Guide to modifying an NC for the track

[Dan]

I’ve spent a fair bit of time researching modifications for my NC (I had a lot of notes/links on my PC which I used for this) and doing some trial and error.

Something I never had when I started was one place that had some information I needed to get a head start and decide the best mods to do, so in the interest of helping out the community I put together a bit of a guide to modifying the NC broken down into a few sections:
- Going faster
- Stopping and Turning
- Reliability mods (non-performance)
- Safety

I tried to remove too much personal opinion but included a little bit where it was necessary. Hope this helps people out, constructive feedback is welcome so I can update this post.

Going faster:
Hardtops:
A removable hardtop is a good idea if you can afford one for aerodynamics and a slight weight reduction.

The weight I used for the carbon hardtop was from Goodwin Racing but you can source a local version from Deckspeed in NSW which they make from their own mould. Two things to note about the Carbon hardtop is you obviously will not have a glass rear window as it is lexan which is where a portion of the weight saving is and carbon hardtops don’t have seals so you’ll need to source some from somewhere like clark rubber.

Weight, lightest to heaviest from the information I could find:
Carbon Removable hardtop - ~7kg (-23.8kg)
Removable hardtop - 24.9kg (-5.9kg)
Stock soft top - 30.8kg

Note - Many racing categories won’t allow you to run a carbon hardtop.

Tuning:
Pretty much everyone these days runs EcuTeK on the NC's, it uses the stock ECU, it has proven reliable on high HP builds and most of the tuners seem to be able to use it now.

It also has the ability to provide the following features out of the box:
- Map Switching
- Flat-foot Shifting
- Downshift Auto-Blip
- Launch Control
- Per-gear Rev Limits
- Speed Density

Exhaust:
I have a 2.5 inch custom exhaust on my car made by Deckspeed which has Racing Beat headers, cat and a muffler before the exit. This setup is quite loud and despite me not having weighed it that setup should be light.

Header:
The header is the biggest bottleneck in the stock exhaust and should be the first thing you look to change.

Traditional wisdom said the long tube headers don’t fit so I haven’t included too much information on it but Joe from Dynotronics has said that the 1.5" long tube headers have been used in the past down here in Australia and so the 1.63”/1.75”/2" (depends on vendor and application) may fit however you'll need to speak to them to confirm before purchasing - the post I’m referring to is here http://forum.miata.net/vb/showpost.php? ... stcount=16.

As for which header to get if you want a short tube header it’s close to a Pick’em between the Goodwin Max power header and the Racing Beat header, however there is an argument to say that the is better than the Racing Beat header for stock engines due to running 1.6” primaries rather than the 1.7” primaries in the racing beat which is more suitable for bigger engines or cars with superchargers. More information can be found here http://forum.miata.net/vb/showpost.php? ... ostcount=8.

Midpipe:
It’s pretty much agreed that the mid pipe doesn’t have a huge performance benefit and the weight reduction is not significant however many people including myself still look to do the whole system.

There are a few options, mostly with different options around resonators/mufflers but if you aren’t going custom I’d say Goodwin are the go to solution. Racing Beat provide some also but they don’t have a catted option which rules them out for a street car

Here’s a comparison of weights in the Goodwin range:
- RoadsterSport with cat and resonator - 7.5kg
- RoadsterSport decay with double resonator - 7.7kg
- Stock - 9.1kg

Muffler:
Brian Goodwin summed up the main options pretty well "Racing Beat is about 15% louder than stock and very deep sounding, the Magnaflow comes in about 15-20% more sound than stock, our RoadsterSport II Duals is actually adjustable for a range from 15 to 25% more sound than stock depending on whether or not you use the included baffles or the optional packed silencer baffles, and MazdaSpeed ranks about 30% more sound than stock with a little more low end boominess (similar to the Racing Beat in tone but louder). The RoadsterSport RACE single tip Miata exhaust is about 50% more sound than stock"

