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ChrisSwearingen:

Okay, having been called out for making Andy H's ears bleed in Ft Worth, and also battling sound at a local event even with the muffler on ( more power = more sound, go figure) I am doing something about the exhaust.

From the header back, it currently has a high flow 2.25" cat about 18" of 2.25 stainless to a 12" resonator, more 2.25" stainless to a Racing Beat muffler to a resonated tip.  And thats still too loud, but just barely.  The whole sound discussion thread aside, I have no problem being quiet where we need to, its just one more of the challenges we have to face, on the other hand, if I can pick up some gains at non sound controlled sites I will.

The current "plan" subject to your feedback and what the exhaust shop tells me is 3" resonator 18" long to 3" stainless to a shortie dual chamber muffler of some sort, more 3" back over the axle to a flange.  From there it's either a turndown and ear plugs for Andy, or a BIG muffler of some kind to a turndown that is still under the rear of the car.

Any suggestions as to brands and or configuration?  Will it a) be quiet and b) make power?

Any suggestions will be greatly appreciated.
 

Thanks for making the effort, Chris!

Best full exhaust I've seen for a Miata is the one George Doganis has on his CSP Miata.  It was built by Burns and utilizes thin-guage mandrel-bent stainless piping with one (or maybe two?) of their super-light racing mufflers.  Makes full power and has great sound.  Even passes sound at San Diego.

--Andy 

MNbiker:

Chris,

 What's with all the exhaust pieces?  With what you described, I bet your exhaust is AT LEAST 15-20 lbs heavier than mine - which consists of a header & pipe to the diff, with an 18" resonator welded in the middle of the pipe.  I have a turn-down at the end.  That's it.  I do have a flowmaster I can hange across the back under the trunk, for a site with tight noise restrictions - but I've never had to use it for an event.  Guess I'm lucky we don't have sound-restricted sites. 

 -Steve

 p.s.  Your car seems a bit porky for an NA Miata.  My '99 was right at 2,200 the last year I ran SM2, and that was with A/C, an A/W intercooler, and the larger 1.8L brakes.  An NA should be lighter.  

We modeled our local sound restrictions after San Diego 

Local Sound Policy:

Standard:

• Maximum limit of 93db, A weighted, at the measuring point.

Measurement:

• The measuring point(s) will be established during course set up, and approved by the event chair.  The course map shall be provided to the chief of sound two days before the event.
• When possible, measurements will be taken at all event sites to provide information for competitors.
• Measurement will be taken at a point on course where the car can be reasonably expected to be at full throttle, under load and at high RPM.
• The measuring point will be 50 ft from the edge of the course lane using a coned gate as a reference.  More than one measuring point may be established.

 

At our last local event I was at 92.6  with the exhaust I had.  A turn down brought it down to 91.  Legal but still too close for me to be really comfortable.  I "needed" a 3" exhaust anyway, so I figured two birds and one stone were in order.  From the racing beat header, I now have 3" mandrel bend for about 4 inches to a 24" long 3" core resonator.  I have a flange after it that I can put a turndown on that will dump right by the diff.  Or I have 3" crush bent (way to many angles to get the 3" through to use mandrel) to the largest body 3" Magnaflow the shop had.  Is about 24" long, 4" thick and 6 or 8" wide.  Side inlet, center outlet, to a 3" crush bent 90 to get out the back of the car to a 3" crush bent turn down with a ridge welded on the tip in case I have to stuff it with steel wool and clamp hardware cloth around it.  I have no idea why my car is so loud, it may be the "frequency" more than anything else or the pressure from the supercharger, heck it may even be intake noise.   Anyway, I tried several different 3" mufflers on the back, and the Magnaflow was quieter than anything else, and should flow better.

I agree an NA should be lighter, but minimum weight for a 1839cc forced induction rwd car in SM2 is 2247.8
 

Andy Hollis:

Thanks for making the effort, Chris!

Best full exhaust I've seen for a Miata is the one George Doganis has on his CSP Miata.  It was built by Burns and utilizes thin-guage mandrel-bent stainless piping with one (or maybe two?) of their super-light racing mufflers.  Makes full power and has great sound.  Even passes sound at San Diego.

