2008
Update: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 HarnessPurpose built controller dedicated to the unique pinzauer needs. This includes:
Intake Plenum
& RunnersThe pinz is very constrained in the intake size/shape that will fit without significant modification. An existing pinz plenum design was modified to have:
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 FilterConventional Bosch EFI design was utilized for the fuel supply. Standard Bosch components as found on Mercedes & BMW OEM systems. This includes:
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:
|
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. |
InjectorsThe 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
IgnitionOEM ignition modules, coil, & wires were adopted. Several benefits to this approach:
LinksAdditional info on Pinzgauer EFI:
