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Lucas' 1991 Mazda Eunos Roadster


Themi

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Background:

After accidentally hijacking Gavs/~Slideways~ build thread, thought I should make one of my own. Here is my 1991 hunk-o-junk.
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I purchased the car in Whangarei, was driven up to collect it and took it back to Auckland. Did not check for rust as well as I should have, however ended up getting a gem. The car was always meant to be a daily, but we kind of know how that goes. It lasted about 6 months of minor changes here-and-there.

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The big issue right from the get go was the plasti-dipped exterior and weird racing strip. It obviously meant the paint would be rough underneath and plasti-dip is a real pain to remove. I've been trying everything possible to remove it, and in the end a good solvent and some elbow grease ended up being the play.

Additionally, the car had no power steering and the A/C was NFG, which is an expensive fix due to being r12 not r134a and not technically legal anymore.

I did all the fun road-trip things you are supposed to do in a newer car.

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Engine was running well, gearbox was smooth, clutch was fine (for now). Ended up changing the clutch about 3 months in after being "that guy" merging into a motorway at 60km/h trying to baby the clutch.

Around this time I noticed the diff was playing up, and it wasn't. Turned out I have the mazdaspeed 6" clutch-type LSD (as well as mazdaspeed adjustable dampening shocks and mazdaspeed upgraded swaybars). Turns out the car was a good buy after all!

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Also had a run-in with some shitheads thieves. Fortunately they didnt break anything, just my faith in humanity but it was a good lesson to not leave my car parked outside!

Anyway, the positives and negatives:
+It ran and drove
+Mildly upgraded (kinda old) suspension parts
+Clutch-type LSD
+Plenty of boot space
+Mint soft-top with glass window
+Decent interior
-Sounds bad
-Looks bad
-Slow

Now that we know whats wrong with it, why don't I go ahead and modify literally everything that doesn't help those three points? Good idea...

(Keep in mind I am a student, most of the "Why did you not just pay someone to do it" questions I usually receive can be answered by lack of funds).

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Idea:

I stumbled across the B6/ZM-DE (2012 below) build thread and decided to do some research into the possibilities of head swaps for the 1.6L B6 that came in the car. These were the only mentions I could find now, but I am sure back when I was first investigating the possibilities of the swap there were more.

Links, oldest to newest:
2004 (mazda3club.com)
2008 (mazdas247.com)
2008 (trinituner.com)
2011 (forum.miata.net)
2012 (miataturbo.net)

Why was this idea so special? Because I could not find anyone who had done it. Also other reasons, which will be revealed later.

I chose to get the ZL-VE head, as it seems it will still work but has the benefit of VVT. Also, rough napkin calculations suggested a minor bump in compression.

Purchasing and Cleaning:

So now that it was an idea I could not get out of my head, the next step was actually attaining one of these heads. PaP it is! Got an absolute steal (unlike my usual trips), I believe I paid $120 for head w/valve cover, intake manifold, injectors, alternator, lower timing pulley and timing covers.

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Then the most important step: cleaning...

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In the next post I will discuss the "benefits" of this head/swap.

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36 minutes ago, tigerstyle said:

So what you're saying is there could be piston to head contact? 

Only if your head gasket is too thin. The engine turns over fine with no head gasket at all but once it's running expansion and momentum makes them touch a bit. It'll still run but not well haha. Oops.

The minimum recommended piston to head clearance is 1mm, so a HG that has 1mm or more thickness once compressed is suitable.

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  • 5 months later...
  • 2 weeks later...
  • 5 months later...

A few small updates:

- tidied the heater core hoses using a hacked up VS commodore heater hose (nice 90 and 150° bends)

- shortened the fuel hoses

- plugs, coolant, oil, oil filter... Old oil smelled of petrol and looked dirtier than diesel oil, thinner than water! A lot of unburnt petrol in the oil from test runs, oops

- sanded and primed a small amount of surface rust

- replaced valve cover with one which had baffles (never replaced baffles on old cover)

- tidied up a bit of wiring. Still needs to be wrapped/sleeved/heat shrink.

I'm back at uni full time, and have very busy weekends so progress is slow. Still starts, runs, drives. Tidying up the tune today made it run a fair bit better!20220731_195753.thumb.jpg.8aa4403c6e00427841ca43fe037e63bb.jpg20220731_195829.thumb.jpg.d02ca62076a98667c12e475baad9d995.jpg

 

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  • 3 weeks later...

More small changes. Probably getting boring but it's progress.

