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Old 07-22-2013, 01:59 PM   #1
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Default The Auto-x thread... share stuff here!

I know this forum is more track focused and I'm thankful for that. However, I know a handful of us auto-cross on a regular basis. I'm also extremely tired of some of the keyboard engineers on m.net and I would like a place to express and exchange ideas in the classes we usually run(STS, STR, CSP, SSM, etc).


I run a 99 sport in STR, here's my basic mod-list:
Xida-S 700/400
15x9 6ULs
225/45/15 BFG Rivals(right now)
RB hollow front-sway, 949 end-links, no rear
ES poly bushings motor mounts, diff, and control-arms
brake pads, organic(yup) front, Carbotech AX6 rear
Custom "cold-air" intake
RB header
Custom exhaust, high-flow cat, Borla resonator
DPtune ecu "reflash"
2140lbs with a gal of gas, which means I need to drop weight!




I did have a 94 R that was prepped similar to this, save the bushings and a lot less power. I bought this 99 already prepped, so I'm happy I got it I've done 1 tour with the car thus far, Blytheville in July. I had a pretty terrible performance, driving like a nanny-boy on the grippy concrete, but my co-driver was leading after day 1 ahead of a previous national champ! He ended up 3rd after day 2 which was very respectable and netted us a tire. I ended up mid-pack, 8th or something like that easily could of been in the trophies though.(coulda,shoulda,woulda)

I'm wanting to drop weight, obviously. I still have the stock battery that I need to replace, replacing the stock seats may net me another 10lbs but I really want better bracing. Going to the edge of the rules, I could get the Wilwood BBK and 2-piece rotors. Only issue I could see with that is if the base compound of brake pads that wilwood sends out is weak enough to keep the brake bias down in the front. A local guy did that mod on his 03 that he did a CS conversion on and he told me the bite wasn't any stronger than a Hawk HPS. I could also get aluminum/tubular lower control arms, as I've been told and how the rule-book reads you can replace one of the control arms(top or bottom) on the car. I figure the lower arm is heavier. If I do that, I'll post RESULTS of that mod and I won't ******* speculate and question it until I have DATA.
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Old 07-22-2013, 02:08 PM   #2
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Here's mine. It's still very much in the teething stage. Nothing special underneath, just not much weight anymore.


revalved Konis currently 700/400 springs, but that's probably going to change before too long.
13x7's running R25 Hoosiers.
Stock 1993 motor, trans, diff.
Megaquirt 1 ecu.
1640ish pounds with more to take off.



The lower arms are definitely heavier.

Don't forget you can use the ebrake to get some heat in the rear brakes before your run. I'll bet you can get some custom made pads if you really need them. Maybe even bandsaw down a set of crappy F350 pads, or something similar.

You'll definitely drop a couple pounds from the seat. Even if you don't drop pounds, you'll get that weight much lower than it is now.
Can you take out the radio legally in an NB?
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Old 07-22-2013, 02:36 PM   #3
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No autox experience, but my MOMO nets me 15lbs on the driver's side alone. Not to mention the amount of car control and confidence it'll give you.
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Old 07-22-2013, 02:40 PM   #4
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The lower arms are definitely heavier.

Don't forget you can use the ebrake to get some heat in the rear brakes before your run. I'll bet you can get some custom made pads if you really need them. Maybe even bandsaw down a set of crappy F350 pads, or something similar.

You'll definitely drop a couple pounds from the seat. Even if you don't drop pounds, you'll get that weight much lower than it is now.
Can you take out the radio legally in an NB?

I'm always amazed when I see DP cars. So wide, so light, and they put down insane n/a power. Will you be going with a VVT engine on yours?


I grab the e-brake on my first run to get some sort of heat in the rears. I was also told about cutting down some of the compound on the pads, dunno how well it would work out on the street though lol.

