P71 SuperDork
Feb. 8, 2010 10:23 a.m.

Well the RX-7 is gone (it's going to be a Spec7/IT racer now, cool!!!) and my tax return came in so it's Miata time! We got a 93 B-Package (no VLSD) with a hardtop in case you don't already know. Audra and I are going to race with the SCCA in STS and the PCA in "Non-Porsche" so it's time to buy mods. What I don't want to do is make the same mistake with the 7 and mod it too far so it becomes a not very fun street car (too loud/too fussy).

The Miata already has 15" RoTa's. Here's what I'm thinking:

  • 205/50/15 Falken Azenis RT-615K's
  • tune-up (plugs, Magnecor wires, synthetic fluids in everything, timing belt?)
  • CAI (it needs a filter anyways, might as well grab a class-legal power mod)
  • Shocks (KYB's? I want to stick with stock springs, it's already pretty low and stiff and we are driving 150+ miles to some events)
  • Exhaust (header, cat, and cat-back. I want a nice sound that not rotary-loud. Something that makes 1 less HP and 10 less dB is fine with me.)
  • Tune (it's legal and this thing needs the throttle response. Is it just bump the timing and go or is there an actual tuner or flash for the box?)
  • Sway bars (I've heard hollow front RB and stock rear)
  • Brakes (just a stock rebuild with SS lines and HPS or Performance Friction pads, I will be HPDE'ing this thing in about 2 months)

Anything else? Suggestions on the specific parts? I already ordered a Flyin' Miata catalog and I have Racing Beat laying around

car39 Reader
Feb. 8, 2010 10:32 a.m.

Roll bar? Make sure the throttle cable is tight? Fuel filter, most of the time people miss it.

Keith SuperDork
Feb. 8, 2010 10:42 a.m.

Look at other tires. I'm not a big Azenis fan (ignore the two sets in the garage). I'd be more likely to go with something like the Kumho Ecsta MX instead.

If you don't know the service history of the car, a full timing belt/seal change isn't a bad idea. It's a non-interference engine so a broken timing belt doesn't hurt anything, but it will definitely ruin your day. I'd do the belt, all the seals on the front of the engine, fuel filter, transmission and diff fluid and shifter boots. Cleaning the injectors wouldn't hurt either.

I can't give CAI suggestions without knowing what the class regulations are, but don't mistake a filter on a tube as a cold air setup. There aren't too many true cold air intakes for the car. Jackson Racing has one and the Randall sold by Flyin' Miata is also good - but the latter requires a hole in the firewall and may not be legal.

For shocks, I'd go with Tokicos or Konis instead of KYBs. If you're thinking of putting on good springs in the future, I prefer the Tokico for that. If you're allowed, put some good bumpstops on the car. It'll make the car handle and ride better.

Racing Beat makes the nicest header. I like the FM exhausts for sound and for the lifetime warranty, but that's not surprising

You can't reflash the ECU. Bump the timing, make sure you have good plugs and wires, that's about it. The Spec guys goof around with the air flow meter, not sure how much that will get you on a stock engine instead of one with "spec" cams.

I think most people are setting the cars up with too much front bar these days, but I can see it working for autocross. Get yourself a good alignment as well.

The throttle cable tension isn't really important as long as you can still reach WOT.

93celicaGT2 SuperDork
Feb. 8, 2010 10:56 a.m.

Are you allowed to modify the AFM, or use a different one?

Any cam modifications allowed?

Kendall_Jones Reader
Feb. 8, 2010 11:01 a.m.

If your doing the exhaust & intake on a 1.6 car, I'd recommend a dyno session to tweak the AFM. I've seen lots of times where you increase the airflow through the engine (with mods) and end up loosing power because the car runs richer (AFM is "metering" more air & dumps in more fuel).

Shouldnt take more than an hour on the dyno (at least on our dyno) & you can tweak the timing as well. I've see anywhere from 2HP to 13HP gain on stock engines.

Kendall

93celicaGT2 SuperDork
Feb. 8, 2010 11:03 a.m.

Oh... this is a 1.6? My bad... disregard my previous post, what i was going to throw out there probably won't work.

Kramer HalfDork
Feb. 8, 2010 11:28 a.m.

Alignment. My car got 1.9° of camber in the front, and 1.4° in the rear, with 3/16" toe in up front, and 1/8" toe out in the rear. Great for autocrossing, not so great for tire wear, so I turned the front wheels in one turn each, which makes the front about zero toe, I think. It quit eating my Azenis every 5,000 miles, but now I track the car on Kuhmo V710's.

