20b In A Rx2
05-06-2004, 12:05 AM
#1
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Join Date: May 2004
Posts: 5
Hey there. I am new to this forum and have found this avenue in my search for info. I have a really nice 73 RX2 that I have been SCCA racing for a couple of years. I can stomp most Vettes with a 12a powerplant and I am now transplanting a 96 20B with a Turbo II 5 speed into the little gem. I am desperately searching for info on wiring diagrams, subframing the RX2 so it won't turn into a prezel and rear end swaps or upgrades. Anyone who could give me some help would be greatly appreciated. Thanx. Mike Beggy. Tucson, Arizona.
05-06-2004, 12:30 AM
#3
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Join Date: Nov 2001
Posts: 2,284
That sounds like a great project. Are you planning on keep the stock twins? They weigh 62LBS which includes the cast iron downpipe, manifold, and turbos themselves. What are you thinking of using for fuel? FI or carb? ECU or dizzy? Forced induction or NA?
Are you going to cut into the firewall and tranny tunnel? The T2 tranny has a starter that fits further out than an NA tranny. It might interfere with the gas pedal. Is your RX-2 a '73 or older model? If so, the shifter will go back an additional 40mm on top of the 160mm, plus 20mm more going from 12A to 13B measurements. If you couldn't follow that, let's think of the length of a top mounted starter tranny. The shifter stick up at point A. If you were to swap in a '74-'80 tranny, the shifter would come up 40mm further rearward. If switching to a 13B, add an extra 20mm further rearward. Keeping the tranny for argument's sake, add an additional 160mm. Since you're going with a T2 tranny, add an additional 100mm (aprox 4 inches). The people in the back seat could shift for you.
Take my GLC for example. I need to have the driver's seat as far back as it will go. The stock boinger shifter was incredibly far forward. The '76 Cosmo ribcase shifter if 30-40mm further rearward, but I still need to use a '79-'80 SA22C curved-back shifter, which is still uncomfortably too far forward. Since my 20B's extra length is going rearward only (using front cover motor mounts on RX-3 crossmember instead of side mounts), my shifter will move back 160mm or around 6 1/2". It will get really close to the E brake, but it can be tweaked to the side if need be. The good thing is the shifter will finally be a comfortable position for me.
If your RX-2 is a '74 with a bottom mounted starter, it may be easier to do the swap. Then again, I don't have an RX-2 in front of me, so your guess is better than mine.
Hmm, I'm still wondering about the rearend for my car. I may go with a big ford 9 incher because the 8.8 is appearantly junk. The axle tubes are clipped on and will flex under power. For me, it's either the ford 9" or an RX-7 LSD disc brake rear. I'll just have to see how hard it is to brake the stocker. I bet my U joints will break first though. Tiny things.
What kind of radiator and oil cooler do you plan to use? The stock oil cooler might be ok unless you plan on using the stock twins. I don't know enough about RX-2 radiators.
Do you have any pictures?
Are you going to cut into the firewall and tranny tunnel? The T2 tranny has a starter that fits further out than an NA tranny. It might interfere with the gas pedal. Is your RX-2 a '73 or older model? If so, the shifter will go back an additional 40mm on top of the 160mm, plus 20mm more going from 12A to 13B measurements. If you couldn't follow that, let's think of the length of a top mounted starter tranny. The shifter stick up at point A. If you were to swap in a '74-'80 tranny, the shifter would come up 40mm further rearward. If switching to a 13B, add an extra 20mm further rearward. Keeping the tranny for argument's sake, add an additional 160mm. Since you're going with a T2 tranny, add an additional 100mm (aprox 4 inches). The people in the back seat could shift for you.
Take my GLC for example. I need to have the driver's seat as far back as it will go. The stock boinger shifter was incredibly far forward. The '76 Cosmo ribcase shifter if 30-40mm further rearward, but I still need to use a '79-'80 SA22C curved-back shifter, which is still uncomfortably too far forward. Since my 20B's extra length is going rearward only (using front cover motor mounts on RX-3 crossmember instead of side mounts), my shifter will move back 160mm or around 6 1/2". It will get really close to the E brake, but it can be tweaked to the side if need be. The good thing is the shifter will finally be a comfortable position for me.
If your RX-2 is a '74 with a bottom mounted starter, it may be easier to do the swap. Then again, I don't have an RX-2 in front of me, so your guess is better than mine.
Hmm, I'm still wondering about the rearend for my car. I may go with a big ford 9 incher because the 8.8 is appearantly junk. The axle tubes are clipped on and will flex under power. For me, it's either the ford 9" or an RX-7 LSD disc brake rear. I'll just have to see how hard it is to brake the stocker. I bet my U joints will break first though. Tiny things.
What kind of radiator and oil cooler do you plan to use? The stock oil cooler might be ok unless you plan on using the stock twins. I don't know enough about RX-2 radiators.
Do you have any pictures?
05-06-2004, 12:45 AM
#4
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Join Date: May 2004
Posts: 5
Wow....where to begin. From my early measurements, the trans tunnel area will need to be cut and modified for engine clearance. I hope to start out with a fully functional stok engine and turbos. The trans has a shifter bracket which moves the shift lever rearward for the RX7 application. I have cut the shaft and modified the mount to save about 5 inches. It still is rear of the RX2 location but only a few inches. The engine mounts and subframe are my current focus as well as the wiring. I'll tell you more in the future.
