Jeff20B

iTrader: (13)

The heater tube in beehive cars ('83-'85 12A) has a restrictor inline right up near the upper beehive coolant tube. This restrictor looks like a brazed-in washer. I assume this is to provide some restriction.

Why is this restrictor there? Is the restriction it provides necessary? Can I run a beehive without a restictor?

We know that running a waterpump with no thermostat is only ok if the bypass hole is blocked and a gutted thermostat is used. The gutted thermostat provide some restriction which is necessary for some reason.

I want to use a beehive on a project car and need maximum cooling efficiency. Should I tack in a washer in the steel line like stock? Or leave it totally open?

Edit: an air oil cooler is not really an option. It's gotta be beehive.

Nismo Convert86

iTrader: (7)

The restriction is there to slow the fluid down, and absorb some of the heat and take the heat to the rad, to have the rad disipate the heat.

Kentetsu

Doesn't make sense to me...

Jeff20B

iTrader: (13)

That actually does make sense to have a restrictor in the main cooling lines when looking at it from the radiator's point of view. However the reasons for having one in a beehive are a little foggy. Especially since the restrictor is in the tube leading up to the beehive, but not actually in the beehive itself. This gave Mazda the option to try it with a restrictor and without, and they settled on the restrictor.

I'm wondering whether the oil would get too cool without the restrictor. Or maybe too hot. Has anyone tried it both ways? I didn't want to be the guinea pig, but I will if I have to.

Nismo Convert86

iTrader: (7)

If something is free flowing it can't "sit" there long enough to absorb the heat from the metal. The restriction allows it to absorb heat out of the metal, and take it to the rad, and the rad will get rid of the heat. Keep in mind this is up to a certain extent, it can move fast enough with out a restrictor, and can remove the same or more heat.

Best I can explain it but it does serve a purpose, in this case i'm not too sure.

Jeff20B

iTrader: (13)

It will be on an engine that is expected to produce good numbers at low RPM. The ports are set up for best flow at or around 4000. I'll be using an FC NA waterpump which can spin reliably up to 7000 without cavitation (according to Racing Beat).

I understand that a restrictor is a good thing, and there is a reason Mazda used one, but the option exists to try it without the restrictor, so I think I will.

Nismo Convert86

iTrader: (7)

Just remember Mazda didn't always do things for performance, it was reliability, if the heat sits there too long, it could warp stuff, HIGHLY unlikley but there are 2 sides to everything. Like you said you can try it both ways.

Kevin

j9fd3s

iTrader: (3)

id use no resistor, i dont see why it wouldnt work

j9fd3s

iTrader: (3)

i would take out the restrictor too

trochoid

iTrader: (6)

Jeff, I have to say you come up with some of the most interesting and thought provoking threads.

I have a question or 2 for greater clarification though. Exactly where is this restrictor located you are refering to? I don't have anything handy that is apart to look at. As most of us know, the heater tube coming from the rear iron on the beehive equipped engines is a tee, the fmoc engines have a straight tube. To match the extra coolant line for the beehive, i.e. supply line to it, there is a 2nd tee where the coolant line connects to the heater core at the firewall.

This tee connects the supply line to the heater core and the beehive. The leg of that tee goes to the heater core, the straight run goes to the beehive. Fluid prefers the path of least resistance, i.e. straight and not curved. If this is the restrictor you are refering too, it may be there to simply direct more coolant to the heater core.

If there is another restrictor, where is it located? If it's the one on the firewall you are refering too, and not running a heater, I see no need for the restrictor.

13BT_RX3

A restrictor oriface is used to limit flow by means of pressure drop. There is a possibility that the beehive will start to leak from too much pressure after you remove the oriface. The behive itself probably cannot flow much more than the oriface lets through anyhow. I would not do it.

trochoid

iTrader: (6)

Since were talking about coolant pressure on one side and oil pressure on the other, if the restriction is only on the coolant side, I can't see pressure as being a problem. Max pressure for the coolant occurs after the engine is shut down and it goes into heat sink where the temps stabilise throught the entire engine. This is when the rad cap will release excess pressure and allow coolant to go into the overflow tank.

