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mk2

PD vs VE rotary diesel pump injection. No difference.

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I need convincing that there is an advantage with the PD or pump injection system compared to the electronically controlled rotary distributor type pump. I can't see it. I recently worked on both the old VE rotary pump as used on the SDI and golf TDI (1.9), and the 'newer' PD engines and simply don't get it. Personally I'd say the PD isn't as reliable since they are under much higher stress and they are exposed to higher temperatures, the wiring is inside the engine, plus diesel can leak into the oil. With the rotary system, everything is immersed in diesel, keeping components clean, lubricated and cool. No leaking diesel into oil. Wiring is only immersed in diesel, not potentially dirty or custard mixed engine oil.

They both pressurise the diesel using a cam, pushing in a plunger piston.

They both vary the delivery quantity by electronically adjusting the timing of a release port.

They both adjust the start of injection by using electronic valve control.

The nozzles that squirt the fuel in, are identical 5 hole injectors for both systems.

The pressure levels in the injectors reach the exact same 300 bar limit as set by the injector pin lift springs.

Anyone?

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ALH still seems like the best engine ever. PD have weaker valve train too because of the thinner lobes and extra stresses. Emissions maybe? Tighter fuel control? 

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Yeah (and SDI without a turbo=same). My guess is emissions are exactly the same because the injector nozzles are the same on a PD system.

Fuel control? Mmm, give or take a millisecond at high revs, I can't see that affecting much. More fuel in a diesel usually means more power, but yeah, you're right- if they inject fractionally earlier or later, it will affect smoke levels a bit. But then again, the timing control on VE system is pretty accurate too (sensed through injector 3 pickup), and adjusted via the PWM solenoid on the side on the pump.

The main things I don't like about PD, apart from the extra cam stresses and belt issues, is the fact that open bare wiring is bathed in engine oil. Not really a problem if it's clean or new, but you know what custard is like from lots of short start stop cycles. Very corrosive, acidic and has high levels of moisture. Not clever. Had a to fix a 3 cyl PD polo the other day where the wire to an injector solenoid had gone open circuit because of custard side effects.

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Never had a problem with the old Golf's AHF lump (330k on the clock), which after sitting for nearly a year in the yard after the clutch shat itself, fired up first time last weekend.

Would love to drop it in place of the trusty SDI before the Golf itself disintergrates and gets collected by the scrappy, but I have the task of finishing the Lupo's bodywork (amongst other things) a year after i last touched it, ho hum.

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More SDI pics? :)

Yeah that engine in the mk4 is a beaut. Really is. Shame about the bodywork on early mk4s. Same as my mk4. It's probably going to need welding this year. Both sills, all the way from front to back. Probably cheaper and easier to get another. Plus VED is expensive.

 

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I'll put some pics up later, none on my phone currently.

And your MK4 sounds like ours! Sills are completely shot at the front, last time i tried to jack it up it just crumpled into nothing, doesn't help with the liberal amount of salt they put on the roads here (thankfully the Disco is waxoiled within an inch of it's life). But yeah, it would be much much cheaper just to get another Mk4, the subframe is going, the steering rack is just about gone, but it still has it's original engine, gearbox and turbo! Only reason it hasn't made the journey into the afterlife is because the missus has owned it for over 15 years and can't bear to part with it (although it will be going beforelond :( ).

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The Lupo as he currently sits.

N7kSd6I.jpg

 

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