NLR: FD Type I S6 - Coolant filler neck/thermostat housing

[Black Talon]

and installing a separate 2 stroke oil tank in its place to feed the OMP Lines (rather then dirty sump oil) Though not sure if the adapter block off plate will fit with the standard twins!

It fits... But it's tight. I've helped fit one to a car with stock turbos.

[gav240z]

Yep... It makes it just like every other car in the world, in that it doesn't have a silly AST to fail and kill your motor.

I would be all for this mod, however isn't the whole point of the AST to separate air (bubbles) from the coolant and therefore make the cooling system more efficient? Which is critical in a rotary -especially a forced induction unit like the FD?

Does the R-Magic tank still perform the same task as a stock AST?

[Suprspt]

This led me to believe the 2 piece units may have failed over time...
or broken when placing the cap on?? Food forthought...

Raise your dead!

Doubt there's much likelihood. Mazda and Ford beancounters at the helm would be paring away the cents any way they could.

[Babalouie]

Does the R-Magic tank still perform the same task as a stock AST?

From the shape of it, at first I thought that it might perform a similar bubble-removal process as the AST.

But I'm not sure if it does....with the AST, the volume of the incoming coolant (in the little tube) is very small compared to the volume of the AST itself. So I think in that context any bubbles stay at the top, and bubble-free coolant returns to the system at the bottom.

I've always wondered why only a % of the coolant goes thru the AST, rather than all of it, but I reckon that with that R-Magic thingo, that cylindrical section isn't much bigger than the incoming coolant volume, so it'll be roughly the same result as a rad hose that turns 90 degrees?

[Qqc]

the ast is not a needed device provided the system is bleed properly its that simple. Is the ast a good idea well that debatable and you will probably never come up with a definitive answer.
if the system is bleed propely and the overflow pickup has enough coolant covering the pickup in my opinion there is no benefit to an ast as air simply can not enter the system.

[Black Talon]

The simple fact is this... The AST doesn't need to be there. The AST itself DOES NOT perform the function of removing air from the cooling system.

That's what the pressure cap and expansion tank do.

Ideally you want the pressure cap to be the highest point in the cooling system. The stock position of the AST is far from that. The filler cap however IS the highest point on the block (with the exception of the throttle body feed for the cold start system).

All you need to remove air from the system is the pressure cap, and the expansion tank system. You also need somewhere that any small amounts of air can collect (usually the top again).

The other simple fact is that 99% of cars out there don't run a separate AST system like the FD has. There simply isn't any real need for it. The FC didn't have one. The RX-8 doesn't have one. No other Mazda rotary engined road car ever had one either.


If it was such an awesome system, why didn't Mazda keep it for the RX-8? It has what most Fords have, which is a large tank high up in the engine bay, with the pressure cap on that, and no extra expansion tank. It essentially stores a volume of coolant higher than the engine. Any small amounts of air trapped in the engine work their way to the top and are no longer a problem.

The expansion system stores the extra volume of coolant where ever you fit the tank. The feed for the expansion tank is usually in the top of said expansion tank, but there is a hose running to the bottom of the tank. Coolant comes in to the bottom of the tank, and if there is any air mixed in with it, the air floats to the top and is no longer a problem.

Both the Ford/RX-8 system, and the regular expansion system rely on that extra volume of coolant and the pressure cap to remove any air in the system. The FD system is no different with the AST or without it. Either way you're relying on the expansion tank and pressure cap to remove air.

The AST is just an extra failure point. I have no idea why Mazda decided to fit the AST like they did. I can only assume it was because someone said "race cars have them", or because of the packaging of stuff around the filler neck (which is the logical place to put the pressure cap).

[Ravell]

I have no idea why Mazda decided to fit the AST like they did. I can only assume it was because someone said "race cars have them", or because of the packaging of stuff around the filler neck (which is the logical place to put the pressure cap).

I'm surprised an left wondering why no one at Mazda during development or in the 10 years that the car was manufactured ever suggested removing or changing the system, considering it would increase reliability and reduce cost.