Power:Weight in Mod Classes

[Vz28]

1.6 Miatas would suffer, stock or street-prepared, if bunched in with any 1.8 Torsen-y equipped Miatas. As you add power a good diff makes even more of a difference since you have the potential to "exit" each corner sooner as well as faster. It could be the discriminator for pushing one up or down a class. I like the STS class idea.

Power-to-weight filters at the high-hp end can be tricky in this racing environment. While modern chassis and suspension do a lot for using that power over older cars, weight (or lack thereof) can be quite the equalizer. My ESP-ish G8 (some suspension work, stock-width tires, drivetrain stock from the air filter to the exhaust tips) is a little under 10lb/hp and would have finished 2nd, very close to 1st in M2 had I opted to be in the correct class last October, so you could argue that it should be bumped up. Yet I suspect a moderately-prepped M2 car - my Miata if it had a good CSP-ish shock/spring/camber setup - should easily beat it on many courses without adding much power.

I will think about this more later to help keep a good discussion going.

[rab]

Many of our courses have a few tight turns that kill the 1.6. The 1.8 does much better with the courses.

Rick -- what differential do you have on your car? If you're still running the open or viscous diff that originally came with the 1.6s, there's your answer in tight corners.

I am still running the open dif.

I didn't propose a hp to weight ratio I agreed to it.

No, but you proposed a problem that we're trying to either find a way to solve, or determine that it's not enough of a problem to bother with.

Thanks for the input.

There is definitely a problem with the classing of this car... and I truly appreciate the discussion. I just don't have the brain power to put into it yet. But if I am the only 1.6 NA with an issue... well I guess I will just concentrate on getting the participant award. BTW I still like the HP to weight classification. and I also Like Jeremy's M class matching S class.

And whats with the are you having a bad day?

Edit*** I just read Viveks note and it makes good sense.. the STS class seems to be a good way to go.

[Jeremy]

So screw the 1.8 NA guys... Just let them get slaughtered next year by Drew, Charles, and John?

I am still not convinced that the extra 12 hp and torsen diff are so magical that these two cars shouldn't be in the same class.
You guys make it sound like the 1.8 has 300 hp and the 1.6 VLSD doesn't work at all.

2293/128 1994 Miata 17.9
2116/116 1991 miata 18.2

Power to weight is very close from the factory.

It appears that the 1.6 is the car of choice in STS due entirely to it's lower weight.
Why can't the STS 1.8 guys get their car down to 1.6 weights in STS? Should be similar rules to our mod classes.

[Jeremy]

http://www.sccaforums.com/forums/aft/443026

Here are some random people talking about STS cars.
Seems to contradict most of what's been said in here, especially regarding power output and weights.

What's been done to Rick's car? How do we know there aren't a couple more seconds in cheap, easy mods available to him.

[Loren]

And whats with the are you having a bad day?

Just bowing to your wisdom, sir.

It appears that the 1.6 is the car of choice in STS due entirely to it's lower weight.
Why can't the STS 1.8 guys get their car down to 1.6 weights in STS? Should be similar rules to our mod classes.

I'm not familiar enough with STS rules to say for sure, but SCCA rules are always "if it doesn't say you can, you can't", which is way different from the FAST philosophy of "if it doesn't say you can't, it's probably not going to make that much difference anyway... but don't push it". There really isn't much difference between the 1.6 and 1.8 NA chassis. Two weight-related things that STS guys might not do: Remove the 1.8 stock under-car bracing, remove the stock brace behind the seats, switch the dashboard assembly to the lighter earlier dash. They might not do it because it's a pain to do some of it... or it could be in conflict with the rules. Not sure. The 1.8 also never had a VLSD option... and while we all think of the VLSD as junk... apparently it DOES work marginally better than an open diff once you get the oil up to temp. That could be a factor in choosing the 1.6.

My ESP-ish G8 is a little under 10lb/hp

I should have made this clearer from the start. I really didn't intend for this upper end "power-to-weight filter" to apply to cars AS CLASSED in SP. That is to say, I think the "natural" SP classing takes into account the power that any given car is capable of making. The cars we need to worry about in FAST are the ones that are modded outside of the realm of SP. The cars with monster engine swaps and/or added forced induction. And it's more the cars that come up from M3 that are (or could be) of more concern. The 240 is a good example. M3 car. Engine swap or turbo bumps it to M2. But, what if that engine swap is a built LS6? Is 400 hp in a 2500 pound car appropriate for M2? THAT is the kind of thing I'm targeting with the power:weight filter idea.

For M2 cars, the question would apply more to something like your G8 with added FI. By the current rules, it would bump to M1. But, would something with as much power as a boosted LS is capable of making be appropriate for M1? Especially with unlimited suspension and unlimited wheel/tire width? A cap on M1 power levels might bump that car to M0 so that it couldn't be an overdog against all of the stock-engined S2000's, Corvettes, etc.

And, again, the numbers I chose were just guesses and could be wrong! If 10:1 isn't right, maybe it's 9:1? But, some kind of limit seems like a good idea just for "Frankenstein control".

On the bottom end, I think it should apply to any car, even as-classed. (back to the SCCA "best of breed" expectation) If it obviously doesn't meet the minimum power:weight to be competitive in the class (a bar that we'll set VERY low), then the driver will have the option to "fall out" to the next lower class.

[Loren]

http://www.sccaforums.com/forums/aft/443026

Here are some random people talking about STS cars.
Seems to contradict most of what's been said in here, especially regarding power output and weights.

