MX5 Donor, Using as a Donor/problems/solutions/advice Info

[HandyAndy]

A great suggestion has been put forward by forum member "Johno" to have a dedicated MX5 Donor page on the forum, as the Sierra is getting a little thin on the ground & as the current "Book" is written around using a Sierra then this thread will hopefully be a source of information for any current or future builders using the MX5 as a Donor.

There are currently some great builds in progress using the MX5 & all have their own "Build Threads" so, this thread will be a source of helpful tips / advice / solutions of using the MX5 which may hopefully help all current builders & hopefully encourage any future builders of a Roadster that may possibly think twice about a build due to a shortage of Sierra,s to take the plunge & build with an MX5.

So......Over to you guys who are or will be using this alternative Donor .

cheers
andy

[Johno]

Hi Andy,
Looks a bit quiet on here so I think I will start the ball rolling... (come on guys form an ordely que)...LOL
I asked Andy to put up a page to help out new members going down the MX5 route (plus ongoing builds) so lets not let him down.
Sometimes it's hard to pick out the info you need from this forum for specific related builds so lets put together information on this page for sound advice for new converts to the MX5.

Well here's my first two pence worth.
A good place for information regarding the MX5 for a Haynes/Locost build is Keith Tanners Seven build.

Just Google the above and you wil find over 1400 entries of all aspects of his build.
Well worth a look....

Johno

[Dualist]

Brilliant, can you sticky this then please.?
I'm going the mx5 route so will need all the help I can get and would need to find it easily.

[PorkChop]

Some pointers about donor choice, or things to look out for if you're buying parts piecemeal rather than a complete donor.

All the 1600 and 1800 parts are interchangable to an extent. For example, you can run a 1600 engine and gearbox with a 1800 diff. You would need a 1800 prop and drive shafts to suit the diff. A 1600 engine will fit a 1800 gearbox.

Apparently (I don't know if this is true or not) but the 1600 gearboxes and diffs are slightly weaker than their 1800 counterparts.

A common upgrade for the 1600 engine (especially if tuned) is to fit the 1800 flywheel and clutch.

You can tell the 1600 and 1800 apart by looking at the cam cover - the 'Mazda 16V DOHC' lettering is raised on a 1800, sunk on a 1600. The 1800 has 'BP' cast into the block on the exhaust side.

The 1800 comes with bigger brakes as standard all round. Mark 2 Sport brakes are bigger still.

Early driveshafts are bolt on (and the PCD is different between the 1600 and 1800). Later driveshafts are push on (and I believe are still different between the 1600 and 1800).

There were several wiring revisions over the course of the mark 1's life.

Early 1600s ('short nose') engines had crank problems. Later long nose engines are fine. They can be identified by counting the number of slots on the crank pulley. The short nose has 4 slots, the long nose 8.

Any imported (Eunos) 1600 engine will be 115bhp, as are UK engines of the same era. The JDM 1600 was discontinued when the 1800 was introduced. The UK 1600 was then detuned to 88/90bhp at this time, so any later UK spec 1600 would be the 90bhp version.

The OEM alloys are very light for an OEM wheel. You would need to spend a significant amount of money to get lighter aftermarket ones.

A mark 3 MX5 gearbox will fit the Ford Duratec apparently

The mark 2 6 speed box is rumoured to be stronger than the mark 1 5 speed.

[Big Vern]

Originally Posted by PorkChop

Some pointers about donor choice, or things to look out for if you're buying parts piecemeal rather than a complete donor.

All the 1600 and 1800 parts are interchangable to an extent. For example, you can run a 1600 engine and gearbox with a 1800 diff. You would need a 1800 prop and drive shafts to suit the diff. A 1600 engine will fit a 1800 gearbox.

Apparently (I don't know if this is true or not) but the 1600 gearboxes and diffs are slightly weaker than their 1800 counterparts.

A common upgrade for the 1600 engine (especially if tuned) is to fit the 1800 flywheel and clutch.

You can tell the 1600 and 1800 apart by looking at the cam cover - the 'Mazda 16V DOHC' lettering is raised on a 1800, sunk on a 1600. The 1800 has 'BP' cast into the block on the exhaust side.

The 1800 comes with bigger brakes as standard all round. Mark 2 Sport brakes are bigger still.

