Chris Abel Posted February 27, 2008 Share Posted February 27, 2008 I want to fit a 80amp 24v alternator to my 200 tdi and running off the aircon belt, I know that the standard alternator uses 10mm belts and can't cope with 100 amp 12v alternators under heavy load, obviously the wider and deeper 13mm aircon belt can take the extra load but how much extra load can be put on a 13mm belt? If i were to increase the diameter of the alternator pully it will increase the belt contact area which would allow more power to be transfered without slipping. Quote Link to comment Share on other sites More sharing options...
sgnas Posted February 27, 2008 Share Posted February 27, 2008 If i were to increase the diameter of the alternator pully it will increase the belt contact area which would allow more power to be transfered without slipping. This would reduce your output as it would go round less often (gearing) Particullarly a problem at idle speeds. Oh..and worse than fag packet calcs. Air con can take ~3% of engine power, say 3hp ~ 2200watts 100amps at 24v = 2400watts Assuming the designers have some sort of safety factor, that looks ok to me * disclaimer, I've looked nothing up and am just using vague memories as figures Quote Link to comment Share on other sites More sharing options...
cipx2 Posted February 27, 2008 Share Posted February 27, 2008 A rule of thumb says A/C takes about 5 hp from the engine. It's not a percentage of the engine power anyway. A rule of the other thumb says an alternator takes: (Amps x Voltage) / 745.7 x 1.15 the result being in HP. So a 100A 24V alternator would take 3.7 HP from the engine. Quote Link to comment Share on other sites More sharing options...
Orgasmic Farmer Posted February 27, 2008 Share Posted February 27, 2008 Hi Chris I just used whatever I could find to fit. The alternator is a 120 Amp from a Renault laguna (£5 on the Bay) and the bracket was made to fit the belt (which was the shortest Steve had on the shelf!). So far so good and no problems to report Quote Link to comment Share on other sites More sharing options...
Guest diesel_jim Posted February 27, 2008 Share Posted February 27, 2008 Some of the military wolf XD's have twin alternators, run off a serpentine belt using a mixture of AC and specific pullies. the belt is quite narrow (can't remember if it's 5 or 7 groove) and they work fine. i fitted a similar system to my 300Tdi 90, using a 130amp alternator, with a pretty small pulley (only because that;s what i had kicking around) and it never suffered from slip at all. obviously the 200 uses a V belt, but i also ran twin alternators on my old 200 and that worked fine as well. If you're really worried, you could graft on the twin pullies like the military 2.5 diesels and the series 3's used. Quote Link to comment Share on other sites More sharing options...
Chris Abel Posted February 27, 2008 Author Share Posted February 27, 2008 Some of the military wolf XD's have twin alternators, run off a serpentine belt using a mixture of AC and specific pullies. the belt is quite narrow (can't remember if it's 5 or 7 groove) and they work fine.i fitted a similar system to my 300Tdi 90, using a 130amp alternator, with a pretty small pulley (only because that;s what i had kicking around) and it never suffered from slip at all. obviously the 200 uses a V belt, but i also ran twin alternators on my old 200 and that worked fine as well. If you're really worried, you could graft on the twin pullies like the military 2.5 diesels and the series 3's used. The most obvious option is to change the 200tdi's V pullys to 300 tdi multi groove and modify the belt tensioner to fit. but its quite alot of work and if i can get away with running a 80 amp 24V alternator on a 13mm V belt that would be far easier! Quote Link to comment Share on other sites More sharing options...
sgnas Posted February 27, 2008 Share Posted February 27, 2008 I probably have book of tables somewhere that will tell me what power a 13mm V belt can transmit. But he "rough" calcs put the load within the design of the AC system belt. I like "rough" maths Now, are we going to "finite stress analysis" the bracketry or use some box and angle from the workshop? Quote Link to comment Share on other sites More sharing options...
