2011 MX5 Mod Options and their impact on Roadworthiness

[jassi]

Hi All - have been mostly a lurker on this forum other than posting about my mx5 nc when i acquired it in 2011. I just wanted to get people's views on some planned mods and how they affect the car's roadworthiness. Felt topic was more suited to general chat as mods are different categories.

Apart from two defensive driving days (one basic and one advanced on skidpan), this car is pretty much a daily driver. Almost approaching 4 years and 50,000 kms, I was looking at doing some basic mods similar to goodwin 2012 phrt street car project http://www.good-win-racing.com/mazda/mi ... oject.html

Exhaust - I was thinking the gwr super-q muffler to start with. MX5parts have this (do i need appearance variant or standard?) and mentioned they can ship it to mx5 factory in ringwood to fit it. is it ok to do the GWR mid-pipe later, i ask as with the stock mid-pipe I have been reading about some issues with the gwr supplied flat gasket causing leaks/drone vs oem o-ring gasket?
Maybe down the line I will move to the GWR mid-pipe combined with either the gwr max power or gwr street header.
I am guessing the muffler doesn't affect roadworthiness? How about the headers - is it recommended to go with the max power or street variant and which one does not impact roadworthiness? The max power seems to be stocked by mx5parts but not the street variant.

Intake - AEM cold air intake. Any views on going with this first vs the different exhaust bits (muffler, midpipe, header) first? Any impact on roadworthiness? Also does mazda really sell this as mazdaspeed branded locally as mentioned in descriptions on gwr/mx5parts in which case should be road-legal?

Suspension - Unsure, but I may have a bistein tuned suspension (2011 special edition). I was thinking of going with a pair of sway bars - GWR recommends the specially developed progress sway bars but I don't see that stocked anywhere locally and most people here rave about the whiteline sway bars and i have seen some mention of racing beat and signature sway bars. Any recommendations on which one is best as well as easiest to obtain locally.
Maybe down the line, I will look at the gwr underbody brace kit (available locally) and progress springs (not available locally) OR should i look at one of these before the sway bar? Also how do these suspension mods affect roadworthiness?

Wheels/Tires - Given i have done almost 50k on the standard 205/45R17 potenza wheel/tire combo that came with the car, I maybe coming up for an upgrade soon. GWR uses a 215/45 on a custom enkei rpf1 17x7.5 and says thats enough for street and better to concentrate on suspension mods instead. But I have seen people swear by a 235/40R17 upgrade and then others say a daily driver will no way get enough heat on the fatter tires. What is ideal, given i am mostly a daily driver and is fat rubber more important than the sway bar, etc. I don't intend to roll fenders or lower, etc. and a 215/45 upgrade will allow me to run the stock 17x7.5 for a bit vs having to upgrade to 17x8 to accomodate 235/40 rubber. Haven't seen one, but is there a 225 option? Lastly what about roadworthiness with tire/wheel upgrades - i see some plus 2 rule on the forum but don't know how to interpret that

Lastly any ideas/experiences on how a Mazda dealer would react to such upgrades when I take my care in for servicing. Do they know how to work their way around such stuff or will crib servicing such cars?

I know there is a lot of collective intelligence on this forum. I am not a mech eng and more comfortable in the car than under it, hence reaching out for guidance Thanks in advance for reading and sharing your views!

PS - My mx5 is supposedly a 2011 Mazda MX-5 Special Edition as mentioned here http://www.caradvice.com.au/103344/2011 ... australia/ but i am unsure how to identify it as the same as I can't find a brightly colored strut tower bar (mine is black) under the hood and no way for me to know if i have a bilstein tuned suspension! Any ideas on this?

PPS - don't really have the cash to do this all in one shot so any ideas on most bang for buck upgrades to be prioritized would be great as well!

[smy0003]

It can be found in this document:

https://www.google.com.au/url?sa=t&rct= ... GY&cad=rja

The 17x7.5 rpf1 SHOULD be legal, but you'll have to do the maths in regards to track width increase and wheel width increase.
I think for a car the weight of a 5 you should be allowed a wheel width increase of 1.5 inches of the greatest available factory tyre size; 7".

