TF running hotter on highway than in-town.

[roger55]

Originally Posted by diceman50

They should serve the same purpose as the vents by eliminating the stagnant airflow in the corners. Also, I found the Spal 4 inch fans on Amazon for $40 each.

http://www.amazon.com/gp/offer-listi...&condition=new

For a similar price, I could get this:

http://www.code510.com/high-performa...-2950-cfm.html

The cfm rating is impressive but something doesn't seem right. It draws 10.5 amps and the 16" I've got draws 18 amps.

[paulspickupparts]

Just to throw this out there. I used to have a 1 ton Dually car hauler. Small block with auto tranny and a/c . The tranny fluid also circulated and cooled through the radiator like yours. I could literally watch my temp gauge go up as I pulled the engine harder. The extra heat in the tranny fluid would raise the temp of the water in the radiator. I especially noticed it when I would pull a steep hill or worse yet a trip over the mountains. When I coasted down the other side of the hill the water temp would drop back to themostat temp plus a few degrees. I never did it but was advised to not use the radiator to cool the trans and install a remote cooler for the transmission.

You tranny will generate more heat when running at highway speeds than puttin around town. This is sometimes a problem with hot rod engines running high stalls which will also run hotter. Not saying this is your problem but usually highway speeds help lower that high under hood temp. Would be interesting to know what your tranny temps are in different situations.

You do have a rather large a/c condenser but if it is not getting hot around town I do not think that will affect your highway temp. I believe you said you had the air off.

Good luck. I will follow this and hopefully see the problem solved.

[roger55]

All my highway testing was with the air on. 210 after 10 miles.

I did both ways for in-town testing. 192-196 air on and 190 off but the fan cycles at that so it's possible it would even go cooler with the A/C off if the fan would stay going.

All tests were at 95 ambient give or take a degree or two.

You wouldn't think my unloaded truck on relatively flat highway going 65 mph at 2000 rpm would put much heat stress on the radiator with the 700R4.

[Speedbumpauto]

I deliberately left the tranny cooler function out of my rad. figuring it would have enough problems. Added a B&M cooler with a fan under the bed between the frame rails. I don't like the plastic flaps either and was toying with the idea of stainless piano hinge and thin polished aluminum for the flaps. Right or wrong I spend a fair amount of time considering looks too.

[paulspickupparts]

Originally Posted by roger55

All my highway testing was with the air on. 210 after 10 miles.

I did both ways for in-town testing. 192-196 air on and 190 off but the fan cycles at that so it's possible it would even go cooler with the A/C off if the fan would stay going.

All tests were at 95 ambient give or take a degree or two.

You wouldn't think my unloaded truck on relatively flat highway going 65 mph at 2000 rpm would put much heat stress on the radiator with the 700R4.

Sorry for not reading you original post thoroughly .

If you are running 192-196 air on and 190 off you have a very good cooling system. The reason I say this is that I believe you stated your fan does not kick on until 190 . So for your engine to run at the above temps in 95 degree outside air temperature is very good . I will say that your thermostat which is 180 is doing very little other than bringing your engine up to operating temp more quickly. Your fan switch set at 190 has become your engine thermostat. Would be interesting to see what temps would be with the fan on all the time (that would be easy to do as a temporary test)

My question is what is your engine temp after 10 miles on the highway with the air conditioning off?

I agree that you would not think your tranny would cause this . Just trying to see what changed from your city driving to highway driving which is causing a rise in engine temp. First thing I would do is take it for a drive on the highway without the air on. Hopefully you can duplicate that 95 outside air temp. Driving on a 70 degree day will skew the test.

[mr48chev]

Actually 210 with the air on after a ten mile run isn't even considered hot if the engine were in the rig it came out of in the first place. That's called operating temp.

I can never figure out why guys get out of their late model dailies that operate at 200 to 220 degrees on the norm and then pee their pants when their hot rod gets a tad over 190 or even up to 190 with the same engine that they have in their late model.

