why does coolant make a double pass
 

Ok, I am just throwing this out guys, but wondering why the engine coolant passages/system are designed to flow the way they are?
The coolant enters and exits at the front of the engine---right? Why?
Couldn't the renesis have the coolant exit in the rear of the engine?
That would eliminate the return flow of hot coolant through the engine, help with the rear rotor running hotter than the front, open more passageways for cool coolant and I think allow for better all over cooling?
To visualize--a lot of people (and myself for a period of time) have temp gauges hooked up to the RB adapter that uses the heater hose. The sensor is monitoring the temps of the coolant in that hose. That heater hose is supplied by a pipe that exits the rear of the engine on the drivers side. The temps of that coolant that is supplied by the rear of the engine is what is seen. Its pretty hot--right?
Ok, then the coolant has to turn and make its way back to the radiator. Why? Its already hot? Why circulate it back to the front of the engine? Why not let it exit to the radiator from that point?
Anyone?
Team---yes I have searched everywhere:)
OD

Does anyone have a diagram of the Renesis coolant flow path? Maybe a visualization would help to see why they did this.

Here is my guess:

"cold" water enters at the front and picks up heat as it travels through the engine. so the water at the front of the engine is removing more heat that at the back. By passing back through, the coolant is actually redistributing some of the heat back to the front of the engine thus making the temp more equal front to back. if it exited from the back, the front housing would be running even cooler than the back housing.

I may be wrong though...

Or it could just be that that was the easiest way to do it . Also you should look at where the cooler water passes over - It would make sense to pass over the intake/compression part of the housings first - yes ?

My educated guess would be for spacing reasons... The radiator of a car is just like a heat exchanger, of which i've seen two styles; one style has cooling fluid running from one end to the other of the exchanger, and the other style has a U shape (and yes, the outlet temp is much warmer than the inlet temp). Perhaps the design of the engine or complexity of routing the coolant channels in the engine may have had something to do with it? I'll try to see if i can find something on it. Although 'hot' coolant may be passing by the engine again, it is still removing heat from the engine, to a lesser degree of course, as opposed to 'cool' coolant.

I think you would be surprised to find that the temp of the water heading in isn't too much cooler then the temp heading out.

I found this @ wikipedia:

Unlike a piston engine, where the cylinder is cooled by the incoming charge after being heated by combustion, Wankel rotor housings are constantly heated on one side and cooled on the other, leading to high local temperatures and unequal thermal expansion. While this places high demands on the materials used, the simplicity of the Wankel makes it easier to use alternative materials like exotic alloys and ceramics. With water cooling in a radial or axial flow direction, with the hot water from the hot bow heating the cold bow, the thermal expansion remains tolerable.

Still doesnt explain why though.

space is one thing

but most important thing is that it travels thru hot areas first --- then back to "not so hot areas, to make the temperature more "even" across the whole engine.

I think in/out at the same end is a tradition from conventional front longitudinal engine layout. The water pump is at the front because the fan is on it and the radiator is in the front. Return is in the front because it's a shorter path. Return from the back would need longer hoses.

I think you're on to something. One thing that killed straight 8s (remember those?) is that the rear cylinders never got enough cooling. Do rear rotors in RX's have a cooling problem?

With modern transverse engines, coolant return could be from the opposite end, without the plumbing being any longer.

Ken

The rear rotor is known to run hotter than the front.
I do now some v/8 guys that do reverse cooling.
I remember the old Packard straight 8's ---damn what an engine!
What got me thinking about this was since temps are critical to our engines in what way can the engine be better cooled. Yes, I started the secondary radiator thing for our car and that works very well to keep the overall temps in check, but since the water temp is only checked at one spot, what is happening elsewhere?
Yes I know builders waffle coolant channels, use different coolants to help with localized hot spots, increase coolant pressure/velocity etc etc in dealing with heat issues, but in thinking out of the box, this idea came to mind.
There are two coolant lines that exit the rear of the engine, one for the heater and the other is the Throttle body line. The temps of the coolant that come out of the engine are equal to (within 10 degrees) of the coolant that is in the hose going to the radiator.
This to me means that the coolant that comes back to the front of the engine is not cooling anything very much.

