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Old 06-07-2007, 10:42 PM   #16
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Default Re: Most important mod for autocross

Try to get a solo school in, one of the best things I ever did. My instructor said that we all just got in 2 years of auto x seat time in one day.

Go for some Falken 615s for some summer auto x / street tires.

+1 for alignment

I would get front and rear sways and run STU and play in there for a while. Thats just me though. Or just take it stock, but get the bolts and an alignment if you don't want to spend much $$$.

Remeber to have fun!!!


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Old 06-08-2007, 05:36 PM   #17
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Default Re: Most important mod for autocross

Camber plates and then alignment
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Old 06-28-2007, 10:10 PM   #18
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Default Re: Most important mod for autocross

The proper mods depend on which class you want to run in.
Note: Best mod in any class in improving driving skill- take courses, talk to experts and get lots of seat time.
In all classes get an alignment with good front neg camber and a rear camber about .5 less than front.

For A stock: R comp tires 245/45-17 or 245/40-17 are the best mod and a 27-29mm Front sway bar is legal too. Nothing else is possible.

For STU: 27-29FSB, 22-26RSB, camber front plates. 225 or 245mm RE070, 01R, advan or 615 tires with tread wear index of at least 140

BSP: R comps, sway bars, camber plates, stage 2 ECU reflash, coil overs,etc
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Old 06-29-2007, 02:55 AM   #19
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Default Re: Most important mod for autocross

Quote:
Originally Posted by XDNBC
The proper mods depend on which class you want to run in.
Note: Best mod in any class in improving driving skill- take courses, talk to experts and get lots of seat time.
In all classes get an alignment with good front neg camber and a rear camber about .5 less than front.

For A stock: R comp tires 245/45-17 or 245/40-17 are the best mod and a 27-29mm Front sway bar is legal too. Nothing else is possible.

Actually, 275/40-17 r-comps for 05+ STi's is best, sway, alignment and adjustable shocks if you can spend the money.
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Old 06-29-2007, 12:01 PM   #20
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Default Re: Most important mod for autocross

Quote:
Originally Posted by rankink75
Actually, 275/40-17 r-comps for 05+ STi's is best, sway, alignment and adjustable shocks if you can spend the money.
Just curious about the effect of using 275/40-17 on 8" wheels. I thought the wheels should be 9-11" wide for those tires. What happens when you use 8" wheels and are at 10/10ths?

The guys here run 245/40-17 r comps on 8" wheels. I am not sure if they have tried other sizes and prefer these, or just picked the widest tires that fit their wheels. Comments?

BTW: In STU our max tire is 245 for AWD cars but 275 for 2WD.
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Old 07-11-2007, 12:26 PM   #21
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Default Re: Most important mod for autocross

Quote:
Originally Posted by XDNBC
For A stock: R comp tires 245/45-17 or 245/40-17 are the best mod and a 27-29mm Front sway bar is legal too. Nothing else is possible.
I believe you can also use the Ohlin struts [NOT coilovers], although they are very costly...

Quote:
Originally Posted by XDNBC
For STU: 27-29FSB, 22-26RSB, camber front plates. 225 or 245mm RE070, 01R, advan or 615 tires with tread wear index of at least 140
Cobb also provides a STU mapping that tunes everything except the boost. Only hitch is that it is tuned for 100 octane. This and the mapping for Stg 2 for BSP also benefit a lot from a protune. STU also offers a lot of upgrades for power as well like a turboback [make sure you keep your cat or you go into SM], uppipe, headers, and others. However that stuff adds up quick in price.


My advice (which I have been getting from everyone in my region) is drive the car stock for at least a year, including tires. Race tires can hide a lot of things that you could be improving on, so you gain a lot more from using street tires which show the mistakes better. Plus, driving a slower and worse handling car forces you to take better lines and learn to use the momentum of the car which are the only ways you are going to go faster once you reach the limit of the stock car.
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Old 07-11-2007, 01:08 PM   #22
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Default Re: Most important mod for autocross

Quote:
Originally Posted by XDNBC
Just curious about the effect of using 275/40-17 on 8" wheels. I thought the wheels should be 9-11" wide for those tires. What happens when you use 8" wheels and are at 10/10ths?

The guys here run 245/40-17 r comps on 8" wheels. I am not sure if they have tried other sizes and prefer these, or just picked the widest tires that fit their wheels. Comments?

BTW: In STU our max tire is 245 for AWD cars but 275 for 2WD.

The wheels are spec'd for 9-11 wide wheels, but they fit fine on the stockers. They are pinched, but still perform better than the 245's which I have run on also. Especially when you upgrade the shocks on a A-Stock sti. Then the 275's are must to the extra grip you achieve.

