Shane661
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posted June 19, 2010 06:44 AM
 Edited By: Shane661 on 19 Jun 2010 15:34
quote:
But as Doug said at speed there isn't a cooling issue because the airflow thru the radiator is excellent. Its in traffic situations with low airflow thru the radiator that all cooling systems whether a car or a bike etc. are having a harder time removing BTU's from the coolant thru the radiator.
Doug actually stated that there would be no cooling issue in traffic as well. I think that everyone can agree that airflow across the radiator leads to more cooling.
quote:
Something interesting...
In the 1990's when GM was designing the LS family of engines they developed new processes to produce a better more true cylinder. On older aluminum V8 engines the cylinders needed to be thick due to core shift and to guarantee cylinder rigidity. This allowed for over boring of up to .06" or more on most blocks. Well these new processes on the LS family of engines allowed them to make the cylinders MUCH thinner. They use an iron liner as before and the block is aluminum. This doesn't allow more than a .005" overbore now, but the cooling of the engine was improved while maintaining better cylindricity and concentricity of the bores even with a thinner wall.
Making the cylinder thinner would naturally allow for much more efficient heat transfer. Let me guess...they sized the water/air side of the system accordingly??
Tell me this...if the thinner bore, and greater suface area of a bored and stroked motor allows for more of the heat to transfer to the coolant...doesn't it seem to reason that it is putting more load on the water/air side of the system? How can the coolant not be hotter if more of the heat is being transferred to it? I think that is about as simple as it gets.
Please explain the above. That is my main stumbling block, aside from the fact that 90% of the people with large motors seem to report that they do indeed run hotter on the street. Oh, and also the fact that for any equal given rpm and throttle position you are producing more heat (hp) with the larger motor.
Shane
  
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smokinZX14
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posted June 19, 2010 08:33 AM
Having built 100s of stroker motors ( cars ) i can say they do make more heat and run hotter .. In all cases i have increase the size of the Rad and the CFM of the fan or fans to be able to maintain the same temps on the street as the non stroked and bored motor it replaced .. If a stock rad has extra or more cooling than needed for a stock motor it may work just fine for a stroker or bored motor .. If the Rad is border line from the factory a larger Rad or more cfm fan will be needed to maintain temps ..Water pumps play the same role as the rad or fans , sometimes i will have to increase the flow rate ( GPM ) of the pump to move the water .. I see no reason a bike would not act the same way as a car .. My 496 motor in my roadrunner needed a 4 core rad plus a high flow pump to maintain the same 180 Deg temps on the street as the stock 440 did with a 2 core rad and std factory water pump .. Same cam , same heads , carb and same headers were used on both short blocks ..The only change was the CID of the short block ..
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biggmoinc
Zone Head
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posted June 19, 2010 09:01 AM
I would think the heating problems compared to built motors n stock motors would not be the thinner walls but rather the added compression, THis is why the motor runs (hotter) than a stock motor, not the larger piston surface, cause along with the wider piston, u get more fuel + more air so the AFR should still be in the comfort zone as a stock motor..........just my opinion, you guys know way more than i do but it seems to make more sense in saying added compression makes a motor work harder at any given rpm which would make the engine build more heat than the stock compression, in any case if u say the motor builds up heat with thinnner walls will it cool faster? THen the fan n radiator should be able to keep up with the heat n not run hotter, ;-), lol
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aliveagain
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posted June 19, 2010 02:38 PM
I used some air conditioner coil cleaner on my radiator. I was amazed at the amount of dirt which came out.
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Y2KZX12R
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posted June 19, 2010 03:21 PM
It is true that when you raise the compression of the engine that exhaust temps go down and head temps rise. More of the combustion is happening before the exhaust valve opens due to a quicker rise in cylinder pressures.
Going from 10 to 1 to 13 to 1 will put more heat into the head and thus the cooling system.
But the debate is over bore and stroke.
My wife drives a 502 CI BBC engine that makes well over 500 hp in her 67 chevelle ss street car and it has the same factory 4 core radiator still in it that cooled the 350 hp 396 that came in the car. It even has A/C in the car and never over heats and can sit and idle until it runs out of fuel on a summer day with the A/C on. It even still has the stock clutch fan and shroud.