ok in further thinking, its my understanding that the "weak" spots in our engine is the corner of the apex seal and the side seal spring. These are the weak spots again from what I understand, because of the heat from the side exhaust port that these areas have to deal with.
Now if that is a critical area then why doesnt the engine have cooler coolant flowing through those spots? If I am not wrong that area is one in which the returning coolant is used?
Two "Hot" areas in this engine
1- combustion side
2- exhaust port.
Combustion side uses coolant from the radiator
exhaust side uses coolant that has already passed through other hot areas?
Poor design? Can we change that?
OD

Mazda has been using this "design"(flow path) for the past 40+ years. spark plug is the hottest spot on the engine. coolest of course is the intake area.

most of the heat will be carried away via exhaust gas this is why the exhaust side don't need as much cooling as the spark plug side.

there is nothing much we can do to change the coolant flow path.

disagree that the exhaust ports are cooled enough. The coolant flow has been in use for all those years BUT this is the 1st side port exhaust engine. Before, the exhaust ports were not as heat soaked as they are now. We also have higher EGT's than the previous models.
All in all, it a spot that could be improved. I think?
OD

Back to basics for a moment. While the rate of heat transfer for radiative cooling goes as the fourth power of the temperature difference, that rate only varies directly with temperture difference in the case of contact cooling (Fourier's Equation). At the junction of the hot metal to the coolant, the temperature difference isn't that much when one considers that such things are measured relative to abosolute zero. In steady-state motoring, say the metal on the cooling passage surface is at 250F and water at 200F. In degrees Kelvin this is 394 K vs 366 K, or a difference of 7.2%. 180F water would give 255 K or 9.9%. 180F water cools about 30% more efficiently than 200F water in this example.

However, if one looks at the passage of water through the engine from the standpoint of design, the total heat transfer in different areas of the engine can be adjusted by adjusting the flow made available to different passageways as well as the area of surfaces in contact with the water. The loss in cooling efficiency of the water as its temperature rises, can be compensated for by manipulating the contact area, flow and flow velocity. If one knows in advance what the desired steady-state temperture gradient is, one can achieve the desired cooling.

However, it seem to me, again from Fourier's Equation, one can play another game. The rate of heat transfer for the example above with a 250F surface and 180F water is exactly the same as for a 270F surface and 200F water! The rate varies only with the temperature difference. In that way, it makes some sense to cool the colder surfaces with cool water, and hotter surfaces with hot water.

If one looks at a side view of a rotor housing, it's pretty clear the engineers were playing extensively with cooling passages to get the desired effects. (see attached). It's reasonable to assume they also included the effects of temperature rise as the coolant passes through the engine in their goal of achieving the right thermal balances. Because of the azimuthal variations around the housing in a rotary, this must have been both vastly more difficult to do than with a chevy V-8, and particularly so in light of the computational power available at the time (about zero).

Very interesting question OD! After an hour's thought while eating my can of beans for lunch, my comments would be:
1) Since the design of the 13b predated modern computers, it's likely there's room for considerable improvement.
2) Without a thorough analysis way beyond a amateur's means, I'd be extremely reluctant to make cooling mods internal to the 13b short block.

you have a reason to believe they didnt do any design computations using "modern" computers for the coolant flow through the Renesis? this was in 2000-2003 remember.

Hell there are/were videos and pictures around showing the process of designing just the proper angle and placement for the rear door inner handle. They made that little japanese woman open the rear door THOUSANDS of times and used computer modeling for various other size and shape people so the door would open not to hard and not to easy ( too easy can actually flip you out of the car!) but JUST RIGHT.

Sorry, I wasn't clear on that. While the Renny is from 2000, the 13b is from 1980ish and before. They weren't starting from a clean sheet of paper in 2000 and may have inherited things from the original design that weren't updatable: only speculation on my part, though supported by some conventional wisdom that the rear rotor gets too hot. It doesn't change my basic take on the matter which is blind modding of the internal cooling system is probably a bad idea. YMMV.

meh no worries HiFLite. I feel like i over reacted to your post

We need to find out where to drill and tap coolant passages on the rear end plate!

What about the heater hose on the drivers side rear, is that an "in" or an "out"?

It might be interesting to put temp sensors all over the block and then add (or subtract?) flow to the rear heater/block hose connector.

You can't really cool them any more. They are way too hot to be given more direct access to the coolant. Their heat is allowed to precess through the motor to the adjoining coolant jackets.

