MX5 NB Track Project

[Thomas. PLease.]

Some of this copied from another forum, but thought I'd add here; not that it compares to a lot of the metal here.

I started my things fairly arse about face when I decided I wanted to rebuild an engine, having never done so before. I've done engine swaps and some repair work but never fully built/rebuilt my own engine. Obviously had half a mind on what would be useful once built and so settled on something reasonable priced given the high chance of me getting something wrong first time out. This led me to an MX5 VVT engine of a 2004 vintage.

I wanted to essentially just rebuild, replace anything worn out and OEM+ if you will, clean everything up and lap the valves etc. Spec was pretty much stock besides some forged rods in case I decide to go FI in the future. Overall the engine seemed to be in good condition, fingers crossed. I did the work and added a baffled sump plate as well to help with the track work I was planning for. Once that was pretty much done I started to hunt for a suitable car to drop the engine into. The build was very straightforward, and just required lots of cleaning, and some careful re-assembly. I did a very mild bit of valve deshrouding, but in all likelihood made things worse than better.

In the end I picked up this 99 NB recently which seemed to be relatively rust free in the right places and having had some recent welding and paintwork. It's by no means perfect but I wanted the car to build a track focused car from so seemed to fit the bill.

The engine seemed to have a big misfire (more on that later) and after compression testing seemed very low on compression on the middle two cylinders Vs the others. I used the car for a few short trips, the PAS was leaking badly, the misfire didn't seem to get any better and the brakes were also binding on the front left.

First job really was to pull the old engine, I removed the head first up to have a look if there was any visible reason for compression loss but couldn't see anything. It was only when I got round to the coil pack that I could see coil 3 was in 2's slot and vice versa. Likely cause of misfire found! Anyhow I already had a fresh engine and so the bp4w was on its way out.

An afternoons work later and the vvt engine was in place and ready to go. Everything buttoned up and she started second go after having realised the coil pack was plugged in the wrong way.

Everything looked good until I saw a cascade of oil coming out the front of the block. Disaster. Much work later and having cleared the alternator out of the way I could see the oil pump had cracked and was leaking catastrophically. An expensive and time consuming mistake to say the least.

Another day later and I had the engine pulled and back on the stand. In undoing everything I had somehow left the old mushed up o ring in place as well as the new o ring leaving them no room, tightening down obviously resulted in the crack. Lesson learned. Following that I ordered a boundary billet gear pump to replace it to get it back together and in the car.

 

[Thomas. PLease.]

A week or so later the engine was back in now with a boundary pump and seemingly working nicely. There was a bit of difficulty getting it to run well but turned out to be the old nb1 coilpack not being well. I wired in the nb2 vvt coils which seem to be doing the job for now.

Vvt is obviously not working at the moment so I'm thinking about doing a standalone ME221 ECU or the like in order to be able to bring VVT back online.

In the meantime I've now added an LSD. I picked up a second hand Black line diff and have swapped that into the stock casing. I know it's a Chinese knock off but it was up for a reasonable price and seemed to be worthwhile. Can always change it if it does fail. Only driven it locally but seems to lock up well and is doing the job with no additional noise or issues so far.

Next thing on the list is brakes. When I bought the car the front left caliper was seized so expect the fronts need to be rebuilt or replaced and so would like to add new discs and pads all round with braided lines.

 

[Thomas. PLease.]

So after having sorted the diff which has so far been great, the next things were to look at hardtop (the soft top in place was badly leaking and broken), sorting the brakes and lines, and then looking into beginning the power mods, namely getting the right things in place for ITBs, which was the direction I wanted to take the car. I know not the best for power, but wanted something fun to drive more than anything else, with sound a bonus.

I managed to find a hard top in the right colour, it's a bit scabby but it'll do for what I'm looking for. May even consider wrapping as well.

At the same time I did new disks and pads (roddisons) all round, with braided lines. I managed to destroy the line going across the back axle so also ended up replacing that with a braided item as well.

