hey guys, I was curious as to what ecatly the ast is. all i know is that it has somthing to do with maintaining the twin turbo system ..maybe.. help plz?https://www.rx7club.com/images/icons/icon9.gif

 

great no one noes, thanks guys...

 

from the fd3s.net website. Maybe experts can comment:

"I occasionally get into a compulsive rut which is difficult to shake while my old brain struggles to understand something without my conscious intervention. It has happened again this time with the Air Separator tank on my '93. Since buying my car last year, I cannot quiet this little voice in my mind which keeps asking what the air separator tank's purpose is, why it is needed, and how it functions, and it it has anything to do with the significant number of engine failures apparently due to overheating. I have assumed that Mazda needed this additional piece of plumping in the cooling system, otherwise it would not be there. Here are some questions, thoughts, findings and perhaps even conclusions which I've reached, so far, and the results of some experimenting.

1. The system seems to be designed to eliminate tiny bubbles from the coolant, not to bleed the system of air. I've taken a look at the coolant at the top of the air separator tank and found it cloudy. I took a sample of the cloudy coolant and it became clear, like typical anitfreeze, after a week of sitting.

2. The presence of these tiny bubbles in the cooling system will significantly reduce the heat transfer efficiency of the coolant. Mazda engineers must have recognized this during the 3rd gens development and added the air separator tank to eliminate (reduce?) the problem. I have never seen an air separator tank on any other car. Has anyone else? Does anyone know of any other car which has an air separator tank?

3. So, where do these tiny bubbles come from? The only place I can figure is that it is the gas (essentially atmospheric gases) dissolved in the water and/or coolant when the cooling system is freshly replaced. The concentration of gas in a liquid is inversely proportional to temperature, so the higher the temp, the smaller the amount of gas which can be dissolved in the liquid, in this case the coolant/water mixture. But once these gases are removed from the coolant, the air separator tank would serve no useful purpose until the next time the coolant is changed and the dissolved gases again needed to be eliminated. Or, is there some other source of gas?"

 

The AST is simply a cleaner better way of containing the air spring....

all cooling systems require a certain amount air to be retained in the system in order to allow the water to expand as it is heated up. In most street cars this air is accumulated in the top of the radiator or wherever the radiator cap is, however with this air trapped in the flow path of the cooling system small amounts of air gets circulated though the system. Header tanks/ASTs are a common thing in race cars since it is imperative that the cooling system work as efficiently as possible. they work by maintaining the air spring out of the the normal flow path of the sytem...mazda recognized the need for the cooling system to be as efficient as possible for the 3rd gen and thus chose to include an ast...to bad they didn't predict the material used would not withstand the test of time.

hope this helps

 

no, it has nothing to do with the twin turbo system.. It stands for air seperation tank, it seperates the air from the coolant and out of the system, because air bubbles in the chambers can cause hot spots and premature engine failure.... The stock ast is known for randomly breaking causing overheating and engine failure. Alot of people upgrade to an aluminuim ast from pettit etc... Some people even say its ok to remove it... DO NOT listen to these people they have been lucky and will find out the hardway.