Coolant Capacity Tank
 

Has anyone ever considered a coolant capacity tank?

The nose of the 99 spec / oem bumpers have limited air flow, and the width/height of the FD's chassis is limited. When trying to run displacement/higher horsepower, this can be a challenge as the radiator can only be so tall/wide. Making the radiator thicker will certainly help at adding capacity, but this is going to require the expense of custom radiator etc.

I have yet to see this on any car, but what if rather than building a thicker radiator (which is about the only option for higher horsepower), add a coolant tank somewhere in the engine bay. Much like the size of a dry sump tank, made from metal, to hold coolant/pressure. You could even add a filler cap top it for easy bleeding. Much like a large remote mount AST, that could hold maybe 1/2 gallon - 1 gallon of coolant.

This should increase the capacity of the system and take stress off the radiator as more coolant will be held outside the engine block, and while the car is on decel/idle there is much more coolant to heat up?

Not sure the point as a tank would probably provide little heat transfer and the added capacity would strain the water pump. Better would be adding another radiator. I've seen several track cars that added a radiator in the back

I was just thinking since its using an electric water pump direct -an fittings to the engine, maybe a tank would bel beneficial as it would increase the overall volume of the system. So if say the system typically holds 2 gallons and we increase that to 4 gallons, now it takes considerably longer for load situations to heat the water.

So lets say the car does fine w its typical capacity as removing heat at idle and low load, but going on load uphill etc temps begin to climb. Well if the volume is doubled, then the temps would rise at slower rate. Of course it would also take longer to get rid of the heat once it finally soaks, but that heat can be dissipated when the car returns to off-throttle situations.

Kinda like water tanks that people use with intercooler w2a setups. Running a large tank so that temps dont rise during boost, and then when car is cruising the heat exchangers removes that added heat.

So here's the idea,

Mount a tank, much similar to this accusump setup. Run the coolant via 16an fitting out of the bottom of the radiator, into the tank, back out of the tank and into 16an fitting on EWP. A tank this size should hold between 3-4 liters which adds about 30% extra volume to the cooling system. Although a larger radiator or extra radiator would hold more coolant AND get rid of the heat, I really wonder how much benefit could be had by adding only capacity. Adding more fluid should buy the radiator more time before reaching critical temps...really want to see if there's any concrete thoughts on this

https://cimg4.ibsrv.net/gimg/www.rx7...75fcf66c85.jpg

Think it's just going to store hot coolant. Agree that you may get some initial benefit when the system is cold for the cold coolant in the tank to work it's way through, but after it does, when the coolant comes up to temp, I don't see any benefit.

The oil sump (which may have initiated this thought) is more to maintain oil pressure vs oil temps

All that said, there's one way to find out, and that's to install one and see if it works. You could probably rig a temp tank and take (somewhat) controlled experiments before and after to see if there's any difference.

I think it would be more beneficial to run a 3" core radiator like Griffin LS-style (notice the path is similar to OEM?) and dual FC oil coolers in series with an external thermostat (180F should be fine).

Watching all of the Rx7 racing videos, you can see that OIL temp is the huge issue here, and as oil temp rises, coolant temp will rise with it (and vice-versa). Both should be upgraded proportionally with power upgrades...

The accusump only works on oil systems because the oil pan has headspace. You dump an extra quart of oil and theres room for it to go. The coolant system has no air room and is sealed, so nowhere for that extra coolant to go.

The accusump also gets filled with engine oil pressure. When the charged oil pressure in the accusump is higher than the oil in the galleys, it has driving pressure. For the accusump to be able to even move coolant, it would have to be higher than system pressure. Even then, if it was able to discharge, it would displace whatever coolant you were adding right out the overflow, or worse, over pressurize the coolant system and potentially damage a water seal.

Thanks for the comments.

I understand what an accusump is an how it works. The picture was shown to illustrate how/where/what size and type of container could be mounted to increase capacity.



3 gallons of water takes longer to heat than 2 gallons of water. Having 3 gallons of water running at 180F and then going on boost for 15 seconds etc is going to rise less in temperature than 2 gallons water, as there is more fluid to absorb the heat. This is the idea behind adding volume to the system.

Why not add volume in the form of more heat exchanger? That way that waters not just acting as a buffer, but actvely cooling. A spare volume would work for the first pull, then become heatsoaked and have marginal benefit.

i think a small increase in capacity would be really good. however the trouble is that it takes longer to heat up, which is good, it will also take longer to cool down, which is bad.

basically if the engine makes x BTU's/time, the cooling system either needs to have the same number of BTU's or more time.

not saying more capacity is bad, in fact i think a small increase is probably good, just saying there is a tradeoff

I would just stack 2 radiators and plumb them in series.

I think you would be better off with a EMP. The main advantage to them is they can move the water to suit the temp. Regardless of the engine RPM. my EWP setup i've never been able to get close to over heating. And in Australia I normally only take it out on 100F days.

I would contact Ron Davis and speak specifics to one of their experts on the subject. You may find they can calculate the ideal size for the BTU's for your application. Good Ducting, fans and a proper sized core will be essential. give them available dimensions and they should be able to make the radiator to fit your needs given you have the volume of space to accommodate it.

But if you want a best guess from the peanut gallery I would say to take what a 2 rotor turbo requires and double it. Also your capacity will have increased just from adding the extra rotors. The extra fluid is in the motor and in the larger radiator.