Boost pressure - C400
Thread Starter
Junior Member
Joined: Mar 2019
Posts: 39
Likes: 2
From: Toronto, Ont.
2015 c400
Boost pressure - C400
Can anyone tell me what the stock boost pressure is for the C400. No tune, stock turbos.
I am trying to locate this info online and having a tough time finding it.
I am trying to locate this info online and having a tough time finding it.
Senior Member
Joined: Mar 2018
Posts: 326
Likes: 105
From: Central Florida
'15 C400 and '15 ML350
My C400 ECU commands between 9 and 10PSI. On the JB4 graph its looks like the ECU has the boost tapering off after a shift. Starts high around 9.5 and drops down to 7.5 for the next shift.
Thread Starter
Junior Member
Joined: Mar 2019
Posts: 39
Likes: 2
From: Toronto, Ont.
2015 c400
It will vary depending on the weather. Progressive map is to try and keep the car seeing the same air in different conditions.
My C400 ECU commands between 9 and 10PSI. On the JB4 graph its looks like the ECU has the boost tapering off after a shift. Starts high around 9.5 and drops down to 7.5 for the next shift.
My C400 ECU commands between 9 and 10PSI. On the JB4 graph its looks like the ECU has the boost tapering off after a shift. Starts high around 9.5 and drops down to 7.5 for the next shift.
Senior Member
Joined: Mar 2018
Posts: 326
Likes: 105
From: Central Florida
'15 C400 and '15 ML350
@MatthewJ thanks for responding. I have recently installed a jb4 on my c400 and would love to see some of Your logs. Map 2 I’m hitting around 11-12psi with 94 octane. That seem low?
Do you have an intake?
From BMS site:
JB4 Map Guide as of v6 firmware:
Map 0: Disables tuner
Map 1: Up to 4psi over stock peak, suitable for all 91 octane+ fuels
Map 2: Up to 5psi over stock peak, suggested for 93octane+
Map 3: Up to 5.5psi over stock peak, slightly more aggressive version of map2
Map 4: Up to 6psi over stock peak, suggested for E30+ or unleaded race gas mixtures
Map 5: Up to 7psi over stock peak, holding more boost to redline, suggested for E30+ or unleaded race gas mixtures
Map 6: User definable map, boost over stock entered on user adjustment page
Map 7: WMI (water/meth injection) progressive map for BMS FSB integration
Map 8: Low boost VALET map
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Thread Starter
Junior Member
Joined: Mar 2019
Posts: 39
Likes: 2
From: Toronto, Ont.
2015 c400
Hey @MatthewJ , yeah I just installed a BMS DCI last night. I haven't really done any long pulls or anything as of yet tbh. I do feel it mid to high end, but low end boost isn't really there. I updated the firmware to the latest stable one available. This morning on my drive into work I used map 3 and hit it once on the hwy, definitely felt it.
I'd love to see a log of your low end boost and daily driving. My boost is always at 0-1 when not hammering it, does that seem right? I mean, I can hear it charge up and release with the intake but the logs just don't show anything until I go WOT.
I'd love to see a log of your low end boost and daily driving. My boost is always at 0-1 when not hammering it, does that seem right? I mean, I can hear it charge up and release with the intake but the logs just don't show anything until I go WOT.
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Senior Member
Joined: Mar 2018
Posts: 326
Likes: 105
From: Central Florida
'15 C400 and '15 ML350
One of my map 6 logs here. Are you looking at ECU Psi, target or boost?
When taking a log its recommended to do runs from like 30 to at least 70 to get a good picture of whats going on. BMS has always been responsive for me when emailing them logs.
Edit: you said daily driving, i have my JB4 set to only log WOT conditions. Ill post a different log with whole drive home all throttle conditions
When taking a log its recommended to do runs from like 30 to at least 70 to get a good picture of whats going on. BMS has always been responsive for me when emailing them logs.
Edit: you said daily driving, i have my JB4 set to only log WOT conditions. Ill post a different log with whole drive home all throttle conditions
Thread Starter
Junior Member
Joined: Mar 2019
Posts: 39
Likes: 2
From: Toronto, Ont.
2015 c400
thanks so much for this @MatthewJ I'll take a look after work and when I am home tonight.
Yeah, Im clearly recording logs incorrectly because i'll just hit "start logging" and then drive around normally.
I need to do a proper log, and that will be in sport+ and from 30-70, we will see what happens then.
I appreciate you taking the time to respond to me - thanks
Yeah, Im clearly recording logs incorrectly because i'll just hit "start logging" and then drive around normally.
I need to do a proper log, and that will be in sport+ and from 30-70, we will see what happens then.
I appreciate you taking the time to respond to me - thanks
Senior Member
Joined: Mar 2018
Posts: 326
Likes: 105
From: Central Florida
'15 C400 and '15 ML350
Define noticeable lol. From the logging its keeping the IAT more consistent and slightly lower (8-10°F). Seat of the pants doesnt notice, but every little bit helps when 10°IAT = 1° timing removed after 80°.
