greg123
Veteran Member
Hi,
This isn't a mpg thread. It's a thread regarding the efficiency of the PD which seems to be less than the VE. For the same car, with a PD the CO2 emissions are higher than VE (indicating more fuel burnt) and mpg real world is between 5-15mpg less.
BUT - it's more or less the same engine and runs very well/clean. Just higher injection pressures and atomisation which shouldn't, by it's self, be a bad thing.
So - what's causing the issue?
I have heard it said that the PD injectors take a lot more moving, more spring pressure and more resistance on the cam. This would add friction loads to the engine. HOW much different it is to a VE pump I have no idea. Same tyres/car/transmission maybe someone has a dyno figures for the engine drag on coastdown from a full power run?
Ignoring the above it's my thoughts that the catylist and exhaust may be more restrictive. So (if legal where you are) a large bore race exhaust would fix that.
Also I think the tune was set up for NOX etc, deleting the EGR & looking with a chip tuner at how far the timing advance can go before it gets too advanced would be interesting. I hear the PD runs way off optimum timing, too retarded, for EGR and NOX purposes. The PD doesn't even sound 'crisp' like a well set up VE, it sounds muted which smacks of too retarded.
Then how about reducing the injection pulses to single pulse or two stage? A bit more noise, but fuel in earlier with longer time to burn and mix.
Can anyone think of anything else and has anyone gone down any of these routes? Has anyone got any g/kwh figures for the best TDI, the late euro 110tdi VE, compared to a typical PD say a 130PD?
Greg.
This isn't a mpg thread. It's a thread regarding the efficiency of the PD which seems to be less than the VE. For the same car, with a PD the CO2 emissions are higher than VE (indicating more fuel burnt) and mpg real world is between 5-15mpg less.
BUT - it's more or less the same engine and runs very well/clean. Just higher injection pressures and atomisation which shouldn't, by it's self, be a bad thing.
So - what's causing the issue?
I have heard it said that the PD injectors take a lot more moving, more spring pressure and more resistance on the cam. This would add friction loads to the engine. HOW much different it is to a VE pump I have no idea. Same tyres/car/transmission maybe someone has a dyno figures for the engine drag on coastdown from a full power run?
Ignoring the above it's my thoughts that the catylist and exhaust may be more restrictive. So (if legal where you are) a large bore race exhaust would fix that.
Also I think the tune was set up for NOX etc, deleting the EGR & looking with a chip tuner at how far the timing advance can go before it gets too advanced would be interesting. I hear the PD runs way off optimum timing, too retarded, for EGR and NOX purposes. The PD doesn't even sound 'crisp' like a well set up VE, it sounds muted which smacks of too retarded.
Then how about reducing the injection pulses to single pulse or two stage? A bit more noise, but fuel in earlier with longer time to burn and mix.
Can anyone think of anything else and has anyone gone down any of these routes? Has anyone got any g/kwh figures for the best TDI, the late euro 110tdi VE, compared to a typical PD say a 130PD?
Greg.