GMG WC-GT Headers - Impressions
03-18-2012, 08:48 AM
#1
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GMG WC-GT Headers - Impressions
It's been a month since I've had the GMG headers on my '11 GT3RS. Now that the setup's clocked a bunch of street miles and track time, it's time to reflect on my impressions.
First things first: the Order Process. I'm currently located outside the country. Getting GMG to ship internationally hasn't been easy. That, combined with an untimely shortage of cats from HJC in Germany, led to a five-week-delay between order confirmation and the headers shipping out. It was hardly a smooth experience, but to James/Fabryce's credit, they got on the case and righted the situation as soon as I raised the issue with them. I reckon it's GMG's style to be economical with words, but they were professional through and through and true problem-solvers. In the end they delivered, and that's what mattered most
My skepticism proved unfounded when the shipment finally arrived mid-February. The contents were very well-packaged--foam on either ends, bubble wrap all around. They unpacked to reveal a beautifully welded pair of pipes. I have spent much time around exhausts, from "reasonably priced" Millteks, Supersprints and FVDs to the likes of Larinis, Tubis and Akras. GMG's product construction is superb--the consistency of the bends, the evenness of the welds--they're leagues above what I'd expect in this price range.
The Packaging:
Closeup of one of the Downpipes+Welds:
200-Cell Cats from HJS--Good Stuff!:
Installation: the headers snapped-on to the OEM side mufflers without drama. For peace of mind I also installed a new set of header gaskets. Everything else was straightforward--incl. the O2 sensors which connected without any codes. I chose to keep the Sharky center bypass--love the OEM Ti tips and couldn't be motivated to part with Sharky absent a real good reason...
Sound: These things are LOUD. Granted I already have a center bypass, the new "normal" (i.e. non-sport mode) idle is as loud as the old idle in sport mode. At full chat the sound is bat$hit insane. Explosive. Sharp. And did I say LOUD?? In my book this setup is borderline acceptable for street use but definitely not for the faint of heart. At 5k+ rpm the exhaust resembles the report of a minigun. Seriously. I literally went "WHOA" in my first windows-down tunnel run. The chatter's not as "poppy" as a cup car, but it's close... (FWIW there's no droning inside the cabin, unlike a few other setups I've experienced in 3.6 & 3.8 cars)
Performance: after giving time for the ECU to adapt, I thought the car exhibited better high-end pull. No noticeable loss of low-end torque or engine shudder at idle (definitely an issue with the Akra race setup based on first hand experience). I thought all that could be just placebo, so I waited until I had more hard data from my hometrack...
This is the main straight at Zhuhai International Circuit. Recorded last Fall when I still had the OEM headers. Car was running a fresh set of R6s. Traffic was clean (it was a sanctioned time-attack lap). Notice the apex speed of 125km/h coming out of T14 and Vmax of 209kmh on the main straight
Fast forward to this month. The same set of R6s (with 18+ heat cycles since the last dataset) that was evidently about to give (over the past 3 DEs I've rotated and then flipped those things on the rims like a professional cheapskate...
). Car had also been laden with heavier iron brakes (vs. PCCBs for 14lbs' difference--unsprung--per corner). The only good thing going for me were the GMG headers.
Not surprisingly, the new data showed lower apex speeds--nearly 10km/h slower, at ~116. And yet I consistently reached VMax's 15km/h higher in the 222-224 range... overall laptimes were right on top of my old ones, albeit with worse handling (cheapskate scrubs+lesser brakes) and less-than-ideal traffic. I'd hazard to guess that I've gained a second on this 1:48-1:52 track...
Power delivery: Needless to say I'm happy with the performance gains. However I felt there's this "hole" in the torque curve between 5.5 and 6.5krpms. It's small (lasts for maybe a split of a second at max as I went through the powerband), but definitely noticeable when I focused on how the car's pulling. I've been able to reproduce this "hole" from time to time, around the same spot in the tachometer...
Net net I'm happy with the purchase. GMG has built a great product and I'm happy to recommend it to those looking for quantifiable performance gains (or much louder sounds...
