Auto Military Pinzgauer

Pinz EFI Old

By far the highest impact modification I've made to the Pinz is to add a purpose built Electronic Fuel Injection system. The results have been great, with increased driveability, torque, and offroad capability. It's pretty much stall proof now. 

 

Pinzgauer Electronic Fuel Injection (OLD)

2008 Update:

We now have vehicles on the road with significantly different components including a purpose built controller. I'm in the process of updating the page to reflect the current system. The old page still has some useful information for those wanting to build their own fuel injection, so by request I'll leave it available.

Extended service testing of our EFI system have gone very well. While we have not decided whether to release a kit, the system has been designed with that in mind and was one of the core design objectives. It had to be turnkey, easily installed by someone with reasonable mechanical skills, and most importantly OEM level engineering.

Until we do decide to release the system as a kit, here's some basics on EFI on the pinz, and our approach.

Introduction:

The Pinzgauer from the factory is equipped with dual Solex 2bbl carbs. They work great, and have excellent off-road capability. They do, however require regular adjustment and cleaning. It can be a trick to get them synchronized. And, like all carbs, they are at best tuned for a compromise of the current altitude and temperature, and will often be rich or lean. You also have the manual choke issue. Again, it works, but is at best a compromise.

Electronic Fuel Injection (EFI) has the advantage of being able to provide the engine with the exact fuel required for the current load. The tradeoff is electronic complexity for the existing mechanical/hydro-dynamic of carbs.

EFI is actually quite simple in concept once you understand the basics. The "Probst" book is a very good tutorial on how EFI systems work, and what the engine actually needs.

Offroad, EFI is very effective. Instant throttle response regardless of load, vehicle angle, etc. With the "off road cruise control" tweaks to the closed loop idle system, it's fantastic on trails.

We did not focus on HP increases, as the pinz engine has come specific engineering constraints that make it very difficult to increase HP. Instead, we focused on all weather drivability, torque, and responsiveness. In that aspect we have succeeded, as the pinz is much more pleasant to drive. No need to row the gears as much, and largely once up to 40mph or so you can stay in top gear except for stop & go.

The pinz has always been a bit finicky about hot starts, requiring slightly different procedure depending on temp, etc. Choking when cold was never an issue, but you did have to work the choke a bit as the engine warmed up. With EFI that all changes. regardless of temperature, crank up & drive away. We've tested down to 13 & up to 100 degrees Fahrenheit. The controller manages all aspects of startup with different settings for fuel, air, and timing for all phases of startup:

  • Priming- equivalent of patting the accelerator pedal with a carb vehicle

  • Cranking- Air, Fuel & Timing all set according to ambient temp, engine temp, & barometric pressure

  • Afterstart- first 30-60 seconds after start need extra richness

  • Warmup- Slowly taper down extra air & richness as the engine comes up to temperature

Another major benefit is no more fuel smell in the cab! Even freshly rebuilt carbs always allowed some fuel smell in the pinz due to the cabover engine placement. This simply goes away with EFI! So do the clouds of smoke from overly rich mixture at startup.

Controller & Wiring Harness

Purpose built controller dedicated to the unique pinzauer needs. This includes:

  • OEM quality wiring harness integration with the pinz factory wiring harness
  • No separate relays required or wiring forward of the engine
  • 24v pinz's still need a voltage equalizer to handle running loads, but the rest of the pinz electrical system is unmodified. By using an equalizer rather than converter the vehicle will still run, you'll just need to watch battery voltage. By using a 12v fuel pump replacements are available at any auto store.

Intake Plenum & Runners

The pinz is very constrained in the intake size/shape that will fit without significant modification. An existing pinz plenum design was modified to have:

  • OEM style injector location shooting at the head intake port
  • Intake runners matched to pinz rpm & volume
  • Plenum capacity matched to pinz displacement airflow & displacement
  • Use of widely available OEM throttle body
  • Integration with existing pinz vacuum system
  • Integration with existing factory air cleaner- This was a core design objective. The factory air cleaner is optimal for the pinz & excels at dust separation & water avoidance.

