306oc - Peugeot 306 Owners Club & Forum

Right having realised that my car cutting out is to do with fuel temp has got me thinking more about aftermarket fuel coolers.

When I did the fuel filter the engine was still warm (not hot hot) and I drained the fuel into a 500ml coke bottle, it was a while till I put the cap on the bottle but when I did I left the bottle in the garage overnight and it shriveled right up and it got me thinking that there must be a pretty huge difference in density between fuel at operating temp and cold fuel.

Anyway I know there is a fuel cooler as standard but its rubbish obviously so what would be better, taking up even more front end space (and weight) or maybe a really long thin one behind the back bumper in the air flow. Maybe using a pair of mocal style oil coolers.


Do you think its possible to over cool the fuel, I know there is a fuel temperature sensor that alters the map?

The fuel cooler cools the fuel returning to the tank! You want the fuel warm for most efficient engine running.

The hotter it is, the less energy it takes to start burning. Hence the fuel heaters on diesels, older style runs fuel by the coolant, newer ones have an electric fuel heater.

Why though, surely denser fuel is more effieient?

I don't think it works the same way as inlet temps dum, personally i would think it'd just make it harder for the HP pump to supply the fuel needed

(09-09-2013, 03:04 PM)Dum-Dum Wrote: [ -> ]Why though, surely denser fuel is more effieient?

Diesel has to heat up to burn when it reaches the cylinder, it doesn't just explode like petrol with a spark, theres a time delay before this happens, if the fuel is already hotter, that time delay is shorter, so it burns quicker and more efficiently. Denser fuel also doesn't atomise as well when it's injected, which is necessary for complete combustion.

Think about what happens when you start a diesel without glow plugs - cold cylinder, only part burnt fuel and poor efficiency. Runs like crap until it heats up a bit. It's the same effect.

Yes and no - you do want cool fuel going to the CR pump, when you're working the pump hard, the hotter the fuel, the harder it is to pump.

Take a look on various forums, there's lots of pictures of the Fuel Temperature Limiter maps - that'll give you a good idea of where *at standard* they're pulling power due to fuel temperature, those maps however ARE to save the CR pump, they're not to affect power at low RPMs, that's done off the Coolant Temperature maps...