SCCA Street Touring/TT Tuner Sharing Thread

[simpleisbest]

Hey All,

I'm building my CTR for SCCA (Autocross) Street Touring (BST) and couldn't find any similar threads around, so here is a post about the class to start things off.

For track guys who are interested in SCCA Time Trials, SCCA Street Touring "cars listed as eligible in and prepared to the SCCA Solo Street Touring Rules are permitted to compete in their respective Time Trials Tuner Class. Vehicles with this allowance are not permitted to interchange preparation rules otherwise". (Currently the FL5 CTR/DE5 ITS would be listed in Tuner 2)

For those not familiar with SCCA rules, all allow modifications (allowances) need to be specifically spelled out in the rule book to be allowed; basically "if it doesn't say you can, then you can't".

Below is a VERY VERY basic and VERY VERY unofficial summary (with very possible errors and omissions!!!) of the rules as they apply to the FL5 CTR (the devil is in the details so please make sure you read the rulebook!) for those interested in building their car to class:

(Current 2025 rules can be found here; Rules from Page 87, Vehicle Class listings from Page 202)

STREET TOURING® CATEGORY (Summarized Prologue)
Street Touring allowances and modifications build upon existing Street category allowances.
Competitors in this class are looking to add performance to a select group of vehicles based on performance potential.
Vehicle modifications should not prevent daily use on public roads. “Daily use” is subjective criterion; competitors will interpret this differently. “Street legal” is a category goal. Some states may require more stringent requirements. It is not the intention of “street legality” to be an absolute. It is intended for the majority of the membership. Drivetrain configuration variances are balanced through limited slip differential and wheel/tire allowances.
Performance Improvements Through “Bolt-On” Modifications

• Modifications should not require cutting, drilling, or permanent alterations to body panels.
• Modifications that enhance the performance for Solo® and street driving. Suspension, Differentials, Bolt-On Engine Parts, Aftermarket/Larger Brake Kits, Wheel/Tire Upgrades
• Vehicle Safety Systems. - ABS may be electronically disabled, but otherwise must remain unaltered.
• Required Diagnostic Systems. - OBD2 systems should remain functional. - Retention of specific emissions systems.
• Engine Tuning.

(Summarized Allow Modifications)

Engine

• Engine Internals & turbo must stay OE.
• Intake (up to turbo inlet) allowed (“existing structure of the car may not be modified for the passage of ducting from the air cleaner to the engine inlet”). PCV valves and or engine management components in the air intake system mass airflow sensors, may not be removed, modified, or replaced, and must retain their original function along the flow path.
• Compressor Bypass Valves (CBVs), blow-off valves, and pop-off valves may be replaced or modified.
• Boost regulation systems, either electronic or mechanical, and electronic fuel cuts referencing boost pressure may be modified, replaced, or removed. This does not allow for changes to the turbocharger or wastegate (including wastegate spring).
• Charge pipes allowed (Modification or deletion of vehicle components (e.g. plastic shrouds, wheel well liners) to permit routing of alternate charge pipes is not allowed)
• Intercooler allowed (“Body panels, fascias, or structural members may not be cut or altered to facilitate charge air cooler installation. Removal of vehicle components to facilitate installation is not allowed. Holes may be drilled for mounting”)
• Downpipe (catted; 3” or longer and 100cell or higher), exhaust allowed. O2 sensor can be relocated. Note - “Exhaust heat shields which cover only, and attach solely to, these parts may also be replaced, removed, or modified. All other exhaust heat shields may be modified the minimum amount necessary to accommodate allowed alternate exhaust components”
• Oil pans allowed (Addition or modification of windage trays or crankshaft scrapers is not allowed)
• Engine mounts may be replaced (must use OE mounting points)

