D Prepared Miata Build

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
So, as some of you know I'm planning on sort of taking the Miata and turning it up to 11 in the coming years (yes, this is a very long term build), and I didn't want to further clutter up my already cluttered up STS build thread.

What I want this thread for at this point is as you may have guessed, planning. Bouncing around ideas (for the foreseeable future, mostly focused on weight reduction), documenting parts accumulation and eventually towards the end of 2010, a massive de-construction of the miata.

The goal is a dual-threat machine, with the competitive emphasis being on D Prepared autocross, but also, eventually as time and budget allow, as a track day / hill climb / time trials car.

The end result, for those that may not know what a D Prepared Miata looks like, is something like this (essentially an E/F Production club-race car):



For the record: Yes, she will run most of this season (if not all) in STS trim. After that, depending on a few things, the evolution (Eviloution if you will) will begin.


(rockon)
 
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aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
1 of the biggest "need" expenses besides a roll bar (as required by the rules) is a good set of wheels. I had a few options I was throwing around:

1. Cheap as F, I could go with boat anchor Diamond Racing wheels. They'd get the job done but sort of go against the very principle of the initial phase of this build: drop as much weight as possible (without spending mad $$), especially unsprung and rotating mass. Not really great looking either (I'm a sucker of function WITH form if I can have it)

2. At the opposite end of the spectrum are SERIOUSLY crazy money, flyweight wheels, Keisers for example. I really didn't want to go that light, and I wanted a wheel that I wouldn't have to worry about bending or cracking every time I ran over a pebble. These were definitely out.

3. Panasport ULs. We're starting to come back down out of the stratosphere here. Still really spendy. They're light AND strong, and admit it, who doesn't like how a set of Panasports look on a Miata? I know I do. And I REALLY had to fight with the decision, but in the end they just turned out to be too much money compared to the alternates.

4. Superlite Minis. They're basically panasport look-a-likes, weigh just a pound or 2 more, but weren't really offered in an offset I was happy with. They could work, but if I was putting up money (I was), I wanted something that I would buy and would work as I wanted to. I was very close to buying these

5. Real Racing wheels. Ugly as sin, and for the price, pretty heavy. But, they would be custom-made to my exact application.

6. I stumbled over the Spin Werkes section on Racer Parts Wholesale's website and was fairly certain they were winners. They were less expensive than some of the other realistic options (Panasports, Real Racing), weigh the same or less, look decent (better than the Reals, worse than the Panasports lol), be very strong, and would be made custom to my application. You can ask anyone I've been discussing this with, I flip-flopped a LOT with the decision, but I couldn't justify spending more money and getting less wheel for my dollar.

Last week these shiny little things showed up:






Spin Werkes series 82s, 8.4lb each (about 1lb lighter than advertised!) in 13x7, 4" backspace. Hubcentric for the miata, with the Mazda-fitment 60* tapered lug seats with Mazda-fitment 12mm bolt-holes, in 4x100. When I say custom, I mean they can make them pretty much however you want them :D

So, after a couple months (without budget) of deliberation, when the budget was there, that's 1 major building block sorted :)

For those wondering why a 7" wheel would poke out so far on a miata: we'll eventually be running 9.5" wide cantilever bias-ply slicks (they'll look more or less like this), so you need that room on the inside to prevent any interference with the suspension.

And to head off the "why only run 7" wheels!?": it's a wheel width limited class. You're allowed to run up to a 7" wheel without penalty. Anything between 7 and 10" incurs a 75lb weight penalty. Since I'm going to be pretty under-powered, I'm going for class-minimum weight if at all possible.




The next, and biggest phase, will be weight reduction, but it's late and so I'll pick that up tomorrow :)
 
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aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
Weight Loss Ideas

Just for starters...

