What is the benefit of the coolant passing by the BAC? I'm finishing up the engine rebuild, and would like to delete these water lines. I just want to rin through the TB for the Idle up system. I live in the Northwest so could it ice up under certin conditions?

 

That was probably their thinking. Really, you might as well leave it. Since you're still using the thermowax, the water has to run back to the water pump. What other route would you send it? Over/under the manifold? You'd have to bend a water line and hope it doesn't kink.

 

it is there for de-icing .. i dont use the coolant path .. but where i live today will be 100+ F

 

I don't believe it was for de-icing and if it was, it's a terrible design.
I think Mazda was more interested in keeping the BAC solenoid at a steady state operating temp, not too hot, not too cold.

 

Could use some of your heat
Bumpstart.

 

I posted this in a thread about this a long time ago:



read the bottom. You can bypass the coolant. I've done it before. I'm not sure how cold out it would have to be for icing to be a real issue, especially since it will warm up underhood and that could melt ice. Basically every electronic throttle in modern cars come with a throttlebody cooling line for a similar de-icing function, and ice is also an issue on EGR valves (especially for diesels).

I'd say delete the hose and you probably won't have any noticeable negative effects. Now, deleting the coolant hose from the throttlebody screws up the thermowax/fast idle functionality.

 

Thanks all, great help. I found the 3 lines for under $50, and the weather we have around here. We seem to have the right conditions here for old fashion carb ice. I will just order them.

 

Interestingly, the FD BAC loses the coolant feed.

Anytime I standalone a car it loses both the thermowax and BAC cooling feed. Never had an issue so far of either icing nor overheating of the valve. I can see icing, under VERY cold circumstances, just like the carb on my '78 SA used to ice up sometimes. Fact is that the S5 NA and TII BACs are directly above the exhaust manifold so if they do ice, it will be temporary.

 

Could I thread jack my own thread? Does the BAC air have to be post turbo? if not, seems it would still have to be post AFM.

 

the GSL-SE didn't have a coolant fed BAC either. while not icing, and a constant coil temp are nice, i'd bet it also makes hose routing neater and more logical, imagine the hose routing if it didn't go through the BAC, it would just have one 10 foot long floppy hose just rubbing on everything.

 

it needs to be after the AFM, but before the throttle.

 

Now I'm thinking more towards delete. Going to try some hose routing. If nothing looks right I'll just buy the new hose set. Thanks