The Quest for 600 bhp - Part 4 - "Chargecooling".
Discussion
Most of my time has been spent on R+D so far with the cooling system described on the board recently. I am going all electric on the cooling system both on pump and cooling fan(s) with full thermostatic control on both. I have selected the single Rotrex C38-81 supercharger I will be using, which in its own design is a very new and cutting edge technology.
CHARGECOOLING.
Charge cooling involves the cooling of the air entering the engine cylinders
known as the inlet "charge".
As you may well know, whenever air is compressed, either by way of a turbocharger or a supercharger, the resultant compressed air temperature is increased. This is not due, as some believe, to the proximity of the air to the glowing hot turbocharger, but by the energy contained within the gas.
See here…
http://en.wikipedia.org/wiki/Ideal_gas_law
This increase in temperature reduces the density and therefore the oxygen content of the charge, and greatly increases the chance of engine combustion getting to the detonation threshold. It is therefore of great importance to reduce this charge temperature as far as possible. Cold dense air will produce more power than hotter air at higher pressure that contains less oxygen.
The easiest and most popular method is by using an air to air intercooler which passes cold external ambient air through a (usually front mounted) aluminium radiator, through which the hot compressed air is passed, cooling it in the process. The other main option, and my choice in this case, is the air to water intercooler generally referred to as a chargecooler. This more complex system uses a radiator sealed within a chamber through which cold water passes, transferring the heat from the compressed air into the water which in turn has a small radiator, reservoir of approximately one to two litres and a pump to circulate it and expel the
absorbed heat to atmosphere, further compounding global warming!
My system will NOT be intercooled but will utilise a CHARGECOOLER similar to the Aston Martin and Jaguar system but with its own pump, tank and cooler rather than using the engines coolant system.
This is a method of cooling the hot incoming compressed air charge from the supercharger as it passes through the chargecoolers (air to water radiators) mounted inside the air boxes. The airboxes will no longer function as air filters as the air is filtered before entering the supercharger.
I am also looking at some new chargecooler developments from the drag race and drift world of motorsport where the chargecooler flow is laminar through a chamber similar to an exhaust straight through silencer and am currently leaving this option open. I can also boost charge cooling with a CO2 cryogenic system, but as this is not sustainable and relies on carrying a compressed bottle of CO2, I consider it cheating.
See here for a basic description of chargecoolers.
http://www.paceproducts.co.uk/public_html/php/prod...
The reason for my choice of a slightly more difficult option is actually many fold. I concluded there was insufficient frontal area on an 8-Series for an adequately unshielded air to air intercooler, but there was plenty of room for chargecoolers which do not require ANY cooling airflow at all, I have a ready supply of circulateable water in my Euro CSi washer bottle and have a further 9 litres in the boot reservoir, these bottles also have their own level sensors, and chargecoolers are far more efficient than intercoolers. The water circuit is therefore closed loop with the only losses being when washing the windscreen. I HOPE!
There is room ahead of the main radiators on the E31 for a large chargecooler radiator or two small ones, as I have yet to decide whether to use two pumps and radiators for the two chargecoolers or a single pump and radiator system, for now it will either be a single large aluminium radiator, or two motorcycle engine radiators. The pump(s) will draw cold water from the washer reservoir, circulate it through the hot chargecoolers and then return to the reservoir via the cooling radiator(s).
I had considered the Laminova range of coolers but concluded that a number of them, approximately 9 in fact, would be required to flow sufficiently, so whilst I still hold the opinion that these are the perfect oil coolers, they are not really suitable for my chargecooler application.
So there we have my designs for the engine and charge cooling systems, next up will be the fuel cooling system.
Stay Tuned,
and as that old saying goes "Injection is nice but I'd rather be blown"
8Tech.
CHARGECOOLING.
Charge cooling involves the cooling of the air entering the engine cylinders
known as the inlet "charge".
As you may well know, whenever air is compressed, either by way of a turbocharger or a supercharger, the resultant compressed air temperature is increased. This is not due, as some believe, to the proximity of the air to the glowing hot turbocharger, but by the energy contained within the gas.
