Another Exhaust Thread

[RevNev]

I can definitely understand the principle behind what you say, I just don't believe it has any relevance to a street driven car and therefore I go for what sounds good to my ears which I realise may not sound good to the next person and especially one of my neighbours from years back.

It's like big brakes on a street car, they look great but their real advantage over the usual smaller stock braking systems fitted to most cars is being able to make multiple hard stops before starting to fade.

Where a smaller stock setup will fade after one emergency stop but if you need more than that on a street driven car then you probably should change your driving style.

Choosing an exhaust by the way it sounds is another level of customisation I've done myself plenty of times on a road car as it doesn't make a lot of difference to have any real purpose. However most of the "big" headers and exhausts are recommended by someone perceived to have exhaust knowledge claiming it makes more power. "You'll need a 3" if you cam an LS3" implying that a 2.5" is too small and will rob the cammed engine of power. To use a 3" exhaust, the engine needs to make close to 600hp (440kw flywheel) over 7000rpm otherwise a good 2.5" is plenty big enough.

Big rear brakes on a race car tend to lock rear wheels and need bias valves screwed almost out nearly blocking the rear brake line. Half of the big road car rear brakes without ABS would be locking up rear wheels all over the place on the track. For good brake balance with hard braking and a lot of weight transfer to the front, it's surprising how small rear brakes can be. It's likely the early Redlines with Brembo's on the front only and stock rear brakes had a better brake balance than 4 spot Brembo rears, but they certainly don't look as good with stock brakes on the rear!

 

[Not_An_Abba_Fan]

Big exhaust and headers DO make more power. Torque curves are different, so the power curve is different, but on a dyno, a 3" twin will make more power than 2 1/2" twin.

 

[RevNev]

Big exhaust and headers DO make more power. Torque curves are different, so the power curve is different, but on a dyno, a 3" twin will make more power than 2 1/2" twin.

Yes, they most certainly do when the engine can consume enough air to use the exhaust's greater flow potential. However, if big headers and a 3" exhaust makes more power on a stock or mild LS3 than smaller headers and 2.5" exhaust, it's the headers, cats or exhaust configuration not the pipe size. Often when a 3" exhaust makes more power than a 2.5" and this can happen, it's the cats or restrictive mufflers on the 2.5" system. All cat and 2.5" exhaust configurations don't make the same power, some are better than others!

 

[Not_An_Abba_Fan]

I know how it works, been doing it for 35 years as well as drag and circuit exhaust development.

 

[DrewPeacock76]

Ok so I ended up getting a 2.5" X-Force cat back system a few weeks ago.
I'm happy with the deeper note but it is sooo quite. Admitting I have have only driven it approx 3 times since it was installed.

Wondering what my options are in replacing the rear mufflers.....

 

[RevNev]

Wondering what my options are in replacing the rear mufflers.....

You'll get a better note with less drone removing front mufflers from the system to make it louder.

 

[panhead]

Ok so I ended up getting a 2.5" X-Force cat back system a few weeks ago.
I'm happy with the deeper note but it is sooo quite. Admitting I have have only driven it approx 3 times since it was installed.

Wondering what my options are in replacing the rear mufflers.....

Shoulda went 3 inch






.

 

[Ginger Beer]

First. If there are mufflers or big resonators in the mid pipe swap them for resonators, or shorter resonators

See how that sounds

Then, if required. At the rear swap the big mufflers for smaller straight thru mufflers

I've always been a fan of getting an exhaust built at an exhaust shop

Once good engineering principles has the header and front/mid pipe sorted, you can test and adjust rear mufflers prior to welding it all up and driving out the door

You can get a twin 2.5" sounding good, you just need to use the right quality parts

I've never been a fan of 90% of "bolt on" exhausts, especially when the ability to support your local exhaust shop keeps the dollars in your own community

 

[harrop.senator]

First. If there are mufflers or big resonators in the mid pipe swap them for resonators, or shorter resonators

See how that sounds

Then, if required. At the rear swap the big mufflers for smaller straight thru mufflers

I've always been a fan of getting an exhaust built at an exhaust shop

Once good engineering principles has the header and front/mid pipe sorted, you can test and adjust rear mufflers prior to welding it all up and driving out the door

You can get a twin 2.5" sounding good, you just need to use the right quality parts

I've never been a fan of 90% of "bolt on" exhausts, especially when the ability to support your local exhaust shop keeps the dollars in your own community

Unfortunately it's the price of the labour for mandrel bend. Most times is cheaper to fit an Australian made redback and adjust the mufflers.

The quotes I got to supply mufflers , v bands , cats and hotdogs and have them just do the piping and welding was $1200 all the way up to $1800. That was for twin 2.5" diff dump or if can fit boom tube style side exit.

Crush bend was $600 quote.

I'm buying a bend kit and just doing it myself now I've got no license lol.

 

[RevNev]

Most times is cheaper to fit an Australian made redback and adjust the mufflers.

I've mentioned this before in relation to exhaust note and Lukey were the "note masters" with their muffler designs. Redback and Manta use Lukey designs and always sound good! It only amounts to using the right type of perforated tube and fibreglass packing to get a great note, it's not rocket science at all, yet most aftermarket exhaust suppliers tend to sadly stuff it up deviating from the old Lukey "note master" design.

I've fabricated exhausts for 44 years and the last 27 years primarily race car exhausts, so I've got the gear to easily chop and change things for my own cars. I messed around with a 340 Maloo midpipe, made a "proper" X-pipe and knocked up a couple of resonators to replace the hot dogs, cut the bimodals open and changed the design over a couple of weekends but cost wise, I'd have to charge 3.5k for a job like that to make it viable, way more than most can pay for an exhaust. Custom exhaust stuff is massively time consuming and costs money to get that perfect job and note if you're not equipped to do it yourself unfortunately.

It took me all day to cut the tailpipes and get the bimodals centred in the bumper cut outs correctly, they hang too low on a ute. I'd have to charge about $800 to do that as viable retail job otherwise mechanically, you'd make more money changing oil and brake pads.