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introduction and a few questions about a mx5 build
tmjns796 - 14/9/14 at 05:03 PM

Hello all, just thought id pop a thread open and introduce myself. I'm a 25 year old father of one, I am a hgv driver after leaving the armed forces as a vehicle mechanic. I'm from north Shropshire and have had a keen interest in 205's and old 3 series BMWs.

Since my boss took me for a spin in his nissan turbo powered Locost toy I have had the bug to build one! After 2 months of convincing the mrs I've got the thumbs up!!

The plan is to go for a Mazda eunos 1.6 pre 94 car as it has lsd and is 115hp in a Haynes roadster chassis.

I have a couple of questions.

Should i go for the Talon motorsport chassis specifically for the mx5? By the time I buy a good enough welder and the steal I could have a ready made chassis and save a good year of build time. Are there others available?

Is the mx5 rack used?

Who is considered the most economical company to buy the body panels from?

Thank you in advance.

mark chandler - 14/9/14 at 05:12 PM

If money is an issue then an abounded project will be the cheapest route, you will need to inspect carefully.

A reputable kit will retain better resale value, not sure it outweighs the additional cost, panels just buy nose cone and wings + a couple of sheets of Ali! even the bulkhead is not that hard to make, all the bends are single plane, mine was formed over a drain pipe.

Good luck

Slimy38 - 14/9/14 at 05:34 PM

quote:
Originally posted by tmjns796
Hello all, just thought id pop a thread open and introduce myself. I'm a 25 year old father of one, I am a hgv driver after leaving the armed forces as a vehicle mechanic. I'm from north Shropshire and have had a keen interest in 205's and old 3 series BMWs.

Since my boss took me for a spin in his nissan turbo powered Locost toy I have had the bug to build one! After 2 months of convincing the mrs I've got the thumbs up!!

The plan is to go for a Mazda eunos 1.6 pre 94 car as it has lsd and is 115hp in a Haynes roadster chassis.

I have a couple of questions.

Should i go for the Talon motorsport chassis specifically for the mx5? By the time I buy a good enough welder and the steal I could have a ready made chassis and save a good year of build time. Are there others available?

Is the mx5 rack used?

Who is considered the most economical company to buy the body panels from?

Thank you in advance.


The Talon stuff is good kit to be fair. However, you'll need his wishbones as well, which gets you up to £900. I would also recommend you confirm a delivery date, the guy is very popular on the Haynes forum! Welding as a skill is probably of use, so even if you don't make your own chassis it's still worth considering it. As a comparison, I spent about £200 on the metal for my chassis and wishbones, and I have more time than money.

The 1.6 Eunos is a VLSD, so technically it is a limited slip diff it isn't considered the best. Then again, it doesn't seem to make much difference in a seven, open diff owners still have fun! Get ready to have fun with the rear lower upright bolts...

The MX5 rack can only be used if it is shortened, which takes some skill and/or cost to do. I get the impression it's cheaper to buy a new proper sized rack than try and modify the MX5 one.

I wouldn't recommend going for 'most economical' with panels, there is a noticeable difference between panel quality. As an example, if you go for the cheapest panels you can find, chances are you might have to get a full paint job. Whereas a more expensive panel set might have a good quality gelcoat that can be left as is.

big_wasa - 14/9/14 at 05:54 PM

If you add up the cost of chassis and wishbones ect then add the panels then you aint far of the starter kit cost of a Gbs zero7 or a Tiger Avon both will have better re sale value.

The zero needs custom drive shafts for the mx5 donor. I " think " that Talon gets around it by sticking a metal box on the diff to centre it ?

I haven't had a chance to read up on Talon's development to mx5 donor as I would like to know if the front geo was worked out or just the bones adjusted to move the top ball joint.

The advantage is you can pay as you go. I would say after the turbo lump a N/a 1.6 will be fun in the twisties but a let down in a straight line.

tmjns796 - 14/9/14 at 06:43 PM

200bhp/ton should be ok in a straight line should it? I didn't get full throttle / boost in the turbo car.
I've read that the rx8 dif is a strong lsd unit and is a higher ratio. Something like 4:1 instead of 3.6:1 . That should make it a bit more frisky?

I'm keen on the pay as you go idea. If I was to save up and buy the kit outright I'd have nothing to do for the 12 months, and everything would just 'bolt' together and be exactly the same as that other guys 7 copy.

