mechanical to electric fans

[pandrade]

one of the first things i did to my supra was upgrade to a 3 row aluminum megan raceing radiator. i used a 89 fan shroud which allowed to me use its 2 aux fans versus my oe 87 which was a singe. all this and optimizing the water mixture keeps me cool at all my races and daily No problem.

i want to make a little more power and increase efficency and thought if i get rid of the bulky mech fan might free up bout 10hp and the added benifits of beter efficency, cleaner engine bay, and alot easier to change belts, my mechanic has taken charge of this project since i dont know crap bout wireing and we are hooking up a 2 speed electrical fan from a 5.7 durango and it fits perfictly( he has been raceing since befor i was born and custome building all his cars) he tells me the wireing is easly done since he has all the controll relays for the fan. the whole time he is giving me all the parts and ALL labor for 45$ since our familys go way back

my question is what temp should i set the relays to( he knows what he is doin perfictly i just want to better inform my self) i was thinking 100 for low speed and the high speed to kick on at 120. Your thoughts?

[cre]

You're not going to free up anything measurable... definitely not 10hp. Also, do note that when you increase the load on the alternator you increase the resistance of the alternator proportionately. And be careful... I don't know why but somehow well over half of the people who do this royally f#$% it up.

100? seems way off whether you're talking Fahrenheit or Celsius. Remember, the thermostat doesn't start to open until around 185?-195?F running them much before that and you'll be loading the engine and adding resistance for no reason (in which case just install a lighter mechanical fan). Engine bay heat isn't going to be a significant issue anytime the car is moving so running the fan, even on low, much before the thermostat's cracking temp doesn't make a whole lot of sense. I probably wouldn't run it until around 170?F and see how things go from there. If the fan moves a lot of air on low you could wait on stepping it up to high speed until 212?F (100?C) or so. This is all going to depend on how and where you drive and also how much air the fan moves at each speed. If you're thinking of the time you'll spend idle waiting in line when at the track between runs then just add another relay and switch to manually bypass the low temp trigger as desired. Data logging the engine temp while driving around for a couple days will help you get this set in no time.

[pandrade]

yah i dont know much about this part but he has done this countless times and has never had issues, even whith cars that he dailys and pushes well over my hp levels. he knows exactly what he is doin me i dont have the expirence so i let the profesonal handle it, i just want to better inform my self

at the track im not really concerned about sitting because most times i have about 15 min wait between runs so i just idle down the turbo and open the hood and let it cool. the main reson i want this is to clean up the engine bay and give me more space( i hate worken on and around the fan shroud its just bulky)

[pandrade]

just a crazy idea, dident the mk4 have electric fans vs the mechanical. couldent i just set the fans to the same temps as the mk4, i mean its same displacment, turbo, and only 1 gen newer wont the operating temps be nearly identical?

[Sonyps307]

The mk4 also runs a belt driven fan.

[pandrade]

dame, i thought they went whith electrical as oem. i dont know anything at all bout mk4 lol.

im gussing im gona have to have the low speed turn on at 210 and turn off at 180.

i could just run the factory set up and see where operating temp bounderys are and set the fans to stay in that heat range... any one know the factory operating temps off the top of there head?( ideal temp)

[Sonyps307]

I have a 2 row with dual 12" and the jegs wiring kit with a temp switch to come on at 200 and off at 185. Mine never overheats and it been 100 degree for a week now here.

[cre]

Thanks for posting some numbers Sonyps307. If you had two different speeds for the fans how do you think they would be best employed? I'm thinking turn on on low speed to help clear some heat out of the engine bay (popular mod on the MR2 but heat's a little more of an issue given their engine placement) and then hold off on high speed until you're sure you need the extra airflow.

[pandrade]

hey thanks for the advice guys(especialy numbers sony), knowing a temp range that works for others really helps wit mine

[Sonyps307]

Well my 2 fans turn a 2300rmps moving 1500 cfm of air each. So u should find out what the one ur using is.