Following this I'd ordered a Jenvey kit from Bofi, which seemed to take an age to arrive so decided to tackle the front wheel bearings which had been squeaking, and fitted an AEM wideband in readiness. Ahead of the ITBs I'd also ordered an ME221 which i'd fitted and managed to get running, albeit without VVT activated, and was running pretty averagely given the basemap.

Then this kit arrived:

Fitting was relatively straight forward with exception of the throttle linkage which took a bit of tweaking to get working. all other bits a direct swap save a bit of soldering on air temp and TPS sensors. The next things was to try and get it running, which was quite a quick process once I'd figured out the right fuel plumbing!

I managed to get it going using a vacuum line setup to harvest vacuum for the master cylinder. The next thing that was frustrating me was the wiring loom, so decided to strip it back and re-wrap for the best positioning given the new setup

Following that I had an issue with the ME221 melting one of the chips, still not exactly sure what caused this, the car worked and ran fine still but obviously wanted it checked out and fixed. I wonder whether it may have been alternator related as I after running a couple of times switched to an NA item. That left me chasing a parasitic draw for ages, before finally figuring out it was to do with the 12v switched feed. The next thing on the list was replacing the ancient 14 inch alloys, which I managed to with a set of Japan Racing items with AD08s which will see how are for now. May well be too sticky for what I'm looking for.

It now looks fairly hilarious on it's suspension so I'm looking at getting a set of Meister Clubraces, and looking forward to getting the ME221 back so we can finish off mapping and enjoy some summer driving!

 

[Thomas. PLease.]

I then managed to get the car remotely mapped which was quite an interesting process, go out and log the car for 20-30mins come back, send the log and then receive an adjustment to upload. However, I was constantly left disappointed and the car felt like it was a long way down on power for some reason. It was driveable but not overly enjoyable given how slow it was being. It took a few weeks, but eventually figured the problem. The base timing was somehow a long way out, around 8-9 degrees. Once fixed the car suddenly came alive and seemed to pick up about 40bhp.

edit more to come

 

[adam cool dude]

Love this. I love how Lego these cars are.

Friend bought a super tatty car. Bog standard 1.8 vvt. Swapped in a 4.1 LSD and 6 speed. Brackets for Subaru calipers gives a super cheap 4 pot upgrade. All costs peanuts.

 

[DRZ]

I really miss my old supercharged Mk2. I had some custom Gaz Gold Pro suspension made up for my car and that was pretty transformative. I ended up around the 220bhp mark in everyday trim which was plenty of fun

One thing to keep an eye on (perhaps less so as you're N/A) is boiling coolant around the 4th cylinder. I ended up doing the coolant re-route mod as I could hear the coolant boiling away even with an enormous radiator upgrade.

 

[Thomas. PLease.]

Love this. I love how Lego these cars are.

Friend bought a super tatty car. Bog standard 1.8 vvt. Swapped in a 4.1 LSD and 6 speed. Brackets for Subaru calipers gives a super cheap 4 pot upgrade. All costs peanuts.

Yeah one of the things I wanted to be honest. I’ve worked on a fair few different cars, these are so straightforward, by and large lots of clearance to do everything and all similar sized fasteners which, rust aside tend not to completely fall apart when touched

 

[Thomas. PLease.]

I really miss my old supercharged Mk2. I had some custom Gaz Gold Pro suspension made up for my car and that was pretty transformative. I ended up around the 220bhp mark in everyday trim which was plenty of fun

One thing to keep an eye on (perhaps less so as you're N/A) is boiling coolant around the 4th cylinder. I ended up doing the coolant re-route mod as I could hear the coolant boiling away even with an enormous radiator upgrade.

Will bear that in mind, I have just installed a new radiator. Did a track day recently at brands hatch and by and large seemed ok with temps just over 100c for most of the time.

 

[dale1uk]

I miss my JDM NB mx5

How were the front chassis legs looking whilst you had the engine out? They are a prone failure point on UK cars due to rust,and if not caught early enough can easily result in the shell being scrapped.

 

[Thomas. PLease.]

The car had a bunch of history which was one of the reasons it seemed like a good buy. Rear quarters replaced/welded and front chassis legs also welded, so they seem ok, I may well rub back the black paint in due course to check.

