Boost Reference

[corsair231]

Hey guys, I have an issue I'm just trying to sort out. I posted this question two weeks ago on the TT forum hoping to get an answer there but no luck yet so moving the question here.

Just wondering where our VelocSyty chips get the boost signal from for it's boost control function. I assume it reads from the map sensor and then adjusts the wastegate cycle. The issue I have is that I have a ScanmasterG and when it is set to display boost it shows different than my mechanical gauge. The G shows 10 psi while my boost gauge shows 15 psi. Is the G showing what the computer sees from the map or is it displaying what the boost should be based on what the chip is commanding? Just trying to figure out why they read different. The reading seems to keep about the same ratio, 2 psi on the G to 3 psi on my gauge. It is a 3 bar map and I don't think I have any boost leak in the map circuit hoses. I have the map and fuel pressure regulator on a dedicated circuit so there's not many places it could leak. Truck pulls well but I worry if the computer is not seeing correct boost it may lead to leaning out. 93 octane with no "check engine" flashing so I assume no knock. Seems the next logical step would be to switch the gauge out with another mechanical to verify it. If it checks out then switch vacuum sources to rule out any plugged ports. If that checks out then swap the map sensor with another 3 bar to check it out. Sound about right? Any thing I'm missing?

Thanks

 

[2500avalanche]

Same issue happened to me. Did you set the scan master to read for 3 bar? It is in the set up of it.

 

[corsair231]

Same issue happened to me. Did you set the scan master to read for 3 bar? It is in the set up of it.

Did you have the box scan master or the round G? Everything I saw in the instructions for the G said a 3 bar was required and I don't recall seeing anything about choosing a map sensor setting but I will take another look at the instructions. I did read somewhere the original G's, (the OG's, haha) had to be re-flashed to read correctly but this is a brand new one which should have already been corrected since the G has been out for a few years now.

 

[2500avalanche]

I have the round G. Look on page 4 of the user manual.
Hold the mode button (left one) for 10 seconds.
Use the recall button (right one) to change perimeter! If you need any other help PM me. I will give you my cell#

 

[Slyclone]

I just got a scan master G , and a turbo tweak. Haven't put power to anything..only because I have to keep reading. But I'm glad I saw this, in the event I need to change the setting to 3 bar.

 

[corsair231]

Thanks avalanche, that seems to be the problem. haven't be able to drive it to make sure yet but it was set on 2 bar. I read the manual and even went looking when I noticed it was reading wrong. I missed it both times. Blind as a bat sometimes.

Well they say the only dumb question is the un-asked one. Guess I proved that theory wrong.

Slyclone, hopefully then I may have saved you some trouble in the future. Oh and another thing I didn't see anywhere is that the default Air/fuel display number is 10-1 if you're still running the stock narrow band O2 sensor.