miami1lt

All,

Wanted to write a quick review of the GT PRO Double X (Secondary and Resonator replaced with X-pipes).

First, Brian at GT PRO was VERY easy to deal with...had some unplanned wait time while my front pipe was being "built". All-in-all, a VERY smooth transaction, and about 21 days from order to receipt.

Second, the install was intuitive, and the directions were great. I took it to a local peformance shop; one that VERY rarely does an exhaust but does GREAT quality work--the reason I trust them. Total install time was about 20 minutes, and most of that was measuring...the cuts (2 of them) took a total of 1 minute each..

Third, the quality was GREAT! Dave, my mechanic at Ron's Performance here in HI could NOT get over how great the fit was, how easy the directions were, and how beautiful the product was. This is a direct quote (in Hawaiian of course, even though he's as white as a ghost), "Brah, this is some of the best aftermarket stuff i've ever seen...you DEFINITELY got good stuff, and please tell GT PRO I said that!". He has heard of GT PRO before, but never seen a product...he himself will order from GT PRO he said after what he just installed. They couldn't believe the pipes weren't just bent, that the pieces were bent but welded to fit...they estimated there were 40-50 pieces welded together to perfection!

Results: Well, no dynos yet, but very responsive for sure. You can definitely feel the mid-range power as it races through the range. The SOUND...the SOUND is incredible...As soon as it came down off the rack, Dave asked me to start so he could put it up and check for leaks. He said to give it a little, so I pumped it a few times...I heard tools dropping all around the garage so that people could come see. Dave's first words (once he raised his bottom jaw back up) were, "That is Formula-1 sounding, Brah". And he is right. It sounds like something you'd see driving from Venice to Rome at 200mph. When I took off to go get him some cash, I hammered it good (about 1/8-1/4 mile away from the shop where the entrance is). When I got back and pulled up, he said, "Dude, I heard you spank it leaving here...that was AWESOME". They asked for a few more revs before I pulled back out.

Video (Before): http://www.youtube.com/watch?v=QZIYQqnUI0k

Video (After): http://www.youtube.com/watch?v=8_Nrzo85FbA

Like others have said, do NOT let the videos fool you...this sounds WAY better in person. It is truely the best mod (to include the extra horses from my ECU reflash). When I pulled into the driveway and pumped it, my wife said, "Oh, baby!!!". By the way, she had no idea what i took it in for today, but said right away, "That sounds WAY better than when you left".

AWESOME...thanks Brian for the new thrills!

BerBer63

Nice write-up, congrats and can't wait for your dyno

HIRO63

I have this product also and I really think that GT Pro product is great! I love the sound and like you said mid range power is different. Plus Brian is great guy to deal with. I think that this product is one of best tune I did also.

Your car sounds nice also!

superlubricity

Awesome! Can't wait to see the dynos!

miami1lt

Thanks for the comments guys. Yeah, I've seen a few single x-pipes, but I really think the x-pipe that deletes the resonator really opens it up (from a sound perspective only)...and there is no drone at all. I cruised at 70mph on the way home (from 4th through 7th gears, and it was perfect).

Also, threw down a few 60-100mph times, and the best I pulled was 5.2s...that isn't much different that before the tune (normally was between 5.3-5.6). So hard to tell if that was much of a gain or just a better run.

I'm hoping to dyno next weekend. I hate the dyno shop I go to (left a pair of wire-cutters in the engine bay the last time), but not much choice or use switching...only dyno-paks around, and I don't like those!

obsidian05e55

Sounds great! One thing though. In the "after" video you can see the mufflers aren't adjusted correctly. The tips are touching the diffuser. Might wanna have them readjust the hangers

ZephyrAMG

+1. Great sound...awesome growl. Now just don't start burning diffuser plastic and having black smoke trail you...

C63newdude

I would love to have a double XX but the fact that you have to cut the pipes turns me down. My main issue is that my local dealer don't want me to mod it at all.

miami1lt

Yeah, it is a LITTLE closer, but really, the pipes are out a tad further too.

After you said something, I went out and checked...I have about 3/8" between the pipe and diffuser. Not sure what it was before, but probably 3/4".

I don't think it will burn up the diffuser, but I'll keep an eye on it...thanks for the heads up.

Freshly

I am not sure what makes a "good" X-Pipe. I am thinking about buying his 1 month old X-Pipe that was installed on his 72 SS El Camino. It was professionally built in a local muffler shop. The X-pipe itself is 2-1/4 inches in diameter. When I tried to look up the specs for the OEM E500 exhaust Diameter to make sure it will fit, I found inconsistant numbers. Some said it was 3in some said it was 2.36in (60mm x 2mm). I need some help to try and figure this out. Thanks,
here are links to the pics. Im not really sure why I cant repost pics:

https://mbworld.org/forums/w211-amg/...on-x-pipe.html

https://mbworld.org/forums/w211-amg/...on-x-pipe.html

https://mbworld.org/forums/w211-amg/...on-x-pipe.html

https://mbworld.org/forums/w211-amg/...on-x-pipe.html

olszowa12

Sounds really mean

miami1lt

First, the cuts have sleeves that can go back over if you decide to return to stock...sounds bad, I know, but it really could go back to stock in no time...and not even the stealership would know (unless they looked at that 2" section.

Second, the stealership can't say anything about modding unless they can prove it caused a problem. Opening up airflow in the exhaust does nothing but good things for the car (lessens back pressure for example). The only issue with the x-pipes is for emissions. If somebody knows their ****, they will know there should be add'l cats there...but most people don't know much about a Chevy let alone a MB. And it wont' trip a CEL, so you are good there.

