How Much??

ian.stewart · Post by **ian.stewart** » Wed Sep 05, 2007 8:38 pm

How much current does it take to run the average Batch fire FI system, Pump, ECU, and Injectors, Im looking at downsizing my alternator, but I dont want to get into the situation of the fuelinjection or ignition having problems when the Fans come on

Post by **katanaman** » Wed Sep 05, 2007 8:43 pm

Are you running ignition as well Ian?

Post by **katanaman** » Wed Sep 05, 2007 8:49 pm

while your answering post the impedance of your injectors if you don't know exactly then if they are high or low impedance.

ian.stewart · Post by **ian.stewart** » Wed Sep 05, 2007 9:10 pm

low impedence, and just running a single coil at the moment. but have intentions of running coil packs next year.

Eliot · Post by **Eliot** » Wed Sep 05, 2007 9:57 pm

on megasquirt - they use 5a fuses on each of the two chanels - so you can assume its quite a bit less than that. ECU is in the order of millamps, assume 1a max.
Biggest draw is most likely to be the injection pump - probably around 10amps unless its a big one.

Post by **katanaman** » Thu Sep 06, 2007 1:25 pm

each injector is about 0.8A, max an amp for the ecu and the fuel pump could be up to 20A depending on what it is. Worst case scenario is a total draw of about 25 amps.

Just out of curiosity what's the thinking behind a smaller alternator?

ian.stewart · Post by **ian.stewart** » Thu Sep 06, 2007 2:18 pm

katanaman wrote:

Just out of curiosity what's the thinking behind a smaller alternator?

The Idea behind the smaller alternator packaging, Hopefully the one I have in mind is a 50amp thingy, and its TINY, and the other advantage is its so much lighter than the great big thing I have just removed, 3.2kg verses a whopping 11kg, all the bracketry is now made and is no heavier than the original set up, I still have the option of fitting a 17ACR, which I think is about 2kg heavier than the one I am fitting.
Save weight,= Improved power to weight Ratio,= go quicker for no more HP

Post by **katanaman** » Thu Sep 06, 2007 4:01 pm

I get the weight thing I just didn't know your original alternator would be so heavy.

chodjinn · Post by **chodjinn** » Thu Sep 06, 2007 5:29 pm

Hmmm, this is one thing I was thinking of recently. I have a standard MGB V8 alternator (dont know the rating) but only going to be running similar to Ian (plus fan, elec water pump and lights etc). Didn't realise it was so low (Amps). Might get away without upgrading the alternator!

r2d2hp · Post by **r2d2hp** » Thu Sep 06, 2007 5:50 pm

Just dont go out after dark and in the rain Ian

ian.stewart · Post by **ian.stewart** » Thu Sep 06, 2007 5:58 pm

Reg, thats what I am worried about.

I suppose I could put it together --run it about, then when its all loaded up, put a clamp on the alt feed wire and see what its pulling.

r2d2hp · Post by **r2d2hp** » Thu Sep 06, 2007 7:46 pm

Do you have a clamp Ian. If your stuck I do have one but will need to get it new batteries.

ian.stewart · Post by **ian.stewart** » Thu Sep 06, 2007 8:25 pm

Plenty of time, probably wont be running until next spring now,

v8alex · Post by **v8alex** » Thu Sep 06, 2007 8:32 pm

I've recently changed from a standard Rover alternator to a Denso 35A alternator. It's much smaller and lighter than the Rover item - i.e. reduced diameter and is internally cooled, so no fan making it more compact lengthwise. Not too expensive either. Ideal also for se7en style kit cars like my DAX Rush where under bonnet space can be tight.

I took a piccy of the two side by side, but for the life of me can't work out how to put photos on the forum.

Alex

Post by **katanaman** » Thu Sep 06, 2007 9:13 pm

v8alex wrote: I took a piccy of the two side by side, but for the life of me can't work out how to put photos on the forum.

Alex

http://www.v-8.org.uk/forum/faq.php#24 click the img button paste link to pic and then click close tags