If the beehive can sustain those pressures, under what, 15 psi, then removing the restrictor should not present a problem.

Naegleria_Fowleri

This is what makes most sense to me.

13BT_RX3

Good point!

Maybe not pressure? Maybe just a heat trasfer calibration to balance the 30% rejection through oil.

What is normal oil operating temp anyway?

trochoid

iTrader: (6)

The 30%, afaik, applies to the fmoc equipped engines. What percentage the beehive rejects, no clue, but I would venture a guess that it's not under 20%.

I have seen posts where the oil temp with the fmoc has been measured to be near the coolant temps with aftermarket gauges and most seem to be under 220*F. I don't know what a good oil temp would be, but I would think anything over 250 is not good.

13BT_RX3

The only other problem I can find with removing it is that it may over tax the radiator. If you have a nice radiator or are in a cool climate with lots of rain this may not be an issue for you.

Rogue_Wulff

Considering the return from the beehive goes into the lower radiator hose, and right back into the engine, the radiator is the least of the worries with a beehive. Coolant has to make 2 trips thru the engine before returning to the rad, if it has gone thru the beehive.
I believe trochoid has nailed it. The restrictor is used to help water flow into the heater, rather than all of it going thru the beehive.

Jeff: If this project is one that is gonna require a beehive, why not tap into the backside of the water housing, on the cool side, for the supply, and make the return flow back to the rad. This would provide cooler water to the beehive, and prevent the heat from the oil heating up water that will then flow back into the engine.
I realise that this could lead to having the oil actually cooler than what a FMOC will provide, and possibly even cool the oil "Too well". Would too low of oil temp really cause a problem? I don't know. We all know the results of having higher oil temps normally associated with a beehive. (oil control seals and dowel pin leaks)
I suppose a manual heater valve could be used to regulate the flow of water into the cooler, if having too cool oil temp is a potential for problems.

13BT_RX3

Run a separate radiator for the beehive. J/K.

trochoid

iTrader: (6)

I tried to find a full diagram of the cooling system flow, similiar to the oil system one. As near as I can tell, the tee at the heater core is the supply for it and the beehive. The other line off of the beehive ties back into the tee, along with the heater core on the rear iron.

It may seem odd that the return goes back to the hotter part of the engine, but I don't think returning it to what would be the lower radiator hose would work since the radiator has a top to bottom flow direction.

The other reason for thinking it flows this way is how effective would the beehive be if it's cooling source was from the hotter part of the engine, instead of after passing through the radiator?

Jeff, you can chime back in anytime. I will be posting pics in the other thread, had too many delays with other work to take them yet.

Rogue_Wulff

Sorry trochoid, but the flow is actually FROM the rear iron, thru the beehive/heater, then returns to the lower hose, and back into the engine. Lower hose is suction from the rad, and the rear iron has flow from the pump pushing water out the nipple.
As for how effective it is, well, it ain't. Hence the cooked oil control and dowel pin o-rings. It simply cannot lower the oil temp to less than 180F, as that is the designed water temp.

trochoid

iTrader: (6)

That's why I was looking for a flow diagram. But now that you mention suction, I do remember seeing a lower radiator hose collapse at high rpms, so your flow pattern makes more sense. I keep thinking the water pump pushes the coolant through the top rad hose, instead of actually pulling it through the rad from the bottom hose.

No need to apologise, I questioned the way I thought it flowed as it was. It didn't seem quite right the way I had it layed out in my head. For me, correct information on the forum is much more important than ego, and I try not let mine get in the way, most of the time anyway. lol

Jeff20B

iTrader: (13)

The beehive coolant flow direction goes from the lowest point to the highest point. Put simply, it allows bubbles to burp through. It flow from the rear plate up through the beehive, through, and into the steel coolant tube on the firewall. The restrictor is located right at the tip of the nipple of the steel coolant tube.

