Full throttle for 2mins 15 seconds - no overheat

Discussion in '80-Series Tech' started by IdahoDoug, Jun 27, 2005.

  1. IdahoDoug

    IdahoDoug

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    There was a thread recently discussing overheat issues with passes, etc and I added my data points heavy towing on the 93 - which shows no overheating pulling the boat on passes. As noted, it's been overmaintained by me as is likely very close to as new.

    We just returned this evening from Lake Roosevelt, towing the boat for the first time with the new to us 97. Leaving the lake, you have to go up a very long and steep hill (6.5% I think). The truck was already hot from pulling the boat out, climbing the lower portion before it gets full on steep, and running the A/C on an 85 degree day. When we got to this part, I hit the 2nd gear start button (to prevent a WOT downshift weighing 11,500lbs), floored it and noted the timer. Left the A/C at full blast. Kinda nervous because this truck is still new to me despite having gone through it quite thoroughly. No pinging whatsoever.

    At 1 minute into it, the truck had slowed from 32mph to 27 and was holding steady. At about 1 minute 30 seconds the truck had regained to 30mph. Still no ping and no temp needle movement, A/C still cranking at full blast. Finally, at 2 minutes, I think the needle moved but it was so little it was barely discernable. We hit the crest of the steep part 15 seconds later and the speed slowly climbed to 45 mph before the tranny shifted into 3rd (I'd turned off the 3nd start button). About a minute later, the oil pressure dropped a needle width for a minute or so and then returned to normal. That was it.

    Informationally, this 97 truck has 138k on it, fresh everything, Mobil 1 in the engine, and I've done two tranny drain/fills on what already appeared clean fluid since buying it 6000 miles ago. It's got a new Toyota 93/94 brass/copper radiator in it from Cdan as PM, and Toyota red. My wife filled it with Costco Premium.

    I'd have to say that this is about the harshest thing you can do to your drive train. Very few vehicles ever have their throttles floored for a full minute, but these things appear capable of handling it for several minutes as I've done longer WOT runs on the other many times.

    DougM
     
    Last edited: Jun 27, 2005
  2. TX_TLC

    TX_TLC

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    Too bad it isn't a pre-95...you would already have had the good radiator and the built-in stop watch! ;)

    Very nice description...and data point.
     
  3. Beowulf

    Beowulf

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    It sounds like you've got your '97 running very well. Keep in mind though, the stock coolant temp gauge is extremely "flat" through a wide temp range. Basically, it doesn't start moving off of "normal" (one needle-width below mid guage) until the coolant temp is approaching 226.

    I have a Greddy that is linear and the OEM gauge never moves from "normal" while the actual temp, measured by the Greddy, fluctuates a large amount.

    -B-
     
  4. Rich

    Rich

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    The real test would be to repeat the tow in 115 - 120 degree heat. The two times my AC cut off activated the outside temps were 115 and 120 degrees. I don't suppose most folks get the opportunity to enjoy such weather in North America outside of the southwest.
     
    Last edited: Jun 27, 2005
  5. Dusty

    Dusty

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    sounds like your rig is a goodun
    I agree with above comment, my electrig guage shows 220 when the oem guage is just barely above middle (hardly discernable if at all). if I went by the oem guage I could say my rig never gets hot. But...the AC doesn't lie, I've had the AC cut out a few times running verry hard up long passes (as shared in my post) and these ocasions were all with >100 degrees outside. I think It's safe to say that if your ac stayed on your rig aint too hot. (especially if you run synthetic oil)
     
  6. IdahoDoug

    IdahoDoug

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    I've not done the actual testing, but are you guys aware that it's common for the better automakers to actually hook up a trailer and go do destructive testing on hot SouthWestern mountain passes to test cooling systems? Of course the cooling capacity is designed using accepted heat transfer standards but before starting to build vehicles, they actually hook up a trailer on several prototypes and go out to AZ as part of the hot weather testing protocol and floor it up grades over and over again until stuff starts to break. It's the real world data that matters in the end, and top notch auto engineers know that the theory only gets them in the ball park, where the real world data is essential to prove it before someone signs off on it.

    My brother in law (not part of the 80 community - sorry it gets so confusing as I have 2 of them, plus 3 brothers) has been part of this actual testing and reports that it's awful to watch as a car guy. Intriguing at the same time - kinda like not being able to take your eyes off a car wreck.

    Anyhow, I can tell you the 80 has been subject to a double dose of hot weather testing because arid dusty offroad applications are one of the LandCruiser's stocks in trade. A healthy 80 will thrive in extreme heat where competitors wilt.