Fuel

• 93oct - "Street Touring® category vehicles will use fuel which is “Federally approved for use on public highways,” and is widely distributed and typically sold in filling stations, commonly called “pump fuel” with typical octane ratings or AKI (AntiKnock Index) (R+M/2) displayed on the pump between 87 and 93. The maximum octane rating allowed is what is typically delivered from a pump marked 93 octane*. Fuels comprised of more than 15% ethanol may only be used when specified by the manufacturer (e.g., in the owner’s manual for flex-fuel vehicles). *Octane verification: Octane levels will vary from the number listed on 42 — 2025 SCCA® National Solo® Rules 3. Vehicles the pump. Octane testing has a “margin of error” and different testing procedures will produce similar but different results. For the purposes of testing gasoline, a result that exceeds 95.9 octane is not allowed and will result in a disqualification with no exceptions (hard limit). This limit gives competitors a 99.99+% confidence level that fuel purchased from a pump marked 93 octane is compliant. Warning: Competitors attempting to approach the 95.9 octane limit through mixing or by any other means may inadvertently create fuel that appears compliant but may test above the 95.9 hard limit."

Battery

• Any battery with same voltage. Battery can be relocated. Additional grounding cables allowed.

ECU Tunes

• ECU reflash and/or in-line electronics (ie, RaceChip…) allowed. Replacing accessory pulleys/belts, crankshaft damper pulleys allowed.
• Any OE OBD2 or newer communications port functionally must remain. The Check Engine Light (CEL) or Malfunction Indicator Light (MIL) may be disabled via software. Only sensors equipped from the manufacturer may be used for engine management

Transmission/Drivetrain

• Any mechanical shift linkage (ie, short shifter)
• Any mechanical LSD unit allowed.
• Clutch pressure plate and disk maybe replaced.
• Transmission mounts may be replaced (must use OE mounting points)
• Steering rack bushings allowed (Steering rack position may not be changed. The amount of metal in a replacement bushing may not be increased relative to the amount of metal found in a standard bushing for the particular application. Solid metal bushings are specifically prohibited. This does NOT allow shimming or otherwise relocating the steering rack.)

Cooling

• Engine Oil/transmission coolers allowed; “Modifications necessary to route fluids to an appropriate heat exchanger (modification of oil and coolant lines, addition of oil cooler sandwich adapters, addition of fluid pumps, etc.) is allowed provided they serve no other purpose”.
• Any radiator allowed (core and fluid capacity cannot be smaller than OE)

Suspension

• Any shocks/springs/coilovers. Springs must be in original mount locations. Geometry cannot be changed.
• Coil spring perches may be changed or altered and their position may be adjustable. Spacers are allowed above or below the spring.
• must use the original spring attachment points (rear springs must remain divorced type)
• multiple springs allowed, as long as they use the original mount locations (ie, helper springs)
• Suspension bushings can be replaced but must be the same type.
• Any sway bar allowed
• Any 2pt strut bar allowed
• Bolt on subframe connectors allowed (fore-aft only). No cross-car/lateral/triangulated connectors allowed.

Camber Allowances

• (Front) Camber plates OR Lower Ball joint (equals modified lower arm) allowed.
• (Rear) Camber kits allowed but can only change only 1 lateral link per corner (The replacement arms or mounts must attach to the original standard mounting points. All bushings must meet the requirements of Section 14.8.B.)

Brakes

• Any brake calipers but number of pistons must be equal or greater than OE. Any rotors, but diameter must be at least equal to OE. Any brake lines. Air ducks allowed.

Wheels/Tires

• Any diameter wheel up to 11” width. Approved tires up to 200tw up to 315 in width.

Interior

• Race seats minimum weight 25lbs (includes mounting hardware) and use OE mount points. The seating surface must be fully upholstered
• Any steering wheel may be used. An alternate steering wheel assembly, including all mounting hardware which replaces an airbag-equipped wheel, is not required to have an airbag but must weigh at least as much as the standard assembly. An alternate steering wheel is not required to have a horn button.
• Pedal cover kits and other interior cosmetic accessories may be added. “Dress-up” items such as chrome dipsticks and non-standard filler caps are permitted, provided they serve no other purpose

Exterior

• Fenders may be rolled, but not cut or flared.
• OEM optional accessories (ie, CF spoiler) can be used; exact replicas permitted.

There is probably a lot of areas and nuisances that this summary is missing, but I tried list all that I think would apply for us.

NOTE - Radiator expansion tank allowance is currently under review by SCCA, so if approved then we should be able to upgrade that as well.

