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 Post subject: Adjustments when disabling alternator on WOT
PostPosted: Sat Jan 05, 2013 8:34 am 
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Joined: Sat Jul 21, 2012 3:25 am
Posts: 8
ECU Model: S80 Pro
Hi,
Is there experience on the forum of + & - of disabling alternator charging on full throttle?

What is a realistic max gain?
My rough calcs were 1hp per 30A draw (assuming 50% efficency) so 1-2hp on the car I'm working on which means its hardly worth the effort.

Downsides?
I've heard of needing to have a voltage compensation table to adjust the injector duration - is this what is needed? Any other considerations?

Application is S80, 4 cylinder natasp duratec with 1 or 2 sets of batch fired injectors, wasted spark coil pack. Obviously thinking of using a spare Aux output on the S80 to drive a relay at throttle > 90% and interrupt the alternator's rotor field current supply.

Thanks
Stuart


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 Post subject: Re: Adjustments when disabling alternator on WOT
PostPosted: Sat Jan 05, 2013 8:53 am 
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Joined: Tue Aug 09, 2011 2:54 pm
Posts: 318
Location: Stevenage
ECU Model: S80 Pro
Distributor: Roverdose
im sure there was a debate like this already, maybe on the old forum. lost of heated opinions, no real world figures.

i like the idea and im sure there was a company maybe 10 years back actually making something that would do just that. as they arnt here now nor anyone else doing the same thing.

so the conclusion i have is that its not going to make any difference.

Drew


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 Post subject: Re: Adjustments when disabling alternator on WOT
PostPosted: Sat Jan 05, 2013 9:16 am 
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Joined: Sat Jul 21, 2012 3:25 am
Posts: 8
ECU Model: S80 Pro
Thanks - I did find this thread Battery compensation tables, specifically coil dwell table - as you say few hard figures but a general feeling of there's only small gains to be had.

Any other views and hard numbers from experience appreciated!

Thanks
Stuart


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 Post subject: Re: Adjustments when disabling alternator on WOT
PostPosted: Sat Jan 05, 2013 12:26 pm 
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Joined: Tue Aug 02, 2011 12:08 pm
Posts: 2896
Location: Norn Iron
ECU Model: No ECU
In theory yes, if all battery compensations will ensure fuel, sparks etc all remain the same then there may be very very small gains to be had.

But power drop also affects fuel pump flow too, so that needs to be considered.

It's one of those things that may yield something, but is it really worth it ? Are you really at that extreme where you're looking for a fraction of a HP ?


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 Post subject: Re: Adjustments when disabling alternator on WOT
PostPosted: Sat Jan 05, 2013 10:44 pm 
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Joined: Wed Jul 27, 2011 5:30 am
Posts: 571
Location: New Zealand
ECU Model: S80 Pro
A lot of oems are now controlling the alternator with the ecu and limiting the charge rate under certain conditions... sounds like more hassle than it's worth for most aftermarket applications to be honest.

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 Post subject: Re: Adjustments when disabling alternator on WOT
PostPosted: Sat Jan 05, 2013 11:16 pm 
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Joined: Sat Nov 12, 2011 6:24 pm
Posts: 96
Location: Montreal, Canada
ECU Model: S100 Pro
Firmware Version: 61
MSS54 (Siemens) runs the BMW S54 engine like that; at WOT the alternator field is de-energized, releasing electrical loading. There's an extra wire in the loom to cut the field, we use this same wire in much the same way with one of the DTA's AUX channels in our set-up.
TBH, I don't recall if the batt. comp were set up to take into account the voltage drop we have when we are at WOT... Looks like I may have to look into this. :o


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 Post subject: Re: Adjustments when disabling alternator on WOT
PostPosted: Wed Jan 09, 2013 6:58 am 
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Joined: Sat Jul 21, 2012 3:25 am
Posts: 8
ECU Model: S80 Pro
stevieturbo wrote:
...power drop also affects fuel pump flow too, so that needs to be considered.


Good point but I have that in hand with the capacity of the pump and have a saftey margin on the PWM duty cycle to ensure it doesn't drop pressure below the regulated setting.

Keep the comments coming - most appreciated!
Stuart


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