    I mention this because I have long held the position that those with cooling issues likely have SOME underlying issue that is the real problem. Due to a previous owner mixing coolant types, it may have a drift of precipitates in the radiator or block. An older hose may partly collapse at high RPMs, restricting coolant flow. Scale on the radiator passages happens almost no matter how well a system is maintained and these tiny passages can easily lose 10% of their flow potential from not only the physically smaller aperture, but also the turbulence these rough deposits cause vs smooth metal. Accumulation of dust/road grime film on the radiator fins also reduces the important air - to - fins heat transfer. A couple years ago I achieved a large cooling improvement on the A/C of my clean low mile Subaru simply by soaking the radiator and A/C condenser fins in Simple Green and thoroughly rinsing. Measured at the dash vents it was something like 15 degrees IIRC.

    I agree with Dusty and Rich that higher ambient temps will place a greater yet load on the cooling system. However I cannot imagine that 30 degrees higher ambient temps like a 115 degree AZ day would put as much a load on the cooling system as having a 1FZ pull 11,500 lbs up a hill at full throttle and low vehicle speed (poor airflow). In other words, I *think* what I'm doing is harder on the truck than blasting up a pass with the truck alone (unless you guys are also at WOT all the way).

    This thread caused me to call my bro in law and ask him a couple questions:

    1 - Starting with an already hot towing engine, then going to full throttle and not gaining speed - how long before the engine's temperature peaks?

    2 - If an engine is X temperature (say 230F) at 85 degrees ambient, would it be pretty much 30 degrees hotter at 115 degrees ambient? Or hotter?

    He's going to get back to me on these and I'll share the answers. I think it's important to know that the margins of extreme demands is where little problems like those mentioned above will come into play. And if your cooling system isn't performing up to your expectations, then I feel its incumbent upon you to take a few more steps to assure your cooling system's capabilities are as close to they were when the truck was new. I'm 100% confident that my 97's is (new OEM radiator, new hoses, cooling system flush, fresh Toyota coolant/thermostat). And sure enough, I can apparently abuse it without overheating.

    DougM
     
  7. Rich

    Rich

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    Doug,

    I was suggesting that the same test, same load, be repeated at higher ambient temps if your objective is to compare your cooling system performance to that of others who have experienced the AC high temp cut off. Success at 85 degrees does not guarantee success at 120 degrees.

    All that really matters is vehicle speed, ambient temp, and engine load. Whether the engine load is achieved by towing on a moderate incline or not towing but on an extreme incline doesn't matter, as long as the same speeds and engine load are obtained.

    There are no set answers to either question 1 or 2. The answers depend on the total heat transfer capacity of the cooling system, other dynamic variables, such as actual vehicle speed, while under test. If the cooling system, at a particular load, speed, and ambient temperature is operating at max capacity, then an increase in ambient temperature is definitely going to result in an increase in engine temps. On the other hand, if, at a particular load and ambient temperature the system still has unused capacity to reject heat, then an increase in ambient temps may not necessarily result in higher engine temps.

    I fully expect that high mileage radiators are less efficient, due to both external debris and internal scale and corrosion, than new. I'm also guessing that the stock fan clutches either don't hold up very well or were perhaps speced a bit on the weak side to start with, given how many have reported cooling system performance improvements after replacing.
     
  8. IdahoDoug

    IdahoDoug

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    Rich,

    Yeah, there are a lot of variables at work on these two questions. However, I'm expecting an answer like the following:


    "Doug, I checked the data base on all the vehicles we did the hot weather test on, and according to the temp data all engines at full throttle peaked their water jacket temps before 8 minutes, though one went to 9 and a full size F350 big block managed to hold off until 12 minutes."

    And for question 2:

    "Doug, I checked the data base on all the hot weather tests vs ambient temps and it looks like when the ambient temp was 8 degrees hotter the engine temp peaked almost exactly 8 degrees higher."


    On the fan clutch, I'm planning to get one of the newer blue ones myself for the 93. However, it's never had any cooling issues despite some pretty serious pulling. I pulled a 9000lb trailer from LA to Idaho in late June and wish that I'd paid attention to how heavy I was on the throttle and for how long. Some of those passes in and near Oregon on the 5 were pretty gnarly. This same rig is on the original fan clutch and I'll have to do a search but I know I've had it at full throttle for longer, and on hotter days with no issues. Not one to tempt fate, I'm going to replace it as even though the airbagged (SRS) 97 will now take over family vacation towing duties I'd like the 93 to remain at full capacity as well. These can't be too expensive from Cdan, eh? Anyone know?

    DougM
     
  9. hobbes

    hobbes SILVER Star

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    I still wish someone smarter than me would come up with a way to make the stock temp gauge more accurate, a la the Supra modification. I remember talk of it awhile ago, but I don't suppose anyone here is trying, are they?
     
  10. turbocruiser

    turbocruiser SILVER Star

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    I'll echo Beo that this test, although well documented and well done is kinda like flashing in front of blind people; no one knows what they did, or did not, see.

    I can assure you that the stock gauge is complete crap and is designed to deceive. I can also assure you that except for the fact that the AC did not cut out, the ONLY thing you can say for sure is that your rig never reached 226 farenheit or higher. Other than that you could have been 225 degrees, 200 degrees or even 100 degrees for that matter.

