pitesy
Part of things
Posts: 10
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Jan 19, 2022 22:00:33 GMT
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Hi guys,
I am currently preparing to install a 1.8 vvt MX-5 engine in my RX-7.
As the MX-5 has a power plant frame thingy that connects the gearbox to the diff, the fabrication of the mounts looks to be a bit awkward.
How did you mount your gearbox? I have seen a few swaps done on the forum, but not many pictures. Ideally I would attach something to the part where the PPF goes normally and not where the 2 threaded holes are below the shifter. It goes in a heavier can than the MX-5 and it will be turbocharged eventually as well and I'm unsure about how strong those are.
Thank a lot for your ideas and help!
Best regards
Stefan
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Jan 19, 2022 22:34:42 GMT
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Usually i would make a bracket to fit to the gearbox. Depending on how much space there is and the shape of gearbox and tunnel i would look at what type of mounts i could use.
Bmw uses a nice construction you might be able to copy of you have room under the gearbox. Consists of 2 cylindrical vibrationdampers mounted on an angle.
If you can only hang the gearbox from the car i would look at using a rubber as used in controlarms or leafsprings. Piece of pipe with rubber and a metal sleeve in the middle. These can be found in many sizes and shapes.
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Jan 20, 2022 14:57:40 GMT
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I did this for fitting a mx5 box into a minor,  Could probably do with a bit more stiffening for something more powerfull. |
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Jan 20, 2022 15:58:29 GMT
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I did this for fitting a mx5 box into a minor, Could probably do with a bit more stiffening for something more powerfull. We did almost exactly this for my B2000/MX5 turbo conversion, couple of poly mounts and job's a goodun! |
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bricol
Part of things
Posts: 289 
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Jan 20, 2022 17:15:31 GMT
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I used a Ford Type9 mount bolted to those two bolts holes you don't want to use under the 6 spedd box, with a bracket I made to duplicate the shape of the Ford box stub.
More than enough strength.
I also made new engine mounts, bolted further forward, rather than reuse the original Mazda ones, which are designed to work with the fame and the diff mounts.
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pitesy
Part of things
Posts: 10
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Jan 20, 2022 21:03:01 GMT
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Thanks a lot everyone! Usually i would make a bracket to fit to the gearbox. Depending on how much space there is and the shape of gearbox and tunnel i would look at what type of mounts i could use. Bmw uses a nice construction you might be able to copy of you have room under the gearbox. Consists of 2 cylindrical vibrationdampers mounted on an angle. If you can only hang the gearbox from the car i would look at using a rubber as used in controlarms or leafsprings. Piece of pipe with rubber and a metal sleeve in the middle. These can be found in many sizes and shapes. Thank you! That is a great idea! I only had troubles thinking of something attached to the PPF mount, but seeing the other comments, it should be easier. I did this for fitting a mx5 box into a minor, Could probably do with a bit more stiffening for something more powerfull. Thank you! I was only afraid of those two holes on the back of the gearbox not being strong enough, as I was unsure, if they were meant to be a mounting point. I did this for fitting a mx5 box into a minor, Could probably do with a bit more stiffening for something more powerfull. We did almost exactly this for my B2000/MX5 turbo conversion, couple of poly mounts and job's a goodun! Thank you! Indeed great to hear you had good results with those mounting bolts running a turbo. How much power are you making? If those hold 200whp I'll make my around around them, as it's 10x easier than mounting off the PPF part. Did you use poly engine and diff mounts? Can you please tell which ones? I used a Ford Type9 mount bolted to those two bolts holes you don't want to use under the 6 spedd box, with a bracket I made to duplicate the shape of the Ford box stub. More than enough strength. I also made new engine mounts, bolted further forward, rather than reuse the original Mazda ones, which are designed to work with the fame and the diff mounts. Thank you! Do you mean those holes should not be used with the 6 speed box? I was thinking of buying one eventually. Can you please tell me why? Are they weaker on that part? |
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We did almost exactly this for my B2000/MX5 turbo conversion, couple of poly mounts and job's a goodun! Thank you! Indeed great to hear you had good results with those mounting bolts running a turbo. How much power are you making? If those hold 200whp I'll make my around around them, as it's 10x easier than mounting off the PPF part. Did you use poly engine and diff mounts? Can you please tell which ones? No worries, power was around 200/220bhp (1.8, TD04, Megasquirt etc). For engine mounts we had to use what were essentially tractor engine mounts due to the way the engine sat in the bay, they had to be much taller than usual. I think you may get away with stock engine mounts in the RX7, is it an FB/FC/FD? Make sure to put a build thread up, I am a huge fan of the RX7's! |
