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  #16 (permalink)  
Old 06-26-2008, 08:10 AM
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my first thought is:
"fair chance" that your motor does not like whatever your hwy cruise rpm's ign timing is set at and/or the Air/Fuel mix(!) at constant hwy rpms....

if not enough underhood air flow at hwy speed was the problem source it would show up big time in stop and go intown driving!!!....

at hwy cruise rpms the motor is basically "loafing" and only making roughly 60-80HP worth of heat to maintain the hwy speed versus minumum 150HP+ to accelerate from a stop sign....

my point is adding air flow should be your very very last resort....
"something" is generating way way more heat "at" hwy speed than normal.....
don't "engineer your way around the problem" especially since the coolant temp rise indicates the oil is getting hotter than it should "loafing" at hwy speed
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Old 06-26-2008, 09:14 AM
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Well I'm open to all input here, and am getting some pretty good theories.
Because of space issues, I am running a undersized rad for the engine. It has been custom re-cored, with a modern core design, fin count, and larger bottom tank, but I no doubt it is under capacity. The Ford Taurus 2 spd fan (will pull small animals to the front of the car when on high LOL ) makes a huge difference, and running RMI-25 (form of water wetter) and distilled H2O has dropped the temps.

I really think it is an airflow problem. either in, or out. I just thought because of how tight the engine compartment is that air is being trapped in there and somehow at hwy speed it's having a hard time escaping. Could be caused by my low sitting intercooler scoop acting as an air dam and interrupting the below car air flow? I though the draft tubes would counteract the effect of the scoop.

I'm really giving a lot of thought to the idea of not enough air being directed into the rad at speed.

Great point about the AFR and timing at cruise RPM. I am able to alter both. I have the ability to engage a lean cruise mode and set whatever AFR I desire. I may play with a richer mixture to see if it has an effect. I'll have to check what the chips no load timing is set at.

Just to be clear the car does not radically overheat, I just notice that the temp is a bit higher than normal and the fan stays on. If I am cruising at a lower rate of speed it temp is ok, but if I cruise at a higher rate of speed temps will climb a bit. (car is 2800 lbs, fairly aerodynamic, so the load from one mph to the other isn't significant)

I really appreciate all the input.
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Old 06-26-2008, 04:34 PM
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you likely posted the key words in your last post: "undersized radiator"

speaking in the most general terms just for the idea because I don't know how far out of balance your system is:
you will have to increase air cfm thru the to small radiator by a factor of about 4 to equal what just 10% more coolant gpm thru that radiator will do....
the good news is just about any radiator is not operating at it's max possible btu transfer rate based on the normal pump gpm and available air cfm thru the radiator at hwy speed....

simple to test to tell if more gpm thru the radiator/less bypass helps keep the temp stable:
warm the motor up till the thermostat is open then clamp off the pump bypass hose and heater hose so 100% of the pump output goes thru the radiator.....go for a test drive

"fair to good chance" the temp will be stable (small chance the fans will even turn off)

if the test shows good results the simplest fix is change to a high flow thermostat with bypass holes (Stewart) for motor warmup so more gpms are directed to the radiator at normal operating temp

plan "B" is change the pump pulley diameter for a bit more overdrive ratio for more gpm thru the radiator at hwy speed

plan "C" is add a oil cooler.....they do help alot

but...... I would definitely experiment/test the A/F ratio and timing first...
just a 2* timing change can make a 10* coolant temp change....
it is possible the problem is a bit of all of the above (timing/fuel/coolant gpm)
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Old 06-26-2008, 05:36 PM
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Just a bit more background on the setup...
I am running an overdrive pump pulley, flowcooler pump and high flow stat. The Taurus fan pulls around 4500 cfm on high (85A starting draw, 33a continuous)

Just curious... What is the down side to running with the bypass plugged fulltime? (car isn't driven in the winter, so warm up time doesn't come into play)

I used to run an oil cooler, but have run out of locations to mount it. (aux tranny coolers) I do run a dual remote filter setup, so I have upped the capacity slightly, and they sit above an air vent, so there is some cooling effect.

I do have the option of playing with the AFR's and timing, but know a few other Grand national owners who run the same timing and AFR's as I do, and have no heat problems. I don't think there is anything radically out of line at cruise speed, ( timing and AFR wise) but some tweaking may help a bit.
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Old 06-27-2008, 09:21 AM
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because you have a good pump and overdrive pulley and high flow stat, lack of gpm thru the rad when just cruising is not likely the source of the problem at all....