Keith SuperDork
Feb. 8, 2010 11:47 a.m.

1/8" toe out in the rear? Yowza, I'll bet the back end is lively.

DeadSkunk Reader
Feb. 8, 2010 11:54 a.m.

I ran my spec Miata at 1/8 toe out in the rear and it wasn't tail happy at all. I've never been a fan of a "loose" car and mine wasn't even close at 1/8 out. I ran the front between 0 and 1/8 in.

mw Reader
Feb. 8, 2010 11:56 a.m.

I'd say RB hollow front bar, no rear bar Koni's with ebay sleeves and 550/350 spring rates still a reasonably comfortable ride (I drove a 16 hour stint with this setup and didn't mind) A better tire (RE-11's or XS's) Alignment And a read through the SCCA rule book so that you are sure you not doing something legal (ex exhaust rules) I also like a different set of seats to hold me in better (a $100 kirkey will do)

There is a huge thread on miata.net in the autox forum called something like "sts state of the art" or similar and it has pretty much a laundry list of the mods that are legal and useful in STS. If it's not listed there, it's either illeagal or not worth doing.

Kramer HalfDork
Feb. 8, 2010 11:59 a.m.
Keith wrote: 1/8" toe out in the rear? Yowza, I'll bet the back end is lively.

As suggested (and done) by Shane at Aim Tuning in Indy.

Josh Dork
Feb. 8, 2010 12:03 p.m.

You MUST have those toe numbers backward front to rear. Unless the rear end was leading the front around every corner anyway.

P71, for a good street ride and semi-competitiveness in STS, I'd go with Konis and FM springs. I honestly prefer the ride of those to stock. Unless your springs aren't really stock, it's not at all stiff right now. It may feel quite harsh, because the shocks are completely gone, but it isn't stiff. Once you start autocrossing it, you will be begging for stiffer springs. I like your proposed swaybar setup, that's exactly what's on my STS car :).

As far as a tune, there isn't anything easy and legal for STS other than a timing bump. The top national guys are running a very non-standard megasquirt setup with custom parts to fit in the stock ecu box and replicate the emissions circuits. I had talked to the guy who developed this a few months ago, but I still haven't decided whether to go for it. Not sure if he's even doing any more of them honestly, I haven't checked in a while. It won't be cheap or easy to install in any case.

moxnix New Reader
Feb. 8, 2010 12:16 p.m.

Tires - I have not seen any data on the new RT-615K's either testing or pricing. With as many decent options as there are out there right now I am not sure I would go with them. options available include (R1R, RE-11,Z1SS(new miata sizes out in a few weeks), AD08, XS, RS3)

CAI - Keith is right. The randall is not STS legal.

Shocks - Go with Koni. If you are thinking about upgrading springs later think about the RACE fronts instead of the sports.

Tune - Nothing off the shelf available.

Sway Bars - Sounds about right but is going to depend on your springs also.

Tom Heath Marketing / Club Coordinator
Feb. 8, 2010 12:25 p.m.
mw wrote: I'd say RB hollow front bar, no rear bar Koni's with ebay sleeves and 550/350 spring rates still a reasonably comfortable ride (I drove a 16 hour stint with this setup and didn't mind)

That's pretty darn close to the setup I use on the Warbird Miata. My spring rates are a touch softer than this, but I'm on revalved Bilstein shocks as part of my Fat Cat Motorsports Variant coilover setup. Drove the car in full auto-x spec from Florida to Nebraska and back without any discomfort. (Other than my ankle...wish I had cruise control.) The right shock valving is a huge part of this; the difference between 4 turns from stiff and 6 turns from stiff is very noticeable.

IMHO, I really really like Bilsteins on Miatas, especailly after a revalve. You can start with a basic set of their HD shocks and upgrade them as you budget allows and they should last as long as the rest of the car. If you plan to keep stock springs forever, there might be better options.

mw Reader
Feb. 8, 2010 12:37 p.m.
Tom Heath wrote:
mw wrote: I'd say RB hollow front bar, no rear bar Koni's with ebay sleeves and 550/350 spring rates still a reasonably comfortable ride (I drove a 16 hour stint with this setup and didn't mind)

That's pretty darn close to the setup I use on the Warbird Miata. My spring rates are a touch softer than this, but I'm on revalved Bilstein shocks as part of my Fat Cat Motorsports Variant coilover setup. Drove the car in full auto-x spec from Florida to Nebraska and back without any discomfort. (Other than my ankle...wish I had cruise control.) The right shock valving is a huge part of this; the difference between 4 turns from stiff and 6 turns from stiff is very noticeable.

