Exhaust question.

[VT GEN3]

Hi,

I have a twin 2.5 inch x-force exhaust system off a set of 4-1 long extractors. Is there any power to be had by removing the rear resonators? anyone dynoed a before and after. What about the sound? The exhaust place says absolutely no difference to power but maybe lose torque??

to leave on or to take off?

[ace078]

Whats you ride???

I have try Y headers, into 2.5" redback center mufflers and 2.5" straight through tail pipes. Torque is great, have no dyno results to say how much, but I have driven plenty of different LS1 modified cars, and mine fells great down low. I think the Try Y's make all the difference down low.:thumbsup:

[busta]

Can i suggest you talk to Dave or Dale at Castle Hill Exhaust (sponsers). They could answer any question you have.

[Nutter]

rear resos on those systems are already usually straight through so removing them wont efftect power at all only noise.

[RED R8]

I have an Xforce 2.5 cat back with HSV Headers I drove it for a couple of weeks then decided I wanted it louder so I unbolted the resi and tried it it sounded odd because the pipes ended over the diff but decided to get two new pipes extended out the back deleting the resi and must say it sounds heaps better it is louder at all revs and chunkier sounding power has not changed performance seems exactly the same, do it you will love it.

[swmn]

Hi,

I have a twin 2.5 inch x-force exhaust system off a set of 4-1 long extractors. Is there any power to be had by removing the rear resonators? anyone dynoed a before and after. What about the sound? The exhaust place says absolutely no difference to power but maybe lose torque??

to leave on or to take off?


It really comes down to flow. Here you go:

Take you car to the 1/4 mile track with open 4-1 extrators (aka: long tube headers or LT's in the states). Attach collectors in your chosen diameter that are too long for your application.

For streetability on a 5.7l/346cid LS1 consider 2.5" or 2.75" collectors around 24-27" long beind your headers. For ultimate power and 1/4 mile ET start with 3" collectors around 20-24" long.

Spray a 1" wide strip of black spray paint down each collector, after you take the car off the trailer at a test and tune day. Get a good burnout in the box, but don't go crazy. You want to see, in the paint, the motor moving the car down the track, not the motor spinning tires in the burnout box. get a good run, this one matters.

Back in the pit, jack the car and look at the paint on the collectors. You should see dry paint near the extractors, the bubbled paint, maybe paint burnt off, more bubbled paint, then dry paint.

Where ever the paint got the hottest needs to be the center point of your future X or H pipe. Mark this point on each collector.

Remove the collectors. Cut each collector at the mark. Hopefully they are about the same length. Reinstall the collectors, keeping left to left and right to right.

Make another pass down the quarter mile with open headers and tuned length collectors. Expect slightly better ET/trap speed than you had before.

Calculate flywheel HP based on you vehicle weight, tire size, ET/trap, weather conditions and so on.

Build an exhaust sytem that flows 2.2 cfm per flywheel HP at 25" H2O suction. You will now have the quietest possible exhaust sytem for the street that lets you keep 99% of your ET/trap in the standing 1/4. Systems that flow less will have pumping losses. Systems that flow more will be louder than needed.

I don't know how to do this in metric units. If your exisiting mufflers are within 5% of optimum flow you probably might as well leave it alone.

M2c,
S

[PWNAGE]

I have an Xforce 2.5 cat back with HSV Headers I drove it for a couple of weeks then decided I wanted it louder so I unbolted the resi and tried it it sounded odd because the pipes ended over the diff but decided to get two new pipes extended out the back deleting the resi and must say it sounds heaps better it is louder at all revs and chunkier sounding power has not changed performance seems exactly the same, do it you will love it.

I have the same system and took the resi off the other day. To me it sounds heaps better, it's meatier and pops alot on down changes but at low revs it makes a booming sound that really drums into your head!

Is the booming that I have the same "odd" sound that you experienced? and did it go away after fitting the straight through pipes?

I'm going to the exhaust shop tomorrow and was going to fit hot dogs but if the straight through pipes sound OK I'd rather do that

[RED R8]

Mine sounded a bit rude unbolted it was just not a nice sound but with the pipes added sounded much nicer a few have said my car is a sweet sounding gen3.My previous car a VP SS had a noisy system so I had two hot dogs added it made no difference to the sound so I wouldn't bother just go straight through.You can get a rough idea of my sound in the exhaust sound file's it is not entirely accurate but you get the idea.

[PWNAGE]

Thanks Daz, after listening to your sound clip I'll be getting straight through pipes. Sounds sweet :D

[LS1WB]

We had the same system on a 6 litre, sounded great. The rear res will only take out the drown, slip in the x force hot dogs it will sound fine with a bit more bark. I think when you take out the hole lot you end up with great note on throttle but a bad annoying note at any criuse speed.