Single or twin zorst on 3.8.

[Dave6179]

G'day. I've just fitted a stage 2 memcal to the wifes VN Calais. Lots better to drive, more economical, even sounds different. The zorst sounds like it's struggling to 'let it out'. Has the std 2.25 after my extractors, but I replaced it all with mandrel bends, 3 chamber muffler (similar to Flowmaster etc) removed the cat, 2.5 tailpipe. Will it work better with a bigger single or same size twin system? I do everything meself so cost isn't an issue. I've read a bit on the '3800performance' website but nothing on this.
I don't wanna hear stupid **** about V8s or turbos... thankyou!
Have a good weekend!!!!

 

[Jxfwsf]

2.25" is about the perfect size for a 3.8L
2.5" single would be the biggest you'd want to fit.
Go to big and then you run into probs with back pressure and worse performance (all noise and no go).

 

[BOOSTER]

I agree N/A motor needs back pressure in the exhaust system!!!!! turbo and super chargers can have straight thru pipe.
If it's sound you want i would cut the resinator (last muffle box) and replace it with a straight thru pipe with a U bolt and it will rust itself tite leaving the rest of the exhaust system in tact,maybe fit bigger extractors.

 

[Dave6179]

I heard backpressure is bad many years ago. I found out different while developing my 179, then the mighty 202. Less backpressure the better.
Is the injected engine different? Not after noise... family/wifes car. It's deathly quiet now, but feels like it 'wants more'.
A lot of the aftermarket systems for the yank 3800 powered cars use 1 5/8 extractors, into single 3", then splits into twin 2 1/4 with quad tips. Maybe I should just try it. If it doesn't do the trick some kid with no clues will buy it!

 

[ducker85]

everything I've ever read about 3" single systems are positive and personal a 3" with both muffler and resi I think sound alot better then a common 2 1/2 singles.

exhaust at 3:50 https://www.youtube.com/watch?v=4JEgHraXu_M

 

[Dave6179]

Yeh, seen that ages ago. Just ordered a 2.5 baffled muffler, same as the one on it but bigger. I tried this muffler behind my 202... sounded like someone bashing a tin can with a stick. Was cool for a coupla weeks then I put the old custom one back. But the 2 1/4 was really quiet behind the std 3.8. Cam and compression made the difference I reckon.

 

[GothicKidd]

buicks are terrible, sound terrble no matter what.. maybe slap roller rockers on it.. might sound a bit better.

Go ecotec haha.

 

[Kiddo]

The back pressure myth always makes me giggle.

Taken from another site as i'm too tired to type it myself;

Back pressure at it's most extreme form can lead to reversion of the exhaust stream - that is to say the exhaust will flow backwards, which is...er... is not good. The trick is to have a pipe that that is as narrow as possible while having as close to zero back pressure as possible at the RPM range you want your power band to be located at. Exhaust pipe diameters are best suited to a particular RPM range (remember the pulses!). A smaller pipe diameter will produce higher exhaust velocities at a lower RPM but create unacceptably high amounts of back pressure at high rpm. Thus if your power band is located 2000-3000 RPM you'd want a narrower pipe than if your power band is located at 8000-9000 RPM.


My personal experience suggests that a twin 2.25 is best. As the pipe diameter is small enough to keep the exhaust velocity up, but still have a higher flow rate when needed.

 

[Reaper]

I agree N/A motor needs back pressure in the exhaust system!!!!! turbo and super chargers can have straight thru pipe.
If it's sound you want i would cut the resinator (last muffle box) and replace it with a straight thru pipe with a U bolt and it will rust itself tite leaving the rest of the exhaust system in tact,maybe fit bigger extractors.

Nope - back pressure is a complete fallacy. In short - do you fart any better with a cork up your arse??? What works best is an exhaust system which will flow the rev range you use 80% of the time without restriction. For a road going NA 3.8 that will be what Jxw suggested.

Bigger is not always better when it comes to pipes. All that happens is you slow down the gas flow killing the scavenging effect that you are trying for with extractors (even stock manifolds deliver it to some extent). Just remember - even though your car may pull 1.21 gigawats of powah at 8million rpm, on the street, it's mostly going to be around 2,000rpm - 4000rpm (or there abouts) 90% of the time which is where you should be aiming to have your exhaust, cam, motor tuned for best results.

Some handy links:

Magnaflow Technology
Exhaust Size Calculator
Pipe Sizing Calculator

 

[delcowizzid]

totally stock engine with Cold air intake best street setup is the big competition pacemakers into twin 2.25" all the way to the rear with the best flowing mufflers you can find