Phone # for SF Motorsports? or other source for Borla?

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

Aaron Buckley wrote:

If anyone wants a SuperTrapp end cap real cheap, let me know

-AB

Only dropped once ...

Richard Casto · **Posted:** Tue Dec 14, 2004 5:57 pm

Wes Eargle wrote:

Dios mio. So now both the trailered Miata and Celica are going to sound like angry bumblebees?

I seem to remember that it was announced somewhere (at event, listserv, forum post, ?) that one of our regular sites would start needing to meet a specific sound level. Was this Sanford and was this due to the new school being built?

Does this ring a bell with anyone? If so, will that impact people's plans to run open pipe and/or really loud cars?

Dan Ecclestone · **Posted:** Tue Dec 14, 2004 6:45 pm

Thanks for all the responses.

I may very well just have a local shop make something for the miata, as I've had good luck doing this in the past. The Borla looks really nice but its hard to justify spending more than $300 for one. Best price so far is $365 shipped

http://www.autopartswarehouse.com/perfo ... _year=1991

Adam Ligon · **Posted:** Tue Dec 14, 2004 9:26 pm

Richard Casto wrote:

Wes Eargle wrote:

Dios mio. So now both the trailered Miata and Celica are going to sound like angry bumblebees?

I seem to remember that it was announced somewhere (at event, listserv, forum post, ?) that one of our regular sites would start needing to meet a specific sound level. Was this Sanford and was this due to the new school being built?

Does this ring a bell with anyone? If so, will that impact people's plans to run open pipe and/or really loud cars?

That is rule is for ALL events sites, now.

Kevin Hassell · **Joined:** Wed Sep 08, 2004 8:50 pm **Posts:** 174

so who is the holder of the sound gauge? is there some way someone can test out their car before the first event to make sure it is below the limit?

i mean.. its not THAT loud..

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Adam Ligon wrote:

Well lets be honest you get what you pay for.

A custom exhaust ready to install for a car is going to fit right, the first time. Not develope rattles and probabaly last longer than a shop done version. Also its going to have mandral bends, not chrush bends like a loacl place will make.

Now that being said I have both kinds of my various cars, bought and locally made.

Adam I agree with you in principal. But depending on the product/manufacturer you don't get what you pay for in product quality. You get to pay a lot of money for their marketing.

Borla makes a good quality product for the most part. But the price is too high. And it is not just Borla. B&B TriFlo, PowerPulse, Corsa etc make expensive custom fit catbacks. For the most part they do fit clean the first time. They do last. But I still think at too high a cost.

Flowmaster, Walker Dynomax, Magnaflow etc. all come in cheaper. They use aluminized steel for their low end and stainless steel for their high end. Their prices are better. But yes some of their designs are not the best. But they're half the price.

Since I don't have a lift in my garage I don't do exhaust work. I'll let Henry do it. Even if it is a kit. For what little he charges I'll get it installed right and if minor adjustments are needed he'll do it on the spot.

I hate doing exhaust system work...

Graham

Donnie Barnes · **Posted:** Wed Dec 15, 2004 10:13 pm

FWIW I don't expect the Miata to be any louder than our Spyder was, which with the Supertrapp was plenty below SCCA dB levels at the few events where they've had a meter. I'll probably check mine to make sure, though, as I have a sound pressure meter somestinkinwhere.

Aaron, OTOH, was probably over that limit with that car. I don't think any of the National events he was at last year had a meter running, though.

My Spec Miata with a straight pipe and an end-turn was fine with the normal limits as long as you turned the end-turn away from the meter. ;-)

--Donnie

Aaron Buckley · **Posted:** Wed Dec 15, 2004 10:26 pm

Donnie Barnes wrote:

Aaron, OTOH, was probably over that limit with that car. I don't think any of the National events he was at last year had a meter running, though.
--Donnie

Ft. Myers Tour had a decibel meter, and I came out at full throttle at 92 db at 50 feet. Since I went to the 'shorty' design, it's gotten a lot quieter

-AB

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Aaron Buckley wrote:

Ft. Myers Tour had a decibel meter, and I came out at full throttle at 92 db at 50 feet. Since I went to the 'shorty' design, it's gotten a lot quieter

-AB

You said the Supertrap made it look like you were down on power on your last dyno. And now you're going to this 'shorty' design. Sometimes a straight pipe is not the best way to get more hp/tq. It's been proven that certain exhaust systems are better than a straight pipe.

Also have to look at the power curve with your solution. I've seen some pretty wild numbers advertised by these aftermarket makers. Some also reprogrammed the computer specifically for their exhaust just for the dyno run. I've requested graphs from dyno testing on supposed 'custom' catbacks for my car. Most never respond or send me a graph from a completely different car. If they designed the catback specifically for my car then they should be able to easily show me a graph. So far only a couple have done so and only one will guarantee the numbers with completely stock engine and computer. When many of them say 'custom' they only mean the fitment.

