Silly Honda-powered MX5 track toy
Discussion
I haven't shared this project on here for some reason so here goes...
A little (lot of) pre-text; I had modified Honda CRXs that were track-biased in their modifications for years but like far too many folk never made it to the track. I then had an S2000 for a while before being taken ill in 2012, thankfully I recovered and the illness gave me the impetus needed to make sure I finally got on track and did more of what I enjoy best – driving!
The S2000 was sold, I bought a mk1 MX5 as a track car and in Feb 2013 I did my first proper trackday at a slightly snowy and wholly intimidating Cadwell Park. I used the little 1.6 MX5 lots on track over the following 18 months, learning to drive and improving the car as I went along. The final iteration of the little terrier was a shouty, naturally aspirated screamer, with a rebuilt bottom end, modified top end and lovely Jenvey-shaped cherries on the top. It was such a sweet little car to drive on track and embarrassed plenty of much ‘faster’ machinery. After all of the improvements and with a still modest 160-ish bhp, the engine was the weak link, so I looked into the various options for further power hikes.
I decided that the further potential improvements available through NA tuning were well and truly into the realms of diminishing returns so that wasn’t an option. Turbo and roots-type supercharging are both fairly common in MX5 circles and deliver excellent gains, but they wouldn’t work for me as I wanted to retain the character of the original car. You had to work hard to get the most out of the car, keeping the engine singing at the top of the rev-range, with the FI options available and torque-rich delivery they would bring, the driving experience would be a very different one.
So an engine swap would be necessary and there are plenty of options! Perhaps the most common swap, and one that I seriously looked at is the KL V6 Mazda engine – it’s a compact 2.5l vee that can make 180bhp without much fuss and promised 220bhp+ with some well thought out improvements. These improvements would come at a fair cost through and I decided that it wouldn’t be cost-effective. Of course, when you think of high-revving, naturally aspirated engines, Honda lumps are usually the first to mind but there is very little precedent for fitting them in MX5s. Once you get past the misinformation about the rotation of the engines (F and K), you realise that there aren’t any bell housing adapters for the Mazda gearboxes and the engines themselves are too big to fit behind the steering rack.
In the end I decided that I would save up for the engine conversion whilst enjoying the car as it was for another year or so. There were whisperings in the US of some parts that would allow me to use a K20 or derivative thereof so did some research, put spare pennies aside and tried to be patient.
In the meantime, whilst being patient, I saw advertised a working F20-converted car and the rest as they say, is history.
It had been built as a road car and there were quite a few things that weren’t quite right or needed changing for the track but the conversion itself was done properly with extensive modifications to scuttle, bulkhead and transmission tunnel to accommodate the bigger Honda engine and gearbox, mated neatly to the Mazda rear end. It was quite a punt really and an expensive one at that, but I thought it could become a unique and enjoyable track car.
Without a money-tree in the back garden the previous MX5 had to be broken and sold off in parts, though we kept plenty of the good chassis bits and moved them over to the new car. In a nutshell the basic plan was to fit swap everything bar the drivetrain from the old car and hope that it would drive in a not dissimilar fashion.
Once back together and freshly mapped by the good chaps at BLiNK Motorsport, the first shakedown was fairly positive – the drivetrain worked perfectly, though there were some handling issues and the day was brought to an early end by a hole in the radiator.
We made few improvements before the next time out at Cadwell, had a great little play with a VX220 turbo, and finally decided that all the work and financial risk beforehand was worth it.
Vid is worth a watch from ~2:45:
https://www.youtube.com/watch?v=43LeENnmOoA
Since then we have done seven more trackdays and slowly tried to improve it as we have gone. Whilst it’s still not perfected, it’s a cracking car and really does surprise nearly everything else on track.
Here’s a video from the last outing at Cadwell playing with a very well-pedalled K20 Elise and Nige Pinder in his mk2 Golf, (brother) Dan driving first, then myself ~5:50 onwards.
https://www.youtube.com/watch?v=VEtY1yA-LKk
I popped the GPS doodah in for a session at Cadwell and a look back at the data shows a low 1:42 on a fairly traffic-free lap, so it’s quite a nippy little thing!
Of course like anything we always want more so I’ve recently bought a HKS centrifugal supercharger kit for it, the challenge is to be able to drive it in the same way on track as I do in its current guise, wish me luck! :drive:
A little (lot of) pre-text; I had modified Honda CRXs that were track-biased in their modifications for years but like far too many folk never made it to the track. I then had an S2000 for a while before being taken ill in 2012, thankfully I recovered and the illness gave me the impetus needed to make sure I finally got on track and did more of what I enjoy best – driving!
The S2000 was sold, I bought a mk1 MX5 as a track car and in Feb 2013 I did my first proper trackday at a slightly snowy and wholly intimidating Cadwell Park. I used the little 1.6 MX5 lots on track over the following 18 months, learning to drive and improving the car as I went along. The final iteration of the little terrier was a shouty, naturally aspirated screamer, with a rebuilt bottom end, modified top end and lovely Jenvey-shaped cherries on the top. It was such a sweet little car to drive on track and embarrassed plenty of much ‘faster’ machinery. After all of the improvements and with a still modest 160-ish bhp, the engine was the weak link, so I looked into the various options for further power hikes.
