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Mk1 Mx5/eunos Duratec/mzr Swap


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#1 gothicsera

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Posted 22 April 2020 - 08:55 AM

Because I need another project.... obviously....
 
I've built a few Duratecs before, including a Rotrex supercharged lump back in 2009 which ended up in my kit car at the time. Back then RWD conversions weren't all that common and I did a fair bit of custom design work for parts.
 
Aaaaanyway, we have a really solid, rust free Mk1 MX5 which I have been doing a few bits on over the past couple of years. Was originally planning to stick a turbo on it and call it done, but everyone does it...
 
So I had an idea to swap what is effectively a Mk3 drivetrain into it - 2.0 duratec, 6 speed box etc. It's certainly not a common swap and there doesn't seem much info about it on the web.
 
I plan on running it on Megasquirt and bike throttle bodies. Relatively basic build with 210hp spec cams which should be enough to have some fun in the twisties.
 
I picked up a very cheap 2004 Duratec from just up the road - £100 as it had been partly stripped and then sat in the corner of a workshop for a few years. Was worth a punt.
 
Stripped it down this weekend - bores and bearings were all immaculate with the exception of a bit too much crank endfloat for my liking. So I decided to put a set of new main and HD rod bearings in and will be fitting ARP bolts to the stock rods. I don't need to rev it more than about 7250rpm anyway. 
 
Washed the block down, brushed out all the galleries, cleaned and measured the crank, rods, bores etc and all is good. No signs of wear on the pistons.
 
Deburred everything on the block and main cradle too since these motors are full of sharp edges and unfinished stuff from the factory, drives me nuts.
 
Cleaned everything up and am just starting to put it all together again. Once the short block is built I'll strip the head and clean that up properly.
 
I'll be making one of my sumps for it too since I expect there will be some height issues.
 
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#2 Zed.

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Posted 22 April 2020 - 09:25 AM

https://www.mx5nutz....howtopic=180466

 

some ideas maybe?
although this went into fitting the nc transmission (box & diff) but thread unfinished :blink: 

Rich.


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50 Shades of Silver. '91 NA6CE, Not a show car :driving: 
Ohlins dampers, COP conversion, 4.778:1 & more ideas than time :yes:
Bodger :ph34r:

https://mighty5s.com...silver-na-eunos


#3 toge

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Posted 22 April 2020 - 03:43 PM

Hello fellow Norfolk person! Sounds like an interesting build, will be good to see how you progress


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#4 gothicsera

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Posted 23 April 2020 - 06:13 PM

I finished assembling the bottom end with new bearings and ARP rod bolts so that's now bagged up, waiting for the head and sump. I'm waiting for my local laser cutters to get back to me, but I'll be ordering a few kits for the sumps and some inlet flanges while I'm there.
 
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Ordered an MS2 kit from DIY Autotune in the USA last Friday, it arrived Monday... great service by those guys as always. Probably the 10th system I've had from them, and they are always bang on.
 
A few of the usual mods, rad fan relay output, PWM idle valve and 2 spark outputs. Although this time I have built an external igniter module using 2 BIP373's to see if there is any difference in the amount of noise on signals by having those high current drivers outside the MS case itself.
 
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I picked up a bargain set of early R1 throttle bodies - these are the ones which also have vac slides in them - the thought behind these was to smooth part throttle response, I'm interested to see how this works in a car and whether it improves MAP signal at low throttle openings as I prefer to use MAP for load rather than TPS. They might be crap, but you don't know if you don't try these things. And I've been around the block enough times now to have the inclination to follow roads less travelled.
 
This is what they looked like when they turned up.
 
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Interestingly they have a wax stat attached which controls air bleed valves in each body - this appears to act like an air bypass for warm up, much the same as an IAC would on true EFI. I'm not planning to retain it since they are (according to some google research) quite temperamental and prone to seizing up. I'll be removing it and going down the electronic IAC route as usual with EFI.
 
I am planning to retain the injectors in the Duratec head, and for reference the ones fitted to the current 2.5l engine in the Mazda are around 300cc/min and super cheap (I got a set for $75USD shipped). These will work great for an engine with throttle bodies and 210hp spec cams. This leaves the holes in the throttle bodies which I might use as the air bypass for the IAC, currently undecided. I'll make a new fuel rail for the Duratec since I have a length of blank in the workshop, that way I can use the return system and add an external FPR.
 
Anyway, this is what they look like stripped of everything I'm not going to use. I will split them and re-space them to suit the Duratec inlet spacing.
 
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I also have an alternator here from a Mazda 6 - bolts straight up, but it should be controlled by the ECU using a PWM signal to the D terminal to control the regulator.
 
After a lot of research it seems that the PWM signal is ~1.3v at peak. With 0% duty cycle giving 0v output and 100% duty being ~18v output. I'm planning to have a bit of a play around to see if I can trick it into charging at a constant ~14v like a normal alternator by building an external regulator system. Why? Because I can and it will cost me nothing... if it doesn't work then the alternator goes in the scrap and I'll get a little denso unit instead.
 
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#5 gothicsera

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Posted 26 April 2020 - 04:35 PM

Done a little bit more over the weekend, although have mostly been on gardening duties!
 
Stripped all the valves from the head, washed it down, checked it all over and reassembled with the standard valves and springs etc with some new stem seals for good measure.
 
Got it bolted back down to the block with new standard bolts. 
 
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Made a blanking plate for the EGR too from a bit of 4mm aluminium offcut
 
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Found a bit of fuel rail extrusion when I was clearing my workshop for moving a few month back, glad I kept it. The stock Duratec fuel rail doesn't have a return, and they look like poo, so I made a new one. Luckily I spent a weekend organising my new workshop a couple of weeks back, and I found all my special drills for doing the fuel rails. Just need the new injectors to turn up now...
 
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#6 gothicsera

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Posted 30 April 2020 - 09:18 AM

Slowly making some progress.
 
Made a couple of odd little plenum things - one for MAP signal to the ECU and the other as the IAC distribution to each throttle body, but I might do something else for the IAC, I haven't decided yet.
 
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Intake manifold arrived yesterday afternoon, so I managed to get the throttle bodies re-spaced and offered up for test fitting.
 
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#7 gothicsera

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Posted 01 May 2020 - 05:33 PM

Change of heart on the alternator. The original one would have been in the way of the steering column and would just make it difficult to get the exhaust out of the 'wrong side'.
 
Picked up a cheap Daihatsu Denso 80amp unit and set about making some brackets for it this afternoon. Belt routing should work ok, though not with a bit of rope :D;)
 
It's all a complete mock up for now.
 
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#8 gothicsera

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Posted 03 May 2020 - 05:41 PM

Done a bit more, but slowed down a bit.
 
One of the trickier things with the early R1 throttle bodies is getting a filter to fit. The backplates won't bolt straight up as the vac slide spring covers are in the way. So my plan was to mod Pipercross PX500 filter and backplate onto them. I cut a new plate from some 1.5mm aluminium. 45mm silicone hose pushed through tight fitting holes in the plate lets it clear everything. I'm just waiting for the trumpets to arrive which will be pushed into the open ends and will serve to lock it all together.
 
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The flywheel also turned up - standard NC MX5
 
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#9 Martin Y

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Posted 03 May 2020 - 07:40 PM

Loving this thread.  And it's making me think about the 2.0 engine in Mrs Y's old Mazda 6 as she's ready to get rid of that car and it's worth peanuts anyway... 


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#10 gothicsera

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Posted 07 May 2020 - 01:36 PM

Did some welding.... hopefully it will fit and clear everything... if not, then I'll be modifying it!
 
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