The Fuel Cooler
Discussion
Likewise, Paul, and the cooling effect is maximum where the temperature differences are greatest. So in this case the fuel exits the rail very hot (from pressurisation and heat soak), and returns to the tank cooler than it was before. Hooray for the tank!
But combustion is most efficient with cold and dense charges. Our intake air is collected well away from heat (but unfortunately then has to travel over some very hot things... perhaps intake air should pass through the AC evaporator
...) So wouldn't it be an advantage if the fuel could reach the rail chilled?...
Just wondered if any one had seen any research, would be relatively easy to do a back-to-back test on a dyno, only a matter of changing a few pipes.
But combustion is most efficient with cold and dense charges. Our intake air is collected well away from heat (but unfortunately then has to travel over some very hot things... perhaps intake air should pass through the AC evaporator
...) So wouldn't it be an advantage if the fuel could reach the rail chilled?... Just wondered if any one had seen any research, would be relatively easy to do a back-to-back test on a dyno, only a matter of changing a few pipes.
Valid point, but the weakest part in our fuel system has to be hose rather than the solid metal pipe that passes seamlessly into, through and out of that cooler body.
Just to be clear, I'm not advocating doing it nor am I considering doing it on my rebuild, it was more a question for the racers.
Just to be clear, I'm not advocating doing it nor am I considering doing it on my rebuild, it was more a question for the racers.
I could very well be wrong but I was under the impression the fuel rail was under pressure direct from the pump. With pressure regulator sitting on the end letting just the right amount back to the tank in the return line, keeping the fuel rail at the correct pressure.
If that is the case ours has always been in the feed line, we've had the car since it was two years old, it went to TVR main dealers & APM, non of them made any comment on the plumbing of the cooler so I just left it where it was.
I've no idea if / what difference the cooler makes, the AC has been broken on & off over the years, I never noticed any difference.
If that is the case ours has always been in the feed line, we've had the car since it was two years old, it went to TVR main dealers & APM, non of them made any comment on the plumbing of the cooler so I just left it where it was.
I've no idea if / what difference the cooler makes, the AC has been broken on & off over the years, I never noticed any difference.
The fuel cooler does serve a purpose for the a/c system. It prevents any liqiud refrigerant returning to the a/c compressor which would drasticaly shorten the life of it, as you cannot compress a liquid.
The cooler is a heat exchanger, the heated fuel passes over the refrigeration pipwork within the cooler thus heating it up, this heat is absorbed by the cool refrigerant leaving the evaporator and evaporates any liquid refrigerant to a gas ready for compressing again, which in turn cools the fuel which retuns to the fuel tank.
I think the cooling of the fuel may just be a benificial by product of having the a/c system as i think the a/c system was an optional extra. So therefore there must be some cars running around without a fuel cooler and i don't think they have anything fitted to replace it and cool the fuel.
Hope this helps.
The cooler is a heat exchanger, the heated fuel passes over the refrigeration pipwork within the cooler thus heating it up, this heat is absorbed by the cool refrigerant leaving the evaporator and evaporates any liquid refrigerant to a gas ready for compressing again, which in turn cools the fuel which retuns to the fuel tank.
I think the cooling of the fuel may just be a benificial by product of having the a/c system as i think the a/c system was an optional extra. So therefore there must be some cars running around without a fuel cooler and i don't think they have anything fitted to replace it and cool the fuel.
Hope this helps.
It's more of benefit to the fuel than the a/c system. The idea is that use of the a/c in warmer weather helps prevent partially evaporated fuel being returned to the fuel line. Evaporated fuel returning back from the tank to the rail causes a lean mix. In reality, the cooler fitted to the cerb is as much use as a chimney on a dog...
Cerberaherts said:
It's more of benefit to the fuel than the a/c system. The idea is that use of the a/c in warmer weather helps prevent partially evaporated fuel being returned to the fuel line. Evaporated fuel returning back from the tank to the rail causes a lean mix. In reality, the cooler fitted to the cerb is as much use as a chimney on a dog...
(My highlighting) My point exactly, precisely why it would be more beneficial in the feed line!Perhaps we're not seeing the whole picture.
As you said earlier, the fuel cooler is most effective when there is the greatest temperature differential.
So it operates by keeping the fuel temp down in the whole system, comprising tank and injection system.
No point trying to cool fuel as it enters the injectors, if the temp of the fuel in the tank from which it emanates is that much higher than it needs to be.
Try spending a day having your car mapped at a rolling road if you are in any doubt how hot the fuel tank can get.
