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Discussion Starter · #1 ·
Anybody got pics of the 1.8L BP tranny's bolt pattern? I need a pic of the bolt pattern of how the transmission bolts up to the engine. Either pics of the engine (flywheel side of course) or the transmission would suffice.

Muchos gracias in advancioso
 

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You'll have to wait till I get off my lazy butt and pull it out again. If it was so friggin heavy it would be so bad.
 

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Discussion Starter · #8 ·
Sarge- many many many thanks. Quick question- has anybody here converted a carb'd engine to fuel injection? I'm currently reverse engineering a DIGI-FANT2 system from an old golf to work with my RX-7. I have to design a system to replace the hall effect sensors with something else like an optical sensor mounted on the distributor. Should be fun.

I'm playing around with the idea of swapping the escort GT's BP engine into my RX-7, of course along with an expensive and rather large turbocharger and all the management to match. My sources say that the transmissions mate up, but from the pics of the tranny in the haynes manual, and your pics (and other pics I have seen of the miata engine) it seems as though the two couldn't be more different. I'm not sure if you have to swap the bellhousing off a miata tranny, and that the BELLHOUSING is the thing that mates up to the centerpiece of MY transmission.

Jeff- tell me more about this plate that sits between the engine and the transmission. I did a little work on a 3SGTE engine and there was no plate. How thick is it? If it's along the tune of 1/4" thick, I could make an adapter plate of the same thickness and not risk having the clutch slide off the splines of the output shaft of the tranny.
 

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I know exactly what Jeff was talking about but can't remember where exactly it sits. It's definitely in between the tranny and block, but it's only about 2 cm thick (judging by my recollection and looking at a ruler). I think 1/4" would probably be too big. The plate has a hole for the start motor I think too...it's more of a gasket.
 

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m0nk said:
I know exactly what Jeff was talking about but can't remember where exactly it sits. It's definitely in between the tranny and block, but it's only about 2 cm thick (judging by my recollection and looking at a ruler). I think 1/4" would probably be too big. The plate has a hole for the start motor I think too...it's more of a gasket.
Its a really flimsy peice of metal, probally aluminum, had one on my 89 GT. It acts sort of like a gasket then anything, i think its just a plate so the tranny and block dont seize together (dont even know if that can happen) Im not sure if you need it, but its there. I dont have a pic, but ill look for one.
 

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Discussion Starter · #11 ·
It's alright... don't bother looking for a pic. I'd only be interested if it were thick enough to have some strength. Adapter plates have to withstand the shock of the torque when you engage the clutch to the flywheel.
 

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I was suggesting the plate just if you needed to know the bolt pattern. If you wanted to see if a certain motor would fit a certain tranny you could just buy the plate from each one and compare them back to back to see if the bolt pattern lines up, or just to have an idea on how off they are.
 

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Discussion Starter · #13 ·
I just went out to the 7 and compared the tranny bolt pattern of the BP to the stock tranny on the '85 RX7 and they're absolutely nothing alike. I dunno how people mated the 12A rotary engine up to their miatas... they must have taken the RX7 tranny along with it or something, Hm.
 

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siragan:

Don't ever mention Hall Effect on this site again. We're all Grade 8 drop out who work at McDonalds flipping burgs. That crap is all hypothetical anyway, just like imaginary numbers. There is no such thing as the square root of a negative number. 1+1 = 2 always.

I took my digicam to the pit the other day but no escort had the tranny removed without the engine also heisted. Sarge saves the day again.
 

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I'm not sure if it is or not, but the vast majority of Front-Engine, RWD (FR) transmisisons I have seen have had the gearbox separate from the bell housing. I'm not sure if the bellhousings are removable on the miata/rx7 trannies, but i think they are not. Adapter plates were used...

here's a GREAT thread with some good links on miata.net for mating a TII tranny to a BP engine...
mita.net link

here's another link with a guy that built a sweet adapter plate. Maybe contact him and see if he can fab you up another one, sounds like after that's done, all you need is a way to mount the engine in the RX7 bay....

