[csu87]

Just saw this posted up on bb and have seen quite a few questions regarding it lately so I figured I would copy/paste. Thanks to MHD Tuning

Originally Posted by martial@mhd

Let me recap the successive ceilings that were overcome:


- 18.5 PSI. The firmware codes put a cap ("Boost ceiling" table) at 1.28bar - 18.5psi. By rewriting several sections in the firmware, this limit is removed. Support for increased boost ceiling is coming to 1M (ikm0s), z4 and 335is (ina0s) this month. Increased boost ceiling is the "mboost" option in MHD.


- 21.5 PSI. The stock sensor is maxed around 21.5 psi, so it must be replaced by the n20 3.5 bar sensor. To use this sensor, the table "map conversion" must be adjusted to reflect the min and max sensor characteristics (50.7 psi at 4.5v). This is what the n20 option in MHD do: it rewrites the map conversion table for you with the n20 characteristics.


Stock map conversion



N20 sensor map conversion as applied in MHD.


- 22.5 PSI. This is also a firmware code limitation, but it is much more complex so it is easier to work around this limitation. The best way found so far is to scale the TMAP sensor voltage. Below a point, say 10psi (2.1V on the n20 sensor), the stock voltage is reported. Above that point, only 50% of the actual voltage is reported, and the map must be adjusted accordingly. 30psi is reported as 20psi.

This voltage scaling was implemented using a reprogrammed jb+ (maxboost device). MHD inverts the formula to log true boost so you an see 30psi in logs, but with a 210 load.

Pending testing, this feature is coming to MHD though a firmware logic change and will no longer require a dedicated hardware. The Map conversion is replaced by a 3 entries, custom map.



Up to 2.1V, the voltage scaling is 100% identical to the n20 scaling table above, then only 50% of the added boost is reported. At 4.5V, the 50.76PSI (~36psi relative) are reported as 37.7 PSI (23 PSI rel).

The use of a table means that
- we can move the middle point, so change of scale doesn't need to apply at a fixed 10psi.
- other sensor may be used in the future for more than 36psi.

[NA55]

Good info.. Looks like MHD is developing nicely..

[JasW]

Great explanation. Inlets, then this.

[sirdaft1]

Can someone clarify as to whether JB4 does the same thing as MaxBoost if using the 3.5bar tmap sensor?

[jippii ensio]

Originally Posted by sirdaft1

Can someone clarify as to whether JB4 does the same thing as MaxBoost if using the 3.5bar tmap sensor?

Technically they do it in different ways but both are able to increase boost to max the 3.5bar sensor.

Soon you don't need any hardware other than the sensor. MHD starts to show what it is capable of

[NA55]

Originally Posted by sirdaft1

Can someone clarify as to whether JB4 does the same thing as MaxBoost if using the 3.5bar tmap sensor?

All tunes have the capability to run higher boost levels.
Only difference is that both MHD and Cobb currently require the Maxboost module, but from from the OPs post it appears that MHD will soon be able to do it without the Maxboost module.

[JasW]

Originally Posted by jippii ensio

Technically they do it in different ways but both are able to increase boost to max the 3.5bar sensor.

Soon you don't need any hardware other than the sensor. MHD starts to show what it is capable of

The sensor and the $32.50 harness from BMS.