MAP sensor through OBD 2?
 

Is it possible to monitor a MAP sensor in real time through an OBD 2 port? I mean to make a gauge out of the signal.

Sixto
87 300D

It's possible, per se, but what are you trying to monitor while driving? Are you having issues with manifold pressure or EGR valve?

I'm just trying to understand what you're thinking here...

Correct me if I'm wrong, but isn't a boost gage the same as a manifold air pressure gage?

Yes, you can monitor MAP through ODBII.

The Scangauge is an OBDII gauge that can be set up to monitor a variety of engine parameters.

Yes, Jon is right, a boost/vacuum or manifold pressure gauge would qualify as a MAP readout.

To be correct, MAP stands for Manifold Absolute Pressure.

ELM327 Bluetooth OBD2 II EOBD Software Can-Bus Car Diagnostic Scanner Tool Thanksgiving Gift - Tmart.com

Here is one that will do what you want. There are a bunch of interpiters based on the elm327 chip. Just google it and you will find all sorts that will work and cheap too.

A scan gauge is a great way to do this :)

-J

got a link?

This is the one I have:

ScanGauge II OBD2 Tool XGAUGE included! Ver4.06 Scan Gauge 2 OBD 2 | eBay

When I set it to MAP, it does read absolute. The minimum reading varies around 14.6 or 7 depending on prevailing baro. pressure.

I have one in my TDI and lawson has one in his F350. In my TDI I monitor voltage, intake air temp, coolant temp, and MPG. (The temp gauge on my Jetta is "buffered" so it doesn't show the actual coolant temp). In the F350 we monitor oil temp, coolant temp, IAT, and volts.

For the price of a cheepie scan tool you get a quality built device that does scanning, and has the great gauge functions. It's hard to beat!

-J

I want to get rid of the vacuum controlled wastegate actuator in our 97 Suburban 6.5t. I'm not convinced that a Turbomaster is the way to go. I'd rather fit a pressure controlled wastegate. Before that, I want to study the behavior of the factory setup then tune the modification accordingly. No need for a permanent boost gauge, though.

The option is a boost bolt for a direct gauge but an OBD tool like Scangauge is something I can use for other things as the fleet ages.

Sixto
87 300D

Isn't there an app for that?;)

How about buying a cheapo gauge from Autozone or Summit or Jegs? If you must have electronic, you'd probably need a MAP sensor from something that reads 3 bar pressure, IIRC. Grand National might have one but those MAP sensors are easy to find. Also, why not use a boost valve from Boostvalve Home Page I have used them before and they work well to hold the pressure to whatever you set it for and then release when the target pressure is reached.

As to controlling the wastegate.

My E300 also has a vacuum controlled wastegate. I can tell you a few of it's behaviors, some of which may translate over to your 6.5.

Idle is full vacuum/boost.
Cruise is full boost until a steady state is achieved, then boost is dialed back to nearly nothing. If the ECU doesn't see the drop in boost at cruise, a code is set.
Any more than about 60% throttle results in full boost commanded.
Tip out dumps boost.
Tip in after coasting commands full boost.

Now, the way I observed my turbo function was to gauge the vacuum going to the wastegate. This way, I can at least see what the ECU is trying to do, rather than what is ultimately happening.

One other thing I did for testing is to hook a vacuum line directly to the wastegate to run full boost all the time. It did fine except that the code was set at cruise since the boost would not respond to the dial-back command from the ECU.

It has a MAP sensor so I shouldn't need another one.

A bleed valve won't work because it's vacuum actuated. Less vacuum = less boost. I can use one of those, in fact I think I have one in the garage, when I convert to a pressure actuator.

Good point, I should monitor the vacuum signal as well.

Sixto
87 300D