But NOT because of coolant flow.

I never knew these engines had water cooling problems. In race trim and operation our weak link is side seal spring life. Everything else is peachy.

Good! While you're here, have you ever experienced water hoses collapsing at high rpm?

ok theres a diagram showing how the water is flown.
I think they tried to is to keep the intake and compress area as cold as possible, the expansion and exhaust area as hot as possible.
cold intake and compress area reduces pinging, hot expansion and exhaust area reduced thermal leak.
its the same with piston engines too. cold water always goes in from the bottom, and hot going out from the top in order to reduce pinging and thermal leak.
http://www.lucubration.com/cozy13bt/...olant_flow.jpg

Guys I understand yall are putting a lot of emphasis on water flow and direction, but also remember that different metals are better at dispersing heat than others. Take aluminum for instance. It is a great conductor of heat, copper is a little better, but well I don't see us with copper engines anytime soon. Don't forget how well the block is at spreading that heat out. Also you can affect cooling by using better coolants than say prestone 50/50. The use of Water Wetter with less anti freeze allows for better flow of the coolant. Having the coolant set at the right temp so its not to thick, and allowing for better air flow. I installed a vented carbon fiber hood, and there has been a noticable drop in engine temp. They make other things like brake cooling units, and transmission cooling units. Cooling the transmission would help by pulling some of that heat away from the block, and not allowing the transmission to assist in the heating.

One of the biggest things that can be done though, and that I am currently looking into is a radiator sprayer. Every time I went to the track with my dad, and we were pushing cars extremely hard over long ours we carried sprayers with ice water in them. We would spray the engines and radiators and you could watch the temp drop on the gauges. Then one day we installed an intercooler sprayer with a nos bottle and just ever so lightly gave the radiator a spray once in a while, and it helped incredibly with cooling.

And this is one of the fundamental problems with this motor - it is a sandwich of dissimilar metals, each with their own thermal properties. When things get really hot, bad stuff happens.

Uh, no. That is just nonsense.

How are you quantifying that?

How, exactly, would you install a transmission cooler on a 6-speed?

Horrible, horrible idea.
First of all, if I were the track marshal, I'd punt you for polluting the track with water.
More importantly, spearing cold water on a hot radiator is just begging for massive thermal fatigue.

I can see where having two different metals bolted up causes a problem with heating and cooling. They would expand and contract at different rates.

On the second note I meant better collant flow not air. Bad habit to be typing and charting at the same time at work.

I can quantify the cooler temps on the engine pretty easily by watching the temp gauge.

I understand there isn't as much of a need on cooling a manual transmission than an automatic. Ive seen plenty of Baja Trucks when I was stationed in SoCal that have a cooling system in place on the manual transmission so I know it can be done on ours too.

Intercooler sprayers are not new, and I have never had a track marshal complain, or anyone else for that matter. Usually your not spraying ice water on the track, while your moving. Thats what the nos tank with intercooler sprayer is for. It works really well though, and again never had a problem with a radiator, intercooler, or the inspectors with a spray system.

Either way, it is wrong.
Changing the ratio has nothing to do with "thickness" or flow.

Then do it. You will be surprised by the actual correlation.

Pretty much none whatsoever until you are above the 1000 HP range.

Entirely different scenario.


Spraying and intercooler is NOT the same thing as spraying a radiator.

Do you proof-read anything you write before you hit "submit"?

Strange you say that about the transmissions. I have monitured the transmission temps on my car...and I am way over what I would consider OK after about 1 hour on the track in the summer. I would imagine that those of you in Phoenix and Vegas would find the heat too much a lot faster than that.

Had a nice Voodoo metal knob that I couldn't hold with my bare hands...and barely with my Nomex driving gloves

Interesting.
My tranny case is usually right about the same as my engine temp.
That said, the tranny doesn't really care that much about how hot it is until it starts seeing something north of the 300° mark.

No of course not, anti freeze is much thicker than water. So reducing the amount of anti freeze in the system wont help you at all. It makes no sense what so ever. Anti freeze also doesn't have the same amount of heat transfer properties that distilled water does. The more distilled water you can get in the system, and the less anti freeze you run. The more fluidity it has, and the more heat trasnfer capability it has.

