Idea for better FMIC plumbing

[sambb]

Gary how does it work having a header tank located lower than the core itself or the heat exchanger (eg on the cars floor)? I always thought the header had to be the highest point in the system. If the header was in the engine bay, is heatsoak likely to be a drama? If the heat exchanger is sized correctly surely a well insulated header would be ok wouldn't it.
The other option for a heat exchanger I was thinking of is a VR6 auxillary radiator positioned where the side mount used to be infront of the drivers side wheel. That would help pull the weight back a bit but would be adding it to the already heavy side of the car too.


For pumps I was going to use two VW 1.8T auxillary coolant pumps (used in my car to circulate coolant around the turbo when the car is switched off) in parrellel as a failsafe.
Do you know if any of the old water to air IC cores from GT4 celicas/RS Legacy were good.

[simon k]

shouldn't matter which point is highest, as long as that's where the filler is. You might need to add an air bleed if there are high points... but not really a drama

[sambb]

But a header tank still has air in it by definition doesnt it so has to be at the top. That makes me think that it has to be in the engine bay a tad higher than the core but I could have that wrong. Seen a few cores where they have the pressure cap on the water jacket itself and no header (all the capacity is in the core and exchanger with no auxillary) but obviously with that system you loose water capacity and the ability to add ice. thinking seriously about this now. One of the things I've been told is that if you want to go E85 then you need rock solid temps. You cant be bunging loads of timing into a car and then have it leave the line at a hillclimb with 80 degree temps but its down near ambient as you cross the line - a recipe for engine death, so if I ever want to do E85 then water to air makes a lot of sense for really stable temps.

[Sydneykid]

Perhaps over thinking it Sam, it doesn't have to be a sealed pressurised system like an engine cooling system. In a long distance circuit race car we use a pressurised I/C system, but for short distance/time event like drags and hillclimbs it's not really necessary.

In the drag car systems the pump takes water from the bottom of the reservoir (ice/water) tank and pumps it directly into the I/C so it always has water in it. From the I/C it then goes to the bottom of the heat exchanger, forcing any air in it out of the top, through the return hose and back into the tank. The cycle continues, the air rises to the top of the tank, the pump picks up water etc. Much like a dry sump oiling system.

If the I/C is,say, the highest point then you could put an air bleed tap there, at say the hose return to the tank. It can be anywhere in the system that is the highest.

Keeping in mind that the "hot" water shouldn't be over 70 degrees (not 100+ like the engine coolant) and even then only in the short hose from the I/C to the heat exchanger. Which should then drop it back close to ambient, so the water in the return hose and the tank should be around ambient temp. Or lower if you use ice/water, until the ice runs out of course. The reason why engine coolant systems are pressurised is to raise the boiling point above 100 degrees. In the long distance race cars the compressor outlet temp often gets over 100 degrees, which could mean the water in the I/C boils, so that's why we use a sealed pressurised system. Unfortunately can't stop after every lap to fill it back up with ice.

Cheers
Gary

[Sydneykid]

Obviously in the race cars we have inlet air temp correction, so if the inlet temp changes the fuel and ignition maps move appropriately. If, say, we have leak in the water to air intercooler system which causes the inlet air temp to rise the ECU moves to the appropriate map to prevent damage. I'd be surprised if your ECU doesn't have that facility, if it does then you need to program it accordingly. If it doesn't then I'd suggest you fit an air temp gauge, in good line of sight. Keeping in mind that you could see inlet air temps from below ambient (with ice/water) to 70 degrees above it (system failure).

Cheers
Gary

[Sydneykid]

One of the things I've been told is that if you want to go E85 then you need rock solid temps.

Exactly the opposite, being alcohol E85 is many times more knock resistant than petrol, so it isn't anywhere near as sensitive to combustion temperatures. We try and run around 85 degrees water temp as that gives the most horsepower. But in traffic on a 40 degree day we can see temps over 100 and obviously we have engine temp correction mapping to compensate for that. Tuning wise we throw more E85 in it as it acts as a combustion temp coolant. But there's not much ignition timing correction as retarding it actually increases the combustion temperature.

In comparison petrol doesn't act anywhere near as well as a combustion temp coolant, so we really have to pump a lot more petrol in to make much difference. That's commonly not enough in the above example, so we have no choice but to retard the ignition to prevent the knock, which in turn increases the temperature, so we throw even more petrol at it. That circle of pain really kills the horsepower and eventually the engine, too much petrol washes the oil of the bores and we have ever increasing blow by and eventually ring sealing failure.

Swapping the same engine from pump 98 to E85 lowers the engine coolant temp by 10 degrees and the oil temp by 5 degrees. As a result there's more capacity in the cooling systems before they over heat to start off with.


Cheers
Gary

[simon k]

In the drag car systems the pump takes water from the bottom of the reservoir (ice/water) tank and pumps it directly into the I/C so it always has water in it. From the I/C it then goes to the bottom of the heat exchanger, forcing any air in it out of the top, through the return hose and back into the tank. The cycle continues, the air rises to the top of the tank, the pump picks up water etc. Much like a dry sump oiling system.

If the I/C is,say, the highest point then you could put an air bleed tap there, at say the hose return to the tank. It can be anywhere in the system that is the highest.

so in it's simplest setup, we could have the IC in the same position as the standard SMIC, the heat exchanger in front of the radiator and the reservoir sitting somewhere convenient like under a mudguard (or even repurpose the windscreen washer reservoir), yeah?

a for a club level circuit car (say 15 minute sessions), what is a practical minimum volume of the system you'd shoot for?

[Sydneykid]

so in it's simplest setup, we could have the IC in the same position as the standard SMIC, the heat exchanger in front of the radiator and the reservoir sitting somewhere convenient like under a mudguard (or even repurpose the windscreen washer reservoir), yeah?

Yep, I have seen a windscreen washer bottle used as a reservoir for an air to water I/C. Depending on capacity it could be a bit light on volume though. More commonly the windscreen washer bottle is used for the I/C water spray. I have also seen a 10 litre fuel can strapped in the boot used as removable reservoir, plumb it in for the event then remove it for road use.

a for a club level circuit car (say 15 minute sessions), what is a practical minimum volume of the system you'd shoot for?

Around 8 to 10 litres should do it, about 50/50 ice and water, that should give a reasonable number of laps at below ambient I/C temps. Obviously there are many variables, where the compressor sits in its efficiency curve, the ambient temperature, heat exchange efficiency etc. Of course when the ice runs out it still works as an I/C, just that you won't get below ambient temperatures.


Cheers
Gary

[simon k]

where the compressor sits in its efficiency curve

hey!!! what compressor? the turbo?

edit: 8-10 litres is more than I expected, putting it in the boot sounds like a good idea

[Redliner]

Have you seen the Frozenboost website. I am looking at doing a air to water intercooler setup on my S3. Frozenboost cores seem to have a reasonable reputation for the price.
Air/Water IC

Take a look at this link:
Big Turbo 20vt's Public Group | Facebook

Another interesting link based on a drag car but the calculations could come in handy:
Intercooler Design