2025 SCCA Time Trials Rules - General Discussion
 

Hey everyone,

This topic started up in someone else's engine swap thread but instead of filling their thread with this discussion, I figured we should move it here instead.

Anyway, here was the latest SCCA Fastrack on the proposed rules changes for Time Trials for 2025: https://timetrials.scca.com/downloads/73768/download

I have questions but I'll put them in response to this post.

OK, my question is about classing because I'm thoroughly confused with the 2024 rules and the 2025 rules when it comes to my new mod.

I'm adding a turbo to my 2013 BRZ.

Reading the 2024 rules, there is a section in the Max Category Authorized Modifications section that states:
"6. CATEGORY - ENGINE AND DRIVETRAIN - 2. Max Category - Intake - Intakes are unrestricted. Forced induction may be added."

So, using that as a guide, it would appear that I'm still allowed to run in Max 4 per the 2024 rules?

I'm still not quite sure how to interpret the 2025 rules yet but even the 2024 rules are not quite clear.

I'm an IT architect for a living and work in infrastructure. Details are my life. If I'm struggling to interpret these rules then I can only imagine what other people are going through. :lol:

For fun, I asked ChatGPT to tell me what class my car would fit in based on the online Time Trials rules. Here is what it tells me:

Based on the 2024 SCCA Time Trials rules, your 2013 Subaru BRZ with a 2.0L engine and added forced induction would likely fall into Max 4 (M4), assuming it meets the following criteria:

Vehicle Weight and Production: M4 allows production vehicles weighing at least 2,200 lbs. (with driver) and produced in quantities exceeding 1,000 units, which your BRZ likely satisfies.

Forced Induction Eligibility: M4 specifically permits unmodified single-unit forced induction 4-cycle engines, provided they align with the natural aspirated displacement limit of 2.9L or less. Since your BRZ's 2.0L engine remains unmodified aside from the forced induction, it fits within this framework.

Engine Modifications: M4's definitions distinguish between modified and unmodified engines. Your car's eligibility would hinge on whether the forced induction was added without altering key components such as the turbocharger housing, compressor wheel, or intake manifold beyond authorized modifications​.

It would be wise to double-check all details regarding your specific modifications and vehicle setup with the event's technical inspection team or the SCCA Time Trials Board to confirm compliance​

My brain was coming up with that as well but I'm curious as to what others think.

You will be Max 2 with added force induction

It's crazy that not even AI can figure out the ruleset. The reason I'm saying that is because of this:

"Forced Induction Eligibility: M4 specifically permits unmodified single-unit forced induction 4-cycle engines, provided they align with the natural aspirated displacement limit of 2.9L or less. Since your BRZ's 2.0L engine remains unmodified aside from the forced induction, it fits within this framework."

I understand what you're saying too but the fact that the rules are so difficult to translate without help is probably one of the reasons that other organizations are attracting people. FFS

I am still trying to figure out what they are accomplishing with this new classing. Max 2 is going to end up with a huge variety of cars and max 3 encompasses one small group of cars? Added FI on unmodded Max 4 car should be max 3.

That was my thinking too. Especially when you consider that there is a pretty specific limit to how much performance I could squeeze out of a stock engine even with FI. I could certainly see my car ending up in M2 with a IAG block and ~400+whp.

Also, to be clear, I'm getting old so my need to "compete" isn't as high. I'm interested in doing this for a level of fun (still competitive to a point). I'm not doing this as a gateway to higher level racing.

I’m in the same boat but what a mess.

Isn't the SCCA all protest-based classing? Maybe we should just class whatever we think and let someone protest. :bellyroll:

AI is pretty bad about most stuff but this sort of thing is where it's truly terrible, where it has to see that the word modified has a specific meaning.

But yeah where it got it wrong is that adding forced induction means you're modifying it to be forced induction. That's what modifying means in this context, modifying whether it has forced induction. So it is Max 2. I do agree they could word it better, and it looks like that's a large part of what they're trying to do with the changes in 2025. Now it says Modified or Added forced induction on a <2.9L motor which hopefully would be clearer to you.

I agree that what you're doing ideally would be max 3 in a perfect world where every car was evaluated individually, but there's no way to make rules for that outside of going full NASA and requiring dynos on site which has its own problems. If you make a ruleset that is simple with very few words and with few classes, and you have people that are just building what they want and not building to the ruleset, then those cars are usually not going to be as competitive as possible.

Like with your rule of turbos only moving a car up one class, someone could build an 800 hp S2000 and that would be very silly in max 3.

The good news is usually for SCCA TT nobody is built properly to the ruleset, and driving ability is all over the place, so cars that are nowhere close to ideal win on a regular basis. Just have fun and probably the other people in max 2 will be similar levels of prep, if they're not then you can always compare to people's times in max 3 or wherever you think your car should fall.

Agreed on AI. My real point is that if a simple logic engine/dictionary (and that's all AI really seems to be at this point) can't deduce the rules then the average driver is probably going to struggle and rely just on interpretation from other drivers which is just crazy.

Also agreed about the classing result. I think the point about an S2000 is that the rules can be manipulated without good guardrails.

Lastly, that point about prep is spot on. I ran in M4 in 2023 in my E85, NA BRZ with no aero against similar cars with full aero. Yeah, I'm sure you can imagine the result. However, driving skill is really key and things like aero probably make more difference than more power. However, more power is very seductive. :lol:

In any event, my point of starting this thread was figuring out/complaining about classing. I'm sure there is more that others might want to talk about though.

Are there any new restrictions or allowances for vehicle modifications under the new rules, especially concerning engine swaps or other major upgrades?

What I've generally observed with the SCCA is that they don't really change class allowances all that much. They do like to move cars around the classes however. I guess that fits a basic philosophy but it feels backward to what other organizations seem to be doing. I'm not sure if I think either one is right/wrong/better/worse but that's what my opinion is (right now). :lol:

That is the thing though. With the old rules you couldn’t have a turbo 800hp S2k in max 3. Added forced induction was up one class, engine modifications(which mean anything not bolt on) was another class. So it would be max 2 since you ain’t doing 800hp on an S2k without a built engine. That is why I never installed a couple reliability mods to my car, they were inside the engine mods and would be max 3 even with no performance gain.


SCCA TT in my area was to the rule set. I saw them make a mostly stock Civic go into max because he didn’t have a rear bumper.