Stronger altenator options?

[A80Avant]

Im interested in getting a stronger altenator for the rs2.is there any info for this? has anyone used a specific model before?

thanks

[S2central.net]

Probably best chatting with a Bosch specialist - one of those guys that refurbs alternators... From memory there was only a 90Amp and 120Amp alternator for the S2/RS2 depending on what options were fitted.

[Jamo]

Yep 120 amp if you had aircon, i've looked into this and the best option is to have the alternator rewired to 200amps

[A80Avant]

great! 120mps sounds great.what do you mean rewired for 200amps though??

thanks

[Jamo]

Haven't you got the 120 amp alternator? then it was standard on ABY / RS2 then again that means nothing I remember a few cases on here where the wrong alternator was on the car ala Alastair C

Rewiring is when you send your alternator to a specialist and they rewire the coils so it produces a greater charge

[A80Avant]

oh i see.
so you can do that with the 120amp alternator? would the rewiring mean that there will be greater hp draw as well?

I think mine has the 90amp one.But ill have it checked and make the changes accordingly.Aiming to get the absolute perfect idle on all conditions basically and this is one of the things needed

[Jamo]

No change in bhp just greater output per rotor revolution.

[S2central.net]

I'm pretty sure that as load (current draw) on the alternator increases then there is greater load placed on the engine to sustain the higher output from the alternator... Or more simply put - you cannot create energy from nothing - ask one Isaac Newton or Albert Einstein.

This is why we have ECU controlled ISVs so that more/less air can be metered in at idle to cater for differences in loading.

This is also why we have aircon status signalling to the ECU so that it quickly compensate for loading at idle due to the additional parasitic losses from compressing the refridgerant.

[S2central.net]

An alternator generating 90Amp of load at ~14V reflects a nominal power of 1.26kW - lets round that up to 1.5kW required by the engine to cater for alternator efficiency and heat loss.

Running a full load of 200Amp takes us into 2.8kW nominal power output - probably well into 3kW loading on the engine...

Worth remembering the ABY has 169kW in stock form.

The lower the current draw on the alternator then the more power at the flywheel.... You wouldn't do a power run on a dyno with aircon turned on for example...

[S2central.net]

A good way ti prove this ain't a load of old tosh is to run up your car on VAGCOM and look at the LOAD parameter that reflects the amount of air being drawn in... Run a warm idle test with all your electrics off - then watch the LOAD parameter increase when you turn on the ac, lights up full, wazz your cabin fan on full blast and wind up the bass on your booyakasha Saturn V subwoofer. All without touching the throttle pedal.

[Jamo]

In an alternator the sap of bhp is not from the coil size of the rotor but on the bush contact to the rotor during revolution, if that is static there is no more parasitic load.

[S2central.net]

Do the VAGCOM test if you don't believe me... The factory manual actually reminds the operator to ensure all high electrical loads are switched off when considering the MAF signal. I ain't making this **** up !

[Ross]

Surely the more power that the alternator is generating, the more resistance there is to turn the motor? That's what it is harder to turn over a big dynamo with your hand... less coils = less resistance. Remember that's not just resistance in the bushes, but also the opposing magnetty force thing as a result.

I am just making this up off the top of my head btw, thinking about conservation of energy, so i could be wrong

[Jamo]

Surely the more power that the alternator is generating, the more resistance there is to turn the motor? That's what it is harder to turn over a big dynamo with your hand... less coils = less resistance. Remember that's not just resistance in the bushes, but also the opposing magnetty force thing as a result.

I am just making this up off the top of my head btw, thinking about conservation of energy, so i could be wrong

You have to be careful with the amount of coils as there will be less coils with a larger diameter coil

I cant see how it can drain more hp than the standard alternator else Audi would publish different bhp figures for cars with a 90 amp alternator and 120 amp alternator

[S2central.net]

Yes Ross - you must be an Engineer !

Extra energy must come from somewhere to cater for the increase in mechanical load that the alternator places on the engine when there is a large current draw... This would reduce the engines idling speed if it were not for clever things like ISVs, MAFs, ECUs and such like...

Ever driven an old tech car - with a carb, points and distributor ?
Then you can see/feel the reduction in idle speed because of the extra load - used to have an old Astra that wanted to stall every cold morning when I had heaters/demisters on...