Introduction - here to learn about how to get a turbo MX5 powertrain into a Westfield

[Martin#30]

Hello all,

I have just joined the WSCC and the forum this morning, I am on a journey of discovery.

I want to put a turbocharged MX5 powertrain that I already have, into a lightweight seven type car. I am aiming for a predominately track car, but I do want it to be road legal for the odd sunny weekend blast - and my for my kids to drive at the Under 17 car club, but that is another story.

My current thoughts are a Mazda SDV base would be ideal. It is perhaps unpopular round here to say I want to buy a pre-built one rather than build myself. However, I will have enough work to do fitting my powertrain in as it is.

So, just wanted to say hi, and I am now off to start reading. The main question I still have is to do with 1.6 vs. 1.8 MX5 engines. The Westfield website, and some googling I have done, suggests that only the 1.6 and 5 speed gearbox can work. I have the 1.8, and six-speed, but I am puzzled as to what the problem may be - the engine/box mounts and physical sizing is the same as far as I am concerned.

Thanks,

Martin.

ps: as we all like pictures, here is the car and engine bay that has rusted away before my eyes, and made all this possible. The engine currently makes 250 wheel HP, so around 280 flywheel, so should be good fun in a Westfield. I am only a set of conrods, forged pistons and an oil-pump away from 400 bhp too.

 

 

[Dommo]

The mx5 turbo route is alarmingly common on here - quite a few build threads now or dig out my blog (mazdafield.wordpress.com). There's also a build just starting which is using a mx5 turbo from a donor straight away.

The 6 speed should fit right up but I don't know of anyone running it. Easily swapped for a 5 speed if it doesn't...

[Mark (smokey mow)]

A 6-speed box should fit, but with a turbo you would be better using the 3.6 or 3.9 diff that is currently in your MX5 and mating it to a 5 speed box as it would give much more favourable gear ratios for a lightweight car.

[KugaWestie]

Welcome

I turboed mine this winter - have a read from here on if for my install 

 

[Martin#30]

Thanks for the replies gents, very helpful. I want to keep the 6 speed as it is a much stronger box than the 5 speed, and the turbo engines can easily put out gearbox ending torque. Ratio wise, my understanding is that 6th in the 6-speed is the same ratio as 5th in the 5 speed, could be wrong though.

Dommo, your blog got me here in the first place. It has been a great read, and made me think about Westfield all over again. I remember aching desire for an SEiGHT back in the 90s, but had not really considered Westfield again until recently.

Gary, I have been reading both your build threads over lunch - very enlightening and thanks for sharing.

Best start browsing the classifieds now, and see if I can find a nice, already built Mazda SDV car out there.

Martin.

[Dommo]

6th in a 6 is slightly shorter than 5th in a 5, but not by much. I've done lots of calculations on the 5 speed and 6 speed, plus what diff ratio best suits me. As a guide to max speeds in each gear with a 3.9 diff and a 7.4k rev limit:

1st - 40mph in 5 speed, 34 in a 6
2nd - 67mph in 5 speed, 56 in a 6
3rd - 96mph in 5 speed, 77 in a 6
4th - 128 in 5 speed, 101 in a 6
5th - 157 in 5 speed, 128 in a 6
6th - 151 in a 6 speed

I think the 5 speeds stand up better in the kit cars because there's less weight to shift, and due to the nature of them you'll have mapped down that massive slab of torque in the mid range as it would otherwise just produce comedy wheelspin. Both Gary and myself are well north of 300bhp and yet to destroy a 5 speed box. "Yet". That said, if one does give up, it's considerably cheaper than replacing a 6 speed

If you're based in Wiltshire and can get to Swindon easy enough, I'm happy for you to have a look around mine. The engine will be coming out over Easter (need to baffle the sump) though so it's still SORN at the moment.

[Martin#30]

3 hours ago, Dommo said:

f you're based in Wiltshire and can get to Swindon easy enough, I'm happy for you to have a look around mine. The engine will be coming out over Easter (need to baffle the sump) though so it's still SORN at the moment.

Thank you for the kind offer, it would be great to take you up on that one day fairly soon. I would really like to understand how you have handled exhaust routing, and the intercooler pipe work. 

I am only 15 miles away in a village near Cirencester, I will drop you a PM at some point and see if there is a convenient time. 

Martin.

[TAFKARM]

I thought the 6 speed was weaker? I had the 6 speed in my old mx5 turbo and killed the syncros in 2nd and 3rd. Crunch crunch!

[Rhett Turner - Black Country AO]

If you can make Stoneleigh in a few weeks there's bound to be more than one turbo MX5 based Westi to look at. 

[KugaWestie]

3 minutes ago, Rhett - Joint Black Country AO said:

If you can make Stoneleigh in a few weeks there's bound to be more than one turbo MX5 based Westi to look at. 

Mine will be there all day Sunday and Monday morning  

[BenD]

Mine will be on the Sunday 

[Martin#30]

So my car searching has bourne fruit, and I thought it only right to come back to this intro post and close it out.

From my original post, you will see I went looking for a Mazda SDV car that I could transplant my existing powertrain into, but alas man-maths took hold (amazing how often that happens to me, I must be unlucky ....), and I bought a RoadRunner Racing SR2. I was on my way to see the beautiful black SDV Marcus has for sale last Sunday afternoon, but I viewed the SR2 in the morning and alas, I ended up not making it to Marcus'. Marcus, again I apologise.

This is the car I bought:

 

 

Lots for me to now learn, as the fuelling is not right on the car. I am used to tuning/mapping Megasquirt on my MX5, but this powertrain is completely alien to me.

 

Now that I have this, I no longer need the MX5 turbo powertrain so if the WSCC forums allow, I am off to put up an advert for that. Perhaps it will be of some use to a fellow SDV owner hankering after wheelspin, blow off valve noises and generally forgetting to act our age.

 

I also hope it is acceptable to stay here as a member, and forum user, even though I have swayed from the fold.

 

Martin.

[Dave Eastwood (Gadgetman) - Club Chairman]

Interesting, well look forward to hearing lots more about the new car, pictures included!

And no, it really doesn't matter what you own, you're still most welcome, though I can't promise you might not get your leg pulled occasionally!

[Captain Colonial]

With that power plant up front?  I'm not going to tease him!

[6carjon]

Hope it came with a radiator you're gonna need a big one