YUP! you do have a air flow problem!
move the 2 tranny coolers!
(atleast mount them on standoffs forward of the radiator face surface to allow more air to get behind them and thru the rad)....(air will always flow based on the path of least resistance)
as the speed increases the increasing air mass pressure on the cooler faces is mis-directing more and more air from going thru the rad....
it's not over heating in town because the fans can suck hard enough to pull a vacuum thru almost all of the radiator surface

again, just for the idea and from my experience about coolers:
(for the majority of street driven applications), oil coolers and tranny coolers are darn effective/efficent just as long as they do have signifigant ambient air temp cfm flow over them....
(ex: police cars/some big block muscle cars have the oil cooler oem mounted on the upper radiator support to catch air from the hood lip to rad support gap)

do also mount your oil cooler! (as your car is operating now you have "0" cooling reserve capability built in)

possibly behind a hole/gap in the lower apron or on stand offs in front of your intercooler?
"if" you can find room and have a few bucks mount a oil or tranny cooler with it's own cooling fan and thermostat to have the best....max cooling at a stop light and on the road
(kind of a pia and scary as hell to me but coolers "do" get mounted in the wheel wells with stone guards for rocks thrown by the tires)
street rod coolers look like a length of pipe with the fins in the car travel direction so they can be tucked up along the car bottem....

just one of many good reasons to keep atleast one bypass route open is pump bearing life....
at rpms, driving with the thermostat closed, the bypass helps reduce the pump actual operating pressure for less side load on the bearing

one more thing to check:
the dead air space at the top of your custom mount radiator needs to be hopefully atleast 2" above the highest water jacket point on the motor so the system can/will constantly purge any air
CRS=I can't recall if Gand Nationals did have a seperate purge tank system due to rad mount position???

move/change the tranny coolers...the combination of not enough rad tubes and fins area and "lost" air flow thru the rad is killing you (without exellent shrouding your fans are just re-circulating alot of hot engine compartment air)

Last edited by red65mustang; 06-27-2008 at 09:46 AM.
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  #21 (permalink)  
Old 06-27-2008, 09:40 AM
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Just another thought (I've been struggling with this issue since I got mine on the road a couple weeks ago) I found the lower radiator hose was collapsing at cruise speed and restricting the coolant flow. Around town it was fine, because the RPMs were lower. I had neglected to put the internal spring in the hose. (so that's what those are for!! )
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  #22 (permalink)  
Old 06-27-2008, 11:11 AM
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Re: tranny coolers...
I used to have an tranny intank cooler in the rad, but pulled it out of the rad to lessen some of the overall cooling load, and to increase tank capacity. To supplement the cooling loss, I added a second B&M cooler. (I used to run an large aux cooler that sat under the frame on the passenger side, and ran a fan with it. Look closely below the pass door
It wasn't quite up to snuff during stop and go driving, so I added a second unit in front of it. That helped a lot, but having room restrictions I could only use one fan. Last year I decided to move the smaller of the coolers in front of the rad to sit directly airflow path. Tranny temps are very stable now. If I'm sitting in heavy traffic, I can throw the rad fan on high. works like a charm)

Because of how tight things are I have no room behind the rad for a cooler. Fan - intercooler with shroud - crank mounted intercooler fan. No room between the bumper/grille/rad to mount another cooler. Unable to use a standoff because of the bumper. The only other option is to mount another B&M cooler on the driver side. I'm just worried about the extra load I would put on the oil pump having it so far away. I'm not too keen on having a wheel well mounted cooler.

Rad is mounted above the highest engine water jacket point, so I'm ok there.

"without excellent shrouding your fans are just re-circulating a lot of hot engine
compartment air"
Fan is shrouded well, but I still think if I can cause negative pressure (or at last a balance) in the engine compartment during Hwy cruising it will help to get more air through the rad.
I'll take some pics today so you can get a better idea of what I'm dealing with.


Thought about the lower hose, Had to make custom setup to fit. It is made up of pieces of 2" copper pipe and short lengths of rubber hoses. (no collapse possible)
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  #23 (permalink)  
Old 06-27-2008, 11:48 AM
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Might need louvered hood to let air out. But it is visible.
I did some louver tests and found that depending on the speed the air might be coming out of the louvers, or going in. Going in at highway speeds is good, it means that there is sufficient vacuum under the car to suck heat out of the engine compartment, although it might lessen the airflow through the radiator. Louvers also reduce heat soak.

Definitely air dams and good core support seals.
Be sure the TOP of the core support seals to the hood.

What type of coolant are you running?
50/50 glycol water mix cools much less than straight water. Consider a test with 20/80 or even 10/90.

Consider Evans Coolant. It works.

It is possible that the water core of the engine has a lot of rust in it. Rust is an insulator.