If it looks stockish I wouldn't imagine a copper measuring it down to the mm on the side of the road.

[jassi]

^^ thanks smy003 - thats a really useful doc. Just had a quick read of it and it answers a lot.

From reading through it, it seems the gwr super-q muffler should be fine, and perhaps the mid-pipe should be fine as well and won't require any certification. However the max power headers, change the catalytic converter and o2 sensor positions, so won't be acceptable or may require some certification?
Also tyre and rim changes within certain limits (25mm width 15mm diameter) should be ok Also it mentions sway bar substitution is fine and so are springs, braces and shocks as long as ride height is within acceptable limits (within 1/3rd of original travel?)
Also no mention of air intake in that doc, but I guess its not such a big deal.

Now to figure out which mod happens first and what is the best option - i am leaning towards the gwr super-q to start as its most basic

[Magpie]

Get on to Automotive Plus. Danny Irvine has made some very specific parts for the NC

1. A 20BPP motor
2. NC Carbon Fibre Panels. At least in QLD, provided that the panel is not considered an impact panel (boot lid for example) it can be swapped. In QLD bonnets, fibreglass ones need to be at least 1.5mm thick.
3. NC Supercharger http://store.automotiveplus.com.au/p/8725479/mx-5-nc-gt-plus-supercharger-kit.html
4. NC Rear Muffler http://store.automotiveplus.com.au/p/8508281/mx-5-nc-exhaust-25-rear-muffler.html

In addition they also sell racing beat headers for the NC.

[Mr Morlock]

If you want to know what you can do in regard to mods for an MX5 to maintain a roadworthy or legal status its unreliable looking at what any commercial operator is offering especially in another State or country- and that was the question "impact on Roadworthiness". What they do in any other State to Victoria is irrelevant. Regulations for modifications and requirements for vehicles is available "on line". The first reference point is Vicroads. and the relevant legislation. People can choose to ignore regulations and also not to inform their insurer of mods made but that does carry some level of risk. A workshop will probably just about do any work that you want done and businesses do sell equipment that is often not legal in certain States but its the owner that has to take the responsibility. Insofar as changing exhaust systems of course it can have a bearing on it being roadworthy and a LVT who can see a car has been modified will pay more attention to something that does not look like standard equipment.

One thing that can have an immediate impact on making mods is acceptance by the Insurance co. Some insurers will just cancel the insurance as they want nothing to do with mods and the problems it can entail. It was reported a few years ago on this forum that a guy had an insurance claim rejected after a car was stolen and crashed and the Insurer said that if they had been informed of the mod in the first place they would have cancelled the policy In essence take notice of Insurance implications the legislators and in particular Vicroads.

You can also be pretty sure that a number of "minor" mods can be done without any problems at all and if someone fits say mud flaps on their NC they may not bother informing the Insurance co nor have any issue with a rwc when the time comes to sell the car.

[taminga16]

Jassi,
Have a look at Reggie's Garage thread and move from there. I have had an 09 NC2 from new, fitted a GWR Roadsport II muffler, Whiteline Sways and TEIN Super Streets, the OEM tyres were B/Stone 050A's and I replaced them with a set of S001's (Brilliant), I have also installed some SS Braided Brake lines and up-spec pads.
Create a statement of needs that looks at what YOU want from the car and go from there.
Greg.

[Regie]

Have a read of this

viewtopic.php?f=57&t=49491&hilit=Reggie

Exhaust wise. If u just want a nice note replace the rear muffler. If u want more power replace the headers and keep the rest of the exhaust stock. Headers alone produce a nice raspy note and a noticeable power gain.

Cold air intake don't worry about it. It's not worth the money

Suspension. You are running stock a pair of white lines will work wonders. Also the factory blistens are nothing to rave about. They are on par with the stock shocks.

Tyres. If u are running stock wheels 17x7 there is a much better choice in 215-45 they will fit stock wheels nicely. If going aftermarket, forget about going 7.5 wide, go straight into 8" wide. U can then run 225-45 or even 235-40. Keep in mind that the 235-40 tyre choice is pretty useless in Australia. (I'm running 235's and am looking at replacement tyres ATM).

