1990 Mazda Miata MX5 - service

Yesterday I did a slipkndgrip (slipngripross ) track day at Thruxton, great day well organised. I was interested in Thruxton as a circuit as it’s a bit wider and potentially safer with more run-off than Castle Combe, although as it’s faster that’s probably debatable. I have driven Thruxton before once at a launch event for the Ford Mondeo (original) and again at a corporate event I orgainsed which culminated in driving a Ferrari 355 round the circuit.

I started off bright and early and had a nice drive trough the country with the top down and arrived very early despite getting lost at the end. Made ‘camp’, signed on, noise check (82dB must try harder) and briefing.



Did the 3 sighting laps and realised that I had no idea where the racing line was and there were no friendly cones showing turning in points and corner apexes.

So got some instruction from Andy, 3 laps with him driving and 3 with me. Good to get independent confirmation that the car handled well, unless he was just being polite. I can’t recommend going out with an instructor enough, it showed me the lines and gave me confidence.

In a low powered car Thruxton is a pretty much a flat out circuit all 4th gear apart from two 3rd gear sections. Out of the pit lane keep to the left for the first corner (Allard) then up to the complex, brake hard and down to 3rd turn right clip the right curb then left and clip the left curb (not too hard or it lifts the inside wheels). Later in the day I was getting a bit of a slide for the initial turn. Swing right then left to hit the apex for Segrave, drift left and change up, then pretty much flat out for the next few corners. A bit of a dab of brakes for Church and then keep left and foot hard down, maxed out at about 100mph, tried 5th but nothing to be gained. Then the chicane, aim for the loudspeaker down to 3rd (I did try it in 2nd but ended up right on the limiter) turn right in the middle of the track (that took some getting used to) clip the right curb if feeling brave, then the left curb (if feeling brave) then the final corner clipping the curb (if feeling brave). I’m not sure I ever got the chicane completely right and had my only 2 incidents there, first I lost confidence between the first 2 corners braked and locked up sliding onto the run off. The second I braked when I shouldn’t have and had a small spin in the middle ending up on the run-off area. Gave the stewards something to laugh about.

Far too many words but I didn’t have anybody to take pictures, here are some from Facebook.







The whole day was well organised and very friendly, there were some other very fast cars present, e.g. race prepared E92 M3’s. I did meet up with a fellow MX5 driver , Andy, (MK2.5) which was good to share some ideas. But I didn’t feel out of place and the low numbers combined with the length of track meant that there was the opportunity to get some clear laps in.

Car was superb throughout no issues at all, although the tyres took a bit of a hammering, at least it shows I was trying. They are standard mid-range tyres that I bought in case I wrecked them and they'd done 2 previous track days.




Conclusions;

• New front brakes were very good (probably not ideal bedding in procedure), although the pedal is a bit spongy now
  
• I’ll do more slip and grip events, in fact will book Castle Combe for August
• I need a better seat, harnesses and standard seats don’t work
• Still need to think about stiffer roll bars and/or stiffer front springs
• Need to think about track biased tyres
• More power would be good :-)

Tyres show you were having fun

It looks good out there, what was the tent for?

Thanks for the mention mate. hope to see you again soon

That’s almost the same research I did with the (possibly) new seats for the Fug

We did sit in them last weekend and admire the exhaust though, so they have been useful even though we haven’t checked if they’ll fit yet

If you do buy a Tubular manifold, be careful.

I had one on my MX-5 and it was near impossible to pass the MOT. Granted, it had a decat, but considering it had the 3.5% emissions rule apply to it, it should have passed. However, it would struggle to get under.

Other cars of a similar vintage like my 944 Turbo with a decat passed the MOT fine here.

In the end I put it down to the one wire lambda sensor. With the sensor moving so far downstream on a 4 branch, they can't really help up effectively ;there is a good reason why Mazda put them right in the top of the exhaust manifold.

A wideband sensor in addition to wiring to go to the ECU feed so as to give it a narrowband signal is one way around the issue, as those sensors are heated.

Just read through this, absolutely love MK1 Mx5's great little sports cars. glad to see people like yourself keeping them on the road and I shall be looking forward to see how it progress'. I owned a little mariner blue MK1 a couple of years ago as a summer project, safe to say it didn't go well should've kept it though miss it quite bad.

Ummm, investigated the exhaust today, bad there doesn't seem to be anything wrong (it would have been a relatively easy fix), good I seem to already have a tubular manifold of sorts.




So I still have an issue, the engine runs but it's surging, sounded like exhaust issues but nothing obvious. Might be the Idle Speed Control Valve... I have remembered that there is a primitive diagnostic port need to to investigate that next. Needs to be fixed by 12:Aug!

So no faults showing that should rule out the Idle Speed Control Valve, but not necessarily the Idle Speed Air Valve. This is a valve bolted to the side of the intake manifold that is operated by the heat of the coolant, it has coolant running through it.




Took it off an despite the manual saying that water would come out not much did, anyway gave it a clean and a good squirt of carb cleaner and out it back on. The water level in the radiator was a bit low so topped that up. Did it cure things, not sure did it make a difference yes.

So that leaves me with it could still be the Idle Speed Control Valve, expensive at ~£300 to replace or the air valve, ~£25 secondhand tested. I have a suspicion that not all is right with the cooling system, it seems to be losing water. Although there was no sign of contamination when I checked the oil before the track day I am starting to wonder if there might be a HG problem.

So next step is to check oil, compression check, cooling system flush...

A question I have, I want to fit an ECU (ME221) if I do can I get rid of a lot of the additional plumbing (e.g. the Idle Speed Control) as it will be controlled by the ECU?

So how long should it take to fit a seat, couple of hours maybe... it took me the best part of a day and a half! Not helped by not having the correct bolts, bent mounting hardware and it just being incredibly tight space to work in.

Anyway, out with the old and a quick check to see if the new seat would bolt onto the existing runners, close but not close enough.





You can buy adapters from various sources but at anything from £50-75 not an option. I did but some custom MX5 seat mounts some time ago, which are listed on eBay at £63, so the first option is to go with fixed seats.



This shows how cramped it is. So I bolted the mounts to the seats after estimating what mounting holes to use. Put then into the car and couldn't get the bolts for the mounts to floor to line up. It's also incredibly tight at the back to get access. After taking the seats out and trying to mount the seats to floor after much messing about realised that they were bent out of shape (my fault) tried thee other pair I had much better.

But can't fit the floor bolts with the seat in place, so bolt front of seat in place and then bolt mounts to floor, then spend ages getting the rear side bolts in place. Everything fitted up and I realised I'd got the lap belts upside down. I'd moved them around to get the eye bolts lined up so that the snap brackets could clip over them.



So out with the seats (again, I lost count of the number of times the seat was in and out), decided to raise the rear of the seat a bit which gave more clearance to access the rear floor bolts. Eventually everything mounted.



Looks good and feels much better, although now they're not adjustable SWMBO can't drive it also it may be an issue come MOT time. Longer term plan is to make some adapter mounts to attach the seat to the runners. I think a U shaped 'tray' will work. There's something missing from one of the runners anyway so it moves about so I need new runners.



In other news, I painted up a wing door mirror in satin black, looks better than having it left in silver just need to do the drivers now and paint the quarter light frame.







Sprayed with matt black, shows up the uneven surface so I think that needs to go down to bare metal all over. The car now looks like it's wearing an eye patch