$2013 Rotary Miata

In reply to Ashyukun:

Great info, thanks Ashyukun!

This project is on hold for a few weeks - I got sidetracked by getting my $2010 GTX running and registered, and then promptly threw my back out. >< Will post again once I've recovered!

wvumtnbkr wrote: S5 stock EFI system will put the car into limp mode without the OMP connected. Some people just wire it to the fender and leave it electrically connected when they run pre-mix. Rob R.

Ran into that with the Jensenator. I wanted to run an OMP, just not the electronic one, so I used an S4 front cover and mechanical OMP, then used an S4 ECU. S4 and S5 share everything sensor-wise except the air flow meter but the S5 AFM can be wired to work with the S4 ECU, that's what is on my car right now and it works fine.

BTW, the S5 limp mode is two fold: it switches the fuel pump relay to run the power supply through a resistor, slowing down the pump thus lowering the fuel pressure. It also cuts off the trailing ignition. The resistor for the fuel pump is also used during hot soak restarts to make it less likely to flood, the S5 ECU handles that internally but the S4 does not. That setup can be reproduced with a 20 PSI oil pressure switch; wire it so the relay for full voltage is activated by the switch, that way until the oil pressure hits 20 PSI the pump runs through the resistor.

RX7 part out CL ad is here, btw: http://sfbay.craigslist.org/sby/pts/3705900757.html

(Edit: Discounts available to GRMers, of course)

Back is feeling better, but I'm going to rest through this weekend before starting back up.

Glad to hear your back is better.

I'm going to be in San Fran in a month or so for training. Try to have it running by then, I want to see it.

In reply to Brett_Murphy:

Ooooh. You don't need sleep while you're training - you can just wander on down and help me piece this thing together. I'll wait!

Let me know when you're out this way and swing by for a beer. :D

Well then. There's nothing like waiting until the absolute last minute to start really working on things. Just now getting back to the rotary Miata. Yeeeeah. This may yet be the 2014 Rotary Miata.

When last I left the transmissions, I was trying to get the dampener off the RX7 shaft to fit the Miata transmission tail over it in order to bolt the transmission up to the Miata power plant frame. That proved...not so easy. So, I decided instead to swap the bell housings.

And now, I hit problem number one:

While the shaft overall is the same length, the tips are different. Searching around the intarwebz, I came across this awesome post from mazdatrix: http://www.mazdatrix.com/faq/miatainputshaft.htm

Since the tip slides into a bearing sleeve, does it actually...do anything? I stuck my finger in there and it seems to move freely and doesn't seem to be connected to anything.

The mazdatrix guys grind down the Miata spline. I was thinking of ghetto-grinding it, and my buddy Jeremy suggested maybe we can just chop the tip off. I'm all for it, myself. He's worried there's actually a reason to leave the tip there. Peanut gallery?

I am morally opposed to chopping the tip off anyone's shaft.

In reply to SVreX:

You are no help, sir. :P

Jeremy will keep his tip and shaft (he has yet to share that with me, sadly), but the Miata transmission's tip and shaft are chopping-block bound unless I hear an excellent reason NOT to do it. :D

I was trying to help the poor slob whose shaft tip you were trying to hack off!!

I see no reason you can't cut it.

I would try to avoid heat. Grinding might loose temper.

Either cut it, and clean it up with light grinding, or grind very slowly and keep it cool.

In reply to SVreX:

You are so good to Jeremy. And to me. :D I know what I'm doing for my Sunday morning!

I thought some of the bearing diameters in the case are a little different as well. You might want to check that out before you grind or cut.

Rob R.

Isn't there a pilot bearing that that tip slides into? (Giggity). With out that support the shaft will probably flop around when the clutch is in and cause problems.

In reply to bgkast:

You are correct, a friend educated me on that Saturday. Ended up dropping the front end and replacing the subframe with the tubular one from V8 Roadsters (I have more money than time at the moment). Still in budget, but may bump me out of the sub-$1k category, which makes me a little sad, but not really.

So we pulled the bell housing and started measuring things. I think the easiest thing to do right now is to either remove the dampener from the RX7 tranny so the Miata tail bolts onto it (which is proving neigh impossible), or swap the shafts (still likely using the RX7 guts, mostly because it looks like it's been recently rebuilt). Does the input shaft run straight through, or are they two different shafts? (I'll find out tomorrow night when I completely take one or the other of them apart...)

Hold up... gimme a sec.....

http://grassrootsmotorsports.com/forum/build-projects-and-project-cars/swapped-91-mazda-miata/72815/page1/

Talk to this guy. He knows his E36 M3. I've seen it in person (he lives about 10min from me.)

Just swap the tail part of the casing, technically you can swap all the guts over/ mix and match since there all "M Type" trans. The maita gearing is nicer than the fc stuff. the damper on the fc guts should be able to just be sectioned off if need be. I should have photos of what mine looked like inside. info on gear ratios and other good stuff. http://www.solomiata.com/Drivetrain.html More good info

In reply to rewedmiata:

I tried to swap the tails and failed - the Miata tail casing doesn't fit over the RX7 dampener, and I have not been able to get that berkeleying thing off.

I checked my factory service manual for this dampener. It does not mention anything about removing it. I would think it has to come off because the factory tools for rebuilding the trans would not work with it on.

Have you tried loosing the large nut (it may be reverse thread)? You should be able to do that by putting the trans in two gears at the same time.

Rob R.

yup I got that part, just cut it off.

In reply to rewedmiata:

I don't have the tools to cut off the dampener.

@wvumtnbkr Haven't tried it by putting it in two gears...will give that a try tonight, thanks!

... bite it off?

Sorry. Terribly, terribly sorry.

You're all terrible, terrible people. (Which is, of course, exactly why I love you!)

It's amazing what a great vise and good cutting tools will do. We were finally able to get the dampener off. Tomorrow, clean out the metal dust, slap bolt everything back together, and fit the engine in. WOO!

I don't know if this project will make it to Florida, but I sure as heck am going to try. :D

Officially calling this the 2014 Miata. I've convinced my buddy Jeremy to move to CA and I'll need to tow his stuff back after the Challenge. :D Priorities!

I'm not sad - let's me pull that tubular subframe and learn to make my own and put that $750 back in my budget. My other Miata might just get the V8 subframe and a V8 to boot.

See you all at the Challenge!

Good job on the pos dampener off

Glad to see you are back onto this project! Now you just need boost...

EDIT: On the shaft tip (just the tip? heh heh yeah I know all men are disgusting pigs ) thing, here's the deal: the pilot bearing keeps the input shaft properly aligned with the mainshaft in the trans, if it's just chopped off and the input shaft is allowed to 'hang', it can get way out of alignment with the innards of the transmission. If it's, say, .080 out of alignment at 7000 RPM really ugly things happen to the transmission innards since the input shaft is whipping around. There are some transmissions designed to deal with a non piloted input shaft, the Miata/RX7 unit is not one of them.

There is no reason you can't have someone make an Oilite pilot bushing which would save a lot of the aggravation/expense of having a machine shop regrind the shaft. That's what I did when I swapped the Toyota Supra W58 trans into my Jensen Healey, in fact I made that pilot bushing myself with a worn out South Bend lathe. All you need are the shaft tip OD and eccentric shaft ID measurements.

In reply to Curmudgeon:

I'm thinking what we'll do is just pull the shaft from the RX7 trans and swap it to the gearbox and tail from the Miata trans. Seems like the cleanest thing to do, especially since the RX7 trans is now filled with metal dust from cutting off the dampener... :D