--Andy 

You are welcome Andy.  I really don't have a problem with sound restrictions.  Where they exist I will meet them.  But I will also put a set of ear plugs in the glove box for you 

Assuming that I need to drop 200 lbs from the car for next year based on the March Fastrack proposal (I bumped that thread to see where things are), a logical place to save weight is the clutch and flywheel.  I think I can shed 10 or 15 pounds of rotating weight pretty easily.  The questions are:

1) 4.5" or 5.5"

2) two disk or three

I think most of the CSP guys are using a 5.5", any reason not to use the 4.5"?  Any tried and true solutions out there people care to share?

ChrisSwearingen:

Assuming that I need to drop 200 lbs from the car for next year based on the March Fastrack proposal (I bumped that thread to see where things are), a logical place to save weight is the clutch and flywheel.  I think I can shed 10 or 15 pounds of rotating weight pretty easily.  The questions are:

1) 4.5" or 5.5"

2) two disk or three

I think most of the CSP guys are using a 5.5", any reason not to use the 4.5"?  Any tried and true solutions out there people car to share?

Not tried and true as the car hasn't run yet, but a few months ago I purchased a 5.5 Tilton twin disc rally clutch for my DP car. Everything bolted together just fine. The flywheel and throwout bearing came from Mazdaspeed, the clutch cover, spring, discs, clutch stop and ARP flywheel bolts came from CV Products, the AN clutch to flywheel bolts and nuts came from Aircraft Spruce. Total bill was right at $1000 including a decent discount on the Tilton parts from CV.

The flywheel weighed 6 pounds 12 oz. Total weight of the flywheel and crank bolts, clutch, plates, and clutch bolts came to 13 pounds and 15.2 oz. 

The argument for the 5.5 over the 4.5 is based on the weight of the car and the skill of the driver. The 4.5 engages harder and is made for lighter cars. The 5.5 is slightly more forgiving and is made for heavier cars, like production cars. The 7.5 is slightly cushier and is made for even heavier cars with V8 engines. I've described the 5.5 and 7.5 as "more forgiving" and "cushier". They are not forgiving and cushy, except in relation to the other clutches.

I went with the Tilton over the 10,000rpm because all the parts were off the shelf - nothing was custom made. I purchased the thicker, heavier rally clutch so it would be slightly more forgiving to slipping the clutch on engagement and is slightly more tolerant to disc wear. I'm hoping it will last a full season of 30 event days with two drivers.

ChrisSwearingen:

Assuming that I need to drop 200 lbs from the car for next year based on the March Fastrack proposal (I bumped that thread to see where things are), a logical place to save weight is the clutch and flywheel.  I think I can shed 10 or 15 pounds of rotating weight pretty easily.  The questions are:

1) 4.5" or 5.5"

2) two disk or three

I think most of the CSP guys are using a 5.5", any reason not to use the 4.5"?  Any tried and true solutions out there people car to share?

Chris,

IMHO this is a place where you shouldn't emulate the CSP (or DP) cars.  Supercharged vehicles - especially small displacement 4-bangers - are prone to idle droop if you reduce the rotating mass too far.  I was all set to go with a small diameter clutch, until I researched the issue a bit more thoroughly.  Personally, I wouldn't go any lighter than a stock diameter 1.6L clutch/flywheel combo.  I'm currently running a stock flywheel, which will be replaced next year with an ACT chromoly flywheel & another Xtreme clutch - half the price of a 5.5" setup, and will last 3 times longer without a re-build.

ChrisSwearingen:

Assuming that I need to drop 200 lbs from the car for next year based on the March Fastrack proposal ...
 

I assume you saw that Flyin' Miata will be selling Shandelle's front tubular subframe. It's reported to weigh about 10 lbs less than stock. But I can't remember if the Mustang guys got the replacement K-Members allowance into SM or not...

http://forum.miata.net/vb/showthread.php?t=282770

http://forum.miata.net/vb/showthread.php?t=286530

http://forum.miata.net/vb/showthread.php?t=286372 

modernbeat:

 I assume you saw that Flyin' Miata will be selling Shandelle's front tubular subframe. It's reported to weigh about 10 lbs less than stock. But I can't remember if the Mustang guys got the replacement K-Members allowance into SM or not...

