Understanding injection pumps and VGT's

[darthdicky]

Trying to get my head around how these pumps work, and how people get on with swapping a standard TDi turbo for a VGT model? Did your fuel consumption increase massively?

What "inputs" does the pump know about to understand how much fuel is required?

Background to this is my 90 has a TGV engine installed and ever since I've had it, it's been heavy on fuel and not as powerful as I'd hope (although fully understand its limitations comparing with modern vehicles, and it's got an autobox). The boost pin is turned as far round as it can, but I'm wondering if that's just throwing in more fuel than it can deal with given that it's seeing 100% boost pretty much all the time I'm on the throttle?

It doesn't throw out loads of black smoke, EGT's aren't too bad, generally runs fine. The injection pump was rebuilt a few years ago by a specialist with supposedly a VGT specific setup, I'm just trying to get my head around how I might make it 1) a bit more powerful to maintain speeds up longer hills and/or 2) slightly more efficient when sat at 55-60mph on the motorway. Tempted to get it put on a rolling road but ideally need someone who really knows these pumps to get the best out of it - so any recommendations welcome.

[TSD]

There's a few decent articles on the web explaining how the pump works, but the Bosch training manuals are a good starting point.

BOSCH_VE_PUMPS.pdf

TGV will always be at or close to maximum boost if you're on the throttle at all. It's an effect of strapping a VNT to a simple mechanical control system. It really needs electronic control (or a much more complex mechanical system) to get all the benefits of the VNT. I looked into it in detail when I installed my TGV, but that was a lot of years and miles ago, so I freely admit I'll struggle to put much hard science behind that statement!

This has consequences - in light throttle cruise the pumping losses are increased (because it's always on boost) so cruise fuel economy must be slightly worse than the same engine with a conventional turbo. Also, when you turn the boost pin, the effect is less noticeable on the road, because constant boost means the diaphragm and boost pin don't really move. The extra fuelling is there, but because it's there all the time you don't feel it coming on in the same way. I suspect that, at cruise, the extra fuel from tweaking the boost pin just means you come off the throttle a little more, and end up pretty much burning same amount of fuel for the same amount of power.

There are other adjustments that can add power and torque, but that's outside my experience. One of @vulcan bombers 'boost' rings might be interesting to try - I've not heard of anyone fitting one of thise to a TGV up to now.

If you are loosing speed on long hills, and the EGT looks 'not too bad', then I would have a long hard look at the lift pump if you haven't already. When the original factory pump started to fail, I couldn't find a TDi pump that could keep up, and the Ibex really struggled to get over 70 on the flat. I fitted a low pressure electric pump and instantly top speed returned to much more exciting numbers.

From memory (and as I said, it was a looong time ago now) when I put the TGV in, fuel economy stayed about the same as the tdi I took out. I was driving a lot of miles then, but there was very little motorway cruise, so I might well not have noticed a change in cruise economy. I think these days I probably get around 28mpg with much more cruising, if that's any comparison for you (SWB Ibex, on 33" with Roverdrive).

[miketomcat]

Having driven TSD's ibex back to back with mine (tgv v 200tdi) I can confirm economy is the same although there is a tendency to work the engine harder rather than stir the gearbox. As for power it's not that much quicker, it'll see about 10 mph more than mine and it's a bit quicker accelerating. What it does have though is a mountain of torque. There's a couple of fairly steep hills on my commute the tgv will pull them in fourth mine needs third both with spirited driving. As for towing well it's about the same difference between 2¼ and a 200tdi but obviously higher speeds. Our ibexes are quite similar both on 33's with a 1.4 transfer box and r380 v disco lt77, Dave's is short wheelbase so a little lighter than my long wheelbase.

Mike

[fmmv]

The auto box will absorb quite a bit of performance. Might be worth checking the pump timing, I don't know about TGVs but 300s seem to like a bit more advance. Plus of course what was said above.

[vulcan bomber]

The spacer ring I sell will allow the timing to advance further, this makes the engine more responsive above about 2000rpm, I don't know what power or torque increase you get from it but it's noticeable. It will work on all Bosch VE pumps. 

 

I've never looked at the TGV pumps but I'd be interested to see what the part number on them is to find out where they differ. 

 

As a general, if you think your engine is struggling, give it a good going over, set the tappet gaps, filters, clean the intercooler out etc. it all adds up.

[TSD]

I don't have the pump number to hand, but I can find it at some point. It is certainly different (as you'd expect) as International have different part numbers for the pump for the 2.5 (with regular turbo) and the 2.8 (with VNT).

Worth noting that fitting a boost ring will be probably be a bit more involved than on a Tdi. The pump is mounted vertically on the TGV, so I imagine it would have to be removed from the timing chest to get access.