The restrictor allows more coolant to flow through the heater core because the beehive is basically Teed in there. If you study that part of the engne bay, it looks like the beehive is parallel to the heater core. Added as an afterthought.

Now the question that comes to my mind is if I'm not running a heater core, couldn't I get away without a restrictor?

Just for clarification, the heater core has an on/off valve in it. When you switch your logicon or whatever it's called in 1st gens to hot, the valve is opened and coolant flows through it. Switching it to cold closes this valve. This tells me that coolant flow through the heater core is not necessary for beehive operation. I'm not sure how many of you were unaware that the heater core can be turned off.

The abiove also tells me that the restriction to flow inside th ebeehive is not necessary in the sense that allowing coolant to flow from the rear plate, do a little work, then flow into the lower radiator fitting, and back into the engine.

Of course this seems a little counter productive. Wouldn't it be better to route the beehive into the upper radiator hose? If the beehive truely is an oil cooler and not an oil heater (peejay said that) wouldn't it make more sense to expel the heated coolant at the upper radiator hose so it can mix with the coolant heated by the rotor housings directly? This makes more sense to me, but I know Mazda did it a certain way for a reason.

The heater core acts like a mini radiator, but it doesn't always flow (like in the summer time when temps are higher). So why is the beehive hooked up in such a way as to be counterproductive? Because it's easier this way? Cheaper? Less hoses and connections to worry about? I guess Mazda figured the added heat would mix with the cooled coolant and be ok.

Who knows. Maybe a quick fix for the beehive cars is to reroute the output into the upper rad hose.

Wait a minute. I just thought of a good reason not to do this. The flow direction regarding pressure vs vacuum in the system may stagnate the coolant in the beehive. The water pump pulls a vacuum at the lower radiator hose, sucking coolant up against gravity and pushes it into the engine. It pushes through the upper hose.

Ok, the waterpump sucks on the lower radiator hose. It makes sense to connect the beehive to this. It's just unfortunate that it will end up sucking heated water. How can we get around this? Is it possible withjout a total redesign and/or adding a second radiator? At that point it's easier to use an air oil cooler.

Would it be possible to connect the upper beehive (output) tube to somewhere in the upper radiator hose? I bet this would work flawlessly while the thermostat is closed. If you think about it, the bypass only stops flow up and out of the thermostat. It shouldn't affect the circulation from the lower rad hose through the engine and out of the rear plate, and into a beehive in a traditional setup.

Then when the thermostat opens, the coolant flows into the radiator under whatever pressure the system is set up for. In this case around 13psi. Will this overwhelm the smaller diameter beehive line? Or if the beehive line is connected after the thermostat, will the flow restriction produced by the thermostat itself be enough to continue to bleed off enough cubic centimeters of heated coolant from the beehive to be effective?

One potential problem. I must add a 6mm hole through the thermostat so it always flows a little. This reduces thermal shock loading on the components. Appearantly the thermostat will start oscillating between open and close and can cause problems if I don't do this. Does this further complicate the issue? Maybe a little.

Here is something else to think about. Ken Durkee from Mazdas and More would always hook a loop line from the rear plate to the thermostat housing. He'd search far and wide for an aluminum one with a fitting. He doesn't do rotaries anymore and never asked him why he did that.

It's my guess it allows coolant to flow even while cold and the thermostat is closed, like I mentioned above. Is this a good thing? Maybe not. My MG Midget was build buy his shop in '88 with a '71-'73 twin dizzy 12A with a single dizzy front cover swap. It had this loop line and it would overheat on the previous owner quite regularly. Not enough to hurt the engine, but the temps would get uncomfortably high.

I got the car and stuck a '74+ 13B. I blocked the rear plate and didn't use a loop line. I also had a cheap 10" electric fan on the radiator. The PO also had an electric fan but think mine is a little better. Anyway without a hood on, it would sit and idle and not overheat. Even the oil was at a comfortably low temperature with an air oil cooler out in front of the rad.

