Dark side engineering: That infernal beehive
 

Anybody know if the 12A beehive is averse to ~100psi oil pressure?

I'm thinking that I don't like having the oil cooler out front, and I think I have a way to keep oil temps down while using the beehive.

it can handle it. I installed a stock rebuilt 83 12-A with beehive on my son's S3. I'm using an old school Powerhouse engineering 100 psi ROPR. Eqqus oil pressure gauge pegs above 100 psi when cold but i havent noticed any leak despite I used harbor freight special nitrile o-rings, yeah non-mazda.

I had an Auto Meter Ultra Lite Oil Pressure gauge in my car right above the beehive. When I ran 10w-40 in the car it would be above 90psi on cold MN mornings here - I think it can hold above that just fine.

I have only seen a couple beehive's that issues with oil mixing into the coolant, and they were severely corroded inside the coolant portion, from lack of cooling system maintainence.

I've always contended that had these been plumbed differently, they would have been more than enough to keep the oil temp in check, without causing coolant temp to increase.

The beehive is great. I use them on all my projects where an air oil cooler would be less ideal. Yes 100psi is fine. The steel hardline won't leak if you keep the front cover fitting aligned while you stretch it 20mm to fit a 13B. Also don't screw with the banjo bolt. It was installed at the factory and doesn't need to be removed to service the o-rings between the pedestal and the unit.

Let's see... I've tested beehives in the blue car, Percent's white car, the GLC, two rotary bajas, and there's probably some more. Never any oil leaks, no overheating of oil or cooalnt, fine oil pressure.

Oil temp and pressure can be monitored with an RB type II temp and pressure adaptor. RX7 1975-1985: Oil System: Oil Presssure /Temperature Sensor Adapter - They can also be used to feed oil to a turbo or supercharger. I threw one in the GLC for the Camden and I've got another one sitting here waiting to go in my baja once the S5 turbo is available. Just earlier this year I also installed one in a friend's baja who's doing a turbo setup a well.

The beehive gets a bad rap around here but I think that's beginning to change.

i don't mind them, they do keep the oil at a more optimum temp more of the time.

i think the bad rap is because the beehive puts all the cooling into the radiator, which is plugged because its 32 years old and the coolant hasn't been changed since 1987

My personal belief, is they get the bad rap from dumping the heat from oil, into the inlet of the engine's coolant. This, after taking the water to cool the oil, from the same place that is used to feed hot water into the heater.
Heated water into the beehive, add more heat from the oil, then dump the even more heated water into the water pump inlet for yet another pass thru the engine........

A thermostatically controlled cool water inlet, and return to the radiator, would be a MUCH more effective method. This could keep oil temps in the near-optimal range under almost ANY condition. It would also keep the heat from the oil going right back into the engine, thus increasing the cooling system effectiveness.

My plan is to replace that hardline with -10. I've certainly got enough of the stuff kicking around.

The rest of the plan involves a small radiator and a coolant after-run pump. Beehive gets its own cooling system.

I had been planning previously on rerouting the coolant from the water pump's outlet instead of the hottest point of the engine, but this way makes even more sense. The hard part will be keeping the oil hot under cruise while still keeping it cool when rallycrossing when it's triple digits outside.

I like the classic look of the beehive and I've never had a problem with one, although I generally have a newer aftermarket radiator installed along with it.

I also suspect the Mazda engineers were pleased with their overall performance or they wouldn't have installed them in the first place.

The argument that beehives were a cheap cost saver over the FMOC doesn't make sense.

Why would Mazda risk wide spread and expensive failure of a system so critical to rotary engines to save a couple bucks?

in theory i agree, however the Germans love to do this kind of thing, and it always ends up being complicated expensive and broken.

Agreed (to an extent ;) ) Manufacturers, contrary to many "know-it-all" tuners, know what they are doin. THEY designed the systems and THEY tested alternatives; using labs, machinery, highly accurate sensors, and very smart people, all of which cost millions of dollars, and THEY determined what was the best for the system THEY made. Not to mention, most manufacturers overbuild and under tune the vehicles for reliability factor. Mazda picked the beehive because it was a viable choice for the increasingly emission restricted (and stock) 12A's. I wouldnt be surprised if accelerated engine warm-up to reduce overall emissions was a contributing factor for the choice, being that the heat generated from the oil system could also contribute to the warming of the coolant....That being said, Mazda also only deemed it appropriate for last generation 12A's, and decided that it wasnt sufficient for any of the fuel injected 13B's. But, there is a reason for everything, whether or not we know why ;)



When I read this, I started thinking of high end water to Air intercoolers or some supercharger "heat exchangers" . Running a separate dedicated pump, lines and radiator...could potentially be a very effective system

Why when beehive oil cooler gets mentioned first thing that pops into my mind is leaky dowel pin...? Next is missing chrome on housings...??

