Wheelhop is an issue in the wet. Pulling out of junctions in 2nd, the rear tends to spin up even at small, license-friendly throttle openings. This is fine, no different to how the car behaved before the build, and I love it. However, what I don't love is that most of the time the wheels don't spin up smoothly now - they hop like mad and I feel awful for the poor rear end. My feeling is that stiff engine mounts combined with standard diff/subframe mounts are encouraging the rear to twist and spring.
Starting to wonder if I wouldn't be better off without the PPF. Thoughts, anyone?


1000 miles just clicked over on the odometer :D I took a celebratory photo, and short, low-res celebratory tacho vid. Will upload later.

Also, when looking at the car the other day, I couldn't work out why we didn't flip the PPF over and mount it on the other side of the driveshaft, away from the exhaust. In light of the slight resonance issues I have, it would seem to be worth the hassle.

1000 miles :D

https://www.miataturbo.net/attachmen...ine=1348425655

Loving the vids. I totally forgot you have that sweet gauge cluster. Very nice

yeah that was nice

This last week, I've been thinking that I should have bought a nice Caterham for every day use instead of putting the money into this Mazda.

Then yesterday, I read some Caterham owner's opinions about high-mileage driving, especially through the winter. Apparently, no matter what Caterham you drive, the chassis as a whole corrodes very easily when subjected to salted UK winter roads, the doors let water spray in from trucks and puddles, and the hoods leak either slightly or severely. Misgivings were expressed by owners regarding unnamed reliability issues that were experienced when the car was used every day for their commute. Someone sold their daily-driven Caterham specifically because they were so tired of avoiding large puddles in an attempt to not get wet.


I like not getting wet, and I like being able to rely on my car. I'm glad I kept the cheap, dented hairdresser-mobile.

New dampers are on the way. Stuff is occurring. F20C MX5 Version 1.1 is in the works :D

Perfect :brain:

Owen, nice build, well done. +1
I am curious though, what was the reason you picked the Miata/F20c path instead of running an S2000?

I think the Mazda has a better chassis for having fun in, and much better steering feel. It's just more in line with what I want out of a road car. If I was building a car to simply go fast in, I'd choose the S2000, as it's ultimately much more advanced and capable if you simply want to get from A to B.


*I'll add that 1) a fully-trimmed Mazda is at least 250kg lighter than a fully-trimmed S2000, the only unarguable advantage of which is that the F20C feels like a much stronger engine in the Mazda;
2) The steering in the Mazda is still a bit vague around the straight ahead, which is annoying, but with any lock on it tugs and writhes and is generally quite awesome. Geo and general set up still needs work though, specifically in the sense that there's a point in the steering's input where the car's nose moves more than you think it should. I think this is what Mr Barker was talking about when he talked about the steering not being perfectly linear. A standard MX5 does not have this peculiarity though, which thankfully means it's an issue that should be straightforward to solve with a better car set up.

My car felt a little lacking in stance the other day…

https://www.miataturbo.net/attachmen...ine=1349813029


Stood up very well on the road, though. The Elise Sport 160 had a much more comfortable ride, presumably combined with masses more grip. Bloody Lotus and their chassis wizards, huh.
Tellingly, my friend has had the car a few weeks, and said he hasn't felt confident enough to push it yet due to the Mk1's reputation as being quite snappy on the limit. He's a very good driver, so that's not the problem. However, if he soon reports that it's actually utterly benign at the limit I'm going to be quite envious.

https://www.miataturbo.net/attachmen...ine=1349813029

Reliable car is not so reliable. At the top of fourth gear, around 8800rpm, the engine stops revving, falls back down to around 8000rpm, then revs again. It's like the ECU is detecting something that it doesn't have time to react to in the lower gears, and shutting the power off. I am seriously considering going to a full standalone ECU because the Honda unit plus the Dastek (which still doesn't work) is not a happy match in this Mazda. I've put a 'wanted' ad up on s2ki for an AEM ECU. The car is going to tdi-plc in London a week on Monday to be tuned, as planned, although now they might not be tuning the Dastek, but installing and programming an AEM.

The car's been trimmed now and nearly every niggle has been sorted. A new bung has been made for the exhaust because even with the old bung, it registers 107db at the track, which is too loud. It needs to be 105 or below. Hopefully the new bung has sorted that, although it's quite restrictive. I'm going to see if I can get QPrep to make a replica of the old, 107db bung for road use. Even with no bung, the car is actually reasonably quiet inside now it's been trimmed, but unfortunately every policeman in the county can now hear when I "do VTAK".
The new dampers are being tweaked this coming week. The manufacturer is coming to meet me tomorrow to take the car and do some datalogging.





Anyway, it's getting there! Now, where have I heard that before...

You're having the suspension manuf come out to set up the car? That's so badass

Yeah. He's a great guy. The dampers are already an improvement on the Xidas.

