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Andy - this is a helpful article. I'm curious about the shock compression issue; I've heard that compression can be reduced when spring rates go up, at least as far as comfort goes. Is the compression of your Koni race shocks (on soft setting) lower than an OTS Koni Sport? Does it make sense, for a dual-purpose car, to reduce the compression damping of a Koni Sport for mid to higher level spring rates ("free" mod anyway if you're revalving the rebound side)?

Thanks

Chris

P40vic:

Andy - this is a helpful article. I'm curious about the shock compression issue; I've heard that compression can be reduced when spring rates go up, at least as far as comfort goes. Is the compression of your Koni race shocks (on soft setting) lower than an OTS Koni Sport? Does it make sense, for a dual-purpose car, to reduce the compression damping of a Koni Sport for mid to higher level spring rates ("free" mod anyway if you're revalving the rebound side)?

Thanks

Chris

I now have my low-speed compression adjusted all the way to soft with the STS2 setup.  Helps a lot with the front brake lockup issue and makes the car bite better on bumpy surfaces (low amplitude, hi frequency bumps) like Wendover and Denver.  I used to run it all the way up in Stock category on stock springs.  My compression on low is very similar to an OTS Koni yellow.  When I get a chance I'm going to scan and post my dynos in a future article. 

--Andy 

I have a local fvriend in HOuston who we're tinkering with his car for STS2 as well. Built on a budget is the theme. I think all it needs now is an alignment and tires and then some more testing :) David

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David Hedderick
Pearland (Houston), TX
01 CRG YZ125 (FOR SALE! $2500)
08 Mazda 3s
02 Mazda Protege (automatic tow vehicle)
92 Miata SE - Fun half-arsed STS2 Car

davebs14:

I have a local fvriend in HOuston who we're tinkering with his car for STS2 as well. Built on a budget is the theme. I think all it needs now is an alignment and tires and then some more testing :) David

I can't wait to hear the "budget exhaust" you have designed for him.  

Oh wait, wrong thread...

--Andy 

It will be light I can assure you :)

But may be a LEEEETLE loud ;)

David

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David Hedderick
Pearland (Houston), TX
01 CRG YZ125 (FOR SALE! $2500)
08 Mazda 3s
02 Mazda Protege (automatic tow vehicle)
92 Miata SE - Fun half-arsed STS2 Car

davebs14:

It will be light I can assure you :)

But may be a LEEEETLE loud ;)

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Aut tace aut loquere meliora silentio.

Andy, how's it sound with just the Supertrapp after the cat?  Have you run any events with sound meters?  What readings were you getting?  One of the Atlanta region's main sites is limited to 98db, so anything close to that range is basically out.

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Andrew
STS2 114 - 1992 Miata

amaff:

Andy, how's it sound with just the Supertrapp after the cat?  Have you run any events with sound meters?  What readings were you getting?  One of the Atlanta region's main sites is limited to 98db, so anything close to that range is basically out.

 

That's the good thing about a SuperTrapp, it's tunable. I can take discs out and quiet it down enough to run at Gwinett, or add discs (or even remove the cap completely) and open it up at sites that don't have any sound restrictions. If you've heard Heyward's Civic it's got the same setup, cat to straight pipe to SuperTrapp dumping under the car.

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Scott Sawyer
Team Underdog Racing
89 Honda CRX Si, STS2 123

STS_Underdog:

amaff:

Andy, how's it sound with just the Supertrapp after the cat?  Have you run any events with sound meters?  What readings were you getting?  One of the Atlanta region's main sites is limited to 98db, so anything close to that range is basically out.

 

That's the good thing about a SuperTrapp, it's tunable. I can take discs out and quiet it down enough to run at Gwinett, or add discs (or even remove the cap completely) and open it up at sites that don't have any sound restrictions. If you've heard Heyward's Civic it's got the same setup, cat to straight pipe to SuperTrapp dumping under the car.

What he said. 

Last time I was at Gwinnet I was in the Civic with the same muffler.  I believe I ran nine discs and passed sound control just fine, though the readings changed quite a bit as the weather changed. 

The Miata is a LOT quieter even with the exact same muffler.  I can run more discs and hit the same readings.  I believe this is due to the longer tubes in the header and the fact that the cat is much farther downstream (under the driver's seat).  Of course, it could also be that that the Miata cat is more restrictive than the Civic cat. 

