CATBACK QUESTION! (ABBA FAN, your wisdom is needed)

[VSCristian]

I have a VS Acclaim, V6.. stock except for the mace memcal, My exhaust is cracked and I was going to replace it with a 2.5inch catback.. I was looking at a few systems:

lukey and redback 2.5inch catback, centre and rear muffler, single exit pipe

lukey and redback 2.5inch catback, centre muffler only, then single pipe to the end

redback 2.5inch catback, centre muffler, rear muffler with dual 2.25inch exit pipes..

I'm after flow and performance ... which system would be the best? and, would the single muffler system drone or sound tough?

[VSCristian]

COMMODORE VS V6 IRS SEDAN 2.5" CAT BACK EXHAUST - eBay, Other, Car, Truck Parts, Cars, Bikes, Boats. (end time 04-Nov-10 20:53:15 AEDST)

[Not_An_Abba_Fan]

It doesn't really matter on a fairly stock V6. Which ever system you want to put on it, go for it. For optimum performance, the 2 1/2" is too big anyway, people just fit them because that is what is being sold.

The best system is keeping the stock size, but using straight through mufflers. Fit extractors for more torque and top end.

With a V6, the bigger the pipe the deeper the sound, manufacturers went with 2 1/2" because it didn't lose too much performance but made it louder and deeper. That is what the masses wanted so that is what is being flogged off to them. Not many people really care about performance on a V6 anyway, they just want it louder, and we all know, noise equals power.....

[PanthaVS]

For optimum performance, the 2 1/2" is too big anyway.

The best system is keeping the stock size, but using straight through mufflers. Fit extractors for more torque and top end.

I'm curious, starting with a stock V6. I got the S/C CAI and am looking at putting in 1.9:1 rockers. What would be best for a exhaust system with that setup?

[HamaTime™]

It doesn't really matter on a fairly stock V6. Which ever system you want to put on it, go for it. For optimum performance, the 2 1/2" is too big anyway, people just fit them because that is what is being sold.

The best system is keeping the stock size, but using straight through mufflers. Fit extractors for more torque and top end.

With a V6, the bigger the pipe the deeper the sound, manufacturers went with 2 1/2" because it didn't lose too much performance but made it louder and deeper. That is what the masses wanted so that is what is being flogged off to them. Not many people really care about performance on a V6 anyway, they just want it louder, and we all know, noise equals power.....

Exactly what my exhaust guy told me, 2.5" Is too big for optimum performance.

So stock pipes, just replace the muffler and cat you reckon for optimum flow and torque.

[VSCristian]

it is my rear muffler that's cracked, so I should get a straight through centre muffler, and get another stock rear muffler? do they come in straight through?

[klampy]

my dads vs has lukey headers, stock cat, lukey 2.5 and straight rear pipe in a cammed+chipped+bored motor+s/c CAI but stock element (such a fool) and it sounds tuff as nails!

[VSCristian]

I'm going for performance over sound, anyway.. cammed+chipped+bored motors would make more exhaust gasses than only chipped ones...

I am considering going 2.5inch.. but i dont want to lose anything... especially down low, so im undecided

[HamaTime™]

Yes, but with a V6 it can get a bit overkill, too large a pipe and you lose some bottom end power, like when you take out your rear resi, it drops a bit of throttle responsiveness.

[hsv vt s/charge]

Id go standard pipe with headers, high flow cat wouldnt be necessary for just a chip, nice straight resi which wont affect flow just keeps it quiet in the cab and the back is up to you. I have a straight through sporty on the end of my vt and there is nice note all round and beefy when you punch it with no loss of power. But i have a lil different setup to you.

[PanthaVS]

I'm curious, starting with a stock V6. I got the S/C CAI and am looking at putting in 1.9:1 rockers. What would be best for a exhaust system with that setup?

** Bump **

[Z2TT]

I've always wondered about this and found it hard to understand.

From what I've understood during lots of research on this.

1. Anything after the tuned section of the exhaust (headers) is a restriction.

2. Backpressure is not what you want, it's exhaust gas velocity, back pressure is just a side effect.

3. On cars with badly tuned headers, the rest of the exhaust will have a bad impact if you increase size too much.

I've seen dyno graphs of 2.0L Hondas with 3" Exhaust upgrades and no loss in lower anywhere in the rev range. I don't know if it's related to the engines head/cams or just purely how you design the headers but as far as commodores go people seem to go either 2.25" or 2.5" but not higher.

