Right,

So I've been having a think about what to do with my tin-top, (cloth-top actually) its going to be a bugger to sell, as its RHD, and its old and not that valuable anyway (I'm in holland remember.) so one of things i'm thinking about doing is stripping the car for the running gear and replacing the smokey crossflow that is in my seven with the MX5 engine and box.

My reasoning is:

The gearbox is one of the nicest gearboxes i've ever had the pleasure of shifting.

The engine is reliable, and fairly powerful.

I like the characteristics - peak power 6500rpm, but still very drivabe at 1100rpm.

Its easy and cheap to get a good deal more power out of it.

I can run the original ECU, or megasquirt.

Most of the bits should fit out of the box, the zorst and prop will need modification, but all else should just about fit since it already has an induction kit which makes the installation a lot smaller.

I have a spare engine in case it all goes wrong, and it would give me something interesting to play with over the summer in time for installation late next year.

The alternatives are:

Do nothing - scrap/sell the mx5 and stick with olde-smokey perhaps fit bike carbs, but generally leave as is - good points - its simple, bad points its a leaky old crossflow which parts are getting harder to find or more expensive.

Fit a zetec - i get to keep the gearbox and prop, but its not much cheaper than a bike engine conversion.

Fit a bike engine - need to uprate the rear axle possibly, and its the same amount of work but for more cost (And possibly more benefit) than fitting the mx5 engine.

what do you think? Did i inhale too many petrol fumes this morning or is this a sensible idea?

[Edited on 29/1/08 by irvined]

MX5 Engine......well what about it.....

I would say build another car! By all accounts you can use most parts from an MX5 (engine, box, hubs, lsd if a Eunos, etc). Sell your smokey Crossflow car, then start again with the MX5. Should be very locost - possibly even a small profit to be made!

It did cross my mind as well, I would build a very different car given the information i know now, but i think if i was to build another car i'd be looking at something different again - mini was on the agenda for a while, but couldn't justify it yet as my commute is silly. This way i'd get myself a larger tin-top or move jobs.

Oh decisions, decisions.

Anybody else running an MX5 engine? What did you do with the exhaust ecu?

quote:

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Originally posted by irvined
Anybody else running an MX5 engine? What did you do with the exhaust ecu?

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As if by magic..............

I love my MX5 engine for all the reasons you list. The gearbox feels great and is supposed to be very strong. You can tune these little engines to crazy levels and there's plenty of support for them plus cheap spares.

Last year I bought a 2nd engine for £40 or €55'ish.

I modified the sump on my engine to give a bit more ground clearance. I also had to cut the PPF mount off the side of the gearbox to get the gearbox to fit into the transmission tunnel.

It's a smooth engine, likes to rev' and has lot's of desirable design features i.e DOHC, Fuel Injection, Oil jets to the bottom of the pistons, originally designed for forced induction (when fitted to the Mazda 323Turbo) etc... plus Japanese reliability.

I am currently running the standard engine management system but without the standard air box. I have a cone filter mounted onto the AFM. I have a Megasquirt built and waiting to be fitted. There's even a forum for people who are Megasquirting MX5/Miatas etc...

I fabricated my own exhaust and manifold by combining an aftermarket tubular manifold with a Caterham system designed for a 1.6 X-flow engine. It took a bit of welding but seems to work well.

[Edited on 29/1/08 by JAG]

Am I correct in understanding that MNR are doing an MX5 based version?

I also heard a rumour that Tiger had an MX5 donored car in the offing..

Martin.

Westfield now have a single donor kit that relies on the MX5 for more than just the usual donor parts - you already own the car, so it'd be about £7k all in

Or get yourself a copy of; 'How to Build a Cheap Sportscar' by Keith Tanner.
Shows how to build an MX5 based seven.

quote:

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Am I correct in understanding that MNR are doing an MX5 based version?

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edit to add
one of our new demo cars will be a single donor mazda

Oi, don't break the old girl, give her to me

i'll look after her (been looking on ebay at them recently) as a fun toy car.

whats wrong with the xflow?

What sort of power and perfrormance can you get out of a MX5 powered se7en?

How do they compare to more conventional powerplant such as Zetecs and Duratecs? (power, performance, cost, complexity)

Not sure how much this differs in a seven, but out the box:

120Bhp, peaking at 6400rpm, redlines somewhere around 7500rpm, hardcut somewhere around 8300rpm.

Performance can be boosted easily with forced induction, and you can get a megasquirt made up which is a direct swap out from the original ECU.



This is a mx5 powered caterham from the US:

http://www.miata.net/motm/2008/cannon.html

It depends which route you choose.

I think Keith Tanners 1600 is normally aspirated and making around 170bhp.

Or forced induction is a very popular way of tuning an MX5 engine. Have a look at the 'Flyin' Miata' website they have some dyno run graphs. Turbocharged 1.6 engines can make 230bhp with some 1.8 engines getting almost 300bhp. Although I would imagine 300 is a bit of an extreme set-up.

Flyin' Miata also do a 'stroker' kit to enlarge the 1.8 to 2.0 for even more madness