MK Sportscars RX5-140 Build

[MK Sportscars USA]

I promised i would do this, so here I am!  

I received my first container from MK back in October.  (PS - I'm the distributor for MK Sportscars in the US)  

Most of the kits were sold to other DIY guys in the US , I still have 1 in stock if anyone is looking. 

Next container full is on order.  Feels good to spread a few of these kits out in the US!

 

I just started building an RX5-140, with a few small upgrades. 

Donor miata was a 6 speed, with LSD and sport brakes.  Engine is a relatively low mileage VVT engine.      

 

Pics below of the staged parts for the build.  

 

  

[MK Sportscars USA]

I bring these kits in with the floor panels installed, as well as the hard fuel lines and brake lines, pedal box and master cylinders.  MK does a very nice job on this, for a very fair price. 

  

Rear suspension and diff mounting.  Fuel tank assembled with miata pump and sender, installed and plumbed. The fuel assembly from the miata gets tweaked a good bit to fit in the tank, and align with the sump at the bottom.  The sender also gets adjusted to operate properly in the new tank.  This was further modified to be a return style fuel system - removing the FPR from the OEM assembly and moving it up front to the engine.  

 

Notice the OEM miata fuel filter mounted on the bulkhead as well. 

 

Axles, hubs, brakes and diff are all from the donor car.  We supply a shortened driveshaft in the kit to accommodate the chassis.  No need to modify an existing one.      

 

Edited December 18, 2024 by MK Sportscars USA

[MK Sportscars USA]

Steering installed.  

Don't worry, that's not the wheel that will be on the car - it's what the donor had - and even came with a nice NRG quick release hub.  

The lower steering shaft is also supplied with the kit - as it is modified from a miata and requires welding - easy just to have MK do it for us. 

The upper steering column is from the donor vehicle.  

Steering rack and rod ends are included with the kit as well.  

 

Radiator is a 55MM core with a 12" fan.  

 

The front brakes are upgraded to wilwoods, and went with some nice EBC coated rotors to finish off the front brakes.  A keen eye will see some Flying miata brake adapters - as I only had the brackets for the smaller miata brake rotors, was nice to have a source stateside to solve the issue.  

 

Edited December 18, 2024 by MK Sportscars USA

[MK Sportscars USA]

Put some tires (tyres) on and gently dropped her on the ground.  

Went with 15x7 wheels, 195 tires all around.  

Did a little prep work on the engine, and slid her into place. Between a forlift, and being able to move the car with one finger, it was really quite simple. Much easier than an "actual" car. 

 

 

I'll update further as the project comes along.  Thanks for reading!  

 

 

Edited December 18, 2024 by MK Sportscars USA

[JohnCh]

Thanks for starting the thread.  I'm looking forward to following your progress!

[MV8]

Nice kit! Thanks for sharing the build.

[S1Steve]

Welcome to the Forum. We like a good build story. The chassis looks very similar to my Superformance S1 . Is the body fiberglass or aluminum panels. It’s going to be fun for the new owner or will this be a demonstration car… Nice build keep us entertained…

[MK Sportscars USA]

Thanks for the interactions, appreciate it.  

 

Body is fiberglass.  Pretty good gel coat finish.  

This car will be traffic blue with a white stripe.  Black front fenders.  

 

This one is for a customer.  

I have my car available as a demo car (K24 honda power, same chassis, though a little stiffer sprung)  

I also have a second build in progress simultaneously - similar car with a turbo added.  This will be sold after it's built and sorted.  

 

I'm setup with the NHTSA as a low volume replica manufacturer - so both of these cars will leave with 17 digit vin numbers and MSO.  Should help the future owners greatly. It was a nightmare getting a Vin for my personal car here in Louisiana.

 

Back to work....

 

 

 

 

 

 

 

 

 

 

[MN7Fan]

Thanks for posting, MK Sportscars has been on my radar. Excited to see they have a formal distribution party in the US.

[MK Sportscars USA]

Not a whole lot to report over the past few days, darn holidays.. LOL

I did get to take my 14 year old nephew out in my car though, I think it may have changed his life.  "The sounds!!"  I think his legs were a little shaky too.  

 

Pics of the fender mounts attached.  These arrive "flat" and are bent to fit the tire /wheel you'll be running.   These are done to the build book specs and fit a 195 tire perfectly.  

But, on a 205 they get uncomfortably close to the tire - so the second car was done slightly differently - just adjusting the bend axis by a few MM. The front fenders will cover a 205 tire, but just barely.  Looks awesome too.  

 

 

 

 

 

[MK Sportscars USA]

Sending these off to be powder coated. 

The holes are drilled in the flats of the uprights to help bond them to the fenders with adhesive. 

The lower ball joint mounting holes did have to be resized a bit, as they were a little too small to fit over the miata stud. 

 

 

Edited December 27, 2024 by MK Sportscars USA

[MK Sportscars USA]

Been a minute since I've updated this thread.  