It is probably the best mod for the car as far as not doing anything but opening up airways and making it run smoother...Fuel economy should rise as well (not much, but expect 1mpg). I've noticed a much better throttle response....you could hear in the vids the real quick bursts...you can't do that stock, as it takes too long for the RPMs to come back down to do that.

Even Money

I don't think emissions are much of an issue with the newer cars, unless the guy is actually looking for cats. Otherwise, I think they just plug into the car, and the car tells them if it passes emissions or not. So, if you delete the pri cats, just get a tune to deal with it, and the car won't know the diff.

Even Money

Is the double x pipe overkill? Would a single x(sec cat delete) and straight thru, vibrant type resonators(stock resonator delete) be as good/better?

bluejae

i've been thinking along the same lines as even money.

@miami1lt - you don't have long tubes right? or any headers?

i've been on the fence with what mod to do next. i thought about putting straight pipes in place of the 2nd cats, and leave the resonators and primary cats... but then if i ever plan on getting headers, that would likely get rid of my primary cats... if what i read from the posts above, as long as i have a tune, it shouldn't be a problem with not having any cats?

if that's true, then i can just plan on getting longtubes which will delete the primary cats, and then some option to take care of the 2nd cats and either x pipe the resonator or leave them be so the sound isn't too crazy...

bluejae

and i guess gt pro didn't fool you

miami1lt

@even money: Good point on emiissions...technically here (HI), they are supposed to put the car up and check the underworks...if they knew that there were supposed to be 2 secondary cats that were gone, they could fail me. I think anybody who does this regularly will think it is strange to see a long exhaust w/ 2 x's in it...but who knows.

also, can't comment on overkill or not. All I can tell you is I won't even drive in S mode now...its only manual so I can get the RPMs up over 2K in every gear...it just sounds like a ferarri now. I actually had a guy in a Cobra roll down his window yesterday, I punched it in first (from a roll) and then slowed down...he pulled up next to me revving a bit, and then said, "Your car sounds awesome"...coming from a Cobra guy, that is a good compliment (since I think they have the best stock exhausts out there).

@bluejae: No LTs or headers. What you hear is straight up X-pipe. I was thinking of LTs some day for the extra horses, but to be honest, the power isn't doing much for me. I can't hook up well anyway, so I prefer just ripping it from like 20-30mph...and besides, sounds like the LTs w/ pri cat delete is VERY loud. This is perfect right now. If you do go LTs, you do need the ECU updated so the pri cat O2 sensors don't pop. I looked at them yesterday, and there isn't a way around that.

I wish you could hear it in person....you'd be sold in a heartbeat. You know how the C63 is loud enough to get some looks? Now I see heads turning all over because people think it's an exotic. To me, it actually gives the car more street cred, as it isn't just a deep thunderous bellow, its now a not-as-deep but more perfect sounding note. That "stutter" in the stock exhaust is gone.

The best way to describe it is it sounds like a Hayabusa on steroids! Sounds VERY high revving and smooth now!

Sincity

I have used Vibrant resonators and think they are a great product. I originally thought a 12" long Vibrant may work, but looking at the secondary cats, the Vibrants are a tad wider and may not fit. If you are going to swap out the stock resonator for a Vibrant, you are wasting your money. The stock resonator is a straight-thru unit with a small H-pipe tying in both exhaust banks.

Brian GT PRO

The Double XX was tuned to a certain freq. and db level based on my personal taste, I hoped that others would be on the same page as I and would like it. I truly do the best I can to build a product that owners would be proud to install, and shops would look at and give us credit and potential business. I know that if I get a good part well engineered, easy to install and works right, I usually end up doing more business with that company, on the other hand if I get a crappy/sub par product, that's the first and last time we speak (just like the crap carbon diffuser we just got/sent back on behalf of JoeMoney) I approach everything that I build from the enthusiast perspective, because at heart that is what I am, I am one of you. If I buy something, I have very high expectations, therefore I expect that my customers expect this of me. Is my stuff the cheapest out there? most likely not, you can go to a muffler shop and do straight pipes and weld them etc., but that's not something I would do to my own car, so that's why I developed these parts. I had a design goal, in terms of exhaust note, db level and craftsmanship that I would accept on my own car, so this is the end result.

Anyhow, I'm glad MiamiLT1 is happy, it really brings joy to my day when someone can appreciate the workmanship, care and thought I put into these parts.

Even Money

So do you feel this design makes the most power with a reasonable exhaust note?

Brian GT PRO

Honestly, I think this is the "perfect" balance for the C63. I have LT's on my car right now, and honestly it's a bit loud for me, and my neighbors are not too keen on it, however it is kind of funny to scare ppl with a quick rev LOL. Power wise the LT's make a ton more power, BUT there is a trade off, the LT's don't sound as "nice and polished" like the Double XX.

Even Money

Thanks...Does your LT setup delete the sec cats, i.e., if you have the LTs can you also have the XX?

Brian GT PRO

The LT's remove the secondary cats , we plug right into the factory resonator. We can also plug into the Single X R-1 which is the resonator removal X. We are considering a design change to allow for Double XX, but it's one of the many things on the list "to do"

superlubricity

. . . on the list after you make the primary deletes for your Single X customers.

Even Money

yeah...'cause I'd like to compare those dyno results to LTs..