)
First things first: the Order Process. I'm currently located outside the country. Getting GMG to ship internationally hasn't been easy. That, combined with an untimely shortage of cats from HJC in Germany, led to a five-week-delay between order confirmation and the headers shipping out. It was hardly a smooth experience, but to James/Fabryce's credit, they got on the case and righted the situation as soon as I raised the issue with them. I reckon it's GMG's style to be economical with words, but they were professional through and through and true problem-solvers. In the end they delivered, and that's what mattered most
My skepticism proved unfounded when the shipment finally arrived mid-February. The contents were very well-packaged--foam on either ends, bubble wrap all around. They unpacked to reveal a beautifully welded pair of pipes. I have spent much time around exhausts, from "reasonably priced" Millteks, Supersprints and FVDs to the likes of Larinis, Tubis and Akras. GMG's product construction is superb--the consistency of the bends, the evenness of the welds--they're leagues above what I'd expect in this price range.
The Packaging:
Closeup of one of the Downpipes+Welds:
200-Cell Cats from HJS--Good Stuff!:
Installation: the headers snapped-on to the OEM side mufflers without drama. For peace of mind I also installed a new set of header gaskets. Everything else was straightforward--incl. the O2 sensors which connected without any codes. I chose to keep the Sharky center bypass--love the OEM Ti tips and couldn't be motivated to part with Sharky absent a real good reason...
Sound: These things are LOUD. Granted I already have a center bypass, the new "normal" (i.e. non-sport mode) idle is as loud as the old idle in sport mode. At full chat the sound is bat$hit insane. Explosive. Sharp. And did I say LOUD?? In my book this setup is borderline acceptable for street use but definitely not for the faint of heart. At 5k+ rpm the exhaust resembles the report of a minigun. Seriously. I literally went "WHOA" in my first windows-down tunnel run. The chatter's not as "poppy" as a cup car, but it's close... (FWIW there's no droning inside the cabin, unlike a few other setups I've experienced in 3.6 & 3.8 cars)
Performance: after giving time for the ECU to adapt, I thought the car exhibited better high-end pull. No noticeable loss of low-end torque or engine shudder at idle (definitely an issue with the Akra race setup based on first hand experience). I thought all that could be just placebo, so I waited until I had more hard data from my hometrack...
This is the main straight at Zhuhai International Circuit. Recorded last Fall when I still had the OEM headers. Car was running a fresh set of R6s. Traffic was clean (it was a sanctioned time-attack lap). Notice the apex speed of 125km/h coming out of T14 and Vmax of 209kmh on the main straight
Fast forward to this month. The same set of R6s (with 18+ heat cycles since the last dataset) that was evidently about to give (over the past 3 DEs I've rotated and then flipped those things on the rims like a professional cheapskate...
). Car had also been laden with heavier iron brakes (vs. PCCBs for 14lbs' difference--unsprung--per corner). The only good thing going for me were the GMG headers. Not surprisingly, the new data showed lower apex speeds--nearly 10km/h slower, at ~116. And yet I consistently reached VMax's 15km/h higher in the 222-224 range... overall laptimes were right on top of my old ones, albeit with worse handling (cheapskate scrubs+lesser brakes) and less-than-ideal traffic. I'd hazard to guess that I've gained a second on this 1:48-1:52 track...
Power delivery: Needless to say I'm happy with the performance gains. However I felt there's this "hole" in the torque curve between 5.5 and 6.5krpms. It's small (lasts for maybe a split of a second at max as I went through the powerband), but definitely noticeable when I focused on how the car's pulling. I've been able to reproduce this "hole" from time to time, around the same spot in the tachometer...
Net net I'm happy with the purchase. GMG has built a great product and I'm happy to recommend it to those looking for quantifiable performance gains (or much louder sounds...
)
Last edited by CRex; 03-18-2012 at 11:18 AM.
03-18-2012, 11:05 AM
#6
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They're about 3 pounds heavier per side, according to my mechanic. I don't have the numbers to confirm that tho 
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03-18-2012, 11:37 AM
#8
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Akra sounds more "composed" whereas the GMG setup is best described as "butch". The Akra's built to look like artwork--and comes with a price tag reflecting the same. One big downside: the Akra race setup I tested droned real bad. That's a non-starter for me...
03-18-2012, 12:05 PM
#9
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I really like exhaust posts.
Interesting topic, Nice to hear about your experiences. Thanks for posting this...