One of the rear quarters is starting to bubble up again annoyingly, and the rails are a bit mashed up so may look at welding in replacements at some point.

 

[DRZ]

Will bear that in mind, I have just installed a new radiator. Did a track day recently at brands hatch and by and large seemed ok with temps just over 100c for most of the time.

The temps reported will depend where it is being measured. The cooling circuit does a good job of 1+2, 3 is marginal and 4 gets barely any flow. Overall your coolant is below nominal temps but the jacket around 4 can be a total steam void. Your ears will tell you if you have an issue.

The coolant re-route is possible because the block was originally designed to be installed transversely. When they mounted it longitudinally they just plugged the original hole, or at least that's the story. In any case, there is a really obvious place for an exit on the other end of the block and so you just feed a hose round. It is well documented out there and even mx5parts stocked the kit for it.

 

[Housey]

Nice. Sold my little MX5 racer to a mate, gonna miss it even though it got nowhere near the use it deserved.

 

[Frozennova]

Love this. I love how Lego these cars are.

Friend bought a super tatty car. Bog standard 1.8 vvt. Swapped in a 4.1 LSD and 6 speed. Brackets for Subaru calipers gives a super cheap 4 pot upgrade. All costs peanuts.

I wouldn't recommend the Subaru 4 Pot route, they weigh about the same as a tank. FreakyParts do a kit that uses the stock calipers with a 280mm disc, or Clio 4 Brembos which are significantly lighter

The temps reported will depend where it is being measured. The cooling circuit does a good job of 1+2, 3 is marginal and 4 gets barely any flow. Overall your coolant is below nominal temps but the jacket around 4 can be a total steam void. Your ears will tell you if you have an issue.

The coolant re-route is possible because the block was originally designed to be installed transversely. When they mounted it longitudinally they just plugged the original hole, or at least that's the story. In any case, there is a really obvious place for an exit on the other end of the block and so you just feed a hose round. It is well documented out there and even mx5parts stocked the kit for it.

Mazda revised the cooling layout on the head gasket for the VVT engines, adding a re-route to a VVT causes the issues to go the other way and starves from 1 + 2 of flow.

I'm not convinced of it being a necessary though, I absolutely beat the death of out of old 280hp NB and when I pulled the engine apart after I bent two rods there were no signs of cylinder 4 ever getting any hotter than the rest

 

[adam cool dude]

I wouldn't recommend the Subaru 4 Pot route, they weigh about the same as a tank. FreakyParts do a kit that uses the stock calipers with a 280mm disc, or Clio 4 Brembos which are significantly lighter



Mazda revised the cooling layout on the head gasket for the VVT engines, adding a re-route to a VVT causes the issues to go the other way and starves from 1 + 2 of flow.

I'm not convinced of it being a necessary though, I absolutely beat the death of out of old 280hp NB and when I pulled the engine apart after I bent two rods there were no signs of cylinder 4 ever getting any hotter than the rest

I am sure clio 4 pots are better but you can pick up the whole kit, brackets, calipers, pads and discs for as little as £250 for all brand new kit (Pattern calipers).

 

[Thomas. PLease.]

Lots of updates to follow this and quite a few new parts. After the Me221 was replaced we got to mapping, but the car was very down on power, and I was beginning to feel fairly disappointed. Kept logging and checking and logging more but nothing we did seemed to make it much better. Eventually took the decision to replace the original engine damper pully with a Fluidampr and a new 36/2 trigger wheel. Firstly was quite surprised at how much difference the trigger wheel made to engine response, but that also highlighted the fact that the timing was way off with the old trigger wheel. With the base offset suddenly in the right place the car came alive and actually made good power. Still not properly dyno'd but Virtual Dyno shows c.160bhp vs. the previous 100 or so with timing out.

Anyway, after that was sorted I spent quite a bit of time just using the car and driving, then felt confident enough to take it for it's first track day at Brands. Car performed very well, but was starting to get a bit hot on some of the longer runs, and the tyres were far too much for the stock suspension, to the point I could barely lose traction, so wasn't necessarily the most enjoyable trackday, but good to spend time on track nonetheless. Levels of body roll a bit of a joke!

