Preface:
The reason I went with the X-Pipe wasn't to gain a lot of power. I've said it before; the big bottle neck on the stock exhaust system is the restrictive primary cats. I really want a vendor/fabricator to make a resonator-to-manifold bolt-in solution for replacing all cats, but nobody has stepped up yet. I even tried to have something fabricated locally, but couldn't find anyone willing to take on the task without it becoming a $1K+ project. I figured the GT PRO Single X-Pipe provides me with a head-start for what I'm looking for as it already bolts directly up to the resonator. It is a solid foundation for the eventual primary cat delete downpipes I want. Heck, maybe I can even convince Brian to make me the downpipes. C'mon Brian!

Product:
It shipped fast from GT PRO and came well packaged. The quality of the welds and craftsmanship of the pipe was very good. High-quality clamps and detailed instructions are also included. The instructions were spot-on and include some great photos. Note: I picked up my own pipe cutting tool but ultimately needed to use a reciprocating saw to complete the "cut the factory exhaust here" step.

Sound:
Thankfully, not as loud as I feared. The growl is enhanced and it's actually quite nice. When cruising it is very tame and you hardly notice a difference until you start to accelerate. At WOT it sounds fantastic and it doesn't lose any of the C63 character. There is no hint of obnoxiousness. Cold start (only one so far) is a bit more brash, but tolerable. We'll see if that changes tomorrow morning.

Weight:
The stock pipe with secondary cats is 18.5 lbs. The GT PRO Single X-Pipe is 7.5 lbs. That is a savings of 11 lbs. Not too shabby.

OK, on to the dyno stuff . . .

My Car:
2010 C63 AMG w/ 3,052 Miles running 92 Octane (Shell) w/o charcoal filters
+ Kleemann K1 ECU Tune
+ PLM Exhaust Manifolds

Conditions:
Temp: 55-70 Degrees F
Barometer: 29.93 in-Hg
Humidity:20-40%
Elevation: 200-ft

Dyno:
Dynojet Model 424xLC2
All pulls (before and after) done in 5th gear w/ SAE Correction Factor & Smoothing 5.

Results:
GT PRO Single X Pipe (After Pulls):
03/20/10 = 439.35 RWHP / 401.21 RWTQ
03/20/10 = 437.68 RWHP / 402.00 RWTQ
03/20/10 = 437.57 RWHP / 400.53 RWTQ

Stock Secondary Cats/Mid Pipe (Before Pulls):
03/20/10 = 435.56 RWHP / 398.13 RWTQ
03/05/10 = 435.60 RWHP / 398.86 RWTQ
03/05/10 = 435.21 RWHP / 398.37 RWTQ

Gains:
Power / Torque vs. Same Day Baseline
+3.79 RWHP / +3.08 RWTQ (Peak)
+8.61 RWHP / +12.76 RWTQ @ 3500 RPM

Conclusion:
If you want a bit more growl out of your factory exhaust, this is a really nice modification. The extra power/torque in the bottom end and the weight savings are nice bonuses. I highly recommend this mod for the sound alone.

Graph/photos below. I hope this was helpful.

Best before and best after dyno pulls:


Side by side photo:


Stock plumbing:


Single X:


Single X:


The primary cats and downpipes beggin' to be replaced.


Single X:


OEM Pipe

 

No cutting required?

 

Great post and detailed explanation thanks. Did you do it yourself or did you take it to a shop? How long did it take to do?

Any sound clips of before and after? Also, do you need any sealer/goop on the joints? Or do the clamps seal them well - especially the new clamp?

 

One cut required. It should be very easy to do with the right chain pipe cutting tool. My cutting tool sucked.

 

Had my shop do the install. I supervised.

It took less than an hour with the car on a lift. It would have been faster if the cutting tool worked correctly.

No audio clips, No sealer/goop required, No leaks.

 

Awesome info, thanks for the leg work! Much appreciated!
Brian, someone, anyone, let's get the missing manifold to xpipe (or straightpipe)
piece completed so we can make some real power at a decent price!

