2.7 Alternator Upgrade

[Banshee]

Typical aint it!!!!! Saw x2 3.2l Elgrande's this morn on the way to work :doh

Rick 125a is awesome!!!!! How much was it?

Mine is being replaced soon anyway as the pulley is squeeking like a goodun' :doh

 

[Lazy-Ferret]

nah that is got from the fuel pump or maybe the ckp sensor, alternator would not be anything like accurate enough for the ECU

That's a result then... I thought I read somewhere on here before about taking the feed off the alternator, and I was thinking that could cause all sorts of issues, if you changed the pulley size.

 

[Banshee]

That's a result then... I thought I read somewhere on here before about taking the feed off the alternator, and I was thinking that could cause all sorts of issues, if you changed the pulley size.

I love it when we're making progress on stuff

 

[Sweety]

Watching this closely:thumbs mines working fine at the min but would like a higher output one:augie

 

[Mobieus_uk]

anyone considered simply getting the alternator rewound for greater output, that way you will be sure it will fit

 

[Lazy-Ferret]

anyone considered simply getting the alternator rewound for greater output, that way you will be sure it will fit

I talked to a local alternator company about that, as they do rewind ones for buses and old tractors, but they said that firstly it would be very expensive, or in their words, not cost effective, and secondly it would make it quite fragile, and too unreliable to put on a 4x4. Not sue why it should be any more fragile than the 125amp one already fitted to most 4x4's though. They said it would be a lot cheaper to do the same as we have been talking about, and just find another that would fit in it's place... which at the time I did not realise was going to be easier said than done.

 

[Banshee]

I talked to a local alternator company about that, as they do rewind ones for buses and old tractors, but they said that firstly it would be very expensive, or in their words, not cost effective, and secondly it would make it quite fragile, and too unreliable to put on a 4x4. Not sue why it should be any more fragile than the 125amp one already fitted to most 4x4's though. They said it would be a lot cheaper to do the same as we have been talking about, and just find another that would fit in it's place... which at the time I did not realise was going to be easier said than done.

Seems we've both done a lot of the same leg work here :lol

I had exactly the same spiel here from a firm I deal with in Wolverhampton

 

[solarman216]

Typical aint it!!!!! Saw x2 3.2l Elgrande's this morn on the way to work :doh

Rick 125a is awesome!!!!! How much was it?

Mine is being replaced soon anyway as the pulley is squeeking like a goodun' :doh

£54 inc delivery, should be here by Friday

re your squeaking pulley, if it is not the belt then it maybe the nut holding the pulley has come loose, so a quick check with a spanner would be good, Rick

 

[Banshee]

I've just had a thought about this driving home.

Rick are you sure that changing the size of the pully won't impact amperage that the alternator kicks out as I'm sure that the smaller the pulley the faster it rotates producing more amperage?

 

[solarman216]

first of all may not need to change size of pulley, would be better not to so as to keep the belt standard, but even if we did change it for a smaller one it will not have any real effect on output, less than 1000 alternator revs = less than full output, 1k to 1.5k = full output, 5k still = only full output, these are approximate values as alternators vary, another point worthy of note is at 125 amps a larger pulley may be required simply to stop belt slip even with the belt very tight, Rick

 

[Banshee]

first of all may not need to change size of pulley, would be better not to so as to keep the belt standard, but even if we did change it for a smaller one it will not have any real effect on output, less than 1000 alternator revs = less than full output, 1k to 1.5k = full output, 5k still = only full output, these are approximate values as alternators vary, another point worthy of note is at 125 amps a larger pulley may be required simply to stop belt slip even with the belt very tight, Rick

I really wish we had a reputation system or thanks system on this site sometimes!!!!

 

[Sweety]

Most alternators kick out their max power from 2,000rpm up over:augie

 

[solarman216]

Most alternators kick out their max power from 2,000rpm up over:augie

alternator revs or engine revs? do not forget the alternator pulley is a good bit smaller than the crank one, I went through many alternators on the boat as engine pulley was on the camshaft and most times at canal cruising speed it only rotated at 400 revs alternator less than 1000 and with a charge controller was pumping out 100 amps all the time, trouble with it was at low revs full output in an oven (engine bay) they barely lasted a year, Rick

 

[Sweety]

alternator revs or engine revs?

:dohEngine revs, have known a couple put out max power a little lower down engine revs wise from 1500rpm. I think on mine it's around 1600-1700rpm. If people do fit larger amp alternators like 125a it'll pay to replace the charging cable to the battery as the standard on is only 70a. I know from reading a lot of car audio forums people have up'ed the charging rate to their battery a lot from replacing the factory thin earths & alternator cable with heavy duty wiring like 0 gauge, if you google the big 3 upgrade loads of info comes up on it:thumbs

 

[solarman216]

I got most of my info from Charles Sterling, Sterling Power products, he explains in simple lingo and to my mind what he does not know about alternators, charging systems and batteries is not worth knowing, Rick

 

[Lazy-Ferret]

alternator revs or engine revs? do not forget the alternator pulley is a good bit smaller than the crank one, I went through many alternators on the boat as engine pulley was on the camshaft and most times at canal cruising speed it only rotated at 400 revs alternator less than 1000 and with a charge controller was pumping out 100 amps all the time, trouble with it was at low revs full output in an oven (engine bay) they barely lasted a year, Rick

According to the T2 spec sheet in the service manual the following outputs for the standard T2 alternator... The thing is, I thought my engine red lines at 4.5K RPM, so I guess these must be the alternator RPM.

With 13.5V energising, it needs a about 1000rpm to start generating, and then goes as follows.
26amp at 1300
58amp at 2500
72amp at 5000

Not sure on the diameters of the two pulleys, but given that info it would be pretty easy to then link that back to engine revs

 

[Banshee]

According to the T2 spec sheet in the service manual the following outputs for the standard T2 alternator... The thing is, I thought my engine red lines at 4.5K RPM, so I guess these must be the alternator RPM.

With 13.5V energising, it needs a about 1000rpm to start generating, and then goes as follows.
26amp at 1300
58amp at 2500
72amp at 5000

Not sure on the diameters of the two pulleys, but given that info it would be pretty easy to then link that back to engine revs

Nice find!!!!!!!!

 

[Lazy-Ferret]

OK, so just popped out and measured them... Alternator pulley is 80mm O/D, and the crankshaft pulley is 150mm O/D.

According to this site, the engine needs to be running at about

550RPM for the alternator to be running at 1000rpm
2700RPM for the alternator to be running at 5000rpm.

So with the standard pulleys, the alternator is roughly twice the speed of the engine.

 

[solarman216]

lots of this stuff is manufacturers sales rubbish, I have not bothered to look at these, I use a DC clamp meter, to check whatever I need, from starting current to charging and glow plug draw, these give you actual figures not theory, once I get this new alternator up and running I will notate revs, amps load etc for you all to ponder on, Rick

 

[rayf3262]

another point worthy of note is at 125 amps a larger pulley may be required simply to stop belt slip even with the belt very tight, Rick

70A alternator requires ~2.0 HP at full output
125A requires ~3.5 HP
Thats around another 1.5 HP through the belt, about 75% more!