Fuel cooler before/after
#1
09-14-2018, 02:10 AM
#2
09-14-2018, 02:19 AM
Veteran Member
Well, not really super great. I mean, it is in the return side of the AC. ResultIng in the freon already being warm due to absorbing the heat from the air in the evaporator/HVAC box behind the dash. So it isn't as effective. I guess, without checking for temperatures, that it isn't going to cool down massivly. As a guesstimate, maybe about 5-10°C. Just enough to be a tad cooler. If it was in the feed piping (from filter/condensor to expansion valve) it would be more effective. People run their V12s without it and have no differences. So it has a very minimal impact in the entire setup.
#3
09-14-2018, 12:20 PM
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#4
09-14-2018, 01:29 PM
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The effectiveness (and importance) of the fuel cooler might well vary according to how much gas is in the tank?
If you have a full 25 gallon fuel load on board and the car has been baking all day in the Las Vegas sun, in August, the cooled fuel returning to the tank might not make much difference. At least not very quickly.
On the other hand, if you have but 5 gallons in the tank.......
Cheers
DD
If you have a full 25 gallon fuel load on board and the car has been baking all day in the Las Vegas sun, in August, the cooled fuel returning to the tank might not make much difference. At least not very quickly.
On the other hand, if you have but 5 gallons in the tank.......
Cheers
DD
#5
09-14-2018, 01:36 PM
Veteran Member
The effectiveness (and importance) of the fuel cooler might well vary according to how much gas is in the tank?
If you have a full 25 gallon fuel load on board and the car has been baking all day in the Las Vegas sun, in August, the cooled fuel returning to the tank might not make much difference. At least not very quickly.
On the other hand, if you have but 5 gallons in the tank.......
Cheers
DD
If you have a full 25 gallon fuel load on board and the car has been baking all day in the Las Vegas sun, in August, the cooled fuel returning to the tank might not make much difference. At least not very quickly.
On the other hand, if you have but 5 gallons in the tank.......
Cheers
DD
#6
09-15-2018, 01:46 AM
Veteran Member
Well, not really super great. I mean, it is in the return side of the AC. ResultIng in the freon already being warm due to absorbing the heat from the air in the evaporator/HVAC box behind the dash. So it isn't as effective. I guess, without checking for temperatures, that it isn't going to cool down massivly. As a guesstimate, maybe about 5-10°C. Just enough to be a tad cooler. If it was in the feed piping (from filter/condensor to expansion valve) it would be more effective. People run their V12s without it and have no differences. So it has a very minimal impact in the entire setup.
Jaguar removed the cooler on later models anyway, so they obviously thought it was not needed, but as it also reduced assembly and parts costs maybe that was a cost rather than an engineering decision?
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#7
09-15-2018, 02:16 AM
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#8
09-15-2018, 08:32 PM
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#9
09-23-2018, 05:12 PM
I pitched the GM a/c unit and went with a Sanden compressor and 134A about 4 years ago. I also ditched the fuel cooler at the same time. Have not noticed any negative effects, so I would suspect that its effectiveness was negligible. Then again, I'm not racing, so to someone who wants the utmost in performance maybe it does make a difference.
Thanks,
John
1987 XJ-S V12
Thanks,
John
1987 XJ-S V12
#10
09-23-2018, 11:39 PM
Interesting responses, I know some 'supercars' use an AC type system to cool incoming air, often built into turbo intercoolers, it functions as a closed system providing cold air supply.
I'm not sure if routing the full A/C capacity to the filter boxes would be of much use even if you had them and the manifolds insulated. That and the plumbing to fit an effective system in the filter box would be too much effort.
I'm not sure if routing the full A/C capacity to the filter boxes would be of much use even if you had them and the manifolds insulated. That and the plumbing to fit an effective system in the filter box would be too much effort.
Last edited by VancouverXJ6; 09-23-2018 at 11:42 PM.
#11
09-24-2018, 12:04 AM
Veteran Member
The reason it is there is evaporative emissions, the car isn't emissions compliant without the cooler. Jaguar measured fuel temps of 60C without the cooler, thus why it is there. Modern cars don't have it because they do not use a circulating system, there is no return line. The fuel pump is PWM controlled to run based on the engines demand, so the fuel stays in the tank instead of being circulated over a hot engine and picking up a lot of heat.
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#12
09-24-2018, 03:03 PM
Veteran Member
I believe that many people do not pay attention to this.
XJS V12 convertible from 89 to 92 A/C works automatically, independently the climate control is switched on or not. I read an article about it somewhere.
The fuel cooler was installed on all XJ6 and XJ12 l, 'll, lll series equipped A/C including carburettor and XJS V12 up to 1992.
I think it would not be superfluous for other more modern cars.
