It’s been a little while since we’ve done a proper update on the various cars in the fleet and I can assure you we’ll get round to all of them very soon, but this is just going to focus on the current incarnation of my personal car which the team have dubbed ‘Gavin’.
The previous shell I swapped the remains of Peril into after the crash has now gone off to scrap due to utterly ruined sills, which could have been fixed but would have cost far more than i’d want to put into the car.
This car lasted 18 months, and probably owed me about £300, so no love lost. Its the car that got me back on the horse so to speak but it was always going to be put out to pasture fairly quickly being as it was purchased in the dark, in the rain.
So what’s the plan?
Gavin came to me on the back of a low loader after James and Leigh sauntered off effectively in secret and bought it for me – what top lads. At this point I was very much without an MX5 and it was proving difficult to find one that i wanted. Eunos, 89-92, Clean, Not silver.
Obviously, it was bloody silver. Hey Ho.
But, it was utterly original – the most original one we have ever seen. Completely rust free, too – and i don’t mean it looks rust free, it really is.
The kicker? It’s an auto. Perfect, the Green one (leaf) was an auto to manual conversion before my time – no worries.
So what do you do when you have a new rust free donor car? You strip it to pieces obviously.
Here’s the thing, we never take the time with these builds, our own stuff, to really do the job right or at least to do the cars some serious justice straight away – its always a rush to make it work so we can get to the track, the next event, what have you. The best course of action for this car, considering the entire drivetrain needed to come out anyway – was to strip it to a bare shell.
The next steps were to seal the underside, convert whatever rust is there and put it in a position where it can be driven without deterioration.
This isn’t the best way to do this, its not even the most effective – but it suits what this car needs. The aging underseal was thin and peeling in places, with some areas of bare metal – liberal application of Buzzweld Rust Encapsulator in both brush on and aerosol varient gives the coverage needed.
Next up is Buzzweld WAR which is an underbody coat similar to stone chip, it gives additional protection and turns the underside a nice shade of black. It took 2 large cans to do most of the underside to a reasonable standard but i’d budget 3-4 if doing it again.
The arches were gone over with a satin black paint primarily for looks to touch up any missed areas but this also provides a further layer of protection – I can’t state how good this car is condition-wise (so it’ll be a shame when a sausage kerb or armco has its way with it).
The next step is improving the chassis, with the car completely bare I decided to tackle something I’ve wanted to do for ages and after last years 30c+ llandow event with a hardtop cooking ourselves – heat management was high on the list.
I’ll attack this problem from two fronts;
DODO Mat Hex
This is a Dynamat style material, and proved to be incredibly easy to work with. Lining the entire cabin for the cost of a single roll (£49.99) with some overlapping and a reasonable amount spare for other odds and sods. If I was going to do the boot and door inners this would have been a 2 roll affair – and i might do that later down the line but for now the difficult to access part is done.
The idea here is it’ll not only limit heat into the cabin but also dampen the harmonics of the car hopefully bringing the harsh tones down a little, these cars do get driven to the track and back which is – for us – a big part of the fun.
Engine Bay Heat
Heat management doesn’t get enough attention with most dual duty cars, pure trackday cars will have found the weak points and fixed them – but on a street/strip car rarely do you get the thing hot enough to justify the cost.
With this car the aim is pretty simple, stop the turbo and downpipe cooking the transmission and transmission tunnel – but also the engine bay in general. It’s bad for the driver, passenger and all the systems in the car.
We’ll do this in two ways.
Wrapping the downpipe, using quality products we’ve used before – heatshield products lava wrap. The claimed performance benefits are a bonus if indeed that is noticeable, the massive difference it’s makes to the heat being poured into the chassis and gear box is the key benefit here.
This is a job that I always recommend, if you do anything – do this.
The next step is a little more garish, using Ram Air RAD Gold Heat Reflective tape the aim here is to keep the heat off the chassis and keep it in the air, which we can then extract more efficiently.
The firewall and transmission tunnel will be covered on both the hot and cold sides to maximize the efficiency and the size of roll (£29.99 100mm x 10m) and the chassis rail will be covered on the exhaust side.
