TechnoMotive Datalogs - Injector Comparison

by Jeff Lucius

The TechnoMotive Datalogger is a diagnostic and monitoring tool that allows you see the internal workings of the engine control unit (ECU). It consists of a cable that connects the car's diagnostic port to a portable computer, and DOS or Windows 95/NT software. The TMO datalogger is available for 1991-1995 DSM cars and 1991 through 1993 Mitsubishi 3000GT/Dodge Stealth cars (with OBDI-style ECU connector and diagnostic port).

Dates: June 4, 2000 with 380s installed; July 23, 2000 with 550s installed
Location: Golden, CO, USA; Ramp from Indiana Avenue onto 6th Avenue West, slight incline
Relavent modifications: TEC 15G turbos, ARC2 MAS conversion (installed for both logs), complete ATR exhaust, oversized intercoolers with 2 inch hard pipes

Ambient Conditions 380 cc/min inj. 550 cc/min inj.
Rel. Humidity
Dew Point
12.25 psi
12.18 psi

This TechnoMotive Datalogger chart shows six ECU data values on the vertical axis versus time on the horizontal axis. There are two seconds between vertical dashed lines of the same weight. The purple curves are from a wide-open throttle (WOT) run through first and second gears with the 380 cc/min fuel injectors installed (stock injectors are 360 cc/min). The lighter blue curves are for a similar run with Nippon Denso 550 cc/min injectors installed. Maximum RPM attained in first gear for each run were just over 7000. There are four interesting things to note in these datalogs.

First there is no engine knock perceived by the ECU. However, knock often does occur until third and higher gears as the mechanic advantage provided by the transmission decreases and engine load therefore increases. Second, at the same boost, the car accelerates only slightly faster with the larger injectors (note the close overlay of the RPM lines). The oscillations of the RPM lines are not real and are a function of datalogger data acquisition. Third, the injector pulse width is proportionally less for the larger injectors; maximum injector duty cycle (IDC) was about 90% for the 380 injectors and about 60% for the 550 injectors. The total fuel consumption was nearly the same, as were the exhaust gas oxygen concentrations (O2 sensor voltages).

Finally, the spark-ignition timing was advanced 5 to 10 degrees more with the larger injectors than with the smaller injectors. The timing advance is increased for the larger injectors because the air flow values (not shown) reported to the ECU by the ARC2 decreased by about one-third compared to the stock MAS with stock injectors. When the ECU sees smaller air flow values it thinks that the engine load is lower and it increases timing advance. Theoretically, this should indicate better performance for the 550 cc/min injectors. It is not certain if the timing values reported by the TMO are the actual timing values seen by the engine. My timing light shows about 10 advance at warm idle while the TMO shows about 28 advance at the same time. However, it may not be as simple as dividing the values seen below by three because 11 to 14 advance at high RPM seems a bit low. In any case, the relative values show an improvement when using the larger injectors.

Maximum Boost = 15.5 psi
TMO log: 550 & 380 injectors

Before some of you ask, yes the Air Flow (Hz) measurement is missing from the image above. If you have the TMO software, you can download and view the two original logs below. Others can download and view the comma-delimited version of the files.
TMO log file for July 23, 2000 - 550s
TMO log file for June 4, 2000 - 380s
CSV file for July 23, 2000 - 550s
CSV file for June 4, 2000 - 380s

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Page last updated March 17, 2002.