deckerfl
Well-known member
Hi Fellow TDI'ers,
I'm going to add CNG capability to my TDI, and was hoping to hear from others who have tried this on TDI's. Specifically, what Kit you used and your experiences with it, regarding installation, function and performance.
Most of the Kits I have seen are, as I understand it, mechanical in that a venturi is placed in the intake, before the turbo, and CNG is metered in based on the air flow going past the venturi (kind of like a carburetor). These kit, would likely be easier to install, and are cheaper, but there's probably no ability for finer control of CNG metering
The other method I've seen is an electronic ECU, which taps into Throttle and RPM signals for inputs and controls a stepper motor to control CNG metering into the intake (kind of like an open loop fuel injection). These seem to be a bit more expensive, but I imagine will allow finer control of CNG metering, if that is necessary.
I actually like the idea of the simpler mechanical system, but some situations worry me in that I'm not sure what the outcome would be. For example: say I'm on a highway, in gear at ~70mph, and I'm going downhill, I let off the throttle, so Throttle is 0%, but the downhill grade, is driving the engine, keeping the RPMs up, say at 2K RPM. Since the RPMs are up at 2K RPM, air is flowing into the engine at a higher ratethan Idle, would the venturi, be metering in CNG, thus fueling the engine, speeding up the car, and higher RPMs, leading to higher RPM's and more CNG, and so on leading to a runaway situation?
I guess I need to plug in my VCDS and log to Throttle, Airflow, and Diesel injected, (Maybe EGT too) to figure out the relationship between these paramaters under different engine loads and engine speeds.
Sorry for the long post, I'd appreciate and opinions and / or experiences.
BTW, the car is an '04 VW Passat TDI. These have the BHW engine, and an Auto transmission unfortunately, so i'll have to be careful with any increase in peak power output.
Thanks,
Dan
I'm going to add CNG capability to my TDI, and was hoping to hear from others who have tried this on TDI's. Specifically, what Kit you used and your experiences with it, regarding installation, function and performance.
Most of the Kits I have seen are, as I understand it, mechanical in that a venturi is placed in the intake, before the turbo, and CNG is metered in based on the air flow going past the venturi (kind of like a carburetor). These kit, would likely be easier to install, and are cheaper, but there's probably no ability for finer control of CNG metering
The other method I've seen is an electronic ECU, which taps into Throttle and RPM signals for inputs and controls a stepper motor to control CNG metering into the intake (kind of like an open loop fuel injection). These seem to be a bit more expensive, but I imagine will allow finer control of CNG metering, if that is necessary.
I actually like the idea of the simpler mechanical system, but some situations worry me in that I'm not sure what the outcome would be. For example: say I'm on a highway, in gear at ~70mph, and I'm going downhill, I let off the throttle, so Throttle is 0%, but the downhill grade, is driving the engine, keeping the RPMs up, say at 2K RPM. Since the RPMs are up at 2K RPM, air is flowing into the engine at a higher ratethan Idle, would the venturi, be metering in CNG, thus fueling the engine, speeding up the car, and higher RPMs, leading to higher RPM's and more CNG, and so on leading to a runaway situation?
I guess I need to plug in my VCDS and log to Throttle, Airflow, and Diesel injected, (Maybe EGT too) to figure out the relationship between these paramaters under different engine loads and engine speeds.
Sorry for the long post, I'd appreciate and opinions and / or experiences.
BTW, the car is an '04 VW Passat TDI. These have the BHW engine, and an Auto transmission unfortunately, so i'll have to be careful with any increase in peak power output.
Thanks,
Dan