Weight, lightest to heaviest from the information I could find:
- Goodwin Race Single - 3.2kg
- Goodwin Street Single - 4.5kg
- RoadsterSport II Dual - 10kg (10.9kg with baffles installed)
- Magnaflow Dual - 10.9kg
- Roadstersport Q Dual - 11.1kg (12kg with baffles installed)
- Racing Beat Dual - 12.2kg (never found exact weight except people including Goodwin saying no weight loss from stock)
- Stock Dual - 12.2kg

Cams:
I’m yet to do this mod yet as I’ll do it when I do an engine swap but from reports I’ve read the cams that are now available (regrinds) are a worthwhile swap.

Mike from Moto East has suggested on a stock 2L with full bolt ons with his regrind cams the gain should be between 7.5kw(10hp) to 15kw (20hp).

Here are the Moto East regrind cams http://www.moto-east.com/store/mazda/20 ... ratec.html.

There are also Cosworth cams available but I think with the R&D done by Mike his ones would probably be a safer bet.

Lightweight Battery:
Probably not the greatest mod but it’s something. I needed to replace my battery anyway so I replaced my stock 10.1g battery with a lightweight Deka ETX15L battery which I weighed at 5.0kg which is a 5.1kg weight loss.

The reason I settled for this model over the popular lightweight option of the Odyssey PC545MJ was the ease of installation (see this guide http://forum.miata.net/vb/showthread.php?t=451899), slightly lower weight, better CCA (220) and Ah (14).

The total cost for the battery plus terminals was $170 from Batteries Direct (http://www.batteriesdirect.com.au/shop/ ... tx15l.html). The guy when I went to pick it up was nice enough to throw in the tie down for me as well which had the additional thread you need to install the shorter battery.

Weight reduction:
To summarise here are the top 3 parts for weight reduction:
- Carbon hardtop - ~23kg (17.9kg compared to OEM RHT)
- Lightweight muffler (Goodwin Race Single) - ~9kg
- Lightweight battery - ~5kg
- Racing Seat - ~5kg (each)

Additional changes that you could can do is removing the passenger seat which is worth about 16kg if your regulations allow it and if it’s a full on track car you can look at things like carbon doors but that is going to require a full cage with side intrusion bars and $$$.

How much power can I make?
Just the bolt on mods – Header, full exhaust and tune should get you close to 105kw and if Moto Mike is to be believed you should be able to easily get over 110kw with a set of cams.

For more power there are a ton of options (2.0L high comp, 2.3L, 2.5L, supercharger etc..) and a lot of the results are tune and setup dependent. If there is interest I can fill out this with some more detail but in the interest of keeping this brief I’ve not put too much detail into superchargers and bigger engines.

Stopping and Turning:

Upgraded Brake Calipers:
Bigger brakes aren’t necessarily needed on the NC with stock power given the brakes and rotors (11.5”) are quite large for a car of it’s size but it is still a mod many like to do.

There are aftermarket options to go to bigger brakes from companies like RacingBrake and Wilwood or you can use RX8 front and rear calipers, the advantages of the RX8 kit is an increase in size front and rear along with the change to vented rotors on the rear.

I have no doubt the larger aftermarket options would be better and lighter but after looking at my options I decided to get a full set of RX8 Sport Calipers (yellow dot) with brake lines from an eBay seller in the US mainly because it was significantly cheaper than the aftermarket options ($360 for the full set of 4 calipers landed) and the weight difference of 1.8kg increase in the front and 900grams in the rear will be made up in some part by lighter rotors (one thing I noticed is the advertised weight reductions of other kits were based on the calipers AND rotors).

The other option which I didn’t look into in detail is buying a set of Brembo’s from another car which suit 17” wheels and get mountings made for them.

