Proposal: Allowing Addition of Forced Induction in Modified

[Loren]

Could a simple rule with power to weight ratio to be qualified to stay or bumped up a class work?

If we did that, we'd have to base it on factory hp and weight numbers, which are either hard to come by, or vary depending on the source. But, we could. Could also do a displacement limit.

In both cases, while it would be a good limitation of the potential "fast cars getting faster" (which they already can, this is just a different way to do it), would also put an arbitrary limit on what is a "slow car". Pros and cons to anything.

[Native]

Aside from my own interest here (I really am going to do the SC at some point. No really. Stop laughing.), there is an inequality in the M classes:
One can swap an engine, and get up to a 25% power increase without having to bump.
One can modify an engine with factory forced induction, for (presumably) less than 25% power increase, and not have to bump.
But if one chooses to add forced induction for said power, one has to bump no matter what, even if it's less than 25%.
That's not fair.

[twistedwankel]

Limit throttle body diameter?

[Loren]

Limit throttle body diameter?

How would it be implemented, and how would it be verified?

More importantly, would it actually solve the problem? Well, if we went to a "restrictor plate", it could. But, we're not going to do that. Otherwise, looking at stock systems... what's the "bottleneck"? We could limit them to stock throttle body diameter, but is that the bottleneck? If you're running 5 psi of boost, with no intercooler and no fuel beyond what the factory injectors can supply... is it going to make a difference if you fit a larger diameter throttle body?

I don't think it would.

[twistedwankel]

https://www.jegs.com/tech-articles/superchargers.html

Jegs made a really good read here. The Table 1 makes me believe any more than 2-3psi in an engine over 9:1 compression would kill it.

**The above chart shows the effective compression ratio of your engine, which combines the static compression ratio with the amount of supercharger boost. Note that for most street applications with 92 octane pump gas, you should keep your effective compression ratio below about 12.0:1.

**To run boost levels from 6 to 10 pounds we recommend the following:
Forged blower pistons with a static compression ratio of 7.5:1

[mdw1000]

https://www.jegs.com/tech-articles/superchargers.html

Jegs made a really good read here. The Table 1 makes me believe any more than 2-3psi in an engine over 9:1 compression would kill it.

**The above chart shows the effective compression ratio of your engine, which combines the static compression ratio with the amount of supercharger boost. Note that for most street applications with 92 octane pump gas, you should keep your effective compression ratio below about 12.0:1.

**To run boost levels from 6 to 10 pounds we recommend the following:
Forged blower pistons with a static compression ratio of 7.5:1

I ran 5 psi on a Renesis for several years with no issues for the motor, including several track days. I put between 20 and 30k on the setup. My buddy that bought it put another 10 or 15k on it. Would it have eventually blown sooner than if it had been left stock? Sure. How soon, I don’t know.

For track use it needed cooling upgrades. Never ran it in autocross conditions, but it wouldn’t have needed them for that.

[Jamie]

Looking at the MSM vs. an NA Miata in particular, they're classed in the same SCCA "Street" class....

That statement seems to be the basis for your proposal, but how many other cars have a factory-boosted and naturally-aspirated models in the same Street class? Off the top of my head, I can't think of many...maybe the Dodge Omni, if you can find one. Certainly not any of the Ford hatchbacks. Not MINIs. So your Miata example might be a unicorn, and even that doesn't hold up under all conditions. Substitute an NB -- better yet, an NB2 -- for your NA, and your balance no longer exists. And then, of course, are cars with no FI-equipped equivalent, like the Mirage. For those, we don't know whether the "factory turbo" car would be classed the same as the NA car...that's an assumption you're making.

As far as "trying to make it work", you've restricted fuel flow, you've restricted charge cooling...the only other thing I can think of is to restrict intake air flow. Mandate the stock throttle body and intake manifold. You'll be able to push more air in, but only so fast, and with no flow improvements.

"Wanting a little more power to be competitive in M4?" Methinks you protest too much...you've built a car on par with any other HS-based car under the FAST rules. If you want to keep proving the underdog, stick a turbo in it and see what it makes of M2. Prove it a failure before changing the rules to favor it.

[twistedwankel]

I ran 5 psi on a Renesis for several years with no issues for the motor

We're probably straying from Loren's thread but:

The weird thing about the Renesis is that it's only running on 2 air ports until 5000rpm then opens the 1/3rd more air and fuel until 9200rpm fuel kill. I assume that would suck the lungs out of a small supercharger or turbo until it caught up again? You would know. On a track you'd probably always be over 5k so a moot point? I never figured out the cfm for the 1.3 or know how to covert that info from psi into compression ratio. Just look at a table and believe them. I was a little shocked to learn that each rx8 has a CPU specific to that car and they aren't interchangeable. So much for a Racing Beat tune. Every time Mazda flashes it I'd lose the expensive tune and have to ship it to CA.

[Loren]

Looking at the MSM vs. an NA Miata in particular, they're classed in the same SCCA "Street" class....

That statement seems to be the basis for your proposal, but how many other cars have a factory-boosted and naturally-aspirated models in the same Street class?

