Hey guys. Its been a really long time since i have posted. But im back in the Rotary game! Im looking for some info from experienced engine builders and tuners. A back ground in Racing with rotarys would be even better.

Lets try to keep this thread clean, and without a bunch of garbage or BS. First hand experience please. If you do not understand what is about to be talked about, please keep the negative and un educated banter to yourself. Im hoping some gurus can step in and share there experience with me. If you know who the gurus are, please point me in the right direction, or tag them in this. Thanks in advance!

Okay. I want to know what the highest, CONTROLLED, coolant temps you have seen ran on a 13b. Controlled and Stabilized is the Key word here.

Im hoping to run my coolant temps at 240 to start, with hopes of going up to 260 deg in the long run. I need to know if the OEM coolant seals can take that kind of temperature and run them at a constant state.
please do not confuse Over heating, and running a stabilized high operating temp.

Ill be running higher than OEM block pressure, coolant jacket mods, Craig davies pump, 2L dedicated Swirl pot, multiple air bleeds that will go to a Big Header tank and a System pressure over 25 lbs. (not to be confused with block pressure)

Can the OEM seals deal with these kind of temps and pressures?

Thanks guys. looking forward to your input.

 

The third gen section recently had a thread on this very subject. You may wish to start with a bit of research..

​​​​​​​That being said, I believe the primary problem comes NOT in whether the seals can handle it or not, but in whether the engine will warp or not. That, if I remember correctly, comes as a result of differing expansion/contraction rated between the irons and the housings on cool down as well as max heat.

 

I've got to ask, why are you targeting such a high engine temp?

 

Yeah I'm wondering too.... I feel like at those levels if anything goes wrong you have no head room before something major goes wrong. Educate us on why high stabilized temps would be a good thing?

 

I would focus more on chasing maximum acceptable EGTs as to get the most out of your turbo setup, not the maximum engine temperatures themselves...

 

Also curious with the desire to run such a high temp and coolant system pressure. Better MPG? With temps in that range it seem like a high tech coolant with virtually no pressure would be the way to go. Evans waterless coolant would handle this with no problem and you could simplify your coolant system in comparison to what you listed.

 

the rotary has been proven time and time again to make optimum power at a temperature that is low by piston engine standards.

you have to remember that if you're equating the rotary to a piston engine, its like a flathead with iron pistons and siamese ports, the basics are there, but lots of quirks too.

the iron rotor, behaves much differently than an aluminum one, and its temps must be kept under control.

you would see a small increase in part throttle efficiency by raising coolant temps at idle/part throttle, although 260 is beyond what we'd consider bad.

it has been my experience that piston engines don't want to be 260f either, they will usually survive a trip there, once

 

EWC is such a joke, I hope you're kidding.

Regardless if the coolant boils or not, the metal expansion and more importantly rubber/viton seals within the engine cannot sustain those temperatures.

Why would I never run more than 1.1 Bar coolant pressure on a rotary? Hmm, that's simple, the damn rubber/viton water jacket seals can't handle the pressure.

What should run HOT for efficiency is a turbocharger in which metal expansion closes down tolerances on the turbine wheel and more efficient pumping is the result. That's why you run a turbo blanket...as well as saving the engine bay paint and vital components around the turbo.

 

I've done some work on fluid temperatures vs engine performance, on modern piston engines.

As an FYI, general engine principles tell you this from a performance perspective: Higher fluid temperatures = less torque/energy loss due to friction, but higher knock tendency, assuming a fixed charge air temperature. So when you have hotter coolant moving through the water jackets and hotter oil coming from the oil cooling jets, you're more likely to knock. And that usually outweighs a frictional benefit, unless you have a highly knock resistant situation (E85 for example).

A lot of newer piston engines have variable water pumps and thermostats that run hotter temperatures during cruising for better fuel economy (due to the friction effect) and cooler temperatures at high load (due to the cooling/knock resistance effect allowing more advanced spark).

If this is for a racing application and you are just trying to get the engine to survive running hot, I would try to exhaust all avenues of expanding cooling capacity first. Improve the radiator, oil cooling, and airflow to those before you try to beef up the engine's ability to withstand high temperatures.

 

The water jackets will be seeing far in excess of radiator cap pressure with the engine running. I haven't put a gauge on a rotary yet but 50-100psi is common in piston engines. This is what keeps the coolant from boiling at the exhaust ports and around the spark plugs.

That said, coolant temps this high will crush the rotor housings unless you use thinner/weaker tension bolts to allow the engine to expand more with temperature. Or reinvent the coolant seals to be able to hold combustion pressure with very little tension on the bolts until the engine is up to temp. Or have a complicated starting procedure like Cosworth DFVs had where you drained the coolant, heated it to near boiling, then poured it back in, before you attempt to start the engine...

I like the idea of high coolant temps for efficiency reasons but there are some realities about the way rotaries are put together that make those temperatures impractical.

 

You have it backwards. You need to understand thermal dynamics a little better. Energy always travels from highest to lowest. (this includes heat)

air temp: 30 deg, coolant: 190. The 190 wants to come down to 30.
air temp:30 deg, coolant 240. The 240 wants tot come down to 30.

