Why use higher pressure radiator cap?

[prsrcokr]

Can anyone tell me if a higher pressure cap is needed with a larger radiator? To me, the pump won't be pushing more fluid and so it's more pressure the lines and gaskets will see before coolant is pushed to the overflow, I'd rather let that happen than let the hoses see more pressure than usual.

Is there some other reason I'm missing? Seems like with more cooling capacity, the system shouldn't see higher pressure than a stock system.

Thanks for any help,
Brian

 

[jdub]

You shouldn't use a higher pressure cap on a street car. The higher pressure will push the coolant boiling point higher, useful for a race car that's running water with a wetter additive. On a street car using a 50/50 coolant to water mix, you do not need it.

 

[tbcmorris]

^^^^^^exactly what i was going to say

 

[mkIIIman089]

You shouldn't use a higher pressure cap on a street car. The higher pressure will push the coolant boiling point higher, useful for a race car that's running water with a wetter additive. On a street car using a 50/50 coolant to water mix, you do not need it.

I feel like this is insinuating that coolant gives more advantage than it actually does. Typical glycol antifreeze is something like 4-5 deg F higher boiling point over normal water at the same cap pressure.

Race car's 35-40psi caps dramatically raise the boiling point, but it's not to compensate for the lack of antifreeze.

That being said, for a high horsepower circuit raced supra, a higher cap will give you a bit more security from boiling over if you run it very hot. On a street car, it's more just a hose leak machine.

 

[jdub]

I feel like this is insinuating that coolant gives more advantage than it actually does. Typical glycol antifreeze is something like 4-5 deg F higher boiling point over normal water at the same cap pressure.

Not true. A 50/50 mix ethylene glycol to water coolant will boil at 223 deg F...a 70/30 mix will boil at 235 deg F. Both temps assume sea level pressure and exceed the temp (212 deg F) where the stock ECU pulls timing. Under higher pressure coolant boiling temps go higher as well.

There is no advantage to running a high pressure cap on a street car. The system still needs to be pressurized to handle temp spikes or above normal run times with high OAT. It's more than just a hose leak machine

 

[mkIIIman089]

Not sure I really understand what the pun is...

 

[jdub]

Not sure I really understand what the pun is...

No pun, there's an underlying reason a coolant thermostat is a very important part of the overall engine system. The wink was a clue...I guess you need it spelled out. Since I'm in a relatively good mood, I'll repeat myself from numerous posts over the years, but it also forces me to point out that what you posted in post #4 is actually way off base.

The TCCS used on Toyota engines "look" for a very specific coolant temp range for normal operations. On the 7M, it's 176 to 212 degs F. Below that, the ECU commands warm-up enrichment...this is why running with no T-stat (a very common word-of-mouth mod) is not a good idea. You will run consistently rich. Above the range, the ECU will pull timing in an effort to prevent excessive combustion chamber temps to prevent detonation. In that sense, it is a lot like what a code 52 (knock sensor) does.

The stock OEM thermostat rating is 190 degs F, right smack in the middle of the range. I wonder why that is

As stated earlier, a 50/50 mix of ethylene glycol to water coolant will boil at 223 deg F...that is at atmospheric pressure. The stock cap is rated at 10.7 to 14.9 psi...that pressure will easily increase coolant boiling temps by 35 deg F. The result is a top temp (~260 deg F), well above where the ECU pulls timing, but provides the ability for the engine to run under extreme conditions. There is no need for a higher pressure cap on a street car.

You stated:

On a street car, it's more just a hose leak machine.

Nothing is further from reality. The T-stat's function is to keep coolant in the correct temp range, otherwise the ECU takes corrective action. The cap (at it's stock rated pressure) is there to prevent the coolant from boiling over at a temp (assuming 50/50 = 223 deg F) just above the top of the ECU's desired range. The cap provides a safety margin against dumping coolant on the ground with a minor overheat...at the same time, the ECU pulls timing in an effort to keep temps down.