Please could you elaborate on the mx5 wishbones?
Regards,

Slimy38 - 14/9/14 at 06:59 PM

Standard Haynes roadster is designed for Sierra uprights. The front suspension is modified to use the MX5 uprights, this means that an MX5 lower balljoint and a BMW upper balljoint is required. This has the potential of changing the geometry. What big_wasa is wondering is whether Phil (Talon) changed the wishbone design to better suit the MX5 upright, or simply modified the sierra wishbones to suit. Judging by the pictures I think it's the latter, and it's what I've done for mine.

The RX8 unit looks closer to the NC MX5, I suspect if you build up for the NA and then try and swap over it might be more trouble than it's worth. The changed ratio could be interesting though. Personally I'll be upgrading my engine after IVA, first with a standalone ECU then a supercharger.

[Edited on 14/9/14 by Slimy38]

big_wasa - 14/9/14 at 07:31 PM

Yep that's what I meant. ^^

Don't get me wrong I am not putting Phill (talon) down as I have thought about buying a chassis my self. Ive built two from scratch and don't know I can be bothered with a third.

Have you had a look on the Haynes website ? Much less traffic but much more of the "Locost" ethos.

I am not really in a position to just out right buy a branded kit either. Its more about the build than the driving anyway.

Mine was a standard tune 2.0 zetec with around 150bhp and being live axle weighed in at just over 500kg. It was quick as a road car but after riding 1000cc bikes and having 2.5L and 2.0 turbo warm hatches it wasn't that quick .

The rx8 diff will give you acceleration but loose you top end. This could make first gear useless.

tmjns796 - 14/9/14 at 08:05 PM

Thanks for the heads up. The wishbones he has listed are to fit Mazda hubs to the seirra based chassis, using 5 series t.r.e to make them adjustable. What is the issue with this? Is the geometry going to be miles out?

big_wasa - 14/9/14 at 08:25 PM

No idea, has it been designed and tested or has it been eyeballed ? That's the question I have and haven't looked into ? I know there was a lot of design work put into the original.

Like I say this is just something I have been wandering and not an accusation against Phil. And is specific to the move to mx5.

I buy the books because I am no designer but I can build to spec off a plan.

Ive bought the Midlana book but that is probably twice as involved as a Locost / Roadster but the guy has spent hundreds of hours modelling and testing the suspension but even that has design flaws.

Slimy38 - 14/9/14 at 09:46 PM

quote:
Originally posted by tmjns796
Thanks for the heads up. The wishbones he has listed are to fit Mazda hubs to the seirra based chassis, using 5 series t.r.e to make them adjustable. What is the issue with this? Is the geometry going to be miles out?


I hope not, because it's what I'm building!! It's a design that was put together a while back by Saturn Sports Cars, and I believe it has been used a few times with no complaints. There are a few more MX5 builders on the Haynes forum.

big_wasa - 15/9/14 at 09:42 AM

I've had a look and I can't find much about it.

When I made my second chassis, locost not roadster I made the wish bones just a little bit wider and this changed the position the steering rack needed to be in to eliminate bump steer.

I will have to ask.

Slimy38 - 15/9/14 at 11:09 AM

quote:
Originally posted by big_wasa
I've had a look and I can't find much about it.

When I made my second chassis, locost not roadster I made the wish bones just a little bit wider and this changed the position the steering rack needed to be in to eliminate bump steer.

I will have to ask.


This is the current 'owner' of the design;

http://www.gillhamonline.co.uk/shop/page/12

The design is available in a PDF from the same page.

tmjns796 - 15/9/14 at 07:59 PM

I've been looking at supercharging the mx5 engine for a while. It looks straight forward and worth the work. Along with a megasquirt set up properly so it adjusts the ignition timing and fueling to work with the blower I bet it would be a very well sorted motor. But that's all in the distant future for me!

So I will need to source a siera rack and shaft and column?

big_wasa - 15/9/14 at 08:08 PM

Mk2 escort rack and you could use the mx5 column.

tmjns796 - 16/9/14 at 05:48 AM

So I could get a brand new quick rack for a mk2 and bolt that in. And use the mx5 rod ends? I'm guessing all this info won't be in the 'american' book due to not having many escort around in the us.