The plenum/intake is all aluminum, tig welded with machined flanges. Uses existing intake mounting hardware & air shrouds without modification

Fuel Supply- Pump, Regulator, and Filter

Conventional Bosch EFI design was utilized for the fuel supply. Standard Bosch components as found on Mercedes & BMW OEM systems. This includes:

  • High Pressure inline Filter
  • Mercedes approved hose & clamps
  • Bosch High pressure filter
  • Bosch bypass fuel pressure regulator
  • In tank fuel pump

Pretty much standard plumbing as used on 80's vintage European cars. Widely available components.

The pinz has fairly modest fuel needs, and no special fuel distribution approaches were required!

Throttle Body


Not the TB we use, just do not have a current photo		 A widely available throttle body was utilized with integrated TPS & Idle Air Control. Again, the pinz has fairly modest demands from an airflow perspective. Low RPM and small dispacement just does not require a large throttle body.

Too big, and you lose throttle response. IE: a very small movement and you are at Wide Open Throttle. Too small and you starve the engine a bit.

CFM needs of the pinz aligns with smaller but higher revving 4 cylinders and smaller V-6's.

Turnkey throttle cable attaches to the factory pinz throttle linkage, no modifications required!

Sensors

Sensor

Description / Source

Ambient Air Temp

(IAT)

 This one is easy. Plain jane GM parts. Cage type located in the factory air cleaner. This is used to set baseline mixture.

Coolant Temp

(Cylinder Head Temp)

 This is used by the controller to determine warmup state. As the pinz is air cooled you have to use either an Cylinder Head sensor or oil sensor.

The pinz oil volume & cooling is so overengineered oil temp is not an accurate indicator of engine operating conditions. So a CHT approach is used with a specific, but widely available bosch CHT sensor mounted in a factory approved location on the cylinder

Throttle Position Sensor

(TPS)

 

The TPS is used to communicate the following states to the controller:

  • accel- the controller temporarily enrichens to prevent "flat spot"
  • decel- for enleanment at zero throttle at higher RPM's
  •  Idle- Richer mixture needed at idle
  • Wide open throttle- Fuel/Ignition changes at WOT
  • Flood clear

Idle Air Control

(IAC)

 Engines need additional air during cranking & warmup. More modern vehicles utilize closed loop idle.

We have implemented full closed loop idle utilizing a widely available OEM IAC valve, with temperature compensated cranking & warmup RPM's, but steady idle once at temperature.

From there the functionality was extended with other fuel/ignition changes to make the pinz virtually stallproof. You can climb grades at the limit of traction, roll over logs, etc at idle without it stalling.

Manifold Absolute Pressure

(MAP)

 OEM style internal MAP sensor is used. Just run vacuum line from the throttle body. It's the most critical EFI input as it's the best indication of engine load. No external modules or wiring needed.

The MAP sensor is also used to determine barometric pressure which is another EFI variable.

Oxygen Sensor

 The O2 sensor is the critical feedback to the EFI system of mixture. We utilize a standard & inexpensive narrow band O2 sensor mounted in the header pipe.

The O2 sensor is utilized for cruise & decel portions of the map to run at "stoich" (Ideal air/fuel ration). Idle, heavy acceleration, and WOT have separate enrichments to accommodate the pinz's air-cooled requirements. 

Injectors

The pinz has modest fuel requirements and standard Bosch injectors are utilized.

Experience has shown that too big is worse than too small. The pinz does not need large injectors!

Distributorless Ignition

OEM ignition modules, coil, & wires were adopted. Several benefits to this approach:

  • OEM level robustness for the tone wheel/crank position sensor. No finicky wiring & sensor behaviors.
  • Limp-home capability- the ignition works even without input from the controller unlike systems with the EFI controller also fully operating the ignition. EFI controller just provides ignition advance/retard, the OEM modules do all the hard work.
  • Standard tach interface
  • Widely available components- all continents
  • Standard plugs including resistor platinum type can be used. You've never seen a spark like this on a normal pinz!

 

Links

Additional info on Pinzgauer EFI:

Photo's of Pinz EFI

  • Coming Soon!

Video of Pinz EFI

  •  Coming soon!