 

Thank you and I agree 100%.

 

Yet another fantastic writeup, thx!

 

Thanks

 

so it looks like the piping diameter is the same so the only difference is the X?

 

Yup, the only real difference is the secondary cats are replaced with an X.

Both stock pipe and x-pipe are 2.5" stainless.

 

Great review. I like the breakdowns and thoroughness...you should be getting paid by these companies to do this stuff...if I was Cory from Kleemann or Brian from GT PRO, I would hire you to write reviews of products...anyway, i'll let their marketing departments deal with that

I get mine in a week or so...I only have the K1, so I'm hoping to get a few more HP out of it since I don't have my manifolds modded like you. But sounds like I should temper my power/tq expectations, and focus on the sound.

I noticed you didn't use the word exotic...thanks...not sure what that means outside of the bedroom anyway. But if you could use one word to describe the sound now, what would it be?

 

Great job, super!

 

Superlubricity, awesome write-up as usual! I hope Brian or another tuner may consider this:

1) Downpipe with 200 cell primary cats, x-pipe, to stock exhaust.

or

2) Downpipe with 200 cell primary and secondary cats to stock exhaust.

or

3) Downpipe with 200 cell primary cat, stainless steel perforated core resonator, to stock exhaust.

Understand that it will not produce the high HP/TQ as a LT header, but the labor cost/time will also be significantly less if we retain the stock exhaust manifold. I like Brian's concept of returning everything to stock with ease. He could make this as a modular system.

 

great job and nice power gain for the mods you have. if you dont mine how much have you spent on you current mods. and why no air filters like K&n or BMC or the ROW airbox?

verynice write up btw.

 

Thanks, lol.
Exotic is a good word. I'm still getting to know the new "tone". After I've had some more seat time, I'll give a better sound summary.

When the weather gets better (damn PNW rain ) I'll talk the G/F into taking some HD video.

 

Thanks. Finally over 400 RWTQ.

The evosport pulley goes on next week.

This would be awesome. Don't forget about the catless downpipe option. I've asked vendors in the past to help produce something just like this. It looks the the community is interested. Together we should be able to get the ball rolling! I'm really hoping Brian jumps in.

Thanks.

RE: Air Filters.

I've tested back to back with BMCs. avengerboater has tested back to back with K&Ns. There is no measurable power to be found.

RE: ROW Airboxes.

I've also played with these on the dyno. I have yet to be able to "prove" they make consistent power over stock airboxes without charcoals. I'll be testing more in the future. There might be a couple HP up top, but nothing I could demonstrate on back to back runs. If I get some concrete and repeatable data (good or bad) I'll be posting it.

RE: Amount Spent.

MSRP for the Kleemann K1 ECU Tune = $1495
MSRP for the GT PRO Single X-Pipe w/ Pipe Cutting Tool = $695
MSRP for the PLM Exhaust Manifolds w/ Gaskets = $1995

Note: I was able to get the PLM Manifolds for much, much, much lower than their MSRP. I'm pretty sure I was their first C63 customer. I quoted my price in the PLM dyno results thread as "ridiculous" and it was.

Besides, most of my $ have been spent on dyno pulls. 51 runs and counting. I'm slightly obsessed.

I'll be re-focusing that energy at the track once season opens.

 

This shows the 2nd cats flow pretty well, it's the exhaust manifolds and primaries where the powers at.

 

has anyone dynoed with straight pipes in place of their cats?

 

Last time i checked they said the gains in the midrange are 25 RWHP???
I don't even see 10whp.

 

Superlubricity - any drone with the X-pipe at all?

 

Great review...sounds good, but not exactly the +15-25WHP/TQ that GT PRO advertises for their X-pipe; like I've said before similar or higher gains can be had with a good set of ss/metal substrate $120 high-flow cats. But, congrats on a nicer sound and glad you like it!

 

That is right....it was you that said it in the past. I was trying to remember who told me this.

 

I'd like to give that undercarriage a how's your father!

 

U know that for $3500 u could of just had a ecu tune and made the same amount of power that u making with all u mods.