Please feel free to add or re-define as this thread progresses.

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[optronix]

This is pretty great. I'm def a noob when it comes to SCCA classing but BST seems like the next step up (or down, depending how you look at it...) competitively vs B Street, which you're kicked off the island for having wheels more than +/- 7mm offset than OEM.

I was dorking around with this last week and was having a pretty hard time finding definitive evidence that my adjustable lower ball joints were allowed. Turns out it's explicitly called out in your post. Cool!

The only other question I'd have is around the turbo inlet I just had installed:

Intake (up to turbo inlet) allowed

By "up to" I'm assuming including?? I can't imagine it provides that much of a competitive advantage.

Other than that, seems that the keys to success will be dialing in camber, tire width, and engine tuning for FL5/DE5. Anyone know what cars are finding the most success in BST as of this moment?

 

[simpleisbest]

This is pretty great. I'm def a noob when it comes to SCCA classing but BST seems like the next step up (or down, depending how you look at it...) competitively vs B Street, which you're kicked off the island for having wheels more than +/- 7mm offset than OEM.

I was dorking around with this last week and was having a pretty hard time finding definitive evidence that my adjustable lower ball joints were allowed. Turns out it's explicitly called out in your post. Cool!

The only other question I'd have is around the turbo inlet I just had installed:



By "up to" I'm assuming including?? I can't imagine it provides that much of a competitive advantage.

Other than that, seems that the keys to success will be dialing in camber, tire width, and engine tuning for FL5/DE5. Anyone know what cars are finding the most success in BST as of this moment?

Glad to hear this thread is helpful already!

The lower ball joint is allowed as a modification/replacement of the lower arm.

Yeah, turbo inlet tube is allowed as you can change intake pieces that connect to the turbo inlet point.

Current BST class leaders are the Subaru STI and Mitsubishi Evo 8/9. BMW E92 M3, Nissan 350/370Z, Toyota GR Corolla, Porsche Cayman S (987), Ford Focus RS, and Mitsubishi Evo X are also very competitive it seems. There is definitely good competition to be had!

Power to weight wise, the CTR should be in the mix.

 

[simpleisbest]

Here's my build list so far:

OS Giken LSD
Eventuri Intake
TSP Catted DP w/PTP blanket
Remark Ti Exhaust
PWR Intercooler
HPS Chargepipes
Spoon Engine/Transmission mounts
Anti-gravity Battery
Hondata ECU Tune
Karcepts Rear Sway Bar
Titan7 T-P10 18x11 +44(f), 18x9.5 +53(r)
Bridgestone RE71RS 295/30-18 or Yokohama AO52 295-30-18(f); Yokohama AO52 255/35-18(r)
KW Race V4 Coilovers JRZ Series 11 2-way Coilovers
Eibach Front Endlinks

Race seat - TBD (if needed)

 

[simpleisbest]

Picking parts that are legal for class is always tricky.

While it's pricey, the PWR intercooler does meet the letter of the rules, as the it fits with no modifications to the stock plastics, including the temp sensor mount. From what I see most of the larger ICs out there all require the temp sensor mount to be cut and sensor relocated, which is not allowed. The Wagner IC might be another legal option, but I am not sure what modifications to the stock plastics are needed for install.

Pics for reference and sensor circled in red

 

[simpleisbest]

With the TSP downpipe potentially generating additional heat, I optioned for the PTP heat shield. While it seems to do a good job keeping under the hood temps down, you cannot fit the stock turbo shield around it.

Class rules do not have a specific allowance ("if it doesnt say you can, then you cant") for an aftermarket turbo blanket, but do allow you to modify the surrounding OEM heat shields to fit any heat shielding you do for the downpipe...so I took a cut-off wheel to the OEM turbo shield

 

[optronix]

With the TSP downpipe potentially generating additional heat, I optioned for the PTP heat shield. While it seems to do a good job keeping under the hood temps down, you cannot fit the stock turbo shield around it.