Rotor size comparison:
Stock NC brakes - F11.5”/R11"
- Flyin’ Miata Little big brake kit - F11.5”/R11.9” (~$2,100)
- RX8 Sport brakes - F12.7”/R11.9” (~$600 inc. rebuild kit & stainless brake lines)
- RacingBrake - F12.7” (~$2,500 Front only)
- Wilwood Superlite 6R - F12.88” (~$2,500 Front only)
- Wilwood Superlite 6R GT - F14” (~$2,800 Front only, requires 18” wheels)

For the stock RX8 calipers here are the rebuild kit part numbers:
- Front caliper - B2YD-33-26Z
- Rear caliper - F1Y1-26-46Z

Brake Rotors:
Brake rotors is always a source of ongoing debate. I think the general consensus is though that slotted rotors aren’t really enough of an advantage to worry about so you should look to just buy rotors that work for you.

As I mentioned in the previous section one advantage of an upgrade to RX8 Brakes is the change to vented rotors on the rear and the relatively high availability of lighter 2 piece rotors.

For stock brakes DBA stock a good range of rotors at good prices and I've been quite happy with the generic DBA rotors so I'd suggest you check them out. If you move to the RX8 Brakes Racing Brake also make some good 2 piece rotors for both the front and rear.

Brake Pads:
I’d say Brake pads are the best upgrade to the brakes you can do.

I personally run Carbotech XP12’s on the front of my car and Carbotech XP8’s on the rear and have found the rotor wear to be very good. One thing to note though is that if you want to run the Carbotech pads you need to use fresh rotors and not use other pads on the same rotors as you are using for the Carbotech pads.

There are a few options but I’ve just given some options from Hawk and Carbotech that might suit your needs (some of this is from anecdotal evidence):

Street/track hybrid pads:
- Hawk HP+ or DTC-30
- Carbotech AXT

Track pads:
- Hawk Blue
- Carbotech XP8/XP10/XP12

Brake Fluid:
For a track car you want brake fluid with a high boiling point. Something like ATE Super Blue or Motul RBF600 is plenty enough but if you have the coin Castrol SRF is meant to be the ducks nuts.

For further reading here is a good article from StopTech on difference brake fluid types http://www.stoptech.com/technical-suppo ... rake-fluid and here’s a good FAQ on the RX8 forums about brake fluid types http://www.rx8club.com/series-i-wheels- ... aq-167264/.

Wheels & Tyres:

Tyres:
This isn’t a definitive list but for a track car these are a few tyre options for different budgets/objectives.

In terms of sizes traditional wisdom said the 16x8 FD RX7 rims was the go but lately there seems to be a move back towards 17” wheels in line with what the quick guys in the US seem to be running. I’d suggest a 225 or 235 width tyre on a 17” rim is probably optimal for the track with stock power.

High Performance Street Tyres (fast):
- Hankook R-S3
- Yokohama AD08R
Budget Semi Slicks (faster):
- Nitto NT01
- Kumho v70a
Semi Slicks (fastest):
- Yokohama A050
- Hankook Z221

Wheels:
To run a wider tyre you are going to want wider tyres, I’d suggest that 17x8 is probably a good size to buy as that is able to fit 235 tyres on the rim and have it the optimum size as well as accommodate tyres all the way down to 215.

You want wheels with the maximum offset you can get, some suggested wheels are:
- Enkei RPF1 17x8 +45
- 949 Racing 6UL 17x8 +48
- Weds TC105N 17x8 +49

Alignment:
Since my car is aligned by an MX5 race shop I choose to remain silent on the settings I run as how we got to some of the settings was through their IP.

Saying I feel this thread has some decent advice for track alignment settings http://forum.miata.net/vb/showthread.php?t=264120 and I’d reiterate the point made on the page about the need for a lot of camber if you are running semi slicks (you’ll need to get something like the Whiteline camber correction kit).

Sway Bars:
The debate over sway bars is still alive and kicking, some of the fast track guys run them, some don’t and some companies selling coilovers say not to bother.