The one that was truly custom designed for my car was done for fitment, resonance, and power. It produces 10hp/11tq at the wheels across the spectrum from 2500-5500rpms.

On a small engine with low hp/tq then going to a wide open exhaust may make nice hp gains at 5000rpm and up. But at what sacrifice on torque down low? What rpm do you typically keep the car at for most of your run and what is the power gain/loss at that time? Just curious.

Graham

Aaron Buckley · **Posted:** Wed Dec 15, 2004 11:04 pm

I originally had a straight pipe with a SuperTrapp end cap to control back pressure. When I cut it from about 3' to 6", the amount of flow changed. Thus, running no end cap produced the best result, with the best torque around 4400 and more hp up top.

Preferrably for my car, I want to run most of my time between 7600-8600 rpms

I still have a lot of tune time left... - AB

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Graham Jagger wrote:

Aaron Buckley wrote:

Ft. Myers Tour had a decibel meter, and I came out at full throttle at 92 db at 50 feet. Since I went to the 'shorty' design, it's gotten a lot quieter

-AB

You said the Supertrap made it look like you were down on power on your last dyno. And now you're going to this 'shorty' design. Sometimes a straight pipe is not the best way to get more hp/tq. It's been proven that certain exhaust systems are better than a straight pipe.
The one that was truly custom designed for my car was done for fitment, resonance, and power. It produces 10hp/11tq at the wheels across the spectrum from 2500-5500rpms.

On a small engine with low hp/tq then going to a wide open exhaust may make nice hp gains at 5000rpm and up. But at what sacrifice on torque down low? What rpm do you typically keep the car at for most of your run and what is the power gain/loss at that time? Just curious.

Graham

I have never heard a valid technical explanation about how you could possibly lose torque at any RPM by reducing backpressure and restriction after the cat. Sure, header and crossover design can change the resonance point, but from the cat-back I don't buy it.

Can anyone explain how it's possible?

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

MikeWhitney wrote:

I have never heard a valid technical explanation about how you could possibly lose torque at any RPM by reducing backpressure and restriction after the cat. Sure, header and crossover design can change the resonance point, but from the cat-back I don't buy it.

Can anyone explain how it's possible?

Let me go do some digging. I went through this a couple of years ago when I was hell bent to redo the exhaust system in my car. I found that no mufflers altered the power band. All the low end grunt on the engine moved up. Nice for top end power but not for off the line performance. My factory cats are also fairly high flowing and good up to about 400hp (true dual exhaust system).

Rich Anderson · **Posted:** Thu Dec 16, 2004 8:37 am

MikeWhitney wrote:

I have never heard a valid technical explanation about how you could possibly lose torque at any RPM by reducing backpressure and restriction after the cat. Sure, header and crossover design can change the resonance point, but from the cat-back I don't buy it.

Can anyone explain how it's possible?

At certain RPM, the design of the exhaust system can over-scavenge the combustion chamber due to negative pressure in the system and draw out some of the incoming air-fuel mixture. By increasing back-pressure, you can effectively curb this over-scavenging. In effect, your exhaust system can work too well at certain RPM and hurt power.

Graham Jagger · **Joined:** Fri Aug 29, 2003 12:53 am **Posts:** 1718

Rich Anderson wrote:

At certain RPM, the design of the exhaust system can over-scavenge the combustion chamber due to negative pressure in the system and draw out some of the incoming air-fuel mixture. By increasing back-pressure, you can effectively curb this over-scavenging. In effect, your exhaust system can work too well at certain RPM and hurt power.

Thanks Rich. That's exactly what I had in my notes. All my research pertains to small block chevy V-8s. Certain cam/head/lifter combinations have issues with using a straight pipe. As I understand it. The exhaust valve will not be completely closed on one bank before the intake valve opens. Too much flow, as in a straight pipe, will actually suck raw fuel out of the engine and rob the current cylinder that is on the intake stroke.

This may be a non-issue with an inline 4 cylinder. It may also be a non-issue with most cars with catalytic converters. But not all.

I think maybe I'll go start a thread in the Tech Section about exhaust systems since we hijacked Dan's original thread.

Graham

Todd Breakey · **Posted:** Sun Dec 19, 2004 5:02 pm

Kevin Hassell wrote:

so who is the holder of the sound gauge? is there some way someone can test out their car before the first event to make sure it is below the limit?

The dB meter is in the bus. I think it is in radio box, Mike can correct me if I'm wrong.

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