Xforce Varex Catback - Pontiac G8 Forum: G8 Forums - G8Board.com
Exhaust Tech Headers, Catbacks, Mufflers, lack of mufflers

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post #1 of 40 (permalink) Old 09-27-2018, 10:23 AM Thread Starter
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Xforce Varex Catback

Purchased and installed the Xforce Varex catback this week. It is very shiny and has very nice bends and welds. It included all new hardware. It's so shiny and fancy, almost too much for me- I'm used to crush bent aluminized. In quiet mode, it is the same volume as stock, except with a better tone, sounds more like a Corvette and less like a truck. There may be a tiny bit more growl right as you touch the accelerator. Unlike the stock exhaust which sounds like a rental Camry except at WOT, you can tell it is a V8 at all times, but it is never offensive or intrusive and could be an OEM exhaust. I can't comment on loud mode, because one of my valves is stuck shut and isn't working. Since it has an X pipe, I could probably start it up and drive easy on it with just one open, but I'm too OCD to attempt it... I contacted Xforce about a replacement and it is being worked, so I'll get back with y'all on that.
Install was not bad, just like any other catback. The main challenge was not having a lift or a helper. I also had a hard time figuring out which side was left and right on the piping closest to the cats (they are reversed in my attached pics). Those same pipes fit very tight to the car. The bolts on my cats were welded on, so it was harder to get the pipes far enough back to fit over the bolts on the cats while twisting them to get them to fit tightly against the underbody. I also had to take the hangers and place them on the piping before hand. Since this piping is dual 3", there isn't really enough room for the clamps to sit perfectly flush unless you have a power ratchet and can put them on the top.
The secondary O2 sensors were pretty snug on my old exhaust, let the PB blaster soak for an hour, then used a 22mm wrench, using the exhaust piping for leverage. I have an O2 sensor socket but it seemed to be just a little too big and was trying to round off the hex. Also I would've preferred the crush type gaskets that go in between the flanged connections, these were the more basic ones, made out of some kind of pressed metal shavings or something. The instructions said to use a sensor safe copper RTV, even on the slip fit connections, but I've always found that stuff to be really messy if you ever have to disassemble and not really help seal anything, so I didn't use it. I did torque everything to spec (80 lb ft) and there are no leaks. I like to use a little copper anti seize on exhaust threads, seems to help get them apart years later.
Overall, seems to be a really nice exhaust, kind of a let down that the valves do not work new in box, but I'm really looking forward to using them once it works!
P.S. Anyone in North AL need an OEM exhaust?
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post #2 of 40 (permalink) Old 09-27-2018, 05:46 PM
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Good you're satisfied, for the most part, with the new exhaust setup despite the defective butterfly valve. Hopefully, XForce will quickly resolve the problem and what kind of warranty do they offer?

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post #3 of 40 (permalink) Old 09-28-2018, 07:38 AM Thread Starter
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1 year on the electronics and 5 on the metal components. This thing is 304ss and will never see salt so it'll probably outlast the car. As for electronics, the motors are ~$30 so it's mostly just the pain of having to drop the muffler to replace it.
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post #4 of 40 (permalink) Old 09-28-2018, 08:57 AM Thread Starter
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Update. They are very responsive to customers and are mailing me a replacement motor.
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post #5 of 40 (permalink) Old 09-29-2018, 10:18 AM Thread Starter
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In the mean time, I figured out how to manually open the valve, for permanent loud mode. It is by no means obnoxious, my other LS with a louvered resonator and Thrush chambered muffler is louder. This Varex is drowned out by wind noise with the windows down by 50 mph. 4 cylinder mode has a little bit of an odd low tone and 1800-2000rpm has some drone, but not excessive. Not annoying when passing thru RPM but on the highway it gets old. Sounds really good at WOT, not raspy at all, very refined tone. The whole system reminds me of a Corvette with dual mode exhaust, just little louder in loud mode.

Last edited by earlingy; 10-03-2018 at 08:51 AM.
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post #6 of 40 (permalink) Old 10-07-2018, 08:26 AM Thread Starter
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Got my replacement motor installed. I definitely like having dual mode. In full open, it is pretty loud, and in quiet, it's like stock. The Smartbox allows you to put the valves at any percent you want, and automatically put the valves at any percent based on throttle, rpm, and speed. I still haven't came up with the perfect setup for all speeds and such. I can leave it 20 to 30 percent open and 4 cylinder mode is still dead silent, but you can actually hear the car, unlike stock. I'm having fun playing around with it. The only downside is your phone has to be on and have the app open to be in "smart" mode. You can still use the beeper and open/close, if you forget to open the app before driving away, just with less control.
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post #7 of 40 (permalink) Old 10-08-2018, 09:27 AM
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Appreciate the updates and hopefully the information provided in this thread will help someone contemplating purchasing this exhaust system.