You also stated:

Race car's 35-40psi caps dramatically raise the boiling point, but it's not to compensate for the lack of antifreeze.

A higher pressure stat on a race engine is there for precisely this reason...if it's not there to compensate for no coolant (i.e. straight water), why do race cars run a high pressure stat? Water's boiling point is lower than a 50/50 coolant/water mix, but straight water's ability to transfer heat is greater...that is why race teams use straight water with a wetter additive. The problem is the boiling point...the solution is to compensate by raising that boiling point with a higher pressure cap (and upgraded hoses).

People that run a higher pressure cap (which allows higher coolant temps) or they run a 160 deg stat in an effort to "run cooler" are not doing their engine any favors. Straight water in a street car coolant system is just as foolish, the engine needs the corrosion inhibitors in the coolant. Like I said earlier, a track car is a different story...the engine is torn down every few races or once a season. Plus, running a race engine on a stock TCCS is not the best move anyway.

 

[mattsplat72]

The stock OEM thermostat rating is 190 degs F, right smack in the middle of the range.

Hey Jdub, I asked in a previous thread about " normal temps" for my car.
I consistently run at 180df, temp spikes to 200df at shut down. If the OEM thermo stays closed till 190df how is coolant getting cycled through my system? I am assuming that I am misunderstanding the informatio...

So now to the point I need/want a new cap I want to get a TRD one from RHDJapan I have a choice between 1.3 and 1.5 bar
http://www.rhdjapan.com/home/search...id=&int_category_id=&str_keyword1=trd+rad+cap

What one would you suggest I get.
Fluidyne Alum rad, Stock fan shroud newer fan clutch and a 10 blade

 

[jdub]

Matt - That temp range is perfect. Keep in mind a stat will start to open at a temp less than it's rating. I've tested numerous 190 stats and have had them start to open anywhere between 175-180 deg F....full open occurred between 190-200 degrees. These were all new stats, OEM and Stant SuperStats. I always test a T-stat before I install it...I've returned several immediately because they opened too soon or too late.

The point is, as soon as the stat opens just a crack, coolant is flowing to the radiator. On systems that have excess cooling capacity (like a big, dual core radiator), the T-stat may never fully open. The flow is sufficient to keep coolant temps in check. I suspect this is your case, which is good I might add.

BTW - I always cut the jiggle valve off the T-stat to provide a bit of flow at all times...it prevents a pressure build-up behind the stat (that can hold it closed) and gets air out of the system quickly. Never a need for the famous "7m burp".

There is no reason for you to run a higher pressure cap...you just asking to blow a hose. If you want a cool TRD cap, get a sticker and put it on a stock cap.

 

[IJ.]

I'd be more concerned at a 20 year old heater core

 

[upgradedsupra]

I'd be more concerned at a 20 year old heater core

lol

 

[mkIIIman089]

No pun, there's an underlying reason a coolant thermostat is a very important part of the overall engine system. The wink was a clue...I guess you need it spelled out. Since I'm in a relatively good mood, I'll repeat myself from numerous posts over the years, but it also forces me to point out that what you posted in post #4 is actually way off base.

The TCCS used on Toyota engines "look" for a very specific coolant temp range for normal operations. On the 7M, it's 176 to 212 degs F. Below that, the ECU commands warm-up enrichment...this is why running with no T-stat (a very common word-of-mouth mod) is not a good idea. You will run consistently rich. Above the range, the ECU will pull timing in an effort to prevent excessive combustion chamber temps to prevent detonation. In that sense, it is a lot like what a code 52 (knock sensor) does.

The stock OEM thermostat rating is 190 degs F, right smack in the middle of the range. I wonder why that is

As stated earlier, a 50/50 mix of ethylene glycol to water coolant will boil at 223 deg F...that is at atmospheric pressure. The stock cap is rated at 10.7 to 14.9 psi...that pressure will easily increase coolant boiling temps by 35 deg F. The result is a top temp (~260 deg F), well above where the ECU pulls timing, but provides the ability for the engine to run under extreme conditions. There is no need for a higher pressure cap on a street car.