See here…
http://en.wikipedia.org/wiki/Ideal_gas_law
This increase in temperature reduces the density and therefore the oxygen content of the charge, and greatly increases the chance of engine combustion getting to the detonation threshold. It is therefore of great importance to reduce this charge temperature as far as possible. Cold dense air will produce more power than hotter air at higher pressure that contains less oxygen.
The easiest and most popular method is by using an air to air intercooler which passes cold external ambient air through a (usually front mounted) aluminium radiator, through which the hot compressed air is passed, cooling it in the process. The other main option, and my choice in this case, is the air to water intercooler generally referred to as a chargecooler. This more complex system uses a radiator sealed within a chamber through which cold water passes, transferring the heat from the compressed air into the water which in turn has a small radiator, reservoir of approximately one to two litres and a pump to circulate it and expel the
absorbed heat to atmosphere, further compounding global warming!
My system will NOT be intercooled but will utilise a CHARGECOOLER similar to the Aston Martin and Jaguar system but with its own pump, tank and cooler rather than using the engines coolant system.
This is a method of cooling the hot incoming compressed air charge from the supercharger as it passes through the chargecoolers (air to water radiators) mounted inside the air boxes. The airboxes will no longer function as air filters as the air is filtered before entering the supercharger.
I am also looking at some new chargecooler developments from the drag race and drift world of motorsport where the chargecooler flow is laminar through a chamber similar to an exhaust straight through silencer and am currently leaving this option open. I can also boost charge cooling with a CO2 cryogenic system, but as this is not sustainable and relies on carrying a compressed bottle of CO2, I consider it cheating.
See here for a basic description of chargecoolers.
http://www.paceproducts.co.uk/public_html/php/prod...
The reason for my choice of a slightly more difficult option is actually many fold. I concluded there was insufficient frontal area on an 8-Series for an adequately unshielded air to air intercooler, but there was plenty of room for chargecoolers which do not require ANY cooling airflow at all, I have a ready supply of circulateable water in my Euro CSi washer bottle and have a further 9 litres in the boot reservoir, these bottles also have their own level sensors, and chargecoolers are far more efficient than intercoolers. The water circuit is therefore closed loop with the only losses being when washing the windscreen. I HOPE!
There is room ahead of the main radiators on the E31 for a large chargecooler radiator or two small ones, as I have yet to decide whether to use two pumps and radiators for the two chargecoolers or a single pump and radiator system, for now it will either be a single large aluminium radiator, or two motorcycle engine radiators. The pump(s) will draw cold water from the washer reservoir, circulate it through the hot chargecoolers and then return to the reservoir via the cooling radiator(s).
I had considered the Laminova range of coolers but concluded that a number of them, approximately 9 in fact, would be required to flow sufficiently, so whilst I still hold the opinion that these are the perfect oil coolers, they are not really suitable for my chargecooler application.
So there we have my designs for the engine and charge cooling systems, next up will be the fuel cooling system.
Stay Tuned,
and as that old saying goes "Injection is nice but I'd rather be blown"
8Tech.
Arr my favorite subject.
Chargecoolers ARE NOT more efficient than intercoolers when looking at overall efficiency (i.e. reduction of charge temperature in relation to outside air temp - which is what counts). They are more efficient when you look at the first stage of charge air into water, but you need to cool that water down again - the second stage.
Because a chargecooler has two stages and a air to air system has one stage, it wont match its efficiency.
My advice is in the first instance, try to fit an intercooler - if you just cant get one in, then look at air/water. Before rushing out to by one of those barrel type coolers, ask the seller what its efficiency is, you may get met with a wall of silence.
What is suprising is that very few people actually measure how efficient their inter or chargcoolers actually are, they just trust what they are told. Its actually quite easy to do and i reccomend you try it.
air to water systems are ok for drag racing, where you can fill the water chest up with ICE and get over 100% overall efficiency, plus the large water tank acts as a damper to knock the high spots off the inlet temp. But remember, the more water you have - the longer it takes to cool it. You need about 40 square inches of pre-radiator at the front to dump the heat.