The easy stuff:
-The wheel / tire package will drop about 40 lb total (going from about a 35 lb combo with street tires to about a 25 lb combo with slicks) by itself.
-Gut the dash (eventually remove it and replace with a light 'cover')
-Remove all the audio equipment
-Pull the bumper supports
-Get the heavy ass stock-type battery out
-Pull the ballast off of the seats (5 lb total lol),
-The windshield surround
-Windshield
-Side and 'sail' glass
-Soft top
-The headlights, motors and hinges
-A lighter intake
-Gutting the tail lights to only keep the brake lights (Not a necessity, but if I want to track the car it would probably be for the best)
-Windshield washer bottle
-The carbon canister for the evap system (any reason should keep that?)
-Windshield wipers and motor
-Inner fender liners
-Turn signals and the side markers
-Trim the rear bumper
-Air bag & stock steering wheel, and airbag sensors / wiring / etc

The expensive / more difficult / diminishing returns stuff:
-Fuel tank (replace with a 5 gal fuel cell)
-Redoing the wiring harness, getting rid of much un-necessary wire
-lightweight shocks
-lighter, tubular control arms
-lighter spindles
-lighter calipers (wilwood maybe)

what am I missing?
 
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TinmanMS6

Now, with more Zoom Zoom!
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2012 Subaru WRX
Turning it up to 11, huh? That's a long way from 3. :p

Edit: Don't think I haven't noticed you slamming the door on any "DP" jokes so far.
 
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TinmanMS6

Now, with more Zoom Zoom!
:
2012 Subaru WRX
If I'm not mistaken (and I very well could be) there is more weight to be saved in rotors than calipers. 2-piece w/aluminum hats and swiss cheesiness, yo!

Fiberglass? Legal?

Dammit. Now I'm going to have to make myself minimally aware of the prepared ruleset. All I've ever looked at is XP, because the possibilities are awesome.
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
Turning it up to 11, huh? That's a long way from 3. :p
No kidding...
Edit: Don't think I haven't noticed you slamming the door on any "DP" jokes so far.
hahahaha I've been trying but it's bound to happen. Talk about a cruel joke on Miata and MR2/MR-S drivers...

If I'm not mistaken (and I very well could be) there is more weight to be saved in rotors than calipers. 2-piece w/aluminum hats and swiss cheesiness, yo!
Not a bad thought, actually

Fiberglass? Legal?
Fiberglass what? Calipers? Brake rotors? 0.o

Dammit. Now I'm going to have to make myself minimally aware of the prepared ruleset. All I've ever looked at is XP, because the possibilities are awesome.
Get to readin!
 

TinmanMS6

Now, with more Zoom Zoom!
:
2012 Subaru WRX
Fiberglass what? Calipers? Brake rotors? 0.o
Haven't gotten to that rulebook yet, but hood (yeah, not much weight, really, but...), fenders, trunk? I don't know what's legal, but I'm pretty sure hood and fenders are at the very least.
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
yeah, pretty much all of that. The problem is they aren't necessary, and very far in the 'diminishing returns' side of things, so it'll eventually happen, but it'll be a while. I may just get some cheap flares (as opposed to replacement fenders) to start off with
 
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TinmanMS6

Now, with more Zoom Zoom!
:
2012 Subaru WRX
OMG. I'm looking at the rulebook...

(attn) $$$$ (attn) $$$$ (attn)

Holy engine builds. And suspension. And...

Are you going to swap to a depowered rack now?

Holy crap, you basically need to keep your shell and (most of) the block.
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
lol yeah I know that's right. RE the rack: I've already got a manual steering rack. And yes, they give you plenty of rope to hang yourself (and your wallet) with.
 
