j.kenzie@sbcglobal.net

Thanks, Alan.
I came across the Quicktifier external bridge rectifier system. Does that provide any of those parts?

http://alternatorparts.com/quicktifi...rectifier.html

Thanks,
Dave

dr bob

Hmmm. Taking the diodes external won't change anything really, except keep the diodes cooler. The forward voltage drop through standard silicon diodes as still about 0.65 Volts at virtually any temperature they will survive at in the car. Meanwhile, the regulator includes "temperature compensation" intended to protect the alternator and battery from overheating from too much current flow. Adding heat shielding will help keep shield from extra heat from the exhaust, but you still need to carry the internally-generated heat away. That means colder air from somewhere, especially on belly-panned cars. I suppose a little fan to push some cold air through the hose at hot idle would help, but only so long as it's not a restriction at speed. I'm not sure there is any pressure built up in the area under the headlight where the hose sits, instead the circulation is air drawn by the fan on the front of the alternator. So at hot idle when you really need some cooling, that's when the circulation is lowest.

mike77

Would sticking something like this along the side of the alternator facing the engine work? Or would it lock heat in?

http://www.thermotec.com/products/14002-thermo-shield.html

j.kenzie@sbcglobal.net

Hi Mike,
I think you have to look at the airflow design of your alternator. Mine has dual fans which suck in from each end of the case and expel from the sides. If you stick a barrier to the side facing the engine, you may reduce airflow, while blocking some radiant heat. Might work, might not.
I am thinking to put the radiant barrier on the engine side, and leaving an airspace near the alternator.
I have ordered some stuff and will drop my alternator and explore, maybe next weekend.
Will post pictures then.
Thanks,
Dave

mike77

Mine is stock so airflow is from the stock air duct. Just been reading about some of the 3M products, not the one linked above. The aluminium tapes can reflect and dissipate heat, so insulating heat in shouldn't be a problem. The 3m site doesn't work well on my phone so I'll take a proper look at their products later

j.kenzie@sbcglobal.net

I see, Mike. I would still leave an airspace around the alternator case, and put the heat barrier close to the engine/exhaust area. Not sure the difference is worth much, but maybe.
Good luck,
Dave

Alan

The point was to move firstly the regulator and secondly the rectifiers external. Doing this allows a much less aggressive temperature derating. Moving the regulator alone can do this - but the temperature deration serves a purpose to protect the alternator - especially the rectifiers - so moving them too allows them to be protected from over temperature and also to keep the windings cooler too.

The rectifier forward voltage drop is likely to be around 1v at operating currents - it's a combination Tj & IR drop total at rated loads - this of course means larger internal power dissipation. These rectifier diodes are not particularly large devices (at least not compared to large scale power devices) - the packaging constraints are very limiting.

Moving stuff out is a very complicated thing to implement though for sure - and the commercially available 'Quicktifier' seems to be a very odd hybrid solution here (I seriously question the value).

Modern alternators are very conveniently packaged - but its always a real compromise having all that heat generating equipment packed in so close to major heat sources on the vehicle. Idle is always the most challenging time, you need a large rotor field due to the low rotation speed, the airflow is lowest, the belt is under the most load yet the output demands hardly change. Often you have been cruising at speed - then have to stop at idle - at this time the residual thermal load is still very high and this spikes the ambient & coolant temperatures & heat radiation right at the time alternator cooling flow is at its worst, likely then the cooling fans will kick in and the alternator is challenged even further by its biggest current load contributors.

Alan

j.kenzie@sbcglobal.net

Thanks Alan,
The Quicktifier moves diodes to an external fan cooled box, in parallel to the alternator's original diodes. This seems like it would reduce alternator temperature to some degree, and thus avoid the temperature compensation needed for a hotter alternator. It is a fairly simple and affordable solution, which is a compromise over your complete design, but do you think it might be worthwhile?
Dave

Alan

From its connection diagram one can see that it is a fan cooled rectifier only, there is no field connection so it does nothing to help the regulator temperature compensation issue. I think for us this is by far the bigger issue - so I'm not sure this will really help much at all. It could help reduce the IR drop in the stock rectifier diodes and maybe as a result reduce internal power dissipation - but it won't eliminate it . So if the regulator still gets hot it will still derate output voltage anyway - so I doubt you will really see any major improvement from this. But maybe worth a try if you are willing to risk it.

Alan

Jim Devine

Didn't find the dimensions, but possibly a blower like this with ducting might work. Nascar cars use them to cool brakes- cheap too. Might help in low speed or stuck in traffic.

http://www.roushyatesparts.com/detma...754-blower.htm

or this one, looks physically smaller:

http://www.ebay.com/itm/Attwood-1731...item5d506d5cb7

j.kenzie@sbcglobal.net

Thanks, Jim. That looks like a part of the kit I ordered. Yours would have been cheaper, but the kit has some nice features too.
Dave

LT Texan

Are you the only one?

I've got the "Camaro V-6" alternator and it charges like crazy, until it gets heat soaked.

Ducman82

Same one I have. And it does get heat soaked for sure, but a shroud and hose did not make much of a difference from the numbers I got..... If any

Carl Fausett

Thanks Alan. Your description was a lot more detailed and accurate than mine. I was painting in broad brush-strokes. Good info, thanks for the correction.

Seems most site idle as the problem. Low rpm's, low air flow across the alternator, high draw for the electric fans = a lot of heat generated. The alternator has its own fan blade under the pulley to blow back over the unit.... two ideas: 1) a better fan design so that this fan actually moves more air at low speeds? or 2) nudge your idle speed up a little? (manual trans cars only) Then the alternator makes more amps, the electric fans spin faster, more air is moving from the pulley-mounted fan too - all good. I'm not talking a lot - 100 rpm maybe - it might just be the nudge it needs.

The thing about option #2 is it costs nothing to try, and if it doesn't work or you don't like it, you can put it back the way it was. No harm, no foul.

Just a thought.

j.kenzie@sbcglobal.net

Thanks, Carl. I tried bumping up my idle rpm's on my automatic car. In gear the rpm's go back to 700 or so. I am guessing that has to do with the nature of the torque converter. I went to the smallest alternator pulley I could find 2 1/8", and it seems to help some.
Dave