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Bad launch/short shifting with JB4

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Old Sep 1, 2022 | 01:14 AM
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2019 C43
Bad launch/short shifting with JB4

Hey everyone, first time posting here. First MB as well. Picked up a 2019 C43 wagon 3 weeks ago. Installed a JB4 on it a week ago and I’m not sure it’s working out well so far so I wanted to ask anyone here with experience launching and drag racing.

Stock, brake boosting hard until car was straining, car felt GREAT.




JB4 map 2: obviously making more power, datalog confirms extra 4psi of boost with no obvious timing retard, but it seemed to bog down on aggressive brake boosting so I launched when revs hit 2000rpm. Still though the car seemed to shift 1-2 at 4500rpm and then 2-3 at 5000rpm. What gives???? Lot of speed left on the table I think

So does anyone have any experience with the car short shifting? BTW TC was fully off. And JB4 does have the BCM.

thanks everyone!
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