IT Rotary Engines

[lateapex911]

The problem I see is that without some specs that are recognized in the GCR RX7 protests are paper tigers.

Ron, with due respect, no they are not "paper tigers". They just need to be done through the proper channels. Get stock housings through independent sources (Mazda -> stewards) and you're good to go. Heck if timing is an issue, contact the Steward before the race, provide the $ and have them ordered early and in the stewards possession. Once used, return them, net cost will be the restocking charge, and I'd bet Mazdaspeed would waive that.

If I'm a rotary guy, and i get protested, I know I'm legal, but if somebody says, "Hey, this lollipop doesn't agree," I'm going to want the paper trail, and it better not start at a competitors 'stock part". Even if the stock part is 1000% legal, the deal is going to smell. So, if you're going to do a lollipop, make sure the process is 100% above board and completely neutral. In other words, Stewards buy the part, Stewards get teh measuring/machining/molding etc done, and Stewards stamp the part and maintain the inventory. If a competitor holds/supplies it, it is worthless. It has to be.


I agreet that trying to quantify the part is critical, but again, the GCR isn't the absolute last word. it can be wrong. Beyond that, how are you going to put 3D CAD specs in it?

[C. Ludwig]

The intake and exhaust ports are defined in terms of crankshaft position. This is the most precise way to define the port and any scrutineering should be based on this approach. More on this later. One glaring example of why a simple lollipop would not work is the, already mentioned, 87-91 turbo center iron. The overall size and shape of the turbo primary port (the port present in the center iron) is essentially the same as that of the NA center iron. However, the entire port is shifted toward the closing line without a change to the opening line. What you end up with is a port that is essentially the same "size" but provides a 10* later closing and 10* more duration. Externally, the turbo iron is indistinguishable from the 89-92 NA iron. A lollipop would likely pass the turbo iron.

IMO, a lollipop would fail to tell the whole story of the exhaust port as well. To begin with, the exhaust port of the NA and turbo rotor housings is the same dimensionally. The only difference between the two in regard to this discussion is the diffuser that was added to the NA engine from the factory to help quiet them down. Pic below.



This is obviously a pic of the internal side of the port. The external side of the port is much larger than the internal. Think of the runner as a megaphone. In the first place, the port size and timing of the stock exhaust port is very good for an IT engine. Not much is going to be gained from exhaust porting, or the removal of the diffuser sleeve. Secondly, if someone wanted, they could easily make handy modifications to the stock bevel around the exhaust port to encourage it to breath while still retaining the basic shape and satisfying a lollipop test. Again, the port is described by Mazda in terms of crankshaft angle, and that would be the best way to scrutineer the engine.

At the end of the day, it's extremely easy to tell if an engine has been ported on the intake side. The primary and secondary runners are all rough cast. Any tooling of this cast surface is very obvious when the intake manifold is removed. The photo that Jake provided above shows a common street port. The closing edge of the port simply can't be modified without it being pretty obvious to the naked eye when the intake manifold is removed. No bore scope needed, just a flashlight and a keen eye. The open line (the part of the port shaded in blue in Jake's pic) could be manipulated, but it would be very hard to get that past a trained eye. The ports are rough cast by Mazda and then the final shape of the port is cut with a CNC process. The mill leaves a very clean mark all the way around the circumference of the port. I'll go out on a limb and say it's impossible to replicate this milling by hand and fool a trained eye. It's also impossible to recreate this line with a CNC mill and alter the port dimensions by any great degree without disturbing the rough casting. Again, the opening line of the port could be moved back (opening the port sooner and creating greater duration) but it would be very difficult to replicate the accuracy of the CNC cut by hand. It could be done but it would be real tough.

The aux secondary port (sometimes referred to as the 5th and 6th ports) are smooth bored from the factory for fitment of the aux port valves which are typically, legally removed as part of an IT build. The actual port dimensions of the aux secondary ports are already very radical in terms of timing in regard to crankshaft location. There isn't anything that's going to be gained from going bigger on these ports.

What are the port dimensions?

Primary port (center iron) opens at 32* ATDC and closes at 40* ABDC
Secondary port opens at 32* ATDC and closes at 30* ABDC
Aux Secondary port opens at 48* ATDC and closes at 80* ABDC

IMO, what you guys need in the paddock is a trained eye. There are cheater engines out there. And you'd never believe how easy it would be to catch them with the naked eye.

I have damaged stock housings you guys can have to measure to your hearts content if someone will pay shipping and handling.

[Ron Earp]

Ron, with due respect, no they are not "paper tigers". They just need to be done through the proper channels.

Well, as one who just went through this process I have some data that suggests that they are indeed paper tigers of a sort.

