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  1. #1
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    When to turn on and off cooling fans?

    I have an CTS-V LSA engine in my 67 Camaro. I'm using Entropy's radiator which has two 12" radiator fans. In front of the radiator I have the C&R heat exchanger for the supercharger and Vintage Air condenser in front of that. I recently add two Spal 6.5" pusher fans in front of the condenser. All four of the fans are controlled by a BCM that I designed myself. This BCM also has inputs for a radiator mounted temp sensor and A/C trinary switch. The two radiator fans are PWM controlled so I can command whatever speed I want for them and the two pusher fans are just on or off. What I'm trying to figure out is what temps I should be using to turn these fans on and off.

    Right now when I'm at highway speeds the engine temp is always right around 195* which is the same as the thermostat that I am using. In normal stop and go traffic the temp will rise to around 210*. But if I get caught in really bad traffic where I am forced to sit in one place for 15 minutes or more the temp starts to slowly creep up to 230* and even higher if I have to wait longer. Keep in mind this is in Dallas area where the outside temp is already 100*.



    So what are normal engine temps for this engine and at what temp should I start to freak out? I used to freak out when it started to get into the 230* range but now I'm thinking that might be normal. The other question is what temp should I start the radiator fans and at what speed? Right now I command them both to come on at 180* at 40% then at 195* at 75% and finally full on at 200*. If the trinary switch is on then both fans are commanded on at 85% unless the engine temp is 200* or more in which case the fans will again be full on. The two pusher fans are on whenever the radiator fans are on, but I'm already thinking about changing this to just having the pusher fans on only when the trinary switch is active or the engine temp is above 205*. I'm also starting to think that I have the radiator fans coming on too early. What are your thoughts?


  2. #2
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    What degree thermostat are you running? Are the pusher fans a function of IAT or engine temp?

    I have a similar set up (LSA with A/C and SC HX) i have a concern around IAT not engine temp but now you're making me nervous! i will run a 160F thermostat which most LSA builds in the Camaro 5 forum use when upgraded pulleys ect....
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  3. #3
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    The thermostat is stock at 195* and the pusher fans are a function of trinary switch and radiator temp sensor. My IAT is usually around 85* to 100* at highway speeds, not sure what it is in bad traffic. I guess I should start monitoring that more closely as well.

  4. #4
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    The OEM thermostat starts to open around 187 degrees and is fully open by 195. On my Cougar I start to ramp in the fan (it is PWM controlled) once the temperature reaches 200. By 205 the fans are at 50% and the temperature rarely goes above 210.

    On my GTO, factory thermostat also, but GMPP harness. The fans are programmed to come on at 212 and shut off at 205.

    If your temperature is not holding steady (no higher than 215) in traffic with the fans on full blast, then I say you have an airflow problem. You either need a more powerful (more CFM) fan(s) or you need better ducting to direct the flow of air through the radiator core.

    Andrew
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    "You were the gun, your voice was the trigger, your bravery was the barrel, your eyes were the bullets." ~ Her

  5. #5
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    couple other thoughts:
    Are you running oil cooler? If so is it in you cooling stack?
    Radiator core support close out could help push/direct air through the core
    Where is the pwm taking the temp signal from? it could be coming in to late. Most PWM companies (auto cool guy/DCC) have very detailed instructions on where to mount the probe for best PWM results.
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  6. #6
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    I have a Tremec 6 speed, so no oil cooler. I just went for long test drive, with the A/C on the whole time and the highest temp I saw was around 215*. This was the first long test drive using the pusher fans so they definitely are helping. But now I noticed that my alternator will drop out in stop and go traffic, I can't win. The voltage will dive down to about 10 or 12 volts then yo-yo back up to around 13.5V. I'm guessing the voltage regulator is not liking the extra current draw and going in and out of thermal shutdown. So now I'm thinking that I need to find a happy compromise between keeping the engine cool and keeping the current draw to a minimum when I can. There is some gap around the radiator and the heat ex-changer that I probably should fill up with some kind of stick on padding, thanks for the tip. My BCM is reading the temp from a standard Delco temp sensor mounted in the bung that is provided on the Entropy radiator. I have found that this temp is usually 3 to 5* lower than the block temp sensor.

