260Z Guy Posted January 15, 2008 Share Posted January 15, 2008 I have been noticing that when my '74 260z is idling the air vents run signifigantly slower then when I am driving/accellerating. The same goes with my headlights(dimmer). I have the idle set at about 750rpm and the car does have a mild cam but it almost seems that the difference in power that the electronics are recieving is greater than the 2-2.5v difference in the charging and battery voltage. I have not checked the alternator's charging voltage yet but I wanted to see if this is a common problem. I have considered doing the AC Delco alternator swap if it is necessary. I plan on retrofitting some HID's and I just want to make sure the voltage is where it should be so they don't flicker. Any ideas? Quote Link to comment Share on other sites More sharing options...
woldson Posted January 16, 2008 Share Posted January 16, 2008 How are the electronics at 1000 rpms? 12v systems suck because of the low voltage (this means ALL connections must perform extreamly well) but the trade off is safty. Where are you able to check the charge and battery voltage relative to the checking of electronics?? Quote Link to comment Share on other sites More sharing options...
260Z Guy Posted January 17, 2008 Author Share Posted January 17, 2008 I was just referring to the batterie's charged voltage (12v) and what the alternator should be charging at when the engine is running (14.4v). I wonder if it might be the voltage regulator, mabye it is set to low? Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted January 17, 2008 Share Posted January 17, 2008 I'm also curious what the actual voltages are at idle and off idle and at what RPM that a change occurs. What size are the pulleys? From what I've been looking at with the stock crank pulley it may be what I would consider small, and if the alternator pulley is on the larger size this will cause the stator speed to be slow, and have a low charge rate or turn "off" completly, running solely on battery. A 2 Volt difference is huge, about 15% from 14V optimum. That's a large difference, and will severly effect the performance of electrical components. On top of that the stock S30 alternators are rather small, from the information I've seen, less than 60A for the largest, if I've read correctly. This may have been enough for a carb equipped car, running the heater fan on low, and minimal lights, but will usually severly suffer when the defroster is on, or the fan set to high, or even the headlights on. Also realize that at idle the available current capabilty is quite a bit lower, on average about 50% of full rated output, whihc is usually a cold output (more on that later), so now were down to about 30A. Most lighting systems with the headlights on and on low beam will be upwards of about 12 to 15 amps, so about half of the available output, not much left for running the car, or or the fan. More on that cold rating. When electronics are cold they will transfer energy (voltage) much easier than when warm, and some companies will use this rating to make thier product, in this case the alternator sound more powerful than it is. The important rating is the hot rating, the one that is rated onec the alternator is actually at operating temp. In most alternators this seems to be between 70 and 80% of the cold rating, so that 60 amp alternator is now only 42 to 48 amps, take into account that idle output now it's down to about 21A to 24A, not much at all. I would recommend an alternator upgrade, Delco alternators seem to be the most commonly swapped into place of other alternators, heck I even had one on my '81 Honda Prelude, yes it ran backwards and yes it charged just fine. I didn't have a problem with cooling but it could have due to the fan being installed for a clockwise rotation of most engines. Installing a larger alternator is useless without also upgrading the charge wiring, commonly refered to as "The Big 3". This is the charge lead from the Alternator to the Battery positive terminal, a ground form the engine block or Alternator case to the battery negative, and from the chassis to the battery negative. I reccomed 4 AWG for this, even on a vehcile that doesn't have a reason for a high current draw, like a stereo, or lots of other electrical upgrades. The extra capacity of the wire size will ensure there will be no reason for a lack of charging capacity. Quote Link to comment Share on other sites More sharing options...
woldson Posted January 17, 2008 Share Posted January 17, 2008 Nice write up six shooter! Quote Link to comment Share on other sites More sharing options...
badjuju Posted January 17, 2008 Share Posted January 17, 2008 an upgraded alternator should be one of the first things done to a z imo. and a battery, and new big wires. see above for a definition of "the big wires". wires, battery, alt. $250, but it will keep your mind off your electrical system (unless you have a 260... lol) Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted January 19, 2008 Share Posted January 19, 2008 I should also mention that you will need to at the very least bypass your ammeter when installing a larger alternator. The Ammeter will be matched to the size of the alternator and when you upgrade the Alternator will be capable of providing more current than the guage can handle, this could be a bad situation. To Bypass it, the simple way at least would be to disconnect the charge and load leads from the guage and bolt them together, using a lock washer, and then insulate well. Wraping electrical tape and heatshrink around this connection will do the job. I would recommend a volt guage as a replacment. Quote Link to comment Share on other sites More sharing options...
