Building a supercharged Exocet

[wesimmo]

I thought some people might be interested in my midlife crisis project....

I had an NB MX5 Sport which was the ideal basis for a quicker MX5 for a bit of B-Road and track fun, it has an LSD and bigger brakes as standard so seemed ideal for enhancing the power a little bit.

The "quicker" came about via this..

"

Which resulted in this...

However the rust apparent under the bonnet wasn't just surface rust and I got an advisory on the last MOT, the chassis rails are scrap. At this point i started looking at restoration costs but then stumbled across the Exocet and a silly plan was hatched with the aim of 400bhp per ton in a great handling package.

I'm hoping to pick my chassis and parts up soon though there's some work to be done before I'm really ready for it.

After a day or so on my own, having done next to no car maintenance before, I'd got this far...

I then got a mate round on Saturday for a few hours and we had a good go at the engine bay, most of the ancillaries are largely disconnected or removed and we've got the loom pulled through into the cabin.

Amazing learning curve so far, but starting to feel more confident that I/we can pull this off!

I then managed another hour after work last night.

 

[wesimmo]

Keeping an eye on this

What charger is that?

Rotrex, nice little unit, runs cooler than a normal supercharger, comes with an independent cooling and filtration system.

I think i can drop a pulley size for a bit more oomph, if the car comes in at 650kg, I'll need about 260bhp for the 400bhp per ton, might be doable.

Or go big on an engine build and see if i can run a turbo back there too for dual charged stupidity.

 

[wesimmo]

Dis gon be gud

We'll see, I've never even changed brake pads before....

I'm treating it like my first PC build, take one apart to understand it and then rebuild, it's just a little more involved.

I'm drawing diagrams of how the charger and custom ECU were built into the OEM bits and labelling up the loom as i go.

 

[wesimmo]

So the MX5 is the donor for the exocet? I'm interested as I've got an MX5 that's starting to become more rust than car.

Less than that really.

You basically strip and disconnect the body from the suspension and submount and then lift it off with an engine hoist.

Most people then strip the suspension etc down, rebush and powder coat, but you dont have to.

Then you bolt a pre-assembled tubular chassis to the MX5 "skate", add the body work with supplied rivets etc, run your brake / fuel lines and electrics down the tunnel, which comes as a sheet of metal to be cut to shape.

The loom you just coil up the bits you don't need and put in a tray on the bulkhead.

I'm having to remove AC, PAS and probably I'll take the ABS out too.

Hopefully having already got a Megasquirt 3 ECU i shouldn't have too many issues with doing so.

 

[wesimmo]

Very interesting i'd quite like to do something like this. Looks like this retains the OEM suspension though, won't that be all wrong for a car of half the weight afterwards?

Yeah that was one of my concerns, especially as I'm running coilovers.

Worst comes to the worst, I get some new springs, the coilovers are something daft like 42 way adjustable on damping so should be able to find a decent setting.

Still, plenty of people run standard suspension and the reviews are pretty comprehensively positive so it can't be all that bad.

 

[wesimmo]

Looking forward to seeing what the finished product is here.

You might see and hear it in the flesh, Northumberland is where I'll be spending a lot of time in it!

I wouldn't want to rejig an OEM harness for the MS, Just make a new harness from scratch, surely much simpler that way? I'm only running a MS2 v3.0 with wasted spark and batch fired injection though and my donor car didn't have a harness

Everything is already hooked up to the MS3 so I just want to get it fired up first and then think about stripping the loom back, possibly.

Will you need to swap the rack to a non-powered one or can you just de-power the one you have? I remember people going through a big process to de-power a powered rack. Does the same go for the ABS?

Interested to see how the conversion goes. The skate would be simple to strip down to seen a few in that state, I guess the main headache will be the wiring. I'd be tempted to build a scratch loom but then if this was me I'd be stripping, cleaning, painting and refreshing everything along the way and would never get it done

Yeah you convert the rack, not sure about the ABS yet, need to do some research on that front.

The other thing I need to consider is the supercharger runs off the same belt as the PAS so I need to work out whether it's just a case of removing the PAS pulley and using a shorter belt to drive the charger.

With regard to stripping the skate, I'm torn between doing it as I build the chassis up and getting the bits sent off for sand blasting and powder coating while I run brake lines etc or waiting.

Realistically it's going to be off the road for a few months each year, the MX5 was surprisingly usable all year round but this not so much, so I'll have time to do a refresh then. I am very impatient and want to get it IVA tested asap!

 

[wesimmo]

Managed to get another few hours on it today.

Engine loom is now tucked away out the rain under the bonnet having been disconnected under the dash.

Rear loom, roll bar, boot and petrol cap release mechanisms removed.

Main loom removed, dash removed, doors removed.

Though the garage i had spent weeks clearing out is starting to get full of MX5 again....