IMHO, I really really like Bilsteins on Miatas, especailly after a revalve. You can start with a basic set of their HD shocks and upgrade them as you budget allows and they should last as long as the rest of the car. If you plan to keep stock springs forever, there might be better options.

That's funny because my 16 hour drive was also to nebraska.

Keith SuperDork
Feb. 8, 2010 12:44 p.m.

I'll have to talk to Shane. 1/8" of toe out should be about equivalent to running casters instead of rear wheels.

mw Reader
Feb. 8, 2010 1:16 p.m.

I like to run 1/8" toe in in the rear to help keep the back end from coming around to easily. On the track, it would cause a little understeer, but in autox it seems to work.

Kramer HalfDork
Feb. 8, 2010 2:45 p.m.

Doh! It is 1/8" toe IN! Stupid me. And I'm reading it right off Shane's receipt. And I knew in my head what I was trying to type, it jsut got tpyed in bcakwards.

BoxheadTim HalfDork
Feb. 8, 2010 3:02 p.m.

The Jackson Racing CAI is nice if you can get it (very hard to get in the UK, dunno about the US). If it's legal in your class I'd try to get my hands on an ARC intake chamber that replaces the black plastic piece between the AFM and the throttle body. They're not cheap but IME they do make a noticeable difference on the throttle response. Plus they look utterly bling , but they're a little JDM YO.

As everybody else said, get the car 4 wheel aligned. It makes a massive difference to the feel of any Miata I've owned.

I'd also investigate if you're OK to put 1.8 front brakes on. All you need is the caliper brackets and appropriate brake hoses, plus of course pads & disks. It does make a difference when it comes to stopping, the disks are a little bigger and with Hawk HPSs they did stand up well to track abuse on the turbo 1.6 I had.

Keith SuperDork
Feb. 8, 2010 3:46 p.m.

I'd investigate the legality of an adjustable proportioning valve. A stock 1.6 engine shouldn't overwhelm the brakes, and putting larger front rotors on the front will only make the brake proportioning worse.

You don't need to change the brake lines when going from 1990-93 to 1994-00 brakes.

Rumnhammer Reader
Feb. 8, 2010 3:56 p.m.

I'm quite suprised that Keith disregarded the throttle cable, this is the first thing I always check and adjust when I get a new used car.

On a 93, it would definatly be the first thing I would do, is to remove the slack, as I've personally seen more then 1/2 inch of slack in the throttle cables on N/A miatas. We are talking, you can depress the throttle almost an inch before the butterfly opening!
With the age of these cars, and most have NEVER been adjusted! Believe me, if you want to increase the throttle response on a miata, check for excess slack in the throttle cable.

Chris Rummel

Capt Slow HalfDork
Feb. 8, 2010 3:59 p.m.

no adjustable proportioning valve in STS.

I really wish we could get one because the MR2 I am driving in STS needs one badly.

dkreindler New Reader
Feb. 8, 2010 4:17 p.m.

Fat Cat motorsports bumpstops. I have the full coilovers, if you can swing the shocks, well worth it.

Keith SuperDork
Feb. 8, 2010 4:25 p.m.
Rumnhammer wrote: I'm quite suprised that Keith disregarded the throttle cable, this is the first thing I always check and adjust when I get a new used car. On a 93, it would definatly be the first thing I would do, is to remove the slack, as I've personally seen more then 1/2 inch of slack in the throttle cables on N/A miatas. We are talking, you can depress the throttle almost an inch before the butterfly opening! With the age of these cars, and most have NEVER been adjusted! Believe me, if you want to increase the throttle response on a miata, check for excess slack in the throttle cable. Chris Rummel

But adjusting the slack will only make a difference when you're cracking the throttle open. It won't really make a difference in throttle response. There's supposed to be a bit of slack, making it too tight can cause problems.

That's why I discount it. At best, it's a psychological change which cannot be measured by the clock. At worst, you end up with a car with funky idle problems.

DeadSkunk Reader
Feb. 8, 2010 4:27 p.m.

I too, must bow down to Keith, although I can't claim a typo. Maybe the 57 year old is starting into Alzheimer's or something. Went to the garage and looked at my old ledger to see what my settings were. Typically 1/16 to 1/8 out on the front and 0 on the rear.

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