The car's now booked in to tdi-plc.com on Friday 9th November, for an install and full tune of an AEM EMS. TDI said they could work on the Dastek in their workshop in the morning, then assuming it worked - which is a big assumption - tune it in the afternoon, but the total cost of them doing that is nearly as much as it would cost me to buy an AEM standalone, then have them install and tune the AEM unit in a couple of hours. As I've said, a standalone should be a great way to rid this car of bugs, in theory. QPrep have put in countless hours ridding this car of fault codes and 99% of glitches caused by the lack of OEM Honda air pump and the Dastek, which of course makes me wish I'd decided to go the standalone route sooner than I have done in order to save QPrep the hassle. Hindsight is a wonderful thing, though.

With the exhaust bung in, which is necessary for other people's ears, I don't think the car will make much more power than a standard S2000, but that's not a big deal. In my opinion, the side exit exhaust remains a good feature of the car. Even with the bung out, the fully trimmed interior now means it's completely possible to have a conversation on the motorway without raising your voice, which is actually an improvement over having the bung in the exhaust without any interior trim. It's amazing how much a bit of trim has quietened it down. The side exit remains the only visible modification to the exterior of the car, which in itself is quite cool. It also means I'll have an easier job of packaging a diffuser, because the silencer/muffler no longer occupies useful ventilation space behind the rear axle, and it'll make the task of managing diff heat with a flat underbody easier because I no longer have a hot exhaust pipe wrapping around said diff. With any luck all the underbody stuff will be done before Summer next year.

I'd like to say right now that QPrep have done a great job with this car. They've been extremely helpful in sorting any glitches out, completely free of charge. Everybody involved in it is quietly proud.

After the AEM install, final damper tweaks and an alignment, the car will be basically there. Videos will follow.

Fair play on the build man!! completely awesome and nuts!! i drive an S2000 Daily and love the engine.. a also have an mx5 so i can just imagine how epic it is to drive with the s2k engine in it!! top marks :D

Been a while since I have commented on your build, it looks great, well worth the wait im sure. As for wheel hop, I would be more concerned with the transmission tail shaft and the forces being transmitted to it by the ppf, it was not designed to carry the load the ppf is placing on it. Could you post up a couple of pics of the mount? When my car was on the stock clutch I never had an issue with wheel hop, so I would look closely at how the ppf is mounted. It needs to be solid or you will get the hop that you have described. Old solid axle guys call it axle wrap, it is a function of the diff being moved by the forces the pinion gear is putting on the ring gear.

Here is a pic of my solution for the ppf

https://www.miataturbo.net/attachmen...ine=1352306041
https://www.miataturbo.net/attachmen...ine=1352306041

Yours looks pretty good to me.
Poly diff mounts were installed at the same time as the car was trimmed and snagged, and they've reduced wheelhop to less than "stock" levels, thankfully. I'd love to eliminate wheelhop entirely, but I don't think it's practical at this stage. Time will tell whether or not the end of my gearbox falls off. If it happens, I'll be sure to write an honest appraisal of the incident from my hospital bed.
Luckily the resonance issue turned out to be caused by a loose mesh core in the small Burns silencer. So in short, I owe my PPF an apology for swearing at it many times and blaming it for wheelhop and resonance.
However, the bloody exhaust still knocks somewhere. It happens when you start the car, and sometimes during hard right hand cornering. The clash is almost certainly between the exhaust and the cross brace between the frame rails, because there's only a few mm clearance between the two. It's something QPrep haven't had time to look at yet. If it's clashing where I think it is, raising the exhaust 5mm or so will probably solve it.

I haven't been able to source an AEM unit for Friday, because by the time I'd given up looking for one secondhand, it was too late to order one from anywhere in the UK because not a single shop seems to carry them in stock. I'm still going to TDI on Friday morning though, to investigate the difference the restrictive trackday-spec exhaust bung makes to the engine's happiness, and to see if they can diagnose the fourth gear problem I'm having. Basically, if it's a failing piece of hardware causing the issue, I'll be able to order the part in time for when I go back to TDI in a couple of weeks with the AEM.


I'll report on everything, including the new dampers, on Saturday. The car's still in London with the damper guy at the moment, so I can't take any photos yet hingston. I'll be going to Sheffield on Friday afternoon to Blink Motorsport for an alignment and corner weight session, so I'll have some weight figures too. I have a feeling the car is either overweight or underpowered at the moment, as it doesn't feel quite as sharp as it should considering there's supposedly 240 obnoxiously whinnying ponies hoofing along 1000kg/2200lb.

225 at 8500 at hubs, 12 more than stock S2k, afr at over 15:1 between 4 and 5k rpm and consequently knocking, top end glitches prob caused by unshielded crank position sensor wires

Can you clarify "load"?

What most don't realize is the ppf is actually designed to twist as an energy absorber in the interest of mechanical empathy vs. pounding parts. Though not so good for putting max energy to the ground.

Engine mounts have vibrating loose and probable different electronic 'noise' caused by TDI simply thumbing through the ECU wires at my request causing the car to not rev over 3k rpm means I'm getting towed home and cancelling the corner weight session. Absolutely gutted.