IT is grassroots amateur racing. Not semi-pro, little league, or anything like that, but pure fun amateur sport. Along those lines there should be a way to check some basic specifications of a rotary engine without resorting to master templates locked in a vault and what not.

You and I go race. You go eight seconds a lap faster than you went last month and set a new track record. I decide to protest you, the tech guys set the bond, I pay it, and your car gets pulled down in the tech shed by Joe Average SCCA Technical crew.

If you have a piston engine the tech guys can determine a fair amount about your engine:

• With a dial indicator, a tool I have in my trailer, we can determine cam lift to a reasonable accuracy.
• With a caliper, another tool I have in my trailer we can very accurately measure displacement.
• With the same caliper we can very accurately measure valve sizes.
• And, in some regions a buret, dye, plate, and grease are available that would allow us to determine compression to a reasonable degree (probably to within a couple of tenths which isn't bad for trackside work and will catch gross levels of cheating).

But, if you are running a rotary engine one of two of things might happen:

1. If the engine is torn down in tech at the track what are the tech guys going to look at? This protest wasn't planned ahead, so no factory sealed parts from Mazda are on hand, and if they were they might not even be accepted by tech due to conflict of interest. There are no specs in the GCR, nothing to measure. Tech guys eyeball some ports, some expert says looks factory or doesn't look factory, and there you go.
2. The teardown bond is set high because the engine has to be sent off for inspection. Protest doesn't go occur because the protester(s) can't afford the bond.

The way things are a rotary engine can be a cheaters paradise. Fortunately cheating isn't rampant in IT but it'll be damn hard to identify illegal rotary engines unless you've planned way ahead and gotten the right people to the track at the right time.

[lateapex911]

Ron, one thing I learned, assume nothing...
When we did our protest, the techs couldn't measure compression*, but noted that the head hadn't been cut, so therefore, it must've been "OK". So that part of the protest was denied, and the guy was deemed legal. (last minute outside of the Protest committee stewarding saved the day, but...)

So, I had assumed they would be able to do some basic stuff, but it wasn't so basic. yea, it would be NICE to be able to show up and get answers, but, I've found prepping far in advance (like racing) yields the best result....even when things seem simple.

*This was a result of tech not having the proper tools...tools that we had. And word got out that the techs were looking for them, and we offered ours. Denied of course, conflict of interest. Our suggested neutral sources, for facilities and tools, also denied.

In your scenario, #1 should never happen, for the reasons you illustrate.
#2, teardown bond shouldn't increase that much for an offsite inspection. The engine still needs to come out and be torn down. (In reading your comments about your recent protest, I've inferred the bond was very very high, and that seems not quite right to me). Huge bonds will occur in many cases, of course. (tear into a Porsche 911 to weigh the crank? Ugg) It sounds like this one was out of line, but, that's a hunch on my part, and don't quote me on it!

I think the issues you have are not unique to the rotary, but will come up in any number of protests. It's a balance in the system....maybe not the right balance, but it tries to protect against vexatious actions and ensure legitimacy. But it also makes the hurdles very high.

[Andy Bettencourt]

Ron, (example)

You have uber-light forged pistons in your Z. I write a good protest asking for displacement, compression, cams and piston compliance - all checked.

Please tell me how much easier it will be to validate all that on your car (or Jeff's) than it would be to do this:

Have a stock set or rotor housings to compare to on hand. You and the PC compare. If a reasonable difference is spotted, you go through with the protest by sending the motor wherever and having them procure the neccessary parts to validate what you think you know based on what you have seen.

If you see no difference, you conceed and pay for the labor and parts to get back to running condition.

I see that as SOOO much easier than trying to validate specs on a 35 year old car, no?

Rotories, easy to cheat - easy to catch - if you know what you are looking for like Chris said. Piston engines, just as easy to cheat - crazy hard to validate specs on out of production components and limited documentation.

[GKR_17]

Don't forget the oil system...

I've not built a wankel, but did stumble on to the info that the ceramic seals likely need higher than stock oil pressures to work right.

[lateapex911]

But seals are free right?

[Andy Bettencourt]

Don't forget the oil system...

I've not built a wankel, but did stumble on to the info that the ceramic seals likely need higher than stock oil pressures to work right.

Oil pumps (pickups) and rotor seals are free.