[taminga16]

Thanks Adam, I overlooked the CAI.
Greg.

[jassi]

Magpie - Thanks for the links - will look into them!

Mr Morlock - thanks for the comprehensive response on roadworthiness. Agree, need to analyse the various mods carefully vs the Vicroads modification guidelines. And yes insurance, whenever I have checked with mine, they claim its for the specified value or market value (as specified in insurance) and includes all mods and alteration (this is with 2 different providers so far), so I am going by that for now. Any recommendations on safe insurance companies for minor mods like I am looking at?

Regie - am already half way through your garage thread thanks to taminga16's suggestion lapping up the insights. Great car and looking forward to reading the rest of your thread!
Agree on the headers vs muffler, and I would like to go headers, but from reading vicroads mod guidelines, doesn't seem street legal to me as it impacts the o2 sensors and the catcon.
Sway bars - yes looking into the whitelines vs the progress, but i guess since progress is not readily available here, whitelines are the popular choice. What about the gwr 6 piece underbody brace kit - any ideas on that?
Tyes - am on the stock 17x7 with potenza 050A's 205/45. I am contemplating between 215/45 on stock rims vs 235/40 on upgraded 17x8 rims (50mm offset like this http://www.good-win-racing.com/Mazda-Pe ... -1310.html) 235/40 i think choices are ad08r or sdrives. However i did read goodwin saying for street use won't get enough heat into 235/40s.
Will avoid the CAI for now then since that doesn't look like much gains.

taminga16 - good point on the statement of needs so here goes
"Apart from the odd once a year track instance, this car is my daily driver and essential for me to get to work and back (80kms) daily as well as some nice weekend road trips. So just need most bang for buck basic mods that are street legal and yet don't cause downtime and lots of tuning. Also don't want to be caught with mods not street legal causing me trouble like having to take car off the road and get roadworthy certs, etc. I have experience living with some muffler, headers and cai on my prior car, so thats where i looked first for some minor grunt, but wanted to understand if they are worth doing on an mx5. Would like lesser lean on the car and hence some minor suspension and handling mods for street use like sway bar, springs and better tyres."

Looking at above guidance from everyone and vicroads mod guidelines, looks like I will be looking at just the muffler for now, sways (progress vs whiteline?) next and then need to figure best path to better tyre/rim options. Don't want have any experience with suspension mods, but am willing to try sway bars as long as things stay neutral (not comfy with too much oversteer causing power sliding on streets or understeering more than what it is stock) If someone can tell me a street legal path in victoria to headers then I will look at them else maybe out for now. Doesn't look like anything else like SCs or turbos are easy and street legal so out for now as well.

[taminga16]

Start with a good front/ rear alignment and then look at tyres when you need them, monitor the 'For Sale', thread, stuff comes up all of the time. Sways are a good investment and remember, our little cars were built to be quick not fast! Let the car do the talking, develop soft input and you will get heaps in return.
Greg.

[Charlie Brown]

I think most of your questions have been answered but I’ll summarised it for you starting from the front and going to the rear.

POWER
AEM CAI – not worth the money, possible increase in power on a good day 0.5kW, can lead to bent rods when the engine ingests water due to the low intake position. The NC has a stock CAI.
GWR header – the best bang for the buck modification for the NC. Will add about 10kW. No it’s not legal, it deletes the first cat. You need to add another O2 sensor bung after the second cat and extend the O2 cables to fit either side of this cat. To make legal you need to fit another (read ‘bigger’) cat in the midpipe, which given the room, may be a problem.
GWR mid pipe – If you don’t have the header you’d be hard pressed to notice any difference in performance.
GWR muffler – a legal modification, good sound for a small gain in output, maybe 2 – 3kW.
You didn’t enquire about a tune. More power is to be gained here especially if you install the header.

WHEELS & TYRES
The stock rim is 17x7. 205x45x17 tyres are the stock size but the rim width also supports 215x45x17 tyres which are cheaper to buy. You can’t go wrong with the Michelin PS3’s at around $180ea. The stock rim is too narrow for 225 section tyres.
Maximum legal width is 8” and to maintain a legal track width you need to have a minimum 43mm offset. Also you need light rims, which restricts you to just a few brands.