Do you find the car with AKRO race was much lighter without the side mufflers? Did you notice the difference in weight between the akroRACE/OEM/GMGSETUP while on track ?
dropping pccb to steels and changing exhaust would have been a substantial difference in weight added to the car.
-adding side mufflers(19.8x 2=39.6lbs) + gmg headers (18.1x2=36.2lbs)
TO recap, You are now running OEM side mufflers(39.6lbs) with the 200cell gmg headers (36.2lbs) + sharky center muffler (need weight) + OEM TIPS (3.3lbs)
-Weights-
OEM NUMBERS (total 84.7lbs stock)
headers 5.5kg or 12.1lbs each
side mufflers 9kg or 19.8lbs each
center 8kg or 17.6lbs
tips 1.5kg or 3.3lbs
GMG header oem + 6lbs (as given above) = 18.1lbs each header
AKRO RACE weights? suppose to drop 46lbs off the car 84.7lbs - 46lbs = 38.7lbs ?
Sharkweks site : Real 16 pound weight savings (stock muffler weighs 17.6lbs pounds total) from the rear of the car (6 pounds savings over 2010+ titanium center section) oem 17.6lbs - 6 = 11.6lbs
as per this post ---> https://rennlist.com/forums/997-gt2-...r-weights.html
Interesting topic, Nice to hear about your experiences. Thanks for posting this...Do you find the car with AKRO race was much lighter without the side mufflers? Did you notice the difference in weight between the akroRACE/OEM/GMGSETUP while on track ?
dropping pccb to steels and changing exhaust would have been a substantial difference in weight added to the car.
-adding side mufflers(19.8x 2=39.6lbs) + gmg headers (18.1x2=36.2lbs)
TO recap, You are now running OEM side mufflers(39.6lbs) with the 200cell gmg headers (36.2lbs) + sharky center muffler (need weight) + OEM TIPS (3.3lbs)
-Weights-
OEM NUMBERS (total 84.7lbs stock)
headers 5.5kg or 12.1lbs each
side mufflers 9kg or 19.8lbs each
center 8kg or 17.6lbs
tips 1.5kg or 3.3lbs
GMG header oem + 6lbs (as given above) = 18.1lbs each header
AKRO RACE weights? suppose to drop 46lbs off the car 84.7lbs - 46lbs = 38.7lbs ?
Sharkweks site : Real 16 pound weight savings (stock muffler weighs 17.6lbs pounds total) from the rear of the car (6 pounds savings over 2010+ titanium center section) oem 17.6lbs - 6 = 11.6lbs
as per this post ---> https://rennlist.com/forums/997-gt2-...r-weights.html
Last edited by lopro; 03-18-2012 at 12:46 PM.
03-18-2012, 12:10 PM
#10
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Thanks. We are installing an Akrap. race setup in a few weeks, so just trying to get a baseline.
03-18-2012, 12:42 PM
#12
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Thread Starter
Did it feel lighter? Yes. But I reckon any handling benefits were to be found at the limit and I wasn't nearly there on public roads!I think the weights you posted are in the right zip code... the OEM side mufflers are 20 pounds apiece... For weight savings I'm increasingly tempted to do delete those anvils via elbow pipes like these and restoring the OEM Ti center muffler... but that's uncharted territory with unproven sound/performance characteristics...
03-18-2012, 01:32 PM
#13
We did 3 videos yesterday, comparing different exhaust set ups.
I have a new system with side muffler delete. Love it. No Drone, deeper tone than the side mufflers with stock center muffler.
Orbit will post the results probably tomorrow or Tuesday the latest.
I see no downside on the side muffler delete, if you track your car.
If it's your daily and you want the quietest, maybe, the stock is better, or also a different car would be quieter.
I have a new system with side muffler delete. Love it. No Drone, deeper tone than the side mufflers with stock center muffler.
Orbit will post the results probably tomorrow or Tuesday the latest.
I see no downside on the side muffler delete, if you track your car.
If it's your daily and you want the quietest, maybe, the stock is better, or also a different car would be quieter.
03-18-2012, 01:49 PM
#15
Orbit Racing side muffler delete, with their new German center muffler.
They will disclose more information this week, and a few more options will be available this week.
The side muffler is nothing new to them, that already use side muffler delete since 2007.
They will disclose more information this week, and a few more options will be available this week.
The side muffler is nothing new to them, that already use side muffler delete since 2007.