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TinmanMS6

Now, with more Zoom Zoom!
:
2012 Subaru WRX
yeah, pretty much all of that. The problem is they aren't necessary, and very far in the 'diminishing returns' side of things, so it'll eventually happen, but it'll be a while. I may just get some cheap flares (as opposed to replacement fenders) to start off with
Yeah, there's enough stuff you can do to pull weight out for free that there's not much point in throwing money at it yet. Pull the whole dash and bend up some aluminum to cover it. Yank your bumpers and start cutting whatever's under there. Throw out everything in the engine compartment that's not required to go, stop, or turn. We could go all day here.
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
Yeah, there's enough stuff you can do to pull weight out for free that there's not much point in throwing money at it yet. Pull the whole dash and bend up some aluminum to cover it. Yank your bumpers and start cutting whatever's under there. Throw out everything in the engine compartment that's not required to go, stop, or turn. We could go all day here.
You did look at my list, right? I'll do the sheetmetal dash once I get a full cage in. Until then, just gutting the stock dash will do (free vs $ ;))
 

khaosman

P5T R.I.P.
Contributor
:
2006 Honda S2000
I can't wait to see this build progress! It sounds insanely fun, and cool.

Details on motor. Higher compression, ITBs, custom exhaust manifold? Tell us more!! :)
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
I can't wait to see this build progress! It sounds insanely fun, and cool.

Details on motor. Higher compression, ITBs, custom exhaust manifold? Tell us more!! :)
ShhhhH! You keep talking like that and my wallet will hear!

Yes, all of those are planned, but that's going to be a year away (from the actual start of this build, which is most of a year away) at a minimum. Because I don't really have the budget for it, I haven't really done any heavy homework on the engine side of things yet.

Essentially the recipe is going to be high compression, light-weight rods & crank, ported head + bigger valves & stiffer valve springs, bigger cams and adjustable cam gears, ITBs and a bigger exhaust manifold. Not sure if it'll have to be custom, but the Maxim Works header may work too.

To start off, we're going to have a KCBHIW MegaSquirt on the current, fresh-stock-build + overbore engine (which, for a stock engine, is pretty stout) + an intake that eliminates the air meter, so that'll tack on a few extra horses and probably have us in the 125 WHP range.

Now for the racer's excuses: I'm going to be dealing with essentially a brand new race-car, plus moving from street tires to full on race slicks in a car that's going to be 300 lb lighter than anything I've driven. The last thing I need at that point anyway is 50 more horses to add to the mix. I say that now, I'm sure by the 3rd event I'll be wanting it haha
 

TinmanMS6

Now, with more Zoom Zoom!
:
2012 Subaru WRX
So, when you pick up that '01 motor for the new build, you wanna ship me your 1.6?
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
I'm not building a 1.8, but nice try. Base weight is based on displacement. To build a 1.8 would put me at just a hair under 2000 lbs which I'm practically at now, so I'm going for the low-drag solution
 

TinmanMS6

Now, with more Zoom Zoom!
:
2012 Subaru WRX
I'm not building a 1.8, but nice try. Base weight is based on displacement. To build a 1.8 would put me at just a hair under 2000 lbs which I'm practically at now, so I'm going for the low-drag solution
What's the formula? It seems to me that the extra power of the newer 1.8s would far outweigh the difference in weight required for an extra .2L.
 

aMaff

High Speed Low Drag
Moderator
:
1992 Miata / 2003 Pathfinder
What's the formula? It seems to me that the extra power of the newer 1.8s would far outweigh the difference in weight required for an extra .2L.
Prepared Class D

Minimum weights are determined by engine displacement. Increases in engine displacement resulting from legal overbore are not considered in these calculations.
Weight formulas (lbs):
Engines with displacement less than or equal to 1667cc: 1.10 x displacement (cc)
Engines with displacement greater than 1667cc: 0.95 x displacement (cc) plus 250 lbs

So with the 1.6L I come up to 1757, with the 1.8L it comes to 1960 (so, 200-ish lbs). On a road course I'd be in 100% agreement with you, but for autocross I think getting as light as possible is going to be key. I don't think you can make enough extra hp to overcome 200 lbs with just the 1.8. The other thing to consider is no matter what your weight, 99% of folks are on the same tire package, which I think is important to consider. Power or not, those same tires that the guy running at 1760 has have to support almost 2000 lbs

At least, that's my theory, I'm curious to hear others, that's sort of the point of this thread :)
 
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