It's not the basis, it's just the example that I'm most familiar with, and it provides one of the closest comparisons available. You could just as well compare any two cars of similar competitiveness in any given class. One boosted, one not. Miatas are also a hot-button topic because they DO make up most of M3. (as well as S4... many of whom will eventually make the leap to M3) They're certainly not the only consideration, but they're worth considering. But, I really only brought it up because someone specifically asked about the MSM.

As far as "trying to make it work", you've restricted fuel flow, you've restricted charge cooling...the only other thing I can think of is to restrict intake air flow. Mandate the stock throttle body and intake manifold. You'll be able to push more air in, but only so fast, and with no flow improvements.

As mentioned above, I'm of the opinion that throttle body size won't make much difference at the level of boost that we're talking about. However, I'd have no problem at all stating that "throttle body and intake must remain stock" as a part of this boost allowance.

"Wanting a little more power to be competitive in M4?" Methinks you protest too much...you've built a car on par with any other HS-based car under the FAST rules. If you want to keep proving the underdog, stick a turbo in it and see what it makes of M2. Prove it a failure before changing the rules to favor it.

I totally get what you're saying. I don't fully agree, though. I'm nowhere near the potential of M4. I'd need to spend another $3-4k to get there. And that's the point. If I could just bolt on a tiny supercharger, I could get there with $1k.

Another thing we could restrict if we wanted to: Stock flywheel. Getting close to saying "everything from the throttle body to the axles must be stock" at this point, but that's okay... maybe that's the easy way to say it?

[Loren]

Jegs made a really good read here. The Table 1 makes me believe any more than 2-3psi in an engine over 9:1 compression would kill it.

There's probably a lot of truth to that, especially in the world of classic V8's, which is sort of what they're talking about.

NA/NB Miatas tend to take boost better than that because the 1.6 Miata engine was DESIGNED as a turbo engine. It was lifted right out of the 323GTX, turned 90 degrees, and fitted to the Miata with no turbo. When they made the 1.8, they simply stretched the design to allow for a larger cylinder bore.

So, Miatas can reliably take 5-6 psi or more without intercooling on a completely stock engine with 9.5:1 compression. Beyond that, the intake charge gets too hot and you'll start getting detonation and/or overheating the engine. And eventually you'll start melting pistons, breaking ring lands, and all of those wonderful turbo-related failures. But, keep it to 5-6 psi and they'll run forever.

I did some Megasquirt ECU tuning on a 1.6 Miata and got to watch a lot of this stuff happen first-hand. Gobs more power at 8 psi vs 5 psi, but ran HOT, and ran out of fuel at a pretty low RPM. When the owner insisted on that level of boost, I simply lowered his redline to compensate and keep the engine safe. (he had Mustang GT driving habits, he never let the car rev, anyway)

But, that's a Miata. Strong crankshaft and rods, oil squirters on the pistons, etc. Other cars, especially economy cars, probably won't take 5-6 psi as readily. 3-4 might be a safer bet.

[BrilloHeadBen]

Okay, I'm finally at my computer and have some time.

1. I mean this with all due respect, because I don't think you're trying to make a rule just so that you alone can exploit it. It sounds like you want more power out of your car, but can't (which is certainly your situation) or won't ($$$) buy the allowed parts per class rules. I get it, I doubt anyone makes a performance cam, ect for a Mirage, and the other cars in your class DO have those parts available off the shelf. That's a bummer for sure, but that's how it goes when you intentionally pick the furthest thing from a performance car.

2. Keep in mind, that this rule would have to apply to every M class aside from M0. Every class has it's overdogs, and we all know what a well driven open diff boosted Miata on coilovers would do M4. I really like the idea of M4, it's where SLOW cars can genuinely play while having some mods, allowing borderline slow cars to get fast kills the whole idea of the class. Sure, we're talking about it happening in M3/4 specificaly, but this could just as well happen in M1 or M2.

3. I get why you brought up that Joe Vance could build his motor and make about the same amount of power, and your correct, but that would also cost him easily 5x as much as a cheap turbo setup. Cost tends to prevent people from building cars to the extreme of our rulebook. 700 bucks? Yeah ALL of us spend that on shocks without blinking.

4. The whole motor swap rule. I know it might be a tangent, but I don't like it either. I can swap in a motor that fits the class rule bump, but is just a detuned version of an engine that would otherwise cause a bump, flash tune it, and boom, major loophole.

5. Lets take Steve for example, If he runs his SC'ed Miata in M3 with this proposed rule, he has a really great shot at the championship. And that's not because of the car, Steve is a great driver. BUT, it certainly gives the impression (and honestly, it's a bit more than just impression) that to run in M competitively, you need FI.

That's all I've got off the top, I'm sure I have more. But yeah, I really dislike the idea of this rule, and it honestly would make me think twice about going to Mod if I also had to contended with cars that were already in my class, just now with more cheap power.

