Possible economy tip, or daft?

[Aragorn]

As above, dervs are typically most efficient at or near full throttle around peak torque.

I see what you mean now about the revving and "more fun".

Reckless: You cant reduce boost pressure below the actuator level with a boost controller, only raise it! Most new cars have a low pressure actuator of around 5psi, and use an ECU controlled bleed valve to raise the pressure as required. With the defender actuator being rated to 15psi you cant use a bleed valve (manual or otherwise) to produce a level any lower than this.

[CwazyWabbit]

Nope. Start reading from here: http://forums.lr4x4.com/index.php?showtopic=82309&p=707426

.....

Thanks for the reminder, I had seen that before but forgotten it

[TheRecklessEngineer]

Reckless: You cant reduce boost pressure below the actuator level with a boost controller, only raise it! Most new cars have a low pressure actuator of around 5psi, and use an ECU controlled bleed valve to raise the pressure as required. With the defender actuator being rated to 15psi you cant use a bleed valve (manual or otherwise) to produce a level any lower than this.

Good point. I wonder how low the standard LR actuator would go? Then use a boost controller to bring it back to the standard level when you want more oomph.

[ian_s]

so disconnecting the boost pipe has blunted the effect of the turbo coming on boost? I may revisit the idea of fitting a solenoid to it for when SWMBO drives it then.

[vulcan bomber]

Certainly does apply on a TDi. Even my ancient 6hp Lister CS will go to no fuel on overrun. The injection pump has wizardry inside it to make this happen. Carburetted engines do not (hence the lovely gurgling noise on overrun).

So if thats the case how do you trundle along in 1st with no throttle and the engine doesnt stop?? I can assure you the VE pump as clever as it is, isnt that clever.

[Escape]

So first you had the pumped tweaked for extra fueling, and now you have disconnected the boost pipe to prevent it from adding extra fuel to match the turbo's air delivery? This would explain why the performance isn't too bad, it's now probabIy running close to standard tune. I guess you will see better mpg, but mostly because the pump was set too rich, hence the smoke. With the extra valve your planning, it would be like an oldskool equivalent to a powerbox you can turn on or off depending on the drive.

Withe regard to not using as much throttle instead, not sure I agree, as I can still rev to full revs now,but without any extra fueling, ie foot on the floor whilst accelerating with no smoke then back off when at speed. If it works mpg wise, I will fit a simple power 'tap'. I wouldn't want to tow with it like this but for most of the time it seems fine.

[TheRecklessEngineer]

So if thats the case how do you trundle along in 1st with no throttle and the engine doesnt stop?? I can assure you the VE pump as clever as it is, isnt that clever.

Because the idle governor adjusts the fuel rack to maintain the idle speed - effectively opening the throttle. If the engine speed is above the demand speed (on overrun going downhill or engine braking) then the fuel rack will be at the no fuel position.

I can assure you that this is not particularly clever and the Bosch VE does very definately operate in this manner - as does every other diesel with a governor. Which is all of them (bar a few funky early designs) electronic or otherwise.

When I have a few moments I'll dig out some references on diesel injection pumps and governors.

[Yostumpy]

So first you had the pumped tweaked for extra fueling, and now you have disconnected the boost pipe to prevent it from adding extra fuel to match the turbo's air delivery? This would explain why the performance isn't too bad, it's now probabIy running close to standard tune. I guess you will see better mpg, but mostly because the pump was set too rich, hence the smoke. With the extra valve your planning, it would be like an oldskool equivalent to a powerbox you can turn on or off depending on the drive.

I had the pump 'optimised' prob 5 years ago by van Aaken in Surrey. it did (and still does) GO like a scalded cat. However i came upon a website prob 2 years ago by accident. I google 'most efficient small van' as I was a bit miffed by my 26mpg avg despite a gentle right foot. The term hypermiling came up. Not something i'd ever come across ( And I'm 50+) so I read with interest. within a week i'd managed to drive from N.kent to Brighton and back on 2 gallons of petrol, 64.5MPG (std 2000MY yaris) . I've tried a few things now in the truck, and My best is 35.4mpg coming back from Dorset. My goal is to hit 40mpg. I'm NOT slow, I don't hold anyone up. (well maybe sometimes) and my avg after 22 fill ups is 29.2mpg!

The pump was NOT set too rich, and it didn't emitt plumes of smoke, but all tdi's smoke on acceleration, Mine now doesn't. AT ALL!!! that must mean its not using as much fuel. but whether its more efficient , only time will tell.

Old skool power box thing is spot on, power only when needed, BUT ONLY if I get net MPG gains, otherwise there is no point.

[Yostumpy]

so disconnecting the boost pipe has blunted the effect of the turbo coming on boost? I may revisit the idea of fitting a solenoid to it for when SWMBO drives it then.

Yes and no. it is a simple 3 min jobbie, pull off the pipe, plug it with a srew, push another bit of pipe on, plug that with a screw as well and Bob's prob not your uncle. It's strange really, hard to describe. Its better than a n/a by a long chalk, (especially as I've got a std 1.410 T/Box and the n/a had the 1.610) It does go very well considering, and I'm sure the turbo is helping even without the boost fuelling as 2.5 n/a with a 1.41o box wouldn't accelerate to 75+ with more to go. I've been using it today, and already I'm forgetting that its got less power. so when I flick my switch its going to be like Nitros!!!!!!! I'm only in Gravesend, if you want to pop over for a spin some time then send me a pm. But bear in mind your series will be quicker and more economical in this mode. Gosh i hope there is SOME improved mpg after all this, other you can all call me 'egg face' or Mungo! yes I like Mungo.

