Boost Logging



This is intended to be a supplement to the instructions for how to perform boost logging for Federal spec (non-California) 1G (91-93) 3/S cars that was created by Clint Battersby (cbatters on 3SI). The thread describing how to do boost logging can be found here. The research and instructions that he has provided are excellent, and this is in no way negative criticism towards his work. It is intended to provide additional information and pictures for those who are not electrically inclined.

Parts


In order to do boost logging, a pressure sensor (and possibly the corresponding harness), various electrical connectors, and various vacuum fittings & hoses are required. Pressure sensors are available in multiple pressure ranges, including 1 bar, 2 bar, 2.5 bar, 3 bar, and 3.5 bar. (these are absolute pressures, which means that they correspond to maximum gauge pressures of 0 psig, 14.5 psig, 21.8 psig, 29.0 psig, and 36.3 psig). For the typical twin turbo 3/S applications, the most appropriate would be the 2.5 bar or 3 bar. In my opinion, the most readily available with respect to the pressure sensor and a harness is the GM style 3 bar pressure sensor (from 89 Turbo T/A). The available options for 3 bar pressure sensors are as follows:
GM Style 3 Bar Pressure Sensors
ManufacturerPart Number
GM (old)*16040749
AC Delco (old)*213-101
GM (new)**12223861
AC Delco (new)**213-1562
MSD**2313
MSD (compact)**23131
Borg Warner**EC1678
NAPACRB219481
Electromotive Engine Controls71130
Holley538-23
* denotes that the sensor is "old" style; this means that the keys for the harness are located on pin A toward pin B, and on pin C away from pin B.
** denotes that the sensor is "new" style; this means that the keys for the harness are located on pin B away from the clip and on pin A pointing away from pin B.
Others are unknown regarding keys. If you have info about any of these, email me


The available options for harnesses to match the 3 bar pressure sensor are as follows:
GM Style 3 Bar Pressure Sensor Harness
ManufacturerPart Number
GM (old)*12085502
AC Delco (old) *PT123
NAPA*ECHEC14
Carquest *S-595
GM (new)**15305891
AC Delco (new)** PT1035
GM (A/C)***??
Conduct Tite***85146
Calterm (A/C)***08826
Calterm (MAP)08658
* denotes that the harness is intended for the "old" style MAP sensor; keyways are located on pin A toward pin B, and on pin C away from pin B.
** denotes that the harness is intended for the "new" style MAP sensor; this means that the keyways on the harness are located on pin B away from the clip and on pin A pointing away from pin B
*** denotes that the harness is intended for a GM A/C Pressure Switch; keyways are at ?? on pin?? and ?? on pin??
Others are unknown regarding keyways. If you have info about any of these, email me
Additionally, there is a 2.5 bar sensor available from Digikey (MOTOROLLA MPX4250AP MAP SENSOR). Additional information for it can be found at the thread listed above. (The picture below shows this sensor installed)





All of these numbers for the sensors and harnesses have not been verified, so please be sure to check that the harness is the correct style and that the pressure sensor range is correct. It is a 3 terminal plug with all three terminals in a row and equally spaced. The plug housing on the harness side is female, and the actual terminals in the harness side of the housing are male. (See pictures below) Some of these harnesses will not have the appropriate keys and keyways, and will require a knife or small grinding disc to modify the harness so that it will fit. (see info above and pictures below)







Electrical Connections


I used a 2 wire trailer plug to replace the EGRT connector (A-22) and a quick disconnect tee for the TPS connection, as opposed to hard wiring in the new connections to the MAP harness (so that it can be easily disconnected if necessary.)






The wire for pin A on the harness is connected to the black wire on the EGRT connector (ground). The wire for pin B on the harness is connected to the white wire with a black stripe on the EGRT connector (MAP signal). Check voltages on the A-22 EGRT connector before making the connections. The ground on the EGRT connector is connected to pin A on the harness and pin B is connected to the wire that has voltage on the EGRT connector.




The wire for pin C on the harness is connected to the green wire with a yellow stripe on the TPS harness (it is the +5 volt source, and should be the top wire when the harness is connected).








MAP Sensor Mounting

An excellent location to mount the MAP sensor is on the firewall. If the factory solenoids (boost, EGR, FPR, etc) have been removed by doing the vacuum reduction, then the mounting bracket can be cut and/or completely removed. One of the long bolts from that mounting bracket will work well for mounting the MAP sensor to the firewall. This location serves well to minimize the amount of vacuum lines.






Pressure Source

The pressure source that I chose to use was the line that comes off of the rear of the plenum. I used a tee and a couple inches of vacuum hose. The pressure connector nipple on the MAP sensor is fairly large, but it will work with the standard size vacuum hose. A small amount of some type of lubricant (motor oil, WD-40, spit, etc - use your imagination) will help to get the hose onto the pressure connector nipple more easily.





Logging


To log this information, MMCD or Shiver's software is required because Pocketlogger currently does not support this option. The MMCd software is free and is available here. In MMCd, the EGRT source will need to be set to 3.0 bar (or whatever sensor you have used) under the "preferences".





To ensure that the connections have been properly done and that the appropriate sensor has been selected on the software, check the logger with the ignition on and engine off to see that it reads ~0 psig. (The exact value will vary depending on altitude and weather conditions). Mine always reads 0.7 psig when the engine is off, but when running under vacuum and boost, it reads the exact same as my Blitz boost controller and mechanical autometer gauge.

Also, there are several options and preferences that will enhance logging, and become even more valuable when logging boost. One is the peak/hold feature, which is useful for many parameters that are being logged, including boost, RPM, knock, o2s, IDC, etc. Another feature is the auto-trigger function that can be set to start logging whenever a certain condition is met: common ones would be TPS>80% (or whatever you want to consider WOT), or when knock > 5 (or whatever limit you feel comfortable with). I believe that it also captures a short period of time before the condition is met which may provide beneficial information, particularly if the auto-trigger is set for knock.


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