[Nonimouse]

Bearing in mind the standard 200/300 pump is capable of delivering enough fuel to take a 200 up to 180bhp (source Andy Graham) as are the injectors, although Land Rover France managed 250bhp in their LR 90 project, I don't think the pump isn't man enough. The lift pump has a perfect point in it's mounting, with the spacer needing to be 8mm, more or less can dramatically effect the flow.

I've witnessed Richards TGV not being a TGV. It sounds like it's bogging down, but it doesn't emit unburnt fuel at the time, so I'm loathe to say it's timing. With it's nigh on appalling fuel economy, I would suggest it's burning fuel quite happily (it really doesn't emit black smoke) I've suggested before that he swap a standard Garret T3 on and see what happens. If that's better then bin the VNT and go Audi 2.5 Turbo, or bin the pump and fit a EDC pump off a 300turbo, so that there is a a boost demand signal

[TSD]

You are assuming the TGV block has a boss machined with a deck height to take a Tdi lift pump, and that the cam has the same base circle to drive it. (The engine wasn't built with a LR pump from the factory, just a similar looking one.)

I don't know and I didn't care enough to find out - I tried a couple of pumps and things got better but not fixed, so I just fitted a Facet as an experiment. Everything got better instantly, so I left it there.

The lift pump 'should' only be an supplement to the lift pump internal to the FIP anyway.

Which reminds me that it's worth checking the pressure regulator in the FIP isn't stuck - I had one that was stuck solid on one pump. Could give some odd results if it were sticking part-way?

[Nonimouse]

Fair points

Over the years I have often thought of fitting an electric lift pump, so I'm already sold on the idea. I did look at the International 3.o litre last year, as fitted to the Ford Ranger (in very rare cases) and that looked to have the same lift pump as the 200/300

I still reckon fuel starvation isn't the problem - simply because he's using so much. Far more than a tweaked 300 Auto Disco

[landroversforever]

If it’s lacking go-go…. But using lots of fuel, surely that means it’s time to check the timing to rule that out? Then it’s down to boost?

[TSD]

If it's starving for fuel at high throttle demand, and someone has tried to get the performance back by upping the baseline fuelling, then it could be the case that cruise fuel is too high, but not yet hitting the smoke limit, but there isn't enough left to give it some real top end grunt. That's sort of what led me to thinking of the FIP intake regulator.

Every time miketomcat uses my Ibex, I end up quizzing him about the performance and handling, because I've owned it so long, and driven it so far, that I'm not sure I can tell if it's 'right' any more. It is, I'm sure, well down on power from when it was new, but probably not as down as I suspect on the days when it 'feels' slow.

[TSD]

One question I probably should have asked - is this a real TGV, or one of the 300tdi conversions?  I'm not sure its relevant to the problem, but there are some differences.

[Ed Poore]

@TSD I don't think it's a conversion but I might be wrong.

I've followed Dicky over a fair few miles both on and off road and pretty much ever since I've known him he's always found the performance to be a bit lack lustre. By comparison my 300Tdi 110 running 33" tyres coupled with a 1.2 transfer box (tall gearing) will out accelerate his with ease in pretty much all scenarios.

I'll echo what others say and it's always been a very clean and smoke-free vehicle. I think he's had the timing and pump checked over in the past by someone and they were given the all clear. However I don't know as to the "quality" of those people and whether they know all the TGV specific stuff (if indeed it is relevant).

I was just thinking through all the basics (good compression etc)., and the only thing I've come up with is could slightly loose valve clearances exhibit these symptoms? To my knowledge Dicky hasn't checked them but then I might not be aware if he has.

[Snagger]

I doubt it’s timing - retarded gives black smoke and advanced gives grey/blue.  It might be slightly off, but even if it was, it should easily output a regular 300.  If it was induction related, I’d also expect black smoke, so I doubt it’s the tappets, filters or pumps.  I think it sounds fuel related - low fuelling is the only scenario that gives low power without increased smoke.

I’d look for a leaking boost pipe from the compressor to boost diaphragm housing, a perforated diaphragm, a stuck pin in the diaphragm housing wall (the one that runs on the slope of the boost pin) and the fuelling settings, but checking all those other induction elements is prudent anyway.

[miketomcat]

There is one thing that stands out here. No one has said auto box, now I have a passionate hate of autos so I'm biased but what if all the gear changes were in the wrong place for a tgv or it was never fully locking up. That would give all the symptoms and might not be noticeable past the crushing disappointment noise.

Tgv has lots of torque so can pull higher gears so a box/t-box set up for a 300 might be to low geared.

If your running 33" try putting 35" on or indeed I might be completely the wrong way round and it needs 31".

Mike

[Bowie69]

Which autobox and convertor is it using? 

Mike, I'll have to show you 'disappointment' in LGT some time

 

[Ed Poore]

Autobox is a hydraulic 4hp and I think 1.4 transfer box with 33" tyres so shouldn't be an issue with gearing.

I think and Dicky might correct me here but it does lock up the box correctly at the expected speeds.