 

[wesimmo]

How much weight do you save by going this route?

Going by the doors and dash I had to lift into the garage, loads!

I think it'll be about 600-650kgs by the time it's done.

 

[wesimmo]

Interesting build! Good luck with it.

I bet you’re learning a lot, fast?

Thanks, and yeah it's a steep curve alright!

But it is just like building a PC to be honest. I learn more easily from just breaking things down and understanding how they work rather than reading or watching. I built my first PC from scratch without much reference material by taking my old one apart.

Of course time will tell whether this turns out ok, there's a lot more bits to plug in!

 

[wesimmo]

So I ordered some new toys for the next stage, getting underneath and removing the sub frame from the body so I can lift the body free.

I've got a 400nm impact wrench and angle grinder on the way with a big battery and charger. The tools and charger arrive tomorrow, the battery on Friday. Looks like I'm stuck doing a few little jobs until the weekend unless a 138k mile MX5 that's lived near the North East coast actually comes apart easily....

 

[wesimmo]

Yep, it's the Ryobi.....

TBH I did wonder whether 400nm would be enough. I'm only hoping that the fact I've had coilovers put on, the clutch changed twice and alignment done several times since I had the supercharger put on means that the bolts aren't as bad as they might be.

If they're that bad that I can't get them out with the Ryobi I'd probably want to replace them with shiny ones anyway, it's not like they're hidden under any bodywork on this build so I kinda want to keep it smart looking...

 

[wesimmo]

You shouldn't have too much issue, the worst bolt I've ever had to try and undo was the rear PPF bolt that has the bushing in the bottom side.

18v DeWalt impact gun wouldn't touch it. Ended up with a 24" impact bar with about 8 foot of bar on the end to crack that one loose

I've got a mate helping who works on hydraulics for plant machinery and did 10 years as a mechanic so he's got a pretty good selection of tools on his van, hopefully we'll get it apart somehow.

As I say though, even if I have to angle grind some bits off, I haven't got the chassis yet so I will probably end up dismantling the skate and get all the bits blasted, coated and rebushed so buying a few bolts here and there, even if they're half decent second hand ones to refurb won't kill me.

 

[wesimmo]

Cheers mate, will do!

 

[wesimmo]

Been a bit of a wait for the weather and help being available, but some serious progress made this weekend.

It was a surprisingly straightforward job, 8 bolts at the front, 6 at the back, make sure everything is disonnected, or cut off bits that you realise you haven't disconnected when you lift the body and know you're making fuela nd brake lines up anyway..

Next job, strip the suspension and sub frames down and send them off to be blasted, coated and re-bushed.

 

[wesimmo]

Well my casual "strip the suspension" comment was optimistic...

Apparently North East living doesn't suit a rust prone car...salt in the air summer and winter causes carnage with suspension bolts rusting to hell....who'd have thought?

Sheared both the bolts for the ABS sensor on one side and rounded off the coilover bolt.

However a quick test with the blowtorch usually used for cooking soon proved the point and heat is the solution, so a proper blow torch and rounded bolt sockets are incoming.

 

[wesimmo]

great work. doing it all in a single garage too? makes it seem a moderately do-able kit... (apart from all the rusted bolts...)

It's not quite a single garage, it's a townhouse and we use the garage to get in and out the house day to day. To the right is a bit more space at the front of the garage but the back is taken up by a toilet.

I suspect space will be at a premium when I've got the new chassis and body parts in there too...

 

[wesimmo]

You've got much more patience than me I wouldn't be removing the old suspension to repaint it, I'd just start bolting on the new kit

That was how I started but the more I get into it the more I want to do it properly now and not have to refurb it at some point, the bushes are 138k miles old....

That and I haven't got the chassis yet anyway so may as well use the time.

 

[wesimmo]

mk1 and 2 mx5, so i think you're golden, according to your signature pic...

used to have a mk3.5 and I've been itching at getting another for a weekend car, but getting a 3.5 would stop me for being able to exocet it... guess I'll watch this...

By the way, I think MEV showcased their MK3 kit at the Stoneleigh Kit Car Show last weekend.

 

[wesimmo]

Well I've not updated recently, mainly because there's not been much progress!

A month to the day after I got the body off I managed to remove one side of the rear suspension.....

Seriously, don't try this on a very rusty MX5, every bolt has been days of heat, penetrating fluid, 3 ft crowbar and 2ft breaker bar to get the nut off.

Even then it took another round of swearing and pain to get the bottom bolt out the lower wishbone, it was seemingly welded to the bushes and so wouldn't turn or even hammer out.

The kit is ready though, just need to break the suspension down even more to make room in the garage.

 

[wesimmo]

Yeah I bought a Ryobi for the job, bbu that ain't up to it....neither is a 18v Snap On I borrowed.

Essentially to break the nuts off you need a big bar on a 15 year old MX5 that's lived near the sea...