I saw this video, was actually quite close for the mentioned hp difference. For just a piggyback that’s quite insane. Goes to show a legitimate ecu would get you at or above 63 levels.
The 55 has better lower end torque which is why it’s able to jump ahead at the start of both races. Thats how Mercedes makes thier cars. On a street the 55 is actually a bit more torquey and quicker than the 63 especially with a tune.
you don’t notice the difference unless going too a track like such. Also considering how close the roll race was I wouldn’t say it “wasn’t close”

renntech makes great tunes. The 55 piggyback tune on it is nutty I dont doubt your observation.
I read on another thread here from another member that the way AMG builds thier cars are so that the 63 can really thrive on open roads at 150+kmph range. Below that on shorter pulls and regular city driving the 55 and lower models actually feel quicker and more responsive due to them being built for that.
if you put the time and money into it you can most certainly get the 55 to well above 63 levels although I wouldn’t recommend anything past stage 1 for avoiding warranty issues. But a stage 1 on the 55 is more than enough if you’re not going to track it.

looks like you already got your 63 to ludicrous levels of speed haha. Especially with the new gen gt im sure its a little more difficult to find and source these parts considering the c192 only a couple years old.
800-900 is absurdly fast, any goal of what output you’re trying to reach or just shooting for the stars

Look at renntechs dyno numbers on a stock 63. I think instead of the 577hp it was something like 641hp give or take

Could be just the differences noted above and was just going off the old seat dyno and didn’t actually measure it, only going off actual driving feel. I asked how they were getting crazy numbers from the 63 tune if it really was the same engine and seemed to be more about the available parameters they could modify with the 55 vs the 63. 63 with those tune numbers is crazy and that might have swayed my decision if that was available at the time!

Thank you for your explanation

My local tuner has dynoed 2 of the 63s. Both put down very close to the same as what renntech has posted. In the past mercedes use to have a reputation for this. Mclaren has always been this way. My 765 put down 102hp more that Mclaren advertised.

There seems to be a lot of misinformation on here. If the 55 and the 63 were so similar the performance wouldn't be so different. The 55 isn't close to the 63. As I stated earlier working with a tuner they can only get so much out of the 55. The 63 is a completely different story. If these were the same logic would say once both were tuned to max output the both should be the same hp. They aren't even close. People aren't paying the premium for the 63 if there was only the tune difference.

Cant argue the facts here... the measurable times that most fixate on: zero to sixty, quarter mile, trap speeds all clearly favor the 63.

I still stand by my thoughts that the 63 is extremely poorly priced but there are deals to be had no doubt.

Looking at some independent 0 to 60 runs, the 63 was 2.7 and the 55 was 3.2.

Where’s the misinformation? The only misinfo I’ve seen is the claim that the 55 and 63 don’t share nearly 90% of the same engine components when they do. Both use the same M177 engine block, same twin-scroll turbos, same compression ratio, and most core internals apart from what was being said. Nobody’s saying the 55 makes more power than the 63 or can out tune it because that’s definitley not the case. Higher baseline power almost always equals higher tuned ceiling. The point is that the 55 and 63 share almost the exact same mechanical platform, apart from things like cooling ECU tunin and possibly forged components in the 63. Even Mercedes has confirmed this.
As shown in the video above, a properly tuned 55 making 579hp is still understandably reeled in by a stock 63 likely putting down as you said earlier closer to 630hp. That doesn’t contradict the argument, it supports it. The 55 can absolutely match or exceed stock 63 numbers with a solid tune. That’s the whole debate whether the $30K+ premium for a 63 is worth it, given how closely related they are mechanically.

There must be a few upgrades to the 63 that we are missing. The 63 is running a larger turbo i know that one. If a tuner tunes the absolute most hp out of the 55 then does the exact same to the 63 according to some post here their hp should be the same. They are not, they are quite aways apart. So something is causing it, cams, intake I honestly don't know. Logic tells us that if they were just different by their factory tunes then installing a max tune to both would prove that by both showing the same output which they don't. This tells a story just don't know what it is.

You may be correct but as of now its still just pure speculation. As of what Mercedes has said and listed officially the engines are essentially the same. Just because two engines are mechanically the same doesn’t mean they’ll produce the same max output with a tune. The 55 hits thermal limits and torque management walls sooner even with the same tune because its intercooling ecu calibration and possibly even fueling aren’t built to handle as much power. If you put those components into a 55 it sure as heck could handle the same amount. You can’t really tune past hardware limitations without upgrading the supporting systems like Mercedes mentioned in their few differences between the engines. A 55 hits thermal and torque management limits faster not because it's running smaller turbos or different cams but because it's built to be a more detuned version of the same platform.

I’m not the expert, but both GT 55 and 63 uses the same turbochargers 177-090-56-02 left and 177-090-57-02 right. I think ECU limits boost pressure since 55 misses forged pistons while turbochargers are the same.

Exactly correct, components are the same. Mercedes just downplays their 63 numbers, that car is making well above 600 rather than 577. Hence why the 55 with a stage 1 at 579hp still isn't quite as quick as a 63.

Once they start producing actual ECU tunes for the 55 it will no doubt hit 63 power with a simple tune.