We build hundreds of engines a year out of our shop and most cooling problems people have are self caused and due to bad setups. People take the shrouds off, they put flex fans on, they put too small of an electric fan on, or two few electric fans on, they take the thermostats out, they don't run over flow cans, too small of a radiator, improper coolant, bad radiator caps that don't hold pressure, etc. We see it all the time.
The bottom line is a 1375 or 1427 zx12r should not have any over heating issues on the street. Maybe if you live in Vegas and ride in 1st gear at 1500 rpm in traffic in the summer 100+ heat then ok i could see it. Imagine what the Harley's have to go threw under those conditions. That's why some places allow lane splitting on bikes.
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KZScott
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posted June 19, 2010 04:04 PM
quote:
It is true that when you raise the compression of the engine that exhaust temps go down and head temps rise. More of the combustion is happening before the exhaust valve opens due to a quicker rise in cylinder pressures.
Going from 10 to 1 to 13 to 1 will put more heat into the head and thus the cooling system.
But the debate is over bore and stroke.
i think the main issue here is that (im guessing) 95% of the guys that run a big bore or stroker and complain of heat, have raised the CR from 12.2:1 to around 13.5:1 or so, and then blame the displacement instead of compression
just a theory...
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smokinZX14
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posted June 19, 2010 05:09 PM
quote:
It is true that when you raise the compression of the engine that exhaust temps go down and head temps rise. More of the combustion is happening before the exhaust valve opens due to a quicker rise in cylinder pressures.
Going from 10 to 1 to 13 to 1 will put more heat into the head and thus the cooling system.
But the debate is over bore and stroke.
My wife drives a 502 CI BBC engine that makes well over 500 hp in her 67 chevelle ss street car and it has the same factory 4 core radiator still in it that cooled the 350 hp 396 that came in the car. It even has A/C in the car and never over heats and can sit and idle until it runs out of fuel on a summer day with the A/C on. It even still has the stock clutch fan and shroud.
We build hundreds of engines a year out of our shop and most cooling problems people have are self caused and due to bad setups. People take the shrouds off, they put flex fans on, they put too small of an electric fan on, or two few electric fans on, they take the thermostats out, they don't run over flow cans, too small of a radiator, improper coolant, bad radiator caps that don't hold pressure, etc. We see it all the time.
The bottom line is a 1375 or 1427 zx12r should not have any over heating issues on the street. Maybe if you live in Vegas and ride in 1st gear at 1500 rpm in traffic in the summer 100+ heat then ok i could see it. Imagine what the Harley's have to go threw under those conditions. That's why some places allow lane splitting on bikes.
Chevys cross flow rad is one of the best around for cooling , the same 4 core rad will cool a 454 no problem as long as it in good shape ..Now take a 383 or 440 2 core 26 inch rad and add 496 CID and it will run warmer no question about it .. Been there done that for the last 38 years .. If i could i would use Chevys cross flow rads in my Mopars but they will not fit in between the frame rails of a mopar ..
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aliveagain
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posted June 20, 2010 01:00 PM
No one has mentioned how having too much anti-freeze can reduce the cooling effect.Anti-freeze is a lousy heat transfer liquid, it is only good for raising and lowering the freezing and boiling points. If someone put straight prestone in,it may have its issues.
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Shane661
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posted June 20, 2010 01:03 PM
Edited By: Shane661 on 20 Jun 2010 21:07
To me the bottom line is this:
Big motors typically make more hp, and often over the entire powerband. HP= Heat.
Thinner cylinder walls and increased contact area = more heat load on the cooling system.
As to whether the engine will "overheat", that is a different issue. But it will produce more heat overall...and more heat will be transferred to the coolant...there is no doubt.
Shane
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dougmeyer
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posted June 20, 2010 02:35 PM
Well, you're getting there, but it only makes "more heat" when you are running it in the "more power" part of the curve, otherwise the heat's the same. Big or small, it doesn't matter power=heat over time. The thickness of the cylinder wall is not as important as the material and the head (combustion chamber) is by FAR where most of the heat gets into the cooling system, not the cyl. wall. And remember we're talking about small and "big" versions of the same engine here. These aren't opinions, Shane, this is all basic engineering fact determined of the last 75 years of IC engine development.