[Not_An_Abba_Fan]

** Bump **

Even with that set up, the "best" exhaust is the stock size with straight through mufflers.

I've always wondered about this and found it hard to understand.

From what I've understood during lots of research on this.

1. Anything after the tuned section of the exhaust (headers) is a restriction. Spot on. A car will make more "power" with no exhaust at all.

2. Backpressure is not what you want, it's exhaust gas velocity, back pressure is just a side effect. Spot on again. To make more torque (which is actually what you want) you need an exhaust system that aids the scavenging effect of the extractors. This will draw the exhaust along the pipe and in turn "suck" all the spent gases out of the head making room for more oxygen.

3. On cars with badly tuned headers, the rest of the exhaust will have a bad impact if you increase size too much. All street cars have badly tuned headers. They are made to get the best average across the entire rev range, not for a specific purpose as are race headers.

I've seen dyno graphs of 2.0L Hondas with 3" Exhaust upgrades and no loss in lower anywhere in the rev range. I don't know if it's related to the engines head/cams or just purely how you design the headers but as far as commodores go people seem to go either 2.25" or 2.5" but not higher. Not entirely accurate. A change of the exhaust system will shift torque curves, this will change the "power" reading. By fitting a 3" to a Honda, because the car is so short, the exhaust doesn't have a chance to cool down and bank up in the pipe creating backpressure. It may have a good dyno readout, but it will have no acceleration.

[soop]

That last example is a great reason why you should base mods off what you see happen on a dyno.

[Z2TT]

Any guys here have dyno readouts from exhausts on a V6? Possibly before and after.

[GTP 85]

This is a comparison of two exhausts on the same car, dynoed within one day. (The engine isn't standard though). Before i ever had a twin system on it, i had a single 2.5 with stock cat and HM headers and it didn't perform as well as the twin systems.

Red line: HM headers, twin stock cats, twin 2 inch pipes, lukey mufflers

Blue line: Pacemakers, twin ballistic metal cats 100 cells, twin 2-1/4 pipes, lukey mufflers

10rwhp (approx. 7.5rwkw)

[PanthaVS]

I'm curious, starting with a stock V6. I got the S/C CAI and am looking at putting in 1.9:1 rockers. What would be best for a exhaust system with that setup?

Even with that set up, the "best" exhaust is the stock size with straight through mufflers.

So in taking that on board, (as well as the rest of this thread) i have 2 options.

System 1. pacemaker tuned length extractors (2" outlet flange), 2" y-piece to a 2 1/4" flange, 2 1/4" sports cat (say 200cpsi) and 2 1/4" cat-back system with straight through sports muffler and resonator??

System 2. pacemaker tuned length extractors (2" outlet flange), twin 2" pipes through twin 2" sports cats (say 200cpsi) and twin 2" straight through sports mufflers and resonators??

System 3. Like the calais stock system with twin cats.

See picture:

[PanthaVS]

*** bump ***

[The1]

If your going with a Dual system you could use a X system, gives best flow as either bank can share the twin exhausts, but obviously this would be overkill for NA V6

[PanthaVS]

If your going with a Dual system you could use a X system, gives best flow as either bank can share the twin exhausts, but obviously this would be overkill for NA V6

I just scored a set of pacemaker extractors for a nice price, so now i need to work out my setup so i can start getting the rest of the parts.

I'm really looking at the twin cat idea (offers least restriction?) with a single system after the cats. (SYSTEM 3 in the pic above)

But I also had a thought, Since the outlet of the pacies is only 2", and the system doesn't increase to a 2-1/4" system till after the Y-Piece. The Cats are in a 2" section of the exhaust.

BUT, to increase the flow, (Reduce restriction) what if i used Enlargers/Reducers just before and after the cats, so as i can use larger diameter cats? (2-1/4" cats are easier to get)

Is this the best idea? Thoughts?

[cattz]

I know it's an old post but still an interesting read.
I've got Stock internals VS V6. CAI with K&N filter, Greenfoam memcal and 2 1/2" sytem.
As i'm mainly after torque and fuel economy, should i just put the standard system back on with a different rear resonator (i like twin outlets).
Don't want noise as noisy V6's sound sh*t. (Unless it's V8 of course).