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Discussion Starter #1
I was wondering if anyone had heard or driven a G8 with the Solo HFCs but no other exhaust modifications (i.e. HFCs bolted up to the stock exhaust). Any idea what it would sound like? Would there still be a power increase? I was just curious.
 

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they are suppose to work without a tune. it would probably sound very similar to stock because you are still running the stock GT mufflers (MAYBE a TAD bit increase in sound). it will be an increase in power i would imagine, but you would want to get a tune to maximize it's full potential. otherwise, IMO, it would be a waste to get the HFC's installed.
 

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So the lower restriction from just the HFCs won't have a significant effect on its own, without a tune? I thought I read in other posts that a 10-20 hp increase with the HFCs was available, right out of the box. But yes, I have heard that a tune is required to make the most of them.
 

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So the lower restriction from just the HFCs won't have a significant effect on its own, without a tune? I thought I read in other posts that a 10-20 hp increase with the HFCs was available, right out of the box. But yes, I have heard that a tune is required to make the most of them.
With a matching performance aftermarket exhaust you can see those numbers when you add HFC's.

Tunes make it even better.

If you're modifying your car in such a way, "adjusting the recipe" to make it run the most efficient is probably a good investment as well, but not everyone shares that viewpoint. Oh well.
 

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Hey Zep, always good to hear from you! I am asking on behalf of my brother, who wants a bit more power and sound but not quite as much as the Mach Balanced gives. I mentioned the V2 system, but of course I haven't really heard it to tell. He's not interested in a tune.
 

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For our HF cats, no tune is needed. A tune will maximize benefits, but again is not necessary. With the stock exhaust, you will only see about a 10% increase in volume because of the oversized OEM mufflers. The exhaust note might get a touch deeper as well. You will see some added power out of the box, but not what it would be with an aftermarket exhaust and/or tune. I would say your gains on a stock exhaust will be around 15+whp. I hope this is helpful.
 

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So the lower restriction from just the HFCs won't have a significant effect on its own, without a tune? I thought I read in other posts that a 10-20 hp increase with the HFCs was available, right out of the box. But yes, I have heard that a tune is required to make the most of them.

I have had that exact combo and now have solo cats stock midpipe and gxp axlebacks. The solo cats with no other mods on a stock exhaust system will be quiet. In fact you would be hard pressed to tell the differance between stock and solo cats only unless they were right next to each other. The stock system with solo cats and gxp axlebacks in my opinion would be the best choice for you. It's about halfway inbetween a solo mach balanced and stock with a similar sound just quieter. I would say though that with that system you will Hear more unwanted sounds at certain speeds in 4 cylinder mode. Not bad but you will hear it more.
 

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Discussion Starter #8
Thanks for the info, that's good to know! Any "seat of the pants" performance enhancement?
 

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Thanks for the info, that's good to know! Any "seat of the pants" performance enhancement?
Probably not as much, again, because he's against a tune. Just getting HFC's and no other mods planned (tune, catback, etc) is like making a peanut butter and jelly sandwich with just bread. Yea, it's possible. But worth it?

Not in my book, but it depends on the person. HFC's are a big investment, I for one like to maximize my dollars invested and yes, most definately, with other supporting mods, HFC's are a night and day difference in "seat of your pants" dyno. Totally true.

Just HFC's ? Probably not.
 

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Discussion Starter #12
No worries, thekalman, I'll even hijack my own thread: Steve, because our cars are all too young to have been regularly subjected to the DriveClean program, do you know if any G8s have gone through it with the HFCs?
 

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Al this Canadian speak is making me want to contribute an evoquivical "eh". Lol

No emissions problems here in NYS... which is said to be pretty close to California in standards.
 

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I have had that exact combo and now have solo cats stock midpipe and gxp axlebacks. The solo cats with no other mods on a stock exhaust system will be quiet. In fact you would be hard pressed to tell the differance between stock and solo cats only unless they were right next to each other. The stock system with solo cats and gxp axlebacks in my opinion would be the best choice for you. It's about halfway inbetween a solo mach balanced and stock with a similar sound just quieter. I would say though that with that system you will Hear more unwanted sounds at certain speeds in 4 cylinder mode. Not bad but you will hear it more.
Going to resurrect this one a bit because I just did this same thing yesterday (installed the Solo HFCs with the stock GXP midpipe and axelbacks). I didn't really want much/any change in volume and this set-up delivered on that end. Spider is right - you'd be hard pressed to tell the difference between this and stock. However, I do get some drone right around 2k rpms. Spider - do you get the same drone/resonance?

And a question for anyone, without adding a Solo catback (I don't want the sound increase), is there any way to kill the drone? Dynamat in spare tire well? Solo axleback? J-pipes on the stock axleback?
 

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No worries, thekalman, I'll even hijack my own thread: Steve, because our cars are all too young to have been regularly subjected to the DriveClean program, do you know if any G8s have gone through it with the HFCs?
I am not sure about that program, but as of yet, we have had no emissions issues. The internal substrate is chemically coated to further enhance their ability to dissipate harmful gases.

