How do I drop my highway temp 8°?

[57vette]

Happy to note that I'm using Carl's PWM in my '69 Camaro 461 BBC. Its working exactly as advertised, I'm currently using a 195° sensor and a 180° thermostat. My radiator is a new Cold Case unit with two 1.250" tubes and I'm using a modified set of Ford Contour 12" fans on a custom designed and built aluminum shroud that's about 1" deep inside. When I'm out driving just after the temp gauge hits 195° the fans go on (I have a LED indicator on my dash).



I included a dozen BeCool rubber flaps in the shroud design to help overall airflow at highway speeds. Generally speaking, its working OK but I think I need more CFM because the car runs a bit warmer than I'd like. On a typical 85° summer day on the highway, I can't get it below 200° while driving at 65 mph. And the minute I'm driving on local streets the temp climbs to 210°-220°. The car now has Vintage Air so there's a almost full width Condenser in front of the radiator. I have the sneaky feeling that if I could turn the fans off with a switch of some kind while on the highway, the temp would stay the same or maybe even go down? One of my friends suggested adding a pusher fan in front of the condenser but that seems like overkill.



I used a corvette kit to put a foam seal around the entire 4-sided perimeter of the shroud/radiator so no engine air is pulled in. I also have a full core support cover to keep air flowing thru the grill and towards the condenser/radiator.



Because of the serpentine setup, its pretty tight as far as space between the shroud and the belts so my choices for 12" fans is somewhat limited. I would've liked to use a Lincoln Mk VIII setup but it was just too deep. Plenty of guys have said 200° isn't that bad for a modded BBC in this car but I'd really like to figure out how to knock down the cruising temp to 195° or slightly under so the fans don't run all the time once the car is warmed up. I thought about the coolant mix but doubt that adding more distilled water to the 50/50 premix would really make any difference. I haven't touched the timing since last year and before the car had the AC it had the 4-core copper radiator and a mechanical fan. It had a 160° thermostat and ran at 175°-185° on a hot day on the highway, maybe 190° around town and only if I was in dead stop traffic would it creep up to 210°-220° and that was after 10-15 minutes of barely moving.

So even though the car is drivable, I'm hoping I can improve something. Is the answer more CFM or maybe something else?-Mike

[raustinss]

My only suggestion is ditch the 200 hp engine contour fans and try to find either stock fans from a higher hp car or aftermarket ,where the blade count, width and pitch will be different. Just a different blade pitch can drastically change the cfm air flow . Again keep in mind those fans were designed for what a 200hp at most 4 cylinder, and I know you're pushing way more than that lol , cheers

[dontlifttoshift]

Lots of questions.

Pulley ratios before and after the AC/serpentine belt install? It obviously worked before, did it change?

How far is your condenser from your radiator? Too far away and the air gets turbulent between the two.

Why the dual 1.5" tubes in the new radiator? You added an inch to the core and then another 3/4" with the condenser. Late model radiators are thin on purpose, it is easier to push air through. It takes a lot of fan to draw through all that.

Where is the fan probe at? If on the bottom of the tank like the instructions say, move it to the top and get the fan running earlier.

At warm idle, what is the temperature differential between the top and bottom hoses?

Confirm gauge readings. Seriously, step one, confirm that your gauge is accurate. Everyone think theirs are spot on, but most aren't.

[dhutton]

With a 195 degree sensor the PWM controller is trying to control the temperature of the coolant exiting the radiator to 195 degrees afaik. If it enters the engine at 195 it seems reasonable that it would be 210-ish when it leaves the engine and enters the radiator.

Maybe try the 185 sensor if you want it to run cooler.

Don

[srode1]

I don't think your fans do anything at highway speed, I agree turning them off with a switch wouldn't change the temperature. You can do the math to confirm if you want. Your set up doesn't look bad to me for an electric fan set up, but you are blocking some of the radiator with the shroud. A pusher fan isn't going to help things, it will block more air, don't do it. Around town bigger diameter fans would help probably, maybe some on the highway too. Do you know what your A/F mixture runs in those conditions? Maybe you are running too lean?

[Vegas69]

On the highway that set up should run cooler than 200 in 85 degree weather. Not far from your t stat rating. I agree with looking at your air/fuel mixture and timing. A vaccum leak? Fatten up your idle circuit or throw some bigger jets in the primary side and see if it cools it down a bit. Does it surge under light throttle? Ping?

[Che70velle]

What rpm are you turning at highway speed?

[57vette]

Originally Posted by dhutton

With a 195 degree sensor the PWM controller is trying to control the temperature of the coolant exiting the radiator to 195 degrees afaik. If it enters the engine at 195 it seems reasonable that it would be 210-ish when it leaves the engine and enters the radiator.

Maybe try the 185 sensor if you want it to run cooler.

Don

I've tried 180° sensor and the 195° no real difference. Have also tried 160° and 180° thermostats, again, no difference in highway temp, fans are always on because once its warmed up its seems to stay at 200° which won't shut the fans down, and in traffic it goes to 220° and a little higher if its stopped and no airflow, just the fans.

Originally Posted by srode1

I don't think your fans do anything at highway speed, I agree turning them off with a switch wouldn't change the temperature. You can do the math to confirm if you want. Your set up doesn't look bad to me for an electric fan set up, but you are blocking some of the radiator with the shroud. A pusher fan isn't going to help things, it will block more air, don't do it. Around town bigger diameter fans would help probably, maybe some on the highway too. Do you know what your A/F mixture runs in those conditions? Maybe you are running too lean?

I kinda agree about the pusher concept. I don't know for sure what the A/F mixture is or the timing... gonna have to check that.

Originally Posted by Vegas69

On the highway that set up should run cooler than 200 in 85 degree weather. Not far from your t stat rating. I agree with looking at your air/fuel mixture and timing. A vaccum leak? Fatten up your idle circuit or throw some bigger jets in the primary side and see if it cools it down a bit. Does it surge under light throttle? Ping?

Hadn't thought of the vacuum leak possibility. No surging, no pinging, shuts off without any knocking or anything else.

While I'll admit that the article "Budget Cooling" drew me to these fans, plus the fact that they are shallow and many have used them for V8 engines including a 461 BBC although the El Camino has a bigger radiator than the Camaro I'm sure. Perhaps I have to look at a couple of more powerful 11'-12" fans that will fit without hitting the serpentine pulleys or belt.

Derale 16925 High Output Radiator Fan is a 12" that is rated at 2000 CFM at Zero static pressure, so maybe in real use it pulls 1500-1700 CFM? While they sell it separately as a Pusher, they offer it as a dual Puller 12" kit with a shroud and in the video demo they state it must be used with a custom shroud as a puller. I emailed them for more info and some better specs.



SPAL Automotive USA 30101522 is a 12" puller that's rated at 1328 CFM and I don't know if this one in tandem would be enough, although reviews say guys are using them with Big Blocks and they do the job. SPAL is supposedly the company that doesn't over rate their fans. These would probably fit well.

[dhutton]

Sensor won’t improve highway temperature. I proposed it since it should affect the slow moving and idle temperature which is 10 to 15 degrees higher than the highway temperature if I understood you correctly.

Highway temperature too high implies undersized radiator imho.

Don

[dhutton]

Suggestion to verify timing and AFR is an excellent one imho.

Based on what I know about you I know that you would enjoy logging and analyzing your AFR…

Don