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post #8 of 40 (permalink) Old 10-08-2018, 10:41 PM Thread Starter
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Yeah, I couldn't find much info on it is why I've tried to put some detail in. If anyone has any questions I'll be happy to help.
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post #9 of 40 (permalink) Old 10-09-2018, 08:55 AM
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I've had my eye on this exhaust since getting my G8. I might finally have to pull the trigger soon.

I'm currently running Kooks headers and midpipe to stock mufflers. I also have Solos, but that means it's straight piped, and that's just too much to drive around with. Does sound damn good though. My plan was to get cutouts, but at that point, I'm almost in as much money as just getting the XForce.

Has anyone connected the XForce catback to Kooks LTs?

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Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
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post #10 of 40 (permalink) Old 10-09-2018, 09:14 AM Thread Starter
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I can't say since I have the stock manifolds, but the Varex has a flat flange connection. You remove the curved "pinch" type gasket, the sort of cone shape one, from the stock midpipe, and install a flat gasket, the type that is the same shape as the flange, like what was used at the stock axle backs.
From the pics I found, it looks like the Kooks have the cone shape built into them. I'd have to see them in person to be sure, but I'd think you need some minor fabrication from a welder who knows how to weld stainless for them to work perfectly.
But I do think headers would sound good with this system, I was thinking about that this weekend...
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post #11 of 40 (permalink) Old 10-09-2018, 11:18 AM
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Quote:
Originally Posted by earlingy View Post
I can't say since I have the stock manifolds, but the Varex has a flat flange connection. You remove the curved "pinch" type gasket, the sort of cone shape one, from the stock midpipe, and install a flat gasket, the type that is the same shape as the flange, like what was used at the stock axle backs.
From the pics I found, it looks like the Kooks have the cone shape built into them. I'd have to see them in person to be sure, but I'd think you need some minor fabrication from a welder who knows how to weld stainless for them to work perfectly.
But I do think headers would sound good with this system, I was thinking about that this weekend...
Interesting. And good to know.

Kooks uses a ball/socket connection. No gaskets. Also, given the position of the connections, I'd likely have to hack part of the XForce off, which is a bit of a bummer. I'm sure any decent exhaust shop could do it. Just want it done well given it's pricey.

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post #12 of 40 (permalink) Old 10-09-2018, 03:30 PM
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I've been eyeing this up for awhile as well. Have always liked the bi-modal exhausts. Too bad the bi-modal SS mufflers aren't a direct swap or easier to find.

Too bad there isn't a better way to automated opening and closing the valves that don't rely on your phone. I've been eyeing this up for awhile as well. Have always liked the bi-modal exhausts. Too bad the bi-modal SS mufflers aren't a direct swap or easier to find.

Too bad there isn't a better way to automated opening and closing the valves that don't rely on your phone.

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post #13 of 40 (permalink) Old 11-01-2018, 01:30 PM
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Well, my XForce catback showed up yesterday. It is very nicely made, that's for sure.

Taking it to an exhaust shop on Saturday morning to have some connections pipes made (with HFCs) to mate it to my Kooks headers.

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Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
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post #14 of 40 (permalink) Old 11-01-2018, 02:59 PM Thread Starter
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Nice, let me know how it sounds with long tubes. I was thinking of adding some high flow cats in for a little more sound. It could definitely be more aggressive in full loud mode... But I'm definitely still loving the ability to change the sound. I drive in 20-35% mode a lot, no drone but sounds aftermarket, but I also end up in quiet mode and full loud at some point every week.
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post #15 of 40 (permalink) Old 11-01-2018, 03:07 PM
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Cool. I figure I'll play with it a bit as well, and see what works. Between the long tubes and cam, should be pretty rowdy in loud mode.

2 questions from install:

1. The instructions for the controller wiring.... was that pretty spot on? or how did you end up running the wire? my plan is to get it into the arm rest.
2. I haven't unboxed everything yet, but I noticed that the tips have stickers that say, "welding required". they sure look like slip joints. what did you do there?

