no alternator

[dokarex]

The berings are almost gone in my 87 Na Diesel Doka so I removed the alternator today and took it to the local rebuilder.
Holy Cow  I must have picked up 5 or more hp (remember I only have 52 to start with 1.6l na). what a difference without the alt. I know racers run with no alt for this reason I just never thought it would actually make this much difference, on hills that I usually slow down on we just kept going and on a road I usually only barely hit 80kph we easily maintained 100kph.    
Since this is a diesel only the fuel solenoid and the guages use power unless driving at night or blasting the radio but how can we disconnect the alt if we want to with out getting out and removing the belt. Until I get a 1.9 TD I'm tempted to run with out the alt and carry a charger. :evil:    
87 Doka na
97 Jetta TD (wifes "think she would notice if I swapped engines? :twisted: ")
B2600 Kubota only here cause its diese

[burn_your_money]

I drove without an alternator in a rabbit for a few months. I just keep a spare battery on the back seat and a set of jumper cables. I used to swap the battery everytime the one died but that got old fast so I would just hook up the battery using the jumper cables, start it and then pack it all up. You'll kill your battery fast though.

[bert]

If you removed the alternator,how did the water pump run,its on the same belt? well its the same belt in uk  :wink:
Bert

[Black Smokin' Diesel]

Full throttle alt/A/C cutout switch?  There's a thread kicking around somewhere...

Andrew

It has some good info and ideas. I still havent found a big enough closed state relay to kill the alt.
http://www.vwdiesel.net/phpBB/viewtopic.php?t=7460&start=0

[Vincent Waldon]

I should know the explanation to this better, but every book I've ever read about charging systems says "Whatever you do don't run the alternator with the B+ lead disconnected from the battery"... and goes on to talk about ruined diodes, hoards of locusts, global warming, and other evils that will befall you if you do this.

The ideal place to cut out the alternator would be the field windings... much lower current than needing to find a honking big relay on the B+ line, and evidently much safer on the diodes.  As a young lad with a 1969 VW van I had a pull-switch bolted to the stickshift that performed this function for the enviable red light races (when all you have is 57 hp every little bit helps) but that was an era of generators with an external regulator and very accessible field windings.

Lots of modern racing cars still have "Alternator ON/OFF" switches so it must be possible... I'll do a little more digging.

[dokarex]

what about a marine battery selecter switch they have batt1 batt2 and off?

[Vincent Waldon]

It could certainly handle the current, but you'd be taking your chances on the alternator diode bridge.

[tylernt]

I don't get it. The alternator should present little or no parasitic drag when there is no call the charge the battery or power electric accessories. I thought that was the point of the voltage regulator, high battery voltage means reduced field strength and less charging from the alternator? So, I don't see how a cutout switch would help. Feel free to enlighten me though.  

[Vincent Waldon]

Yup, assuming the battery is in good shape a diesel doesn't present much of a load to the alternator... but it does take power to make power... every 746 watts is a horsepower if the alternator is 100% efficient.

I agree... the gains are likely slight.  Disconnecting the A/C would probably have a much higher yield.


Vince

[jtanguay]

well having a clutch like on the a/c compressor would be nice... but then again that draws power...

[MaxHedrm]

Yeah ... a clutch that disengaged automatically until battery voltage dropped to a specified level would be ideal.

[tylernt]

Yeah ... a clutch that disengaged automatically until battery voltage dropped to a specified level would be ideal.

I still don't see how this would recover any HP. The alternator is pretty much already disengaged by the voltage regulator until the battery voltage drops.

[jtanguay]

the alternator is a rotating mass though... surely you could gain more revvability

[Black Smokin' Diesel]

Yup, assuming the battery is in good shape a diesel doesn't present much of a load to the alternator... but it does take power to make power... every 746 watts is a horsepower if the alternator is 100% efficient.

I agree... the gains are likely slight.  Disconnecting the A/C would probably have a much higher yield.


Vince

The alt provides all the power needed to run the car. The battery is there to start the engine and assist in case the car needs more current. With diesels having such low current needs, the battery is pretty much doing nothing 95% of the time.

Would putting the switch on the exciter wire work as well? The thing is, if you kill the alt, you kill the tach, which is a no-no when doing a WOT acceleration. I like the idea of a clutched pulley but then again, no tach unless you use a gas tach with a sensor on the IP sproket.

[jtanguay]

Yup, assuming the battery is in good shape a diesel doesn't present much of a load to the alternator... but it does take power to make power... every 746 watts is a horsepower if the alternator is 100% efficient.

I agree... the gains are likely slight.  Disconnecting the A/C would probably have a much higher yield.


Vince

The alt provides all the power needed to run the car. The battery is there to start the engine and assist in case the car needs more current. With diesels having such low current needs, the battery is pretty much doing nothing 95% of the time.

Would putting the switch on the exciter wire work as well? The thing is, if you kill the alt, you kill the tach, which is a no-no when doing a WOT acceleration. I like the idea of a clutched pulley but then again, no tach unless you use a gas tach with a sensor on the IP sproket.

AHA! that is the first best problem with this mod so far...  you're absolutely right... hmmm