[toenden]

I know nothing about tgv's BUT on the autobox note, I did experience that my engine (300) "suddently" were able to smoke black going from auto to manual in my 110". Nothing else altered and it ran the same manual pump on both gearbox setups. At the time I put it aside as the autobox keeping the engine in a "good" revband versus the manual box (err, me) working the engine outside its best working revrange.

/mads 

[Snagger]

45 minutes ago, miketomcat said:

There is one thing that stands out here. No one has said auto box, now I have a passionate hate of autos so I'm biased but what if all the gear changes were in the wrong place for a tgv or it was never fully locking up. That would give all the symptoms and might not be noticeable past the crushing disappointment noise.

Tgv has lots of torque so can pull higher gears so a box/t-box set up for a 300 might be to low geared.

If your running 33" try putting 35" on or indeed I might be completely the wrong way round and it needs 31".

Mike

I thought about that, but there were comments about the engine sounding sluggish and like it was labouring, which I doubt would be the case if the TC was slipping too much.  It’s not impossible that another internal transmission is sapping performance, like some of the clutch packs dragging, but I’d expect black smoke, at least thin, from the engine labouring and would expect to see cooked and contaminated ATF.

[muddy]

To me it sounds like the VNT coupled with the auto is keeping the VE on boost demand all the time even when cruising.

As a 'power' test I would expect you to be able to sit at 80 with that gearing. My old 300 auto disco circa 280k on 235/85 tyres would certainly sit at 75-85 and that only had a pump tickle, you just had to get the TC locked up and then steadily build the speed.

My gut feeling would be to give it a service, make sure the valve clearances are spot on, check for dragging brakes, bearings etc and then fit a 'cone' filter pretty much directly to the turbo so you know there is no intake restriction. Are you measuring EGT pre turbo? are you measuring boost at the intake manifold? I would 'tune' to around 800 degrees c EGT under sustained heavy load and approximately 1.5 bar of boost at the inlet manifold with a smoke haze. once there you could try advancing or retarding the timing until you get the best performace and then dial back the fuel for safer EGT and hopefully better MPG.

Im not saying any of that is right or proper that is just what I would do. My 300 manual 90 ran 1.5 bar of boost (probably a little too much for turbo efficiency) and would hit 1000c EGT if you felt like working it hard, yes it smoked but it went pretty well, sit at 70 with an empty 16' Ifor and would do about 90 before you felt like the throttle was just a noise switch.

 

 

[TSD]

32 minutes ago, muddy said:

To me it sounds like the VNT coupled with the auto is keeping the VE on boost demand all the time even when cruising.

No, as said at the top of this thread, it's on boost all the time, because it's a VNT with a simple minded controller. It uses boost pressure to control the VNT mechanically, but I suspect there isn't a straight relationship between the VNT 'angle' and the output of the turbo, so it is only ever 'right' at one point (or very close to it).

My TGV will produce boost while parking. In motorway cruise it will indicate around 15psi and 20 at full throttle. Mash the pedal in the midrange and it will spike higher. So much so that I can't be specific about the boost numbers because after 200k+ miles it has actually bent the needle on the VDO and it now permanently indicates a few psi of vacuum with the engine off

 

[toenden]

2 minutes ago, TSD said:

No, as said at the top of this thread, it's on boost all the time, because it's a VNT with a simple minded controller. It uses boost pressure to control the VNT mechanically, but I suspect there isn't a straight relationship between the VNT 'angle' and the output of the turbo, so it is only ever 'right' at one point (or very close to it).

My TGV will produce boost while parking. In motorway cruise it will indicate around 15psi and 20 at full throttle. Mash the pedal in the midrange and it will spike higher. So much so that I can't be specific about the boost numbers because after 200k+ miles it has actually bent the needle on the VDO and it now permanently indicates a few psi of vacuum with the engine off

 

...Thats just the engine holding its breath before the next beating... 🙂

/mads

[Nonimouse]

This is Trembath's old bus, so I think it's a genuine TGV

 

Rich, just a question: Have you checked the on boost diaphragm is able to move - I've even seen these full of oil

[muddy]

5 hours ago, TSD said:

No

 

Yes, I think 🙄

What I am trying to say is that because the turbo is making boost all the time surely the boost control in the pump is going to be constantly trying to deliver the increased fueling?

 

[vulcan bomber]

Yes the injection pump only cares about boost pressure to adjust the fueling. It's a bit daft because boost pressure is only really the ability to get the air into the cylinders not the amount of air that is actually there. Just like an air compressor, it might deliver a million psi, but start painting and your going to run out in not time because the compressor can't keep up with a paint gun.

We use boost and talk boost pressure because it's easy to measure.

 

The 2.8TGV turbo is again controlled with boost, which is about the worst way to control a VNT, it means when your cruising the turbo is trying to make more boost than you need which means the Veins in the pump are creating a restriction in the exhaust and the dreaded "back pressure".

 

There's a good reason why most VNTs are electronically controlled.