--sarge
 

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Discussion Starter · #17 ·
I'd ditch the rotary because it's just inherently bad on gas. The '7 is my daily driver... right now it's running pretty lean, and on only about 1/3 of a rotor under full throttle. It gets 25mpg, which is fine, but it's only putting out like 50hp according to my butt dyno. The thing is so slow, I can hardly keep up with caravans from stoplights... even when the caravans aren't trying to race. It's honest to god, the slowest car I've ever driven... in a striagh line. I'm planning on tuning it... but I just like the BP. With my old escort GT, the thing was fast as hell and I could still get 41mpg highway. Rotary engines are good for racing... but they're just not practical. And for all you guys saying to yourselves, "damnit siragan, just tune the damn thing!!!", yes... I am going to tune it before I swap anything out. I'm just looking at my options.

There were three different mazda RWD transmissions: (taken from Pele at RX7club.com)
  • Type 1 is usually called the Rib Case... It's a fairly old design used on the old RX2,3,4,Cosmo and stuff..

    Type 2 is the N/A RX-7 tranny. Also used on the RWD 626, GLC, Miata, and B2200 and lower trucks...

    Type 3 is a newer incarnation of the old Rib Case... It's used on the RX-7 Turbo, the 929, and the B2600 Truck...

So according to him, a miata engine should bolt right up to my tranny. Maybe he's talking about the 1.6L engine or something.

Adapter plates, in my eyes, are "botches" to the solution. Does it work? Yes. But by doing so, you are shifting the clutch/pressure plate assembly farther OUT on the input splined shaft of the transmission, and as a result, two things happen:

1. You get less input shaft for the clutch to "grab" onto, so you risk stripping the splines of the shaft off, and also torsional shearing of the input shaft itself.
2. You are forced to modify the release fork/ T.O. bearing assembly to be able to push the fingers of the pressure plate an extra distance, x, which is equal to the thickness of the adapter plate used.

I could do this, yes. I have access to not only a plasma cutter, but also MIG and TIG welders, a CNC machine, a waterjet, and a laser cutter. I even have assess to a metal rapid prototyping machine. I could technically create my own custom bellhousing. I've got access to stuff that most car buffs only dream of having access to. But ego and such aside, let's be realistic. With all the time and energy it would be to fabricate all that crap, I'd be better off buying a NEW engine/tranny combo (I was thinking of going with nissan, I like their engines) and simply modifying the driveshaft.

That way, the only three things I would need to modify would be:

1. The driveshaft
2. The mounts (both tranny and engine)
3. The management system (chances are I'd get a front clip w/ harness/ecu)

I dunno exactly what I want to do. I was really hoping the BP would bolt right up to my tranny. What I will probably do is create an independently managed, entirely custom built fuel injection system on the 12A engine I've got, and throw on a turbocharger. I don't care who you are talking to, turbocharged rotaries, when tuned correcty, are some of the best race powerhouses you can get. I'd keep my weight balance near perfect, and I'd probably be pushing out about 200 horses out of the engine. It'd be badarse. I think I'll probably go that route. I'll spend a ton of money becuase it'll only get like 11mpg... but I guess you only live once.
 

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with an adapter plate, all you need is to change the throwout bearing depth to not mess up the fork throw. (or just use a hydraulic TO bearing and skip the fork altogether).

The clutch disc doesn't really grab more than an inch or so of the input shaft anyway, and the splines usually go 3-4 inches.

More importantly when using an adapter plate is to make sure your input shaft is seated in the pilot bushing ok.

I don't think you're going to get a lot better mileage out of a BP when in an RX7 though, because the car is heavier than the escort. plus the gearing might be kinda low, since the rotary redline is at 8k instead of 7, so you'd be probably getting the same mileage with the BP as with the rotary. I'd say just do a 13B (TT?) upgrade, instead of using the 12A, if you do any sort of swap... :)

--sarge
 
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