The lack of proper sizing is probably the biggest issue with the WTAC control tires.

 

Agreed, but to be fair the cars looking for wide 15" options are the minority these days.

 

Many thanks for noticing my car. It is like a knife to a gunfight, being the only NA car under 2ltr and 200 RWHP... BUT, it is a fantastic event to be part of and hopefully will be back in 2018.

Unfortunately in 15" the AD08R's only come in 205 width :( I have thought about a larger wheel but the cost of swapping almost 4 sets of rims deters me. Hopefully I will have some Nankang AR-1's in 225/40/15 to test soon and if these work out then a wheel size change may be on the cards. Whilst this is a 'turbo' forum and I am NA, I will not be looking at any power mods until such time as I have reached the limit of what the car can do. Will be installing some more sensors to make use of ChassisSim https://www.chassissim.com/ and working with Kyle.

At WTAC Kyle was kind enough to speak to me on numerous occasions and his ideas/suggestions are going to be tested. Next step will to become a customer of Kyle once these tests have been done and I have sufficient data to give.

 

What lip is this?

 

Any chance you can pass on some of what Kyle advised in relation to MX5 specific info?

 

Happy to, however some is specific to my build.

1. Remove rear mudguards - cause drag
2. Remove rear bumper - test if drag reduced (like Blackbird's car)
3. Replace current vortex generators on hard top with smaller ones. The current ones may actually be reducing the air going under the wing. Simply conduct wool tuft tests.
4. Boot has way too much vertical movement. This causes the wing AoA to reduce as downforce develops. Will post details of exactly how much change in the angle if interested, it was surprising.
5. Like Blackbird's car the wing may benefit from moving more towards the rear.
6. Change the wing to a 2D instead of the current 3D.
7. Look at getting the air out from the wheel arches.
8. Look at using side skirts that make full use of the rules.
9. Both the driver and the car to go on a diet.
10. Based on my limited horsepower I will get the most advantage of reducing drag whilst not decreasing downforce.

The advice requires a lot of testing and evaluation. Further, I need to do the testing on a track that I know I can consistently deliver consistent laps on so the driver impact on the results can be reduced. Plan is to use my local track and do one test at a time, for example with the rear bumper, do a session with, without and with a cut down version.

Without doing full CFD, working within the constraints of the clubsprint rules and insufficient data makes 'ideas' more difficult to quantify. Further Kyle gave me his suggestions free of charge, however we did discuss the CFD design of a rear difusser if removing the rear bumper works. For this I will be a paying customer.

My PB at WTAC 1:52.216

Winner clubsprint 1:36.839

 

Good crash list. If there is room to cut weight, definitely do so as that is the one thing that benefits every aspect of the car.

Regarding tires, I was in a similar situation two seasons back - the class I run here in the US allows you to choose your tire make/model, but there is a treadwear rating limit and there was one tire that was faster than all other options at that tw rating so it dominated the class, and it's not available in 15". I was doing a lot of serious looking into making the necessary changes to run 17" wheels. Thankfully, rules changes shortly after that which disallowed that tire so I didn't have to go down that road. Since WTAC seems pretty solidified on that control tire, it may be worthwhile to really take a look at what you need to do to run a wheel size that allows you to get significantly more footprint on the ground. Even if it's an unconventional solution, it may be much faster. The snowball effect is in full force here though - add more power to overcome the additional drag and rotational mass of the larger wheel/tire, add more brakes to suit the increase in power, etc. etc.

FWIW, our wing kit would check three of those items off your list in one swoop

Great to see you're approaching changes incrementally and doing everything you can eliminate variables so you have meaningful data for those changes. No doubt you're going to continue to get faster and faster.

 

You may want to look at Andy Hollis build thread if you dicide to run 17in tires, he had to go that way because of rules also. Really well documented, it might be very helfull for you I think!

https://www.miataturbo.net/general-m...a-power-83002/

 

I should add that I totally get how unappetizing the thought is of changing to a new wheel size is when you have several sets already in the old size and would need several sets in the new size :(

 

I know... will send email asking for freight quote to here.

Bigben will look at the link, thanks.

 

Having read the WTAC rules I think it's down to 17's or 18's.

 

i’m reading Your thread for ideas by the way. For me I have limited horsepower and either need to use it for downforce or speed, a very fine aero balancing act. Current data and drag suggests a 250kmh max speed based on power. The question would be do the benefits of wider tyres cancel out the extra weight/rolling resistance. A BMW (NA) with a 2.5ltr motor (no aero) on same size tyres but running 98 fuel was about 0.3 secs quicker than me, mind you the driver is very experienced. I’m going to see if he can give me some data to see where the difference was, straight line or corner speed.

 

Mark, I am pretty sure there is one of those wings in Brissy already. https://www.miataturbo.net/race-prep-75/singul%C3%A4r-motorsports-aero-wing-86624/page4/#post1392744

 

Gee Emm yes there is, Tim's car I occasionally get to see it when we are at the track, however I do not spend much time at Lakeside.

 

Oh no, I'm sorry I wasn't clear, I was not referring to your car, it was more of a comment about WTAC in general in terms of the available tires... Ryan and I were just talking about it the other day..
Glad I can be of help and inspire
How much horsepower are you working with?

 

a massive 194 RWHP.

It is a pain that I can get 225/15 A050’s but not AD08R’s.

reading your build has made me think about where t save weight. Will be sending an email off to the rules persons asking some questions. First is do I need a windscreen if I have a full cage. WTAC Clubsprint rules are some what restrictive. For example I cannot use drop spindles or must use OEM brake mount points.

 

its this his one off ebay

https://www.ebay.com/itm/99-00-Mazda...72.m2749.l2649

 

Spent the Sunday ticking off a few jobs off the list, and adding some new ones

New - small flat flap off the boot to reduce drag

Tick - fix boot vertical movement. Did this with some hard plastic packers. This worked a treat, boot needs a decent 'slam' to close now. But significantly less vertical movement.



New - radiator ducting
The radiator is a PWR water/oil combo. It developed a very small leak during WTAC so was pulled out to be repaired. So decided to make the ducts to stop the air going around/under the radiator.

Passenger side - before

Drivers side after
From the mouth - will make these from CF soon. Am considering bringing the brake duct intakes onto the new side panels and 'blank' off the holes on the air dam. Could also use the space under the radiator for an air duct for the intake.

 

Did you purchase the carbon in sheets and cut to fit? Or is that something you've made yourself?

 

It was a swap deal

By the way Beavis Eipgam is Magpie spelt backwards in case you did not realise who it was.