Thread: Deleting fuel cooler.

Originally Posted by admiralranga

Less relevant here but I do suspect the coolant ones do a decent job of warming the fuel up when it's very cold.

I don't think it would matter too much. As far as I can tell the pump recycles a fair bit of the returned fuel - not a huge amount of fresh tank fuel gets used.

A bit like taking a leak in a pool, it makes its own warm spot.

So does anyone know what the implications of cold fuel have on tuning in a diesel?

shorter pulse width?
adjustments in injection timing?

I don't think colder fuel would make any difference regarding making the charge cooler as it's already in the cylinder when injected, but the other factors must play a part in performance / economy.

Just wondering - for better or worse?

The temperature affects density and the injected quantity depends on that, as long as the FT input is involved in the managmenet it's not so simple... go back to post #10 and see what's in that link i posted

Originally Posted by sierrafery

The temperature affects density, go back to post #10 and see what's in that link i posted

Yeah i get that.

Thats all compensated for by the ecu (within reason)

The ECU adjusts Pulse Width to compensate for the denser fuel, maybe also adjusts timing?
But adjusting pulse width will also alter the timing as well (inadvertently)

I'm not worried about hot fuel, more curious about cold fuel now. As to why or even if it does enable more power.
I'll be running an external air cooled cooler, unless i'm convinced otherwise that 70c fuel is a good thing. To me the stock heat exchanger seems like a compromise between having something that will run anywhere in any climate (not a bad thing) and peak performance.


Just wondering if these changes have a positive or negative affect.

I think that an automotive engineer could explain better why they use coolant based fuel coolers and not air cooled ones... though if you know that you'll drive it when it's really cold outside think about some thermostatic bypass setup as to not let the fuel through the air cooled cooler before it reaches 70*C or it's possible to run with it overfuelled for too long

Originally Posted by sierrafery

I think that an automotive engineer could explain better why they use coolant based fuel coolers and not air cooled ones... though if you know that you'll drive it when it's really cold outside think about some thermostatic bypass setup as to not let the fuel through the air cooled cooler before it reaches 70*C or it's possible to run with it overfuelled for too long

I've been running all week without a cooler of any sort - max temp was 66 deg. But this is in a cold horrible place. Not sub zero but close. You are right though, with an air cooler fitted a bypass would be needed for sure. I'll make a bag that fits over the cooler for winter running (if i'm still stuck in this hell hole)

If needed I can take a pic of my D2a which was converted to the new type about 11 years ago and no problems since. Was done by Fred Smith who used all original LR parts incl hoses.

I wouldn't overthink all this stuff guys.


The LR technical info says the fuel cooler is for "optimum performance and emissions"

The fuel is kept within a certain temp range as it enters the head/injectors.

The difference pointed out above as regards timing being affected is true, but the difference is negligible..I wouldn't worry about it.

The TD5 engine management has maps that makes allowance for different temperature fuel and adjusts pulse width to ensure the correct MASS of fuel is injected.

Personally I'd keep the cooler, it'll stop the fuel in the tank getting extremely hot when in hot weather with low fuel in the tank, it'll also lift the temp of the fuel entering the head when it's cold, I'd also view that as a win.

As a side note, I'd definitely be making sure the fuel temp sender is working otherwise you'll get poor performance results.