260Z Guy Posted January 22, 2008 Author Share Posted January 22, 2008 I appreciate all of the info six shooter, I will have to do more research into the alternator swap and Big 3 upgrade. That will probably be good for my application since I want to upgrade the stereo in the near future as well. Quote Link to comment Share on other sites More sharing options...
Daeron Posted January 23, 2008 Share Posted January 23, 2008 I should also mention that you will need to at the very least bypass your ammeter when installing a larger alternator. The Ammeter will be matched to the size of the alternator and when you upgrade the Alternator will be capable of providing more current than the guage can handle, this could be a bad situation. I hate to doubt you, but this is the first I have ever heard of this among all the alternator conversions I have looked at.. Granted, its possible that I overlooked the detail; I have a 75 280, which DOES have an ammeter, but the 76 and up 280s have voltmeters instead. It *may* be that I've overlooked a subtle part of the conversion on a 240, that has not been properly covered on the conversions for a 280 that I have read, because later 280s don't have the ammeter.... BUT, as I said, I haven't heard this before. Why did I not notice a difference when I switched from a 65 amp alt to a 55 amp alt? both were listed as replacements for my model at the parts store and the $15 difference made a difference at the time. Is there no way to keep the ammeter? Isn't there a shunt unit that could be changed out to accommodate a higher amp alt? Personally, the Maxima 90 amp upgrade is the no brainer in my book. Still Nissan/hitachi componentry, bolts up in the stock location, just needs a different pulley on it, and a newer style plug (new plastic = less bad) It is an internally regulated unit, so it will take some minor re-wiring. If you hunt around you can find more information. I also like to recommend changing the charging wire for the alternator anytime you upgrade an old car with a higher amp unit. Half the time, the issue stimulating the swap in the first place can be remedied (to a great extent, at least) by simply installing new battery cables, a secondary grounding strap, and replacing the alternator charge wire. I cannot recall if thats the main positive wire on the back, attached with a lug to the BATT post, or if it is the heavy wire in the T-plug, but if you dig into some of the write ups that have been done both on this site and elsewhere regarding alternator upgrades, you should find the info you need. Hope this helps, and good luck! Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted January 23, 2008 Share Posted January 23, 2008 Are you sure you didn't go from a 55A alt to a 65A alt, that would make more sense than going down in capability. Anyway. The stock guage would likely be no less than 60A capable, probably over the 65A if that was an available size. I have seen some smaller, but are usually used in very specific applications. I have seen as low as 30A capacity for automotive and related. Smaller are usually for monitoring specific electronic circuits. The extra 10A of capability most likely wouldn't be a problem, since I doubt you are using the full capacity, and will most likely stay below even 50A, unless you have upgraded to an electric fan, or other power hungry devices AND feeding them off the fuse box or down stream from the Ammeter. If you connect direct to the battery for a main power source, you won't max out the Ammeter, since the load will not be running through the Ammeter. I have not read an alternator upgrade guide that didn't mention changing or swapping out the ammeter for a voltmeter, in cars where that would be applicable. It may also depend on how the ammeter is connected in the system. Some cars had the alternator ran through the ammeter, other had the alternator connected to the battery and then only the vehicle electrical system running through the ammeter. Yes, there are shunt type ammeters, if you really feel the need to know how many amps are being drawn, personally I view that as more of a "bling factor" than anything useful. When talking about high current draw you're not really going to notice any changes that would indicate a problem, until it's too late. A volt meter on the other hand is much more useful in knowing how many volts are currently available in the system and if there is a change is easier and more quickly noticed than a small change in current draw that goes along with a drop in voltage. Pulling out the Ammeter is going to be one of the first things I'm going to do to my 240 when I get it, as I have a stock voltmeter coming with it. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.