The problem here is that what is happening isn't normal and the engine temp should drop out on the highway at 70 mph by all known standards. If it spiked up really high I'd say you had the wrong rotation on the water pump but unless someone made a serious mistake that shouldn't be the issue. That leaves air flow. If you had easy access to the highway you could pull the fan and shroud off the truck and bop out and hit the road and see where the temp runs and go from there.

[roger55]

Originally Posted by mr48chev

Actually 210 with the air on after a ten mile run isn't even considered hot if the engine were in the rig it came out of in the first place. That's called operating temp.

I can never figure out why guys get out of their late model dailies that operate at 200 to 220 degrees on the norm and then pee their pants when their hot rod gets a tad over 190 or even up to 190 with the same engine that they have in their late model.

The problem here is that what is happening isn't normal and the engine temp should drop out on the highway at 70 mph by all known standards. If it spiked up really high I'd say you had the wrong rotation on the water pump but unless someone made a serious mistake that shouldn't be the issue. That leaves air flow. If you had easy access to the highway you could pull the fan and shroud off the truck and bop out and hit the road and see where the temp runs and go from there.

I agree with you with the first part of this post. If 210 was as hot as it would ever get on the highway, I'd be fine.
But, it was 95 out and it was flat highway.
I want to have the capability to drive this truck in worse conditions than that.
On a hot summer 110 degree day and running one of those extended 4% grades you can get in places even on interstate, I'm afraid I could be at over 225 with the way the truck is now. Even though that wouldn't damage it, I just don't plain want it to run that hot. I may lose some coolant at that temperature too.
Even if I do figure out and solve issues of why it runs hotter on the highway that in-town, I think it still may run 210 to 215 on a 110 degree day in stop and go traffic. That's not horrible but still warmer than I would prefer.

I would feel much better if I had numbers like 205 around town in the worst of conditions and 200 on the highway in the worst of conditions. I want some breathing room between the hottest actuals and running too hot for me.

[Hampshire]

You've probably heard this before, but my sister in law (who lives in the greater Houston area) always remarks that the three types of weather there are "Hot, Hotter & Hottest"

....so, from my many visits, I can understand the need (and the challenge) in building in that extra margin of safety. You do have a lot of variables to consider. Hopefully a simple solution will emerge...

[1project2many]

Some thoughts:

1) Airflow through the radiator is typically be much greater when moving with electric fan off than with the fan on & vehicle stopped. Typically the fan shroud on an electric fan is only as large in diameter as the fan and will extend to the radiator. The remainder of the radiator will be open to allow air to flow through the radiator. Your setup is likely to build pressure around the outside of the fan and prevent airflow in the corners of the radiator. Without the ability to transfer heat energy from engine coolant to air (or another medium), a radiator of any size will not be effective.


2) Although the aftermarket companies say otherwise, I have had consistently better results using OEM cooling fans than aftermarket versions for vehicles. Larger OEM electric fans include the 17" early '90s Camaro fan and the early '90s 3.8 Taurus fan at (IIRC) 23". The Taurus fan is two speed with advertised ariflow of 2500 and 4500 CFM. I have a BMW fan and shroud from about 2005 or so that has those very cool "flaps" that open when airflow through the radiator increases.

The effective (but not as sexy) Taurus fan:


3) Some of our school buses have rear A/C systems with relatively small condensers underneath. If the fans on these units are not at their best, the a/c is noticeably warm. I have seen a huge difference in cooling ability between those shallow angle aftermarket fans and the OEM designed replacements. The best fans have a shroud built around the fan blade and the difference in airflow is amazing. Have you checked temperature difference between inlet and outlet of the condenser? Is your condenser doing such a great job of cooling the cab that it's heating the engine as well?

"Good" A/C condenser fan:


4) Engine compartments often have less pressure differential when moving than we expect. There can be a benefit from installing an air dam or other device to create low pressure immediately behind the radiator. I wouldn't consider this a next step but I'd keep it on the list of things to try if all else fails.