You stated:


Nothing is further from reality. The T-stat's function is to keep coolant in the correct temp range, otherwise the ECU takes corrective action. The cap (at it's stock rated pressure) is there to prevent the coolant from boiling over at a temp (assuming 50/50 = 223 deg F) just above the top of the ECU's desired range. The cap provides a safety margin against dumping coolant on the ground with a minor overheat...at the same time, the ECU pulls timing in an effort to keep temps down.

You also stated:


A higher pressure stat on a race engine is there for precisely this reason...if it's not there to compensate for no coolant (i.e. straight water), why do race cars run a high pressure stat? Water's boiling point is lower than a 50/50 coolant/water mix, but straight water's ability to transfer heat is greater...that is why race teams use straight water with a wetter additive. The problem is the boiling point...the solution is to compensate by raising that boiling point with a higher pressure cap (and upgraded hoses).

People that run a higher pressure cap (which allows higher coolant temps) or they run a 160 deg stat in an effort to "run cooler" are not doing their engine any favors. Straight water in a street car coolant system is just as foolish, the engine needs the corrosion inhibitors in the coolant. Like I said earlier, a track car is a different story...the engine is torn down every few races or once a season. Plus, running a race engine on a stock TCCS is not the best move anyway.

Thanks! The real reason I asked, instead of jumping to conclusions, was that you seem to post exclusively to try to boost your ego by making others appear wrong. This has not only lead to questionable information being stated as fact on some occasions (which I might add, seems to be taken as gospel from a mod/expert/whatever you are) but apparently you don't even read my post before spouting off! As you have now done twice in this thread - told me how wrong I was, then agreed with me by the end.

To simplify my post: (just for you! ) I think raised boiling point is provided mostly by the increased pressure, and to a lesser extent antifreeze. Don't buy a higher pressure cap for your road car, it'll just cause more leaks.

(You addressed the coolant boiling point, and then went on a tear about things I never even spoke about! Even though you agree with the end point to not use one on a street car.)

And quite frankly ANYTHING you say about "racing" is completely anecdotal, seeing how you don't seem to have the slightest notion how things really work on a race car, or what "race teams" do. Since the industry in general is quite secretive about their actual practices, your best bet is to avoid bringing it up.

 

[jdub]

It's funny you would focus on the only statement in your original post that was truth.

That being said, for a high horsepower circuit raced supra, a higher cap will give you a bit more security from boiling over if you run it very hot.

What about the rest of the post? Care to enlighten this old man with an ego about what you really meant about:

I feel like this is insinuating that coolant gives more advantage than it actually does. Typical glycol antifreeze is something like 4-5 deg F higher boiling point over normal water at the same cap pressure.

(it's 10-15 degs F)

And:

Race car's 35-40psi caps dramatically raise the boiling point, but it's not to compensate for the lack of antifreeze.

(so, you telling me race teams don't run water?)

And:

On a street car, it's more just a hose leak machine.

(implies the cap is useless on a street car?)

Or are you going to come back with the same sarcasm in an effort to discredit the guy who had the audacity to correct you?

Thanks! The real reason I asked, instead of jumping to conclusions, was that you seem to post exclusively to try to boost your ego by making others appear wrong. This has not only lead to questionable information being stated as fact on some occasions (which I might add, seems to be taken as gospel from a mod/expert/whatever you are) but apparently you don't even read my post before spouting off! As you have now done twice in this thread - told me how wrong I was, then agreed with me by the end.

Boost my ego? You think a F-16 Fighter Pilot needs to post in a car forum to boost his ego...LMAO!!! That is without a doubt the funniest thing I have heard in a very, very long time. I was zorching around the desert at 100', just under Mach 1 when you were still shitting your diapers son...you have no clue what an ego really is. I do know whose ego is a bit bruised though...pretty typical for a guy who is not even old enough to drink yet in our modern, progressive society.

