Inside the VP44

[CRC]

Not really having a clue what goes on inside the VP44, I found this thread the other day which suggests that the inside of the VP44 is not really a place for the average DIY mechanic to find himself ......

http://www.competiti...ead.php?t=80602

[rotodiesel]

I've banged on about VP44 problems in the past, so I'll keep it brief:

Anyone in the diesel business will know from my user name that I have worked with radial piston rotary pumps for export from the UK. Originally subject to a Hartridge patent, the radial as opposed to the axial piston pump design allows higher fuel pressures for a given cam loading. Bosch could therefore only produce a radial piston pump when the Hartridge patent expired - and the VP44 was born.

There are two major issues with the VP44, one mechanical and the other electrical. Mechanical problems are caused by poor design and material choice, especially in the area of the cam advance mechanism. Electrical problems are caused by thermal cycling and vibration (notice the flexi connector in the link - this is inside a diesel filled pump running in the Vee of an engine). The semiconductor driver devices inside the pump and their bonding wires are also prone to failure - some of our our East European friends have devised a work-around for these failures.

By contrast, the PD system has no electronics on the engine, oil lubricated followers for the fuel elements, allowing vastly higher injection pressures than a fuel lubricated VP could ever deliver and precise control of injection timing referenced directly from the crank via a tone ring at the flywheel end. This means the timing never needs to be set, does not change (even with belt changes/stretch) and gives precise governing.

The relative engine performances in terms of specific fuel consumption and emissions (compare the tax brackets and performance of a V6 and 1.9/130 Superb) speak for themselves. The VP44 was an over development of an obsolete technology which Bosch adopted too late because of patent restrictions. The company I used to work for knew how to make radial piston rotary pumps which lasted (although they might leak a bit...).

rotodiesel.

Edited 11 June, 2013 by rotodiesel

[dieselV6]

Guys, are you trying to talk down the 2.5V6 diesel so that you can bag a cheap bargain?

Yes, PD in theory was supposed to be more reliable, certainly provides higher injection pressures, but once again, in real life there is a (not so) small matter of 3000+ engines requiring expensive PD pump-injector unit replacements in one country (Germany), in a single winter, against low fraction of a percent VP44 failures on BDG and later engined 2.5TDI VAG group cars... Given the extra refinement, comfort and speed, I'd take VP44 any day over the PD units if the car is to be owned from start till end. Though to be fair, CR is even worse in this respect, hence I am keeping the Mk1 2.5TDI Superb for as long as I can.

That, and I have just come back from a half term trip (1200 miles each way), car full of stuff, towbar carrier box, 4 people and the 2.5TDI would still happily cruise at 135mph+ on the autobahn. Even a remapped 1.9PD just cannot do it for long periods of time, head gasket will let go eventually (a few years). My 2.5TDI VP44 equipped Superb just passed MOT, smoke test on fast pass, and at 120k miles/7 years it feels like it's only halfway through its working life. I think it's far more important to have the car fuelled and maintained properly and base engine choice on whether you want/need the extra power/speed/refinement that the 2.5TDI offers over the 1.9PD.

[CRC]

I'm not trying to talk the V6 diesel down .... I own one and love it.

Mine gives excellent power and mpg, both below the turbo cut in and above it, but there are increasing numbers of folk coming on the forum who seem to be suffering from poor mpg / smoking / low power below the turbo cut in etc, and I suppose this post was really a wake up call to show that, given the complexity of the VP44, yer average mechanic is not going to be able to fix any problems that the VP44 may throw up, regardless of what he tells you.

Should you have a VP44 problem, it really is worth checking out the capabilities and the test equipment of the company who claim to be able to fix it, before you part with your hard earned cash.

The complexities of the advance piston and solenoid were quite an eye opener, and if the pump doesn't advance properly then the fuel won't burn properly?

[rotodiesel]

The PD injector recall did not apply to the 1.9/130 which uses Bosch electromagnetically actuated unit injectors. It applied to the Siemens piezo injectors fitted to the later 4 valve 2.0 PD engines - which the Superb never had.

VAG had to be kicked into recalling them in the UK. Briefly (again) the piezo injectors are high voltage devices powered from an inverter within the ECU. VAG clearly forgot that old diesel engine oil is full of soot and therefore conductive (all unit injectors are inside the engine). When oil gets into the piezo stack, the inverter is overloaded and shuts down for its own safety. The engine then stops dead - in the fast lane - no power steering - no brake servo after vacuum runout. Great stuff.

The Bosch electromagnetic injectors in the 2 valve 1.9 are highly reliable. I have tested engines with over 200k miles in which all of the IQ values are within original tolerance. The connecting looms sometimes fail (cheap in situ job) but I have seen very few injector failures.

VAG caught cost cutting (again) in my view.

rotodiesel.

[vk10]

I own the same 2.5tdi v6 as you all know from my last thread, even after pouring money down its throat, new vp44 pump timing water pump service etc etc, still trying to find a way of reducing 1 the smoke on even slow acceleration let alone foot down (that will make the road look like black clouds) 2. My trips to the petrol station. Couple of years ago I owned a gs300 and for some reason the economy on the superb and the old Lexus feel the same.

The pump timing is at 0.6 ATDC. Morning starts are perfect first crank.

Given my fantastic experiences,I wouldn't recommend the 2.5tdi anymore. But again that's my personal view iam sharing. There are some people who recommend remapping it but I can't see how that would help.

The vp44 is a complex design seeing that after doing a lot of research on it, there are very few in the industry who would want yo touch and get give you only 12 months guarantee.

Maybe at the back of their head they know its going to go pip again. The thought if it gives me nightmares. For now Il just head to the local bp round the corner to fill up.