Class rules do not have a specific allowance ("if it doesnt say you can, then you cant") for an aftermarket turbo blanket, but do allow you to modify the surrounding OEM heat shields to fit any heat shielding you do for the downpipe...so I took a cut-off wheel to the OEM turbo shield

This is an example where I'd rather ask forgiveness than permission. Who's going to contest a turbo blanket? Although I do recall seeing something about the heat shield... I figured that was more related to aftermarket turbos. Maybe that's where you'd get a contest, is if someone thought you were trying to hide one?

Also though I highly doubt you'll run into heat soak issues during autocross... and TBH I've been skeptical of turbo blankets/heat wraps since the 90s. I've seen more personal anecdotes of them doing more harm than good than the other way around. Probably why I skimmed over the heat shield stuff when I was poring over the rules.

I flip back and forth between wanting to stay compliant and IDGAF. I'm drifting more towards just buying a Miata and getting serious with that.

 

[simpleisbest]

This is an example where I'd rather ask forgiveness than permission. Who's going to contest a turbo blanket? Although I do recall seeing something about the heat shield... I figured that was more related to aftermarket turbos. Maybe that's where you'd get a contest, is if someone thought you were trying to hide one?

Also though I highly doubt you'll run into heat soak issues during autocross... and TBH I've been skeptical of turbo blankets/heat wraps since the 90s. I've seen more personal anecdotes of them doing more harm than good than the other way around. Probably why I skimmed over the heat shield stuff when I was poring over the rules.

I flip back and forth between wanting to stay compliant and IDGAF. I'm drifting more towards just buying a Miata and getting serious with that.

Yeah basically destroying brand new components vs being able to replace is super lame

Some of the local SCCA regions I race with can get pretty strict and I plan to compete at National events, so the decision for me was pretty clear. Much really depends on the tribal culture of your local region and the attitude of your fellow competitors....especially if you start winning

So the turbo blanket thing got successfully protested a few years back at Nationals with an Fiat 124S in STU iirc, so there is precedent against it.

Heat soak during an autocross run is unlikely, but if ProSolo somewhat possible? My desire mitigate the heat from the downpipe was more a concern with all the plastics in the area as I will occasionally mix in HPDE events too.

 

[optronix]

Yeah basically destroying brand new components vs being able to replace is super lame

Some of the local SCCA regions I race with can get pretty strict and I plan to compete at National events, so the decision for me was pretty clear. Much really depends on the tribal culture of your local region and the attitude of your fellow competitors....especially if you start winning

So the turbo blanket thing got successfully protested a few years back at Nationals with an Fiat 124S in STU iirc, so there is precedent against it.

Heat soak during an autocross run is unlikely, but if ProSolo somewhat possible? My desire mitigate the heat from the downpipe was more a concern with all the plastics in the area as I will occasionally mix in HPDE events too.

Yep, it's more to protect the surrounding elements, I get that. I just also recall coking issues from the 90s, but fortunately that is one of few things that has actually improved since then .

 

[BigBird]

Here's my build list so far:

OS Giken LSD
Eventuri Intake
TSP Catted DP w/PTP blanket
Remark Ti Exhaust
PWR Intercooler
HPS Chargepipes
Spoon Engine/Transmission mounts
Anti-gravity Battery
Hondata ECU Tune
Karcepts Rear Sway Bar
Titan7 T-P10 18x11 +44(f), 18x9.5 +53(r)
Bridgestone RE71RS 295/30-18 or Yokohama AO52 295-30-18(f); Yokohama AO52 255/35-18(r)
KW Race V4 Coilovers
Eibach Front Endlinks

Race seat - TBD (if needed)

this is a sweet build!

Along the lines I was looking at as well for my TT Tuner 2 build.

 

[simpleisbest]

So 315s fit in the front
(I did not check fitment for the rear) While no rubbing so far on Stock suspension, I might need to use wheel spacers with coilovers.

 

[BigBird]

So 315s fit in the front
(I did not check fitment for the rear) While no rubbing so far on Stock suspension, I might need to use wheel spacers with coilovers.

I didn't realize with them moving most of the T3 cars to T2 that they kept the old tire widths for T2. This is interesting

 

[sackofcheese]

So 315s fit in the front
(I did not check fitment for the rear) While no rubbing so far on Stock suspension, I might need to use wheel spacers with coilovers.

This is an absolutely nutty amount of tire that can fit

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