That's not gonna fly in SM.  Kinda tempting for XP though (assuming he could relocate the mounting points for me.) 

MNbiker:

I'm currently running a stock flywheel, which will be replaced next year with an ACT chromoly flywheel & another Xtreme clutch - half the price of a 5.5" setup, and will last 3 times longer without a re-build.

One reason I went with the Tilton over an Xtreme was that by the time I put the best and lightest Xtreme/ACT etc. parts together my bill would have been around $780. True, the longevity was expected to be better and more compatible with the stock throwout parts, but the weight was higher. At a $250 delta the Tilton made sense for a high strung DP Miata. FWIW, the super-special small diameter, curved face throwout bearing was $124 of the $1000 total.

modernbeat:

One reason I went with the Tilton over an Xtreme was that by the time I put the best and lightest Xtreme/ACT etc. parts together my bill would have been around $780. True, the longevity was expected to be better and more compatible with the stock throwout parts, but the weight was higher. At a $250 delta the Tilton made sense for a high strung DP Miata. FWIW, the super-special small diameter, curved face throwout bearing was $124 of the $1000 total.

I'm totally with you on using a small-diameter clutch for a DP (or CSP) car.  It was on my build list, if I'd moved my car to DP. 

I have the 5.5" Quartermaster clutch and aluminum flywheel.  The clutch and flywheel weigh 12lbs 3 oz plus bolts.  I went with the racing disks rather than the rally.  I took off about 7# from the stock crankshaft and the car will definitely rev  But with no mass, its been difficult for me to launch cleanly.  My wife has mastered it better than I have!

QM makes a thin rally disk that will replace the racing disks, so if modernbeat likes his set up, I may try the rally disks.

Check out the Prather's website http://www.pratherracing.com/products/powertrain.shtml  and http://www.powertraintech.com.

There is some good reading about clutches on the Powertrain web site. 

MNbiker:

ChrisSwearingen:

Assuming that I need to drop 200 lbs from the car for next year based on the March Fastrack proposal (I bumped that thread to see where things are), a logical place to save weight is the clutch and flywheel.  I think I can shed 10 or 15 pounds of rotating weight pretty easily.  The questions are:

1) 4.5" or 5.5"

2) two disk or three

I think most of the CSP guys are using a 5.5", any reason not to use the 4.5"?  Any tried and true solutions out there people car to share?

Chris,

IMHO this is a place where you shouldn't emulate the CSP (or DP) cars.  Supercharged vehicles - especially small displacement 4-bangers - are prone to idle droop if you reduce the rotating mass too far.  I was all set to go with a small diameter clutch, until I researched the issue a bit more thoroughly.  Personally, I wouldn't go any lighter than a stock diameter 1.6L clutch/flywheel combo.  I'm currently running a stock flywheel, which will be replaced next year with an ACT chromoly flywheel & another Xtreme clutch - half the price of a 5.5" setup, and will last 3 times longer without a re-build.

I'd agree with this. In a class like CSP or DP where these clutches meaningfully help acceleration, they might be worth it. In SM it just seems like the lack of driveability will outweigh the weight savings. You're talking 100whp more than CSP. You can probably nearly spin the tires at will, and that weight is low and at least close to the middle of the car. After codriving with Beth and Erik at nationals, it really convinced me that a fast SM car can still drive like a stock car. Get in, buckle up, turn the key, and gently roll away... then go like hell when you push the pedal down. My MR2 is now the same way, a clutchmasters stage 3 feels about like stock, and holds my 300 ft-lbs and 340whp going to my 315 rear tires. I think a small clutch would do little for me other than be a distraction and make the car harder to drive. There's already enough to think about out there.

Good advice that doesn't involve spending money!  Are you sure this is the SM(2) forum?

Now where will that 15 lbs come from? 
 

ChrisSwearingen:

Good advice that doesn't involve spending money!  Are you sure this is the SM(2) forum?

Now where will that 15 lbs come from? 
 

