Don Terrill’s Speed-Talk

Does anybody run alternators on their cars? I've heard they drop your HP a bit, but running a little 1/2 or track or so does it really hurt?

I guess it really depends on how you car is set up. (electric pumps, fans, etc)
If you run electronic ignition you can probaly argue that having the battery at fully capacity throughout the race will optimize your ignition output and make up for any HP losses.
If you're worrying about losing horsepower due to parasitic loss from the belt, you can always run it off the third member.

Just some thoughts...

If you are running circle track you should have an alt.on the engine .The Hp loss that it use to turn it will not be a great as the electronic ignition or msd will lose in HP due to not enough battery to supply there needs.

I am running a drag car with ignition, fuel pump, water pump, and fan. When all the items are on and making a pass I do not feel comfortable without an alternator.

I feel that the alternator weight is more than the HP loss, I have mine turning at a 1:1 ratio from the crank. It fully charges at roughly 1800-2000 rpm. I can run two time runs, 10 rounds of racing and still have plenty of power.

I do charge the battery before a race but have gone several races without a charge without a problem.

When making a pass everything on, the alternator will charge 13 volts.

I had a belt break one race, removed the whole deal, the car still ran the same numbers.

In short it's the peace of mind. That and I don't have to drag the generator and charger to the track.

As long as your volts don,t drop past 10 volts you will be ok but on the edge.Anything lower and HP will suffer.







mike

If you dont run an alternator, you really need a 16 volt battery, its the volts that count not amps!
Volts=pressure
Amps=flow.
Fully chargerd 12 v battery is exactly 12.66 volts
Fully charged 16v battery = 16.88 volts
Anything over these voltages is called surface charge and will come off the plates very quickly.
Good luck if you intend to go rounds with only a 12 v battery and no alternator.
As you double the voltage you half the current requirement.
Example if you have battery in boot and the starter lead is barely adequate with a 12v battery it will be ok with a 16v battery as the current flowing thru the same lead is less.
Ideal situation is 16 volt battery with alternator charging at 18 volts.
As long as your elec gear is ok with that sort of voltage.
I dont have a problem with MSD, Barry Grant 400, elec water pump, and starter with 18 volts.
Once you hear your race car start on 16 volts you will never go back to a 12 volt system.
I am out of the battery game now, so am not trying to sell product..

In a drag race deal you don't need an alternator with a 16 volt battery.

I data logged voltage, and with an EFI system, Electric water pump, big electric fuel pump, ignition, electric fan on the return road, it would only lose .4 volts from the time I left the trailer, to the time I returned to the trailer..... GREAT batterys. Highly recommended.

Thanks for the responses. I wil run Circle track. So if I Had a 16v battery, i'd have to charge it everytime I raced without an alternator? Generally how much HP do you loose with an alternator?

You can get an alternator that will keep a 16v fully charged.

Generally how much HP will an alternator rob you of? Whats the advantages and disadvantages of an alternator, and charging a battery after every race?

nascardriver0723 wrote:Generally how much HP will an alternator rob you of? Whats the advantages and disadvantages of an alternator, and charging a battery after every race?

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Don't have any hard numbers, never tested with & without & it would depend completely on the equipment you are running & the state of charge of your battery anyway.
If everything was off & the battery was fully charged the answer is in my opinion at least is you would not be able to measure the HP loss,,

Advantages, possible slight gain in flywheel HP
Disadvantages,, having the wrecker help you off the track,,,,

In circle track the real question is do you want to finish the race

Run the alternator,,,

When we dynoed my 502, I wanted to know how much hp the alt. and water pump were using. Now this is on a mild street low rpm BBC turning 6800max.
1st - we ran it with the alt. & water pump, it made 610hp/627tq
2nd - no alt. and elec. water pump, it made 626hp/627tq
So both cost me 16hp.
Never ran it just without the alt., but I'm guessin its about half the lost.
So around 8hp or so, maybe 10hp on a higher rpm motor. But the tq seamed to be uneffected...
Hope that helps

With a nascar tour legal 358, 9-1, 390cfm, MSD 6-ALN, the difference between running off of the alt and running off the battery was 10+ hp more with the alt on!
Plus the tq and hp curves were much smoother with the alt running. (Not a bunch of little valleys in the curves) For these types of engines 10 hp is worth $$$$

I just looked at the MSD website for my ignition system (Digital 6)
It states that it will deliver full output from 9 - 18 volts

So if my batteries fully charged then i would run without the alternator.

Trev

Hmm... I guess losing 10 HP is better then having to have a wrecker pull ya off the track. Thanks..