Hi all, Paul here. I was on here ages ago and only just signed up again, with a fresh email and access to this new account. Anyway I guess it's long overdue that I made some effort to document the develpoment of my mk1 five.
A couple of summers ago I bought a very clean mk1. Having been advertised as untouched, rust free, with low miles of circa 40k. Allegedly one of the "best examples" MX5 City had seen. So a lovely solid base to work with. The only downside... it had literally nothing on it I wanted. So it was going to be a journey from OEM spec, to OEM+. Ish. Stop giggling Wannabe Yes, there was a little mission creep.
Cheers Rich. I tried Imgur. Far easier to upload the images. However when it comes to inserting images on this forum it crashes 99% of the time. I've tried every variation possible. I thought it may be fun to share the work. Sadly this has quickly turned into a chore. Oh well. If the website gets an update I may try again in the future.
Good call Wannabe... lets skip to the end and save a lot of faff Short version to save me the hassle... it was OEM. Now it isn't. The end.
OK I guess I can manage some basic details...
I upgraded everything on my car and left the 1.8 engine totally alone for two years. All I did on the mild power tweak was a full Racing Beat intake and exhaust system. It may have made 140bhp or so. Soon... it will be between double that and circa 300bhp. All while adding no extra weight. Plus the engine sits further back than a four cylinder, so it should be very well balanced. The bonus is I get to keep the lovely mazda five speed gearbox. According to those with these in USA I wont have to upgrade my shafts either. So that is an awful lot of money and weight saved over say a V8 conversion. This is what I wanted... better sounds, OEM balance and weight, crisp throttle response, no supercharger belt issues or turbo heat or torque issues (for the transmission).
Shall I just ping Wannabe some pics and he can upload them?
This may be the first conversion like this in the UK. Mainly due to the costs and faff required. The engine is a JDM version of the 3.2 V6, imported from Japan via USA to me in the UK. I actually ordered two of these. The conversion kit and all the performance upgrades were also imported from USA. The postage and import tax alone were daft. But when it's all done, it will be unique for the time being. Plus I like the idea of keeping it all Japanese rather than some random Euro or USA engine. A Honda VTEC is a good option for reliability and in keeping with the MX5 vibe. Good revs, sound, response.
This JDM engine is called a J32A. There is an identical North American market version called J32A2. There are other variants both smaller and larger. But these offer the best power to weight ratio. Others have lower power, while some are just a bit too heavy for me. In America you may find this engine in a Honda Acord Type-S. In stock it only had 260bhp as the pathetic cast iron manifold and thin wiggly downpipe is so piss poor. Once those two elements alone are improved you gain 30bhp immediately, according to many.
On top of this I went for: Massive 90mm K-Tuned throttle body, *Holley EFI cast alloy air plenum intake (saves loads of mass and gives 5-7 percent increase alone), ported head intakes / runners, big bore CompTech manifolds designed for this engine, AEM programmable ECU. A lower spec car than this in USA allegedly has 318bhp, according to the tuner. But I will be happy with a dead 300. Fingers crossed. More than enough for a street MX5 to play.
*Removing the mega heavy Honda plenum and replacing it with Holley should bring the engine back down to OEM weight. The kit suppliers say the standard heavier engine adds 4kg to the car.
Tuning... sky is the limit. You can go well beyond 400bhp NA with cams and ITB. Supercharging makes 500-700bhp. Turbo charging makes 1300bhp. On standard bottom end. I have loads of videos of cars racing with these specs if you are interested. Totally pointless of course, but shows how well made Honda engines are. A tad more reliable than Mazda.
The engine has only just been mounted. Today the flywheel is being lightened by an engineering company. Plus an upgraded adaptor spacer is being made. Also the plumbing is happening now. Once those elements are done the gearbox can go back on. The "to do" list is rather long! But some parts include... Getting the Holley plenum on, throttle with custom cnc adaptors on, air intake on, AEM and custom loom connected. Then the big one... getting a new 2.75" exhaust system fabricated from the CompTech headers back. I expect over the next couple of weeks it will be coming to an end.
In the mean time I have emailed a few pics to Paul / Wannabe. If he is kind enough to help you may see some more snaps. I am also sure he will give you some impressions when he gets to drive its nuts off
I imported two J32A JDM engines. Both circa 45k miles in lovely condition. We put all the bolt on goodies on one and kept the other for a spare unit. Unlikely it will ever been required. But best to have it sitting there. With the lowly power I'll be running it will barely be awake compared to many. So it should serve as a reliable long term daily.
I'd read about J32 swaps on miata.net but had no idea there was one in the UK. AFAIK noting was ever sold here with that engine, so I guess yours may well be unique.
So, that Holley intake fits under the stock bonnet? Yum yum.
No way does the Holley fit under the bonnet like the Honda plenum. So there will be a central hole cut in the hood. At least it will be symettrical Ditching the Honda plenum has too many benefits such as: No need to modify the OEM intake, it keeps it all clean and symettrical, removes a lot of mass, removed a LOT of rats nest plumbing, removed dual Honda throttles with additional water cooling, allows far bigger air flow which these engines love, actually saves some labour.
Yes I am fairly sure it may be unique. The kit seller said they have none in Europe when I asked ages ago. I think there is one in NZ. But a fair few in USA. Although many people seem to opt for the poor OEM cast iron Honda manifold or even the Honda ECU Both of these really do strangle the easy potential on offer. So seems daft to not spend a little more. Also there are some low power versions around. Some have the lower spec engines, yet claim they are the J32A or J32A2. Some of these are clearly not, as you can tell from the intake.