A radical consideration would be run the heater hose to a remote radiator in the rear of the car. But watch your pump rpm. If you have a heater, try running the heater full blast when the engine gets hot and see if additional radiator area might help.
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Old 06-27-2008, 12:01 PM
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Quote:
Originally Posted by quick72toy
LOL Yeah, she's pretty tight in there. The funny thing is, I have more room to change my plugs than the factory Buick does.

Thanks for the ideas.
Can't do the air dam because the intercooler scoop sits there.
I guess i could pop the hood and put in some sort of safety latch, but I'd like to find another way to get the air out.
The 3" tubes would fit from below. They would go up between the block and frame rails and end just below the headers.
I'm just trying to figure out what angle I should cut the bottom end at.
Aerodynamically you want the back cut 30% to the relative airflow, IF the pipes are sufficiently long.
BUT, the question is, what IS the relative airflow direction among all that chaotic air under the car?
Air doesn't necessarily go the direction it looks like it would go. (just like in head ports)
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Old 06-27-2008, 12:17 PM
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POST 17

Quote:
Originally Posted by quick72toy

, I am running a undersized rad for the engine.

but I no doubt it is under capacity. The Ford Taurus 2 spd fan (will pull small animals to the front of the car when on high LOL ) makes a huge difference,
and running RMI-25 (form of water wetter) and distilled H2O has dropped the temps.


Just to be clear the car does not radically overheat, I just notice that the temp is a bit higher than normal and the fan stays on.

but if I cruise at a higher rate of speed temps will climb a bit.
.
I apologize. I caught your coolant description this time.

What is "a bit higher than normal"? Running a constant 220 on the highway would not be a problem. If it continues to climb, and never levels off, then you have a problem.

Consider the Evans coolant. It won't boil until 360* and runs only 3 psi radiator cap. http://www.evanscooling.com/main21.htm
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  #26 (permalink)  
Old 06-27-2008, 10:36 PM
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I have smallish factoryhood louveres, and I imagine they are helping some. I am now working on sealing up the rad, and making sure all the air I can get is directed towards it.
Thanks for the info on the backcut. I'm not sure how the airflow is undernearh the car, i guess it wiil be trial and error with the tubes.
To be honest I guess I really don't have a big problem temp wise. She may hit 185 on a hot day, but the GN setup runs best with a 160 deg stat. I know, I know, before you all start jumping all over me This is standard practice for almost all performance GN's. It is one of the first mods that is done. Lower the temp, and you can run higher boost and timing.
I'm also concerned about intercooler heat soak saturation, so if I can drop the underhood temps it is bound to help.
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Old 06-28-2008, 07:31 AM
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first,
a 160* stat does not lower normal/balanced operating temp at all...
it simply changes how warm does the coolant get in the motor till the the stat does open....
as soon as the "wax" temp inside the stat is melted to the point that it can't hold back the spring the stat is open and the motor will continue to get hotter till the gpm thru the rad stabilizes it....
in your case 185* is where the radiator btu cooling capability balances the the btu's generated by the motor with warm ambient air temp (excellent!!!)

second,
you definitely don't want to put many miles on a motor at only 160*....
it's too cold and signifigantly impacts cylinder wall wear and motor wear....
do note on the attached wall wear/temp graph it is "only" a 60 hour test duration!

third
the reason the stat is there to begin with (and needed!) is to get the block and rotating assembly up to 180*+ temp as fast as possible/least amount of miles possible for less wear....

fourth
blink your eyes really quick once....
that's approx .1 second
if you could get your normal/average temp down to 160 for cooler heads to tolerate more boost your car might be 2 blinks max quicker in the qtr....
that's not a performance difference you can feel or even be aware of....
it just shows a difference on a ET slip....
there are 100's of good "tricks" to make a car quicker and faster by .1-.2 seconds that DON'T ruin the motor!

ps: "if" you drove your car as is when the ambient air temp was around 32*...it will likely balance at 160 and good chance even lower (bad for the motor!)....
put a 180 or 190* stat in it so you can drive it in cooler weather!

pps: to get your motor to operate at a 160* balance temp on a warm day will require atleast roughly a 50% bigger radiator...
when there is way way more rad coolant btu's transfer than motor prduced btu's it causes the stat to repeatedly open and close due to way cold coolant comng from radiator so the temp stays around 160....

your goal should be 185* constantly at any speed driving normal on a warm day....
pretty good chance that changing your tune up settings just a hair will do that....
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Old 06-28-2008, 10:24 AM
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Quote:
Originally Posted by quick72toy
I have smallish factoryhood louveres, and I imagine they are helping some. I am now working on sealing up the rad, and making sure all the air I can get is directed towards it.
Thanks for the info on the backcut. I'm not sure how the airflow is undernearh the car, i guess it wiil be trial and error with the tubes.
To be honest I guess I really don't have a big problem temp wise. She may hit 185 on a hot day, but the GN setup runs best with a 160 deg stat. I know, I know, before you all start jumping all over me This is standard practice for almost all performance GN's. It is one of the first mods that is done. Lower the temp, and you can run higher boost and timing.
I'm also concerned about intercooler heat soak saturation, so if I can drop the underhood temps it is bound to help.
I love your car. Bravo !!!!!!!

