What works better, two small ones or one big one? I have a 26X16X3 aluminum rad in the TR8. Stock had two small fans. On every replacement I have done before, I used a 14" fan and been done with it. Now that the car has the LS3 installed, I'm going to need every bit of cooling I can get. Might even need to go to a bigger radiator, but I have a 26X16 laying around, so I'm starting with that. I also have 2- 9" fans that came with another project, so I'd like to try and use them rather than go buy another 14" fan. Logic tells me the 2- 9" fans cover 125 sq inches and the 14' fan covers 154 square inches, so the 14" would be better.
What's the CFM rating on the fans?
Scratch that. Think I just found the 9" fans I have from Summit. They move a paltry 475 cfm each. Thats not getting it done. Guess I'm ordering a high flow Spal 14" fan.
tr8todd wrote:
What works better, two small ones or one big one?
Depends on the shape of the rad. Short and wide? 2 fans. Reasonably square? 1 fan. Basically, whatever will move the most air and fit in the car is the correct answer.
Spal has a series of low-profile, very high cfm fans---- I'd look into those if limited space is an issue.
I just snagged an early 90s (the less soap bar looking) Taurus fan for my LS1 swapped FC RX7 build. Supposedly flows like 3500cfm or something and I think I paid $25. Size should be about perfect too, mine is mounted on a 26x19 Speedway radiator and is probably about 3" short in height.
Edit: It's 21x16x7
I have heard that one of the best oem fans to snag is the ones out of a Volvo S70. They also come with a very nice relay pack that is easy to wire up. I am going to get one for my disco to get rid of the energy sucking mechanical
SPAL fans are rated at zero pressure drop or something. I have never had any luck with them moving air when confronted with a radiator core blocking their path.
Find an OEM fan that fits the radiator. My favorite OEM fan is the 2013 GT500 fan. It will overlap on a 16" core. It is huge, has profiled blades that MOVE air instead of just beat it senseless, and has a beefy motor that has two speeds: Serious, and Really Not Screwing Around. It is designed to pull large amounts of air through a radiator, A/C condensor, and about three or four other coolers in a thick airflow-robbing stack and STILL keep a 600hp engine cooled down.
And it's under $200 from Summit.
I have the Ford Contour V6 dual fan setup on the Stincoln smelLS. It's less than 3.5" thick and move a ton of air. I'm also using the Volvo 2speed relay in conjunction with the resistor to run it. This should give true 2 speed on both fans.
A link to help with wiring:
Switch + 2speed info
I have a pair of SPAL fans on my rear mount radiators and they've done a fine job in a less than perfect situation.
Knurled wrote:
SPAL fans are rated at zero pressure drop or something. I have never had any luck with them moving air when confronted with a radiator core blocking their path.
Depends on the model. They usually publish the specs at multiple levels, but everyone always advertises the zero drop number because it's most sexy. Kinda like the way everyone talks about maximum power but rarely advertises the torque available at 2000 rpm 
The biggest mistake people make is looking for slim fans. No. You want torque. You want big fat power-sucking motors. That'll give you the maximum draw through multiple heat exchangers. You can check this out by trawling through the Spal website and looking at all the ratings, not just the zero. We use fat Spals on our stuff and they move serious air.
Also, shrouds are important. They force the fan to pull through the core instead of pulling from around the edges of the fan. Set that shroud as far back from the core as you can, snuggling it right up doesn't work. Bonus points for bypass flaps. You can see the shroud (undersized for the radiator in the picture, so a significant portion of the rad doesn't get fan cooling) and the bypass flaps in Knurled's picture.
In reply to Keith Tanner:
Agreed. If a fan claims to only draw 15 amps, it's a piece of crap. If it's a monster like the much-loved Taurus fans and draws 40 - 50 amps on high speed, then it's worth something (and make sure to use beefy relays, fans like those are known for pulling damn near 100 amps on startup).
In reply to mad_machine:
Yup, the Volvo fans are supposed to work well too. Scoped those out at the JY before pulling the Taurus fan. From what I could tell on visual inspection, all of the 850s, S70s, V70s, ect use the same fan. I snagged the Taurus piece instead because it was easier to pull out and I liked the shape of the shroud better. Did grab a Volvo relay, though.
I have a Ford Windstar dual fan unit in my '77 Silverado. It draws more current than the alternator can put out, and will suck your clothes into the grill when you're standing in front of it.
If I leave it on (toggle switch), it over-cools the engine even with the thermostat closed.
It's awesome!
tr8todd wrote:
What works better, two small ones or one big one?
This is a math/geometry problem. Your fan options are represented by circies and your radiator by a rectangle. What arrangement of circles will fit in that rectangle and give you the maximum total circle area? That's your optimal setup. The rule of thumb is that you want to first jam in the single biggest fan that will fit, and then fill the remaining area with the biggest fan that will fit.
However, this is in all-performance, little-redundancy setup. The closer to equal your fan sizes are, the more non-high-speed cooling power you'll have left if one fails. Also for that reason, make sure each fan has independent ducting, such that if one fails, the remaining fan won't just be sucking air backwards through the dead fan.
Other tips:
- Thicker fans are better
- OEM fans last longer and are much cheaper than aftermarket fans
- Puller setups are always better than pusher setups.
Keith Tanner wrote:
The biggest mistake people make is looking for slim fans. No. You want torque. You want big fat power-sucking motors. That'll give you the maximum draw through multiple heat exchangers. You can check this out by trawling through the Spal website and looking at all the ratings, not just the zero. We use fat Spals on our stuff and they move serious air.
Also, shrouds are important. They force the fan to pull through the core instead of pulling from around the edges of the fan. Set that shroud as far back from the core as you can, snuggling it right up doesn't work.
Quoted for emphasis.
I read somewhere that you want the fan to be its hub diameter away from the core for optimal flow. Properly shrouded, of course.
Never had a TR8 overheat once a 26X16 aluminum rad with the 2.25 core was installed. Nothing else up there now, so don't need a huge sucker of a fan. No AC, no tranny cooler, nothing else. Granted the most I've tried to keep cool is around 330hp, but these Rover engines are known to run a little warm. I looked long and hard at the Camaro rad. At first glance, its huge. But then you actually look at the core and not everything stuck to the tanks, and its not that impressive. Core is only 1" thick. There is a built in power steering cooler, and a tranny cooler for the 6 speed. There is also a big AC condenser in the way. I'll use what I have and install a new 14" fan at least to get it running. If it doesn't work, I'll go bigger. I can drop the bottom of the rad 3" and go 19" tall, but would rather not. I can also cut away the frame rails where the rad sits and go as wide as 31". No worries about weakening the car with 110 feet of roll cage tubing installed so far. The shrouding I made up will definitely keep it cool once its rolling. I'm only worried about when its sitting still, and at that point in time, the engine won't be working all that hard anyway. Cross my fingers and see what happens.
Core thickness is not as important as area. Don't worry about being "only" one inch thick, that also means that the coolant going through the radiator is being cooled more thoroughly. Of course it all depends on what water ump you have, if it can't flow very much before it starts cavitating, you are going to have to work with old-school solutions.
I'd like to find the person who started the myth about water flowing too fast causing engines to overheat, and knock some sense into them.
Core design is more important than thickness. The biggest advantage of a thick rad is that you have more thermal mass to absorb heat. OE rads tend to have much more efficient cores than most aftermarket units.
tr8todd wrote:
these Rover engines are known to run a little warm.
It's one of the reason I run a "desert" t-stat on my disco. It opens at 185 and the engine rarely gets above 190, The regular one opens around 190 and will run close to 200