20220822_153748.thumb.jpg.93c70969293991283bbf47f0dd55dfe9.jpgAir filter is somewhat back on. I'm going to get a smaller clutch master/reservoir so I don't need the hacked up bit at the back of the filter (it was adjusted to make space).

Wires were tidied up on top of the engine, just wrapped in some tesa tape. Does the job, looks way better than the kapton/tefzel rainbow happening before.

Although I tell myself this every time I touch it, the car is very close to warrant. Bulbs, horn, tyres, wipers, coolant bleed, finish tidying wiring, alignment, mild road tune, that's about it. Oh and a bonnet, it needs it's bonnet back.

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I also need to sort out the wideband. It is an innovate lc-2 reading full lean (~22:1) 95% of the time, then 5% of the time it reads somewhere normal (13:1). I'm aware this can be a faulty sensor(unlikely), bad wiring (likely), an exhaust leak (likely) or a misfire (likely). The sensor has been in the exhaust but not plugged in for a while, so it is likely very sooty. I'll need this back for the road tune to get it to a wof place.

 

Pictures are kind of just for fun, not much visually different from last time.

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  • 1 month later...

New video of it driving from yesterday. New wideband revealed my accel enrichment was very low, managed to clean it up so it accelerates not too badly.

Still hesitates when at WOT which I believe is the base map.

We also removed the dash and continued the arduous process of tidying up all of the wiring in preparation for a warrant.

Video of 1-2 shift:

Google Drive

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  • 4 weeks later...

Ok, finally a bit more progress.

Firstly, to address the last video. I believe cylinder 4 was missing in that video contributing to the rasp. It wasn't bad, but I do think it was running as a 3 cylinder.

We want it to make it to beach hop next weekend! Likely driving down on the Wednesday, so a warrant will need to happen in the next uh, 10 days?! That will include the first fail, fixing things, and a recheck...

So over the last two weekends we did some very boring things, namely:

  • Tidied the last of the wiring in the engine bay
  • Unknowingly damaged some important wires tidying the wiring
  • Realised the car wont start, removed the dash, repaired the wiring
  • Fixed the windscreen washer hosing+pump
  • Added a horn
  • Removed the rear swaybar+links, as all bushings were toast, and I don't think it is a requirement to pass a wof.
  • Replaced all damaged bulbs
  • Replaced the dash
  • Added heater controls
  • Somehow broke the windscreen washer stalk wiring?
  • Fixed a misfire on Cyl4 caused by my bad crimping on the injector wire
  • Tidied up some minor surface rust
  • Took it for a short hoon up and down the road, felt waay better with 4 cylinders instead of 3... Started acting up again at the end, but it could be anything from another botched crimp job to tune.

So what we have left to do, we think:

  • Replace right front park light
  • Find out what happened to the windscreen washer stalk
  • Swap wheels to some which have tread left on the tyre (also the current ones are quite flat, just steelies to roll around on)
  • Jerry rig some loom extender for the windows to go up and down? (creature comfort, not mission critical)
  • Install battery tie down and passenger ecu cover/kick panel (on courier)

It doesn't feel like much has to get done, but every list of 3 items to repair ends up becoming 14... Picture for fun just to show how small the engine is even in a tiny car.

Will it pass wof? Find out next time...

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Small updates:
Power windows now work for the first time since 2019, fixed the wiper stalk/washer (was just a fuse!), replaced the last few damaged bulbs... and now the misfire is worse than before. Haven't done full diagnostics, but for some reason cylinders 1, 3 and 4 aren't firing consistently. Some part of me believes this is just dirty plugs due to being run untuned for so long, but it was a sudden onset issue and could be more wiring-related.

Next, I will admit that the order of photos is more than messed up. In keeping with this, I found some older progress pics of the head going into the car, and the mess that preceded this. Some people keep asking for little images of the head going into the car before it was a complete mess so I will oblige.

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Until next time!

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Made a sub loom for my coil wiring, instead of the dodgy setup I used to have with AliExpress coil plugs and damaged sockets. I'm going to do the same with my injector plugs, just to rule out issues. OEM connectors+Deutsch hurt the wallet.

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Then had some fun with launch control...

Launch control test

And lastly my swaybar bushings arrived but I realised I don't have the brackets for the D shaped bushings. Off to the wreckers in the weekend!

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Got it out to the MX5 Car Club of New Zealand show and shine this morning in Albany.

150+ MX5's, I (unsurprisingly) wasn't winning any tidiness trophies but had some good discussions with other owners about the head and ITB's.

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