STL engine builds?

lateapex911 said:
Chip, I understand all that... I'm trying to get to a base answer, and then from THERE we can debates the little stuff.
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I know you know - hell everyone still reading this thread (all 6 of us) knows. we also all know that there's no answer that is always right. because specifics matter, and the rule is blind to them. I'd take the RWD car so long as it was no more than 10% heavier, that's 235 lbs, just because I think it'd be a better car over the race, even if it din't qualify as well or even win in your hypothetical race.

the IT rules seem to work, and I'll say it again - I think it's because everything is so imperfect that it all works out in the wash. engine swaps and stiffer chassis start to correct for that so ST is less forgiving to hatpulls.
 
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JeffYoung said:
Not far off of Ron's example really. 200 crank is around 170ish wheel, if not a little low. The Glen seems to be a lot of long straights and fast sweepers.

Work of his example and explain why he is wrong.
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In STL trim that will be a lap in the 2:12-2:14 range at the Glen.
 
lateapex911 said:
OK, for the Golf, you're talking 120hp or so crank? And since you said "yes" how much weight would you add to the RWD car before you said, "hmmm, yea, that's a tough one to choose between, I just don't know which way I'd go"?

And at ITS power levels, "Hell yes" becomes ? weight? (we are at 2350 for the FWD car)
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At the ITB level, 150-200 pounds would shift my thinking - again, ALL other things being equal.

At some point with an S-power car, the amount of weight required to make it work becomes so much that it's not likely to happen. I think I'd be hard pressed to do an FWD S car REGARDLESS, but I confess it's not all about where the driven wheels are.

K
 
Greg Amy said:
Nope. The CRB has declared directly to the STAC (we asked) that rotaries are subject to a 2x displacement multiplier when considered for power-to-displacement calcs (though I can't find it in the GCR anywhere...) As such, none are automatically eligible for STL. To address that, we specifically include the 12A and 13B as part of the STL program, with limited mods and additional weight.

GA
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GCR overrides all those conversations. I just re-read the rules and nothing says rotaries are not allowed. It fits all criteria that I could find. It is an IT car and it has under 2.0 displacement as well. The only thing I found was a specific weight for the 12A and 13B. So ALL other rotaries would follow the regular weight classifications as far as I can tell. What am I missing?

The only information I found on pertaining to a Rotary engine... From the GCR:
The Mazda 12A is permitted at 2225 lbs; Mazda 13B is permitted
at 2615 lbs; no porting is permitted in either engine the 5th and 6th
intake port actuators and valves may be removed or disabled.

If that is to exclude other Rotary engines it should add a line to the start of the above rules "Only the following non piston engines are allowed"

Stephen

I guess it doesn't matter, my ITB car is a 2.2 and the RX8 won't be allowed for my brother to double up in it. I guess this class is not something I personally should be following anymore. ITE looks like the best fit. I just wanted to follow-up on why I thought I was correct.
 
StephenB said:
What am I missing?
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Nothing in the current document, but like Greg said before, these engines have been considered in the past to be 2X of their displacement because of how many 'power strokes' they can produce in one single engine revolution vs the traditional internal combustion engine.
 
Andy Bettencourt said:
Nothing in the current document, but like Greg said before, these engines have been considered in the past to be 2X of their displacement because of how many 'power strokes' they can produce in one single engine revolution vs the traditional internal combustion engine.
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So the type of engine is adjusted differently based on the number of "power strokes".

OK that makes sense.

Why is the exact same reasoning not applied to AWD cars, which have twice as many drive wheels? (I see this as an STU issue)
 
JS154 said:
So the type of engine is adjusted differently based on the number of "power strokes".

OK that makes sense.

Why is the exact same reasoning not applied to AWD cars, which have twice as many drive wheels? (I see this as an STU issue)
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Let me be clear, they typically list the 1.3 Wankel like a 2.6 in classes like this because of it's design and 'how it acts'. We all know it's effectively a 2-stroke. Classes that take those factors into account usually allow porting however, so in this case you get the whammy without the allowance. AWD and forced induction are animals that are very hard to tame as you know.
 