I did read your posts thoroughly and posted appropriately with more than enough facts to back it up. Now tell me what what questionable information I've posted?
If you are going to say crap like that, back it up punk.

To simplify my post: (just for you! ) I think raised boiling point is provided mostly by the increased pressure, and to a lesser extent antifreeze. Don't buy a higher pressure cap for your road car, it'll just cause more leaks.

(You addressed the coolant boiling point, and then went on a tear about things I never even spoke about! Even though you agree with the end point to not use one on a street car.)

That is not what you said in your previous post (#4)...it was a bunch of cryptic crap and you are trying to say it was accurate? I guess you think 1 statement out of 4 is good to go. And, that 1 correct statement is a repeat of what I already posted. Your problem is your little cat got hurt because you got called on it. And, now you are doing the "saving face" back pedal common for guys your age.

What you are completely ignoring is the engine in any car is a system...what happens to one component, has an effect on another. My post was meant to illustrate that...something your limited intelligence and experience has obviously not yet been able to grasp.

And quite frankly ANYTHING you say about "racing" is completely anecdotal, seeing how you don't seem to have the slightest notion how things really work on a race car, or what "race teams" do. Since the industry in general is quite secretive about their actual practices, your best bet is to avoid bringing it up.

Seeing how you do seem to know just enough how a automotive engine works to be dangerous, you're trying to tell a guy who has been playing with high performance cars for over 35 years that I don't "know anything". I guess you are going to tell us all about what "race teams do" based on your vast experience. That's pretty damn arrogant coming from someone who has to use sarcasm in a lame attempt to justify their position.

Go ahead...post some facts boy and prove what I said is wrong, or are you not man enough to take me on? If you're going to whine and post the same type of BS above, take it to your buddies or go home and whine to your momma. You might get some sympathy there...you are way out of your league here. What really kills me is I had respect for you and what you have posted in the past on SM...I thought you were more mature than most...you pretty much destroyed that perception.

 

[Doward]

Colin, don't be a dick. Seriously, there are quite a few guys on here that have not only participated in various forms of racing, but continue to do so on a daily basis. And if you want to really beat a coolant system into submission, go road racing

Jdub is 100% correct in all information provided, except one thing - 190 is NOT 'smack dab in the middle' of 176-212 194 is

See, when you post things like 'I think' it just verifies that you have NFI what you're talking about.

As Jdub stated, the boiling point of glycol is much higher than that of water. Go looks up Evans NPG if you want more proof. There are better alternatives than straight water.

 

[gofastgeorge]

I'd be more concerned at a 20 year old heater core

100% spot on.
Not only that, but the Japanese aftermarket caps will also tend to
overpower any place that you still have the original spring style hose clamps.
Like the connection behind the head.
(personal experiance)

Oh, and the temp spike after shutdown is normal.
It is because the head & block are still very hot,
and without a constant supply of coolant that has just come from the radiator,
the coolant in the engine still will go up to the temp of the engine
as it absorbs the heat off the hot spots in the head,
and then rise up to the thermostat housing (were the sensor is).

Remember, the coolant temp you see on the gauge
is that of what is flowing by the sensor at that moment.
It is not the temp of the head, especially around the exhaust ports.
It is not the temp of the coolant just coming out of the radiator.

 

[jdub]

Jdub is 100% correct in all information provided, except one thing - 190 is NOT 'smack dab in the middle' of 176-212 194 is

:runaway:


LMAO!

 

[figgie]

Thanks! The real reason I asked, instead of jumping to conclusions, was that you seem to post exclusively to try to boost your ego by making others appear wrong. This has not only lead to questionable information being stated as fact on some occasions (which I might add, seems to be taken as gospel from a mod/expert/whatever you are) but apparently you don't even read my post before spouting off! As you have now done twice in this thread - told me how wrong I was, then agreed with me by the end.