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Shane661
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posted June 20, 2010 02:43 PM
Edited By: Shane661 on 20 Jun 2010 23:57
quote:
Well, you're getting there, but it only makes "more heat" when you are running it in the "more power" part of the curve, otherwise the heat's the same. Big or small, it doesn't matter power=heat over time. The thickness of the cylinder wall is not as important as the material and the head (combustion chamber) is by FAR where most of the heat gets into the cooling system, not the cyl. wall. And remember we're talking about small and "big" versions of the same engine here. These aren't opinions, Shane, this is all basic engineering fact determined of the last 75 years of IC engine development.
Doug, the basic facts are this:
1) A big motor is generally making more power overall. That is why we build them. Hence we ride them that way. HP=HEAT...and the big motor makes more of both. The people who ride these bikes are not holding a magnifying glass to their wrist's in order to ensure stock power output.
2) The cooling system is a heat exchanger. The larger bore and/or increased stroke equals more heat exchange to the coolant. Cylinder wall thickness is essentially an insulator. By reducing the thickness of the walls you are increasing the amount of heat transfer, as is the increased surface area of the bore. Any increase in stroke also increases the surface area of the exchanger. Even if the power output were only equal, more heat would still be transferred to the coolant due to the increased efficiency of the heat exchanger. The capability of the cooling system to remove the heat has not been changed, but the amount of heat added to it has been increased.
The bottom line is that the above line items are not factually disputable by anyone...even an MIT graduate. This is also an "engineering fact".
Shane
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dougmeyer
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posted June 20, 2010 04:29 PM
Too much misinformation in your response for me to mess with. Maybe someone else cares enough to give it a try.
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Shane661
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posted June 20, 2010 04:30 PM
Edited By: Shane661 on 21 Jun 2010 00:59
quote:
Too much misinformation in your response for me to mess with. Maybe someone else cares enough to give it a try.
Translation: "I can't dispute what you have said".
Maybe you just don't have anything condescending enough to say right now? Surprising, since your prior posts have been tantamount to calling me an idiot.
To repeat my above comments:
1) A big motor is generally making more power overall. That is why we build them. Hence we ride them that way. HP=HEAT...and the big motor makes more of both. The people who ride these bikes are not holding a magnifying glass to their wrist's in order to ensure stock power output.
2) The cooling system is a heat exchanger. The larger bore and/or increased stroke equals more heat exchange to the coolant. Cylinder wall thickness is essentially an insulator. By reducing the thickness of the walls you are increasing the amount of heat transfer, as is the increased surface area of the bore. Any increase in stroke also increases the surface area of the exchanger. Even if the power output were only equal, more heat would still be transferred to the coolant due to the increased efficiency of the heat exchanger. The capability of the cooling system to remove the heat has not been changed, but the amount of heat added to it has been increased.
Thanks to Doug, for his input. For everyone else, read my above comments and expect your big motor to run at least a little warmer than your stocker. 
Shane
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aliveagain
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posted June 20, 2010 05:34 PM
The only time I had an issue was when my fan didn't kick on in stop and go traffic. Plain and simple ,there was not enough air flow to transfer all the heat away. Hp had nothing to do with it. I guess the way to solve this debate would be to have a big bore and a stock bike idle side by side and see how often and for how long the fan cycles.
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shiphteey
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posted June 20, 2010 06:13 PM
I could take my stock 12 motor over to Shane's house and crank em up both at the same time, same fuel and see what happens.
Only issues would be isolating all the variables so we'd need:
Same fuel
Same coolant mix
Same oil and level
Variables that we can't easily control are his big bore's compression is over stock....that and mine runs uber rich down low dumping tons of fuel and can skew the results.
A.
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dougmeyer
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posted June 21, 2010 01:26 PM
Shane,
At NO TIME did I intend to be insulting or condescending. These things are not personal like politics. It's just stuff we like to play with, after all. I'm just not doing a good enough job of explaining the physics. I could bore you with stories, but that wouldn't prove anything. I've been traveling all over for the last 11 days, but I'm home now. I'll dig up some support data to try and clarify this stuff for y'all.