5) I will list my fan and vehicle specs if interested but there are enough differences between our locations and vehicle that I'm not sure it's relevant. It is a pusher setup because there is less than 1" clearance between the water pump and radiator.

I prefer to use the ecm for fan control. Often with the 180 'stat I find turning the fan on at a lower temperature reduces average operating temperature. Both on and off temperatures are adjustable and I've found over the years the minimum hysteresis works best if it's no less than 5 degrees F. There is also a maximum speed for fan operation which can be adjusted so the fan will stay on when running even if the A/C is off. Other factors in the tune can play a part in engine temp as well. Have you deleted EGR? Is the timing set to OE specs? Any chance you have engine oil temp readings?

[roger55]

Thanks for taking the time to post all that info for me!

Answering your questions first.
Yes the EGR is disabled in the ECU.
No, I don't have the oil temperature.
Yes, the time is set to OE specs at 6 BTC. See that printout from my software for everything else. At 2000 rpm it looks like 36 to 38 total advance while running at 65 on the highway.
Yes, my A/C is incredibly cold. I haven't checked any temperature differentials across the condenser.

With all help I've gotten (this forum and the trifive.com site), I've come to the realization that with what I've done, I don't have any air flow from the grille area to the engine compartment that doesn't go through the condenser and radiator and that is not a good thing.
I've now removed all the tape and seals I put on there as I detailed in my photos. After I receive the high-flow thermostat and lower radiator hose spring this coming week, I intend to drive it and see how my temperatures compare to the last testing I did.

Looking at that Taurus fan that is 23X18, It appears that the actual fan size is 16" and the same as what I've got. I don't think the cfm for that would be any higher than what I've got either. I'm pretty skeptical of advertised cfms for fans. Mine draws 18 amps. I would think that Taurus one similar.

I think I would be in pretty much the same place I am now if I had that Taurus fan. If I put holes in the corners of my shroud, it would be the same as the open area of the core that would be left with a small shroud like the Taurus one has.

Earlier today I thought about trying to go with a mechanical fan because they are large. But, the only way I could do that is without a shroud at all. I can't fit any type of tapered shroud because of how I built my cold air intake pipe. I'm not willing to go without a shroud at all so I won't even be trying that.

[mr48chev]

The fan cools it down sitting or at low speeds to where most of us would be turning cart wheels so I don't think you will do much better fan wise.

[Clarance J]

Hello Roger55. How about getting a different temp switch that turns the fan on at a lower temp. The one I have is on at 185 and off at 170. Just another idea to ponder. Great looking truck you've built.

Earl

[roger55]

Originally Posted by Clarance J

Hello Roger55. How about getting a different temp switch that turns the fan on at a lower temp. The one I have is on at 185 and off at 170. Just another idea to ponder. Great looking truck you've built.
Earl

I'm not totally happy with the switch I have but it doesn't have anything to do with my issues.

Mine switches on at 190 and that's OK but it switches off at what must me 189.5 so the fan cycles more than I'd like. I only see it do that with the A/C off.

With the A/C on and the engine warmed up, it stays above 190 and the fan continuously runs. Same as it would do with the switch you have and why it isn't part of the issue I'm dealing with.

Your switch won't work with a 180 thermostat as the fan would fight with it and never turn off. I have to run a 180 thermostat because my TPI ECU would command too fast of an idle speed if it ran under cooler than that. It probably could be reprogrammed but it still doesn't have anything to do with my issue so the only thing it would do is make it take a little longer to get to the temperatures that I'm reporting.

[yossarian19]

Running hot at highway speeds isn't likely to be an airflow issue. I'd look at your water pump.
Running hot around town, sure, all the above suggestions about removing airflow restriction makes sense - but if you are shedding enough heat just puttering around town with no airspeed across the front of the vehicle, you darn sure have enough airflow at 70 mph. What you haven't got is coolant flow through the radiator.