I decided that the further potential improvements available through NA tuning were well and truly into the realms of diminishing returns so that wasn’t an option. Turbo and roots-type supercharging are both fairly common in MX5 circles and deliver excellent gains, but they wouldn’t work for me as I wanted to retain the character of the original car. You had to work hard to get the most out of the car, keeping the engine singing at the top of the rev-range, with the FI options available and torque-rich delivery they would bring, the driving experience would be a very different one.
So an engine swap would be necessary and there are plenty of options! Perhaps the most common swap, and one that I seriously looked at is the KL V6 Mazda engine – it’s a compact 2.5l vee that can make 180bhp without much fuss and promised 220bhp+ with some well thought out improvements. These improvements would come at a fair cost through and I decided that it wouldn’t be cost-effective. Of course, when you think of high-revving, naturally aspirated engines, Honda lumps are usually the first to mind but there is very little precedent for fitting them in MX5s. Once you get past the misinformation about the rotation of the engines (F and K), you realise that there aren’t any bell housing adapters for the Mazda gearboxes and the engines themselves are too big to fit behind the steering rack.
In the end I decided that I would save up for the engine conversion whilst enjoying the car as it was for another year or so. There were whisperings in the US of some parts that would allow me to use a K20 or derivative thereof so did some research, put spare pennies aside and tried to be patient.
In the meantime, whilst being patient, I saw advertised a working F20-converted car and the rest as they say, is history.
It had been built as a road car and there were quite a few things that weren’t quite right or needed changing for the track but the conversion itself was done properly with extensive modifications to scuttle, bulkhead and transmission tunnel to accommodate the bigger Honda engine and gearbox, mated neatly to the Mazda rear end. It was quite a punt really and an expensive one at that, but I thought it could become a unique and enjoyable track car.
Without a money-tree in the back garden the previous MX5 had to be broken and sold off in parts, though we kept plenty of the good chassis bits and moved them over to the new car. In a nutshell the basic plan was to fit swap everything bar the drivetrain from the old car and hope that it would drive in a not dissimilar fashion.
Once back together and freshly mapped by the good chaps at BLiNK Motorsport, the first shakedown was fairly positive – the drivetrain worked perfectly, though there were some handling issues and the day was brought to an early end by a hole in the radiator.
We made few improvements before the next time out at Cadwell, had a great little play with a VX220 turbo, and finally decided that all the work and financial risk beforehand was worth it.
Vid is worth a watch from ~2:45:
https://www.youtube.com/watch?v=43LeENnmOoA
Since then we have done seven more trackdays and slowly tried to improve it as we have gone. Whilst it’s still not perfected, it’s a cracking car and really does surprise nearly everything else on track.
Here’s a video from the last outing at Cadwell playing with a very well-pedalled K20 Elise and Nige Pinder in his mk2 Golf, (brother) Dan driving first, then myself ~5:50 onwards.
https://www.youtube.com/watch?v=VEtY1yA-LKk
I popped the GPS doodah in for a session at Cadwell and a look back at the data shows a low 1:42 on a fairly traffic-free lap, so it’s quite a nippy little thing!
Of course like anything we always want more so I’ve recently bought a HKS centrifugal supercharger kit for it, the challenge is to be able to drive it in the same way on track as I do in its current guise, wish me luck! :drive:
Thanks a bunch gents! And only one comment about my silly wing! 
The wing is a case of function over form and proved its worth in back to back testing - I'm making a video about it at the mo so will share once done.
The F20 engine has a book power figure of ~235bhp, mine made 190bhp at the hubs which is a little more than most S2000s on the same dyno. For a comparable figure, I would imagine it would make 240-250bhp on a typical dyno at the flywheel. I'm not suggesting transmission loses are any where near that high, it's just for a sense of comparison.
The wing is a case of function over form and proved its worth in back to back testing - I'm making a video about it at the mo so will share once done.
The F20 engine has a book power figure of ~235bhp, mine made 190bhp at the hubs which is a little more than most S2000s on the same dyno. For a comparable figure, I would imagine it would make 240-250bhp on a typical dyno at the flywheel. I'm not suggesting transmission loses are any where near that high, it's just for a sense of comparison.
Thanks for generous comments!
It weighs 980kg in its current guise, for comparison my 1.6 mk1 track car before it was ~925kg with a simple roll bar rather than the rear cage and door bars.
I doubt there are many S2000s that are under 1150kg so a sizeable difference.
Air intake has seen various iterations, supercharger will change things again though plans are afoot for a direct feed with that.
It weighs 980kg in its current guise, for comparison my 1.6 mk1 track car before it was ~925kg with a simple roll bar rather than the rear cage and door bars.
I doubt there are many S2000s that are under 1150kg so a sizeable difference.
Air intake has seen various iterations, supercharger will change things again though plans are afoot for a direct feed with that.
Edited by Matt Scarbro on Thursday 15th October 11:52
Crusoe said:
Missing some cold air induction or just me looking at that photo wrong? Any idea of weight, seen quite a few track s2000 builds but always hard to get the weight down anywhere near 1000kg guessing this is a bit under?
Re the S2k, am I right in saying you'd need to lose circa 300kg in order to get to the 1000kg mark?Gassing Station | Readers' Cars | Top of Page | What's New | My Stuff