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Shane661
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posted June 21, 2010 01:57 PM
Edited By: Shane661 on 21 Jun 2010 22:00
quote:
Shane,
At NO TIME did I intend to be insulting or condescending. These things are not personal like politics. It's just stuff we like to play with, after all. I'm just not doing a good enough job of explaining the physics. I could bore you with stories, but that wouldn't prove anything. I've been traveling all over for the last 11 days, but I'm home now. I'll dig up some support data to try and clarify this stuff for y'all.
Thanks, Doug. It's really nothing personal. I am just more interested in "real world" results than physics. I also have a simple laymans understanding of heat exchangers, because it is part of my daily job. 
Shane
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SteddyTeddy
Pro
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posted June 24, 2010 12:05 PM
Real world. I did an 2x4 on my ZRX motor. First build was same CR and same head package. The bike went from hardly ever having the fan come on to the fan coming on at every stop light. Installed larger radiator and now no problems.
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shiphteey
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posted June 24, 2010 03:32 PM
Good info there S-Teddy.
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dougmeyer
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posted June 24, 2010 03:56 PM
Same timing and jetting or re-calibrated for the new configuration? Same OATs?
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Shane661
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posted June 24, 2010 05:45 PM
Edited By: Shane661 on 25 Jun 2010 01:59
Can I ask you once again Doug...if you know the motor makes more power (and even at low rpm), why would it not make more heat? At what point does a large, well-tuned engine not make more power under acceleration? Without taller gearing, how are you keeping average power output the same, while under load? These aren't steady-state cruising comparisons...people are twisting the grip....and the bike is accelerating harder as a desired result.
Also, if the thickness of the cylinder walls is reduced...and the surface area of the exchanger increased...why would more heat not be in the coolant? And if the cooling system is being taxed with additional heat...well...oh nevermind....
The bottom line is that more hp is more heat...and these motors will make more average power under general operating conditions. That is why we build them, obviously.
Shane
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dougmeyer
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posted June 24, 2010 08:49 PM
My timing/jetting answer was directed at the ZREX example cited above, not an acceleration example, but.....
OK I'll give it another shot.
First, "power" (horsepower) only exists when torque is present, agreed? (Torque x rpm/5252= hp)
And, can we agree that it takes a certain amount of power to just keep the engine running, right? And given that our comparisons are based on a single type of vehicle with a given rolling resistance and aero drag, and this occurs on a flat surface under the same atmospheric conditions, it takes a certain amount of force (torque)to move that vehicle down that road at that speed. Right?
OK lets say it takes 3 hp to keep the engine idling. Maybe 10 to go 30 mph, and probably 40 or so to go 65 mph.(I'm estimating those, of course, but they are close).
We've got a cooling system that will dissipate the heat created under those conditions through a liquid to Air heat exchanger to the air. That cooling system is sized to dissipate 150+ hp continuously at temperatures up to at least 100F OAT or so.
BUT, there has to be SOME adequate airflow at the radiator to move the heat from the coolant to the surrounding air. In some cases the stock systems are not good enough to do that at anything above a dead idle. But that's not because the engine is producing more heat, it's because the cooling system is not functionung.
So now we've got two engines a stock one and a "big" one, everything else is the same. We are asking them both to idle, go 5, 10 30, 50 mph and each is required to put forth exactly the same power as specified above as required to accomplish that task. On what grounds do you expect that the larger one is A) putting out more power, and B) that the extremely under-taxed cooling system is incapable of maintaining the same coolant temperature (which is, of course, regulated by a thermostat so you wouldn't see the change anyway)?
Now lets go to acceleration. Call it a 1/4 mile. The big engine going to need to create more power to accomplish the desired quicker time. Lets say we've got a 180 hp setup and a 200 hp setup. That's about a 12% increase in power. IF the increase in heat output was linear (and it's not) we'd expect the heat into the coolant to go up 12%. Do you think that the cooling system, which is designed to be capable of cooling that bike running 90 mph down US 50 in Nevada on a 110 deg day, a would be incapable of leveling that out in 10 seconds? Just askin'
OK Top speed- and I'll throw in a little anecdotal story of my own. In 26 years of LSR racing at Bonneville running highly modified air-cooled and water cooled bikes on gas, nitro and turbos, making HUNDREDS of 5 mile passes
at wide open throttle for up to 2 minutes, with STOCK radiators and bodywork, I've never rolled off the throttle with the temp higher than the normal operating range. And I wouldn't expect to.