[seckerich]

The rotary is no different than any motor on port work, however we can not touch anything where everyone else gets to port match. . They have to match the stock part --period. The Turbo housing has a different casting ID and is easy to spot without teardown. If you do not agree with the outcome of the protest at the track you can appeal the decision and have the parts held as evidence for the appeal and shipped to an expert. Not the big hole you make it out to be. And for the record I had new, sealed parts shipped from Mazda per the request of my chief of tech at CMP because he was told to expect a teardown of a second gen RX7. If you plan to protest a car call the chief of tech for the race and give them a chance to prepare to tear down the car properly. All us rotary guys are cheating bastards, just ask Grafton. He has the plugs to prove it. Have you had RX8 plugs made yet?

[Ron Earp]

Hey Chris,

Thanks for the pictures and post on the rotary and the offer on the housings. I've never disassembled one of the engines but have always been intrigued by them.

Fortunately cheating isn't rampant in IT.

The good thing is I feel that the sentence I wrote is true, at least in the areas where I race. Due to the efforts of folks like Steve E in the SE the rotary engines are policed pretty well and I do not think there are wide spread problems. However, not all regions are fortunate enough to have someone like Mr. Eckerich

You have uber-light forged pistons in your Z. I write a good protest asking for displacement, compression, cams and piston compliance - all checked.

Please tell me how much easier it will be to validate all that on your car (or Jeff's).

Andy, if we were to use my car for an example of the 35 year old car, you find that you'll will have absolutely no trouble validating specs for the cam (lift 7mm IN, 7.35 EX, etc.), compression (9.30 max), displacement (3.310" x 3.110", 2630cc max), and valve size (1.65" IN, 1.38" EX). In the shop manual those specifications are written in black and white and, for the convenience of US customers the specs are in millimeters and inches. With the exception of cam duration all the specifications can be fairly easily measured with tools most of us have at the track. Jeff's car is the same and even a little bit easier.

I think using these specifications is more straightforward than pulling a motor apart and judging if something is "stock as cast" or "not stock as cast". And then if the tech fellow (who we hope is a trained eye with rotaries cause if he isn't then it won't be easy for him to determine what is what) decides it is "non-compliant" we need to send it off to someone else (maybe, in your example we do so I'm sticking with that), a rotary engine expert, for a second opinion. With my engine, and others like it, if I'm running a 2.8L 280z motor I'll be found non-compliant at track, easy. Huge cam? Non-compliant at track. 10.8:1 compression? Non-compliant at track. The difference is with my engine an average fellow even casually interested in engines can check some critical parameters with simple hand tools - no previous experience needed. I show up in a Jensen Healey and the tech guy, having never seen one of the evil spawn of the devil engines before, can check the aforementioned items.

My initial reason for starting this thread wasn't to point out a specific protest action or find fault with any person or group. I simply wanted to try and get a consensus regarding getting even some basic rotary specifications in the GCR for future reference. The scientist in me likes numbers and things I can measure. However, it appears to me more folks are interested in explaining why we can't do that, or should do that, than suggesting ways we can do it, even if it is a simplistic first effort. I understand that it is a complicated problem. But, with the sort of talent we have amongst us almost surely solvable if it is something that the group feels is a real issue, which I gather most do not. And I'm okay with that as you folks have been at this far longer than I have.

[Andy Bettencourt]

I know your goals Ron. My point is that it's just as hard to prove your pistons weigh the right amount as it is to prove castings on a rotory. Both involve significant invasion, bith have no spec, both require a stock part to compare to.

You can buy new rotor housings from Mazda. Can you buy new OEM pistons from Nissan?

My overall point is that paper tigers exsist for all cars unless you go all the way.

[Ron Earp]

I know your goals Ron. My point is that it's just as hard to prove your pistons weigh the right amount as it is to prove castings on a rotory. Both involve significant invasion, bith have no spec, both require a stock part to compare to.

However, one modification has extremely minor performance ramifications while the other is quite considerable. Having pistons that weigh 65g less than stock probably won't show up on the dyno and offers a minimal performance advantage on track. Having a port that is slightly enlarged will show up on track and the dyno. The major aspects of a piston engine that enhance performance are easily determined by just about anyone.

I'm certainly not going to take the position that some do explaining that if it is too easy to cheat with a car then we either can't have it racing or have to place additional rules and regulations on the car. That disingenuous argument was used by some against having V8 cars in IT classes. It appears to me there is enough regulation on the rotary engines based on the fact that ports must be used as cast and no porting of any type is allowed. I just don't think that "no porting of any type" is going to be that easy to determine at the track and is relatively ambiguous for the untrained volunteer.

I do understand that the rotary engine ports are complicated. However, I do feel even having a rudimentary outside surface dimension with locations in the ITCS in the form of an engineering drawing would be helpful for racers and tech volunteers. I think it'd be an improvement, however minor.

You can buy new rotor housings from Mazda. Can you buy new OEM pistons from Nissan?

My overall point is that paper tigers exsist for all cars unless you go all the way.