    A real world test with a real world gauge: I have been praticing passes on Pikes Peak up to about the 12.5k foot elevation here off and on since I got the gauge to tell the temps. So far after accelerating super hard, between WOT and 2/3rds WOT (rooster tails coming off all four tires around each and every corner) for up to a minute and a half my gauge has gone to about 98 celsius several times. Once it was within the 98 - 100 range right in the middle of the marks.

    What does this mean compared to your truck with a 12k pound boat, well, absolutely nothing!!! So, what's the point, well, that was the point; unless you have an accurate aftermarket gauge you have no idea what your rig, or any other rig is doing. Refer to the thread below and install an accurate aftermarket gauge and run this rig through this test again and then the data will be, well, data. Meanwhile, happy wheeling, happy wrenching, happy boating and happy slower speed towing!!! :cheers:


    https://forum.ih8mud.com/showthread.php?t=27705&page=1&pp=30&highlight=aluminum+radiator
     
  11. Dusty

    Dusty

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    Dough
    after my recent post i ordered and installed one of the new blue fan clutches from cdan for a mere 108$ (thanks dan-what a guy). I havn't had an oportunity yet to drive a long, hot pass to test out the clutch but i can say my motor makes a louder blowing/fanning noise when idling.
    The few times my AC cut out it was >100 degrees outside, my AC was on and my 1fzfe was WOT with the pedel to the floor for many minutes. I don't believe my radiator is in as good shape as it was new but I'm resisting getting a new one for now as the one in my rig works fine 99.9% of the time and my wife might love me less if I got a new one without proof that we need it. (she has learned to watch the digital guage and knows the engine isn't getting hot-damn guage)
    I'm not yet totally convinced that an unmodified 80 in perfect running order is overheat proof though I believe there are some on this forum who feel this is the case and their opinion carries, with good reason, much greater weight than mine as they have had much more experience with this machine than myself. I suppose my lack of faith may stem from a belief, whether real or immagined, that few out there realy run their rigs hard at WOT as I do and therefore have not explored the limits of their cooling systems. On the other hand, I dare not dismiss the notion that perhaps my narsasistic (and poorely spelled) stance may indeed be rooted in some sort of sick and perverted denial, which, if being the case, may my cruiser explode in an overheated briliance and burn itself to hell.
     
  12. RavenTai

    RavenTai

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    Could you post a link to the supra mod?

    I have seen the miata mod, both my 96's and the miata gages are made by yazaki meter and they are similar but there are enough differences that the miata mod will not transfer over directly, it would need some tweaking/ testing. As far as I know nobody is working on the mod. I think it was Rich that measured the response of the thermister at different temperatures. I pulled out the gage and took pictures and made a schematic, but AFIK nobody has gone any further with it.

    Although my electronic skills are not EE grade I think I am proficient enough to come up with this mod. I am pretty sure there are some other members here with the skills needed the stumbling block is having a loose tamp gage and thermister to work with.

    Anybody have a spare 95-97 cluster ( I assume 95-97 are the same/similar enough? ) they could pull the temp gage out of?

    The stock gage does not have markings through most of the range so even after mod you would not be able to tell exactly what temperate you are running this makes it somewhat inferior to an aftermarket gage, a fixed stock gage does have one advantage it is already there and well blended into the dash, with a fixed gage you would get needle movement with temperature change and be able to tell when you are approaching an overheat witch is all I really want anyway.


    the pics I took were lost when I lost my server so I will repost them here.

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    originally from thsi thread

    https://forum.ih8mud.com/showthread.php?t=27705
     
    Last edited: Jun 28, 2005
  13. turbocruiser

    turbocruiser SILVER Star

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    Not that I'm smarter than anyone but this is likely the simplest way to work the stock gauge into something accurate. FYI, this controller will easily fit in the ashtray ( I have the same sized same shaped unit as a turbo-timer snuggly fit into the ashtray so that when you pull the ashtray out the unit pops up). Despite my aftermarket greddy gauge, I may still add this controller to both control another auxilliary fan as well as get whatever info the stock sensor gets at its location. HTH. :cheers:


    http://www.hksusa.com/products/more.asp?id=1697
    TurboTimer.JPG
     
  14. CruisinGA

    CruisinGA

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    I regularly run my barely maintained F engine at WOT for several hours at a time... at redline/70 mph... towing a trailer

    Its also 23 years older. :D


    As much as I like 80's, the 40 is my favorite. :D
     
  15. Dusty

    Dusty

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    Yea, but that old 2f makes as much power as a civic. low power=low heat production=easier to cool. Now take a hemi fighting 1fzfe and you are making some reeaal power.
     
  16. hobbes

    hobbes SILVER Star

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    Sorry Raven, it was your comments (and the Miata) I was thinking of. I googled it this AM and see there is stuff for the RX-7 out there as well.

    As far as the markings, would not a OBDII diagnostic tool give you an accurate reading? You could then just "add" an important tic mark (like where the A/C shuts off).
     
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