[BrilloHeadBen]

Aside from my own interest here (I really am going to do the SC at some point. No really. Stop laughing.), there is an inequality in the M classes:
One can swap an engine, and get up to a 25% power increase without having to bump.
One can modify an engine with factory forced induction, for (presumably) less than 25% power increase, and not have to bump.
But if one chooses to add forced induction for said power, one has to bump no matter what, even if it's less than 25%.
That's not fair.

I mostly agree with you. I think the engine swap rule is bad. The rules for factory turbos in Mod actually seem to work fairly well, but I understand where you're coming from, but I think opening an already ajar door is the wrong move.

[Loren]

Believe it or not, you guys are swaying me. I could go either way on it. Who else has thoughts?

I still like the idea simply because I like to allow as much as we can allow. But, if we can't find a reasonable set of restrictions that everyone is happy with to make it work, so be it.

[BigBlue]

I am not a fan of the idea. I was thinking about how to state my opinion as I read thru the thread and by the time I got to Ben's list, I realized my thoughts/concerns paralleled his. Aside from the immediate reaction of fear that Ben and I were thinking alike (I kid, I kid...), I don't see a point in rehashing his list.

Thing is, no matter what the classes are I'll keep showing up. It's great people having a great time at every event. Why mess with a good thing.

[Jamie]

Looking at the MSM vs. an NA Miata in particular, they're classed in the same SCCA "Street" class....

That statement seems to be the basis for your proposal, but how many other cars have a factory-boosted and naturally-aspirated models in the same Street class?

It's not the basis, it's just the example that I'm most familiar with, and it provides one of the closest comparisons available. You could just as well compare any two cars of similar competitiveness in any given class.

OK..it's the one you used, and I still suspect it's a unicorn.

"Wanting a little more power to be competitive in M4?" Methinks you protest too much...you've built a car on par with any other HS-based car under the FAST rules. If you want to keep proving the underdog, stick a turbo in it and see what it makes of M2. Prove it a failure before changing the rules to favor it.

I totally get what you're saying. I don't fully agree, though. I'm nowhere near the potential of M4. I'd need to spend another $3-4k to get there. And that's the point. If I could just bolt on a tiny supercharger, I could get there with $1k.

As Ben pointed out, you created that situation by deliberately choosing a car well down on performance. And as soon as someone shows up with a cheaply blown Miata on coilovers and 205 tires, you're back where you started from...except you've made the class more expensive.

Another thing we could restrict if we wanted to: Stock flywheel. Getting close to saying "everything from the throttle body to the axles must be stock" at this point, but that's okay... maybe that's the easy way to say it?

So you're taking away allowances allowed in the other Mod classes? You're making the rules more complex?! Like Ben, I don't think you're creating a rule only you can exploit -- clearly anyone can take advantage of it -- but it's driven by your unique choice of car.

[BrilloHeadBen]

GET OUT OF MY HEAD, RON!

[Loren]

Another thing we could restrict if we wanted to: Stock flywheel. Getting close to saying "everything from the throttle body to the axles must be stock" at this point, but that's okay... maybe that's the easy way to say it?

So you're taking away allowances allowed in the other Mod classes? You're making the rules more complex?!

To be clear, we're not talking about a particular class here. We're talking about allowing the addition of forced induction in ANY mod class.

I was just suggesting that requiring a stock flywheel on a car that has added boost is another item that we could put on the list of "boosted car" restrictions. It would be one line item on the list. Along with the throttle body and intake restriction that you suggested, and everything that's already there.

Don't blow up about it. I'm just brainstorming potential restrictions that could make a difference.

[Jamie]

I was just suggesting that requiring a stock flywheel on a car that has added boost is another item that we could put on the list of "boosted car" restrictions. It would be one line item on the list. Along with the throttle body and intake restriction that you suggested, and everything that's already there.

OK...then you're taking away an allowance (or multiple allowances) otherwise allowed, because we allow all those changes in Mod otherwise. And people complain the SCCA's rulebook is hard to understand. Not wound up -- I have no dog in this one -- but amused.

[jev61]

I think Loren should get the front runners of M3 together and ask to compete in M3 in his car with boost. If everyone says yes, he is G2G for the upcoming season. If, after the season, they change their minds, he bumps up to M2. Steve, you are out of luck. You will be too much to handle with boost in your car. It is M2 for you. Better yet, go play with Matt and Drew.

[Carracer]

The idea feels like it will only help a very small number of people. Sure I don't think it will destroy any class but at the same time it's not like it's letting more of your "average" street build cars play in a more far class.

1. If it isn't broke don't fix it.
2. I don't think the average turbo build keeps the stock injectors, the only people with that setup would be building a car for FAST classing. I think that is something we want to avoid.
3. "Any change to gear ratios" We can do that in stock class. Why add this for mod classes?

Personally I would think it would make more sense for a simple, motor sway of up 25% HP or 8 PSI of boost. I think that is reasonable for a conservative street setup. Or simpler yet, total HP can't be increased more than 30% without a class bump and work off the honor system.

Like I have said before, M4 ( maybe ), and S5 are the only classes that can't have a car built to FTD. Every other class has enough holes in the rule book to allow for some absolutely unfair cars. Why start adding a more qualifiers that don't really help any of that and again, only work for a car built for the FAST rule book.