When to turn on and off cooling fans?

[blitzer454]

Ok, thanks for the chart, I'll see where I'm at on the table tomorrow.

[dhutton]

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.

Any half decent design process includes a detailed test phase and data analysis to confirm the design goals were met with adequate margin....

I’m impressed with what you have done here. I’m pretty good with hardware but couldn’t write a line of code to save my life. LOL....

Don

[blitzer454]

Oh God, you're not an product manager are you, I just lost all respect for you.

[dhutton]

Oh God, you're not an product manager are you, I just lost all respect for you.

Retired chief engineer...

Don

[blitzer454]

Cool, I just retired a little over a year ago. Semiconductor apps engineer here.

[dhutton]

Cool, I just retired a little over a year ago. Semiconductor apps engineer here.

I retired almost 3 years ago. Never looked back, I’m out in my shop building cars almost every day.

Don

[blitzer454]

We share the same retirement plan, but I suspect I'm building at a much slower rate than you.

I was discussing this problem with my brother who writes the firmware for me and we're going to also try staggering the turn on times of each fan as this should help limit the amount of inrush current when the fans come on. That inrush could very well be what was bringing my alternator down.

[dhutton]

We share the same retirement plan, but I suspect I'm building at a much slower rate than you.

I was discussing this problem with my brother who writes the firmware for me and we're going to also try staggering the turn on times of each fan as this should help limit the amount of inrush current when the fans come on. That inrush could very well be what was bringing my alternator down.

Soft start them by ramping the pwm duty cycle.

Don

[blitzer454]

Yep, the radiator fans already do that but the pusher fans don't but it won't hurt to stagger them all.

[dhutton]

Have you tried it without the pusher fans? I hope you aren’t circulating air back to front. Without a close out panel I could see it happening.

Don

[blitzer454]

Yes I have, temps are better with the pushers, but that gives me an idea. I think I'll fab up a temporary close out panel and see what that does.

[dhutton]

Quite a few options on eBay

https://www.ebay.com/itm/67-69-Camar...0AAOSwitRa1iH6

If it helps try one on the bottom. The first gen Ram Air Firebirds had a lower close out panel too.

[Rag Top Rob]

A little off topic I know.
I have always wanted a LSA in my 69, I drive a 2013 ZL1 Rag Top moded to 750 HP. I love it, to say the least.
I also know of all the cooling requirements in my 5th gen. and then the new 6th gen blower cars (LT4) have something like 12 coolers. I live in the deep HOT south.
That said, I have always been afraid to jump into the blown motors in a 1st gen. Just saying..
Do these really work out in hot climates or is it just a on-going battle?
Thanks Rob

[dhutton]

A little off topic I know.
I have always wanted a LSA in my 69, I drive a 2013 ZL1 Rag Top moded to 750 HP. I love it, to say the least.
I also know of all the cooling requirements in my 5th gen. and then the new 6th gen blower cars (LT4) have something like 12 coolers. I live in the deep HOT south.
That said, I have always been afraid to jump into the blown motors in a 1st gen. Just saying..
Do these really work out in hot climates or is it just a on-going battle?
Thanks Rob

I think the answer is it depends on how hard you want to drive it and how much you want to spend. If you research Mark Stielow’s LS9 powered Hellfire you will see that he used a huge custom C&R radiator with integrated coolers coupled with a very high cfm pwm controlled fan. He also had close out panels and hood vents. The LS9 is modded and produces around 950 hp if I remember right. He road raced it and had no cooling issues. He sold the car and now has an LT4 powered Camaro with a similar cooling setup.

Don

[Motown 454]

My Mechanic had a sign in his garage How Fast You Want To go $$$$$

[nicks67camaro]

2 of the best cooling mods I did was the hood vents and close out panel. Channeling all the available air through the radiator and having a place for the at hot air to escape from absolutely helps these cars.