I have spent considerable time designing and refining my own chargecooler system - I'm not an expert, but you can read about it here:
http://www.mez.co.uk/turbo8.html
Eliot.
www.mez.co.uk
Chargecoolers ARE NOT more efficient than intercoolers when looking at overall efficiency (i.e. reduction of charge temperature in relation to outside air temp - which is what counts). They are more efficient when you look at the first stage of charge air into water, but you need to cool that water down again - the second stage.
Because a chargecooler has two stages and a air to air system has one stage, it wont match its efficiency.
My advice is in the first instance, try to fit an intercooler - if you just cant get one in, then look at air/water. Before rushing out to by one of those barrel type coolers, ask the seller what its efficiency is, you may get met with a wall of silence.
What is suprising is that very few people actually measure how efficient their inter or chargcoolers actually are, they just trust what they are told. Its actually quite easy to do and i reccomend you try it.
air to water systems are ok for drag racing, where you can fill the water chest up with ICE and get over 100% overall efficiency, plus the large water tank acts as a damper to knock the high spots off the inlet temp. But remember, the more water you have - the longer it takes to cool it. You need about 40 square inches of pre-radiator at the front to dump the heat.
I have spent considerable time designing and refining my own chargecooler system - I'm not an expert, but you can read about it here:
http://www.mez.co.uk/turbo8.html
Eliot.
www.mez.co.uk
eliot said:
Arr my favorite subject.
Chargecoolers ARE NOT more efficient than intercoolers when looking at overall efficiency (i.e. reduction of charge temperature in relation to outside air temp - which is what counts). They are more efficient when you look at the first stage of charge air into water, but you need to cool that water down again - the second stage.
Because a chargecooler has two stages and a air to air system has one stage, it wont match its efficiency.
My advice is in the first instance, try to fit an intercooler - if you just cant get one in, then look at air/water. Before rushing out to by one of those barrel type coolers, ask the seller what its efficiency is, you may get met with a wall of silence.
What is suprising is that very few people actually measure how efficient their inter or chargcoolers actually are, they just trust what they are told. Its actually quite easy to do and i reccomend you try it.
air to water systems are ok for drag racing, where you can fill the water chest up with ICE and get over 100% overall efficiency, plus the large water tank acts as a damper to knock the high spots off the inlet temp. But remember, the more water you have - the longer it takes to cool it. You need about 40 square inches of pre-radiator at the front to dump the heat.
I have spent considerable time designing and refining my own chargecooler system - I'm not an expert, but you can read about it here:
http://www.mez.co.uk/turbo8.html
Eliot.
www.mez.co.uk
Hi Eliot,Chargecoolers ARE NOT more efficient than intercoolers when looking at overall efficiency (i.e. reduction of charge temperature in relation to outside air temp - which is what counts). They are more efficient when you look at the first stage of charge air into water, but you need to cool that water down again - the second stage.
Because a chargecooler has two stages and a air to air system has one stage, it wont match its efficiency.
My advice is in the first instance, try to fit an intercooler - if you just cant get one in, then look at air/water. Before rushing out to by one of those barrel type coolers, ask the seller what its efficiency is, you may get met with a wall of silence.
What is suprising is that very few people actually measure how efficient their inter or chargcoolers actually are, they just trust what they are told. Its actually quite easy to do and i reccomend you try it.
air to water systems are ok for drag racing, where you can fill the water chest up with ICE and get over 100% overall efficiency, plus the large water tank acts as a damper to knock the high spots off the inlet temp. But remember, the more water you have - the longer it takes to cool it. You need about 40 square inches of pre-radiator at the front to dump the heat.
I have spent considerable time designing and refining my own chargecooler system - I'm not an expert, but you can read about it here:
http://www.mez.co.uk/turbo8.html
Eliot.
www.mez.co.uk
I appreciate your experience here and the comments you make. I have looked into this quite deeply and wonder if you could clarify/explain a couple of things from experience please.
You say that overall efficiency between ambient and charge temperatures is what counts. I would suggest that the only efficiency we are really concerned with is the reduction in charge temperature between the inlet and outlet of the cooler. THIS is the only efficiency that counts surely? Who cares what the ambient temperature is? We are concerned only with charge temperature as it enters the motor, so to hell with the pre-rad efficiency/area as long as it keeps the charge temps down!
