pete95zhn

I did some work on my friend's 996 turbo S (MY 2003) yesterday and noticed one interesting thing. Namely it doesn't have a fuel cooler. So far all turbo's I've seen has had one and even the pics I found from the internjet about GT2's there was the cooler installed if the car had a AC at all.
Friend's car's installation is very OEM look (I'd say 100% OEM) and is a perfect match to GT3's with AC.
So, has anyone else seen something similar before?

Reason for this question is a tempatation to remove this cooler from my engine. Why not?

jimq

i thought the Turbo S was only 2005?

pete95zhn

OK, X50 then...

Macster

My understanding is the Turbo has a fuel cooler.

Even if the car you are talking about came from the factory with no cooler, or more likely somebody removed it, why would you want to remove the fuel cooler from your car?

What do you hope to gain?

The Turbo's fuel tank has siphon jets and the pump constantly pumps fuel through these. The fuel pump runs all the time. It is cooled by the fuel. This heats up the fuel.

Remove the cooler and the risk is the engine may not make as much boost or power as the DME has to dial back boost or ignition timing to combat detonation brought about the negative effect hot fuel has on the intake charge when it is injected.

Even at other times, other than under the hardest acceleration, fueling may be affected if the DME assumes a narrow fuel temperature/density range of the fuel staged for the injectors.

Even if you're willing to risk this, the fuel cooler weighs next to nothing. The A/C system still remains so unless you're looking to lighten the car by removing the A/C system along with the cooler...

Sincerely,

Macster.

m3ntal

So did you ever figure out what he had in place of the fuel cooler? Im trying to delete mine and was told there is a stock gt3 replacement part to replace the cooler. Also, Ive read that evoms has machined fittings to get rid of it. Any ideas?

pete95zhn

IMO it had a GT3 parts, ie a tube in place of that cooler. I changed mine to a 997 turbo one with slightly altered piping, now it clears 997.1 turbo's Y-pipe.

Nolan Santacruz

In my opinion Fuel cooler is typically a container with a coil inside which is filled with ice or dry ice to reduce the temperature of incoming fuel.

993GT

for the record, the part I've circled in red is the fuel cooler
it works great on hot days BTW

jpflip

Resume from Porsche the essential companion page 197-201. Fuel cooler was installed only on american cars on 3.4 liters 996 and turbo cars. Connected between fuel pressure regulator and fuel tank to reduce fuel vapor levels of the returning fuel. Coolant is simply freon from the air conditioning compressor. After 2002 the cooler is connected to the fuel pressure line to cool the fuel entering the manifold to avoid vapor lock caused by fuel entering the EV6 injectors....

powdrhound

Hmm.... So, does the AC have to be on for the cooler to function? I have always run my car at the track with the AC off and never had any issues.

993GT

yes A/C must be engaged/running for the 'cooler' to function, the car doesn't need the 'cooler' to run right, just gives the engine a safety margin on very hot days by offering a mild intercooling effect(cold fuel spray reducing air charge temps.)

powdrhound

I learn something new every day. I always used to turn off the AC at the track to limit parasitic drag but I guess the idea I'd to leave it on to cool the incoming fuel instead. Thx.

993GT

I'd still bet that on track, running without the A/C on would be quicker as the intercoolers have adequate airflow and the parasitic power draw from the compressor would overrule any SLIGHT power gain from the cool fuel charge the A/C fuel cooler would provide, not to mention the radiators have to deal with warmer air from the A/C condensers infront of them and thus making the engine cooling system work harder to keep the coolant temp. happy(bit of a Catch-22)....
However in hot day(say 30C+) traffic, the fuel cooler would have greater effect as the engine cooling system isn't being taxed as hard but the air intercoolers are not seeing sufficient airflow and the engine bay temps are likely higher...
I'll try datalogging and posting results one day
or if anyone else has datalogged or dyno'd they're car and would like to post results, we would all appreciate it

Macster

No, the A/C does not have to be on for the fuel cooler to function, that is be cooled by the A/C.

At least not based on my unscientific test.

Last night after driving around 30 miles I pulled into home and parked the Turbo and with the engine idling got out and checked the lines to/from the fuel cooler.

The large line from the fuel cooler was obviously cool to the touch. Much cooler to the touch than the other lines/hardware in that area. The cooler can too felt cooler.

Also, the engine compartment fan was running so engine compartment temperature was elevated.

This observation reinforces my belief the fuel cooler is chilled all the time by the A/C compressor working all the time, even when the A/C is nominally off that is the snow flake symbol on the A/C system LCD is dark.

The compressor is a variable displacement type so it can be dialed back so that it doesn't have to be working that hard to provide cooling for the fuel cooler.

This does suggest though that an A/C system acting up due to possibly low refrigerant needs quick attention as the compressor could be running with low refrigerant which can result in two things: 1) the fuel is not chilled; 2) the compressor running even though the snowflake symbol is dark could suffer from inadequate lubrication because the oil is not being circulated due the low refrigerant level.

Anyhow, you can run your car at the track with the A/C off with no worries about hot fuel. The small parasitic loss from the compressor running is of no concern. And IIRC under hard acceleration the A/C compressor is disengaged so for the short time the engine is being worked hard even this small load is removed.

jpflip

False statement. I am sorry but this is completely wrong. An air conditioning cannot work if the compressor is not engage. The a/c switch function is to engage the clutch on the compressor and use the engine power to drive the compressor. Look at the pulley on the compressor you will see what I am talking about. With the switch in the off position the center part of the compressor pulley is not moving, means compressor off, means no compression of freon nil effectivity of the a/c system. Now put the switch in the "on" position you will see the center part of the compressor pulley start moving and driving the compressor.... I've been looking at the wiring diagram and also "The essential companion" to found a reason to get the air conditioning to start automatically without engaging the switch because of certain parameter and could not found anything. Once the switch is off the compressor clutch is disengaged...