exhaust sizing for V6

[Immortality]

i've been doing a little math here. some have suggested that the ideal size exhaust for the Holden V6 buick engine is 2.75" now this is a very difficult size to find (i've never seen one that size, have you) so most opt for the 2.5" which is a little undesize but performs better then a 3" on a fairly stock engine with a few mods. now, doing the math a twin 2" system should produce approximatly the equevalent flow to a single 2.8" system which is much closer then the single 2.5" system. has anybody out there experimented with this type of setup on a V6. any ideas on this comments etc please

 

[1991_Vn2nV]

Theres a few out there, twin 2.25 inch is more popular which flows more than a 3"...

The reason is, most people willing to spend the dosh on a twin system are going for more mods. There is a big difference in price between a single and dual system.

Im going for a dual 2.25 inch to mufflers, 2.5 inch through the resonators... then 3 inch from the resonators into some twin tips

 

[yZoH]

i'm running Lukey extractors into Cat, into 2 1/4" system into hi-flow muffler, straight piped....

Cheers
MaT

 

[Immortality]

i have access to a reasonably well equiped workshop at work, including pipe bender, mig welder etc so i might have a go at doing it myself. can't be that difficult, just gotta get some exhaust tubing and 2 high flow mufflers. we aren't required to run cats over here so thats one less thing to worry about but i might need to find a twin inlet resonator etc for the rear as i don't want the boys in blue folllowing me

 

[AklHoon]

One of our machanics @ work has a VS HSV and rekons just to fit a factory V8 big bore exauste ,he rekons make the ol V 6 note only sound nice and mean but make it fly,gunna give it a shot anyways lol

 

[Surfwagon]

I don't know where you're getting your info that makes you think you need bigger than single 2 1/2" on a N/A V6.
If it's a manual with big cam and lots of revs then maybe 3" will be ok but you will loose low down torque and you'll need to rev it all the time to get decent acceleration.
If it's an auto the 2 1/2" would be the max unless it's set up fro the drags and the same applies as per the manual if using a bigger exhaust.
I'm making 196 rwkw with a single 2 1/2" mandrel exhaust with no drone and a nice deep note.
The article in Steart Machine they said that 3" was the go but if you read the article fully they are talking about highly modified engines and not neccessarilly motors that are going to see street duty.
There's an old hot rodding saying and it still applies today "Horsepower wins races but Torque rules the street".

 

[Immortality]

i was thinking more in the future when i finally get round to getting my supercharger. the article in streetmachine didn't actually give a lot of info and they are only after good 1/4 mile times and not street driveablilty, a 3" is definitly to big for a V6 that is used for the street unless you didn't mind not having a bottom end. i had suggested a twin 2" system because it has about the same volume as a 2.8" zorst and i've read in a few threads in the JC forum that the ideal size for a zorst is 2.75" which of course is not avail. right now i'm thinking 2.5" as it's simple and will leave me extra dosh for other mods:yeah:

 

[smaddock]

There's an old hot rodding saying and it still applies today "Horsepower wins races but Torque rules the street".

Thats where higher than factory stally's come into play They make up for the lack of low-end torque.

 

[RVN 355]

single 2 1/4" -2 .5" enough for a 3.8Litre, gees,most 5L v8's flow 130-160rwkw on a 2.5" system so whats this sayin.

I agree with: SURFWAGON: loss will occur in the low down torque range.

If you are will too pay for Headers that flow into twin system,2 x Cat's, 2 Mufflers,Issues with vibrations,fuel tank,more costing in labour,pipe work,Flanges,Welds and what ever be sure but dont expect huge Numbers with 2 2.5" off Exhaust on A Stock 3.8L

 

[Immortality]

i was talking about a twin 2" system not 2.5". we don't need to run cats on them here in NZ as they weren't fitted as standard here. i'd be doing most of the work myself so would save $$$$$ there and the engine certainly wouldn't be stock. i'll be picking up a second set of heads soon that will be fully ported and polished etc, portmatched intake, full HPC treatment etc cam/ roller rockers and then eventually a supercharger when i can con the little missus into that!!!