I suggest the Evans Coolant. It will cost $100 but I bet it will drop your temp.
It cannot hurt, and I believe it will help.

Definitely work on all your airflow seals, especially that core support to hood seal.

My guess is that you are wasting your time with the tubes, because airflow direction through the engine compartment will change at different road speeds so you might be "tuning" for one speed only. The tubes will have to hang down so low for consistent operation that clearance will be a problem.

One other thing that would help is a big air dam and side skirts, like the IROC Dodges used to run. But they are noticeable and fugly.
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Old 06-28-2008, 11:05 AM
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Your car front end design tends to push air under the car rather than over or around. It needs an air dam, I know that might be difficult in your situation.
Here's what I would do.
I would get some yarn, cut lengths to about 2 1/2" and tape yarn to the hood louvers and about 6" apart all along the side and rear of the hood edges.

Drive the car and watch the yarn. See if the air is coming out or going in. I will probably change from out to in with the increasing relative wind. (actual speed of the air over the hood changes with headwind, etc.)

The windshield develops high pressure and the yarn will probably go in over about 60 mph. Watch your louvers, that is important. If the yarn is sucking in when you start having higher coolant temps, then work toward sealing the hood edges.
You have 2 situations. For handling you don't want high pressure under the hood and neither for cooling. So blowing air up through the louvers is reducing the hood lift. If the yarn is sucking down, then the louvers need to be sealed for more radiator airflow, reducing front end lift.
Developing more under hood suction will probably require a front air dam of some sort and sealing all around the hood.

Last edited by ScoTFrenzel; 06-28-2008 at 11:11 AM.
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Old 06-28-2008, 12:36 PM
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red65mustang
I'm going to disagree with some of that article.
http://www.carnut.com/ramblin/cool3.html
The purpose of the stat is to regulate operating temperatures (" an automatic device for regulating temperature") it is a control device.
The wording below is a bit contradictory.
"a 160* stat does not lower normal/balanced operating temp at all...
it simply changes how warm does the coolant get in the motor till the the stat does open...."
Isn't that controlling the operating temps? I says it in the last line. I'm not wanting to argue semantics here, but in my books basically it helps control engine operating temp.
Normal temp day, city cruising, my temps stay close to the 160 range, with the fan cycling off and on as required. (cycle range is programmed into the chip)
If I put a 180 deg stat in, the temps sit in the 180 deg range. Yes, rad capacity, flow, heat saturation, come into play, but that is not really the point. If stats dont really help control operating temps, why do they have different ratings?
I'll leave this one alone, as this discussion could go on for pages :-)

Cylinder wall and motor wear...
I have been running different variations of this combo for 12 years and every time the motor has been in to the machine shop for a freshen up, (rings, bearings, etc) I ask the machinist if anything has caught his eye, or looks out of the ordinary, and the machinist comments on how little wear there is, for the amount of miles. Granted this isn't a ultra high mile, hard driven car, but it isn't a garage or trailer Queen either. It does go to the track, and often sees 24 psi of boost.
I talked to quite a few other GN owners running 160 deg stats, (some who have had their cars since new (86) ) and they report no abnormal engine wear.
The jury is still out on this one for me.

There is a much greater difference in measured performance, going from 180 to 160 deg operating temps. Much more than 0.1. I do not have any back to back time slips show 180 vs 160 times but, the butt dyno speaks loudly here. It is something you can feel. Granted, part of the byproduct of this is cooler intake air temps, and density of the air, etc... but overall lower operating temps help with detonation. These cars (GN's) are a very funny beast and don't really like the heat. Numerous post have been written on the different Turbobuick boards, about how the car performs much better on a cooler night.

I do appreciate the input, and love to stir up the grey matter. Always willing to listen to other opinions.

Thanks for the kind words ScotFrenzell
As I mentioned in a earlier post, it isn't a horrible problem, I just want to see if I can bring the under-hood temps down a bit. It won't hurt. This discussion has opened up my eyes to better airflow and rad sealing. I'm a tinkerer by nature, and like the challenge of doing something different. (hence the car LOL) This is just another improvement project. (The list is always growing and shrinking)
I do appreciate the input and ideas. I steal what works for me and try to incorporate some of the theories, without any visual modifications.
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