Early driveshafts are bolt on (and the PCD is different between the 1600 and 1800). Later driveshafts are push on (and I believe are still different between the 1600 and 1800).

There were several wiring revisions over the course of the mark 1's life.

Early 1600s ('short nose') engines had crank problems. Later long nose engines are fine. They can be identified by counting the number of slots on the crank pully. The short nose has 4 slots, the long nose 8.

Any imported (Eunos) 1600 engine will be 115bhp, as are UK engines of the same era. The JDM 1600 was discontinued when the 1800 was introduced. The UK 1600 was then detuned to 88/90bhp at this time, so any later UK spec 1600 would be the 90bhp version.

The OEM alloys are very light for an OEM wheel. You would need to spend a significant amount of money to get lighter aftermarket ones.

A mark 3 MX5 gearbox will fit the Ford Duratec apparently

The mark 2 6 speed box is rumoured to be stronger than the mark 1 5 speed.

Little can be swapped between 1600 and 1800 engines but they do both fit in the same 'hole' and fit on the same gearbox.

1600 diff up to 94 is 6" crown wheel from 94 all diffs 7" crown wheel and essentially the same as RX7.
7" naturally stronger than 6" but both are stout. 6" are open or the unpopular VLSD, 7" available as open or with Torsen type 1 or 2.
Three different types of driveshaft depending on the diff you have so get the driveshafts at the same time to go with the diff.

MK2 gearboxes are 'better' than mk1 in that the mk1 is intentionally noisy but this proved unpopular and the leaky remote change was redesigned but both are equally stong as they came from the B1600 pick up.

Clutches - If running a tuned 1600 N/A engine then avoid the heavy 1800 flywheel better to use a H/D 1600 clutch. I'm using a 1600 flywheel and clutch on my nearly stock 1800 with no problems.
If turbo'ed then use the 1800 flywheel and MX6 clutch unless running mental amounts of power

5 speed boxes have better ratios that the 6 speed and in something like the haynes roadster first in the 6 speed would be pointless. Just extra weight to carry around and as its bigger, more of a squeeze on footwell space.

Brakes - Mk1 1800's have bigger front brakes, Mk2 1600 and 1800 had the MK1 1800 brakes and bigger rears, MK2.5 had bigger fronts again and then there were bigger rears for some special editions.

Wheels MK1 all 14" MK2 15" MK2.5 16" mk3 17"

Mk3 MX5 does indeed use the duratec engine as it was part developed by Ford and Mazda. (Well Ford does own part of Mazda)
So a Mondeo engine can be used but a mazda flywheel clutch and starter will be needed. I have a MK3 6speed if anyone wants to make me an offer?

MK1/2 parts Hardly anything interchanges with the MK3's. The MK3's all different, being based around the RX8.

[chrisponter]

The 1.6 inlet manifold is bigger making it harder to fit it under the bonnet, but people on here have managed it.

+1 on Johno's point about Keith Tanners book How to Build a Cheap Sports Car, it's just about how he managed to overcome all the problems in his build. And his contact details are in the back, there's not much he doesn't know about taking apart an MX-5 and he will answer you if you send him an email.

[HandyAndy]

Originally Posted by Dualist

Brilliant, can you sticky this then please.?

Consider it done

Great to see some very helpful info being posted, I,m sure this thread will be a great source for all MX5 donor builds....

cheers
andy

[Johno]

Hi all,
Some good info there guys... . Thanks for helping out with the page to get it going and thanks to Andy for making it a Sticky.
Well I'm going to keep it short and sweet. Here's a guy from the good old US doing a Haynes Roadster the American way.
http://www.locostusa.com/forums/view...hp?f=35&t=8967

Some very interesting ideas there for a different approach to the car.
Have a look and see what you think...

Johno

[vmax1974]

Got the rear subframe dropped down to the floor today but the front subframe has got caught up on the threads

As far as I can tell all the groundwork to removing the subframe has been done

Have I missed anything why even bashing the subframe with a length of wood and a sledge hammer it just wont budge

[fangorn]

This is the way I will be going.I have the steel and a MX5 donor. Once I tidy up my work area and make a build table I'll be into it!! It is great to have a MX5 area.Sierras are Dodos here in New Zealand.