Thanks

2009 PBM GT
Under the Knife Again
Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
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post #16 of 40 (permalink) Old 11-01-2018, 03:11 PM
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just wondering if there is way to just buy the mufflers instead of the whole cat back system ?
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post #17 of 40 (permalink) Old 11-01-2018, 03:15 PM
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Quote:
Originally Posted by gmpontiacguy View Post
just wondering if there is way to just buy the mufflers instead of the whole cat back system ?
That would be ideal. I did some searching on it though, and looks like that's been a recurring wish/hope, but has never been an option. Catback or nothing.

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Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
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post #18 of 40 (permalink) Old 11-01-2018, 03:39 PM
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going to see if i can get a set from Australia
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post #19 of 40 (permalink) Old 11-01-2018, 03:41 PM Thread Starter
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just wondering if there is way to just buy the mufflers instead of the whole cat back system ?
If you don't mind having custom welding done, you can purchase just the Varex mufflers from Summit. Just take them into any exhaust shop and they will have you up and running pretty quick. They could even fashion them up without cutting the existing OEM axle back so that you could go back to stock at home. I thought about doing that, but I talked myself into the catback for the x pipe sound, and because I thought it'd be cool to have that super shiny thing under the whole car at shows.

Quote:
Originally Posted by ebg8gt View Post
Cool. I figure I'll play with it a bit as well, and see what works. Between the long tubes and cam, should be pretty rowdy in loud mode.

2 questions from install:

1. The instructions for the controller wiring.... was that pretty spot on? or how did you end up running the wire? my plan is to get it into the arm rest.
2. I haven't unboxed everything yet, but I noticed that the tips have stickers that say, "welding required". they sure look like slip joints. what did you do there?

Thanks
1. Honestly, right now I just have the power wire ran through my trunk pass-through and to the console 12v outlet. I've been working overtime, and working on my house, plus Red Dead Redemption 2 came out (Hey, I always loved playing cowboys...). However, my plan is to tap into the ign 12v in the trunk that most people use to power on their subwoofers, and run it to a relay that powers the controller. That way all the wiring will be tucked neatly in next to the battery, and it will turn on and off with the car without using up my 12v outlets.
As for wiring the mufflers, I pulled the grommet in the trunk/fender near the battery, cut a small slit in it, and ran the power out there. I then ran the power across in the rear bumper/valance to the other muffler. The harness attaches to the mufflers "in series" so you won't have enough wire to go out to the left muffler, then go back inside, cross in the trunk, and go back out for the right muffler like I wanted to. I zip tied everything up tight and out of sight.

2. Yeah, I don't know why they say that, they are slip fit. Good thing too, because it took me a few tries to get the tips level.
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post #20 of 40 (permalink) Old 11-01-2018, 04:01 PM
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Quote:
Originally Posted by earlingy View Post
1. Honestly, right now I just have the power wire ran through my trunk pass-through and to the console 12v outlet. I've been working overtime, and working on my house, plus Red Dead Redemption 2 came out (Hey, I always loved playing cowboys...). However, my plan is to tap into the ign 12v in the trunk that most people use to power on their subwoofers, and run it to a relay that powers the controller. That way all the wiring will be tucked neatly in next to the battery, and it will turn on and off with the car without using up my 12v outlets.
As for wiring the mufflers, I pulled the grommet in the trunk/fender near the battery, cut a small slit in it, and ran the power out there. I then ran the power across in the rear bumper/valance to the other muffler. The harness attaches to the mufflers "in series" so you won't have enough wire to go out to the left muffler, then go back inside, cross in the trunk, and go back out for the right muffler like I wanted to. I zip tied everything up tight and out of sight.

2. Yeah, I don't know why they say that, they are slip fit. Good thing too, because it took me a few tries to get the tips level.
Gotcha. I don't use the arm rest outlet, so I might just leave it there for awhile. I did notice that it says not to hard wire it, and it will void the warranty, but that's directed at constant 12v source. I'd like to think wiring to a switched source would allow you to retain the warranty.

Cool

2009 PBM GT
Under the Knife Again
Wiseco Pistons, K1 Rods, Johnson Lifters, BLP Keep Hatin' PDS Cam, Roto-Fab, BLP Ported Intake and Throttle Body, Kooks 1-7/8 long tubes, XForce Varex Catback, ZL1 Converter, Camaro Trans Pan/Filter, GXP Brembos
Breyton GTS-AV Wheels, 6k HIDs, Holden Steering Wheel and Paddle Shifters, Eibach Springs, 35% Tint
Tuned by Day Tuning
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