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Old 12-01-2009, 10:03 AM   #1 (permalink)
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Exclamation Too much grill block

Yesterday I had to drive from the Denver area up to Leadville and back. This includes going from 5280 ft to 11,013 at the Eisenhower Tunnel, back down to 8780 at Silverthorne, back up to 11,300 at Fremont pass, and finally down to 10,200 in Leadville. A few long steep climbs, and from Denver to the tunnel is pretty much straight uphill.

I put together exterior grill blocks for the upper and lower grill openings in the Town & Country van, hoping that I would get enough air in the small middle openings. This was OK around Denver, though I did hear the fan more often. The ambient temp was in the mid 60s.

As I started the climb out of Denver the temp kept climbing to the point that I pulled over to rip out the bottom block, because I didn't want to have it overheat. It came down a notch as I pulled back out on the highway, and stayed there till the road leveled out for a bit and the temp came back into the normal range, and for the rest of the climb stayed just a tick above where it usually is, so I didn't have to mess with the top block.

These are just temporary cardboard blocks to see what would happen, and give me a better idea of what will work. I think the first setup would work fine around town, but when I get into the serious climbs, it becomes apparent that those holes in the front are there for a reason. I did have a load, but it wasn't up to the limit. When I came back down it was dark and the temp had come down into the 20s in the mountains, and into the 40s in Denver, and the engine temp was back down where it normally stays, and I had plenty of nice cabin heat.

I think what I'll do is build a block that I can Velcro into place, so I can remove it easily when I have a heavy load and a long climb. So the idea of a more permanent air dam/block is probably not in the works for this vehicle. It does have 188,000 miles on it, and I have to keep it alive.

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Old 12-01-2009, 11:41 AM   #2 (permalink)
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All bets are off for sizing a permanent grille block when you live in the mountains. You've got one size for the ascent, and another for the downhill leg!

Underlines the importance of keeping an eye on temperature if you're going to start getting away from the OEM setup.
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Old 12-01-2009, 11:56 AM   #3 (permalink)
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Do you have a scangauge to monitor actual coolant temps, or are you just using the guess gauge?
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Old 12-01-2009, 12:08 PM   #4 (permalink)
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Similar experience

thatguitarguy, I have a '90 Dodge Caravan in the fleet and I spent it's first several years in Colorado trying to keep it cool climbing the passes here. I added a higher performance electric fan, tried a cooler thermostat, went to a 2 row and finally a 3 row radiator. I drove slower while climbing and would occasionally turn the interior heat to high with the windows down to dump engine heat. Obviously no grill blocking on this vehicle.

However, on my VW Golf I have used upper grill blocks year round and some lower blocking for faster warm-ups in winter. I still need to open the lower blocks before climbing passes, even in sub-zero temps.
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The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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Old 12-01-2009, 12:50 PM   #5 (permalink)
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I think the idea of a grill block which is in several pieces which are easy to remove/install is the only way to go due to the fact that most of us drive in various traffic conditions and in different sesons throughout the year.

Another point here is to allow the highly modified cars we strive to build to be easily converted back their stock conditions for when someone (normal) has to use them. Some of the modifications such as the grill block, alternator cutout, etc... require little bit more attention to how the vehicle performs and continous monitoring of those parameters, (normal) people expect cars to behave (normally) when they operate them and it would be optimal if the econo modifications could be disabled so the vehicle does not sustain any damage due to (normal) people ignorance.
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Old 12-01-2009, 01:11 PM   #6 (permalink)
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Automatic Radiator Adjust

Some of the university students who design, build, and race SAE formula cars, have mentioned something that would help in this situation.

Consider that 1/3 of the engine heat goes to the radiator at what ever throttle position the engine is running at.

If you are pulling a large load up a pass in Colorado, and the engine is putting out 200 hp, then the radiator will need to dissipate 1/3 of that load, or 67 hp!! AND the hole for the radiator block needs to be sized accordingly.

Likewise if you are putting along on flat back roads, and only using 3 hp, then the radiator opening can be effectively closed-off completely.

The only way to safely do this, is provide an 'automatic' device that monitors this for you, or at least have a cable assisted damper or some sort.

Hope this helps, Jim.
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Old 12-01-2009, 03:04 PM   #7 (permalink)
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If the fan is running more you are kind of defeating the purpose of blocking in the first place.

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Old 12-01-2009, 05:00 PM   #8 (permalink)
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Correct. The fan should not really be coming on as it is only drawing power and using fuel. If it does it once or twice on an incline then it should be ok, as long as the temps aren't getting too high.
As it turns out, i have mine completely blocked now that the weather has turned bad. It gets close to 90c but i turn up the cabin heater a little and it stabilises. I drive a diesel and a small one at that so it generates very little heat the way i drive. If my wife drives it i have to remove the grille block. I should revisit that adjustable grille block some day.......

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Old 12-01-2009, 05:40 PM   #9 (permalink)
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This is why I was hesatant about grille blocks at first. I used to live in the foothills, and knew I needed all that air coming in to cool the motor. The "Towing a trailer through Death Valley with the AC on max" must have been thought up by flatlanders... lol

Come up to the hills once in a while. It's MUCH different.

I'll probably be pulling off some tape from the partial upper grille block I have when I take the trip back to California for Christmas. I'm not sure how it's going to be, since it's winter, and it'll be cold (and most likely snowy), but I'll be climbing up to 5,000 feet along with several 6% grades along the way.
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Old 12-01-2009, 05:42 PM   #10 (permalink)
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I don't have a scanguage, and I won't be getting one for this vehicle. It has a gauge and not a light, so actual temp is pretty irrelevant. Relative temp is what I need to know and I can tell from the "guess gauge" what is hot and what is too hot. It does have a trip computer that monitors average mpg and current mpg, and that's all I want for right now. It has helped me to change my driving style and eek out better than 27mpg average. It will never be a 60mpg hypermiler, but I am trying for 30mpg. But when I have 60-70 miles of pure uphill ahead of me I don't need redundant gauges telling me that I'm getting single digit mpg. I do work to keep it in the double digits, but it's not worth slowing down to 30 mph and becoming a hazard on the interstate in order to save a few pennies worth of gas. It's about balance. I did reset the computer before I left, and by the time I got to Leadville I had averaged 21.6 mpg on the way up. It may not sound very good, but for that much climbing, I felt pretty good about it. Of course it went way up on the downhill loop, and that is where the benefits of an exterior grill block come into play.

Before this 98, I had a 94 Caravan which was closer in design to the 90. It never overheated, but sometimes on those long climbs it would get up there. The 98 is a pretty modified design all the way around, and before this, I never saw the gauge get that high. I think stylistically the 98 T&C has a bigger open grill than the Caravan, but it is pretty easy to block.

Last edited by thatguitarguy; 12-01-2009 at 05:50 PM..
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