    So Andrew says his fans don't start until 200* and I think that is the right course to take. So I'm going to try start ramping up the radiator fans at 200* and be full on at 215*. I don't see any point in having the fans come on any lower than that as any temp lower than that means that the car is moving fast enough that normal air flow will take care of the cooling. Since I have pusher fans, I think I will make the radiator fans a function of engine temp only and have the pusher fans come on whenever the trinary switch is on or if the engine temp is 210* or higher. How does that sound?

  7. #7
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    I think your fan temp range is right based on the factory 195* thermostat. Couple other cooling options if you think you need it.

    Agree with the "foam strips" to help funnel air
    I added hood vents which help get all that air out (might not be an option for you)
    I saw the entropy fan shroud is pretty blocked off. I like how SPAL uses the rubber flaps to open at any speed for an easier pass through of the air.

    I think the stock CTS-V Alternator is 105 amps
    The 2012 zl1 camaro is 150

    I think they both use the low mount driverside stud on for mounting location. Easy upgrade if you infact only have 105 amp.
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  8. #8
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    Those Entropy fans use a lot of current, considerably more than the Spal fans most use as far as I know. With those fans and pushers you have likely exceeded the current rating of your alternator. I don’t think your regulator is going into thermal shutdown since the alternator voltage has dropped lower than the regulator output voltage.

    The suggestion to add hood vents is a good one. So is the one to add a close out panel if you don’t already have one.

    I think the oil cooler suggestion was for an engine oil cooler. LSA engines have oil coolers in the CTS-V and ZL1.

    Tweaking fan temperatures isn’t going to solve an overheating issue when the fans are running full speed imho...

    Make sure that you are using large gauge (4 gauge maybe) wire to connect the alternator and fans to avoid any voltage drop and the resulting fan speed drop.

    Don
    1969 Camaro - LSA 6L90E AME sub/IRS
    1957 Buick Caballero - huge project
    1959 El Camino - Ironworks frame
    1969 Mustang Sportsroof
    1956 Cameo - full C5 suspension/drivetrain

  9. #9
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    I got my front drive accessory kit from Street & Performance back when they were still in business. I looked at my documentation and it says the alternator is a CS130 140A. I'm not digging the Entropy fans, I think they are too small and I agree that they draw too much current given their size. So is there a better fan and shroud that is a drop in replacement for the Entropy one?

  10. #10
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    I don’t think you are going to find a replacement fan setup that drops onto that Entropy should. He claims they move more air than the Spal fans. I am assuming you have his newer fans.

    Curious about your PWM circuit. Does it deliver full voltage at 100% duty cycle or is there an inherent voltage drop? Have you verified the actual fan voltage when the fans are on 100%? What is the RDSon of your device?

    Don
    1969 Camaro - LSA 6L90E AME sub/IRS
    1957 Buick Caballero - huge project
    1959 El Camino - Ironworks frame
    1969 Mustang Sportsroof
    1956 Cameo - full C5 suspension/drivetrain

  11. #11
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    Quote Originally Posted by dhutton View Post
    I think the oil cooler suggestion was for an engine oil cooler. LSA engines have oil coolers in the CTS-V and ZL1.
    Don
    Yes I was referring to the oil cooler. My experience engine oil has a lag behind coolant temps and could be contributing to the overall higher temps being seen.

    If the fan system is going to get changed I know SPAL dual fans are pretty tried and true
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  12. #12
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    I apparently have the old fans as what I have does not match the picture he is now showing on his website. Mine look like this:
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    Yes, the BCM will give full voltage at 100% PWM. The RDSon is only 18 miliohms. No I haven't actually probed the voltage at the fan yet.