[TheRecklessEngineer]

Further to my earlier promise, here's some detailed tech on specifically the Bosch VE and injection pumps/diesel fuelling control in general.

Note that two types of governor are available for the Bosch VE. A min/max and variable speed. Vehicles are fitted with a min/max type - it will regulate the idle speed (effectively varying the fuelling to maintain an idle) and it will cut the fuel at a rev limit to stop the engine self destructing.

To start with, a good video showing a very basic single speed governor. The Bosch VE is more advanced than this:

And here's a link to a detailed description of a Bosch VE pump:

http://mebonty.monobasin.net/vepump.html

What I'm referring to above as a fuel rack Bosch seems to call a control sleeve. I'm used to much bigger diesels with non rotary injection pumps - where it's referred to as a fuel rack. The link talks about the governor, but some of the images are broken. Over run isn't mentioned, but it does talk about the operation of the idle governor.

An interesting excerpt from this one:

http://www.ebah.com.br/content/ABAAAfAEkAL/bosch-ve-pumps-manual?part=6

It's part of the Bosch VE manual with a detailed description of the governor mechanisms. From the section specific to overrun

"During downhill operation the engine is “driven” by the vehicle, and engine speed tends to increase. This causes the flyweights to move outwards so that the sliding sleeve presses against the tensioning and start levers. Both levers change their position and push the control collar in the direction of less fuel delivery until a reduced fuel-delivery figure is reached which corresponds to the new loading level. At the extreme, the delivery figure is zero."

This one is good for general diesel theory, although the source is dubious.

http://www.vegetableoildiesel.co.uk/forum/viewthread.php?tid=123

"The fuel injection on a diesel is based on engine load. Within the pump, there is a spring that the accelerator cable actually pulls on. Opposing the force of a spring is the centrifugal regulator. The actual movement of the junction of the spring and the regulator determines the amount of the fuel injected. Thus, if the engine is kept loaded so it can't really increase its rpm, only a small pressure on the accelerator will actually open the fuel to the max. As soon as the revolution rises, the centrifugal regulator will start countering the added force to the spring and close the fuel, until the engine rpm matches the force of the spring. The maximum force on the spring (and thus the maximum rpm you can request) is simply limited by a limiter that prevents the accelerator cable to pull on the spring more than to a certain limit."

And a nice little video demonstrating the max fuel governor (note the control arm must be in the maximum fuel position for this demonstration - there's no idle governing going on here)

So hopefully from the above, you can see that when your foot is off the pedal the control arm on the pump is in the idle position - the control sleeve position and hence the amount of fuel being injected into the engine is regulated by the governor inside of the pump. If the engine speed is greater than the idle speed (i.e. on overrun) the governor will by it's nature will push the control sleeve to the no fuel position. As the engine speed approaches idle, the governor will move the control sleeve to start injecting fuel again picking up the idle before the engine stalls. Likewise, if you put an engine at idle under load the idle governor will attempt to maintain the idle speed by moving the control arm to compensate.

[Retroanaconda]

Very interesting. So in a way there is a basic form of anti-stall built into the injection pump?

[TheRecklessEngineer]

Very interesting. So in a way there is a basic form of anti-stall built into the injection pump?

Yes, exactly. The modern electronic forms are better as they use a 'feed forward' technique to guess at what the engine loading is about to be. A mechanical idle governor is only ever retrospective in it's response - and won't ever raise the engine speed beyond idle.

[Yostumpy]

just been conversing with another chap on (that eco website) another forum, he has a 6.5 gm deisel, set up to run as n/a, then later he added a turbo, without upping the fuelling with a boost pipe. he got a 2 mpg gain on daily runs, and about a 3 mpg gain, ona run. But hes is only getting about 18mpg (us) to start with, so not much help there. Cant wait to fill up, except my journeys this week, and prob next, are limited to about 2 miles each way and back, and back, and back, etc. so not a good test.

[jad]

At one point in my 200tdi defender 90 the diaphragm in the fuel pump was stuck solid and was not moving at all under boost. I would still register 0.5 Bar of boost but it was terribly slow, like painfully slow..... Was having to change down into 3rd to go up some hills along the A303 and was getting down 25/30mph from memory. I did however manage about 340 miles from a tank which equated to about 33/34mpg after correcting for tyre size.

Jad

[Yostumpy]

Ok another update. filled up at 190 miles, 75 of which were local running about, rest a trip down to margate...... Not as good as i'd have hoped, avg was only 30mpg. i think the lack of extra grunt that the turbo gives with the extra fuelling , means longer in gear getting up to speed, whereas best way is hard and quick. i shall give it one more then put the pipe back on. If I comuted a set distance,every day I could do some more acurate a-b-a testing. So ultimately it looks like a no go. Shame really.

[Yostumpy]

having reflected on this, 30mpg is not to be sniffed at, and the road down to margate is flat, 2 years ago i'd have sold my granny to get 30mpg, and now its not enough? oh dear. I think that without its extra fuelling the optimum speed on t'open road is about 62mpg, whereas with fuelling happy at 56mph. Its lovelly to drive in both modes, Oh why don't I have a proper regular job, .say 30 miles away!

But then 75 miles of ithe tank was very urban commute, t/lights,1/ 2 mile trips to wickes etc.

[Yostumpy]

decided to look at this another way? A mathematical way, say 190 miles tot , with 75 very localised urban driving.

75 is APPROX 1/3 of total, therefore say....... 75 miles at 28.0mpg

therefore 28 + 31.5 + 31.5 =91 divided by 3 ................= 30.3mpg


so one can assume that my trip to margate netted me about 31.3mpg which brought up the lower comuting avg. Still awake!!!