From a rotten wreck to smashing the quarter mile in 9sec – what kind of mad scientist lurks behind this Mazda RX-7 project? Only the one that turbocharged his lawnmower.
In our new series, Me & My Project, owner Gavin Bey tells Matthew Macconnell about his Frankenstein Mazda RX-7 and how it now delivers devastating performance.
“I frequently drove past the red RX-7 that I have now back in 2010 on my way to work. It was parked up in a field in Shetland for three years and it turned out that the person that owned it had purchased it, imported it and crashed it. A couple of weeks, however, it vanished. I started enquiring about its whereabouts, Shetland is a small place, so it made things easier, and I eventually ended up talking to the owner.
I wanted to buy it and the owner agreed. I was told £1,000 as it stood but I only had £500 and had to walk away. A month passed and the owner phoned and asked me if I still had my £500; at that point, I only had £200 left. He told me that some of the car’s bits had been sold and that if I wanted the rolling shell that I could have it for the £200. I rocked up with a friend and a trailer and parted with my £200.
Saving up, I bought bumpers and side skirts and was also looking for an engine online. A rotary popped up on Ebay and I had it shipped to Aberdeen; it was a nightmare to get things shipped to Shetland on the ferry, so I collected it from Aberdeen. I finally managed to get the engine running but it was rough, so I bought a tuneable ECU. The car went through an MOT and I had it on the road for a year; it was a simple build at this point.
It remained a rotary for eight years and had been through four engines, two being in the same year – one engine even managed 600bhp. Rotaries are a great concept, but they give owners stress and anxiety whether it will start or whether the air density of the day will melt an Apex seal. My friend then sold me a white RX-7 — it was clean and I had plans to keep it that way as my red one was never about cosmetics — a decision was made and the 600bhp engine in the red car was swapped into the white one.
I now had two RX-7s, one with an engine and one without. Rather than putting a rotary back in the red one, I was pulled towards the reliable Honda K-Series engine and a rusty Honda Civic Type R EP3, donor car, popped up with 160,000 miles on it. The K20 engine came out and I scrapped the shell. The K20 is a tall engine, and I wasn’t sure if it would fit. I made an adapter plate with 10mm steel on my laith, which aligned the crankshaft and gearbox input shaft, and drew a template that would fit the bell housing and the block.
I then contacted CG Motorsport and they made me a twin-plate clutch to a specification I provided, that was bolted onto the standard flywheel and the engine and gearbox were connected. Next, I made an inlet manifold from the EP3 manifold; I was purely learning during this. I’m self-taught and a lot of the information came from YouTube. Next was an exhaust manifold, which was tricky because K20s are front-wheel drive. I bought a heap of tubes online, tacked them together and then fitted a Holset turbo. It was at that point I looked over at my clean white one and thought: “Oh, no… have I just swapped the engine into the wrong car?”
I needed money and one car had to go. The white one was a dream but the red one, which made 500bhp on a dyno, was the one through which I learned so much, so the white one was listed. Rotary owners understand why I swapped the engine but those who have never owned one simply don’t. I started to slowly increase the power but I found it difficult to change gear due to the high-revving K20 engine and the synchros in the RX-7 gearbox – and over time, I chewed through gearboxes.
Someone reached out to me, knowing I had that issue, and advised that a company, called MaxxECU, had an ECU that controlled BMW M3/M4 DCT gearboxes. It got me thinking as these ‘boxes shifted fast – I could have this in the RX-7. Once again, an Ebay purchase of just £600 got me an M3 gearbox and then I bought the MaxxECU Race ECU. I reached out to someone in Sweden who was building a K20 DCT RX-8; they had K20, DCT and adapter plate blueprints. Knowing that I was learning the hard way, he gave me the plans.
An adapter plate was made alongside a spline that comes off the flywheel to the ‘box – no clutch was needed. At this point, I was diving into more advanced territory, learning CAN bus and tuning gearboxes. I drove it for a year and got greedy with power; the K20 then threw a rod. Rather than dropping in another, I noticed the K24 engine had more torque and I bought one for £300.
With some work and a PSR GTX 3584 turbo, it produced 713bhp at 1.7 bar but was capable of circa 800-900bhp at the 2/2.5 bar. The issue that I had was traction – I needed four-wheel drive and noticed the BMW ZF8 gearbox that the xDrive M4 had. I then went a bit mad on Ebay and bought one alongside various other parts.
Next, I reached out to a company to make an adapter plate from the K24 to the ZF8 gearbox – I bolted the engine to the gearbox. There were all kinds of issues such as getting driveshafts through the chassis legs, the geometry was off and the top mounts for the suspension were in the wrong place. Being a £200 car, I took the grinder to it and cut the chassis legs, then I had to make a custom transmission tunnel and fitted the engine to the gearbox.
I had to now fit the front diff which was in the exact position where the engine was meant to be – it looked impossible to do. I then realised the suspension wouldn’t work either. I was over-complicating matters: I fitted the RX-7 lower and upper arms, used Mazda 6 and the RX-7 hubs and welded them together to accommodate a driveshaft hub that could in turn accommodate dual wishbone suspension. I mounted the front differential, fitted the driveshafts and used a short MX-5 steering rack – just to see if things would work and they did.
To control the gearbox, I reached out to a company that produced gearbox ECUs, but the gearbox was from a 2020 car and hadn’t been controlled yet. Soon enough, with the gearbox in and out the car and some additional tinkering – I had four-wheel drive. The car will cover the quarter mile in nine seconds. I look forward to getting it on the drag strip as the time should be closer to eight seconds with the extra grip.
See if Gavin managed it here
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