Lower weight is better, I forgot about that plus. I believe the sport came with a no-radio option so I could take out the radio, but I DD the car currently so I'll be keeping it for now. I'm wondering how much weight I could save by removing the rest of the a/c components under the dash.
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Old 07-22-2013, 03:39 PM   #5
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Yep, getting the weight out of the car is priority #2(behind getting the suspension right), and getting it down in the car is priority #3.


I don't think cutting surface area will do a whole lot to help, since bias is generally a function of hydraulics more than pad area.


Getting the A/C components out of the dash will certainly help, but I think you're only talking 10lbs though.

I'm staying with the 1.6. I don't believe that the 1.8 is worth the 200 pound penalty.
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Old 07-22-2013, 04:07 PM   #6
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In ST, the FM LBBK on all 4 wheels will be near perfect. According to my math. If your year has a prop valve you'll want more aggressive pads in back, but only slightly. The less braking decel you can make the more aggressive you want the rear pad to be. On hoosiers, even pads with the LBBK should work with stockish proportioning.

Speaking of weight, my car in SSM is currently 180 pounds over weight. But I have to run with almost a full tank because my -044 setup has a shitty fuel pickup. So theres about 60 pounds that can come out by only running 2.5 gallons in the car if I fix the pickup. Thats a really cheap 60 pounds to take out of the car. It ran well at the Devens tour last weekend. And as anyone who's driven it can attest to, aero works.
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Old 07-22-2013, 04:11 PM   #7
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I'm wondering how much weight I could save by removing the rest of the a/c components under the dash.
I've read some people who think it's really hard to get the evaporator out, maybe that's true on an NA but I did it on my NB and it was easy. Take out the glove box (and, in my case, the Hydra that's attached behind it), a couple of clamps, and it pulls out. The $15 Mazdacomp AC delete pipe goes in where it used to be, and there are 3 plugs for the holes it would otherwise leave. It was less than 10 pounds, but it took maybe 30 minutes tops, and the heater blower definitely works better now that it doesn't have to push through the evaporator heat exchanger.

--Ian
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Old 07-22-2013, 04:18 PM   #8
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Mine felt like a lot more than 10 pounds. I know for sure that all NA8s have to have the condenser in ST, not sure if the factory non-a/c NB had the condenser already installed or not.
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Old 07-22-2013, 04:44 PM   #9
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Leafy,
Are you running the stock tank? Your car is the first time I've ever heard a miata not being able to run near dry. Can you guys run a small fuel cell? That's on my list to get another 10-15lb out of the car, a 3G cell.
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Old 07-22-2013, 04:56 PM   #10
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Leafy,
Are you running the stock tank? Your car is the first time I've ever heard a miata not being able to run near dry. Can you guys run a small fuel cell? That's on my list to get another 10-15lb out of the car, a 3G cell.
Yes, stock tank, the -044 pickup is just terrible for auto-x with high g-loads. Stock pump I could run down to 1/2 gallon and be fine on street tires. With the -044 on street tires last year I could run down to 1.5 gallons. With the -044 on hoosiers with aero, I need like 5/8th of a tank on the gauge. When I discovered this a couple weekends ago I swore the pump must have like come off the support and was just flopping around.
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Old 07-22-2013, 05:12 PM   #11
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I know my car has ran extremely low on fuel almost since it was new. I'm wondering how hard that is on my fuel pump. I guess I'll find out whenever the pump fails lol.

30 minutes and $15 is worth a little under 10lbs to me. I know the sport had an a/c delete option so it would be legal for me.
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Old 07-22-2013, 05:14 PM   #12
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30 minutes and $15 is worth a little under 10lbs to me. I know the sport had an a/c delete option so it would be legal for me.
Yes, but did the non-A/C sport come without a condenser?
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Old 07-22-2013, 06:35 PM   #13
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Yes, but did the non-A/C sport come without a condenser?
99% sure it didn't
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Old 07-22-2013, 07:43 PM   #14
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It's easy to tell if you've got an engine bay photo, because the fittings for the AC lines on the condensor stick through the firewall. If there are rubber plugs in those holes, then there's no condensor behind the dash.

