Andy43 Posted March 28, 2012 Report Posted March 28, 2012 Looking at reducing power losses to a 3k via a alternaor disconnect cct. Can I just add a solanoid to disconnect the output from the alternator ? Or would a better option be to open the field winding via a relay ? Thanks Andy Quote
altezzaclub Posted March 28, 2012 Report Posted March 28, 2012 I'd go for a switch in the feed wire. That way the alty is not energized at all while its spinning. Mind you, the power you gain will be offset by the extra weight in wires and switches! If you took the armature & windings out completely you could take the voltage regulator out too! Quote
ke70dave Posted March 28, 2012 Report Posted March 28, 2012 (edited) what i want to know is, do you realise how miniscule the power losses are? ~13.8V x 50A x 1/60 (efficieny guess) = 1150W. ~ 1kw of power. (admitedly add a bit more for belt losses etc....but still....) but i guess for a race car, everybit helps, altezzas suggestion sounds good, switch the energising wire. Edited March 28, 2012 by ke70dave Quote
coln72 Posted March 28, 2012 Report Posted March 28, 2012 Thought about this briefly for my club car back in the day. Couldn't justify the stuffing around as it was technically against the regs and I'd have to hide it :( My other worry was that I'd forget to switch it back and run the battery flat. Why not just take a couple of batteries and swap them between races and run without an alternator, or just gut it and have it for show. Save the weight of all that copper etc and the power gain :hmm: Quote
ke70dave Posted March 28, 2012 Report Posted March 28, 2012 have the switch setup on the bottom of your accelerator pedal, so it only turns off the alternator over half throttle. oooh ooh! you could set it up so when you hit the brakes the alternator turned on! Just like the F1 KERS system :P Quote
B.L.Z.BUB Posted March 28, 2012 Report Posted March 28, 2012 (edited) Thats a cool idea. only switches on under braking. And easy too just hook a wire from your brakes to the alt power wire... Edited March 28, 2012 by B.L.Z.BUB Quote
altezzaclub Posted March 28, 2012 Report Posted March 28, 2012 I like it! Very clever- what else can we help you cheat with?? Quote
Andy43 Posted May 13, 2012 Author Report Posted May 13, 2012 (edited) what i want to know is, do you realise how miniscule the power losses are? ~13.8V x 50A x 1/60 (efficieny guess) = 1150W. ~ 1kw of power. (admitedly add a bit more for belt losses etc....but still....) but i guess for a race car, everybit helps, altezzas suggestion sounds good, switch the energising wire. When your only making 75hp or so its 2% improvment for free. Edited May 15, 2012 by Andy43 Quote
Sephiroth Posted May 13, 2012 Report Posted May 13, 2012 2% gain 75hp - 76.5hp ?? The extra hp from this doing this kind of mod to my 3k will stop people on push bikes over taking me Quote
towe001 Posted May 13, 2012 Report Posted May 13, 2012 Thats a cool idea. only switches on under braking. Same same. But i think there'd be one small problem. How often would the brakes be used in a typical 10 lap race ? Maybe wire in a switch into the battery sensor wiring. That way a relay wouldn't be needed. Quote
sprinterfiend Posted May 14, 2012 Report Posted May 14, 2012 I think it would be easiest to use a kickdown switch from an older automatic car to turn off your alt. The kickdown switch was located under the accelerator pedal on my old 180b. It used to have an audible click when you pressed the accelerator pedal past about 90% causing the auto to kick down a gear. it would then turn off again once you lifted back passed that point. Quote
ke70dave Posted May 14, 2012 Report Posted May 14, 2012 (edited) Dave you didn't need to be a arsehole in your response. When your only making 75hp or so its 2% improvment for free. appologies as to how i seemed to come across, but i can't see how i was an ar$ehole, i did the math, and i gave 2 suggestions on how you could achieve what you want to do. remember that with the alternator off you are then running your ignition system (specifically the coil) on 12V not, 13-14V as it is designed. now i don't know much about coil design, but if a coil is designed to run on 13-14V and its only getting 12V, i suspect you will get a Smaller spark, and if not smaller spark it will change it somehow. So it is possible you will lose any gains you get (1kw), when you turn off your alternator, by reduced spark. Edited May 14, 2012 by ke70dave Quote
towe001 Posted May 14, 2012 Report Posted May 14, 2012 Just one hiccup on that Dave - ballast resistor. Isn't the ballast resistor suppose to drop the voltage down to a more user friendly 6-8v for the coil ? But i do see what your getting at with the more voltage the bigger and stronger the spark. Quote
ke70dave Posted May 14, 2012 Report Posted May 14, 2012 hmm true not sure how the balast resistor works though, if its got an inteligent regulator in it then it will give out the same voltage no matter what input its given..(within a range) if it is indeed just a resistor, then if it was being fed 13-14V before, and giving out ~7V, and now its only getting 12V it will only give out 5-6V...surely that can't be good? Quote
towe001 Posted May 14, 2012 Report Posted May 14, 2012 Nar not really. Just had the thought, maybe underdrive the alternator Quote
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