[roger55]

Originally Posted by yossarian19

Running hot at highway speeds isn't likely to be an airflow issue. I'd look at your water pump.
Running hot around town, sure, all the above suggestions about removing airflow restriction makes sense - but if you are shedding enough heat just puttering around town with no airspeed across the front of the vehicle, you darn sure have enough airflow at 70 mph. What you haven't got is coolant flow through the radiator.

I was in this camp at the beginning of thinking about this.

But, I have been convinced otherwise by the help I've gotten here and on the trifive.com site.

On the highway, the engine is generating more heat because it's running at a higher rpm.
With what I've done, I have no openings for air at the front of the truck other than what has to go through the condenser and radiator and the 16" hole in the shroud. And that's causing more heat in the engine and compartment and it's working against the cooling system. So basically, the highway speeds aren't able to make virtually any more air to go through the radiator or the engine compartment than does when sitting still.

I didn't believe this at first, but many have said it and the more I thought about it, the more sense it makes.

That said, I am making sure I don't have water flow issues. I've got a RobertShaw high-flow thermostat and a lower radiator hose spring on order. I will install those and re-test. I don't think those were issues but doing that for good measure. The water pump is a new not manufactured one. It's not the problem I'm sure. I've never even seen a water pump with a flow problem in the 40 years I've been in this hobby. I guess that doesn't mean it doesn't happen though.

[paulspickupparts]

I agree that the engine will generate more heat . It is working harder.

Same thing with the transmission. This keeps falling on deaf ears but it would be a really good idea to know your transmission temp fluids. The tranny is working a lot harder at highway speeds than in town. Because of your location and high ambient air temps that thing could get very hot. Will depend on converter, exhaust routing , air movement and type of transmision cooler. In your case the radiator trans cooler. If your tranny fluid is running hot it will make your engine run hot. Many people install a temp sensor in the tranny pan just to monitor it. If your tranny is running hot it will decrease the life of everything

If your engine is running hot it will make your transmission run hot. If your transmission is running hot your engine will run hot.

Add to that that big a/c condensor in front of the radiator. If that thing is hot you could have very hot air entering the radiator.

Really you have three things heating up your radiator. The engine , the transmission , and the a/c condensor.

I really hope you do a highway test without the air on after you get the truck back together. You can then eliminate one thing at a time in your truck instead of a keyboard.

[yossarian19]

Originally Posted by roger55

I've got a 305 TPI engine with a 180 Stant thermostat that I can verify that it does open at 180...The fan switch turns the fan on at 190 and I've verified that. The truck has Vintage Air A/C and all the testing I've done is with it turned on and the ambient temperature at 95 degrees.
After some extended in-town driving, the water temperature runs at 192-196. Getting on the highway and running at 65MPH (2000 rpm), it will warm up to 210 after about 10 miles. I Transitioning back to in-town driving, the temperature will come back down to 192-196.

These aren't damaging temperatures but what concerns me is a hotter day maybe up to 106-110 and pulling a highway grade. With what I've got, I have no room for the extra heat those things would do.

After a re-read...
Y'know, your truck is actually performing exactly as I would expect it to with a 180* thermostat. Hop in a new truck and drive it around town for five minutes. It comes up to 210*. Now hitch a trailer to it and drive balls-out up a highway grade. It's probably still at 210*. If you swap the t-stat for a 180* you'll only decrease operating temperatures under low load conditions - and it will still find it's sweet spot at 210 under high load.

If I was still an auto mechanic and somebody came in asking me to diagnose this, I'd tell them "operating as designed"

[roger55]

Originally Posted by yossarian19

After a re-read...
Y'know, your truck is actually performing exactly as I would expect it to with a 180* thermostat. Hop in a new truck and drive it around town for five minutes. It comes up to 210*. Now hitch a trailer to it and drive balls-out up a highway grade. It's probably still at 210*. If you swap the t-stat for a 180* you'll only decrease operating temperatures under low load conditions - and it will still find it's sweet spot at 210 under high load.

