Tech Corner

The difference between gauges lines – Standard EV vs. EV² and Performax

EV vs. EV²
There are a number of advantages to the EV² versus the EV series gauges. They are similar in appearance (available in the same general styles), but EV series uses curved lenses.

The EV series uses a separate “amplifier box” near the gauge head, so you need to find a mounting spot for it. The amplifier box for a Pyrometer measures about 2.3″ x 2.3″ x 1.6″, and for a temperature gauge it measures about 2.75″ x 2.4″ x 0.88″. The EV series is an air core gauge movement, basically a set of electric windings, with electronics in the amplifier box to drive them. They also use conventional incandescent bulbs for lighting, although we offer LED replacement bulbs in a variety of colors. They do have the benefit of allowing you to change the backlighting colors. The EV series does include mechanical boost and other pressure gauges. These are typically lower cost than electronic gauges, but require running tubing into the cab. In the case of a fuel pressure gauge, it requires the use of an isolator to keep fuel out of the cab.

The EV² Series is completely “standalone”, no amplifier box needed. They utilize stepper motor movements for precision, and LED backlighting for brightness and durability. Both of these technologies allow the gauge to operate at a very low current draw (less than 0.1 Amp with lights at full brightness). Also, the backlighting is powered by the main ignition input, without drawing any measurable current from the dimmer circuit of the vehicle, so there is no worry about overloading the factory dimmer.

The EV² gauges also include an integral programmable warning light, which may be activated and adjusted using Programmer P/N R82003 and a PC. The Programmer may also be used to adjust the backlighting curve to perfectly match the factory dash lights, and can also adjust the amount of signal filtering/smoothing that the software performs.

If price is a significant factor, you may want to consider using a mechanical EV boost gauge with EV² series for the remaining gauges. Since the mechanical boost gauge does not require an isolator (as with mechanical fuel pressure), you could install it at a lower price than the comparable EV² electronic gauge. The EV² would still be simpler to install, but at a higher price. The EV gauge would be very similar in appearance except for the curved lens. Mechanical EV2 pressure gauges will be introduced in 2013, at a lower price than the electronic pressure gauges.

See also Temperature Compensation below.


EV² vs. Performax™
The Performax and EV² series share many attributes: Stepper motor movements, LED backlighting, solid-state sensors and programmable warning lights. The EV² individual gauges cost more than the Performax counterparts, since the gauge must contain the processing power, while the Performax processing power is mostly in the ESP controller. The Performax series uses an underhood controller (the ESP) which connects to all the sensors (so you don’t have to run all those sensor wires through your firewall). There are 3 common wires which run to all of your gauges (up to 17 total), simplifying your wiring and allowing you to move gauges around to any location. The Performax system also includes the Total Recall™ feature, which provides the ability to view the extreme values of all functions connected to the Performax system. For most functions, the stored value is the maximum value, but on fuel system pressures (Fuel, HPOP, and Rail Pressure), the lowest value while under load is recorded (requires the use of Performax boost gauge sensor). This allows you to focus on driving down the dragstrip or pulling track, keeping it in the groove instead of trying to see if your fuel pressure is dipping at the end.

The ISSPRO Performax PC Datalogger is an optional interface module and software package which allows your Windows-based PC to record all of the data being read from the sensors connected to the Performax ESP controller.

The module connects to the gauge wiring in place of one gauge (or you can wire in an additional gauge connector in a convenient spot for the module), then connects via the included cord to the USB port of your PC.

The software displays actual values for all sensors connected to the ESP while it is logging (there is a start/stop button on the screen). When logging, the software writes to a comma-separated-value (CSV) file to be opened up in Microsoft Excel (or a similar program). The data is logged for each channel at 5 samples per second. You can use your spreadsheet (e.g., MS Excel) features to analyze and graph the results.

The data is logged for all sensors connected to the Performax ESP, regardless of whether a corresponding gauge is installed. You can have all 17 channels connected to sensors for datalogging, even if you only have room for 3 gauges in your truck.

Also available is the Performax USB Datalogger, which records the data directly onto a USB drive, eliminating the need for the PC in the vehicle.

If you are not interested in the Total Recall or PC Datalogger features, then EV² is the likely choice when installing 3 or fewer gauges. For more gauges, the Performax system is more cost effective, especially when installation time is taken into account.

Pyrometer temperature compensation
One significant benefit of ISSPRO Performax™ and EV² gauge systems is the temperature compensated pyrometer, unique in automotive pyrometers.

Conventional pyrometers just measure the difference in temperature between the probe tip and the leadwire end (typically at the gauge head). The industry standard is to calibrate on the assumption that the gauge head is at 70° F. In an enclosed cab on a hot day with a dark colored interior, a gauge can reach well over 170° F and will be very slow to cool off (the pods act as a good insulator). This will result in your pyro displaying a temperature over 100° F cooler than the actual temperature, in conditions where you are likely to see high temperatures. Because of this inherent inaccuracy, ISSPRO Performax and EV² pyrometers utilize temperature compensation circuits and show the actual probe tip temperature.

Pre-turbo or Post-turbo thermocouple installation?

Clearly the manifold (pre-turbo) installation is better in almost all circumstances. Many people from the “old days” worry about thermocouple tips breaking off and chewing up the turbo. This fear is a relic from the days of exposed-junction thermocouples (the type still used in laboratories). For 40+ years the automotive standard has been to encase the thermocouple junction in a welded sheath of high-temperature stainless steel. More recently they have also been made out of Inconel stainless, which is rated for continuous use at 2000° F. Here at ISSPRO we have not had a single report of a sheathed-design thermocouple breaking and damaging a turbo, with over 40 years of history.

Measuring pre-turbo tells you more about the temperatures your pistons are seeing, as well as the worst case temperature of your turbo. The temperature difference between pre- and post-turbo can vary anywhere from +500° F (pre-turbo much higher when under heavy load and temps rising quickly) to -100° F (post-turbo hotter immediately after starting downhill after a hard pull uphill).

The only time we see post-turbo measurements as preferable is when monitoring the turbo temperature during shutdown. As the turbo cools off, it is being cooled by the exhaust gases at no-load (which are now cooler than the turbo). These gases get heated up as they cool off the turbo, so you actually see a warmer temp post-turbo. However, the difference between pre- and post-turbo temperatures is minimal by the time the turbo has cooled to around 300° F (which is where most people shut down). In other words, post turbo lets you see the cooldown progress better, but it is nearly identical to the pre-turbo reading by the time you reach the shutdown temperature. To shut down automatically, many customers install an ISSPRO R4130 Turbo Temp monitor.