After the track day I decided I needed to firstly replace the original radiator, work on better seating and suspension, and make some tyre changes to something slightly less fully track orientated.

In the mean time I found a set of Cops a local guy was selling so took those, then created a loom from scratch to go full sequential cops, which really tidies up the engine bay, as well as the black crackle painted valve cover.

That was followed by a new seat, with associated mounts, new coilovers from meister and new drop links then new set of wheels/tyres to make the most of it all.

Before Suspension

After, could still add a bit more drop, but already catching the exhaust slightly on middle of the road speed bumps.

The suspension really transformed the car, I was massively surprised how much more compliant the car is, especially on slow speed damping. Puts my R56 Cooper S to shame and makes it a really nice drive.

In the background I've been slowly gathering bits to rebuild a new ported/polished head and am now getting close. Could probably start a thread alone on that as getting the head ready for the cams has been a long process, but I'm close now having finished the grinding/machining work. Just need to get the lash caps right now, then we should be ready to fit. My only concern at this point is the oil return holes being nowhere near the placement of the original cams, so not sure whether to just chance it and hope that'll be low pressure return, or whether I should try and open those up?

What's next. I have another trackday planned for November, so will get an opportunity to test the new suspension, seats etc. I really need to sort roll bar and harnesses but otherwise the car will likely remain as is for a while whilst I hope to get the head work sorted. I want to dyno the car shortly as is so I have a benchmark pre/post head work and go from there. May look at an overbore and high comp pistons in due course to aim at taking the engine over 200bhp which should make it very good fun.

 

[bainbridge]

Really enjoying this thread, but it makes me feel that the work I've done to my own NC is a bit underwhelming!

Regarding ITBs, does this mean that hot air from the engine bay is now being drawn into the engine rather than cool air via the CIA? If so, what impact is there? I've seen lots of mx5s with the CIA removed, but these were forced induction.

 

[adam cool dude]

Nice to see an N/A engine as most just boost because of cheap it is. Will be interesting to see what power it makes.

 

[Thomas. PLease.]

Wanted to go itbs from the start just because I really like N/A engines and I’m not looking for something that’s overly quick, just fun. Sounds being a big part of that for me. I’ve had quite a few quick cars, M3s, M2c, C63, F type R etc and just don’t find for the road, those cars as fun as something you can actually drive at full throttle for more than about 1s.

I’ve got a dyno booked for this weekend now so will get a first look at where we are. In terms of hot vs cold air, yes at the moment it’s just sucking in engine bay air. Intake temps aren’t catastrophic once moving, but if left static then heat does build up. Will investigate adding some bonnet vents in future but expect it’s only going to change a handful of degrees at the most.

I have seen a few people put a half size rad on then add a full plenum almost with ramair effect through the front bumper but they feels like a lot of work at this stage.

 

[adam cool dude]

Wanted to go itbs from the start just because I really like N/A engines and I’m not looking for something that’s overly quick, just fun. Sounds being a big part of that for me. I’ve had quite a few quick cars, M3s, M2c, C63, F type R etc and just don’t find for the road, those cars as fun as something you can actually drive at full throttle for more than about 1s.

I’ve got a dyno booked for this weekend now so will get a first look at where we are. In terms of hot vs cold air, yes at the moment it’s just sucking in engine bay air. Intake temps aren’t catastrophic once moving, but if left static then heat does build up. Will investigate adding some bonnet vents in future but expect it’s only going to change a handful of degrees at the most.

I have seen a few people put a half size rad on then add a full plenum almost with ramair effect through the front bumper but they feels like a lot of work at this stage.

Please update when you can. We are building an exocet with VVT, 6 speed and a 4.1 LSD. Maybe you can make a cold airbox out of fiberglass to go over the filters?

 

[Thomas. PLease.]

Ah nice. Yeah it’s definitely possible, I think SPS motorsport in Germany are building something similar at the moment, and jenvey do a stock plenum that could be made to fit as well but it’s a bit pricey.