#13
09-24-2018, 03:10 PM
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the reason it is there is evaporative emissions, the car isn't emissions compliant without the cooler. Jaguar measured fuel temps of 60c without the cooler, thus why it is there. Modern cars don't have it because they do not use a circulating system, there is no return line. The fuel pump is pwm controlled to run based on the engines demand, so the fuel stays in the tank instead of being circulated over a hot engine and picking up a lot of heat.
Last edited by Brutal; 09-24-2018 at 03:13 PM.
#15
09-24-2018, 11:45 PM
Veteran Member
The reason it is there is evaporative emissions, the car isn't emissions compliant without the cooler. Jaguar measured fuel temps of 60C without the cooler, thus why it is there. Modern cars don't have it because they do not use a circulating system, there is no return line. The fuel pump is PWM controlled to run based on the engines demand, so the fuel stays in the tank instead of being circulated over a hot engine and picking up a lot of heat.
It has no emissions control stuff from factory. No cats, no lambda sonds, no charcoal canister, ... But I still have the fuel cooler
And there are quite a few modern day cars with a fuel return system. My 2007 Volvo C30 had a full standard system. My current to be shifted 2018 Fiat 500 1.2l (Fire series) has a return. But they lack fuel coolers and both engines run a lot horten than the XJ-S' V12...
#16
09-25-2018, 12:32 AM
Veteran Member
No idea, but it certainly doesn't do any harm. In some ways it's actually a very good thing from the AC system's point of view, as it ensures there is absolutely no liquid going back to the compressor. Slugging a compressor with liquid is a very bad thing! 1960's Chryslers had a similar sort of piping arrangement for that reason of protecting the compressor.
The Euro spec V12's did have a much more complicated ignition timing system than the North American cars to compensate for the lack of catalytic converters, maybe the fuel cooler was the thing that would have tipped emissions over the knife balance? I have no idea.
The Euro spec V12's did have a much more complicated ignition timing system than the North American cars to compensate for the lack of catalytic converters, maybe the fuel cooler was the thing that would have tipped emissions over the knife balance? I have no idea.
#17
09-25-2018, 06:47 AM
Veteran Member
Just a personal anecdote. 160 mile trip cruising back roads 40-50 mph in 95F temps, no A/C. Fuel vapor recovery system clogged. I first noted a very strong raw fuel odor at stops. Then noticed a visible cloud of light distortion surrounding the fill spout whenever stopped. Pulled over for fuel and had 25-30 psi in the fuel tank. I didn’t gauge it, but opening was a furious discharge that lasted 5-6 seconds. No simple ‘woosh’. Tank was hot to the touch. Not quite as hot as the intake manifold.
Vapor system being clogged was the fault for the pressure build-up, but had it not been clogged I’d just have not known just how hot the fuel gets and just how much is being lost to evaporation on a hot run.
If the fuel circulates through that bay and isn’t cooled it is being heated. Hot fuel is not what anyone wants.
I’ll either her add a fuel cooler out in the nose, or change to a bay mounted sump/pump combo. Circulating only the sump fuel, return to sump, and refilling sump with original pump. All that complexity make a simple finned aluminum fuel cooler sound like the obvious choice for me.
Vapor system being clogged was the fault for the pressure build-up, but had it not been clogged I’d just have not known just how hot the fuel gets and just how much is being lost to evaporation on a hot run.
If the fuel circulates through that bay and isn’t cooled it is being heated. Hot fuel is not what anyone wants.
I’ll either her add a fuel cooler out in the nose, or change to a bay mounted sump/pump combo. Circulating only the sump fuel, return to sump, and refilling sump with original pump. All that complexity make a simple finned aluminum fuel cooler sound like the obvious choice for me.
#18
03-20-2020, 09:12 PM
Junior Member
Old thread, but I came across this device when removing the intake manifolds today and was initially confused about how it worked, but assumed it was a fuel cooler and here I am. While I was tracing the line I noticed it bends around, and fairly close to, the rear muffler before entering the fuel tank. I would have to think that any cooling done by the fuel cooler is undone by the exhaust. My line is not shielded, and neither is the exhaust at this location. I don’t have a need to remove it, but I’m frustrated with the fuel lines compression fit to this unit. They are old and also don’t want to come off. I’m a fan of -an fittings and quick releases. I suppose I’ll just convert it all while I’m tearing it down.
#19
03-21-2020, 12:00 AM
Old thread, but I came across this device when removing the intake manifolds today and was initially confused about how it worked, but assumed it was a fuel cooler and here I am. While I was tracing the line I noticed it bends around, and fairly close to, the rear muffler before entering the fuel tank. I would have to think that any cooling done by the fuel cooler is undone by the exhaust. My line is not shielded, and neither is the exhaust at this location. I don’t have a need to remove it, but I’m frustrated with the fuel lines compression fit to this unit. They are old and also don’t want to come off. I’m a fan of -an fittings and quick releases. I suppose I’ll just convert it all while I’m tearing it down.
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