Voltage Drop at WOT?
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also the a/c is controlled with a clutch, no think of the stator and rotpr as a clutch in the alternator,look it up ford has been doing this for years, and i work for porsche as a tech and they also do the same thing
Well, if we can see the reference from Delphi, then I'd like to see it. Interesting. I'd like to learn more. I know you can turn on and off the compressor. It's got a clutch, but never knew they could with the alternator.
http://en.wikipedia.org/wiki/Alternator
Could be. At higher RPMs, some alternators can self-excite. This doesn't mean that the alternator turns itself "off." The engine needs electricity to fire the spark plugs. The faster the engine turns, the more the spark plugs fire. The more the spark plugs fire, the more electricity is required. The alternator can not stop working at the point of the highest electrical demand!
You should check with your brother again on this... I'd bet that its just the exciter.
Nope, the alternator turns a winding through a magnetic field. You have generators and motors mixed up here. The process of turning the alternator through the magnetic field takes force to accomplish.
Sure, if you can self-excite, you can turn off the exciter and safe some hp. But again, this doesn't mean that the alternator is no longer producing electricity, its just doesn't need the extra help from the exciter circuit.
THIS, THIS, THIS! is a great point. If an alternator is failing, the voltage should drop slowly as the battery drains. The OP's problem could just be a loose wire that is getting knocked around as the engine kicks at high RPM.
Could be. At higher RPMs, some alternators can self-excite. This doesn't mean that the alternator turns itself "off." The engine needs electricity to fire the spark plugs. The faster the engine turns, the more the spark plugs fire. The more the spark plugs fire, the more electricity is required. The alternator can not stop working at the point of the highest electrical demand!
the reason the pcm does this is due to acc drag on the engine i will find the actual delphi engineering study from my brother and they found this to be woth a total of 7 hp at wot also newer cars dont do this cause newer alternators are pwm and the ezcite circuit is actually turned off and on in a percentage
THIS, THIS, THIS! is a great point. If an alternator is failing, the voltage should drop slowly as the battery drains. The OP's problem could just be a loose wire that is getting knocked around as the engine kicks at high RPM.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Furthermore, the truck alternators may be a superior design, and obviously have provided some relief for some people having charging issues, but it's not getting at the original root of their problem IMO. These engines/cars were able to charge adequately (albeit a bit low at idle with a full accessory load) with stock electrical systems and stock charging components when new, so unless you've added additional load or are using a poor quality rebuild, then the issue is more than just charging capacity of the alternator - and the higher output truck units are likely just masking other issues. I think more often than not, the real issue is people getting rebuilds that are not of the same quality as the OEM original alternator. I've had lots of disappointing rebuilds from retail parts store chains over the years myself.
Last edited by RPM WS6; Apr 25, 2012 at 12:06 PM.
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Verdad Gallardo Furthermore, the truck alternators may be a superior design, and obviously have provided some relief for some people having charging issues, but it's not getting at the original root of their problem IMO. These engines/cars were able to charge adequately (albeit a bit low at idle with a full accessory load) with stock electrical systems and stock charging components when new, so unless you've added additional load or are using a poor quality rebuild, then the issue is more than just charging capacity of the alternator - and the higher output truck units are likely just masking other issues. I think more often than not, the real issue is people getting rebuilds that are not of the same quality as the OEM original alternator. I've had lots of disappointing rebuilds from retail parts store chains over the years myself.
TECH Resident
Joined: Nov 2011
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From: NJ
I'm about 100% sure this does not happen, unless I missed something in engineering school. The only way you are going to "turn it off" is to stop it spinning, so unless you're car has a accessory belt that the pcm can shut off at any time, there would be no performance gained. You are still spinning the alternator. MAYBE the regulator could cut the voltage at high rpm but there is no need. Nothing is gained.
Joined: Nov 2001
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From: Schiller Park, ILL Member: #317
Anyone that wishes to test this can do so quite easily and see for themselves if they have a comprehensive OBD scanner.
TECH Resident
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From: NJ
I can't speak for every/all applications, but I can say that this is not how the LS1s work. I've run many scan logs of WOT voltage in the past, due to an issue I was diagnosing several years ago, and I can tell you that alternator output does not drop off to nothing or near nothing at WOT with a properly working system (LS1).
Anyone that wishes to test this can do so quite easily and see for themselves if they have a comprehensive OBD scanner.
Anyone that wishes to test this can do so quite easily and see for themselves if they have a comprehensive OBD scanner.
Well, I guess I learned something new today. That is can be turned off so to speak. I would like to see some real world testing numbers of how much is gained by doing this. 1ltcap says 5hp, but is that by removing it from the belt all together, or just by so called turning it off?
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From: NJ
Well, I guess I learned something new today. That is can be turned off so to speak. I would like to see some real world testing numbers of how much is gained by doing this. 1ltcap says 5hp, but is that by removing it from the belt all together, or just by so called turning it off?
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From: NJ
If you knew that F-bodies don't do it, then why the fck would you come in here talking about it and just trying to confuse everyone. Absolutely no relevance to this topic. That's like someone asking, "What company had the first variable displacement prototype," and you go and tell 'em, "Well Honda started doing their version of it in 2005."