Jeff, you can find the same pedestal on ebay for $23 shipped non racingbeat of course. They work fine.

It saved weight and made the car easier to assemble. It also brought the oil up to temp faster and reduced complexity.

So what if the engine's oil O-rings were granola after 80,000mi? It's long out of warranty by that point.

The missing chrome has nothing to do with the beehives, it's generally due to the 3mm apex seals. I've pulled plenty an air-oil cooler engine apart that had more missing chrome than chrome. One was worn through the sheetmetal in spots!

Both valid points.
Getting the oil up to temp quicker likely reduced emissions, particularly in cooler climates with a lot of city driving.
No reason to worry about an engine lasting forever, that kinda defeats the idea of selling *new* cars.......

Well now I have to object to the conclusion that Mazda was deliberately designing rotary engines to fail.

As any student of rotary history knows, the Wankel engine went through a severe bottleneck in the 1970's that nearly tanked the Wankel for good. Anybody remember the days when Mazda rotary drivers would raise the number of fingers corresponding to their rebuilds when they passed another Mazda driver on the road?

Back then it was the carbon apex seals and they fixed that problem. Do you seriously think that in 1980, when they moved on to the FB, they wanted a repeat of the finger fiasco because of a poorly designed oil cooler?

And if that logic isn't good enough for you, try this. I've driven 4 different FBs over the last 10 years for my long daily commute into Atlanta. Every one one of those FBs came new to me with an original 12A fitted with a beehive oil cooler and well over 100,000 miles, to which I proceeded to add another 50,000 to 80,000 miles. Only one of those 12As failed, and it was because of an apex seal, not a leaking O ring, at 179,000 miles. I doubt there are any boingers from the era that could make that claim.

In fact, the beehive cooled Mazda 12A is one of the most reliable internal combustion engines produced in the 1980's, including those Wankels cooled by the FMOC.

If you abuse or modify your 12A, you might run into problems, but don't blame it on the beehive.

Hey now, the only person who jumped to that conclusion was you.

Every engineering exercise has pros and cons that need to be weighed against each other. A potential reduction in life is often an acceptable and necessary engineering trade-off. The cars aren't designed to last 30 years and 30,000,000 miles are they? They COULD be but then nobody could afford them. Does that mean that a car that only lasts 200,000mi was engineered to fail so they could make more profit?

FWIW, my first beehive car had 211k on the original engine and didn't have the dowel leak.

we actually have the lighter and easier to assemble bit in writing, somewhere. the beehive has a few trade offs, but engine life doesn't seem to be much shorter (or longer).

i've owned more 84-85's than any other year, but i've had dowel pin leakers of other years, and i've seen GSL-SE's do it too, so its not uniquely a 12A problem.

there is some bulletin about the Reman engines, and Mazda blames the 12A engine failures on clogged radiators, and just about every 1st gen i've had has had one of those!

It's good to see the beehive getting a little love.

Can we work on fan clutches next?

fan clutches? i've never seen a bad one?

Me neither. I don't see why they get such bad press.

I've seen three bad fan clutches. All three were really stiff and would wear the belt(s) out prematurey. One even leaked before I threw it away. But I've also had some good ones. They only needed one belt and never squealed. Cooled just fine.

I think I figured out what's up with the beehive. A poster above said something that triggered my rotary sense. Basically Mazda used the beehive for emissions so the engines would warm up faster. Notice they only used them on the last run of carbed engines. Also notice the EFI 13B didn't get one because it didn't require one as the EFI was ultimately cleaner than carbs. Makes sense to me.

Beehive = emissions device.

i've seen 3 bad fan clutches too! all three had the stamp of certain failure, the BMW roundel.

yes. that emissions twist on things does sort of make sense when you think about it, doesn't it?

i've never had any issues with any of my beehive 12A engines. as a matter of fact when my air oil cooler cracked years ago, i ended up putting the beehive on my 13B for a few weeks while i waited for a new one to get to me. however, i simply just like the front mounts better.
:lol: bloody hilarious!

I think of the fan clutch as more than just the viscoelastic unit that activates the cooling fan.

The fan clutch is really a design element that features elegant and simple construction, a cowling optimized for air flow in the FB engine compartment and free wheeling performance except when occasionally needed to moderate temps. No electrical connections, thermisters, switches or motors to go bad, or drain on the battery or charging system.

In this sense, the fan clutch never really goes bad, you just need to replace the viscoelastic unit every once in awhile.

Having said that, I was just kidding with the fan clutch comment and apologize for hijacking what up to then was an interesting and informative discussion on the hallowed but often maligned beehive.