As you said earlier, the fuel cooler is most effective when there is the greatest temperature differential.
So it operates by keeping the fuel temp down in the whole system, comprising tank and injection system.
No point trying to cool fuel as it enters the injectors, if the temp of the fuel in the tank from which it emanates is that much higher than it needs to be.
Try spending a day having your car mapped at a rolling road if you are in any doubt how hot the fuel tank can get.
ukkid35 said:
Perhaps we're not seeing the whole picture.
As you said earlier, the fuel cooler is most effective when there is the greatest temperature differential.
So it operates by keeping the fuel temp down in the whole system, comprising tank and injection system.
No point trying to cool fuel as it enters the injectors, if the temp of the fuel in the tank from which it emanates is that much higher than it needs to be.
Try spending a day having your car mapped at a rolling road if you are in any doubt how hot the fuel tank can get.
Exactly. They are always in the return line. Hot fuel fleeing back to the fuel tank heats it up like a tea urn. Older Astons, jags and a few other Marques ran similar setupsAs you said earlier, the fuel cooler is most effective when there is the greatest temperature differential.
So it operates by keeping the fuel temp down in the whole system, comprising tank and injection system.
No point trying to cool fuel as it enters the injectors, if the temp of the fuel in the tank from which it emanates is that much higher than it needs to be.
Try spending a day having your car mapped at a rolling road if you are in any doubt how hot the fuel tank can get.
I know they're always in the return line on other vehicles and I understand the reasoning. It's de rigeur on modern diesels with their incredible high injection pressures causing heating of the 'fuel' (I use that term loosely in relation to Derv... and would've thought heating diesel before trying to set fire to it could only ever be a good thing!).
Interestingly, an online search shows that some Cerberas have been 'wrongly plumbed' with owners stating that their coolers are definitely in the supply side, unless of course they were misinterpreting the direction of flow... but it also shows that it's been raised on here before with current user names in the mix.
But my point was, given that intercoolers are beneficial to cool intake air immediately before use, would there not be an advantage in cooling the fuel near to the point of use too? OK, using a second cooler if necessary.
I've heard of racing motorcycles chilling their fuel before a race but I think that's more to do with getting more crammed into a limited size tank, wasn't that the case in F1 too?
Maybe one for the drag racers to explore? Liquid Nitrogen, anyone?
Interestingly, an online search shows that some Cerberas have been 'wrongly plumbed' with owners stating that their coolers are definitely in the supply side, unless of course they were misinterpreting the direction of flow... but it also shows that it's been raised on here before with current user names in the mix.
But my point was, given that intercoolers are beneficial to cool intake air immediately before use, would there not be an advantage in cooling the fuel near to the point of use too? OK, using a second cooler if necessary.
I've heard of racing motorcycles chilling their fuel before a race but I think that's more to do with getting more crammed into a limited size tank, wasn't that the case in F1 too?
Maybe one for the drag racers to explore? Liquid Nitrogen, anyone?
This was discussed a few years ago and i think the conclusion was that as is usual for TVR not all cars are plumbed the same. My cooler is definitely in the feed line. My cars lines run as follows
bulkhead to cooler
cooler to front of rail
rear end of rail (pressure valve) back to bulkhead
bulkhead to cooler
cooler to front of rail
rear end of rail (pressure valve) back to bulkhead
mines on the feed line as well. 4.5 AJP 1998, hard fuel lines through the interior. On the early 4.2 with the fuel lines that run along the transmission tunnel, it feeds straight from pump into the fuel rail, bleeds to the fuel cooler and then back to tank.
I think the priority is the AC circuit rather than engine performance. Perhaps they wanted a little lift on the inlet temp to the AC compressor as the more you start with the more efficient the AC circuit is.
I dont know what the temperature difference is between inlet to fuel rail and outlet but I wouldn't think its a huge amount as fuel is incompressible and the pressure is low. If it was a modern Common rail diesel engine, the pressures would be in a different league so the pressure drop on the PCV would be much greater and create much temperatures going back to tank.
I think the priority is the AC circuit rather than engine performance. Perhaps they wanted a little lift on the inlet temp to the AC compressor as the more you start with the more efficient the AC circuit is.
I dont know what the temperature difference is between inlet to fuel rail and outlet but I wouldn't think its a huge amount as fuel is incompressible and the pressure is low. If it was a modern Common rail diesel engine, the pressures would be in a different league so the pressure drop on the PCV would be much greater and create much temperatures going back to tank.
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