I think my thoughts are if you are running a non-track orientated spring rate and/or need some adjustability in the car to change understeer/oversteer characteristics then sway bars probably have a benefit and I found the Whiteline sway bars I’ve been running to be ‘good’ on my car with BC V1 coilovers with uprated spring rates but MCA who I’ve just brought a set of custom coilovers off have suggested not running them so I’m about to try that out and I may elaborate on this after I’ve had some time to test.

There is a lot of information here on different sway bar sizes http://forum.miata.net/vb/showthread.php?t=486374

Coilovers:
Coilover choice is often confusing, there are so many options that are different, opinions are subjective and a lot of the fast guys have a brand preference or commercial interest.

In the interest of making this relatively brief I’ve given just a few options and I didn’t mention every brand only the ones I’d be comfortable recommending (some of this is anecdotal evidence):
BC V1 - ~$1,000
- Pro’s - Cheap to purchase, good quality for the price.
- Con’s - Poor ride, needs to run stiffer springs for serious track use (also possibly revalved), 1yr warranty.
MCA Blue ~$1,500
- Pro’s - Good quality for the price, good ride, 2yr Australian warranty, custom spring rate.
- Con’s - BC housing.
BC ER ~$2,000
- Pro’s - Separate compression/rebound adjustment, good quality for the price & features.
- Con’s - Designed for track use only, unknown valving quality control, 1yr warranty.
MCA Red ~$2,600
- Pro’s - Custom spring rates, good ride quality, local support.
- Con’s - Single adjustor, BC housing.
Ohlins DFV ~$2,700
- Pro’s - Aluminium construction, good quality, good ride quality.
- Con’s - Could use stiffer springs for serious track use (also possibly revalved), single adjustor.


Reliability mods (non-performance):
Front Hubs:
The stock hubs will not hold up in the long term to track work if you are running semi slick tyres, most of the guys with a lot of track days have experienced a hub going and I experienced a hub failure personally on my NC but luckily the car was drivable to my mechanic to be changed out.

To replace the stock hubs you want the stronger series 2 RX8 Hubs which is part number F189-33-04X (Series 2 is identified by F189 at the start of the part number).

Coil Over Plug Connectors (2005/2006 model NC’s)
The early NC’s had a problem with the coil over plug system which can cause a misfire to develop in the car, Chris from MX5 Racing talks about how to identify if you have an issue in this thread viewtopic.php?f=18&t=54755.

Rather than waiting for the issue to happen it’s probably best just to replace the plugs and wiring to get rid of the root cause. Unfortunately a full harness is prohibitively expensive but Ballenger Motorsports sell an assembly which includes the connector, front lock, seals, and terminals already crimped on 12 inch wire leads which means that it just needs to be spliced into the existing cables. These can be purchased from here for $9.99USD a piece (around $100AUD landed for 4) http://www.bmotorsports.com/shop/produc ... ts_id/2177

Rear hub & axles:
I personally haven’t seen too much detail on this but the result if it all goes wrong seems pretty catastrophic - See this thread for details on the fact that it is possible to replace the Rear hubs and axles with RX8 units http://forum.miata.net/vb/showthread.php?t=570198

Rear O2 Sensor:
I went out on the track on a 35 degree day last weekend and had an issue where my rear O2 sensor ended up falling down near the exhaust due to heat, shorted out and caused the engine fuse to pop. Reading threads on the US Miata forums this doesn’t seem to be a contained issue and my mechanic knew the issue as soon as I told him what happened.

The issue was only with the rear O2 sensor but I’ve purchased replacements for both my front and rear O2 sensors. They are Denso units which cost me around $300 for both and hopefully putting them out of the way will avoid this happening again. My reason for replacing both was so that I could keep the OEM front O2 sensor as a spare and replace it preventatively while replacing my faulty rear sensor.

