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Autocross FAQ

54K views 133 replies 47 participants last post by  Steve35 
#1 ·
Thought I would throw together some FAQ's on autocrossing the 3. If you have any to add, I will edit my post with the question and answer.

Here is the current SCCA Solo Rule Book

http://scca.org/documents/Solo Rules/2007SoloRules.pdf



What class does my 3 fall into?

The classes for the Mazda 3i and 3s are:
H Stock
Street Touring S
Street Touring X
F Street Prepared

The classes for the Mazdaspeed 3 are:
D Stock
Street Touring Ultra
D Street Prepared (under the 4 cyl. mechanical induction catchall)

Right now, the only classes that the 3 and MS3 are competitive are in the Stock Classes.

What can I do to my car and remain in Stock?

First, you should always consult the SCCA rulebook for current rules. The Stock Class rules tend to stay consistent, but you should always check if you are thinking of a new mod.

Stock Class basically requires you to run the car the as presented from the factory. The only changes generally allowed are wear items such as tires (any DOT approved tire is allowed, including ‘R’ Compounds), brake pads (any pad can be used), exhaust can be changed after the last catalytic converter, the air filter can be changed.

While it is not a wear item, the front sway bar can be changed as well.

For wheels, you are allowed to use any wheel that is dimensionally the same (width and diameter) as the wheels that came with your model car. You can change the offset by .25”.

Can I use a smaller rim than what came on the vehicle and stay in Stock?

No, you must use the size that came on your model car.

What are R-Compound tires?

Some manufacturers make tires that are specifically designed to be driven on the track. Because many sanctioning bodies require DOT approved tires, the manufacturers design the tires to meet DOT regulations. Some of the tires that fall into this class are the Hoosier A6 an R6, Kumho V710, BFGoodrich G-Force R1, Hankook Z214 (There are more, but these are the top 4 in autocross)

I put a cold air intake in and dropped the suspension. Is this okay for Stock Class?

These mods will put you into the Street Touring classes. Street Touring S (STS) for the regular 3 and Street Touring Ultra (STU) for the Mazdaspeed3.

Okay, what can I do in Street Touring?


First, you should be aware that the Street Touring rules are still new and, as a result, are still changing. What is legal this year may be illegal next year (and visa-versa) If you are going to build a car to the Street Touring Rules you should get a rulebook and stay current with rules changes.

SOME of the things that you can do are:

Suspension mods (lowering, sway bars, struts)

Engine Mods (Cold air intake, emissions legal headers, mounts, accessory pulleys)


Alternate brake pads and rotors (ie slotted or cross drilled) may be used.

Wheels can be any diameter but may only be 7.5” wide.

Tires may have a maximum section width of 225mm. The UTQG Treadwear rating must be 140 or higher. There are some tires that are on the exclusion list, consult the rulebook.

No limited slips allowed.

There is much more that can be done, but that is the gist of it.

Street Touring X adds:

8” Wheels allowed
Maximum tire is 245mm (but the UTQTG rating is the same)
Diffs are allowed.
High Flow cats are allowed.
Alternate Rotors and Calipers are allowed (provided the rotor is the same size or larger than stock.)

Additional changes for STU are:


Maximum tire is 275mm (but the UTQTG rating is the same) on RWD and FWD



What is Street Prepared?

Street Prepared allows more engine work – you are allowed to change anything before and after the head. No cats are required.

Any wheel can be used and any DOT approved tire can be used.

The suspension allowances are a bit more free than in Street Touring.

To be competitive in Street Prepared, you should be prepared to trailer the car
 
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#27 ·
[quote author=astrob0y link=topic=87808.msg2338961#msg2338961 date=1211640675]
quick question, how do they calculate the final time?
[/quote]

They use timing lights. Ths time starts when you trip the lights at the start and stops when you trip the lights at the finish.

Unless it's a ProSolo, in which case the lights start when the tree goes green. :)
 
#28 ·
[quote author=astrob0y link=topic=87808.msg2338961#msg2338961 date=1211640675]
quick question, how do they calculate the final time?
[/quote]

In autocross the timer starts and stops when you trip the start and finish light beam. Typically, the accuracy is down to .001 seconds.

Usually, the winner of a class is deteremined by your best run, so if you have a bunch of bad runs but manage to pull one out of your a$$ on the last run that is the fastest in the class, you win.

National Tours are a bit different. Each person gets three runs on Saturday and three on Sunday. The best runs from each day are added together to determine class winners.

PZ
 
#30 ·
[quote author=astrob0y link=topic=87808.msg2347362#msg2347362 date=1212003030]
Times Total
67.921 54.516
67.956
66.457+1
65.683
65.892+1
65.714+1

I know how they keep track of the times but whats the formula to calculate that?
[/quote]

It looks like the club you ran with is using some sort of factor time. Many clubs do this to 'normalize' times across classes so that in theory if a driver were to drive in two different classes, his final time, after the factor was applied would be the same.

Do you have a link to the results that we can look at. It might help out.
 
#32 ·
[quote author=astrob0y link=topic=87808.msg2347441#msg2347441 date=1212004562]
http://www.ner.org/sites/ner.org/files/event 3_fin.htm
[/quote]

Another New England Region member! :)

Okay, NER runs the PAX/RTP factor for the novice class:

http://www.scca-chicago.com/solo/indexes/rtp2008.html

What this does is allows you to compare your times across classes. A Modified is set at a 1.0 and the numbers drop until HS at .792. Theoretically, if the same driver ran in AMod and HS, and you multiplied the raw time with the factor, you would get the same number.

Your class, STU has a factor of .830, so they were applying that to your time. So even though you ran a faster raw time than the STS car, he ended up higher in the standings because he has a softer factor (the class is not as fast as STU).