05-06-2004, 02:04 AM
#5
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Join Date: Nov 2001
Posts: 2,284
Here is something I just found. You'll probably find it to be of value. I sure did. http://ausrotary.dntinternet.com/forums/vi...81903d74dd6e245
05-06-2004, 11:36 PM
#7
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Join Date: May 2004
Posts: 5
For those of you that have been there, are there any diagnostic tools that are used for the Japanese 20b when trying to get the stock ECU to work? I still don't have a line on getting a wiring diagram for a place to start. The engine appears to have some really in depth design features which aren't easily understood without some basic knowledge. BTW, I have the 12a sitting next to the 20b in my shop and the 20b with the trans weigh 202 #'s more that the original equipment. If I can get it far enough back in the car, I am hoping that the additional weight won't kill the way the car handles. I'm currently (was) at 55/45 front to rear with a near perfect 50% cross weight. Does any know if you can switch to a 12a front cover and use the same front mounts without breaking the front cover under power? Semms like going from a 100hp motor to 300 or so may require a different approach to mounting in the car.
05-07-2004, 12:41 AM
#8
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Join Date: Nov 2001
Posts: 2,284
The front cover handles 200HP just fine. I'm not sure about 300, but Japanese people do it in their FBs. I installed an '84 front cover on mine and mounted it RX-3 style in my GLC.
The extra weight is from the automatic and the stock twins. Automatics always way more than a manual from the same car. Since the JC Cosmo never had a manual option, we can compare it to a T2 trans. Again, it weighs more. The stock twins are 62LBS. My engine used to lean to one side until I removed the twins. My NA header only weighs 21.5LBS!
My intake only weighs 25LBS which is 3.5LBS more than a genuine '74 REPU intake manifold and carb with ACV. This does not include the (heavy by FB standards) REPU air cleaner assembly with charcoal canister in the lid. It also does not account for the thick piece of plate steel that somebody used as an ACV blockoff plate on my JDM manifold that's on the 13B in the GLC. I'd bet that thing adds at least 3.5LBS if not more to the carb/manifold combo in it. In other words, the intakes of both engines weigh the same +/- maybe one pound. Again, not counting air cleaner assemblies, which are both simply sheet metal and foam.
Only the 80mm thick 20B-only plate with stationary gear is a concern to me right now. Everything else, when compared part-by-part, will show the 20B side plates, rotors, rotor housings (and in my case, an FC aluminum waterpump compared to an FB cast iron unit on the 13B), and especially flywheels, will be on the lighter side. This holds true for R5 13Bs (such as mine) and any 12A (such as yours) with their slightly heavier... well, everything (even the lightest 12A rotors are still the same weight as 20B rotors, I think... 9.5LBS). Mazda shaved a pound here and there on each housing in '86 and rotors in '89 and later engines. This advantage quickly goes away though with one additional rotor, housing, 16CM length of E shaft, 16CM longer tension bolts etc.
The only one I don't have a weight for is the 80mm thick plate. j9fd3s, could you weigh it for me? Thanks.
The extra weight is from the automatic and the stock twins. Automatics always way more than a manual from the same car. Since the JC Cosmo never had a manual option, we can compare it to a T2 trans. Again, it weighs more. The stock twins are 62LBS. My engine used to lean to one side until I removed the twins. My NA header only weighs 21.5LBS!
My intake only weighs 25LBS which is 3.5LBS more than a genuine '74 REPU intake manifold and carb with ACV. This does not include the (heavy by FB standards) REPU air cleaner assembly with charcoal canister in the lid. It also does not account for the thick piece of plate steel that somebody used as an ACV blockoff plate on my JDM manifold that's on the 13B in the GLC. I'd bet that thing adds at least 3.5LBS if not more to the carb/manifold combo in it. In other words, the intakes of both engines weigh the same +/- maybe one pound. Again, not counting air cleaner assemblies, which are both simply sheet metal and foam.
Only the 80mm thick 20B-only plate with stationary gear is a concern to me right now. Everything else, when compared part-by-part, will show the 20B side plates, rotors, rotor housings (and in my case, an FC aluminum waterpump compared to an FB cast iron unit on the 13B), and especially flywheels, will be on the lighter side. This holds true for R5 13Bs (such as mine) and any 12A (such as yours) with their slightly heavier... well, everything (even the lightest 12A rotors are still the same weight as 20B rotors, I think... 9.5LBS). Mazda shaved a pound here and there on each housing in '86 and rotors in '89 and later engines. This advantage quickly goes away though with one additional rotor, housing, 16CM length of E shaft, 16CM longer tension bolts etc.
The only one I don't have a weight for is the 80mm thick plate. j9fd3s, could you weigh it for me? Thanks.
05-12-2004, 02:48 PM
#9
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Join Date: Nov 2001
Posts: 2,284
That 20B-only 80mm thick plate is 36 pounds not including stationary gear (thanks Mike). Just add that to the known weights for the rest of the parts and you'll have an accurate weight for the 20B, give or take a little.
Any news on your project?
Any news on your project?
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