The first Chrysler "Hemi" V8 engines appeared on the market in 1951. Since that time, they have been used extensively in the custom car field, being modified and swapped into countless custom vehicles, and in racing form, achieving dominance in several forms of motor racing. The current version ("Gen-3") of the Chrysler "Hemi" V8 engine first appeared on the market in 2003, in the 5.7 liter version. Since that time, Chrysler Corp. has produced other versions, including 6.1 liter and 6.4 liter engines. The fuel delivery and spark delivery systems on the current version of the "Hemi" is controlled by a dedicated purpose computer (Engine Control Unit, or ECU).
The Gen-3 Hemi engine (2003 and newer) incorporates new and advanced engine technology into the original “Hemi” design, and although there are now large numbers of used engines becoming available in the salvage yards, the Gen-3 Hemi has not become popular in the custom automobile field, largely due to the difficulties in adapting the native Chrysler ECU to other applications and to handle engine modifications. More specifically, there are significant obstacles which block the successful reprogramming of the native Chrysler ECU to correctly manage the engine after any performance-improving engine modifications have been made.
Up until now, the only alternative has been to replace the Chrysler ECU with an expensive aftermarket unit. AND here's another "gotcha"......the BIG giveaway with most aftermarket ECU's is the lack of any substantial diagnostic code. One of the MAJOR advantages of OEM units is that in most cases, the program logic contains nearly as much diagnostic code as there is control code.
Further, if a custom car builder wants to use a current “Hemi” engine with a current-technology, electronically-controlled transmission, he has only one option, which is to retain the Chrysler transmission and the Chrysler ECU, which limits him to a completely unmodifiable engine package.
By way of contrast, the General Motors (GM) "LS" V8 engines have seen wide acceptance and usage in the engine swap and custom car fields, due in part to the ease with which the Delphi ECU can be adapted and reprogrammed. In addition, the Delphi control technology is substantially advanced over the Chrysler technology. The Delphi technology is based on the measurement of the instantaneous mass flow rate of the air being ingested for combustion, whereas the Chrysler control algorithm uses measured air density and throttle position to make a guess at the mass airflow rate.
THE HEMITRONIX SOLUTION
In response to this inconvenient problem, NRC has developed hardware and methodology which enables the simple replacement of the Chrysler ECU and associated components with the Delphi ECU and its supporting hardware and electronics, allowing comprehensive performance improvements to the basic “Hemi” engine, while retaining all the immense drivability improvements and reduction of emissions that computer controls have made possible.
Further, this system adapts the more-advanced Delphi control algorithms to the “Hemi” engine, enabling the transplanted engines to obtain substantially better fuel mileage than is possible with the Chrysler system.
Our system includes all the hardware components (coils and brackets, sensors, adapters, crank and cam position reluctors, throttle body, fuel pump, pressure regulator, etc.), wiring harness, the ECU, and a complete, clear set of installation instructions. As an extra option, our system can include the necessary adapters to attach Delphi electronic transmissions to the “Hemi” and control those transmissions with the Delphi ECU.
We have named this system the “HemiTronix".
Here is a picture of our "test mule" engine on the dyno. It is a dead-stock 2004 5.7L Hemi from a truck.
With the HemiTronix control system and with our new throttle body, the engine made over 390 HP and 420 lb-ft of torque. We are currently developing a 6.4L version, which after some judicious head and cam development, should easily make a very streetable 500+ HP.
NOTE: The increased power on the "test mule" occurred with only one plug per cylinder in operation. Why is that? Because the second plug on the Gen-3 Hemi is fundamentally there for emissions purposes. Remember, there are two wires off each Hemi coil, one for the "primary" plug on one cylinder, and the other to the "secondary" plug on the cylinder 360° away in the firing order. The "secondary" plug fires during the overlap period to help reduce emissions.
MOPAR ACTION Magazine was so impressed with the HemiTronix package that they did a full feature article on it in the August 2012 issue.
MOPAR ACTION Magazine has kindly provided us with access to a copy of that article. We thank them for their work and for access to the article.