Many people have gone through the pikey mod, then on to a FMIC. What I was wondering is - would it be a good idea to mount a big return fuel line cooler in place of the OEM SMIC? After the pikey mod, it would have pretty good airflow.

Another question - could the OEM SMIC be adapted by TIG welding or clever pipework to work as a fuel line cooler?

I guess it's down to the actual internal bore of the cooling lines, but this could be a potential good (re-)use of the "stored" OEM SMIC's that many people have about...

Any comments?:confused:

Bas

The 3B Passat with the 115 bhp PD engine originally had its fuel cooler mounted in such a place. Not sure why they moved it, maybe didnt work so well.

The original IC would be no good to cool fuel. Its and air to air cooler and the internal bore is far to large, doubtfull it would take the pressure either.

And remember the OE fuel cooler is on the return line, its only purpose is to stop hot fuel returning from the engine distorting the plastic fuel tank.

The little t piece valve on top of the fuel filter on the return line actually redirects the hot returned fuel back into the supply line at given temperatures to stop fuel waxing which happens when diesel gets to cold.

Thanks Ross - may see about mounting a proper fuel cooler where the SMIC was, keeping the OEM fuel cooler as it is.....

I take it you plan on mounting it on the supply line then?

no mate - on the return line - before the OEM cooler. From my limited understanding - it's the hot returning fuel that brings up the temps in the entire tank, is that right?

I see where your going with the idea.

However is cold diesel a good thing? My understanding is as diesel is cooled it thickens as its a heavy oil and thus flows slower.

I've still got an oil cooler to go in somewhere, can be used as fuel one too, but not sure what I can do with it now lol

I see where your going with the idea.

However is cold diesel a good thing? My understanding is as diesel is cooled it thickens as its a heavy oil and thus flows slower.

Your right Ross as always.

Warmer fuel is much better, Think of burning fuel as a chemical reaction. The more heat in the system the faster the particals flow around and the more reactions occur.

Same thing for fuel, the warmer the fuel the faster it flows, injects and burns.

If anything you would want a fuel warmer, but i doubt youll have the problem of fuel waxing in your climate Bas

Oil cooler is a totally different story, Whilst its nice to have warm oil, if the oil gets too hot it can start to burn off in the oil feed lines to the turbo. This leaves carbon deposits in the line which over time build up and block the oil feed. Then the turbo is starved of oil and you can guess the outcome

Maybe you could mount an oil cooler in the space left by the removal of the SMIC.

thing is - big diff when I fill up with diesel at the gas station - cooler fuel at 38 deg C is a good thing....

Warmer fuel is much better, Think of burning fuel as a chemical reaction. The more heat in the system the faster the particals flow around and the more reactions occur.

Same thing for fuel, the warmer the fuel the faster it flows, injects and burns.

Generally you get more efficiency (read: power) by having a larger temp differential between before and after - you can't do much about after as it's the temp at which the fuel burns so you reduce the incoming temp (hence cold air and presumably cold fuel). I was under the impression that it's this which makes the car run better when you've just filled up - a nice large tank of cold fuel. When you're down to the dregs it'll be relatively hot because of the return stuff.

Diesel has to be REALLY cold to start waxing. Certainly sub-zero.

many years ago - I used to run a fuel cold can from moroso - it was a cork insulated ally can with coils of tubing inside and a drain underneath.

The idea was to fill with ice or dry ice to cool the petrol down to get max bhp for the drag strip...

With a full tank of cool fuel, or first thing in the am after the engine's warmed up, I notice a power difference..

Think this needs some experimentation..

I think petrol and diesel will react differently. And remember you have a fuel temp sensor on the PD and this alters fueling according to temp and IIRC from my notes the engine management alters things to keep that fuel at optimum.

I see where Ross is coming from, and where Basil is coming from.

As for who's right:-

1) Ross is in the general case

2) Either of them might be right in the Bahrain specific case. What can overnight air temperatures get down to in Bahrain Baz?

overnight - 30 deg C - it was 42 deg C yesterday around noon. Deffo more smoke, lol

At that rate, as long as it's small enough to actually work with the flow rates involved, I'd say a fuel cooler is a good idea; maybe consider a thermostat to bypass it below 15C air temp.