I actually have a carbon fiber hood on my car, thats how I know. Its been on the car for a couple months now, and the engine has been staying a little cooler under normal operation. My next step will be to add a sprayer and then to do the fan install on the oil coolers. It gets hot here, When I get home I will post the photo where I had an in car temp gauge reading 130 on the highway. Anything I can do to lower car temps I will do.

As for the Transmission cooler. My buddy Jay had to install one on his Corvette, and its running at about 750whp. His situation was also a must do, not just something he wanted to do. If the rear rotor on our car is serving as a problem, then cooling the transmission surely wont do anything but help, with the exception of in the winter.

Now Im not sure exactly how much of my post you read, spraying and the intercooler are the same thing when its the system I am talking about. I am talking about the intercooler/radiator systems that spray nos to help with cooling. <-- we are on the same page about this right? To clarify I have never used NOS in the throttle body or inside the intake. Only as a cooling tool.

This is completely wrong on several levels, but it has already been discussed in several places.

Also discussed to death and the data about how air moves through the engine bay demonstrates how coincidence is a deceptive indicator.

Those systems are NOT designed to be sprayed on the rad, just the intercooler.
The temperature differentials and the thermal loading are completely different in those two systems.
I've watched more than one radiator virtually explode when hit with tap water after a hard track run.

These numbers speak for themselves to me. Water is second only to Mercury when it comes to the ability to transfer and move heat.
Thermal Conductivity of AntiFreeze = .14
Thermal conductivity of water = .67

On a second note the viscosity of distilled water around 70 deg is 1.0 where as for Antifreeze at the same temp its 17.8. So nearly 18 times thicker than water. Heres the chart if you want to read it: http://www.engineeringtoolbox.com/ki...ity-d_397.html


So coincidence or not my car is running cooler after the install. That was the only mod that was done on the vehicle that month as well. Obviously the temps on the car now would be obsolete being that it was in the 85 deg range for a month and a half, and now its in the 40 deg range. I understand that much, but I am talking about the drop in temps I saw when the hood was first installed.

Never had a problem with a spray system. I had one installed on the 427 before I bought the super charger for it. Ran it for about 8 months then just moved it to the intercooler. The system never had any problems, and the radiator never exploded. I drove that vehicle in both SoCal and Arizona. Had to use the system numerous times to prevent engine damage. So from my experience I have never seen that kind of problem with this system.

Thermal conductivity is only a small part of the overall equation.
Thermal inertia (effusivity) and flow rate are more important.
Also, viscosity (or, what you really mean - fluidity) ratings (in mPa·s) are not linear in their relationship to flow, not to mention that 17.8 mPa·s at 70° is roughly the viscosity of honey.
I'm pretty sure you've seen antifreeze. It is nowhere near the viscosity of honey.
Pure ethylene glycol is about 16. Mercury is 1.5. Do you believe ethylene glycol flows more slowly than mercury?

Yes antifreeze does flow a lot slower than mercury. Just because its heavy doesn't mean its not fluid. Put them both on a piece of paper and see which one flows faster. Anti freeze is thick. Mercury switches are very sensitive. Pure antifreeze is thick, what most people touch is 50/50 which cuts it in half. Making the viscosity a bit under 9.

The important part is heat transfer. The whole purpose of the system. Anti Freeze doesn't transfer heat well at all. .14 vs .67? your talking about a huge difference. The fact that water transfer heat so well, means it can absorb more heat in less time as well, and move that heat to the radiator.

Mercury Viscosity is .118, just slightly higher than water.

I think there might be a date with an IR thermometer and a concentration meter in your near future...

Well I've got a couple of guesses and their exactly that---guesses.

Alec, what is:

1. The need to circulate a coolant through the entire motor to maintain a constant temperature in all areas to dissapate heat / avoid hot spots.

2. Engine bay packaging (the radiator is almost always in the front and why take the long path over the river and through the woods to grandmothers house. An extra long hose weaving through the engine bay would add more design constraints to the other required automotive systems (steering, brakes, emissions, suspension, A/C, other). Thinking about V-8 motors of the past, typically there is nothing else in front of belts and/or behind the radiators (and there shouldn't be) so therefore that spot is pretty open. Seems plausible, yes?

3. Probably some obvious reason that I/we have yet to learn.

My gut says this is not rotary specific. Thinking back on the oldest auto engines I can think of, in and out coolant hoses always appear to be entering/exiting very near the radiator.

