Hi,
I have a xantia Nreg 1.9 Turbo Diesel with a Bosh Pump.
Does anyone know if I can adjust something to improve fuel economy, without the risk of MOT failure?
I dont mind a slight loss of performance.
Yes the airfilter has been changed.
Regards
Exect
Fuel Economy
Moderator: RichardW
The fundamental difference between diesel and petrol engines is that diesels work on the principle of free air. having got the technical term out of the way this means that they have an unrestricted air supply - and the only control is the amount of fuel injected. At idle little fuel is injected and thee ngine develops little power - inject more fuel - engine runs faster.
In a petrol engine the engine inhales a petrol/air MIXTURE as a gas and its speed (hence power) is controlled by the amount of the gas and to some extent by its composition. The gas is made up either in a carburrettro or in the manifold at the point of injection.
So the answer to your question is no - you can't adjust the pump to give better economy.
Unfortunately TD Xantias are very heavy (about 20 - 25% more than a BX) and this is reflected in the economy and performance.
Curiously 2.1's which have 3 valves but are essentially similar to the 1.9 are claimed to be no thirstier - and the HDi which is a bit different and uses a much higher injection pressure amongst other things which gives better atomisation - and hence better combustion is noticeably better on fuel.
In a petrol engine the engine inhales a petrol/air MIXTURE as a gas and its speed (hence power) is controlled by the amount of the gas and to some extent by its composition. The gas is made up either in a carburrettro or in the manifold at the point of injection.
So the answer to your question is no - you can't adjust the pump to give better economy.
Unfortunately TD Xantias are very heavy (about 20 - 25% more than a BX) and this is reflected in the economy and performance.
Curiously 2.1's which have 3 valves but are essentially similar to the 1.9 are claimed to be no thirstier - and the HDi which is a bit different and uses a much higher injection pressure amongst other things which gives better atomisation - and hence better combustion is noticeably better on fuel.
jeremy
-
Peter.N.
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You can adjust the pump to deliver less fuel which will actually improve the emmissions but it will also reduce the performance and may have the opposite effect to the one that you are looking for because you will tend to drive it harder which will increase the fuel consumption.
Diesels are at there most efficient at small throttle openings and relativly low speed. If you keep your revs to around 2,000 and aviod 'flat tothe floor' driving, you will get the optimum fuel economy.
You may even find that a 2.1 will give better economy, because it produces a lot of low down torque and means that you can hang on to low gears longer.
Mx 2.1 td XM, a heavier car than the Xantia, averages over 40 mpg and on a long journey will exceed 50 mpg. But I do live in a rural area and dont drive hard or very fast. Its actually better than my wifes ZX!
Diesels are at there most efficient at small throttle openings and relativly low speed. If you keep your revs to around 2,000 and aviod 'flat tothe floor' driving, you will get the optimum fuel economy.
You may even find that a 2.1 will give better economy, because it produces a lot of low down torque and means that you can hang on to low gears longer.
Mx 2.1 td XM, a heavier car than the Xantia, averages over 40 mpg and on a long journey will exceed 50 mpg. But I do live in a rural area and dont drive hard or very fast. Its actually better than my wifes ZX!
I echo the comments above about the 21.TD. IMHO it is a fabulous engine, being very refined, smooth and quiet and giving loads of torque, which enables a relaxed driving style and hence (for the size of the car) excellent fuel economy. No exaggerating, it will do a genuine 45 mpg (air con off!) day to day running and over 50 mpg on a run driven sensibly at the speed limits. Some motoring pundits decry the sound of a diesel engine as being tractor like but I like the sound of diesels. Personal choice. Sure, you know the PSA 2.1 is a diesel at tickover but it certainly doesn't rattle like some BMWs, Volvos, VWs and others I've heard and at motorway speeds all you can hear is a distant hum. Brilliant! 
Think you mean "High gears" don't you Peter?You may even find that a 2.1 will give better economy, because it produces a lot of low down torque and means that you can hang on to low gears longer.
Be careful!