To simplify my post: (just for you! ) I think raised boiling point is provided mostly by the increased pressure, and to a lesser extent antifreeze. Don't buy a higher pressure cap for your road car, it'll just cause more leaks.

(You addressed the coolant boiling point, and then went on a tear about things I never even spoke about! Even though you agree with the end point to not use one on a street car.)

And quite frankly ANYTHING you say about "racing" is completely anecdotal, seeing how you don't seem to have the slightest notion how things really work on a race car, or what "race teams" do. Since the industry in general is quite secretive about their actual practices, your best bet is to avoid bringing it up.

What the fuck. I'll bite. Memorial day weekend is around the corner and it has been a bit since I have stretched my legs here.

Well to replace ancedotal with real life AND physics.

I have dealt with SCCA, IMSA, GT Touring, Porsche Cup etc. As Jdub stated, they all use water with "additives" to help in transfering heat away from the engine. Why you might ask? Simple...... IT IS IN THIER RULE BOOKS!!! It is not a secret. It is part of thier rules. The specific one is safety. If there is wreck. The water will just turn to vapor almost instantly upon being opened to atmospheric pressure. Any that lands on the track will evaporate quickly. And if a car runs over it, it won't go into a tail spin.
Antifreeze, glycol etc turn the track/street into a skating rink if it leaks. It will not evaporate quickly and will stay longer on the track. So there is no "secret" about thier cooling. It is part of all the racing series rule book to include NHRA, a slew of Motorcycling racing series, WRC, F1 etc.


Water's Volumetric Heat Capacity is the greatest of ALL liquids known to us when dealing in earth's atmosphere. The short coming of H2O is the not so great boiling point at 212F. All liquids follow certain rules which are a combination of rules from ideal gas laws, Kohlers Theory, Dalton's law, Bernoulli's principles etc.

One of the curious things about water is that as it gets heated up, it is one of the few liquids that continues to have a very high Volumetric Heat Capacity even when approaching its boiling point. Hence the reason why race teams use water as thier cooling fluid as they need to get the heat away FAST and in large quantity. Something that water is sutiable to do, only if we could get the boiling point up.

Ahhh but we can. Increase the pressure of the system in which the water is contained and the boiling point of water increases relative to the additional pressure. So now we can keep the water in the much needed liquid state thanks to the higher than normal system pressure without having all that water turn to steam.

There is a reason why those race teams use AN fittings for even thier cooling systems (-20 lines) and that is because they are seeing exceptionally high pressures.

 

[mkIIIman089]

-The antifreeze boiling point part? The one that I didn't contest after you corrected it (Without a reference, but I'll accept unless I find contradictory info)? What about it?

-No, what on earth would lead to that conclusion? I would have thought after 10 seconds of thought one would realize that antifreeze and water are not one in the same.

-Taken COMPLETELY out of context, I guess that would be confusing. All you'd have to do is read the thread title for it to make sense, though.

-Personal attacks from the interwebs based on age stereotypes, what a novel idea! Never heard that before! "Some occasions" does not mean I am directly referring to this incident.

- 1. I was low on the boiling point elevation, you corrected me. (incorrect) 2. Whether or not race cars run glycol antifreeze mixed with their water they do run much higher pressure caps. (Believe it or not, it's not mandated in all series to not run glycol) (correct) 3. Circuit raced Supras can benefit from higher pressure caps in the event of very high water temps. (correct) 4. Street cars will not see any benefit and will more likely than not result in leaks. (correct, AND you agreed)

I don't remember anyone questioning the function of the thermostat, how the ECU reacts to coolant temps, or even why it's unnecessary to run a higher pressure radiator cap. For some reason you took it upon yourself to ride in on your high horse and pick apart my post (some completely out of context) to state irrelevant information that you have already posted in the past, I'm sure.

