Guess you could say I have a bit of a thing for the GLC63's—I'm now on my third one and I admit I have issues with missing cars I've owned in the past My journey began with a 2018 GLC63s Coupe, followed by a 2020 GLC63 SUV, and now I’ve got a 2021 GLC63s. It feels incredible good to be back behind the wheel of a GLC63—I’ve truly missed it, oh and that sound! Boy it pains me to know there will not be another v8 in a suv this size from Mercedes again

Over the years, I’ve tested and tuned may of our cars, uncovering some interesting differences in the performance of stock versus tuned models. While many claim there’s no noticeable difference between the SUV, coupe, and or the non-S versions, I'm wondering if that is that really true?

My 2018 GLC63s was mostly stock, aside from lowering. Unfortunately, I didn’t have it long enough to do any major mods as it was involved in an accident. But I did manage to get some baseline Dragy numbers.

• 93 octane, 82 degrees 1800 da
  • 0–60: 3.75 seconds
  • 1/8 mile: 7.65 @ 92.21 mph
  • 1/4 mile: 11.89 @ 115.44 mph

Next came the 2020 GLC63. Completely stock, it ran the following: Big difference from none s models.

• 93 octane, 88°F, 1,800 DA
  • 0–60: 4.14 seconds
  • 1/8 mile: 7.65 @ 92.21 mph
  • 1/4 mile: 12.36 @ 110.72 mph

After tuning it with EC (CPC/TCU/ECU) and adding 1 gallon of E85 to a full tank of 93 its apparent how big of a difference the tuning makes for the no S models.

• 93 octane w/ 1g of E85 91°F, 2,332 DA
  • 1/4 mile: 11.31 @ 118.63 mph
  • 60–130: 11.31 seconds

Later, I partnered with a new tuner to explore even more performance, upping the ethanol content to E30-E40. With good air and DA, was able to achieve an impressive 11.05 @ 124.87 mph with the stock exhaust. Not bad, right? To run 10's on stock everything other than just tuning and fuel was the goal, so close!

Fast forward to recent, and I’ve just tested our 2021 GLC63s bone stock with 11,000 miles on the clock:

• 93 octane w/ 1 g of E85 57°F, 11 DA
  • 1/4 mile: 11.67 @ 116.62 mph

Pretty stout, in my opinion. While I've already order the CPC module to tune the exhaust valves and remove any other nannys, I'm scratching my head... Is it really worth worth tuning for small gains on 93 octane, or does the S (coupe) really gain more performance because just by its shape of the body (aero) which I doubt there much of a difference?

While I agree that tuning (CPC/TCU/ECU) makes a night-and-day difference for non-S models, I’m curious if its worth it on the S models especially running only 93 octane pump gas.

By the way, it’s interesting looking back at my older posts about mods we've shared—one of the things I tried back then is now being sold online by random vendors. Here are some older posts of my pasted GLC63's. Thanks for listening!

https://mbworld.org/forums/glc63s-gl...package-2.html
https://mbworld.org/forums/glc63s-gl...3-results.html
https://mbworld.org/forums/glc63s-gl...er-spacer.html

 

Forgot I did some conversion body stuff on the 2020 GLC63, here is the thread. Wow forgot about that lol Also here are some past pics of both the 2018 GLC63s and 2020 GLC63
https://mbworld.org/forums/glc63s-gl...t-package.html

 

We’ve lowered her yesterday with links, also had the front window tinted. Was aiming for a balance between style and comfort. While keeping ride quality in mind, we didn’t go too low since Mercedes nailed it with the stock suspension. But let’s be honest, the lowered look is irresistible!

Our goal was to match the Race mode height (lowered) while in Comfort mode, with just a touch more drop. Race mode typically lowers about 0.5" compared to Comfort, so we achieved a 1" drop in the rear and 0.5" in the front for Comfort mode. In Race mode, that translates to a total drop of 1.5" in the rear and 1" up front, as seen in these photos.