Data exists for all this, but the math bores me so I'm not going to do that.
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Shane661
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posted June 25, 2010 02:35 AM
Edited By: Shane661 on 25 Jun 2010 11:20
Ok, a few things:
quote:
So now we've got two engines a stock one and a "big" one, everything else is the same. We are asking them both to idle, go 5, 10 30, 50 mph and each is required to put forth exactly the same power as specified above as required to accomplish that task.
The example above would apply to steady-state cruising speeds, not dynamic load conditions as applied on the street.
Let's assume, for simplicity, that accelerating your bike from 0-100 mph in 4.5 seconds will produce the same total heat load on the system as doing it in 2 minutes. Even if the total heat produced were equal, you would be asking the system to dissipate the heat much more quickly...agreed?
quote:
On what grounds do you expect that the larger one is A) putting out more power, and B) that the extremely under-taxed cooling system is incapable of maintaining the same coolant temperature (which is, of course, regulated by a thermostat so you wouldn't see the change anyway)?
The larger engine is producing more power, because it has been built, and is being ridden in a manner to do so. Do you drive your 'Vette in a manner so as to produce the same average power output as a Kia? Seriously?
While citing power difference at peak is one thing, you may see a greater increase by percentage at a much lower rpm...depending on the setup.
I am not concerned with whether or not the system is "overtaxed". I am concerned, in this debate, over the amount of heat produced by the engine under typical operating conditions. Whether the system is undertaxed should not even be a concern, if the engine is not producing more heat, correct?
As far as regulation by the thermostat, again, a moot point. Why would there be any change if there were not more heat being produced? It seems obvious to me that you are conceding that the engine WILL produce more heat, but that it will somehow be "transparent" to the rider?
quote:
Now lets go to acceleration. Call it a 1/4 mile. The big engine going to need to create more power to accomplish the desired quicker time. Lets say we've got a 180 hp setup and a 200 hp setup. That's about a 12% increase in power. IF the increase in heat output was linear (and it's not) we'd expect the heat into the coolant to go up 12%. Do you think that the cooling system, which is designed to be capable of cooling that bike running 90 mph down US 50 in Nevada on a 110 deg day, a would be incapable of leveling that out in 10 seconds? Just askin'
I think that when you do a smoldering burnout, stage the bike at 7000 rpm, lay down more hp, and then cruise back to the pits at 15 mph...well, all of those will combine to put more load on the system.
quote:
OK Top speed- and I'll throw in a little anecdotal story of my own. In 26 years of LSR racing at Bonneville running highly modified air-cooled and water cooled bikes on gas, nitro and turbos, making HUNDREDS of 5 mile passes
at wide open throttle for up to 2 minutes, with STOCK radiators and bodywork, I've never rolled off the throttle with the temp higher than the normal operating range. And I wouldn't expect to.
Hardly applicable to street or even dragstrip operating conditions. You are describing a situation of maximum coolant and air flow.
I doubt that we are going to agree on this, Doug. You are convinced that you are correct, and quick to dismiss all "anecdotal" evidence to the contrary. I feel that I fully understand your logic, but your argument is not compelling to me. I think that you are trying to put rigid constraints on a scenario (street riding) that is very dynamic.
Shane
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SteddyTeddy
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posted June 25, 2010 04:50 AM
quote:
Same timing and jetting or re-calibrated for the new configuration? Same OATs?
Same timing, I think my mains were upped 1 size at the time. Oh and it was 50* outside at the time. The bike made 10 to 25hp more through the entire RPM range and nearly 10 ft -lbs of TQ. More power = more heat, right? Current build is at 14:1 CR with OS valves. Jetting was upped about 4 sizes but timing is set the same. It really uses the larger radiator and I've been debating about installing an oil cooler as well.
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dougmeyer
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posted June 25, 2010 01:13 PM
10 to 25 more hp only at wide open throttle though, right? You were indicating more heat at stoplights.........
Does your bike run any hotter while riding or racing while you are asking it for that extra power?
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It's not that I think you're dumb, it's just that so much of what you know isn't true....
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