O2 Sensor part numbers:
- Front O2 Sensor (Denso) - 234-9088
- Rear O2 Sensor (Denso) - 234-4340

3rd gear selector bush:
When you need to replace your clutch be sure to replace the selector bush in the gearbox. Chris from MX5racing describes the issue in this thread viewtopic.php?f=18&t=54606

Safety:
Race seat:
Mounting a race seat in the drivers side of the NC is relatively simple, you just pull the stock seat out, put a new one in on a mount (either fixed or sliding) and put a resistor into the airbag sensor to trick it into thinking it is still there, this thread shows the process pretty well http://forum.miata.net/vb/showthread.php?t=222788.

The passenger seat is more complicated to install as it has a weight sensor that needs to be tricked to get rid of the airbag light which is why I haven’t done it yet. Cyberbug explained how he did it here http://forum.miata.net/vb/showthread.php?t=444193

Roll over protection:
There is only one company I know of that sells a CAMS compliant roll bar and that is Brown Davis, the price is quite high at approx $1,400 plus shipping but I got one as I think it is better to be safe than sorry since I am 6’1 and I would sit above the stock roll hoops even with a race seat in the car.

The kit provides the ability to put the plastic trim back in the car and with the removable rear stays you still retain use of the soft top (see here)
http://www.browndavis.com.au/motorsport ... ggle-id-13

Harness:
You should always use a 6 point harness and the easiest way to install a harness is by installing a Brown Davis roll bar and using the eyelet holes that are already in it which can be accessed by drilling a hole through the stock plastic panel behind the seats if you reinstalled the trim.

If you don’t have a roll bar then you can do one of two things, weld in an eyelet reinforcement plate just under where the stock roll hoops start or use a harness bar. The downsides of both mounting methods is that if you are over 5’10 you probably have no chance of having any clearance under the stock bar so in the event of a rollover your neck will probably be crushed and the disadvantage of the harness bar is that the mounting of the harness will probably be well above your neck and cause the harness to be installed in an unsafe manner.

For the other parts of the 6 point harness it is just a matter of following the safety instructions provided by your harness manufacturer and installing the reinforcement plates for the eyelets installed to the side of and underneath the seat. Schroth have good instructions for safe harness installation https://www.schrothracing.com/sdocs/200 ... ctions.pdf

Starter Setup:
So using this information I’d say a good basic Stater track setup which should be good for a 1:10 around Wakefield if you can steer it:
- Header/Muffler - $1,500
- Whiteline camber correction kit - $150
- Nitto NT01 Tyres (215/45/17) - $700
- Carbotech XP10 Front/XP8 Rear pads & Brake Fluid - $500
- MCA Blue Coilovers (Track orientated Spring Rate) - $1,500
- 4.1 Final Drive Rato Diff - $900
- Coil over plug connectors - $100
Total = ~$5,350 + Labour

[mx5002]

Great write-up mate.
Now if you could tell me how to do 10s in my nb8b that'd be great

[lightyear]

10's is easy in an NB8B. Brendan and I have done it. With minimal power mods too.

[RS2000]

MCA Blue ~$1,500
- Pro’s - Good quality for the price, good ride, 2yr Australian warranty, custom spring rate.
- Con’s - BC housing.
MCA Red ~$2,600
- Pro’s - Custom spring rates, good ride quality, local support.
- Con’s - Single adjustor, BC housing.

The rumours about BC parts still exist !

[Dan]

MCA Blue ~$1,500
- Pro’s - Good quality for the price, good ride, 2yr Australian warranty, custom spring rate.
- Con’s - BC housing.
MCA Red ~$2,600
- Pro’s - Custom spring rates, good ride quality, local support.
- Con’s - Single adjustor, BC housing.

The rumours about BC parts still exist !

You call it a rumour but I'm pretty sure it's true (I'd concede maybe they aren't from BC but at least some of the parts come from the same manufacturer) I couldn't be bothered getting into it in the other thread though. To me it isn't really a huge con and the only reason I put it as a con is because I put the full aluminium body as a pro on the Ohlins.

