Topic: Exhaust - do I need it, or can I cut it off and throw it away?

Hi - We're trimming the fat on our car, which currently has the factory cat, muffler, pipes, etc.

I was hoping to save some weight (and maybe get some cash for the cat) by swapping to a bigger diameter exhaust header, and a straight pipe out the back.

Is there any requirement to have any sort of racing cat, muffler - or am I good with a simple pipe out the back?

Thanks for your help!

Re: Exhaust - do I need it, or can I cut it off and throw it away?

The rules have a section on the exhaust requirements

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Thanks, I found the rules - helpful!

Wondering if anyone has examples / recommendations of a cherry bomb / supertramp / resonator we could consider.

3.I.5 Noise Limit. Our noise limit is 92dB @50 feet @ W.O.T. What that boils down to is
no straight pipes allowed; please use at least one muffler or resonator. With these
heaps, a single Cherry Bomb or Supertrapp is usually plenty.

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Cherry Bomb is just one brand name for a cheap, flow-through "glass pack" muffler. They come in various lengths and for various exhaust pipe sizes; you can usually find them at regular auto parts stores.

Like the rules say, that's "usually" enough. If you're running something particularly high-revving (like a rotary), everyone else at the track will appreciate you using something more effective (like a stock muffler).

Command Pilot/Flight Director, Escape Velocity Racing
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Currently 1-2 vs. Team Fairlylame in the Class of 1964 Championships

5 (edited by rb92673 2020-10-17 11:08 AM)

Re: Exhaust - do I need it, or can I cut it off and throw it away?

What car/engine?

Some tracks are more restrictive than others too.

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Again, the question is so generic that it really can't be properly answered.  What car/engine/track, etc.  While Lemons doesn't run there, you need to be near electric car silent at Laguna Seca. As noted, rotaries are loud.  They also are sorta like a 2 stroke in that they are picky about exhaust.  A straight pipe on a rotary kills power (and everyone else will kill you).  Some tracks are pickier than others.  With most cars/tracks most any muffler/silencer is good enough but we don't know either of those bits of info.  We got dinged for sound with a 6 cyl BMW that was straight piped out the back at Buttonwillow.  Putting one of these on quieted it down enough to make everyone happy and probably helped on power a bit http://www.classicchambered.com/index.html

1990 RX7 "Mazdarita"  1964 Sunbeam Imp (IOE 2013 Sears Pointless) 2002 Jaguar x-type
Gone bye-bye
1994 Jaguar XJ12 (Winner C-Class 2013 Sears Pointless)  1980 Rover SD1 (I Got Screwed 2014 Return of Lemonites)

Re: Exhaust - do I need it, or can I cut it off and throw it away?

So how quiet should a chain driven mid engined GEO metro with a Ducati engine reving  to the moon be?

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Thanks for your input.

We've got a 4 cyl 2.0 T turbo (B207R / Generation 1 Ecotec). We've reset the ECU to ignore the cat and other exhaust sensors.

Our idea was to:
1. Swap out the exhaust header for a 3" version (perhaps this https://zzperformance.com/collections/e … rty-header) to increase flow and cooling.

2. Straight 3" pipe from the exhaust header to about 12" from the back.

3. Add one of these 3" cherry bomb race mufflers https://cherrybombusa.com/race-mufflers.html (or perhaps one of these http://www.classicchambered.com/index.html is better for power and sound?

Any thoughts or input on this is much appreciated.

Thanks!

Re: Exhaust - do I need it, or can I cut it off and throw it away?

timburrman wrote:

So how quiet should a chain driven mid engined GEO metro with a Ducati engine reving  to the moon be?

As the owner and hooner of an unmuffled Ducati, it will make all loud things sound quiet with the exception of top fuel.

That guy

10 (edited by OnkelUdo 2020-10-19 05:08 AM)

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Passaable wrote:

Thanks for your input.

We've got a 4 cyl 2.0 T turbo (B207R / Generation 1 Ecotec). We've reset the ECU to ignore the cat and other exhaust sensors.

