dimension and/or allowable tolerance from stock.

With my inline six I can probably have the head off, displacement, valve size, and a rough compression check completed in under three hours. Seems it should be possible to perform similar performance checks on a rotary engine.

[JeffYoung]

And, apparently, one cheat is to use a Turbo rotary housing which is bigger, but looks stock and not ported.

The answer to this one is simple guys. We get a 13b housing new in the box, measure it and provide the specs.

[lateapex911]

The answer isn't that simple.
Jeff, "we" can't do that...nor can Steve provide the part..conflict of interests arise in both conditions.

In a protest of a piston engine, even if the GCR says 30mm valve size, the protestee can appeal and say it's wrong, and the GCR very well may be, and the protest will be overturned when the research concludes the listed size is a mistake or typo or whatever. Shop manuals at the track will override the GCR, or cause enough doubt as to cause the Protest stewards to not render a decision at the track.

Your "issue" appears to be a matter of timing. In a 13B teardown (12A too), the part is confiscated, and a stock one is procured by the Stewards from Mazda, and compared to the part in question. I'm assuming that you don't like the lag time involved, because rotaries CAN be protested in this manner just as any piston engine can. Remember, the port is akin to a cam, and cams go out for measuring against stock examples that independent parties (SCCA Stewards) procure when a cam is protested.
(An intake port is located on the sideplate and looks like a liver shaped swimming pool, kinda. It's not as simple as measuring a circle. Lollipops are for exhaust only, and don't measure all the parameters of the port anyway)

Now, SCCA DOES have certain cam profiles on file, so there are some cases where it's easier and quicker than having to get the part and then measure it.

You COULD request that:
- SCCA Tech purchase a stock 13B side plate and housing and maintain them in stock for future protests. SCCA might be willing to pay, or Mazda might be willing to donate.
- You could convince your regions tech staff to do the same. Funding is an issue.
-Or, you could arrange for the Regions tech staff to procure the part, and then pay an independent lab (one with no POSSIBLE conflict of interest) to measure the shape via CAD and store the profile in the Regions files. Once you have the measurements (and it's not just a 2D measurement either) you can return the part and disseminate copies of the data easily and quickly. Now, measuring a protested piece would need to be accomplished by an independent firm having the proper tools, or by the Regions staff if they had the proper tools.

No matter what, i think, rotary teardowns aren't trivial, and you just have to ignore the seemingly obtuse aspects and forge ahead.

[JeffYoung]

With all due respect, I think it is, and has to be, much simpler than that. Ron's cite to the GCR gives us the answer. We get a 13b housing (the suckers are not cheap though, $650 each front and rear from Mazdatrix), measure the ports and add that to the spec line. Or SCCA does.

And t I'm not sure why SCCA Tech has to do that. We (on the ITAC) "determine" valve sizes, compression, etc. via internet searching.

I also think you are missing the point. We just want a spec for the ports on a 13b in the GCR for future reference. So no one has to haul stock 13b housings to the track for a protest. It is honestly pretty silly, and at least to this guy unecessary, that a rotary has to be torn down to check port sizes.

[Ron Earp]

The answer isn't that simple.
Jeff, "we" can't do that...

Well then we need to find a "we" that can.

Jake, none of what you write or suggests concludes with specs getting into the GCR. The goal here is to get specifications into the GCR.

As far as the cam analogy it is, as I am certain you know, a bit more complicated. The port size provides the "cam lift" and the port size provides the "valve diameter". So, suggesting a housing is like a cam and therefore has to be sent to Topeka for inspection doesn't quite hold water.

Port specifications should be in the GCR. Else I'll go to work on getting my 260z specs out of the GCR so that you rotary guys have to haul a head around to tear me down. You don't want that. Those heads are heavy. :-)

[mbuskuhl]

We get a 13b housing (the suckers are not cheap though, $650 each front and rear from Mazdatrix), measure the ports and add that to the spec line. Or SCCA does.

Those are the rotor housings, you'll need the side and center irons as well for the intake ports.

And, apparently, one cheat is to use a Turbo rotary housing which is bigger, but looks stock and not ported.

The turbo rotor housing does not have an exhaust diffuser like the NA rotor housing. Simply pull the header and look for the diffuser.