For STU I run the azenis 245/45 on the stock wheels as well.
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Old 07-11-2007, 01:29 PM   #23
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Default Re: Most important mod for autocross

Interesting note: using a catted Cobb downpipe and stock muffler, and stage 2, 91 octane mapping, I get 16.3 psi max boost in 2nd gear. This is the same as I got with stock boost so it is legal for STU. If anyone protests my car I just need for them to ride with me and check the boost on my gauge. I do use 94 octane gas but don't think that has any effect on boost.
Strange note: I just read where my stock boost should be 14.5 +/- .7, but I got 16.3 and once got 16.7 boost in 2nd gear before I did any mods to my car.

Am I just lucky or is that normal for stage 2 with my setup? I am not aware of the differences in Cobbs STU 100 octane mapping, but I don't seem to need it- and I don't want to use 100 octane gas.

Last edited by XDNBC : 07-11-2007 at 01:40 PM.
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Old 07-11-2007, 02:57 PM   #24
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Default Re: Most important mod for autocross

Quote:
Originally Posted by XDNBC
Interesting note: using a catted Cobb downpipe and stock muffler, and stage 2, 91 octane mapping, I get 16.3 psi max boost in 2nd gear. This is the same as I got with stock boost so it is legal for STU.
That is not correct.
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Old 07-11-2007, 10:54 PM   #25
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Default Re: Most important mod for autocross

What is not correct?
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Old 07-12-2007, 07:32 AM   #26
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Default Re: Most important mod for autocross

It is not legal to tune boost in ST. The rules don't care about initial or final boost levels, you cannot change the map.

XDNBC could install a map with a peak boost of 2 psi at 7K rpm and that wouldn't be legal either.
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Old 07-12-2007, 08:57 AM   #27
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Default Re: Most important mod for autocross

From 2007 SCCA Solo rules Street Touring Class page 80.

E. The engine management system parameters and operation may
be modified only via the methods listed below. Any and all modifications
must meet or exceed the applicable US DOT emissions
standards for the year, make, and model of the car. These allowances
also apply to forced induction cars, except that no changes
to standard boost levels, intercoolers, or boost controls are permitted.
Boost changes indirectly resulting from allowed modifications
are permissible, but directly altering or modifying the boost
or turbo controls, either mechanically or electronically, is strictly
prohibited.
1. Reprogrammed ECU may be used in the standard housing.
Traction control parameters may not be altered. Altered
engine controllers may not alter boost levels in forced induction
engines.

According to the above statement, it seems that reprogrammed ECUs are allowed, and that no changes to standard boost LEVELS are permitted-and that you can not alter boost levels. It does not say that the maps can not be changed or that where the boost levels appear in the rev range must not be altered.

The statement that "Boost changes indirectly resulting from allowed modifications are permissible" is a bit confusing since catted downpipes are legal and this mod definitely speeds the turbo spoolup speed and changes the boost at different revs and probably the max boost also.

Christian- how does the STU map you design differ from the stock map?
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Old 07-12-2007, 10:08 AM   #28
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Default Re: Most important mod for autocross

Quote:
Originally Posted by XDNBC
no changes to standard boost levels, intercoolers, or boost controls are permitted..... Boost changes indirectly resulting from allowed modifications are permissible, but directly altering or modifying the boostor turbo controls, either mechanically or electronically, is strictly prohibited.



From my understanding this means you can not alter anything that controls boost through the ECU, or MBCs.

I believe the reference to changes resulting from modifications is something along the lines of boost creep. If you add in a large enough exhaust [or catless, but that is illegal in STU] you could see boost creep which would put you over the stock boost levels, but because you didnt tune boost, it is legal. You didnt control that boost increased, it just happen to on its own as a result of something else.



Last edited by Jephro : 07-12-2007 at 10:12 AM.
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Old 07-12-2007, 10:19 AM   #29
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Default Re: Most important mod for autocross

The stock boost curve must be maintained for ST classes and thus you can not touch it when tuning. This includes bumping up the rev limit as it could be conceived as changing the boost curve since there was no curve above 7k rpms prior. With typical STU modifications you will get 1-2 psi higher without changing the stock ECU boost parameters. This is acceptable in ST classes as it is a direct result of opening up the exhaust while not touching boost under the rules.

Last edited by rankink75 : 07-12-2007 at 12:57 PM.
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Old 07-12-2007, 10:26 AM   #30
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Default Re: Most important mod for autocross

Quote:
Originally Posted by rankink75
The stock boost curve must be maintained for ST classes and thus you can not touch it when tuning. This includes bumping up the rev limit as it could be conceived as changing the boost curve since there was no curve about 7k rpms prior. With typical STU modifications you will get 1-2 psi higher without changing the stock ECU boost parameters. This is acceptable in ST classes as it is a direct result of opening up the exhaust while not touching boost under the rules.
very well put


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