Our idea was to:
1. Swap out the exhaust header for a 3" version (perhaps this https://zzperformance.com/collections/e … rty-header) to increase flow and cooling.

2. Straight 3" pipe from the exhaust header to about 12" from the back.

3. Add one of these 3" cherry bomb race mufflers https://cherrybombusa.com/race-mufflers.html (or perhaps one of these http://www.classicchambered.com/index.html is better for power and sound?

Any thoughts or input on this is much appreciated.

Thanks!

Unless your car is caged, seat, kill switch, fire suppression all installed and otherwise completely ready for tech...focus on that and reliability first and second.  "Adding lightness" comes after, except gutting the car.  Almost every new car owner underestimates by a factor of 10 or more the effort and time needed just to accomplish that.  If it comes down to the wire, a muffler shop can install an exhaust on the existing header in an hour.  If you realize the Monday before the race, your seat is such that your helmet is too close to the cage...much harder to fix in an hour.

Anything with a gen1 ecotec is likely to not be looking at a class win with a new team (almost no car is) so focus on getting on the track and having fun and make improvements later.

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Our Chrysler V8 had TWO cherry bomb style mufflers and even after testing all day Friday and passing tech inspection without incident, we were still black flagged 2 hours into the race (mind you, we were leading the race at the time) and told we couldn't come back on track until we made the car more quiet.

Food for thought.

The Pentastar whisperer

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Passaable wrote:

Hi - We're trimming the fat on our car, which currently has the factory cat, muffler, pipes, etc.

I was hoping to save some weight (and maybe get some cash for the cat) by swapping to a bigger diameter exhaust header, and a straight pipe out the back.

Is there any requirement to have any sort of racing cat, muffler - or am I good with a simple pipe out the back?

Thanks for your help!


you are going to want some sort of exhaust system. You can remove the factory stuff, but I'd add a performance muffler and you need the exhaust to exit outside the car. Typically on the pass-side. CO2 sucks and running around in a loud ash car for 1.5-2 hours gets old after about 10 minutes.

"get up and get your grandma outta here"

Re: Exhaust - do I need it, or can I cut it off and throw it away?

BTW "Cherry Bombs" do not flow that well.

"get up and get your grandma outta here"

Re: Exhaust - do I need it, or can I cut it off and throw it away?

A turbo acts as a sort of muffler so with that you are part of the way there.  I'd run one of those chambered exhausts and you should be good.  There are a few smartphone apps that measure sound (probably not super accurate) but should be close enough to work for this purpose.

1990 RX7 "Mazdarita"  1964 Sunbeam Imp (IOE 2013 Sears Pointless) 2002 Jaguar x-type
Gone bye-bye
1994 Jaguar XJ12 (Winner C-Class 2013 Sears Pointless)  1980 Rover SD1 (I Got Screwed 2014 Return of Lemonites)

Re: Exhaust - do I need it, or can I cut it off and throw it away?

You aren't going to win because you shaved 10lbs. Just remember that.

With exhaust, being too loud can actually be a driver fatigue issue. You want loud enough that you can hear the engine, but not so loud that you're getting hearing damage. We have to wear ear plugs now and I still get out with ringing ears. We don't violate the sound limit, but man our car drones inside.

Glass packs will burn out, faster with the added heat from a turbo.

reference, we have a saab B234R (2.3 turbo 4 cyl), 3" downpipe off the turbo then straight 2.5" from the rear of the subframe to the rear bumper. No mufflers, resonators, nothing. The turbo does a good job muffling enough to be below the sound limit, but man it's loud in the car. I've considered putting  something back in the system.

20+ Time Loser FutilityMotorsport
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Re: Exhaust - do I need it, or can I cut it off and throw it away?

Something to consider for anyone worried that their car makes too much noise:  You can buy a reasonably well-rated decibel meter for about $20 on amazon.   Will let you know how close to the limit you really are.  Cheaper and easier than adding more muffler if you're only half sure you need it.

Re: Exhaust - do I need it, or can I cut it off and throw it away?

TheEngineer wrote:

You aren't going to win because you shaved 10lbs. Just remember that.