Someone that knows these engine want to 'splain to me WTF this means and how the math works out...?

GCR Technical Glossary:
Displacement (Engine) – Reciprocating engine: the swept volume of 1 cylinder times the number of cylinders. Rotary engine: the difference between the largest and smallest volumes of the working chamber, times the number of lobes, times the number of rotors.

Sports Racer Category Specs:
Rotary Piston Engines:
Cars with rotary piston engines by the NSU-Wankel patents shall be classified on the basis of a piston displacement equivalent of twice the volume determined by the difference between the maximum and minimum capacity of the working chamber.

And then there's this:

http://www.rx7.com/techarticles_displacement.html

...which explains the 2x multiplier pretty well.

But the "controlling legal authority" on rotaries right now is the GCR definition, which by my calc brings the engine to just over 3.9L...?

Andy Bettencourt said:
Let me be clear, they typically list the 1.3 Wankel like a 2.6 in classes like this because of it's design and 'how it acts'. We all know it's effectively a 2-stroke. Classes that take those factors into account usually allow porting however, so in this case you get the whammy without the allowance.
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Which is exactly why I believe that all rotaries are STU engines, with "street port". You get both the whammy and the allowance.

GA
 
Greg Amy said:
Someone that knows these engine want to 'splain to me WTF this means and how the math works out...?

Rotary engine: the difference between the largest and smallest volumes of the working chamber, times the number of lobes, times the number of rotors.
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It's a way to calculate the displacement of a chamber (rotor housing) factoring in the amount of sides used to create a power stroke on a single rotor then again the amount of those chambers.

Since the 13B has two rotors with volumes of 654cc's each, it's common to measure the overall volume at 1.3L (1308cc's)...
 
Andy Bettencourt said:
Since the 13B has two rotors with volumes of 654cc's each, it's common to measure the overall volume at 1.3L (1308cc's)...
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Andy, that 654cc is swept volume per lobe, per rotor. Ergo, using the GCR definition it's 654cc times three lobes per rotor times two rotors...or 3.9L.

Using the SRCS, it's 2.6L.
 
Greg Amy said:
Andy, that 654cc is swept volume per lobe, per rotor. Ergo, using the GCR definition it's 654cc times three lobes per rotor times two rotors...or 3.9L.

Using the SRCS, it's 2.6L.
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100% true, but aren't we trying to compare a measurement vs a standard 4-cycle 4cyl? Then, as the link you posted points out, you should only use 720 degrees of rotation, hence the 2.6.
 
I agree with the 2.6L, that link explained it pretty well. I suggest that the GCR Technical Glossary definition needs to be replaced with the one in the SRCS. I'll actually make that request to the CRB now.

So, Stephen, there you are, that's what we were all missing.

On a related and absolutely, 100% coincidental side note, I heard second-hand that the STL RX8 entry at the Sebring Double National was asked to change his class to STU this afternoon.

GA
 
Greg Amy said:
On a related and absolutely, 100% coincidental side note, I heard second-hand that the STL RX8 entry at the Sebring Double National was asked to change his class to STU this afternoon.

GA
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Funny. Keene must have been looking over the list and went to talk to the guy. Gots to clean up the rules boys!!!
 
I figured I might add my recent exp. to this because its relevant to a lot of the conversations we had especially about SCCA/NASA and how welcomed you feel.

I finished the Buccaneer Region DD School at Roebling and had a blast with everyone involved from SCCA. They went out of their way to make us feel like we were customers and wanted which was nice. Adam Malley was really great as well as the other SCCA folks I dealt with.

I did very well with my STL car granted I have more power than a lot of the vehicles out there outside of an EP rx7 in my group.

1:24.8 was my best time per my traqmate, and a 1:25.1 from mylaps so close enough.

I have a lot of areas to improve on still but the Miatas that were out there in various trims were all over me and just barely off my times. I think a SM converted to STL would actually be a very, very strong competitor and it makes me think I should have gone that route.

Or maybe Im just that slow!
 
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