Improving MPG

revjames said:

Someone told me you can take the viscous fan off and (if you have an ES) you can use the 2 fans from the A/C to do the cooling (they actually did cut in when I had overheating problems with the HGF) Anyone else heard of this?

Click to expand...

Hi there, I took the viscous fan of my wife's Tdi 200 manual, about 2 and a half years ago. No overheating - ever - even when towing, even in summer when it gets quite hot here, never. The benefits are quieter running, slight increase in pick-up and definite 32-3 mpg increase.

Then I bought a '98 Tdi 300 auto for myself. Within 2 weeks it had a full filters service, De-EGR and viscous fan off.

I'm getting over 35mpg out of the Tdi 200 and 33 from the TDi300. These are daily running figures, NOT on long runs where they both increase by about 5 mpg.

I don't go over 65mph though, the aerodynamics will kill mpg at 75-80mph.

thebiglad said:

Hi there, I took the viscous fan of my wife's Tdi 200 manual, about 2 and a half years ago. No overheating - ever - even when towing, even in summer when it gets quite hot here, never. The benefits are quieter running, slight increase in pick-up and definite 32-3 mpg increase.

Then I bought a '98 Tdi 300 auto for myself. Within 2 weeks it had a full filters service, De-EGR and viscous fan off.

I'm getting over 35mpg out of the Tdi 200 and 33 from the TDi300. These are daily running figures, NOT on long runs where they both increase by about 5 mpg.

I don't go over 65mph though, the aerodynamics will kill mpg at 75-80mph.

Click to expand...

I would be very waery taking the fan off. Do you use the air con fans to cool it at all?

iannotts said:

I would be very waery taking the fan off. Do you use the air con fans to cool it at all?

Click to expand...

This is what I want to know. I was thinking of putting a 2 way relay in the A/C fan cct so you could override it and manually turn them on or even use a temp switch to control it. I did notice they were running when I overheated when I was having HG problems so maybe there an 'emergency; circuit in there? I think if I was to take it off I would keep it in the boot just in case!

iannotts said:

I would be very waery taking the fan off. Do you use the air con fans to cool it at all?

Click to expand...

I don't have air-con in either Disco so, no, I don't have any fan cooling at all.

The thing you need to bear in mind is that when the engineers were designing these vehicles they need to be cooled in all situations and all countries, hot weather, off-road, slow traffic queues, towing etc.

I have proved to my own satisfaction that my vehicles don't need fan-assisted cooling in the operating conditions they're in currently and there are benefits to having the fans de-installed.

Having said that, in the Tdi 300 I always have the fan with me so that IF I'm in conditions requiring fan assistance, it takes 30seconds to re-install.

With the Tdi 200, it has been used in pretty much all conditions without showing any need for auxilliary cooling, for nearly 3 yrs now, so I reckon that is as good a test as I can make.

Incidentally, Kenlowe, on their site, state that the viscous fan is almost never 'fully' used and when replaced with an electric fan , the lecky one almost never comes on !!!!!

I Fitted a new exhaust today and also fitted the decat pipe. The difference is amazing, the best £18 I've spent (the decat pipe not the complete exhaust). The Disco is much more responsive and eager now it has transformed its driveability. Go on everyone decat your Disco's today.

I think I've sussed it out. On the thermostat housing there are (i) a temperature sender unit for your gauge and (ii) a temperature switch that controls the A/C fans on the front of the rad (ES models only) This switch only seems to bring the fans on in the event of a very high engine temperature (as was the case last year when my head gasket went) To me the easiest way to utilise these fans would be to wire a dash mounted switch in paralell with the temperature switch. This way if you see the temp beginning to climb or you know theres a steep hill ahead and you are towing - you can switch the fans on ready. I think I will fit the switch and experiment a little before I remove the viscous fan. Thinking about it, the best way would be to identify the relay that controls the fans and just wire an overide to the coil of that.