My gut also says that somebody on this thread is going to seek out and find info on this and share with all. I left a post it note on Henry Ford's headstone yesterday. If his ghost gives my Ouji board the answer, I'll let you guys know.

Both of them?

We ran a tranny cooler with -10 lines to the rear of the car to a small oil cool rad with a fan blowing air through it. Still ran 250F when she was hot. Interestingly enough, the temps didn't dramatically decrease without the cooler. The old SpeedSource RX-8 Grand-Am ST cars never ran one of these. We did it in hopes of making the 04-08 trans 3/4 syncho and shift fork last longer-----negatory. Keep in mind this was with headers/exhaust running right along side the tranny case too (which I would assume would have soooome heat transfer) Maybe. Perhaps?

All the other RX-8 Grand-Am racers/SpeedSource car owners never ran or tried a trans cooler. Like us, they just carried a crap load of spare tranny's with them.

The big boys will REM or WPC (or some other type of microfinishing treatment) their gears and this does lower temps. We may have experimented with this in the older transmissions and found reduced temps and higher power on the chassis dyno. :) But it didn't cure the 3/4 design problem.

Side note: The 09-10+ tranny is near freakin' bulletproof. We have 4 of them now and they are rock solid. They weak link is the input shaft which is about 1/2 the diameter of the 04-08. But you can shift that sucker as fast as you can and she works great! 30 hours of everything I could throw at it (trying to break it on purpose to finds it's weak link) and the synchros were barely worn. This thing is awesome compared to those old POS that we would rebuild every 5 hours or so with damn near all new parts.

The reason I know the change in antifreeze works is because of what we would do on vehicles when I worked for GM. Guys would move from up north where they were selling cars that had two row radiators. The cars sold here were 4 row radiators. Same vehicle its just where the car was thought to spend its life. They would move down here and have over heating problems. Well we couldn't always convince them to change to the radiators that would come stock on the cars from here. So we would change out the anti freeze ratio. We would do a custom mix to 0deg F which its never hit here in Dallas. This always solved the over heating problem they were having. Up north they are using 60/40 where as we can get away with 25/75 here. 25/75 protects you to zero deg, then you can add water wetter on top of it to improve heat transfer.

like I said in 9k's thread ... you guys are thinking too much about the heat issue ...

Now my reasoning for this thought is to help protect the apex corner and the side seals.

To continue with the same coolant path yet have a major change in the position of the exhaust ports which exposes critical parts of the engine to higher temps than ever before is basis for some thought especially after the number of early engine failures this design has seen?
In 1995 Mazda did some research of a side port design and of course in 2004 they did this again. Thats knew that the side seal was in trouble and they came up with the new design that supposes to eliminate carbon from getting under it. They also designed the omp injector so it would weep as close to that area as possible in efforts to lubricate and COOL it.
That was a failure as we all know.
They also increased clearances in the side seal/corner due to the heat factors. Thatwas a failure also.
They probably could not redesign the coolant passages due to expense. The entire package would have to be redone?

Now coolant temps at the heater hose site (drivers side by the knock sensor) is only about 10 degrees cooler that it is at the radiator feed hose. I have monitored both. This means the returning coolant IMHO is not picking up a lot of heat?
There are 2 exits for coolant in the rear of the engine
heater hose supply --drivers side
one for the throttle body--passengers side--its very small

Water versus antifreeze--lets not go there. For those interested read some of Evans coolant theory papers.

A redesign again imho may not be that hard. Electric water pumps have come a long way. One could be placed at the rear of the engine to pump coolant thru the engine toward the front, coolant exit would be close to the radiator and then a long hose from the rad to the ewp? The internal coolant passage modification that would be neccesary---IDK?
I wish I had the means to try this.
OD

Heat transfer is mainly due to the delta between the coolant temp and the temp of the parts they are cooling. The greater the delta..the more the heat transfer

If you think about it...the cooler side of the engine gets the coolant first when it is cooler...therefore the largest gradient in temps...

The hot side gets the warmer coolant...but is already warmer to begin with....so the gradient difference will still allow good transfer towards the coolant...and it then immediately exits the engine and goes to the radiator.......much better than the other way..that would result in the charge getting more heated during compression than needed...and trying to mimic a diesel

A few points:

1) If hot radiators in general explode when water is sprayed on them, they would also do so in a sudden rain or splash of water from a puddle. If such occurances cause massive metal fatigue, street car radiators (the ones not made from plastic anyway) would fail quickly. An exception might be if a modder is foolish enough to rigidly bolt it to frame members with no provision for expansion/contraction of the cooling tubes.