Going to resurrect this one a bit because I just did this same thing yesterday (installed the Solo HFCs with the stock GXP midpipe and axelbacks). I didn't really want much/any change in volume and this set-up delivered on that end. Spider is right - you'd be hard pressed to tell the difference between this and stock. However, I do get some drone right around 2k rpms. Spider - do you get the same drone/resonance?

And a question for anyone, without adding a Solo catback (I don't want the sound increase), is there any way to kill the drone? Dynamat in spare tire well? Solo axleback? J-pipes on the stock axleback?
In order to prevent drone, especially on the G8, you will need J pipes. That is why all of our kits have J pipes on them. As big as the stock muffler is, it is still not a drone killer when using HF cats. This is why the J pipe technology is so great! Dynomat won't stop drone...it may reduce noise in the interior, but the deepness will be there.
 

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In order to prevent drone, especially on the G8, you will need J pipes. That is why all of our kits have J pipes on them. As big as the stock muffler is, it is still not a drone killer when using HF cats. This is why the J pipe technology is so great! Dynomat won't stop drone...it may reduce noise in the interior, but the deepness will be there.
Ok, so would your axlebacks kill the drone? Also, what would be my quietest option now?

1 - Solo HFC's and axlebacks

2 - Solo HFC's and some version of a Solo catback

Thanks for the reply (on a Sunday, no less).
 

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i would say the best bet would be their axlebacks and HFC's. and yes, as long as you have the j-pipes, you will have no drone. also, solo makes the V2 kit, i believe, which is their quietest catback option...but comes at a much higher price compared to just axlebacks. not sure how the V2 vs. axleback sound compares on the loudness scale, maybe steve could chime in..
 

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The axle back is more raw sounding than all of our kits...the kits are more refined. The difference between the Mach Balanced and V2 with J is not that huge. The V2 with J is the quietest. The axle back is more similar to a Mach in terms of volume, maybe even a Mach Shorty...just not as refined.
 

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Discussion Starter #19
i would say the best bet would be their axlebacks and HFC's. and yes, as long as you have the j-pipes, you will have no drone.
I don't know if that's exactly true: even after having Solo measure and adjust my J's, there's a drone (a resonance) at about 70 km/h that can get quite beastly under load (with all 8 cylinders in). It's beatifully quiet on the highway, though.

Solo can correct me if I'm wrong, but I'm of the impression that you can either tune for quiet at highway speeds or quiet at city speeds, but trying to tune out resonances across the whole RPM range is not really viable (discounting four cylinder mode). Is that true, or do I have some more adjusting to do?
 

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Turbo301 said:
I don't know if that's exactly true: even after having Solo measure and adjust my J's, there's a drone (a resonance) at about 70 km/h that can get quite beastly under load (with all 8 cylinders in). It's beatifully quiet on the highway, though.

Solo can correct me if I'm wrong, but I'm of the impression that you can either tune for quiet at highway speeds or quiet at city speeds, but trying to tune out resonances across the whole RPM range is not really viable (discounting four cylinder mode). Is that true, or do I have some more adjusting to do?
70km/h = 40mph? 6th gear, 1100rpm? This is actually the engine "lugging", and more a product of the car should NOT be in such a tall gear at that speed. If you flop over to manual mode 5th gear, the sound goes away, right?

The SOLO J-pipes target the natural L76 resonance in v8 mode of drone at 72mph (probably 110km/sec, highway speeds) where the real drone at this speed, on my exact test-car was headache inducing and


If you had a custom tune on there, you could request that they tweak the TCM tune to allow for the 70km/sec (or 40mph) to NOT lock up the torque converter .... which would avoid that spot altogether, and your lugging issue would be solved, solo exhaust system independant.


Ya see, the J-pipes are a certain length to target a corresponding certain frequency.

Take off the J-pipes altogether and cap the "branches" where the J-pipes were. Then take it up on the highway and you'll see what drone really is. That's what the J-pipes target.

If you're not willing to custom tune it to avoid the "fuel economy numbers mandated 40mph/70kmsec 6th gear idiotry that comes with the factory program on these cars.... then grab a laptop with a freeware sound collecting program and measure the hertz of the drone at your speed, and tune your J-pipes to that. Sure, possibly you will re-introduce the 70mph/110kmsec drone by adjusting this, but if you do most of your driving at 70km/sec then you can effectively tune out THAT FREQUENCY instead.

For me, my tuner made 40mph or 70km/sec to be 5th gear by default.... and I do not share the same issue you complain about. Likewise, my car at highway speeds is near stock quiet in v8 mode which is how I run all the time. I have a mach unbalanced with J's, along with HFC's and Kooks LT's, and it's the best of both worlds -- I love it.

Try it and report back. I personally had just about forgotten about the 40mph lug THAT SOME CARS have a problem with... mine was not an issue.

Not all g8's react to teh same mods identically... keep that in mind too.

--zep
 
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