-As for that last paragraph of militaristic drill sergeant sounding insults, all I can do is laugh because you seem to think that in the real world that will actually get you somewhere. I would have thought an "old man" would have learned that by now, but I guess one can only expect so much from someone being rocked in the cradle of some superior in a rigid system their whole life. As for respect? There are few things I care less about than the respect of some joker on the internet.

Doward - I'm not here to be a dick, there is a serious abuse of power from some of the "older" guys on here, especially from those with titles. It has been steadily increasing from funny poking at REALLY foolish people to this completely unsubstantiated attacking of people who word things slightly different than they would. If I intentionally post "I think" it's for a reason, to not speak in absolute truth and to invite correction if someone knows with undisputed fact otherwise. Typically I do it to at least point someone in the general right direction.

figgie - Sounds good to me! There are many amateur series that do not ban the use of glycol coolant though. Even semi-pro series like Rolex don't ban glycol based antifreeze.

 

[mattsplat72]

Thanks guys. You helped alot . Thank you for taking time out of your day and saving me money that I can't afford to spend. Imagine you did this for free....Sham wow.

 

[jdub]

-The antifreeze boiling point part? The one that I didn't contest after you corrected it (Without a reference, but I'll accept unless I find contradictory info)? What about it?

-No, what on earth would lead to that conclusion? I would have thought after 10 seconds of thought one would realize that antifreeze and water are not one in the same.

-Taken COMPLETELY out of context, I guess that would be confusing. All you'd have to do is read the thread title for it to make sense, though.

-Personal attacks from the interwebs based on age stereotypes, what a novel idea! Never heard that before! "Some occasions" does not mean I am directly referring to this incident.

- 1. I was low on the boiling point elevation, you corrected me. (incorrect) 2. Whether or not race cars run glycol antifreeze mixed with their water they do run much higher pressure caps. (Believe it or not, it's not mandated in all series to not run glycol) (correct) 3. Circuit raced Supras can benefit from higher pressure caps in the event of very high water temps. (correct) 4. Street cars will not see any benefit and will more likely than not result in leaks. (correct, AND you agreed)

I don't remember anyone questioning the function of the thermostat, how the ECU reacts to coolant temps, or even why it's unnecessary to run a higher pressure radiator cap. For some reason you took it upon yourself to ride in on your high horse and pick apart my post (some completely out of context) to state irrelevant information that you have already posted in the past, I'm sure.

-As for that last paragraph of militaristic drill sergeant sounding insults, all I can do is laugh because you seem to think that in the real world that will actually get you somewhere. I would have thought an "old man" would have learned that by now, but I guess one can only expect so much from someone being rocked in the cradle of some superior in a rigid system their whole life. As for respect? There are few things I care less about than the respect of some joker on the internet.

Doward - I'm not here to be a dick, there is a serious abuse of power from some of the "older" guys on here, especially from those with titles. It has been steadily increasing from funny poking at REALLY foolish people to this completely unsubstantiated attacking of people who word things slightly different than they would. If I intentionally post "I think" it's for a reason, to not speak in absolute truth and to invite correction if someone knows with undisputed fact otherwise. Typically I do it to at least point someone in the general right direction.

figgie - Sounds good to me! There are many amateur series that do not ban the use of glycol coolant though. Even semi-pro series like Rolex don't ban glycol based antifreeze.

So now you're being attacked...again typical. Where's the proof of your previous statements about me? Lets see you back it up. Abuse of power? Give me examples. Again typical, because there are none.
So you resort to the same tactics.

It is obvious to anyone that reads this who called as he sees it and who is pissing in the wind.

BTW - You don't know me or my accomplishments. I'll bet any sum of $$$ you desire what I have done in my professional career is several magnitudes above what you could ever possibly do. I am a military guy, one who does not tolerate this type of adolescent behavior. Keep it up Colin...you can continue making a fool of yourself if you so choose. For me, I'm done arguing with a child.