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SS1 MX5 conversion....hopefully

Posted: Mon Apr 01, 2019 11:12 pm
by Jester007
Good evening all,

Having spent the last few months giving the SS1 a once over, new crank oil seal and usual servicing its high time she rolled out of the garage. Unlike some of my previous rolling resto's (that never ended up rolling) I've figured I need to get at least 1 year of fun out of her.... especially given she flew through the last MOT.....That said.....I have a cunning plan..... that I'm hoping you lot will praise and/or pick holes in (I'm looking for honest feedback).

I've managed to bag a very cheap....very rotten....but low milage (50k with good service history) Mazda MX5 1.8 VVT that I am collecting this weekend. So you can probably see where this is going.
The plan in the late part of this year is to take the SS1 off the road and begin an MX5 engine/gearbox swap.

Have any of you attempted something similar? If so, what were some of the notable pitfalls you hit? Do you think I'm mad? :w

From the limited pre-research I've done the most immediate obstacle is swapping the ECU for an MS3 (version 3 for VVT capability) - I'm not overly keen on transplanting the entine MX5 loom as I dare say the stock ECU won't be best pleased with the lack of airbags, HVAC, door solenoids and a whole host of other things it will throw error codes back on. My immediate thought with using the MS3 is to take the engine loom of the MX5 and "feed" the MS3 with sensor data from that, using a nominal 12V pickup from the SS1 loom to provide the power to the MS3/Engine Loom. An abstract statement I know, but I'm in uncharted territory.

I'm under no illusion this will take some patience and a LOT of time...but nothing good was ever easy....and a reliable 146bhp is a very tempting prospect in an SS1.

Anyhow, thats enough rambling, roll on summer and a happy year of SS1 motoring...winter is coming.... :D

SS1 MX5 conversion....hopefully

Posted: Mon Apr 01, 2019 11:31 pm
by scimjim
I’ve mocked up a 1.8 and it just needs the crossmember cutting out (the one that the K series Sabre doesn’t have) - engine mounts need a couple of inches adding each side to hit the Ti mounts (which you won’t have unless you start with a galv SS1). Non VVC loom is much simpler. Even contemplated fitting the ABS. I’ve also fitted the complete dash and centre console - looks like it was made for it :D

Unfortunately, it’s too far down the list of projects to put any more time into but you’re welcome to pop down and look at it some time?

SS1 MX5 conversion....hopefully

Posted: Mon Apr 01, 2019 11:31 pm
I believe Jim King and Phil Howard have mocked this up as basis for an auto conversion

SS1 MX5 conversion....hopefully

Posted: Tue Apr 02, 2019 4:36 am
by philhoward
This could get very confusing as I’ve been having an email conversation with another Phil who’s looking at grafting a lot of MX5 into an SS1..

Certainly (as Jim says) the Mk1 bits seem to want to live on in an SS1. Seemed so very bizarre when even the dash fitted!

SS1 MX5 conversion....hopefully

Posted: Tue Apr 02, 2019 6:25 am
by scimjim
I doubt the ECU will stop/limit the engine if it’s missing HVAC and airbags - but there is an off the shelf solution here?

Having done the change to zetec and K series, I think the later mx5 Engine will be much harder? The earlier engines are said to be stronger and coupled with a with lower CR, will react better to forced induction (which you’ll need to consider when you decide you need more power :D )

SS1 MX5 conversion....hopefully

Posted: Tue Apr 02, 2019 7:06 am
by rkclodhopper
Make sure the propshaft rotation direction the same, if not your into a diff change. I think the Honda S2000 engine/drive train goes the wrong way.

SS1 MX5 conversion....hopefully

Posted: Tue Apr 02, 2019 1:23 pm
by Jester007
Thank you all so far for the feedback - unfortunately I'm committed to buying the 1.8 VVT 2.5 now, it was far too cheap to let it slip away - to be honest at £390 its worth it alone for the leather seats engine and gearbox!

Thanks Jim for the kind offer to view your mock up - (just FYI I do have a galv model - it was the one for sale on here that was a school project D542RJO) - I will most certainly take you up on that in the coming weeks - I'll PM you nearer the time to see when you are free. Also, thanks for the link to the ME221 - looks like a perfectly viable alternative to a Megasquirt and will still allow me to do away with the troublesome immobiliser. So it maybe the case I go for a Mk1 loom, Mk1(dumb)alternator and this ME221 with the req mods to the Mk1 loom. No danger of me wanting Force Induction at this time :wink:

I guess my initial thought was to have my cake and eat it - i.e retain the SS1 dash and general look and feel (excluding the Clocks of course as I know the MX5 speedo output is a gear to plug not cable) - but if the Mk1 MX5 dash is a fettled fit then I may just jump to that - especially if I pick up a Mk1 loom. Certainly makes it easier when reusing switches etc.

The beauty of these MX5's is there are tons of spares and they all seem dirt cheap.

Thank you all again :D

SS1 MX5 conversion....hopefully

Posted: Tue Apr 02, 2019 1:35 pm
by Jester007
Oh and thanks Richard! Something in my impetuousness I overlooked, but its counterclockwise I believe so I think we're all good.... other than getting the prop adjusted - I'll be interested to see the difference in diameter - if nothing else I can use the SS1 and MX5 props to fashion the correct couplings....I've been waiting for an excuse to drag the TIG out :wink:

SS1 MX5 conversion....hopefully

Posted: Sun Apr 07, 2019 8:32 pm
by Jester007
So, the MX5 has made the trip from sunny Blackpool to Middle Earth. It appears the coastal climate has not been kind to it - rot pretty much everywhere you can see, and a lot more places you can't (sorry, the picture doesn't do that statement justice) - its abysmal and a sad sight on a car that has in its short life had a reasonable amount of money spent (full stainless system, sticky Yokohamas , service history points out high quality oils and waterless coolant) .

But.... the engine is absolutely perfect, runs like a sewing machine - gearbox nice and tight, , trim is pretty much unmarked too. The chap I bought it from had a very interesting workshop - just a retirement hobby for him but when you spot a Renault 5 Maxi and a half built 6R4 in the corner (can't vouch for if it were genuine but the engine was defiantly the Rover V8 minus 2 cylinders), a quick "pick up" turns to an hour and a half natter before leaving :D

I've done some preliminary measuring for the dash and centre console and it doesn't look a million miles away from fitting the SS1 - a rough measurement had the MX5 dash 15 inches deep into the cab, opposed to the SS1 being around 10/11 inches - width was around 2 inches shorter on the MX5 dash - I don't know why but I expected the MX5 dash to be far wider than the SS1.

Also doesn't appear too far out where the gear stick comes through the tunnel. As I say, these are rough measurements as I couldn't wait to start eyeing things up....I'm optimistic!

Furthermore, I'm now back in the camp of transplanting the entire loom including ECU etc over to the SS1, maybe even put the central locking, servo/master cyl & ABS unit onto the SS1.

This particular model doesn't have all the HVAC unit that would need to come with it and I figure it may just be simpler to adapt the SS1 bits to run off of the MX5 loom (lights and pop up motor, an aftermarket fuel pump, wiper motor etc). There are some spare blanks in the MX5 dash that could accommodate extra switches without looking out of place.

As I said at the beginning of this post, I plan to get the summer out of the CVH engine and enjoy the car some before the work starts!