David Sparkes Posted February 27, 2008 Share Posted February 27, 2008 Note the notched belt in the pictures, The advantage of this design is that the belt is more flexible, thus wrapping better around small pullies, and being able to transmit more power, than a conventional V belt. Thus, if sticking with a V belt, as opposed a multivee serpentine belt, try to find a notched belt. HTH Quote Link to comment Share on other sites More sharing options...
simon red90 Posted February 28, 2008 Share Posted February 28, 2008 The most obvious option is to change the 200tdi's V pullys to 300 tdi multi groove and modify the belt tensioner to fit. but its quite alot of work and if i can get away with running a 80 amp 24V alternator on a 13mm V belt that would be far easier! ou'v said i yourself, stop being lazy and get your engineering hat on! planned mod for my truck. i'll let you know how i get on. dont forget, it's only the water pump and pas pump, pretty straight forward... Quote Link to comment Share on other sites More sharing options...
Scotian Posted February 28, 2008 Share Posted February 28, 2008 Chris.. Could you explain in more detail about putting 300 Tdi pullies on a 200tdi? Its the only thing I dont like about the 200Tdi and I need to put a more powerful alt on too. Can I just buy the pullies and stick them on the spindles? or is there much egineering involved.. and what exactly would I need to do with the tentioner? Quote Link to comment Share on other sites More sharing options...
western Posted February 28, 2008 Share Posted February 28, 2008 Chris.. Could you explain in more detail about putting 300 Tdi pullies on a 200tdi? Its the only thing I dont like about the 200Tdi and I need to put a more powerful alt on too. Can I just buy the pullies and stick them on the spindles? or is there much egineering involved.. and what exactly would I need to do with the tentioner? I have a 100 amp Marrelli alternator on my 200Tdi driven by the standard notched Vee belt never had any problems with belts breaking or not doing the job. Quote Link to comment Share on other sites More sharing options...
simonr Posted February 28, 2008 Share Posted February 28, 2008 As a rule of thumb, the most you can reasonably put through a regular V belt (13 or 10mm) is about 3hp - but at 3hp it will be trying to catch fire. 3Hp is roughly 2.2kw = 180A If you allow a safety margin so that it will not be trying to catch fire - I would guess at 100A being about the limit. A PolyVee (serpentine) vehicle belt can be good for up to 8hp or up to 500A - so, say 250A with some margin. Si Quote Link to comment Share on other sites More sharing options...
steve_d Posted February 29, 2008 Share Posted February 29, 2008 Hi ChrisI just used whatever I could find to fit. The alternator is a 120 Amp from a Renault laguna (£5 on the Bay) and the bracket was made to fit the belt (which was the shortest Steve had on the shelf!). So far so good and no problems to report Am I reading these photos correctly? Looks to me as if the alt is being driven from the A/C pulley. If this is the case then the A/C belt is having to carry the load of both A/C and alt. putting its load calcs way off the scale. Steve Quote Link to comment Share on other sites More sharing options...
Orgasmic Farmer Posted February 29, 2008 Share Posted February 29, 2008 You see correctly, though the AC is only used for on-board air and as such may run for about 5 minutes every few hours of driving, and certainly not at a time of high current draw (like winching). Anyway it survived a challenge event and plenty of driving round the woods here with no problems as yet (unlike the standard diffs which seem to pop everytime I go out!). Quote Link to comment Share on other sites More sharing options...
simon red90 Posted February 29, 2008 Share Posted February 29, 2008 Chris.. Could you explain in more detail about putting 300 Tdi pullies on a 200tdi? Its the only thing I dont like about the 200Tdi and I need to put a more powerful alt on too. Can I just buy the pullies and stick them on the spindles? or is there much egineering involved.. and what exactly would I need to do with the tentioner? the crank pulley goes straight on. as does the water pump (i think, not yet tried it) alternators are obvious. power steering pump is the only one you have to make, or find. i'd say, for most, making ormodifying a pulley is a pretty tricky but well worth it. Quote Link to comment Share on other sites More sharing options...
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