UNDERBODY BRACES
Save your money for something else. They are on par with CAI’s.

SUSPENSION
The cornering ability of a stock NC improves dramatically with a set of adjustable sway bars. Probably should be the first modification you make.
Shocks - Save, save, save for the best you can afford. Do not buy cheap coil overs. You are far better off with a set of lowering springs and quality adjustable shocks rather than $1100 coil overs, especially for a daily drive. Remember to stay legal the car has to have a minimum underbody clearance of 100mm. It starts at 119mm and as most of the aftermarket springs have a 35mm drop you can see you may run into problems straight away.

You should also remember that some of what you read on the US sites may not apply to us here in AU. Tyres (not tires), rim widths, power output, gear ratios, diff ratios, model year, etc are just some of the things that are different. We don’t have Mazdaspeed equipment here so it’s not considered a legal Mazda extra when fitted.

If you need to find out more, join the VIC MX-5 Club and have a chat to the boys there who have done it all before.

[jassi]

Hey Charlie - thanks for the point by point detailed response ^^

have ordered the gwr super-q muffler for now. really looking forward to it Will look at the GWR header and mid pipe if I am ready some day and follow it up with a tune then!

For tyres, when the time comes, will move to 215/45R17 on stock rims - the michelin ps3s do sound like a good deal at 180 each. If do intend to upgrade to 17x7.5 or 17x8 rims, will the 215/45s like ps3s fit on the same?

I am strongly considering sway bars but still a bit confused between whiteline sways vs progress and just heard of superpro http://www.sparesbox.com.au/superpro/sw ... 4-superpro and http://www.sparesbox.com.au/superpro/sw ... 6-superpro
I haven't heard much on these until recently. Any thoughts on which ones are best bet?
When you say save for shocks any examples or recommendations? Wil leave the shocks and springs stock for now given the 100mm rule.

Will stay away from CAI and bracing kit as not much benefit from the sounds of it.

Agreed on the US vs AU differences, hence been trying to read up on stuff from this forum. And yes its been a long pending intention to join the vic mx5 club and catch up with some fellow mx5ers will try and do so soon!

[Charlie Brown]

For tyres, when the time comes, will move to 215/45R17 on stock rims - the michelin ps3s do sound like a good deal at 180 each. If do intend to upgrade to 17x7.5 or 17x8 rims, will the 215/45s like ps3s fit on the same?

Forget the 7.5 unless the design you wants only come in that size. The 215 will fit the 7.5 but you will need to get 225 for the 8"

I am strongly considering sway bars but still a bit confused between whiteline sways vs progress

I'm not sure of your confusion.
Whiteline is made here in Australia and is readily available, often popping up second hand in this forum. Whiteline is made from solid bar and they probably supply the majority of the AU swaybar market for all cars.

Progress are made in the USA. The cost to import would make them prohibitive, probably around $650.

Deckspeed here in Sydney carry RacingBeat. These are also a hollow bar like the Progress bars. If you want a hollow bar call them for a price.

As for Sparesbox, I have no idea which brand they carry and their site doesn't say. Guess it would be a lottery.

[jassi]

Forget the 7.5 unless the design you wants only come in that size. The 215 will fit the 7.5 but you will need to get 225 for the 8"

thanks the reason I asked was if i do a 2 step upgrade - tyres 215 first and then 17x8 rims, I wanted to be able to move the 215 tyres from the 17x7 to 17x8 rims. Doesn't sound like that will work. And I am guessing if i get the 225 tyres first they won't fit the stock 17x7 rims. Maybe I should buy a tyre and rim a month and in few months they will be ready to go on the car

Whiteline is made here in Australia and is readily available

thanks that makes sense. I wasn't sure on the whole solid (whiteline) vs hollow bar (progress/racingbeat) and if one is better than other (weight, handling, etc.). The spareparts was just an example link of pricing, I was referring to superpro sway bars really http://www.superpro.com.au/sway-bars as they seem aussie made as well, but have never heard of them!

[Regie]

When i ran 17x8 wheels i had 215-45's on them. They fitted quite nicely