I have a question for any one that has any ideas......ADM sent me a Aeroforce scan gauge to try out, it reads boost but only to 22.7 psi....when logging with HP it will only read to 255kp = about 22.5 psi....the boost gauge in the hhr will read up to 27 psi...logging on the dyno we see the same or pretty close to what the in car gauge reads.....So my 10000$ question is were does the gauge get its reading from...its electronic so theoretically they all should be the same.

 

A couple of people have indicated that the stock electronic gauge is reasonably accurate, but I've never quite felt like it is (at least on mine as I see jitter very ofen... unless I've got a leaky BOV). At some point, I'll likely plumb a vac line into the hard pipe (don't get excited... I'm still waiting for HRC like everyone else ) to get a "real" measure.

BTW, I think that's a typo above... 255kpa is about 37# of boost. The conversion factor between kpa and psi is .14503773773020923.

 

ECM sends the data to the gauge. Data comes from manifold pressure readings. The gauge has an internal logic module, similar to the clusters, which tells it what to display.

 

255 kPa on a MAP sensor is an absolute reading. To convert MAP to boost pressure the formula is as follows:

Boost Pressure (psig) = MAP (psia) - BARO (psia)

So, at sea level a 2.5 Bar MAP sensor will only read 22.29 psig

The LNF PCM code limits boost to 255 kPa.

 

Good catch... I obviously forgot about the 1 bar we live under already. Oops. Thanks for the correction!

 

The internal code limit on the LNF is 255 kPa. The LNF GDI PCM is a variable boost design based on barometric pressure (BARO PID [PID.2340] in HPT) that will vary boost from 18 - 21 lbs. psig based on altitude.

The gauge displays baro corrected boost pressure and will not read absolutely correct because of BOV control and surge. Now, depending on how you log boost in HPT you will probably see a different reading that is hard to pinpoint. The HPT help file offers a formula to convert MAP to boost, but it uses a 14.5 psia atmospheric pressure constant that is probably not accurate for your altitude.

Your not going to see anything consistantly over approximately 22.5 psig, the turbo simply runs out of steam and the PCM code prevents the BOV from controlling anything over this.

How are you monitoring boost on the dyno?

 

Aha!

According the Rand McNally Commercial Atlas, the elevation for Springfield, MO is 1, 316 ft/401 m, which calculates to 14.01 psia.

 

Is that the max or average elevation for the area?

At 1,316 ft above sea level (14.01 psia) you should see a max of 22.97 psig at 255 kPa.

 

we have a superflow 30 at the shop we plug into the manifold

 

Did you plumb for it? If yes, where? Can we get a pic?