If I was still an auto mechanic and somebody came in asking me to diagnose this, I'd tell them "operating as designed"

New cars/trucks are designed to run that way and the temperature is controlled with the fan and not the thermostat.

New cars/trucks are designed to run that way and the temperature is controlled with the fan and not the thermostat.

My '55 Bel Air has a 180 thermostat.
With that one, I'm running a cross-flow radiator with dual 14" electric fans. Has A/C.
It never runs over 190 in any condition. I don't tow anything with it of course. But on grades at 105 out and it stays below 190. I'm controlling the temperature with the fans on that too and I could make it run even cooler if I wanted to but I don't want it to fight the 180 thermostat.

[tmoble]

What Paul said:

>> "You can then eliminate one thing at a time in your truck instead of a keyboard."

There's a lot to be said for this.

always remember, the t-stat sets the minimum temp, doesn't really have anything to do with the maximum.

[roger55]

Is there information out there that could help me make an estimate of how much additional temperature a 700R4 transmission adds to the water when an in-radiator cooler is used?

I wouldn't want to put the money into a remote cooler (with it's own fan) just to see what difference it makes. Obviously putting one without it's own fan in front of the radiator would defeat the purpose of taking the most load off the cooling system as possible.

[yossarian19]

Transmission fluid adds negligable amounts of heat to the coolant and may actually pull heat out of it under some conditions. Healthy operating temp for the auto transmissions I'm familiar with is ~160* to 180*. If coolant goes in to the hot side of the radiator at 210 or so, it's leaving at (give or take) 170-190*. With the transmission cooler in the cold side of the radiator... it's only adding heat to the coolant under pretty severe conditions.

It's also worth noting that on each and every factory automatic that the trans fluid runs through a radiator heat exchanger with an auxillary cooler plumbed in after the fact - usually only for tow package vehicles.

[1project2many]

Camaros and 'Vettes have such a low coefficient of drag that the timing tables often run a bit more advanced than what works best for a larger vehicle. Engine MAP on the highway is about 54 kPa in the data screen you posted. I'd expect to see this value a little lower although with A/C running it's not too unreasonable for a truck. I'd also expect to see low to mid 40 in a Camaro at the same speed.

It only takes a few degrees additional timing to bring coolant and oil temperature up considerably and EGR, when operating, counters the effects of excess advance slightly. I'd say that the displayed advance is a bit high for your application. TBI trucks, with similar design heads, often end up around 30-34 deg advanced in OE cals and they use EGR. If too much timing is causing a problem then decreasing base timing 2-4 degrees using the distributor should provide some improvement.

Do you happen to have the four letter code off the original ecm or the chip? I'm just curious to see if I have a copy of that file here to look at.

Hopefully this issue is as simple as needing more openings in the shroud.

[roger55]

It's a 1991 7730 speed density version. EGR programmed out.

[1project2many]

Thanks. GM actually released many different calibrations for that year and engine. They usually use a four letter code on the chip to identify which calibration is programmed in.


Not a big deal... you've got bigger fish to fry there.

[roger55]

Another guy told me he thought 36 to 38 degrees total advance sounded low but then thought it might be right since it was only at 2,000 rpm.
Anyway you are right, it's probably not in any kind of range that would cause a heat problem. Someone did say I should check the advance with a timing light to make sure I'm actually getting the amount of advance the ECU is commanding as it doesn't get feedback of any kind to tell me this in the readout.
I will do that but based on the fact the engine runs like a top, I don't expect it to be off.

Btw, I sent that chip to Larry's Electric and they programmed it to take the EGR out and disable the VATS. Not sure what else they usually do for swaps. I bought my harness from them too. I can get the chip number if you think it will be of help at all.

I wouldn't mind getting the gear it takes to program these. I also have a 83 El Camino SS with a 96 LT1 engine running controlled by a 94 ODB1 ECU. Both these vehicles are long-term holds for me and it would be nice to have programming capabilities for both.