So I measured boost on my CLS550.....

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Old Sep 18, 2025 | 10:23 AM
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2005 S55 AMG
So I measured boost on my CLS550.....

....And it wasn't what I had expected. I heard these will see 11psi (ish) max but on 2nd and 3rd gear pulls the most I saw was 7.5psi. The car went 13.1 at 108 at the track which seems about right, so I'm sort of stumped. Anyone else measure boost stock or tuned? Thanks.
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Old Oct 30, 2025 | 10:48 PM
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2005 S55 AMG
Well, I got the tune back on, and I'm seeing a max of 12.5psi now, so I don't think it was anything wrong with the turbos. Starting to think the "11-13psi" from the factory is a flat-out myth.
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Old Oct 31, 2025 | 08:30 AM
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2015 CLS550 Shooting brake 4-matic
Hi. I might said this before but if that "track time" 13.1 and 108 trap is 1/4 mile time and trap, it's way slower it should be. Back in the day with stock turbos and pump gasoline my shooting brake did go 11.94s and 120 mph trap according to Dragy. Or was your car stock then? Still might be slow.

Also if your max boost with tune is 12.5 psi =0,862 baaria its low.

There is something wrong and holding your car to get the wanted power out.

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Old Oct 31, 2025 | 09:35 AM
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2005 S55 AMG
Originally Posted by PekkaH
Hi. I might said this before but if that "track time" 13.1 and 108 trap is 1/4 mile time and trap, it's way slower it should be. Back in the day with stock turbos and pump gasoline my shooting brake did go 11.94s and 120 mph trap according to Dragy. Or was your car stock then? Still might be slow.

Also if your max boost with tune is 12.5 psi =0,862 baaria its low.

There is something wrong and holding your car to get the wanted power out.
I dunno....most other stock cars are running in the 108-109 range too.....that must have been one heck of a strong tune!
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Old Oct 31, 2025 | 09:43 AM
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2015 CLS550 Shooting brake 4-matic
Okey, I did get confused what time and boost is with tune and what is not. If you are happy with those times and boost everything is good.

I will post later that Dragy shot 11,94s and 120mph what I did get with stock turbos (shooting brake about 0,1s slower than coupe)
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Old Oct 31, 2025 | 09:45 AM
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2015 CLS550 Shooting brake 4-matic

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Old Oct 31, 2025 | 11:36 AM
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Yeah that sucker is rolling.....what type of fuel were you on? The most boost I've heard of on stock turbos is around 20psi on E50. Pretty sure 91 octane is my limiting factor right now. Car has been 12.50 at 112.5 tuned but I think it could go 20s or 30s.

Last edited by JQmile; Oct 31, 2025 at 11:37 AM.
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Old Oct 31, 2025 | 01:17 PM
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2015 CLS550 Shooting brake 4-matic
Originally Posted by JQmile
Yeah that sucker is rolling.....what type of fuel were you on? The most boost I've heard of on stock turbos is around 20psi on E50. Pretty sure 91 octane is my limiting factor right now. Car has been 12.50 at 112.5 tuned but I think it could go 20s or 30s.
Just straight pump gasoline, no meth, full weight. My tuner have done great job.

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Old Nov 2, 2025 | 08:53 AM
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10-second E550
7.5psi in 3rd gear is a little low. 4th gear would show you full boost, but probably still under spec. And in my opinion, it shows in your trap speed, if only by a few mph. I'd suspect a leaky check valve in the boost control circuit preventing full boost.
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