Alternator Switch

[nisskid]

wondering if anyone has played around with an alternator switch, a switch to disable it to reduce load on the engine, for applications like drift/drag i can see it's use, my worry is voltage drop even over a short period which could cause ignition issues.

i'm looking at using thermo fans instead of clutch fans, and hoping i can bypass the disadvantages of the current they draw putting load back on the engine. if i can get away with 1 minute of hard driving, then 4 minutes of easy driving/idling to restore the battery, then i'd be happy.

the other question is if it's possible to add the switch to be triggered by your pedal, so anything over half throttle it automatically switches it off, or whether this constant on-off environment is shit for an alternator.

i know it used to be used by a few of the drag guys back in the day, wondering if there's an obvious reason i don't see as to why it's not more popular?

probably a stupid question, but interest either way.

[Duncan]

Not possible unfortunately....the drag is caused by the power required to turn the alternator, and the alternator would be turned no matter whether it was on or off.

A/C (or my March's supercharger) have an electric clutch that disengages the pulley from the compressor which reduces the drag to almost nothing when turned off, big difference.

you can of course run without an alternator if the car can run on battery power and be recharged in the pits

[GTSBoy]

That's not entirely true Duncan. Any electric generator places an increasing mechanical load on the drive shaft as the elctrical load increases. Electromagnetism is powerful stuff. Action at a distance and all that. Just because the rotor doesn't touch the stator, doesn't mean they're not linked.

[pipster11]

Why not turn the thermo fans off for 1 minute? Then cruise for 4?

[GTSBoy]

Why not turn the thermo fans off for 1 minute? Then cruise for 4?

Because that gives him no forced cooling. With his original idea, the fans keep running off the battery while the alternator switch is off. The alternator is unloaded but the fans still work.

It seems to me, that if you are going to go to this amount of trouble for drifting, then you'd be better off just putting another big battery somewhere in the car, wiring the fans up to that separately and not putting any of that on the same charging circuitry as the rest of the car, and just charge the battery from the mains in the pits.

I also don't like the idea of flicking the alternator on and off while driving around, and especially having it switched off while you're thrashing the engine, because you need all the battery & alternator voltage you can get to keep your fuel pump running the way it was when the car was tuned, and keep the injectors working the same way they were when the car was tuned, etc etc. If you start to rely on the ECU's voltage compensation you may start to cause yourself problems that you didn't need to.

[TiTAN]

why not just setup the thermo fans properly on a temp controlled switch so they are only on when required instead

[GTSBoy]

why not just setup the thermo fans properly on a temp controlled switch so they are only on when required instead

I think that's the point. If you're drifting and you up it for 30+ seconds going sideways, you'd probably have the fans on during the drift and he would rather that they were not pulling on the alternator at the time.

[TiTAN]

if powers an issue run a bigger/better turbo instead.

its not like these are tiny capacity NA cars that need as much help as they can get to make a few HP

[nisskid]

Not possible unfortunately....the drag is caused by the power required to turn the alternator, and the alternator would be turned no matter whether it was on or off.

A/C (or my March's supercharger) have an electric clutch that disengages the pulley from the compressor which reduces the drag to almost nothing when turned off, big difference.

you can of course run without an alternator if the car can run on battery power and be recharged in the pits

you can't get rid of all the mechanical load on the motor without fully removing the alternator, however you can reduce the load, the more the battery requires, the more loaded up the alternator needs, if you basically tell the alternator to not bother charging the battery at all, you reduce the load hugely.

this is one in use, the eco guys are jumping on board with it, although i think it's kind of stupid as realistically the fuel usage will equal out, a lot of them instead are just manually recharging when they get home and run no alternator at all.

if powers an issue run a bigger/better turbo instead.

its not like these are tiny capacity NA cars that need as much help as they can get to make a few HP

mm, the cost of a switch vs the cost of a larger turbo + support mods and new tune, hard decision lol.

even if we are talking about better off load engine response, for drift that's quite handy, for the effort of flicking a switch after each run, it's worth it.

[nisskid]

I also don't like the idea of flicking the alternator on and off while driving around, and especially having it switched off while you're thrashing the engine, because you need all the battery & alternator voltage you can get to keep your fuel pump running the way it was when the car was tuned, and keep the injectors working the same way they were when the car was tuned, etc etc. If you start to rely on the ECU's voltage compensation you may start to cause yourself problems that you didn't need to.

this is the part that worries me, that's not a bad idea actually, run a smaller battery running off the alternator constantly for vitals, and then i'm thinking maybe add a switch in which mean you can turn the alternator on to replenish the bigger battery running fans (and possibly the headlights etc).