 

With the temps dropping, the weather’s been cooler for some performance runs. Decided to do a few Dragy tests! Current mods include a gutted secondary cat and about 2.5 gallons of E85 in the tank for a little extra kick. 😉. MPH and 60-130 is showing some good results, et isn't the greatest with 0-60 times in the 3.5 second range, just can not get better with its stock tcu/cpc settings and hurting et's, plus it will just spin all 4 tires. This is one areas that having the ecu/cpc/tune tune seem to really help greatly. But... IMHO the tuning on the S is pretty damn stout for stock especially compared to the none s models.

 

Here’s a quick exhaust video after deleting the secondary cat—sounds perfect to me! You can even catch the turbo spooling down at times. 😊
https://www.youtube.com/shorts/vHfQfoP4QA8

https://www.youtube.com/watch?v=YqDu2284uC8

 

Happy Thanksgiving, everyone! Had some time today, so I decided to take a cold start video with the new Renntech exhaust valve controller. The difference isn’t huge, but it’s noticeable—especially since the stock valves only open about 60% even with the exhaust button activated, while these open fully. It’s a bit of a boring video as it’s just the cold start, waiting for the idle to settle, but still thought I’d share!

 

Good stuff and awesome chronicles of your GLC journey - thanks for sharing - your whip is fast!

 

Thank you, appreciate that!

 

Do you have a tow hitch installed on yours by chance?

 

no sir, last video posted will show this.

 

I couldn’t resist diving into tuning and reached out to Paul, who helped tune my last GLC63. Turns out the CPC was already swapped, and from what we can tell, it was never removed if someone had tuned it before.

Today, we went ahead and tuned the ECU and TCU. The car feels so much better down low now—the missing torque and throttle curve are back, and it’s a game-changer. Unfortunately, we couldn’t replicate the flex(ish) 93-E40 tune we had before, so we went with the standard 93 tune instead.

I ran some Dragy tests, and while the gains aren’t mind-blowing, they’re definitely noticeable and worth it. The extra power really shows in the 60–130 times. Using the same fuel setup (2 gallons of E85 in a full tank), here’s the comparison:

• Prior (CPC tune only): Averaged 11.25 seconds for 60–130 in 50°F weather at -400 DA.
• Today (ECU and TCU tuned): Averaged 10.35 seconds for 60–130 in 72°F weather at 1151 DA.

That’s about a 1-second improvement despite less favorable weather conditions. With similar weather to before, she should easily hit low 10s or even high 9s for 60–130, and this is still with stock downpipes and intake.

I also tried some 1/4-mile runs, but the PS4S tires are pretty worn and couldn’t grip well. My best 0–60 time was 10.3 seconds, but most runs were between 10.4 and 10.5 due to spinning. That said, the trap speeds tell the story: an average of 119.64 mph now compared to 116.55 mph before. That’s a solid 3 mph gain, which speaks to the improvements.

I’ve already ordered 200-cell catted downpipes and might follow up with an intake. If I can get her into the 9s for 60–130 in average temps/DA with a bit of ethanol, I’ll be absolutely thrilled.

 

Some impressive times. Must admit I am a little jealous of how great the 63 sounds, they were just a little out of my price range so settled with the 43 instead.

 

Absolutely agree with you. Honestly, it’s the sound that mostly brought me back—the visceral, muscle-car feel it delivers. I’ve owned plenty of other high-end cars and SUVs, and while there are now so many faster platforms out there, it doesn’t mean as much if they don’t sound right. Sadly, the era of being about to purchase a V8s is slowing coming to an end. Companies like Mercedes and many others have been forced to pivot due to political pressures and environmental policies and its really not fair imho.

 

Call me a pickle and color me green! Tonight we received some fantastic air. Although the weather is perfect, it is still difficult to launch with scorching the tires through the second. Despite trying a few different approaches, the results are still undesirable. Yet a 3.25 seconds from 0 to 60 is too horrible. Very pleased with running low 9's 60-130 time and a 123 mph achieved in the 1/4 is great. Maybe 8's 60-130 with dp and intake?