Basic AMP draw study on 98 GTS

[Bolt]

This may answer some questions on what draws power from the battery and how much. I was supprised. I know from now on when I race someone I am turning everything off so my altermator does not steal any of my power. This blows my mind!

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I could not do the test with just the high beam headlights on. It kept blowing my meter fuse at 23 amps.

Just imagine what the numbers would be when you turn on multiple things. AC, Headlights, driving lights, radio You can do the math. No wonder these alternators get hot and they have to be high amperage output.

 

[Madduc]

Very interesting info! I always try to turn off as much as possible when having fun, but never saw the numbers.

 

[eucharistos]

cool info

who woulda thunk it

 

[PowerKraus]

BOLT

[FONT=&quot]I'm an accomplished mechanic, built several blah blah.......and tuned them....shot a rocket to the moon too......anyway. I think alot of myself and know nearly everything.

After an 8 month hiatus from the forum, I looked through the forums tonight and found your article fascinating NEW information. Thanks for taking the time to document and post!

Rob

[/FONT]

This may answer some questions on what draws power from the battery a SNIP the math. No wonder these alternators get hot and they have to be high amperage output.

 

[plumcrazy]

im surprised about the locked and unlocked

 

[Bolt]

im surprised about the locked and unlocked

This is kinda what got me started. I saw a post where someone said their car had less drain when it was locked. Of course I had to prove this to myself. As you see the numbers don't lie.

 

[plumcrazy]

Very strange.. I'd like to hear from mark or Tator maybe as to why.

 

[luc]

This may answer some questions on what draws power from the battery and how much. I was supprised. I know from now on when I race someone I am turning everything off so my altermator does not steal any of my power. This blows my mind!

You realy believe that a couple of HP make a difference on a 450HP car?

1HP = 764 Watts
At about 13.8 V regulated voltage, 764 Watts = 55.36 Amps
But due to friction and eddie current loss an alternator is only about 85% efficient so it take about 1HP for 45 Amps.
Big deal ?

Luc 00GTS

 

[plumcrazy]

who said anything about robbing hp ?

 

[luc]

who said anything about robbing hp ?

maybe you should reread the beginning of the 1st post

 

[Ratical2]

Thanks Bolt! Interesting information and your meter is pretty cool too. My meters stop a 10A. The numbers are much higher than I expected.
Now you know why Electrical Power Distribution is one of the important considerations when designing a car. Because of engine load considerations that affect the mileage rating, the smallest alternator possible is used. So the system designers actually fight over who gets the power.

Thanks again!

 

[Asp Man]

Originally Posted by luc
maybe you should reread the beginning of the 1st post

Or maybe you should. He said power, not HP. I think the intenet was that he didn't want any accesories robbing current.

 

[Asp Man]

Dbl. post, sorry.

 

[Steve 00RT/10]

This is kinda what got me started. I saw a post where someone said their car had less drain when it was locked. Of course I had to prove this to myself. As you see the numbers don't lie.

I would guess Lock / unlocked....are both powering an electric solenoid to engage / disengage the locking mechanism. That takes juice. An uneducated guess would have me think the locked postion is the failsafe or basically 'unloaded' condition....therefore the lower draw

who said anything about robbing hp ?

Luc is correct. Electricity eats up HP. That's the why the AC turns off at WOT

 

[luc]

Originally Posted by luc
maybe you should reread the beginning of the 1st post

Or maybe you should. He said power, not HP. I think the intenet was that he didn't want any accesories robbing current.

Since he mention racing, don't you think the idea was that with no draw on the alternator he would be faster?

Steve:
Regarding the A/C cutting off at WOT

What take of lot of HP is the compressor therefore at WOT the A/C compressor clutch disengage but the lack of airflow is simply due to a bad design.
All the flaps/doors are vacuum operated and under WOT, intake vacuum is very low and consequently the door/flap close and airflow stop.
Very easy to fix with a vacuum canister ( as i did on my car)
I still have plenty of cold air at WOT.
Remember than on an A/C sytem the clutch cycle on and off all the time to regulate termperature/line pressure

 

[Bolt]

Power / HP, Whatever. It was a cool study. I was more after what is robbing electrical juice. Especially at idol. When I turn on everything and come to a stop my car idol really goes way down and it seams like it may stall. But it never does. With everything turned off it does not do that. Hmm,,,,.... Remember, My car is not very normal. Lots of mods.

These cars are so finicky when it come to electrical power (Juice). This is why I did this study. I thought it was kinda cool!


1HP = 764 Watts (cool info) Is this for real?


I picked up the meter at Harbor Freight for $30. It also tests temperature and Db (sound) I thought that may be handy to have in the car when someone thinks their car may be louder than mine.

 

[luc]

Power / HP, Whatever. It was a cool study. I was more after what is robbing electrical juice. Especially at idol. When I turn on everything and come to a stop my car idol really goes way down and it seams like it may stall. But it never does. With everything turned off it does not do that. Hmm,,,,.... Remember, My car is not very normal. Lots of mods.

These cars are so finicky when it come to electrical power (Juice). This is why I did this study. I thought it was kinda cool!