My (built) LSA first gen cooling set up will consist of:
C&R Radiator with integral oil cooler
Afco Heat Excahnger (gt500 base)
Vintage air heat exchaner
SPAL twin 11" fans
pwm DCC controller
Hood vents
Radiator close out panel

I have thought of using 2 "extractor" fans molded into the hood at the vents to help pull air out of the engine compartment. My old SBC set up with the hood vents you could see on a cool day the amount of heat radiating out. Plus it helps get the trapped air out at higher speeds.

[dhutton]

2 of the best cooling mods I did was the hood vents and close out panel. Channeling all the available air through the radiator and having a place for the at hot air to escape from absolutely helps these cars.

My (built) LSA first gen cooling set up will consist of:
C&R Radiator with integral oil cooler
Afco Heat Excahnger (gt500 base)
Vintage air heat exchaner
SPAL twin 11" fans
pwm DCC controller
Hood vents
Radiator close out panel

I have thought of using 2 "extractor" fans molded into the hood at the vents to help pull air out of the engine compartment. My old SBC set up with the hood vents you could see on a cool day the amount of heat radiating out. Plus it helps get the trapped air out at higher speeds.

Pretty much the same as mine but stock LSA and C&R heat exchanger.

Don

[blitzer454]

Here's what I have done so far:

1. Added foam tape to seal between hood and top of core support. This is a cheap mans version of a close out panel. This will block hot air from recirculating through the fans.
2. Added some foam tape between back of radiator and core support, but still some gaps between core support and heat-exchanger that foam tape can't fill. But this should help the fans pull and push air through all radiators with less air escaping around the sides.
3. Changed firmware to turn fans on at 189* at 60%, 197* at 80%, and 205* at 100% pwm. Using 5* hysteresis.
4. Pusher fans still come on whenever radiator fans are on and radiator fans are still a function of trinary switch and engine temp for now.
5. Pusher fan turn on times are now staggered. The 1st fan comes on 200ms after it receives the command and the 2nd fan will wait 700ms after receiving the command. Radiator fans have always been using soft start. These changes will reduce the inrush current.
6. I took out a gallon of 50/50 coolant and replaced it with straight distilled water also added a bottle of wetter water. Water transfers heat better than antifreeze but the draw back is higher freezing point and lower boiling point.
7. I backed probed one of the radiator fans and the voltage was down about 0.7V from the battery voltage which isn't bad. I could improve it slightly if I did some rewiring. Currently I have the fans connected to a H-bridge as I was using the fans to test my BCM. So instead of configuring the driver as an H-bridge I could rewire it to a low side driver configuration. But that would only improve the voltage by about ~0.4V.

During the test drive the engine temp at highway speeds is still right around 195* and in normal stop and go traffic I was seeing temps around 208*. I do think that it cools down quicker once I start moving, but I'm not convinced that it changed much when sitting in one place. I let it sit and idle for almost 10 minutes and the temp climbed up to 212*. I didn't run it any longer than that as my alternator is pretty much dead now. The voltage is mostly staying around 10.4V while idling and when driving it will occasionally bounce up to 13.5V. This also occurs even with the pusher fans disconnected.

I'm pretty much convinced that I need radiator fans with higher CFM. I talked to Entropy and they have a shroud with two 14" fans. I think he said the fans stick out about 4.5" which may hit my remote oil filter, but I think I can move it down enough to make this shroud work. I also like the idea of adding hood vents. Does anyone have any recommendations for a vent set that will find the '67 Camaro cowl hood? For those of you running a LSA or other supercharged engine, what temp do you see when standing still at idle for 15 minutes or more? It would be nice if I had a target temp to shoot for.

[dhutton]

It is possible that you have air trapped in the coolant passages. Have you burped the system? It helps if you fill the radiator with the nose of the car raised a foot or so to help air escape.

I bought one of these to get all the air out of the engine and also the intercooler system.

https://www.ebay.com/itm/For-Car-SUV...oAAOSw~o5acYvt

My LSA won’t be running until the fall so I can’t offer you any temperatures.

Don

[dhutton]

This guy makes some nice hood louvers:

https://www.pro-touring.com/threads/...ght=Hood+vents

Don