Sharing the body is smart to do as you don't really want to pay for them to reinvent the wheel and do fitments for every car when it's already done by someone else and the important part of shocks is the insides which is where they invest their engineering effort. They also assemble the shocks here so hopefully most visible manufacturing defects would be picked up by them during assembly and they've sold enough that if they felt a part was a weak point I'm sure they'd get it sorted out.

If you doubt it here's some pics with a BC V1 side by side with an MCA Blue in the MCA shop http://www.86forums.com.au/index.php?/t ... on-our-86/ The pictures are quite old but you can see the similarities and if you look on the MCA website the bodies still look the same (only difference is the inverted strut).

I have a set of Reds that should be arriving any day now and I have a set of BC V1's in the car at the moment so I'll have a look myself.. I'll come back and eat my words if I'm not correct.

[zorak]

I think you are right Dan - my bc's do look very similar to the mca blues on my 86

Awesome write up mate

[sailaholic]

Well of course the mount points are going to look similar... They bolt to the same car.

I'd have said that the fact one is an inverted strut and the other isn't would be a fair indication they aren't the same ;).


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[Dan]

Well of course the mount points are going to look similar... They bolt to the same car.

I'd have said that the fact one is an inverted strut and the other isn't would be a fair indication they aren't the same ;).

I wouldn't say that is a smoking gun, in fact I just had a look and found that the BC ER Coilovers are actually offered in exactly the same configuration front and rear (inverted front, non-inverted rear) as the MCA Blue's in that thread I linked. They also look remarkably similar unlike the 86 coilovers from Ohlins and MCS which look completely different.

Here is a link to the BC Coilovers I was referring to - http://www.bc-racing.com.au/bc-racing-c ... -3235.html

MCA say openly that some parts are made overseas which is understandable as you can’t manufacture anything to a decent quality here in Australia without it costing big dollars.

I never spoke to MCA about it directly but I had a PM from a fellow forum member (well respected on here) confirming the same thing I have heard from a few people "When I spoke to MCA over 12 months ago they said that they started by BC's but by the end of it all that was left was the shell”.

Maybe it isn't technically BC but I'd suspect given the similarities the likely source of the housing and top mounts is Bor-Chuann who are the parent company of BC Racing and who do manufacturing for a few different companies (e.g. Ksport, Megan, Apexi) who also offer some shocks with close to identical housings but often with differing levels of quality control.

It doesn’t matter though, at the end of the day they don’t do everything in-house and the housing is the most obvious part that they outsource so whether it’s Bor-Chuann or Wayne Enterprises that manufacture them they are made by someone else (BC I’d consider to have good quality control).

Regardless of manufacturer I still stand by my comment that the construction of the MCA body isn’t on the level of a top end company like Ohlins or MCS who make works of art (no pressed steel parts welded on) which is the point I was making where I mentioned BC, but with MCA you pay for the quality of the insides of the shocks which is the most important part and they seemed to be unmatched in the price range for that part of their construction.

[oztrackdays]

Engine Swap Options

V8 LS1 engine = 300 rwkw for < $5k

http://www.v8roadsters.com/lsx-mounting-kit-1/

there are other Options but for a track car why not just start at the finish line.

[Charlie Brown]

Great write up Dan, it brings together many NC performance upgrades.

One point for everyone to remember is to check your class rules before you carry out any modifications, otherwise you could find you're running in a class which you won't be competitive.

There are a couple of modifications in Dan's list that aren't permitted under CAMS Type 2 class for the NSW Supersprints. The RX-8 rotor mod, as no increase is allowed in rotor diameter, and removal of the passenger seat to reduce weight is out also.

If you are going to run in a different class and use the RX-8 rotors, remember that the 16 x 8 RX-7 rims won't clear the calipers.

[Dan]

Good point Phil, I should of made that clearer. I will update the post soon and at the same time I'll also add some information I have about Aero and LSD's.

I'm building my car for 2B Prodsports now so I don't need to worry about the restrictive regs in 2B Supersprints around things like brakes, passenger seat, Aero, LSD etc..

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[mazmad]

Yes second that very useful write up.