Yes, new pistons are available straight from Nissan. Our man Riley at Lynchburg Nissan has been watching out for us and stockpiled lots of Z pistons. I use them and I think most L series racers do because they are high quality. Aftermarket pistons are available which are identical and are probably made by the same factory sans logo. However, for the extra ~$4 each I use the factory pieces.

[Andy Bettencourt]

I have always felt that we should build a template that slides on the header studs that shows the profile of the exhaust ports. Can detect everything but is a nice initial peak.

Also, knowing what RX-8 rotors look like vs. RX-7 ones is a good idea too. RX-8 versions have higher compression.

[JeffYoung]

This has been a helpful discussion. I do agree with Andy et. al. that there are some areas on a piston engine car that are hard to establish compliance for.

Ron's basic point to me does seem valid though. Port size is a basic power definig characteristic of a a rotary motor. I don't see any harm (and if you rotary guys disagree, let me know, I'm certainly no expert) in getting basic specs for the port sizes in the ITCS.

Greg, Steve, Andy, Jake have convinced me that certainly is not the end all be all, and may not matter much, but it is a start.

[Andy Bettencourt]

Port size AND SHAPE are the basic power defining characteristic of a a rotary motor.

Fixed.

[Greg Amy]

Fixed.

Agreed. If you can get a basic port shape, located relative to the exhaust studs as Andy suggested*, then I think that would be a good basic go/no go gauge that Tech can keep around for a quick check (remove exhaust manifold, stick in port, go/no go). Something like that would be relatively easy to fabricate.

GA

* If someone were really industrious and wanted to change the "cam timing" of the engine, they could also relocate the exhaust studs (though they could do the same thing inside as well). However, if someone is willing to go to that extent to cheat, well, then that's kinda like the Smokey Yunick 7/8 car and I think they deserve the "pass"...

[JeffYoung]

Agreed x2. We are getting some stock housings from Chrs L. We'll measure and make some plugs, and locate them using the studs to (try, anyway) avoid the problem Greg mentions.

This may go nowhere but it is worth a shot in my view.

Steve E. -- any thoughts on this? You have been an invaluable resource here on how these motors should be built legally. Much appreciated.

[lateapex911]

So, this is for the exhaust?? Didn't Steve say the intake was where the performance payoff is? Or I think that was Chris. Either way, that's where I've always understood the real power gains to be.

Since Steve got (and wisely shipped them to the Steward) the plates, why not make templates of those openings? Reference your templates to the water jacket openings. (Make sure a Steward is present as a witness through the process to insure the conflict of interest issues can not arise. See also: OJ Simpson trial)

Once you have those, you can structure your protest in a staged manner, and using the template would net the obvious easy to spot changed opening cheats, saving the more thorough and expensive steps.

Bottom line to me though is, you guys want to nail the easy power cheats. Those are in the intake ports. Any real protest would involve a teardown to get and prove wrong doing, even with the template.*

* I think the visual intake manifold off inspections CAN yield obvious signs of tampering, and if it aint stock, it aint legal, so there is that as a first step, but it's not a 100% conclusive step.

[Ron Earp]

why not make templates of those openings? Reference your templates to the water jacket openings. (Make sure a Steward is present as a witness through the process to insure the conflict of interest issues can not arise. See also: OJ Simpson trial)

We should obtain said drawings via Mazda and avoid the "chain of custody" issue. Anyone have a contact at Mazda we could start with?

R

[seckerich]

Let me be real clear going forward. You will not tell if a rotary is cheated up unless you take it apart. Unless they are a total moron and grind the ports all the way. I hear these thoughts that a little bit goes a long way, it does not. It takes some serious porting to get where we do on the EP motors. All housings from mazda for the entire time the 86-91 6 port motors in ITS were made they were CNC cut on the intake openings. They are the same and are easily seen with something as simple as a paper tracing of a stock port laid on top. All the plugs in the world will not help because there in no access from the outside and the only port you could check has an inconel insert that blocks most of the opening. Nothing you put on exhaust studs will tell you anything. Do your homework before you post misleading statements.

If you want a true template then you need a cnc cut overlay of the side housings that locates on the 2 factory dowels and it will bust anyone that is changing or moving the port. I put stock housings on my CMM and reverse digitized them to get the basis for my ported EP stuff. A simple template .050 thick would do for any tech crew and cost about $50. I have checked more than I care to admit looking for the best and they are almost identical on the surface. Core shift in casting makes some flow better but that is the same with any cast piece. AKA flowing 20 SM heads to get the best. Mazda will not release prints.

You are getting a little carried away because of BS statements by those with the least knowledge about rotarys.