Hi all, After a while of being relatively quiet on here I am back with my latest!
It all began a few years ago after I had sold my last E30 (black 325i vert) and was feeling like something was missing. I flew to Auckland and purchased this coupe from a forum member. It was a great car and I picked it up for a price unheard of in todays E30 market. At the time I didn't have too many plans for it, just maintain it and drive it on the weekend. I changed the cambelt with the intention of keeping the M20 in it. At least it was reliable!
I couldnt help myself and installed a set of XYZ coilovers and Sportmaxx 16x8 wheels. I also had the rear guards rolled and pumped out along with painted bumpers and respraying the guards.
This lasted for summer until I decided to misbehave while driving for a wedding for Jamie (Black E30 in the pic).
The gearbox lost reverse while trying ever so hard (M20B20 remember) to get it to do a celebratory burnout. So I gave the 4hp22 one last farewell and got onto thinking about what I was going to do next.
I decided I wanted a repower. I considered this a huge challenge and something I had never attempted before, so I was anxious. I set about stripping the old M20 out and began to think about what was going to take its place. I contemplated M5x, RB25, 1JZ, V8s.. even a 13b turbo.
Then this turned up...
It was all on!
A 13b turbo from a series 5 Mazda RX7. I always wanted an RX7, the rotary engine was something that I just had to have. So what better than a rotary E30 to satisfy my cravings. The rotary also ticked many other boxes that the bigger inline 6 options didnt: engine bay space, brake booster clearance, power to weight.
With the engine finally stripped and sitting in the bay it was becoming apparent that it was a relatively straight forward swap. Custom sump and oil pickup were to be made. While a conversion to manual steering was going to give me more room under the engine and around the exhaust/turbo and also satisfy my need for a clean engine bay. Power steering isnt a necessity in a car this light with an engine that weighs as much as a weetbix box.
Custom engine and gearbox mounts were fabbed up and the engine yanked back out again to go back home. Once the mounts were completed I dropped the engine back in to check everything was correct.
Once I was happy that it was all going to fit I worked out where the intercooler and radiator were going to fit and mocked up some intake piping.
Then it was time to pull it all back out again and prepare for paint. This was exciting, I've always craved a smoothed over E30 engine bay!
The paint was laid down and I was stoked!
Engine back in again for the final time to start piecing it together. Now the fiddly stuff, nothing heavy, plenty of cursing and swearing to come! As the car was originally auto I fitted a manual pedal box early on in the piece with anticipation of what was to come.
All along I wanted to intercooler to remain hidden, but still receive good airflow so the piping was tricky. Because I am using a stock turbo and boost levels I have been able to keep the piping nice and small which was helpful in keeping it all hidden. Once I was happy it was off to get alloy welded and have the BOV mount welded in place.
Then black paint was applied before reassembly as well as mounting radiator, RX7 oil cooler (in factory location) and making hoses and lines to suit. I also removed as much of the front body loom as I could and hid the remaining wires between the radiator and oil cooler. I also made a throttle cable and clutch line etc while i was mucking around in the engine bay.
Finally starting to take shape..
I had decided to go standalone with the engine management. An old Microtech LTX-8 ECU was purchased and I undertook my very first attempt at wiring anything more than a headunit. I also fitted and wired in boost/vac, water temp and oil pressure gauges.
With the wiring completed and ready for first start up. Fluids were poured in, fuel was mixed and she fired into life! Took a bit of turning over to clear, but it started after a few goes! I was a pretty happy lad that night, it was finally starting to seem real. Also, a rotary engine is incredibly loud in the shed with just a turbo and no exhaust... Happy neighbours were not found in my area that night!
The next morning I discovered a small pool of oil under the car so the sump was removed and a small pinhole welded up. I was frustrated because I had checked the sump for holes.. obviously not well enough!
Next on the list was exhaust so the car was taken back out to my mates place where he has a hoist and the necessary skills to fab up some pipes/flanges. The exhaust consisted of a 2.5" short downpipe, 3" to centre resonator, 3" to rear muffler. This provides plenty of flow, a reasonable amount of noise reduction and next to no ground clearance at the height I had it. Ive since lifted the suspension 20mm at the front and 10mm at the rear just to give a bit of freedom underneath.