Guess which one transfers more heat in the same system. the 240 will transfer dramatically more energy for a giving time in the radiator. In a well build system, this actually creates more head room and a more stable system as it is constantly transferring more energy.

 

you didnt actually bring that garbage into this conversation did you?

That stuff is ******* garbage.

 

Rotors are thermally controlled through the oiling system. 2 different subjects. 2 different systems. Thats a completely different conversation. I have that one under control already.

 

uhhhhh.... Block pressure exceeds well over 45 psi... stock. the cooling system works best when the block pressure and radiator pressure are as close as possible.

 

Thank you. this is the kind of Conversation i would like to see here. The tension bolts are one of my concerns. I have used pre heaters on a couple race cars, but would hate to have to do it for this build. They are used more to bring the internal tolerances into operating spec before use, as the engines run on the big side of tolerance. Im hoping i can find a happy medium without to much loss below operating temps.

Lets try to keep it somewhat clean. I know to some of you this sounds ridiculous, but try to keep the non informal replies to a minimum.

like the turbo talk. wtf did that come from? haha. For this conversation, lets consider all other systems are running optimal.

So how hot have people continually ran a 13b... Yes, im trying to raise the efficiency of my motor, but i dont want to get to consumed on that topic. I would like to find some hard data on what the hardware can handle. then i can really explore the theories of efficiency and what will work.

thanks guys.

 

I have also searched. How often does search actually work. haha. i usually get pages of non related ****.

if you know where that thread is lurking, please share.

 

I used to see coolant temps of about 220 at the end of a run before I beefed up my cooling system, almost 230 on bad days.

Engine is FAR happier with coolant under 200! And this is with a non turbo engine.

It really would be nice to run higher coolant temps. NASCAR run in the 240-245F range, WRC don't worry until 260+. Be very nice to have a higher temp delta across the radiator for a number of reasons. As j9fd3s pointed out, though, engine performance really suffers when things get that hot.

One of the things I wanted to try was a two stage cooling system, take coolant off at the heater pipe on the rear end housing and route that to an aux radiator. The effect should be more coolant flow through the all-important bottom half of the engine. The result should result in a more thermally stable engine that could withstand higher overall coolant temps. The really hot coolant gets to a separate radiator and the top end of the engine stays relatively cool rather than getting heated up so much by the hot spark-plug coolant.

 

from the other thread.

it would appear that Mazda has done what every piston engine has also done, and revised the coolant flow so that the engine is more evenly heated. i would imagine this lets them run the new engine, either at the same temp with better efficiency, or more probably at higher temps without problems.

 

Measure it with real world data. You're not really contesting me, but rather the OEMs on this one...

45psi Absolute Pressure is 2.1 Bar Gage, so are you suggesting we run a 2.1 Bar Cap on our radiator systems because that would not make them as close as possible, they'd be identical.

If that's the case, why doesn't every manufacturer do that? What conclusions are they coming to that dictate 0.9 Bar, 1.1 Bar, or 1.3 Bar across the range of these motors?

Another question to ask yourself: Since these engines are revving and spinning pumps which have a certain efficiency and range before cavitation, does the block pressure alter during operation? And if so, how much?

 

I want a real world solution to cavitation at higher altitudes. I drive mountain roads HARD in my Integra and plan to build this FB Rx7 for harsher conditions. The altitude has two main effects. Lowered boiling point of coolant system and more importantly, lower heat transfer rate due to density of air traveling through the heat exchanger.

 

Do not confuse block pressure with radiator pressure. They are different.

Or, at least, they are different if you have a thermostat or plug the bypass and install a restrictor ring in the thermostat housing.

 

These are the recommendations from the Mazda competition preparation manual, dated 1980, Note that this is for a non-turbo 12A motor in a racing environment:

Warm the engine up at an idle speed of 2000-2500 RPM, until the oil temp reaches 160F (70C).
Recommended coolant temperature (outlet side): 160-195F (70-90C).
Max coolant temperature: 205F (95C).
Recommended oil temperature (oil pan): 195-230F (90-110C).
Max oil temperature: 250F (120C).

I think you are pushing the limit.
Which cooling jacket mods are you using?
Barry

 

I wasn't confused at all. He said that these two pressures (block pressure and radiator pressure) should be as close as possible.

 

I've read that rotor housing have a certain deformation under heat that has to be accommodated for when designing Apex seals.

Wouldn't higher temperatures make this worse?

 

I dont understand what you are trying to argue with me. lol. Unless you just like to argue ****.

where did i suggest a 45 psi rad cap? Ill be running at least a 22 psi cap on my systems. Its a part of fluid dynamics, system pressure differentials work best the closer they are. I didnt say put a 45 psi cap on a shitty old RX cooling system.

As for manufactures, actually, they are currently doing it. lol. Maybe you need to spend some more time around current technologies, not some old Rotary **** that was designed in the 80's. Many, many current engines have pressures above 20 psi, and have moved away form the standard rad cap. They run proper header tanks, and some are actually sealed systems. lol. there pressure is linear, but infinite.

Now for your real "real world" cavitation problem... This topic is a real world solution. haha. The Higher the system pressure, the less cavitaion there will be. The HIGHER system pressure also combats LOWERED boiling points that are caused by lower atmospheric pressures found in higher altitudes.

Im not making this **** up as i go. Many engineers and Race teams use these methods.