2) Water spraying works primarily through evaporation, and not via the heat capacity of the liquid. One can easily see why this is so from the attached pic. (Copied from here: http://hyperphysics.phy-astr.gsu.edu...rmo/phase.html ). It shows the amount of energy it takes to heat water through the ice/liquid/gas phases. 0 C to 100 C takes 420 J/kG. 100 C to 101 C takes 2300 kJ/kG, or ~ 5 times as much. Chilling the sprayed water beforehand is pretty useless. 0 C to 101 C will give you 5% additional cooling compared to 30 C to 101 C.

Of course moving air will also evaporate water and at temps well below 100 C. Still, it's well established in the HVAC world that a water (primary circuit)/water/air heat exchanger is vastly more efficient than water (primary circuit)/air one. Virtually every large building has heat exchangers on the roof that work with water evaporation this way. If you want to experience the effect first hand, go outside on a hot day and spray your AC condensor with a garden hose - the effect inside is immediate and dramatic. Don't do that on a regular basis though, cause you'll get scale buildup on the fins and reduce your long-term efficiency. This is also the downside of routine water spraying car radiators/intercoolers.

As far as the -8, most of the reported non-track cooling problems come from low-speed or stopped conditions which water spraying will be of limited help solving due to the lack of airflow. Otherwise, why not use it when needed?

I've not experienced it and the couple of reports I ran across didn't specify which one, but I'd assume it would be on the suction side (lower hose). I doubt if this occurs with new hoses and the factory configuration, but there are two elements of the stock layout that may help. The first (according to CW) is that the stock water pump (assuming stock pulleys) cavitates at high rpm effectively putting a limit on the amount of suction the wp can generate. Second, in the middle of the stock hose is a metal fitting which supports the hose in a rather long staight run. Going to a more efficient, non-cavitating pump will generate more suction. Getting rid of the metal fitting in the interest of simplicity or pusuit of the Golden Idol (flow) may either alone or together with a better pump result in hose distortion or collapse.

Note I'm just speculating (hence the original question) wrt the RX-8, but not so in other cases. In the good old days, we used to run into this problem fairly often. Hoses were pretty bad back then and often had metal coils (spring-looking thingies) inserted into long straight hose runs for support. If you pulled it out, the hose would suck right down flat when revving the engine. :SHOCKED:

Heat transfer, big time! Since it's all radiative however, a simple piece of thin aluminum blocking the line-of-sight between the two will cut it down to almost nothing quite easily.

How easy is a swap to do? (Street car). I'm already having some trouble with 3/4 at only 21k miles on the car. I'd hate to get the stocker repaired only to have the problem show up again in another 20k miles.

i run the 09 trans--and have been for over a year. bolt in swap.
Its heavier and bigger-so it does put it closer to the exhaust--like you say just shield it.
Also you cannot refill the trans fluid from up top --you have to do it the normal way.
Get a syncro saver and you can really jam the gears with no fears. The space between the throws is a little wider than the S1 model, the 3/4/5 gears ratios are much closer making accelleration and downshifting easier. You dont need a short shifter with it, the oem one is just fine. Reverse is in the right spot also.

Dan--didnt understand youre post? My thought was no hot/.cooler coolant. All coolant when it enters the engine would be same for both sides combustion and exhaust.
Per just laser surface temps--not very accurate i know---the exhaust side surface of the engine(not header!) is always hotter than the combustion side.-20-30 degrees F and thats on the surface.
OD

Except for the PPF, which is a deal-breaker.

Not worth the price of admission :) Cheaper to find a working used one. The parts are stupid expensive...even if the labour is free :)


I have 2 spare that I have picked up for $500 or less each...one with 3200 miles on it...and the other with about 20 ( idiot wrecked it on a test drive :) )

LOL.
I have one of those, too!

Wish I could have gotten that engine :)

you people are soo obsessed about running engine cool. sure you should not let it overheat, but running it too cool is not necessary good otherwise thermostat would never be invented.
if a rotary can do 100k miles with stock setting like some people have done, means its got enough cooling.