Page 60 of 79
Posted: Thu Oct 24, 2013 7:06 am
by ChrisJC
stevieturbo wrote:I'd have thought more power than that actually.
80Amps at 14Volts = 1120Watts
There are 746Watts per horsepower
So 80Amps at 14Volts = 1.501hp
Not enough to be worth worrying about!
Chris.
Posted: Thu Oct 24, 2013 7:17 am
by katanaman
You might well be right as those figures don't take into account any loses. It's really just a straight conversion from amps to watts then to HP (745.7 watts =1hp) . It won't be much more than that though.
Using a really modern alternator would be difficult as they are all ECU controlled now for fuel efficiency. Things like they charge less on acceleration and more on coasting/overrun. Even the 4.0 4.6 rovers had large alternators though, all the serp belt ones basically. They were 110A if I remember right. Not sure if you could drive a large alternator effectively without a serp belt right enough.
Posted: Thu Oct 24, 2013 7:47 am
by DaveEFI
I have a self contained 100 amp unit on my SD1 EFI driven off the v belt. It's a Marelli A127 type with integral fan. More or less a direct replacement with an extra spacer to one of the original brackets. I do have a turnbuckle for adjustment as the original was a right fiddle to set.
Posted: Fri Oct 25, 2013 5:35 am
by unstable load
When the alternator on my P6 packed up I had it rewound to deliver higher amperage. I can't remember how many it delivers, but it was significantly more than standard.
Any decent rewinding place would be able to wind it to deliver higher amps.
Posted: Fri Oct 25, 2013 12:48 pm
by Ian Anderson
katanaman wrote:You might well be right as those figures don't take into account any loses. It's really just a straight conversion from amps to watts then to HP (745.7 watts =1hp) . It won't be much more than that though.
Using a really modern alternator would be difficult as they are all ECU controlled now for fuel efficiency. Things like they charge less on acceleration and more on coasting/overrun. Even the 4.0 4.6 rovers had large alternators though, all the serp belt ones basically. They were 110A if I remember right. Not sure if you could drive a large alternator effectively without a serp belt right enough.
Hi Marki
In the old days they used to recon they could power 5hp through a standard V Belt
Things like Lawnmowers with a Brigs & Strattern 4.5 hp motor through a V belt working hard on thick grass held up for ages
Ian
Posted: Fri Oct 25, 2013 2:11 pm
by stevieturbo
Ian Anderson wrote:katanaman wrote:You might well be right as those figures don't take into account any loses. It's really just a straight conversion from amps to watts then to HP (745.7 watts =1hp) . It won't be much more than that though.
Using a really modern alternator would be difficult as they are all ECU controlled now for fuel efficiency. Things like they charge less on acceleration and more on coasting/overrun. Even the 4.0 4.6 rovers had large alternators though, all the serp belt ones basically. They were 110A if I remember right. Not sure if you could drive a large alternator effectively without a serp belt right enough.
Hi Marki
In the old days they used to recon they could power 5hp through a standard V Belt
Things like Lawnmowers with a Brigs & Strattern 4.5 hp motor through a V belt working hard on thick grass held up for ages
Ian
Perhaps, but a lawnmower wont see the same rpm's and change of rpm's than a car belt will.
Posted: Fri Oct 25, 2013 3:06 pm
by Coops
this has wandered a bit
Posted: Fri Oct 25, 2013 3:41 pm
by Rossco
Tony......lets admit it though, most lawnmowers have done more miles than the Cappa in the last 2 years
Posted: Fri Oct 25, 2013 6:41 pm
by r2d2hp
think my chainsaw has vibrated further
Posted: Fri Oct 25, 2013 8:26 pm
by mgbv8
Rossco wrote:Tony......lets admit it though, most lawnmowers have done more miles than the Cappa in the last 2 years
Ouch!!!
Posted: Fri Oct 25, 2013 8:27 pm
by mgbv8
r2d2hp wrote:think my chainsaw has vibrated further
Double OUCH !!!
Come on guys! Coops need some support here
Posted: Fri Oct 25, 2013 11:15 pm
by katanaman
sorry
Posted: Sat Oct 26, 2013 6:06 am
by Ian Anderson
Posted: Sat Oct 26, 2013 9:35 am
by Darkspeed
Sorry for still wandering
That assumes no heat produced, no running of the cooling fan required. and no mechanical losses in the system. no belt frictional / heat losses etc.
Expect the system to no more than 40% EFF. maximum and efficiency dropping with RPM.
Just think of the effort required just to spin the alternator and its fan at 10,000 rpm without it actually being connected to anything.
I would say more like 4-5HP at 6000RPM and all losses are worth worrying about. Its a 1% loss even with a 500BHP motor
ChrisJC wrote:stevieturbo wrote:I'd have thought more power than that actually.
80Amps at 14Volts = 1120Watts
There are 746Watts per horsepower
So 80Amps at 14Volts = 1.501hp
Not enough to be worth worrying about!
Chris.
Posted: Sat Oct 26, 2013 9:57 am
by katanaman
I agree there will be losses but 4-5 HP? That would mean your your using 2.5-3.5 to get 1.5 worth of power. I really doubt that, even a screw supercharger isn't that inefficient and they are fairly poor.
Anyway we better get back on topic before Tony breaks out the big sticks