The main differences no loop line, the engine is bigger, the porting is smaller at '74 spec (the 12A was streetported). Could the loop line have caused the problem with the 12A? Or was it the fan?

If I rememebr correctly, I ran the car with the hood on and it still didn't overheat. I can't remember now.

This post turned out a little longer than I wanted. Anyway I'm thinking I should say screw it and just hook up the beehive to the rear plate and the lower rad hose, as in a traditional setup. I'll figure out an easy way to add a restrictor and monitor the difference. What do you guys think?

Jeff20B

iTrader: (13)

Here's a question for you beehive guys. Is your coolant temperature generally higher than air oil cooler cars?

Perhaps the restrictor was added by Mazda engineers after the beehives were already manufactured as a way to keep the oil temps higher? Like maybe it was too effective? It's cheaper to add a restrictor to the cheap coolant tube.

This follows the same logic as the thermal pellet in 2nd gen and later eccentric shafts. The thermal pellet, as it's called, is a temperature controlled valve that prevents oil flow to the front rotor. The reason is for emissions, so stuff heats up faster. It's been said when it fails it takes out the front rotor bearing. Atkins and others sell a thermal pellet bypass plug which is always open and allows full time oil flow to the front rotor like all '85 and older shafts.

Seems to me Mazda wants oil temps higher for better emissions. We want them lower for more power and longevity.

My rotary sense is tingling. It's telling me to not use a restrictor. This should lower oil temps because it will effectively speed up the coolant flow. It won't screw up the flow because the heater core outflows the beehive whenever it's set to hot. Again the old thought process of "it needs to flow slow to pick up more heat" comes to mind. However in this case, since the hot side of the rad differs only a few degrees from the cool side, the evidence suggests that the restrictor is allowing the oil's heat load to build up rather than bleeding it off at a healthy rate. I'd say it heats up to maximum only half way through the silly thing.

So does the above logic make sense to anyone else? Hello? Is this thing on?

Rogue_Wulff

Jeff, I tested a beehive cooler and the oil/coolant lines with a temp probe once. The oil temp coming out of the front cover: 143F. Coolant temp coming from the rear iron: 180F. Coolant temp leaving the beehive: 173F. Oil filter temp: 173F.
My thoughts about the beehive, is it has the POTENTIAL to be more effective than the FMOC. The key here, is it needs cooler water flowing into it. Here's how I would do it.
You could tap a line coming out of the front water housing, on the cool (water pump) side, or even use the threaded hole on the front iron, route this to the inlet of the beehive. For a return hose, either run it into the top rad hose, or add a fitting directly to the top of the rad.
In the event that it actually provided too cool of oil temps, then start restricting the water flow.
I had planned to try this on my '83 12A, but I was given a complete FC FMOC, so I used it instead.

Jeff20B

iTrader: (13)

So it does act like an oil heater.

In order to get cooled pressurized coolant, you could tap the front of the waterpump. I'm not sure which side, I'd have to look at it. Use a large fitting like 1/2" NPT or something.

I just looked. There is not much room. The belts might get in the way. The pulley might be in the way. The aluminum waterpumps have a cast iron impeller section with ribs. The best place to tap would be where the alt normally sits. This means relocating the alt.

Again because the engine is watercooled, the temperature differential which exists between upper and lower rad hoses is really not that much. The reason the water gets up to 180° or so is because it has just been heated by the spark plug section of the rotor housings. I'm sure the bottom of the rotor housings also adds plenty of heat.

Ugh. Now it's looking like I'll have to mount the radiator in the back. The front of the car is too small. I could change things around, but if I can get away with it in the back, that means less work routing coolant pipes along the floor of the car and all the misc stuff that go along with it.

A tall '83-'85 radiator with a 16" electric fan on the core should be enough for idle and hopefully enough for low speeds. Higher speeds should provide enough air flow if the radiator is as far rearward as possible. I'll route the exhaust away from the radiator. It might work.