Hope this helps.

PZ
 
#36 ·
I didn't feel that this was worthy of it's own thread, so I'll say it here. I took my car to a local auto-x and ran into a problem that people may want to watch out for. A coolant hose that runs from the reservoir to the thermostat housing? (buried under intake, can't see) came loose off of one of the clips on the radiator support. It got cut up by the fan, and I lost a bit of coolant before I realized it. Ended my day earlier than I had anticipated, and almost left me stranded if it weren't for some cool guys helping me out. It's probably due to the rear motor mount and how much the engine moves around which would pull the hose from the clip. Keep this in mind and be sure to check after every run or two just to be safe.
 
#37 ·
Just want to add.

I recently installed my Borla exhaust with race pipe that replaced the second cat.

Before exhaust:
Class: STS (PAX: 0.816):
- Koni Yellows
- Tein H-techs
- RB Rear Sway

After exhaust:
Class: STX (PAX: 0.820)
- Koni Yellows
- Tein H-techs
- RB Rear Sway
- Borla exhaust with race pipe

The ruling was agreed by a few people from the ASA (which is the a local club in Edmonton, AB) that I still had the stock headers (complete with the stock cat) and the second cat was far enough down the line that I would be classed in STX not FSP (or worst M) with the race pipe.

I was willing to take the class change cuz the pax index was a difference of 0.004. So not a big change and the sound is allot better.
 
#38 ·
[quote author=Drunkn Munky link=topic=87808.msg2671668#msg2671668 date=1223334426]
Just want to add.

I recently installed my Borla exhaust with race pipe that replaced the second cat.

Before exhaust:
Class: STS (PAX: 0.816):
- Koni Yellows
- Tein H-techs
- RB Rear Sway

After exhaust:
Class: STX (PAX: 0.820)
- Koni Yellows
- Tein H-techs
- RB Rear Sway
- Borla exhaust with race pipe

The ruling was agreed by a few people from the ASA (which is the a local club in Edmonton, AB) that I still had the stock headers (complete with the stock cat) and the second cat was far enough down the line that I would be classed in STX not FSP (or worst M) with the race pipe.

I was willing to take the class change cuz the pax index was a difference of 0.004. So not a big change and the sound is allot better.
[/quote]

Wow, all that money just to go (in PAX terms) as fast as FS.

Throw some R-comps on there and go FSP! :)
 
#39 ·
Right now I am in Kamloops, BC and the only autocross out here is the Kelowna Corvette club and they follow the old rules so i am in FSP already.  But can't afford R's :(

Beside I'll stick with pax 0.820. I dont want 0.833. For the new rules.

I can just be cheap like others I raced with in ASA and use Bridgestone RE-01's. Street tires that are almost R's. :)
 
#42 ·
Thanks. So next season, I am planning on removing my CAI and rear sway bar so i can run in the H Stock with my v710's. I have a feeling i might be kicking some butt. :p

but boy am I going to miss those things. The CAI gave it such a nice sound and the rear sway just totally change the ball game when it comes to handling.
 
#43 ·
Here is a link to the scca rules http://www.scca.com/documents/Solo Rules/2008_Solo_Rules_2.pdf , in our region there isnt a lot of competition in h-stock and you will probably dominate. Personally i would keep the mods and run in stock prepared and really enjoy the car aand the satisfaction of making if faster with each mod. Does your front struts bottom out, mine do pretty bad, im guessing from the lower 3speed stance. Koni makes dampners available for our car, and would keep you stock class legal. cat back are also legal. I dont know how efficient they are for your car, mine would mostly add a better tone. im thinking about fabricating a cat back with a flowmaster, never heard a bad sounding flowmaster on any car.
 
#45 ·
Sorry if I missed it in the thread- what's the widest 17" R Comp you can mount on a Mazda3 without rubbing or being over the limit for the 6.5 inch wheel. I'm guessing a 225?

And just how competitive is it in H Stock? I'm asking because I have a 350Z in BSP that's not all modded out for the class. They aren't all that competitive in their class (Mazda RX8's are the class leader :lol:)

Besides paying a lot more for the 275's needed for the Z, I wonder if it would be more competitive and cheaper to just run the MZ3 in Stock next year.
 
#46 ·
[quote author=Johnny Law link=topic=87808.msg2690043#msg2690043 date=1223925267]
Sorry if I missed it in the thread- what's the widest 17" R Comp you can mount on a Mazda3 without rubbing or being over the limit for the 6.5 inch wheel. I'm guessing a 225?

And just how competitive is it in H Stock? I'm asking because I have a 350Z in BSP that's not all modded out for the class. They aren't all that competitive in their class (Mazda RX8's are the class leader :lol:)

Besides paying a lot more for the 275's needed for the Z, I wonder if it would be more competitive and cheaper to just run the MZ3 in Stock next year.
[/quote]

You should be able to fit 245 Hoosier A6 on the Mazda 3.

I thought EVOs and STIs are class leader in BSP
 
#50 ·
Thanks for the info PZ.

It might also be worth noting that the Mazdaspeed 3 (and the regular 3 as well) is also legal in:
- Street Modified (SM)
- E Modified (EM)
- X Prepared (XP)

Competing in any of the above will likely result in a trailer-only car and a significantly lighter wallet. ;)

Also, in the latest SCCA Fastrack update, the SAC (Stock Action Committee) dropped a proposal to move the MS 3 from D Stock to G Stock.

I started autocrossing in an Evo back in '03; I've been running a '99 Miata for the past couple years. Just got my 'Speed 3 and while it's not destined for regular autocross duty I'll definitely be bringing it out to an event now and then.
 
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