 We can still get 10-12lbs with reasonable driveability. I was planning on the ACT Steel Flywheel for a 1.6...9lbs I believe. Follow that up with a lightened SPEC clutch and you can lose another few lbs there. We don't have a lot of places to lose weight so we need to get it where can. Especially when Randy is rolling around on 315s....a miata will never get the power down or brake like that MR2.

We took the car to the MiDiv event in Topeka.  The new pulley combination netted us about 14.6 PSI and unfortunately 4 bent rods.  We are cutting it close to get the motor back together for Nationals.  The engine management change from eManage Ultimate to a standalone Megasquirt-II will most likely not be completed.

The recent additions have earned the car the name of "Bionic Miata" the hope is that it will be better than it was before, better, stronger, FASTER.  Let's just hope it doesn't end up costing six million dollars.

New parts list: (just for reference Bill and the guys at Flyin Miata had all the goodies in stock and I got them in 2 days from picking up the phone which really helped with the schedule, other vendors were quoting 10+ days)

Wiesco 9.0:1 forged pistons +1mm overbore (new displacement 1884cc, new min weight 2256.8, time to put more junk in the trunk)

Carrillo H-Beam rods

 Custom rod and crank bearings

+1mm Intake and exhaust valves

ARP main cap studs

New valve springs and retainers

ATI dampener

145mm crank pulley for the blower

and all the usual wear items, oil pump water pump etc.

So while I am waiting on the motor to come back from the engine builder, I am tinkering with other things.  New silicon couplers for the intercooler pipes, tbolt clamps, intake air temp sensor mounted to intercooler outlet.  Various engine bay cleanup things.

Which brings me to the dual feed fuel rail quesiton.  Not that I really need more to do, but this is a good time.  Anyone have an opion, worth doing?  Should I just convert mine to dual feed, or buy an aftermarket one?  Good marketing but bad science?

Obligatory picture of bent rods:

Chris,

Sorry to hear about the engine troubles.  We put a rod through the side of my block at the Milwaukee Tour warmup event - so I can definitely empathize.  I'm pretty surprised you managed to bend rods at only 14.6 psi.  That leads me to suspect a less than optimum tune.  My last engine lasted 5 seasons with a stock bottom end at 15.5 psi.  I put another stock bottom end back in the car, as I can buy several $1K stock engines for the price of a single built engine.

FWIW I don't see the need for a dual-feed fuel rail until you get to 300whp.  I'm still running the stock rail, with no issues at ~280whp.  All those anodized aluminum parts & braided stainless hoses do increase the bling factor, though. 

I AM a big fan of t-bolt clamps.  I blew off a bypass valve hose at an event, and it scared the crap out of me.  So I kind of went overboard clamping all the pressurized hoses down.  I even have those fancy spring-loaded clamps on my pressurized air intake hoses.

-Steve

p.s.  Do you have a 6 speed in your car yet?  If not, you may want to invest in a few extra 5 speeds (or a Quaiffe gearset). 

Steve,

I  suppose it could have been the tune, but nothing seems to show any detonation, and we had put 104 in the tank instead of the pump gas we normally run on as insurance.  Anyway, we had already purchased a Megasquirt to put on the car so engine management will be upgraded along with everything else.  BTW, the new target HP is 300 HP, good thing I ordered that dual feed rail .

 I am still running the 5-speed, but I hear you about the spares.  I may jump to the 6 speed next year, but need to figure out what rear gears to run with it.  I am still churning trying to get things back together for Topeka. ( I will see you there)  Work threw me an unplanned trip to DC, so I loose a week of reinstall time.  Oh well... that's how it goes.

--Chris

MNbiker:

My last engine lasted 5 seasons with a stock bottom end at 15.5 psi.  I put another stock bottom end back in the car, as I can buy several $1K stock engines for the price of a single built engine.

 With Rods now only $400, I don't see any reason not to throw a set of rods in the car, the stock pistons can take it. When I complete my new Intercooler/Radiator setup, my car will probably be pushing 18psi....on the stock bottom end. That has me seriously contemplating a set of ETD rods and ARP Head Studs = $550 and you have a bullet proof bottom end for 300rwhp, which is cheaper than a $1k junkyard engine.