I finally got hold of my 3 Bar GM Map sensor and decided to test it head-to-head with the JDM Map sensor. Both were hooked up to the LMA2/LM1. The volt-to-psi configuration for both is based on mrfred's work and the spec sheet for the sensor from GM.

One is hooked to the intake manifold and the other was hooked to the firewall with a very short hose to the FPR vaccuumm hose. Since the JDM MAP on the intake manifold tends to pick up noise, I applied a 0.25 sec smoothing to it via Logworks.

I also logged the JDM MAP via the OBD2 port. As you might know, this way to log boost tends to be the laggiest.

I did 4 back to back runs on my Evo 9 running stock boost. I have not adjusted the boost on the car one bit.

Overall, the results are very close to each other. There is less than 1 psi discrenpancy between the two across the rpm range.

Here are the charts: The top chart is the JDM and the bottom one is the GM sensor.



Below is one run of all the sensors together: JDM via OBD2 (Gold); JDM via LM1 (red); GM via LM1 (Green). Notice how all three track very close to each other, but the JDM via OBD2 is lagging behind @ the start.



I know that some have had different results from the JDM and their ZT2 logger, but I did not see that in my testing. I do not know why they had different results. It could be a matter of setting up both sensors properly, or it could be something else.

 

Good stuff

 

Nice work NJ.

 

Excellent stuff man.

 

Thanks, NJ. Good stuff here.

Could you test the sensors at higher boost levels? Say, 24, 25, or 26psi? As you may recall, the issues a few of us have seen are at higher boost pressures.

 

which one is cheaper? easier to install? easier to get ahold of?

i'm slacking, i need one

 

wow, i did not realize how laggy the logging of the JDM sensor is. great work.

 

It is laggy ONLY if you log it through the OBD2 port. The reason is because the ECU has a slow response rate. Logging the JDM sensor via the LMA2/LM1 that I used is as fast as the GM 3 bar sensor. Basically, it is not the sensor it is the ECU.

 

The JDM MAP sensor is stealth. You unplug the USDM MAP sensor and plug this one in its place. You flash the ECU with the needed tables/data provided by mrfred in a thread in this forum. And then you can log boost via the OBD2 port with Evoscan. At $130 shipped, it is easy, but more expensive than the GM 3 Bar sensor.

The GM 3 bar needs more installation know how and a logger that can log boost like the LM-1/LMA2 that I have. It retails @ around $70 with the pigtail harness.

 

That will have to wait until I start messing with the boost settings. Even then, I do not think I will run 24 psi boost on 91 octane. Maybe, when gas prices drop and I can go back to mixing for 93 octane, then I will test @ high boost.

To be honest with you, I do not think the boost level has anything to do with your issues. It is either the way you have your system set-up or the logger itself.

 

It would be nice to see both of these sensors hooked up to a common controlled pressure source on a bench-top with a common voltage fed to both and a chart made that ran them from -30"Hg to +42psi (just under the 3bar max) and compare output voltages between them...that would give the figures you really need for remapping the ECU to the sensors' total range.

I know this would be a pain in the **** to do...you would have to cobble some fixture for an airtight container that would hold the JDM MAP sensor, come up with a variable power source to power them, a vacuum source, a pressure source...ermmm...yup, a PITA!

Just a thought...I will now go back to lurking.

 

Rummaging around www.delphi.com and came across another option from GM-Delphi....a combined MAP/MAT sensor logs to 3.5 bar and does up to 125C temp ... in one sensor
http://www.delphi.com/manufacturers/...ors/et/mapmat/


This could be used to determine both the boost and the post IC temps if placed on a bung on the upper IC pipe, just before the TB. Coupled with a separate second sensor on the LICP, this would provide a solution for those companies or people who wish to test both temps and pressure drop across intercoolers. This would end the debate about flow and heat soak.

In relation to this thread, there are issues with the JDM 3 bar MAP, not with accuracy, but in throwing codes. The sensor is also part of the EGR routine and using the JDM 3bar appears to throw a SES at random times on the VIII. mrfred is still chasing down the location in the code for EGR tables on it IIRC.

As Naji referred to above, the GM one takes more to install, but can be logged in Logworks ( free ) . At some point here, i plan on tapping the UICP and placing one there and on the custom LICP I'm having made. Logging will be Logworks, not OBD2, as Naji explained for the higher data rate..along with my LC-1

As an additional teaser, a simple differential circuit to compare in/out temp and evaluate boost can have an output routed to a relay to power an ic sprayer to come on automatically at 15 psi and a temperature higher than " X" ...doesn't need to be hooked to ECU....for those road racers and HDPE guys who want to stay cool without thinking about it.

Milburn

 

Good stuff, i'll probably stick with the JDM sensor, i like simple =-)

The simpler the less that can go wrong, my motto =-)


Cheers!

 

I've been curious about what you mean here. By ODB2, do you mean EvoScan or Mitsulogger? If so, how many parameters are you logging when you do a run?

 

I am using the Logworks plug-ins for the tactrix cable. There isn't a way that Evoscan/Mitsulogger can log boost outside of the OBD2 port. As such, I cannot compare their boost logs from the OBD2 port to another logger. Logworks integrates data from the OBD2 port and data from the LM1/LMA2 into one log and you can see how much slower the response from the OBD2 vs. the LM1/LMA2 when it comes to boost.

I have attached a log. The OBD2 boost column is labeled "OpenPort_Boost". The LM1/LMA2 JDM boost column is labeled "PSI" and the GM 3 Bar boost column is labeled "GM_Boost." Notice how the OpenPort_Boost column keeps giving the logger the same boost numbers. This is because the ECU has a slow response time and cannot keep up with the requests from the LM1/LMA2.