With exhaust, being too loud can actually be a driver fatigue issue. You want loud enough that you can hear the engine, but not so loud that you're getting hearing damage. We have to wear ear plugs now and I still get out with ringing ears. We don't violate the sound limit, but man our car drones inside.

Glass packs will burn out, faster with the added heat from a turbo.

reference, we have a saab B234R (2.3 turbo 4 cyl), 3" downpipe off the turbo then straight 2.5" from the rear of the subframe to the rear bumper. No mufflers, resonators, nothing. The turbo does a good job muffling enough to be below the sound limit, but man it's loud in the car. I've considered putting  something back in the system.


I have no idea how some of the Miata guys do it. Honestly we run a V8 with a healthy exhaust, and when I go door to door with those guys I can't even hear my car. No way I could sit in that for more than 10 minutes.

"get up and get your grandma outta here"

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Our Corvette is a LOT more quite then our Camaro was...and the drivers love it.

Easier to hear the radio...no post stint headaches, etc..

Food for thought.

Team Sucker Punch:Winner Org Choice award Were the Elite Meet to Cheat 2015
Chevy Camaro (Tiger striped #38)  (1989-2017 RIP old friend)
Chevy Corvette 1984......and still racing!

Re: Exhaust - do I need it, or can I cut it off and throw it away?

While researching off road x pipes I came across this rpm act. I guess epa decided “track only” doesn’t save you from them. This explains it and makes it only take a few minutes to tell your elected officials how you feel.

https://www.sema.org/rpm-bill-summary

Re: Exhaust - do I need it, or can I cut it off and throw it away?

Tiptoe the rat wrote:

Our Corvette is a LOT more quite then our Camaro was...and the drivers love it.

Easier to hear the radio...no post stint headaches, etc..

Food for thought.

There is a sweet spot, too quiet is too quiet... the Passat with entirely stock exhaust is silent when you’re wearing a helmet. I bumped into the rev limiter on the straight because of this. We’re going to open up the exhaust a bit. Benz has a single 2.5” Flowmaster and it’s calm and quiet, but the sound is there enough to shift by sound, which is about right. Some cars are deafening when they pass, and that is just fatiguing...

#111 Tradewinds Tribesmen VW Passat Inde ‘20... shhh, the Benz is napping!
#888-Hong Kong Cavaliers Benz S500: formerly known as OMG Racing #140...
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Re: Exhaust - do I need it, or can I cut it off and throw it away?

Having been the object of numerous sound violations, both on track and on road (different cars)
I have learned a couple of things that might help.

Exhaust Noise Tips and Info:

+ Tech will want any side-exit exhaust to exit behind the doors, preferably behind the cabin.
+ Having no rear windows can lead to exhaust reversion into the cabin.
+ Large diameter exhaust tubing lowers the tone of the exhaust note.
+ BASS carries more sound energy, farther from the car. (Balto was EARSPLITINGLY,F-ing LOUD, but was high pitched and therefore 
    compliant)

+ Cold air carries sound waves better than warm air.
+ Wet air carries sound waves better than dry air.
+ You can find out where most tracks have their dB meters on the interwebs.
+ Directing your exhaust at the ground can help mitigate dB levels.
+ Directing your exhaust upward will help mitigate sound, a la Laguna Pipe
+ Directing your exhaust away from the trackside dB meter will help mitigate measured sound, a la Laguna Pipe
https://images.autotrader.com/scaler/620/420/cms/images/oversteer/2016/12-dec/lagunaseca/260090.jpg
https://i.ytimg.com/vi/6sdQZvUQq7Y/maxresdefault.jpg
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Re: Exhaust - do I need it, or can I cut it off and throw it away?

Balto was loud, but most of the sound was radiating out of the hood rather than coming out the exhaust.  So largely non-directional but kind of spraying upward.  It was really REALLY loud with the hood off.

And if you think it was annoying on the outside...  The muffler was inside the passenger door skin and completely exposed to the driver.

I _suspect_ the car would have passed Laguna sound despite the exhaust exiting on the right.  Maybe.