[GTSBoy]

Your version of my idea makes sense. You'd do enough in and out laps to be able to just use a battery isolator to bring the extra battery on and off charge and probably keep it close to fully charged without having to spend time and effort on manually charging it. Plus, it has the benefit of still being basically streetable without having to worry about charging the second battery manually as well.

[R32 TT]

funnily enough I just replied to another thread about thermos a few down from this.

I suggested that if you have the right ECU, you can have them turn off when the car is above a certain speed (e.g. 60km/hr +) as I do.

You have all the air-flow you require, as soon as you button off and cruise in to the pits or cool down lap they are back on when you actually need them.

Previous to this I also did something based on RPM/Temp. (Because at the time I didn't have a speed signal) In this setup, the fans are off above say 4000rpm when the car it clearly running at speed. But when you are in 5th crusing at 2500rpm, such as during your cool down, - they are on.

All comes down to your ECU capabilit on what you choose.

[TiTAN]

you can't get rid of all the mechanical load on the motor without fully removing the alternator, however you can reduce the load, the more the battery requires, the more loaded up the alternator needs, if you basically tell the alternator to not bother charging the battery at all, you reduce the load hugely.

this is one in use, the eco guys are jumping on board with it, although i think it's kind of stupid as realistically the fuel usage will equal out, a lot of them instead are just manually recharging when they get home and run no alternator at all.

mm, the cost of a switch vs the cost of a larger turbo + support mods and new tune, hard decision lol.

even if we are talking about better off load engine response, for drift that's quite handy, for the effort of flicking a switch after each run, it's worth it.

these are turbo motors with half decent power to begin with. i am sceptical its going to make much of an improvement. though happy to see tested gains on a real dyno not a pants dyno.

running without the alternator and charging the battery off mains is just moving where you get the energy to your electricity bill same as entirely electric cars, most of our power is off coal/gas power stations to begin with so hardly much cleaner.

[GTSBoy]

funnily enough I just replied to another thread about thermos a few down from this.

I suggested that if you have the right ECU, you can have them turn off when the car is above a certain speed (e.g. 60km/hr +) as I do.

You have all the air-flow you require, as soon as you button off and cruise in to the pits or cool down lap they are back on when you actually need them.

Yuh, but again, this is not what he wants. He wants the fans on when he's thrashing it, to provide some cooling, because the car is not necessarily driving straight through the air at high speed, it could be working hard but going sideways fairly slowly.......But he doesn't want them dragging on the alternator.

[blind_elk]

Really, how many kW does an alternator draw from the engine. Not many, I surmise. So I doubt you would ever notice the difference in performance with the alternator switched either way.

[R32 TT]

Really, how many kW does an alternator draw from the engine. Not many, I surmise. So I doubt you would ever notice the difference in performance with the alternator switched either way.

Yes at the end of the day I'd agree with this.. the thermo is taking all of what. 0.5kw ? In that case you may as well run it full time.

[zoidbergmerc]

Seriously, you'd get more gain by taking a shit before you got in the car.

[nisskid]

Why not turn the thermo fans off for 1 minute? Then cruise for 4?

being a drift car, we are driving at some times up to 90 degrees, and on some technical tracks like skid pan or go kart tracks, or hairpins, as low as 30km/h, the thermo's are still effective at these points.

[nisskid]

these are turbo motors with half decent power to begin with. i am sceptical its going to make much of an improvement. though happy to see tested gains on a real dyno not a pants dyno.

running without the alternator and charging the battery off mains is just moving where you get the energy to your electricity bill same as entirely electric cars, most of our power is off coal/gas power stations to begin with so hardly much cleaner.

like i said, even if it's a few kw over the board, we spend more time on the dyno trying to get that peak power through tuning than it would to wire in a switch. more importantly however it's off load response may benefit a decent amount, if so for drift being able to get your revs up high quickly is important (clutch kicks/drops)

[nisskid]

Yes at the end of the day I'd agree with this.. the thermo is taking all of what. 0.5kw ? In that case you may as well run it full time.

i'm looking to run 2x 100w headlights, + 2x 55w lights (drifting in places with no lighting, or poor lighting), twin shrouded thermo's behind the radiator, 2x thermo fans in front of the radiator (1 in front of the oil cooler, 1 in front of p/s cooler), if you think that + all the ignition/fuel pump/accesories/ecu etc etc doesn't chew a bit, then you're kidding yourself. once you consider the inefficiencies of the alternator, it's probably not such a insignificant figure, but hey, that's just my opinion.