Not sure if you are familiar with the front of the E31 but there is very little frontal area open to airflow and most intercooler systems on theses cars are masked by the front bumper panel so you are absolutely correct when you suggest the correct cooler type for the installation constraints. (Read your web link).
I was going to fit inlet and outlet charge temperature sensors on the coolers to assess their efficiency but as I would have to fit both systems to the car for assessment and comparison, then junk the least efficient, I decided to try and get it correct first time by design and save a whole lotta wasted work and money.
I believe it pretty unfair to ask the cooler manufacturers for an efficiency because it relies on so many variables and would be virtually impossible to make a comparison without having a standardised system such as fixed temps, flow rate, frontal areas etc. Whilst it would be great to put them on the spot, I don't think its a fair question to ask.
You quite rightly state, "the more water you have - the longer it takes to cool it.", it also follow that "the more water you have - the longer it takes to HEAT it.", and with a decent sized pre-cooler, and the inlet temp only adding heat to the system whilst actually boosting, (only a small proportion of the time on a road car), the system only needs to transfer the heat from the boosted proportion of the drive over the entire driving time. I am aware of the ice etc and as I said in the original post but re-iterate that I see these as not suitable for a road application. I also have a 144 square inch, 2 inch thick pre-rad so I would really appreciate your feedback on how this would compare to the 40 square inch requirement you suggest.
I am sorry if this response to your post sounds aguementative, it is certainly not meant to be, and I would really appreciate your experience in this matter to explain where I may have gone horribly wrong, or some major consideration I have overlooked.
Regards,
8Tech.
8Tech said:
You say that overall efficiency between ambient and charge temperatures is what counts. I would suggest that the only efficiency we are really concerned with is the reduction in charge temperature between the inlet and outlet of the cooler. THIS is the only efficiency that counts surely? Who cares what the ambient temperature is? We are concerned only with charge temperature as it enters the motor, so to hell with the pre-rad efficiency/area as long as it keeps the charge temps down!
Overall efficiency matters, because the ambient air temperature was what air temp you started with and your'e trying to get your inlet temp as close to that temp as possible. No point having 100% efficient chargecooler if your inlet temperature is still 50'c over ambient because your water is 25% over ambient. You are assuming a limitless supply of cold water, which you dont have. So consider the whole package, get the best CC and the bigest pre-rad you can fit in. The water tank just helps balance things out, it knocks the spikes of the temperature for longer when blating past someone. If you do little bursts (<10 seconds) it works quite well, but sustained periods of boost will require large radiators to dump the heat out.
I need to find the reference to 44square inches of pre-radiators, its possibly wrong. Just checked mine, one is 20x8 and the other is 20x6 giving a total of 280 sq inches. They take a several minutes of normal driving to get the temps back down - but thats fine, as it gives my brakes a chance to cool down too.
8Tech said:
You say that overall efficiency between ambient and charge temperatures is what counts. I would suggest that the only efficiency we are really concerned with is the reduction in charge temperature between the inlet and outlet of the cooler. THIS is the only efficiency that counts surely? Who cares what the ambient temperature is? We are concerned only with charge temperature as it enters the motor, so to hell with the pre-rad efficiency/area as long as it keeps the charge temps down!
That is right in a way. We can all measure the efficiency of the core, as whether hot air in or cold air in, we should see the same temperature drops at the end of the core. Measuring the 'whole' efficiency of a chargecooler system is difficult, as this all depends on placement of the pre-radiator, tank, volume of water, engine intake filter temperatures etc. So one set of efficiencies from one test vehicle will not relate to another vehicle. It could be all measured on a bench, but then these figures would be 'best case scenario' and probably never acheived in real life.Its the same with traditional air-to-air. Test efficiency figures can be given, but whether they will be acheived when fitted to a vehicle, is a different matter.
Rule of thumb though, and with actual real world vehicle installations, I have always seen around 20c above ambient max (sustained) in a well designed system using 4" PWR cores, on various vehicles, flowing no more than 400cfm, 20psi. The larger cores respectively can cope better at higher levels.
David
www.chargecooler.co.uk
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