Author Topic: Mx7? rx5? Newbies build thread begins  (Read 21978 times)

Offline Steve-A

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« on: April 10, 2010, 10:47:32 PM »
Hi guys.

I\'ve been lurking here for a while, slowing learning about these roundy-roundy engines, but I thought it was time to say hi.

I\'m Steve. A couple a years ago I bought an mx5. She looked like this:



88k on the clock, a whole 88hp at the wheels... Either way I loved the drive and roof down experience and realistically it was 100 times better than any of the \'classic\' british roadsters I\'d been to test drive.

Very soon I joined an mx5 forum and started to get tempted into performance modifications.....




Thats how she stands now. 200+ hp from the standard engine, turboed with different cams and megasquirt.

Anyway, meandering back towards rotaryness..... I\'ve always lied the idea of a 7. I love the lines of an FD and to me one of the most appealing things is the concept of rotary power. It seems to hold many similarities with two strokes, and I adore my two stroke motorbike. I had a Ducait 748 for a while, which was a work of art, but was blown away by the riding experience of a 20 year old knackered mismatched rgv250. I\'ve now done a complete rebuild on her mechanically. Crank, top end, gearbox, all suspension bearings, all brakes, the list goes on. Still havent started on body work.....



So yeh rotary.... So I started reading more and more about rotary engines and I really like the idea. I was soooooo close to going out and buying an FD a few months ago, but there are just too many draw backs for me and the way I use my car. The biggest draw back is the lack of soft top. You cant beat a nice summers evening with a lady in the passenger seat and the roof down.... I know I could get an FC vert, but they just don\'t do it for me.

Having decided I couldn\'t quite go for an FD, I\'ve decided I\'d like to do a rotary swap into my mx5. I\'ve been doing lots of reading on the internet and I\'ve found masses of information. Its not an easy swap, infact is easier to drop an ls1 v8 from a corvette in than the 13b, but I like a challenge.

One thing to my advantage is that I\'d like to try n/a for a while, I\'ve enjoyed  having turbo power delivery for the last year but I\'d like to experience the pure revvy feeling of high tuned n/a. I very much like the idea of throttle bodies and quite an aggressive port and hopefully to end up near the same power as my current set-up. That said I\'m not very power focused, more experience and feel focused.

If I start with an n/a 13b from a FC there is one big advantage over any other rotary. The FC n/a gearbox is basically the same as an mx5 gearbox. By using parts from both I can use the FC bell housing and bolt upto the block easy yet retain all the mx5 mounting points, the mx5 prop and rear end.

I will need heavy modifications to the front subframe, or possibly to buy a posh tubular one from the states, to clear the 13b sump. I\'m gonna need custom engine mounts. I\'m gonna need a fully custom exhaust. I\'m gonna need to organise some engine management, I plan to use megasquirt.

I\'ve picked up a dead 13b, with good gearbox from a friend to use as template for subframes and stuff, and this week I\'ve started to sell of my turbo bits to raise some funds, so its project go! I\'ll try to keep this updated.
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Offline rossonza

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« Reply #1 on: April 10, 2010, 11:39:21 PM »
Welcome Steve! And I wish you the best of luck with this build
email @ rossonza@gmail.com
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Offline Nik da Greek

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« Reply #2 on: April 10, 2010, 11:50:20 PM »
Wotcher, Steve, welcome to the club and all that. Liking your Gamma there, a rotary\'s the same except it goes round rather than up and down, nothin\' to it :Giggle You don\'t need such cobra-like clutch hand reactions with a rotary though :D The swap you\'re looking at has been done before, I think a fair few Yank cars have had it done. Martin at Speedline Imports on here is a good way through doing a similar conversion, and he\'s also a great source of bits! Be interesting to see how you get on

Offline Paul-Tll

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« Reply #3 on: April 11, 2010, 06:45:20 PM »
Great project, keep the pictures coming and good luck with progress of your RMX5. you should end up with a really good  and desirable car at the finish. Be sure to come along to some meets later this year, so we can have alook !:3gears-lh
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Offline m1tch

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« Reply #4 on: April 11, 2010, 08:18:20 PM »
Hi mate, ask Speedline imports, he has an MX7, I asked about it, all you need is custom engine mounts and a cut down propshaft and everything just fits :) regarding the egi/turbo route, get a turbo lump, with turbo ECU etc, and just plumb it in as an EGI, the ECU will just use the NA part of the mapping, then you can just bolt the turbo on when you get bored of beating everyone just a bit :)

Offline Steve-A

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« Reply #5 on: April 11, 2010, 11:00:56 PM »
Thanks for the useful info guys.

I\'ve got a list of 20 or so build thread from guys who\'ve done the same swap in the states to try and gleam some info from. It could be that I\'ve already read Martins thread on the mx5nutz website, if its not the same bloke then I only know of 2 rotary swapped mx5s in the UK and they are both owned by a bloke called Martin!

