Kill Switch (EOC): Where did you install your activator? And what did you use?

[paulgato]

I'm struggling to get my head around what needs to be stopped to stop the engine. Is there a thread on that end of things somewhere, does anyone know?

[oldtamiyaphile]

I don't think there's a thread on a diesel kill switch, as the usual method of ignition and fuel pump won't work.

However, I wouldn't go fitting a kill switch to a TDI anyway if you want the turbo to survive. For the occasional long traffic light (after a long DFCO) I just use the ignition switch. By comparison, in a petrol, you might be killing the ignition ten times per mile hence the need for a convenient dedicated switch.

[paulgato]

Originally Posted by oldtamiyaphile

I don't think there's a thread on a diesel kill switch, as the usual method of ignition and fuel pump won't work.

However, I wouldn't go fitting a kill switch to a TDI anyway if you want the turbo to survive. For the occasional long traffic light (after a long DFCO) I just use the ignition switch. By comparison, in a petrol, you might be killing the ignition ten times per mile hence the need for a convenient dedicated switch.

Thanks for advice, but a) what is 'DFCO', and b) what is the issue with the turbo? Can I not simply kill the fuel injector pump? What is the difference between that and keying off and on again? (...other than wear and tear on the ignition switch of course.)

I tend to switch engine off at long red traffic lights, and also on long, straight shallow descents where I don't want to use engine braking.

[RedDevil]

Originally Posted by paulgato

what is 'DFCO'

DFCO - Wikipedia, the free encyclopedia

DFCO may refer to:

Dijon FCO, Dijon Football Côte d'Or
Deceleration fuel cut-off, see Fuel economy-maximizing behaviors (section: Burn and coast)

Originally Posted by paulgato

what is the issue with the turbo?

The turbine in the exhaust can get extremely hot, it can fry its bearings etc.
As long as the engine runs those get cooled, but not if you kill the engine.
(Hope I did not oversimplify the issue)

[oldtamiyaphile]

Originally Posted by paulgato

what is the issue with the turbo? Can I not simply kill the fuel injector pump? What is the difference between that and keying off and on again? (...other than wear and tear on the ignition switch of course.)

As mentioned above, the turbo can fail if it's not allowed to cool prior to the engine being switched off. The usual recommendation is to let the turbo cool for 30 seconds after a high boost event before switching off. TDI's are on boost at normal drive speeds much more so than petrol turbos typically would be (although modern low pressure petrol turbos share a similar duty cycle). In short you can't P&G (EOC) a TDI like you can a petrol, because it's high load/ boost then engine off. Diesels use so much less fuel at idle that petrols that the EOC advantage isn't that great. Ever wonder why few if any turbo diesel hybrids exist? Potential economy would be astronomical, but an exhaust driven turbo wouldn't last.

Ideally, I'd love to swap my T5's exhaust driven turbo for an electric supercharger someday, then I could add a 4motion rear axle with electric motor and I'd have the best of everything, 900Nm of torque combined, 4wd and 60MPG

DFCO in a diesel means a lot of air is being drawn in with no heat being added, a great way to cool your turbo prior to shut down.

As for wiring the kill switch to the PD pump, I'm not sure, my 2007 pump is still mechanical. I think for the relatively occasional EOC opportunities with a TDI, a kill switch is a low priority.

[paulgato]

Ah... interesting info red devil and oldtamiyaphile. I didn't know that about TDi turbos.

I did once experiment with Pulse n Glide, though not with Engine Off Coasting. I found it didn't work for me at all well. A constant speed gets me way more mpg.

The way I drive this TDi, the turbo is almost never doing anything. I monitor boost pressure from time to time, and it's not zero, but pretty close.

Typical use of Engine Off Coasting for me is long straight shallow descents on motorways and dual carriageways, and on those roads my normal cruising speed is between 40mph and 50mph. At those speeds the turbo is pretty much idling. (On single carriageways I tend to keep my speed a little higher as it is more dificult for other drivers to overtake.)

Another occasional use of EOC is on local roads where for example along one stretch I happen to know that I can coast a mile or so and maintain the speed limit of 30mph. Again, no significant turbo boost going on prior. On those urban/suburban roads with a 30mph limit I typically sit at 27mph in 5th gear at engine tickover (800 RPM). At that speed on the flat I'm getting stupidly high mpg - like 140 or so - but still a mile of EOC can really boost my average up.

My car is relatively heavy, and normally is loaded down with work tools, and my feeling is I get best mpg when I can keep at a lowish speed and never slow down or accelerate.

One thing a mechanic once advised me - and this I do - is to blast the **** out of the engine once a week. Just for 30 seconds I'll accelerate up a hill, just to get the turbo spinning. The mecahnic reckoned that with the way I drive I could otherwise have problems with vanes sticking (I don't know what vanes are really, but lets not allow them to stick, eh?)

[Fat Charlie]

I thought it was the wickets that you folks were concerned about sticking. Now it's vanes?

[Jakins]

It would be so easy to design a secondary coolant resavoir and radiator for the turbo run by an electric pump that just runs constantly. But im not a thermal engineer so I dont know how well that would work in reality.

[Baltothewolf]

Originally Posted by Jakins

It would be so easy to design a secondary coolant resavoir and radiator for the turbo run by an electric pump that just runs constantly. But im not a thermal engineer so I dont know how well that would work in reality.

Not sure how much flow is needed (how much heat needs to be dissipated? ) because if it's low enough, you could probably make one out of a 360 or 480mm computer radiator, a pump and wire some fans to the battery with a switch inside the car to always run it.

[MetroMPG]

No more key twisting in the winter beater Civic!

This momentary switch is inline with the electric fuel pump circuit (which is in the cabin fuse block).

The beefy switch is left over from the Baker forklift scavenged to build the ForkenSwift (electric Metro).



Yes, I screwed it right into the shifter knob. :P