Zac's 1998 Series 7 FD3S RX7

Zac Perston

Tutor

729 Posts

New Zealand

I'm a complete build thread junkie, I can't get enough of them and I'd love to see the build threads section of the forum expand further, to that end, I though I'd put up some details about my current project.

It's a 1998 Series 7 FD3S RX-7. I purchased it a couple of years ago very cheaply as it had an electrical problem the owner couldnt figure out... It turned out to be the primary and secondary injector connectors on the front rotor were swapped, so it was hugely overfuelling on that rotor. It's the usual rotary story, rebuilt engine recently, but no real proof of that... There were some reciepts with it, one for a new housing, so that's a good sign I suppose?

First thing I did after getting it running was to make up an adaptor to fit a cheap aliexpress pressure transducer into a sparkplug hole, the output of which was nice and even, so I'm fairly certain the motor is actually pretty healthy.

https://www.hpacademy.com/assets/forum/attachments/Zac3.PNG

https://www.hpacademy.com/assets/forum/attachments/Zac4.PNG

The twin turbo system had a few issues, no big surprise there, but it was a good excuse to tear it apart and get familiar with it. After mapping out how it all worked I tested everything, replaced the solenoids that were stuffed and the one way valves that were leaky. Once back together the car really perked up. I've never actually put a boost guage on the thing, but it ran cleanly through to the redline, seemed to make good power and you could really feel the second turbo kick in.

I tidied up the body and interior as best I could, and came to the conclusion that its actually a pretty honest car. Everything is there, all the clips, original fasteners, no modifications to the interior, etc... So I figured it'd be a good one to keep that way. I had a job that I was commuting too and from 3 hours a day, and I enjoyed taking the RX7 most of the time. We had a race-track at work, so lunch-time was usually pretty fun. The tyre and petrol bills really started to stack up though.

After around 15,000 trouble free k's, the turbos seals went bad in a big way, and it started smoking pretty heavily. The problem was so bad, than when I took the intercooler out, there was around 500ml of oil in the bottom tank I had to pour out.. Atleast my apex seals were well lubricated? ;-).

I looked at, and even purchased a couple of sets of second hand turbos, but none of them really seemed like they would be in any better condition than my current ones. Rebuild kits for them are really bloody expensive too, as although they're just a hitach HT-12, they have a carbon face front seal, which apparently gives the aftermarket permission to charge moon-beams for replacement parts... rotary tax eh? I figured I would do something a little different and fit a set of twin turbos off an R32GTR that a friend of mine had sitting around.

One of the first tasks I undertook at my last job was to set up the CNC machine shop. I've always had a passing interest in machining, and have a little experience, but nothing too serious. This project got me very familiar with Fusion 360, as I had to write the post-processors to talk to the different controllers running the machines in the shop. Was fun, and I learnt a heap, which I then wanted to put into practice on a project for myself (the actual machining of every day parts wasn't my job at my previous employment, just setting up all the systems initially). I started with a couple of simple items, a sump brace and some emissions block-off plates. This got me confident enough to give my turbo idea a go.

I upgraded the RB26 T25 turbos in a pretty well trodden pattern. Steel turbine wheels and replacement billet compressor wheels. The sizes are pretty much as per factory, which puts them very similar to the original HT12's.. A little more exhaust flow, and a slightly larger compressor wheel. I used a CNC lathe to carefully map out the geomerty of the replacement wheels, and after a HEAP of measuring, generated some tool paths and machined these profiles into the OEM compressor and turbine housings. I had to make up a few other bits to get the housings to fit on the garret CHRA's, but nothing too stressful. After getting most of the way through this part of the project, I discovered that there is a guy in the US that does this swap too, but once again the price is pretty high, well out of my budget.

The turbo swap is almost complete, The charge piping is modified and fits again, same story for the water cooling and oil feed lines, I just need to weld some new flanges on the oil drains and it should be that part of the job complete.

While I had the car at my last place of employment, the area was hit by a pretty major earthquake, and the cieling in the workshop my office and car were in came down. No substantial damage, but many, many little dings and scrapes. My insurance company is really great, and just told me to get it sorted by someone I trusted. I stripped all the trim out myself, so I could avoid any broken clips and future rattles, but had a professional remove the front and rear windscreens. It then got a lot of paintless dent removal done, and some body work on the nastier dents, followed by a complete re-spray in the original Chaste White.

So, this is pretty much where I'm up to. The motor is sitting on the stand, almost all back together except for the turbos. I need to get that back in place, build a new wiring harness for it (the old one way just a little past it), build a better intercooler that fits in the stock location, sort a decent, but hopefully quiet exhaust, and it'll be a runner again.

I got given a Power FC for it, and I've purchased a datalogit to go with it to get it running again, but I think I'll try out a couple of different ECU's and see how hard they are to get to run the OEM twin turbo setup. Should be fun times ahead, as its just so, so close to being back on the road again :-).

I've told her that if she gets it running, she's more than welcome to drive it. No luck yet.

Attached Files

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