After this the next step would be to create a full heatshield for the manifold and hot side of the turbo, creating as much of a differential between the hot and cold sides of the system. For the moment, we won’t be doing that – but as a future improvement we will, however I’d argue that a better solution that doesn’t prematurely deteriorate your Oil feed and water lines would be Ceramic Coating, granted and quite considerable cost.
Turbo blankets in this application aren’t advised, the previous time we ran one on the low mount setup the exposed area leaves an incredibly concentrated area aiming directly at the heater hose which caused issues on the dyno.
The final step improves overall cooling and heat evacuation in general. GC Fabrication Hoot vents.
At a certain point, all high powered track MX5/Miatas need to move to a vented hood of some description, it allows the radiator to work far more efficiently by creating negative pressure in the engine bay, this combined with proper ducting of the radiator and intercooler ensures maximum efficiency. Keeping the engines air feed as cool as possible will also give the system an easier time making the power reliably.
What’s next for the chassis prep?
A few parts from the green car will carry over, a set of Skidnation Frame Rails – pretty much a must-have modification in my book, installing eyelets for the 6 point harnesses at this stage makes life easier too.
A GCR2 Rollbar and door bars, after that the carpet can go back in.
We’ll do a bit of a quick and dirty improvement for the subframes this time around, the budget on this build is super tight so I’m not doing polybushes – if some spare cash comes up I’ll be using it for a set of Whiteline Anti Roll Bars – it desperately needs them.
A quick brush off and paint of the subframes and control arms, checking for premature bushing wear and making sure the ball joints are all serviceable – replacing them with pro forged units if not – and back on they go.
I must admit I’m a little loathed to put the front subframe on before the engine is ready, as I’d rather lower the car onto the assembly to save us messing about scratching paint and denting firewalls.
The 4.3 TorSen differential is in need of help, the pinion seems to be worn and needs to be sleeved as no matter what we did last season it wouldn’t hold oil for very long, as this has been fully rebuilt once before.
Anyway, as of now the list of jobs are;
Rebuild the engine
Upgraded Rings, Bearings, Oil Pump, Rods
Install the subframes
Install the wiring harness
Install the ECU – Ideally high inside the dash
Install the CAN wiring / EGT Box
Install Bonnet Vents
Install / Modify / Improve Exhaust
We’re working on a bolt on 3” system, lightweight, track noise limit friendly.
Refresh the Brakes
Improve Radiator / Intercooler Ducting
Improve Oil Cooler Location
Going into a little more detail with the engine, stock pistons are proven to last above the power levels I’m going to be running – which will be a GT2560R on our low mount manifold, on a 1.6 engine.
This is the same engine I’ve pushed 17psi through in stock form and the recent tear down shows everything was healthy, but I’ve exercised a lot of mechanical sympathy.
The new setup is a hybrid. Using the head from a MK2 1.6 which have solid lifters and more importantly cam and crank angle sensors and what appears to be a far better-designed head port wise, for reference this is a different casting from the early 1.6 engines.
On top of that, we have a 3.2l plenum volume aluminum fabricated intake manifold, which was previously used on Alan Bowker’s 500BHP 1.6 Exocet. Without cams, we won’t be making much use of this setup but the 1.6 intake manifold is quite restrictive.
Power goals? This will flow around 18-21psi at 7200rpm, Ideally I’d like to run this out to 74-7500rpm at a reasonable pressure, 16-18psi. If its much lower than that, we’ll need to look at compressor housing and back pressure of the system to decide what needs changing.
Inevitably the next modification to the engine will be a turbo camshaft of some description, that’ll make far better use of the airflow available.
But this isn’t trying to make world-ending power, the goal is drivability with 250-270 at the hubs, which would be a 45-65WHP increase on the previous setup, the car’s differential and gearbox won’t suit anymore and I’m not intending on moving to a 6 speed / 3.9 just yet.
When will this be back on the road?
The engine should be completed by the end of march, we have a track day to get to at Snetterton on the 9th of April, so, 4 weeks, end of march.
Engine and tuning aside, there’s about 40 hours or so left to get the shell finished up, ECU installed, wiring sorted out and ready to accept the engine. So quite a few long evenings and weekends to make that happen.
We’ll do our best to document and update over the next few weeks.
Thanks for the ride leaf.