Jeremy, that starts off with this "You want the 90-93 for STS. Lighter, better gearing, more power (after ECU upgrades)." and goes from there.

It's not that the info is contradictory, it's just that they're working from a completely different ruleset.

Better gearing? We have NO restriction on gearing. You want a 4.3 (the 1.6 gearing) in your 1.8 Miata? (or any other NA/NB Miata) No problem, there is a factory 4.3 Torsen that bolts right in. Our rules DO NOT prohibit it.

And it's not any lighter under our rules.

And there's no way that an equally prepared 1.6 will make more power than a 1.8. Not possible.

You have to apply what is being said to OUR ruleset, not theirs.

(unless you're talking about simply moving the STS-legal cars to M3... THEN you can look at their ruleset... but I've already conceded to that as a Good Idea if we choose to do it)

[Jeremy]

OK. So a 9.4:1 1.6L engine can never have as much power as a 8.8:1 1.8L engine.
STS guys say the 1.6 is 100 lbs lighter. But under FAST rules you can remove some random stuff that no one would ever do, to equal it out.
a torsen diff is arguably better than a vlsd which is marginally better than an open diff.
1.8 guys can change their gearing to 1.6 specs. How many FAST members are changing gears?

I think you have kind of a distorted view of the average autocrosser. I don't think anyone is changing gears, removing braces, changing dashboards, drilling holes in pieces to save weight, and various other things which you are worried about.

The mod cars are about putting on springs, bars, intake, exhaust and driving, and if that's the case the 1.6 and 1.8 are not that far apart. I would think there are other mismatches in other classes which are 100 times worse than the competing NA miatas.

[twistedwankel]

I know a member who is "actually" putting a well thought out NA LS1 into a '94 Miata and is only planning on gaining 200lbs over stock engine....holy karumba...I love that car all ready.

[Vz28]

For M2 cars, the question would apply more to something like your G8 with added FI. By the current rules, it would bump to M1. But, would something with as much power as a boosted LS is capable of making be appropriate for M1?

Perhaps we should find out

Anyway...I agree with what you that power/weight filtering can be useful for re-classing. I was just making the point that it may be necessary to look at the chassis the power is being added to, in order to see if it can effectively use all (or any) of it in an autocross environment. In the case of the G8, I suspect that it would not dominate M1. It is very heavy and cannot fit very wide tires given the weight, and even very wide true street tires would not make it easy to use the power.

Regarding 1.6 vs 1.8 NAs, I cannot really comment there as I have not driven both. I have driven a VLSD car and it certainly does work better than an open diff when the important parts are still on the inside. But in a similar torsen car it seems to me that you can put the power down much earlier and in a more consistent fashion which is valuable in and out of every corner. I think STS Miatas are not allowed to run Torsens but I may be wrong.

Regarding "average" versus "serious" autocrossers, my inclination (which may or may not align with this group's goals) is to attract new drivers and keep them coming back. Does that mean catering a little to the most common cars that attend regularly? Not sure...stir stir stir...

[Loren]

How many FAST members are changing gears?

On Miatas? More than you think. As I mentioned earlier, the 1.6 diffs are made of glass. Even on cars that aren't autocrossed or otherwise abused, they break. It's not a question of "if", but "when"... they all break. And any Miata enthusiast who doesn't live in a vacuum knows that the 1.8 diffs are an easy bolt-in... and they DON'T break. It's a no-brainer. And 4.1 Torsens are fairly cheap, too. (if you're looking at buying a replacement diff, anyway... $200 for another 1.6 diff that's going to break vs. $500 for a Torsen that's not...)

I think you have kind of a distorted view of the average autocrosser. I don't think anyone is changing gears, removing braces, changing dashboards, drilling holes in pieces to save weight, and various other things which you are worried about.

Drilling and cutting stuff is not the norm. But swapping parts? I don't know about other enthusiast communities, but I know it's VERY common in the Miata community. Diffs? See above. 3.9, 4.1 or 4.3, take your pick. (turbo guys like the 3.9, racers like the 4.3, 4.1's are more common) Removing braces? Only hardcore lightness types do that... everyone else likes to ADD braces (but they'll add all the stock braces from the 1.8 to the 1.6... and then all the same aftermarket braces). Swapping dashes? It's more often done for aesthetic reasons rather than performance/weight reasons, but dash swaps are COMMON on Miatas... and any 90-05 Miata dash can fit in any other Miata (door panels may need to be swapped to match).

The mod cars are about putting on springs, bars, intake, exhaust and driving, and if that's the case the 1.6 and 1.8 are not that far apart. I would think there are other mismatches in other classes which are 100 times worse than the competing NA miatas.

This is possibly so. I'd very much like to find a simple way to address a lot of them, as well... that's the point of the minimum power:weight downclassing idea.

[Loren]

Anyway...I agree with what you that power/weight filtering can be useful for re-classing. I was just making the point that it may be necessary to look at the chassis the power is being added to, in order to see if it can effectively use all (or any) of it in an autocross environment.

Problem with that is that it is very much a "judgement call" at that point. A simple formula (even with guestimated numbers that Jamie doesn't like) is a lot easier than having to judge the "relative goodness" of a particular chassis. I like classing rules that are easier to apply than that. It's fairly easy to spend a few minutes searching Google to get a reasonable idea of the power and weight of a given car/powerplant combination. Not as easy to come up with a "how good is this chassis for autocross" quotient. And with unlimited prep rules... nothing keeping you from "fixing" any suspension shortcomings... nothing keeping you from putting fender flares on to run wider tires. I mean, if you've already spent $5-10k to put forced induction on the engine... why wouldn't you?