Having done lots of reading I\'m definitely going to start with the EGI engine, as it allows me to build the hybrid mx5/rx7 gearbox and use standard gearbox mounts, prop and diff. I\'d also really like to try the whole high revving n/a thing for a bit having only really had experience with turboed performance cars. I\'m sure the old snail with tempt me back at some point but the main thing now is to get over the mechanical aspects of fitting the rotary engine in.

ECU wise I think I\'m gonna build a custom loom to use with my megasquirt. Thats the simplest option wiring wise and I\'m very comfortable with the Megasquirt platform.

I\'ve got a buyer for my mx5 turbo kit confirmed, just need to drop my performance clutch out to sell as part of the kit, so thats useful.

I\'ve arranged to get the engine out of Lee Mills EGI now he\'s decided its too rusty to continue with, so will be going to collect that next weekend.

I\'ve been started to strip down the dead egi block I\'ve got to see what\'s usable. Gear box is fine, clutch looks fine, intake manifold and throttle body assembly is fine, so again useful stuff.




I\'ve got 8 injectors to get cleaned and pick the best 4 from, as I already had a set I\'d bought off ebay to use with my megasquirt and turbo mx5 block.

Finally I\'m gonna find out the shipping costs to get this: v8 roadsters subframe imported from the states. Should eliminate the awkward cutting/welding needed of the standard subframe to clear the 13b sump, and be 5kg lighter and stiffer than standard.
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Offline Nik da Greek

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« Reply #6 on: April 11, 2010, 11:03:37 PM »
Never mind all that old rotary nonsense, more pics of the 250 Gamma please :rollin

Martin has an advertisers section on here as Speedline Imports, dude if you wanna check it out.

Offline BlitzBoy

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« Reply #7 on: April 12, 2010, 12:21:48 AM »
Here is a link on how to use a Megasquirt with a Rotary engine
http://www.rx7club.com/forumdisplay.php?f=153

Martin\'s MRX5 achieved 270 at the wheels on low boost, which must be quite frighting on a small soft top car lol
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Offline Steve-A

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« Reply #8 on: April 12, 2010, 09:10:31 AM »
Cheers Blitzboy, I have in fact already bookmarked that forum and there\'s also a very comprehensive guide over on http://www.diyautotune.com :)

From experience just over 200hp at the wheels feels pretty exciting in an mx5, so 270 must be rather wild! I\'m sure its the same Martin now as on the mx5nutz forum, and its a very nice build. My build will be a little more cheap and cheerful but hopefully just as functional.:)

p.s. Nik, this is the beautiful noise of a 250 twin on Lomas race pipes after a fresh rebuild.

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Offline Nik da Greek

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« Reply #9 on: April 12, 2010, 09:57:04 AM »
Oooh, that\'s proper that is, that takes me back :yes. I want another stroker now :rollin No, not that sort of stroke, perverts :D

Offline Marcrs

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« Reply #10 on: April 12, 2010, 10:10:23 AM »
Hi Steve,

that\'s a pretty nice looking MX5 you have there...and a very interesting project, I\'ll be watching this closely :)

I remember riding my mates RGV250 when I had my Z900...not long after that I bought a GSXR750...and an RD400 to satisfy my 2 stroke urges ;)


good luck with the MX5, keep the pics coming :)

Offline Speedline Imports

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« Reply #11 on: April 12, 2010, 11:19:54 AM »
Hey Steve, yes that would be my 13b turbo MX7 build on Nutz.  Any queries etc feel free to get in touch and I will try to help you out as much as possible.  Good Luck with it :)
 
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Offline od404

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« Reply #12 on: April 12, 2010, 11:52:24 AM »
Great to see you\'ve finally decided to rotary Steve!  I will be keeping a close eye on this thread for updates :3gears-rh

Offline grinder

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« Reply #13 on: April 12, 2010, 05:24:27 PM »
ohhh an RGV250 - not seen one of those in a while

i couldnt afford one at the time so i went with a KR1-250 instead


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Offline Steve-A

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« Reply #14 on: April 12, 2010, 05:28:30 PM »
I wondered if you might have spotted this Steve, even if I get my own rotary powered car, I\'d still like that ride in your FD :P

Martin, it was your build that finally inspired me to take the plunge. I think I\'m fairly planned out for the moment but I\'m sure problems will surface along the way. The only thing I could do with a little info/help on is the subframe mods required. Nobodies very specific on the net so hard to know exactly what needs cutting, but as you\'re using the TII gearbox and a custom prop length I suspect non of your measurements will match up with my build.

My life would be made easier if I wasn\'t daily driving the mx5 while I plan this! Then I\'ve got a 1 week window to do the swap, so gotta do as much planning as possible!

KR1s are mean! Tankslapper is the word that comes to mind, haha. It almost seems like you guys need a 2 stokes sub forum :P
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