chrisdavid Posted February 21, 2012 Report Share Posted February 21, 2012 I'm sure this topic has been discussed over the years on LSSZ. I did a lot of research (i.e. googling) for the last few hours. I wanted to get the boards opinions on running a mechanical fan vs. electric fan. Currently we are running a Mechanical fan on our crate 350 Truck at HMP. It's light plastic material. We have never had a cooling issue, it's always been fine. The question is, are we losing a measureable amount of horsepower with our mechanical fan? Should we switch to an electric fan? I really don't want to run an alternator. We run a new optima battery with a switchable Transmission cooler fan. Although we have never had any battery issues, we haven't run a whole lot of power on it. I would assume that the optima battery could handle an hour long race of two fans running (occasionally). Has anyone had any experience with this? Would we pick up HP by dumping the mechanical fan and going electric (I'm sure this answer is yet)? If so, is the change worth it if we are running cool now? Here is a picture of our current "working" set up. I'd like to know what YOU would do? Link to comment Share on other sites More sharing options...
lcpyltx8 Posted February 21, 2012 Report Share Posted February 21, 2012 We run electric fans out here in VA on my Grand Stock. I only run a single, but after 3 practice sessions (15 laps each ish) my battery was drained... this was before we put the optima in. but since then i've always run a racing mini alternator with the optima. It's a 50 amp unit, never seen dyno numbers (dont seem to affect it too bad to me), but another thing i've seen done so you dont loose HP is run the alternator off the rear end. there are some brackets out there you can buy with the pulley already welded to the yoke but they're pricy. my unit is thermostat controlled so it's not on "all" the time, but it's pretty much on 100% of the time im on track, and i'd say with a tranny cooler fan, you'd kill the battery fairly quick. -Shawn Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 21, 2012 Report Share Posted February 21, 2012 On the cars we deal with that run no alternator we have gone through serious efforts to eliminate every amp of draw due to the unpredictability of a circle track race, you never know when you’re going to have to turn a hot starter. The electric fan would run during red-flags which means you when be running it when you were about to ask the most of your battery. Beyond that keep in mind the high draw of even the best fans (20 amps) will increase the heat (and resistance) of your main electrical wires and cause an overall higher rate of draw on the battery. I like electric fans; we run them on everything, in your case it just doesn’t seem like a good option. You could switch to an alternator but then you’d lose draw from the mechanical fan and gain it with an alternator so it’s no big win. Link to comment Share on other sites More sharing options...
Truck99 Posted February 21, 2012 Report Share Posted February 21, 2012 The alternator vs no alternator debate in the circle track world is about as controversial as "what is the best oil?" My 2 cents - if you're running more than about 30 laps or if you are running an electric fan, keep the battery charged between runs and run a lightweight racing alternator. You'll gain more than you'll lose at the end of the race just by keeping your electrical system fully charged. Link to comment Share on other sites More sharing options...
sm44 Posted February 21, 2012 Report Share Posted February 21, 2012 How much drag does a "free Wheeling" alternator use hp. wise? I have had the idea of running a switch on the alternator and during cautions/ parade whatever having it on and while racing having it off, would this be worth it to the guys running alternators? joe Link to comment Share on other sites More sharing options...
lcpyltx8 Posted February 22, 2012 Report Share Posted February 22, 2012 in the case of a vehicle... The modifications required to turn off the magnetic field would not be worth it. In something like the motor/generators i deal with every day, they're 20ft tall and weigh thousands of pounds. Thats alot of rotating mass and the fields generated contain a lot of current, and we can "turn off" the field. we actually see a LOT less steam load on the turbine end while the machine is unloaded. I dont see how installing a small "denso" style alternator would make that much of a difference in HP for the work put in to alter the field since it's all regulated internally, then you still have a lb or 2 of rotating mass to deal with. in a comparison to the forces generated by the field or by the rotating mass, i would say that the force applied by the rotating mass would be far greater than the field generated by a 12v DC alternator, but still not something that cant be made up by adjustments in suspension so you have that ability to carry that speed through the corner. -Shawn Link to comment Share on other sites More sharing options...
JamesHigdon Posted February 23, 2012 Report Share Posted February 23, 2012 If the electric fan debate comes back to a pure power issue I would call it near to a wash with a high quality fan and no alternator vs. an electric fan with an alternator. If it comes back to reliability and repeatability then the extra insurance an alternator gives plus the ability to keep your motor cool during cautions and red flags sounds best. I have seen very few stock cars that didn't puke up coolant sitting during a red-flag. In relation to cost use a mid-eighties GM crank, water pump and alternator multi-groove pulley setup on a junk-yard 66 amp unit gone through by a local rebuild shop and you'll have a complete setup under $250 brackets, wires and all. Early 90's Maximas (the squarer body) run a great dual fan setup the as far as I've seen can't be killed off by an act of man and can be had for $40 or $50 and Lincoln Mark cars of the 90’s run a huge single fan that can cool most any V-8. More money gets you new parts obviously but it can be done cheap. If you don't want to run an alternator then in my opinion your current setup is optimal. Link to comment Share on other sites More sharing options...
CC57 Posted February 23, 2012 Report Share Posted February 23, 2012 Chris, do some google searches and I think you will find (and keep in mind, after the heatng issues I experienced last season, I should be an "expert on this stuff ): 1. Don't run the 6 blade "plastic" flex fan. It flattens out too much at speed, creating more of an air damn than a air flow device. Consensus is the GM 4 blade steel fanis superior. 2. Run an alternator. For what little horsepower draw you may lose running the alternator, you will more than offset it by the power gained by keeping a good voltage level supplied by the alt to the MSD ignition (i.e., the battery voltage will not drop off during the length of the race.) 3. The horsepower draw on the water pump having to turn the fan blades through the on-coming air is greater than the horsepower draw placed on the engine from the alternator 4. With a good serpentine system (read as proper tensioning) and good belts, there is very little draw on the engine. 5. Under Yellow or Red conditions, it’s nice to be able to cool the engine by turning on the electric fan rather than running up the RPMs on the engine to get the blades to pull more air. 6. Unless you have a very well configured fan/shroud assembly (your's looked pretty close if not on the mark), a good electric fan will produce more CFM, both during static (stopped) and dynamic (moving) conditions than the mechanical Hope this helped you some… Link to comment Share on other sites More sharing options...
chrisdavid Posted February 23, 2012 Author Report Share Posted February 23, 2012 Thank you all for the feedback. I know Robert that you are an expert after last season. I never used my head to think about the possible power loss from no alternator. I think we will be switching to an alternator and electric fan in the months to come. Thanks again! Chris Link to comment Share on other sites More sharing options...
bret90 Posted February 24, 2012 Report Share Posted February 24, 2012 Thank you all for the feedback. I know Robert that you are an expert after last season. I never used my head to think about the possible power loss from no alternator. I think we will be switching to an alternator and electric fan in the months to come. Thanks again! Chris Up here in the NW/MI area we run electric on most SLMs. Even in 200 lappers. And those guys are winning. Can you run two batteries and connect them? Voltometer gauge? I saw Gary Lewis switching out batteries half way thru a 200 lap race........ Any 16" single Spal or Derale. Or a stock one off a 95ish Ford Mustang or Windstar. Link to comment Share on other sites More sharing options...
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