 HTH,

--Andy

 

That helps a lot, but my only other question is how does it sound?  This will be an occasional fair weather driver, so I'm trying to avoid the bees trapped in a coffee can sound.  Also, how easy is it to tune?  Can disks be "hot" swapped (literally, while the thing's hot).  I'm curious if you could add / remove disks between runs depending on condition changes.

 Also, any more pics of how it's mounted? Did you weld a flange to it so it would bolt up to the cat?  I can't tell by looking at the picutre on your GRM blog.
 

 Thanks again :)
 

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Andrew
STS2 114 - 1992 Miata

amaff:

That helps a lot, but my only other question is how does it sound?  This will be an occasional fair weather driver, so I'm trying to avoid the bees trapped in a coffee can sound.  Also, how easy is it to tune?  Can disks be "hot" swapped (literally, while the thing's hot).  I'm curious if you could add / remove disks between runs depending on condition changes.

 Also, any more pics of how it's mounted? Did you weld a flange to it so it would bolt up to the cat?  I can't tell by looking at the picutre on your GRM blog.
 

 Thanks again :)
 

It sounds very mellow, especially when it has disks in it.  With six discs, I can run through a National Park without drawing any attention.  It does not at all sound abrasive or raspy, even when fully uncorked.  Its quite easy to tune, and yes you can do it hot.  There are six allen-head screws that hold the plates in (I only keep three in there to make it easier to change).  A socket wrench with the appropriate socket makes the job quicker than an allen wrench.

The downside of my setup is that it the sound exit is right under the driver's seat and it can drone on the highway.  If your's is a daily driver, I'd recommend mounting the thing at the back of the car exiting straight out the back.  Have a look at a Spec Miata exhaust for tube routing (Mazdaspeed or Springfield Dyno).  You'll need to get pipes bent for that, though.

If you choose to duplicate mine, you have to fab up an adapter that has a flange and a small piece of pipe that is joined at an angle.  The cat exit points at the powerplant frame, so you need a slight angle so the muffler can parallel the PPF.  I have better pics of the pieces used, if you choose to go that route.  Lemme know and I can get them to you.

--Andy 

It's not going to be my daily, so I'm seriously considering this for the weight and performance advantage (as well as the tuneable volume for sites like Gwinnett).  If you wouldn't mind sending some more pictures to amaff5 @ gmail dot com

 

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Andrew
STS2 114 - 1992 Miata

amaff:

It's not going to be my daily, so I'm seriously considering this for the weight and performance advantage (as well as the tuneable volume for sites like Gwinnett).  If you wouldn't mind sending some more pictures to amaff5 @ gmail dot com

 

You've got mail.

 I've also updated the blog to include a pic of the finished adaptor piece. 

Some of the pics on the blog are chopped off to the right side in the formatting.  You can get the whole picture by saving it to your own machine. and viewing there.

--Andy
 

Thanks for the info.  That'll be extremely helpful :)

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Andrew
STS2 114 - 1992 Miata

New update.  Tested a staggered 15" RT215 and 16" RT615 setup.  Story here:

Test

--Andy

 

And another.  Lost a little weight over the holidays...

Weight loss 

--Andy 

So, what does this thing weigh now?

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90 Miata/89 CRX - STS2 #90/190

GChambers:

So, what does this thing weigh now?

My scales are broken and in for warranty service, so I can't answer that right now.  But it should be pretty much where I predicted it would be when I started.  Somewhere in the 1950-1960 range.  Of course, that's today.  In a week, it will add another 20 lbs due to the new seat rule.  I'm still contemplating how I want to make the new brackets.  I can do a lot with 5 lbs of steel...

--Andy 

Andy Hollis:

And another.  Lost a little weight over the holidays...

Weight loss 

--Andy 

 Damn, you got me beat by 2+ pounds! My 9BS is getting pretty weak anyway, guess it'll be time to replace it in the spring.

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Scott Sawyer
Team Underdog Racing
89 Honda CRX Si, STS2 123

That's impressive.

Looks like I have a ton of weight to shed. We were hopeful that we could get my car down to 2015 from 2058lbs (On the HPT scales at Nationals) with going from the "B" package to a base package. I guess the new goal should be under 2000lbs. My current seats should be close to 25lbs. I will need to weigh them to confirm before the season gets going.  

 

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90 Miata/89 CRX - STS2 #90/190