  13. #13
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    Hmmm, I wasn't aware of the engine oil coolers on the CTS-V. I only have a remote oil filter attached to the front of the subframe that does get some good air but only when moving.

  14. #14
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    Can you could flip the fans to get them closer to the top. This way you are pulling air directly at the hottest part of the system?
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  15. #15
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    C&R has a nice radiator setup with Spal fans and integrated oil and power steering coolers. Improved Racing has an oil cooler thermostat that you will want to add to insure that the oil gets warm enough in cool weather.

    I used that same Entropy radiator and fans in a couple of LS builds and had absolutely no overheating issues.

    I recommend you measure your fan voltages right at the fan. Make sure you are not dropping voltage across your grounds.

    Don
    1969 Camaro - LSA 6L90E AME sub/IRS
    1957 Buick Caballero - huge project
    1959 El Camino - Ironworks frame
    1969 Mustang Sportsroof
    1956 Cameo - full C5 suspension/drivetrain

  16. #16
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    It looks like the fans are located in the middle of the shroud so flipping them wont help. I might try calling Entropy tomorrow and see what's up with the fan change. Perhaps he can do an exchange if the newer ones are truly better than the old ones.

    Don, were your LS builds also LSA engines with the additional heat-exchanger? I'm wondering if that is making a big contribution to the whole heat issue.

  17. #17
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    I have the "gt500 / ZL1"
    https://www.speedwaymotors.com/AFCO-...RoCOBcQAvD_BwE

    Its half the height but double the thickness. I am going to run the C&R universal with integral oil cooler and make my own brackets. the "lous change camaro used this type of heat exchanger. I know the "zr9 camaro used the cooling stack similar to what you have with dual spal fans with no cooling issues.

    http://v8tvshow.com/V8TV_2/index.php...o-zr9?start=48
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  18. #18
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    Quote Originally Posted by blitzer454 View Post
    It looks like the fans are located in the middle of the shroud so flipping them wont help. I might try calling Entropy tomorrow and see what's up with the fan change. Perhaps he can do an exchange if the newer ones are truly better than the old ones.

    Don, were your LS builds also LSA engines with the additional heat-exchanger? I'm wondering if that is making a big contribution to the whole heat issue.
    No for my LSA build I used a custom C&R radiator with integrated oil, power steering and transmission coolers. The Entropy radiators were used on NA builds.

    Sitting in traffic your supercharger is essentially bypassed and should not be generating a lot of additional heat load. Do you have the stock LSA cam?

    Until you measure your fan voltages I am not convinced the fans are an issue. That is pretty basic engineering practice and it sounds like you are an engineer... :>)

    Don
    1969 Camaro - LSA 6L90E AME sub/IRS
    1957 Buick Caballero - huge project
    1959 El Camino - Ironworks frame
    1969 Mustang Sportsroof
    1956 Cameo - full C5 suspension/drivetrain

  19. #19
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    Dang, that reminds me that I forgot to monitor my intake air temp while sitting in traffic, although I'm not sure what a good number should be anyway. But I bet it shoots up to 150* or so. The entire engine is still stock for now.

    My nephew wants to sell his 68 Firebird project and I've already decided to take it off his hands. I foresee a radiator swap taking place in about 5 years from now as the plan for that build is to keep it simple with just a 350 SBC that came out of my Camaro. Maybe sooner

    I really do wish that I had brought a radiator with the additional coolers, but since this is my first build I didn't know better.

    Don, I'll measure the fan voltage tomorrow but I'm confident in my Engineering skills ;) I figured you was an Engineer when you asked about RDSon, most people wouldn't know what that is.

  20. #20
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    That sounds high for IAT. Stock ECU pulls timing in the mid 80's. Here is a good chart

    https://www.camaro5.com/forums/showthread.php?t=465911
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    Nick S.
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