[dieselV6]

Well, if it is still smoking and using too much fuel, perhaps pump was OK but injectors are shot, or more likely both were shot in the first place due to using bleached agro fuel or some other "inventions"? Or turbocharger / VNT adjustment mechanism is sticking? Or EGR valve is stuck? Common on former taxis.

I understand your frustration, but keep in mind that from previous posts it appears someone happily sold you a lemon and then servicing was not much better, happened to me in the past and since then I buy cars new and run them till the end, with DIY servicing. I have been driving my 2.5V6TDI for the last 7 years from new, never have let anyone mess with the engine, DIYed the belts and oil+filters servicing (plus a few CV boot jobs), and it runs perfectly at 120k miles. I am not the only person with this experience here on the forum, and there were cars with double my mileage still running just fine.

Edited 16 June, 2013 by dieselV6

[vk10]

I completely agree with you, but as i said I was just expressing my own views on this one!, the reason i did buy a 2.5tdi v6 was because my cousin owned a 52 plate one a few years ago and driving that was a pleasure. But for the some reason the one I have simply does not match up to it & and makes me regret selling my cvt 1.9tdi. (yes i know the word cvt may just open up another thread)

As for buying new cars, Iam not in a position to afford it which is why i went for a used one. But yea point well taken where i have been sold a lemon but it all comes to the same point, its put me off this particular engine on the whole. The other aspect being, this tiptronic under engineered over revving auto box. Would be fantastic in a 1.9 tdi but the person who decided to give it to the 2.5tdi probably was in a hurry to get back home as it was a Friday afternoon engineering.

I look forward to seeing you people at the annual meet where your more than welcome to drive mine and give your reviews on it!

Last but not the least I do want to add this, Had it not been for you guys on this forum helping me out at each step to get this car driving, i would have scrapped the thing in March itself. So Cheers for that.

[rotodiesel]

Thanks for your good wishes - returned.

Although I rejected the 2.5 as a tow car at an early stage due to its engineering limitations, when I test drove a couple of these (one manual, one auto), my immediate impression was that the transmissions were not matched to the engine. Both could do with a taller top gear (what's the point in buying the extra torque if you can't make good use of it) and the slush box would have made an uphill start with a loaded trailer unspectacular or dangerous - depending on traffic conditions. The light "throttle" (there isn't one) change points are also far too low - did they forget this engine is turbocharged?

A good Independent diesel specialist is the only way to make the best of a VP44. Some of the shortcomings have been "fixed" - officially and by unofficial means, but the basic principles and the electronics within it make it a high risk item - for not a lot of fuel pressure.

rotodiesel.

[vk10]

I agree, gearboxes are nowhere near to being matched plus the awkward converter lock In on 3rd gear makes it annoying at times and makes me think I have a 6th gear which it doesn't. I would add the heavy engine does make the handling suffer on bends but at the same time,is fantastic on rough roads and eats all the potholes you find in the roads these days. What is your view on an economy remap for this car

[CRC]

I reckon there's a bit more to the remap of the V6 than meets the eye, the reason being that the VP44 has its own FPCM (Fuel Pump Control Module). As far as I can make out from the link below, the main engine ECU computes the fuel requirements based on current operating conditions and sends that information to the FPCM on the VP44 and this then should supply the fuelling as required.

If the VP44 is already having a problem supplying the fuelling as demanded by the standard ECU, then it's still going to have a problem supplying the fuelling demanded by the remapped ECU.

If the engine smokes under normal, light footed driving and the mpg is poor, then something is adrift, and if the ECU is standard and showing no faults, the static timing is correct on the VP44, then you kind of have to suspect that the VP44 is not quite doing what it was designed to do and is injecting more fuel than it should at the wrong time.

VK10, do you find that your maxidot average mpg on setting 2 is close to what you are currently measuring, or is it way out still?

I'm not exactly sure how the flow rate of fuel is measured, but think that it's probably calculated in the VP44 as one of the test computer screens on the original link shows a cubic milllimeter value for each cylinder.

http://dodgeram.org/...sl/ISB/Vp44.htm

Edited 17 June, 2013 by CRC

[vk10]

Interesting bit, was,in euro car parts 2 days ago and purchased this bottle of cata clean, put it in with 15 litres of fuel and gave the car a bit of thrashing. Result is mpg is now at 35.2 mpg mixed driving and smoke has reduced. Crc the mpg is off the setting 2. I'm thinking whether its worth going for revo stage 1 remap. They do a trial for 5 hours as well.

[Cown]

I reckon there's a bit more to the remap of the V6 than meets the eye, the reason being that the VP44 has its own FPCM (Fuel Pump Control Module). As far as I can make out from the link below, the main engine ECU computes the fuel requirements based on current operating conditions and sends that information to the FPCM on the VP44 and this then should supply the fuelling as required.

If the VP44 is already having a problem supplying the fuelling as demanded by the standard ECU, then it's still going to have a problem supplying the fuelling demanded by the remapped ECU.

If the engine smokes under normal, light footed driving and the mpg is poor, then something is adrift, and if the ECU is standard and showing no faults, the static timing is correct on the VP44, then you kind of have to suspect that the VP44 is not quite doing what it was designed to do and is injecting more fuel than it should at the wrong time.

VK10, do you find that your maxidot average mpg on setting 2 is close to what you are currently measuring, or is it way out still?

I'm not exactly sure how the flow rate of fuel is measured, but think that it's probably calculated in the VP44 as one of the test computer screens on the original link shows a cubic milllimeter value for each cylinder.

http://dodgeram.org/...sl/ISB/Vp44.htm

That's interesting. Would explain why additives seem to have a huge impact on this engine.