I currently am running a GM 3-bar map sensor on my setup but am planning to change it over to the Hondata 4-bar unit. Nothing will be changed on the setup and of course I will change the settings for the map sensor in s300, my question is will this have any negative effects on my tune and/or would it be unsafe to drive on in and out of boost?

 

When you rescale the calibration for the 4bar just note a few load points and the cell values. Make sure they correspond to the same load/rpm points as before.

 

Does that work in all EMS systems? Back in the day when I was boosted on Crome, I switched from the OEM 1.8bar map to a GM 3bar and had to retune...(its probably due to my freebie tuning software)

 

You didn't have to retune per say, but rather blend a few columns together. The problem is it rescales the map without taking the numbers to the new column.

Say you had a fuel value of 1205 at 8k rpms and 10 psi on a stock map sensor. When you recalibrate the MAP the 10 psi column may turn into the 18 psi column but still keep the 1205 fuel value that was originally for 10 psi. Thus lacking fuel and needing a "retune"...

 

Exactly, and it depends on how many load columns he is using. For instance Hondata S300 supports 24 x 20.
If the OP is using all 24 columns for 3 bar resolution then switches to 4 bar resolution in the same 24, hes has alot of work to do.

But if hes only using 16 columns for 3 bar, switching to 4 bar he can simply add 4 more columns and keep columns 1-16 the same values as before.
*This should be in the EMS forum.