I had my tuner come round and check the car out to see if it was dyno ready - he checked things like voltage drop to the coils and fuel pump. Interferance on any sensors etc. He also set up the fuel maps at idle so that I could at least run through a few heat cycles and bleed the cooling system before putting it on the dyno for a tune.
Then it was dyno day!
The tune went well until 3500rpm where we found a misfire which turned out to be a malfunction in the ECU. We also found that the spark wasnt as strong as it could be so it was decided that I would replace the old coils before the next dyno day just to be safe. It was back to the drawing board and a little bit more wiring to be done.
While I was waiting for more dyno time I installed a handy little voltage gauge so I could keep an eye on the battery. I got it off trademe for a few bucks and hooked into the wiring that goes to the check panel. It reads about 0.4V lower than at the battery but at least it gives me some idea of whats going on.
Back on the dyno again after a few weeks
The tune was going good until 4500rpm where the turbo started to make some boost and the internal wastegate couldnt keep up. The ECU was cutting fuel at 13psi so we had to pull the pin. Back to the drawing board.
I found that the wastegate was hitting the back of the turbo and not opening fully, and also put some of the issue down to the fact that the exhaust was so much bigger than the factory downpipe and the turbo was flowing much faster and free'er than normal. I solved this by taking a scallop out of the backplate of the turbo and adding a 3mm restrictor plate straight after the turbo with a 2" hole (the size of the factory downpipe)
While playing around the exhaust I decided to delete the old steering guibo and heatshield to give me some more clearance and eliminate the chance of the extreme heat deteriorating the rubber.
I also decided to ditch the viscous fan as it needed a shroud to actually make it work and it was too hard to make a shroud. I replaced it with an electric fan and had a plate made up to shroud the fan and enable it to pull air across the entire surface of the radiator. I wired the fan so that I can either turn it on with a switch in the car or the ECU can turn it on at a set temperature.
I also added a heat shield around the turbo and downpipe after seeing it glowing red on the dyno.
It was almost dyno time again and after a few hard road tests to check the boost levels I encountered another problem. Small case diffs.
I quickly sourced a medium case 3.73:1 open diff from Ray @ Hellbm and installed that with some fresh Redline oil.
Back on the dyno and fingers crossed for the third time lucky!
The tune went well but we discovered the restrictor plate is choking the turbo a bit and the boost level starts to drop at around 6000rpm. This will be fixed one way or another in the future with either a boost controller or opening the turbo up again and adding an external wastegate. Power wasnt huge at 155kw at the wheels on a low-reading roller dyno. Once the boost issue is sorted out I should see close to 200rwkw. After driving the car home in the wet I decided 155rwkw is plenty for a street car for now and I will focus on getting the car legal/certed so that I can begin to enjoy it. The day after dyno I had to see what it was like in the dry.. Turns out it goes ok! I had to give it a bit of victory burnout love on the driveway which was great - Unfortunately the right hand side engine mount didnt think so and started to bend (8mm plate!!) So out it comes to have some strength added to it.. Two 5mmx15mm gussets at the weak point. It aint pretty but it works, the second victory burnout proved it! (on closed roads of course)
This weekend I managed to put the engine mount back in and also paint the inside of the fuse box cover. I'm crazy on clean engine bays and the transparent blue lid with yellow underneath just didnt cut it!
I understand the rotary E30 isnt going to be accepted by everyone here, and I also understand it isnt a first, but I'm always a fan of doing what you believe is right for you. After a bit of deliberation I decided on posting this so people that are interested can see what I've been doing and share their thoughts. After all, I built it for me! It wont get old driving down the road seeing peoples reactions to this car!
Its been a long time coming but this diary brings me up to date on my build thus far. Its been a huge challenge, but something I have enjoyed immensely! I've learnt more than I could ever imagine and become much less hesitant to take on big jobs. Next on the list is learn to weld, then I'll be unstoppable!!
While this isnt a comprehensive list of everything I've done and products I've used etc I feel I've covered the main points. Feel free to ask any questions you may have, or even offer criticism on things you think I could improve. I have acheived my goal of keeping the car low-key in appearance. From the outside the only give away is the exhaust, which could just be another E30 with a fart-can.. Until you hear it!
My goal was to keep this tasteful and not your typical "brap brap brap Rota BeMa G" Now that I have finally posted this project I will continue to update this thread as I make progress.
Happy building and thanks for taking the time to read this thread!! Jason
Edit: heres a flame pic!