1HP = 764 Watts (cool info) Is this for real?


I picked up the meter at Harbor Freight for $30. It also tests temperature and Db (sound) I thought that may be handy to have in the car when someone thinks their car may be louder than mine.

Your rpm's drop at idle seems more related to voltage than Amps.
Low volts do a lot of weird things with computers, you should check the voltage at idle, with and without electrical load.
yes. 1hp=764W is for real.

 

[Steve 00RT/10]

Steve:
Regarding the A/C cutting off at WOT

What take of lot of HP is the compressor therefore at WOT the A/C compressor clutch disengage but the lack of airflow is simply due to a bad design.
All the flaps/doors are vacuum operated and under WOT, intake vacuum is very low and consequently the door/flap close and airflow stop.
Very easy to fix with a vacuum canister ( as i did on my car)
I still have plenty of cold air at WOT.
Remember than on an A/C sytem the clutch cycle on and off all the time to regulate termperature/line pressure

I guess I never tied the airflow thing together with the compressor being switched off.....but the bottom line is the PCM is programmed to shut the compressor down to put more power to the wheels....like maybe 10-15HP more. I would guess a vacuum fix would circulate cool air already 'made.' ....and last long enough under the few second WOT burst....correct?

Steve

 

[luc]

I guess I never tied the airflow thing together with the compressor being switched off.....but the bottom line is the PCM is programmed to shut the compressor down to put more power to the wheels....like maybe 10-15HP more. I would guess a vacuum fix would circulate cool air already 'made.' ....and last long enough under the few second WOT burst....correct?

Steve

Correct, the evaporator is still cold and therefore the air blowing through it is still cooled.
10 to 15 hp seems to be a goo guess, on a low horsepower car,you can really feel a big difference when the compressor kick in.

 

[Chuck 98 RT/10]

I'm not sure but I think the alternator's draw on engine power is constant therefore rendering accessory usage irrelevant regarding HP. The a/c shuts off at WOT because of the compressor drain on HP not the alternator. But again, that's just a guess. Interesting thread though, thanks for posting.

 

[Steve 00RT/10]

I'm not sure but I think the alternator's draw on engine power is constant therefore rendering accessory usage irrelevant regarding HP. The a/c shuts off at WOT because of the compressor drain on HP not the alternator. But again, that's just a guess. Interesting thread though, thanks for posting.

I think any accessory power needed by the engine involves HP drain. The alternator works like a water level to monitor what the car is drawing to run whatever is turned on. The alternator voltage output remains somewhat constant (above 13.2 volts) , but the juice (amperage) needed to maintain the 'water level' condition varies per the load, AC included. That's why alternators are rated in amps. The Ohms law HP/wattage/amp calculation above applies no matter what.

A 12 volt car battery has 2.2 volts per cell or 13.2 volts, thus the alternator output needs to be above 13.2 to do any charging

Steve

 

[Jack B]

I think any accessory power needed by the engine involves HP drain. The alternator works like a water level to monitor what the car is drawing to run whatever is turned on. The alternator voltage output remains somewhat constant (above 13.2 volts) , but the juice (amperage) needed to maintain the 'water level' condition varies per the load, AC included. That's why alternators are rated in amps. The Ohms law HP/wattage/amp calculation above applies no matter what.

A 12 volt car battery has 2.2 volts per cell or 13.2 volts, thus the alternator output needs to be above 13.2 to do any charging

Steve

The basics:

1. An alternator generates an ac voltage and then converts it to dc thru a rectifier.

2. A battery is charged whenever, the charging source has a higher voltage than the battery voltage. In affect, they sort of equalize.

3. As the demand load (accessories) pulls current (amps) the battery voltage drops and the alternator supplies more of the load.

4. There is a regulator in the alternator that moderates the voltage and therefore the current.

5. The problem (misfires) that the viper has from a low battery voltage is due to a required range of input voltage for the PCM. The PCM has a dc converter circuit that is a dc/dc regulator, it has a min/max range, once the battery voltage drops too far and the regulator reaches it's max output the PCM offsets for injector pulse falls out of range, therefore, the engine instability.

6. The true output power (watts) of the alternator would be Volts X Amps. For input or required power power you would have to increase that number for: the electrical losses across the rectifier; the mechanical losses across the belt; the rotating losses of the alternator; lastly the I2r losses of the circuit itself. If I were to guess, the inefficiency of the electro-mechanical circuit could be 50%-100%.

As an estimate, if the alternator pulls 100 amps at 14 volts, that would 1400 watts. Double that for losses and you get 2800 watts, divide that by 746 and you get approximately 4 hp. Losses might be higher, but, we should be in the ballpark.

The last paragraph has a lot of conjecture, but, the theory is accurate.

 

[Bolt]

This is all good stuff and the detail here is great. So when we put the Paxton setup on these cars we need to swap out the crank shaft pulley. As it is smaller it tends to spin the alternator pulley slower. Hence a smaller alternator pulley would make up for the difference in diameter in crankshaft pulley. I think this is all boaderline close and the crank pulley is not much smaller. Things that make us go Hmm,,,.... I just might try something. Just for fun. Yes smaller alternator pulley.