I am patiently awaiting some parts for the the wiring of this car, but should be here any day and we'll be off to the races again with this build.  We'll be using a standalone ECU and MK chassis harness to wire this car.  Will also be using standard MK gauges instead of the Miata dashboard.  

 

As I stated earlier, I'm working on another car - an RX5 250 Turbo build.  

This car is using the OEM miata harness to power the car and the engine needs - and the miata dashboard for info.  

This is the standard arrangement using the RX5 kits from MK - re using the donor car harness to complete the build.  

I hadn't gone through this process before with the Miata harness - and wanted to share with you guys.  

First - it's time consuming.  And quite tedious.  

Second - you better be pretty sharp on auto electrical circuits and wiring diagrams.

Third - Patience is key, the only way to eat an elephant is one bite at a time.  

 

That said, it is certainly a good solution and a significant cost saving path (if you don't count your time...)

 

Here's a few pics of the progression, first pic is the untouched harnesses from the car.

 

Second is the beginning of the teardown - this part is covered in the build manual, and removes quite a bit from the main chassis harness - but I wasn't happy here, and continued to remove quite a bit more from this harness and the other harnesses from the car.  

I managed to avoid splicing too much, with only 3 solder connections made in total.  

Everything else was re pinned, rerouted, and economized as much as possible.  

 

Third pic gives you an idea of how much is removed from the harness vs. the OEM configuration.  

 

And lastly a beautiful shot of the discarded tangle....

 

 

 

 

 

 

 

[MK Sportscars USA]

Next step is to lay this mess into the car and start the fitting.  Again, this takes a good bit of patience, planning and trial and error for the "best" fitment.  

Second pic compares the OEM engine harness and the "new" engine harness.  

Third is the beginning of the harness routing, trying to group circuits together in the manner that best fits the car.  I ran all engine wiring on the "cold" side of the engine to avoid the exhaust heat.  

 

 

 

[MK Sportscars USA]

More progress.... Lots of zip ties and masking tape wasted.

But starting to get manageable.  

Last 2 pictures are the final layout.  

This does turn into a fairly elegant solution at the end, and makes the miata harness a viable candidate for the job.  

 

Only 6 relays remain (headlights, parking lights, fuel pump, main relay, horn, and fan) plus the flasher.  

Fuse box is under the dash in an OEM like position.

All other components will be nicely hidden by the scuttle and engine bulkhead.  

 

Factory color codes are used throughout, so future modifications should be easy and can be referenced with the miata wiring diagrams. 

 

Overall, I am pleased with the finished harness - but it took me far more hours than I anticipated. 

And it all works!  That's the best part. 

I did swap a turn signal / headlight pin on the drivers side...  And getting the high beam dash indicator to work requires the bulbs to be installed first (Doh!)

But otherwise went off without a hitch.    

 

When I jump back on the RX5140 wiring in the next few days, I'll take some pics to document this option using the MK chassis harness and ME360 ECU / Harness.  Should be far faster, cleaner, even simpler, and add some nice flexibility to the build.  

 

 

 

 

 

 

 

[MV8]

Is there an removable panel from under the bonnet to access the fuses and electronics without removing the cowl? Might be something to add if you ever want a full windscreen. Nice and tidy though.

[MK Sportscars USA]

Standard fuses are in the passenger compartment.

 

Bulkhead panel or scuttle removal are quite simple - even with a full windshield - but I wouldn't expect these items to be accessed too often - relays and main fuses shouldn't fail frequently.  

 

Wouldn't be too difficult to add a removable panel on the vertical wall of the bulkhead panel, certainly a good idea if that is a concern.  

  

Thanks for the nice and tidy comment!

 

[JohnCh]

Very interesting!  By any chance do you have before and after weights of the harness, or the weight of the enormous pile of wires removed? 

 

I'm looking forward to hearing how the other harness goes in. BTW if you didn't see it, there is a current thread with tips on building a wiring harness that might be of interest for the upcoming car:

 

 

[MV8]

4 hours ago, MK Sportscars USA said:

but I wouldn't expect these items to be accessed too often - relays and main fuses shouldn't fail frequently. 

Usually it is whatever they are connected to that fails and blows or damages these components while away from home. These things are easily accessible on the miata, but I admire your optimism.

Edited January 25 by MV8

[MK Sportscars USA]

3 hours ago, JohnCh said:

Very interesting!  By any chance do you have before and after weights of the harness, or the weight of the enormous pile of wires removed? 

 

I'm looking forward to hearing how the other harness goes in. BTW if you didn't see it, there is a current thread with tips on building a wiring harness that might be of interest for the upcoming car:

 

 

Just checked.... 13 lbs  of left over wire, plus probably another pound or two of stuff I've tossed.  

Nice work on the wiring harness build attached!

[11Budlite]

I can add that when I was building the dash and tidying up the wiring on my son's Miata-powered Exocet, I ended removing enough wiring and connectors to fill up a 5 gallon bucket. It was amazing how much wiring there is, even on a very basic mid-90's sports car. So I can definitely see it being over 13 lbs!

Edited January 25 by 11Budlite