The AC delete pipe is a plastic part clearly designed for expressly this purpose. It's molded plastic with a corrugated pipe in it, there's no way they spent the upfront capital costs on that just to sell a thousand of them for $15 each through Mazdaspeed as Spec Miata parts. It's gotta be a factory part that was used on the production line.

I know basically nothing about the ST rules -- I run my car in a local class called 'OSP' (similar to XP nationally, except with DOT R comps not full slicks).

--Ian
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Old 07-22-2013, 07:58 PM   #15
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It's easy to tell if you've got an engine bay photo, because the fittings for the AC lines on the condensor stick through the firewall. If there are rubber plugs in those holes, then there's no condensor behind the dash.

The AC delete pipe is a plastic part clearly designed for expressly this purpose. It's molded plastic with a corrugated pipe in it, there's no way they spent the upfront capital costs on that just to sell a thousand of them for $15 each through Mazdaspeed as Spec Miata parts. It's gotta be a factory part that was used on the production line.

I know basically nothing about the ST rules -- I run my car in a local class called 'OSP' (similar to XP nationally, except with DOT R comps not full slicks).

--Ian
Its factory on NA6's with no A/C that is for sure. I dont know about the NB's though. Tomorrow called mazdaspeed and find out, thats how we going the final word on NA8's.
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Old 07-22-2013, 08:18 PM   #16
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Yes, stock tank, the -044 pickup is just terrible for auto-x with high g-loads. Stock pump I could run down to 1/2 gallon and be fine on street tires. With the -044 on street tires last year I could run down to 1.5 gallons. With the -044 on hoosiers with aero, I need like 5/8th of a tank on the gauge. When I discovered this a couple weekends ago I swore the pump must have like come off the support and was just flopping around.
That's nuts. I was able to run my ES car BELOW E. Granted it was only V710s.. but still.

Looking at the rules, looks like you can put in a 5 gallon cell, and baffle it. That should drop another couple pounds, and fix your pickup issue.
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Old 07-22-2013, 08:27 PM   #17
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Looking at the rules, looks like you can put in a 5 gallon cell, and baffle it. That should drop another couple pounds, and fix your pickup issue.
Or pull the stupid 044 out and put in a DW300, Walbro 255 or Walbro 400, or any of the other half-dozen pumps that fit in the stock location and have none of the 044's stupid problems.
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Old 07-22-2013, 08:28 PM   #18
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Or pull the stupid 044 out and put in a DW300, Walbro 255 or Walbro 400, or any of the other half-dozen pumps that fit in the stock location and have none of the 044's stupid problems.
Thats the plan.
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Old 07-22-2013, 08:32 PM   #19
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I'm fairly certain the delete option did not come with a condenser. I know the CS didn't have a/c nor a condenser, rubber plugs in the holes. They probably used the same parts for the CS from the a/c-delete in the sport. I may be over-assuming a lot of things. I won't fret too much on this, though lol.


I had a much more experienced and better driver, drive my car yesterday. He has a highly competitive STS car that he normally drives. He matched my best time on this single run, lol. He also out-rawed me by a few tenths in his STS car :(


He sad the car felt almost numb, maybe had some to do with the rivals and p/s. But he suggested stiffer springs for my 2140lbs. So I may swap in 800/450 springs, I think it will help especially on concrete.

For comparison, here's my run:
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Old 07-22-2013, 08:40 PM   #20
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This was my tour co-driver's first run in the car, he'd been driving HS on street tires all year (aka the slowest possible class). I think it was a 62.5 + every apex cone on the course.


My fast run didnt get recorded I think this was my fastest that got recorded and the only time I locked up the fronts trail braking.





On the springs. 800/550 would be silly on street tires. Much too rear biased and IMO too stiff for streets to work at a-x speeds. I ran streets with 840/506 once, and that was enough the car just didnt feel good and it was much easier to slide than with the 650/400 setup I was running on the xidas.
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