James Paventi

iTrader: (34)

Hi All,

I'm curious how many folks have tried mimicking the pill that's in the stock AST, with their aftermarket AST, and what difference they have noticed.

I have an aftermarket previously used aluminum AST. I don't know what brand it is as the seller didn't know. This is coupled with a Fluidyne radiator and 50/50 standard antifreeze.

I've had noticed that driving around town in 75 ish degree weather tends to either hold the coolant temp or let it rise. Put another way, it rises at a red light and then holds at 35-45 MPH. As soon as the fans come on it drops ... slowly at a light and more rapidly if cruising. My fans are set to come on at about 200 deg F via a PFC.

After reading many a thread I learned that the stock AST has a 0.7mm pill in the outlet line. After a quick trip to the garage this was confirmed. It cost a bit of coolant but I confirmed that my aftermarket AST has no plug.

My understanding of the pill is that it limits the amount of hot water bypassing the radiator and thus water that is not being cooled.

I purchased a number 70 Holly carb jet (brass) off of ebay and installed in into my AST.

I've driven my car around for close to a month with this set up now. I've observed a few things:

First when warming up i the morning the thermostat seems to open at 182F instead of 185F. Well, I'm saying that wrong. I should say that my digital water temp gauge shows temps rising and then holding at the above mentioned temps. The gauge sensor is located in the throttle body coolant line. Also when leaving a red light the temp will briefly drop to 179F. It didn't drop at all before.

Second, around town cooling will drop the temps now. OK, so a long stint of 45 MPH cruising would drop the temps from say 200 to 190 prior to the pill addition. How long? Let's say about three green stop lights. Now it's roughly 1/3rd of the distance.

Last thing. If I manually trigger the fans before parking the car, the temps drop much more rapidly. As it stands I can hit the switch about 75 yards from my driveway vs 150. When I park the temp is 185F.

I've made a couple of trips on the freeway and am not so convinced that it makes a noticeable difference here. My current theory is that there is so much coolant flow at higher RPMs that it doesn't matter if the AST has a pill or not.

So, can anyone confirm?

James

Julian

iTrader: (14)

Don't know effects of with and without as I have always used a pill. When I installed a Pettit AST I epoxyed in a pill (I cut it out of old plastic AST) before ever installing. You are right, it will retrict the radiator by-pass, does it make a differnce ..?? but I figured Mazda went to trouble of putting one in so why not keep the same. Somewhere on this site I have a post on the subject.

adam c

iTrader: (2)

There are a lot of manufacturers of aftermarket AST's for our cars. As far as I know, none of them place "pills" or other restrictions in the AST's. I don't think a pill there will give you any meaningful improvement in your cooling .

For better cooling, I suggest turning the fans on at a much lower temperature. This will have the most effect when driving in stop and go traffic when there is very little airflow thru the radiator. My fans are set to come on at 85C.

My throttle body coolant temp readings always seem to be about 5 degrees lower than the readings on the PFC. Have you compared the two?

ttmott

iTrader: (1)

If there is no restriction the water pump will be circulating coolant in a loop between it and the radiator bypassing the engine. If the AST is getting hot this is the case. The restriction is there to allow gasses to vent to the AST but limit the coolant recirculating.

James Paventi

iTrader: (34)

I hear you Adam. It's hard to say what effect that the pill has when my testing isn't exactly scientific. Oh, and yes I have noticed the PFC vs gauge delta ... though I've never paid attention to how sizable it is.

What about one of the folks out there that has closed the heater core loop? Any one of you care to chime in. I recall reading a few threads where this was done to increase flow through the radiator on the track.

adam c

iTrader: (2)

Many have simply eliminated the AST from the system. I would be curious to hear if there was any effect on cooling. I cant imagine it would be a change of more than a degree or 2 (F).