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pitesy
Part of things
Posts: 10
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Jan 21, 2022 10:15:16 GMT
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Thank you Trikkisixx! I'll just wait until my new engine is here (sold the mockup a while a ago) and try visualising it again.  If those 2 holes were okay for 220bhp, I think I would get away with mounting mine there as well. Good idea, I will create a thread soon. It is a sloooow build, but would be nice to document it. Oh, and it's an FC. Someone had it caged 20+ years ago and hasn't used it much since. I bought it as a roller. But I'll inculde details in the thread. |
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Jan 21, 2022 10:28:45 GMT
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Thank you Trikkisixx! I'll just wait until my new engine is here (sold the mockup a while a ago) and try visualising it again.  If those 2 holes were okay for 220bhp, I think I would get away with mounting mine there as well. Good idea, I will create a thread soon. It is a sloooow build, but would be nice to document it. Oh, and it's an FC. Someone had it caged 20+ years ago and hasn't used it much since. I bought it as a roller. But I'll inculde details in the thread. No problem Yes you will be fine. Look forward to seeing it! Good luck! |
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Jan 21, 2022 11:10:04 GMT
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those two holes are also mountings for the mx5 PPF so should be pretty capable.
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pitesy
Part of things
Posts: 10
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Jan 21, 2022 13:42:46 GMT
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Thank you Trikkisixx! I'll just wait until my new engine is here (sold the mockup a while a ago) and try visualising it again. If those 2 holes were okay for 220bhp, I think I would get away with mounting mine there as well. Good idea, I will create a thread soon. It is a sloooow build, but would be nice to document it. Oh, and it's an FC. Someone had it caged 20+ years ago and hasn't used it much since. I bought it as a roller. But I'll inculde details in the thread. No problem Yes you will be fine. Look forward to seeing it! Good luck! Thanks a lot! those two holes are also mountings for the mx5 PPF so should be pretty capable. Thanks a lot! You are right, it's attached there by a small L bracket. Almost forgot that... |
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bricol
Part of things
Posts: 289
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Jan 24, 2022 15:43:52 GMT
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I used a Ford Type9 mount bolted to those two bolts holes you don't want to use under the 6 spedd box, with a bracket I made to duplicate the shape of the Ford box stub. More than enough strength. I also made new engine mounts, bolted further forward, rather than reuse the original Mazda ones, which are designed to work with the fame and the diff mounts. Thank you! Do you mean those holes should not be used with the 6 speed box? I was thinking of buying one eventually. Can you please tell me why? Are they weaker on that part? Sorry - I was trying to be too clever - you mentioned you didn't want to use them, so I tried to identify the ones I DID use as being those same two holes, with mine being a 6spd. I reckon they will be more than strong enough, although mine's not exactly had a hard time yet. |
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pitesy
Part of things
Posts: 10
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I indeed misunderstood you. Sorry, English isn't my native language. I was googline around and have noticed, that Westfields also you these engines and gearboxes. This is their solution (the right one on the 1st pic):   Might do something like that, but a bit thicker (5 or 6mm). Maybe even countersunk bolts so it won't have that overhang for the rubber mounts. |
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Last Edit: Jan 26, 2022 0:34:03 GMT by pitesy
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bricol
Part of things
Posts: 289
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Jan 27, 2022 11:40:24 GMT
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Overhang for the Westfield probably more to move the rubber mounts closer together so they fitted in the transmission tunnel, while still allowing room to tighten the nuts on their mounting studs. I think the nuts would collide with the boss on the gearbox if they were in-line with the mounting to the gearbox in their application.
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pitesy
Part of things
Posts: 10
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Thank you! I also think that is the reason. I picked up 4 Land Rover V8 engine mounts, will use them as engine and gearbox mounts as well. They are a bigger diameter than the above bobbins. I am thinking about coutersinking the bolts that attach the bracket to the gearbox bosses, so it sits flush. Than I can play around with the positioning of the Land Rover mounts. Also want to avoid that rear overhang, as my chassis most probably won't require having it like that (so less leverage and stress on the mount and bosses as well). Makes sense in my head, hope it also does written. |
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