MicroSquirt.com read only forum (Jan.15,2018)

what is the approx. current draw of Micro. S running 2 small, motorcyle ing. coils ans 2 inj's?

Thank's, Keith

Keith,

That depends almost entirely on the coils, injectors, and the fuel pump. MicroSquirt is a very minor draw (and few hundred milliamps, depending on the LED usage, etc.) compared to those.

Measuring the current draws is the best way to know. Calculating it is second best. If you want to guess, figure on ~3.5 Amps per coil (multiplied by the duty duty cycle, which depends on the number of coils and rpm) and ~ 1 Amp per high impedance injector (multiplied by the duty cycle, which in turn is affected by the rpm and flow rate).

For example, if two injectors are run at 50% DC, and you have two coils running 25% DC, then you would estimate:

I = (2*3.5*0.25) + (2 * 1 *0.5) = 2.75 Amps,

plus the fuel pump draw (which is hard to estimate, it should be measured or checked from the manufacturer's specifications).

Lance.

The MicroSquirt itself draws very little. On my application it pulls 95mA. I have 4 relays, each one of them pulls 150mA. Just to put the Microsquirt's draw in comparison.

The coils will draw good bit of power upto 7.5A while they are charging, a 3ms dwell on a 12krpm engine is roughly a 60% duty cycle. so figure a maximum average of 4A.

Injectors similarly but about 1A max, max average about 80% or 800mA

An Innovate LC-1 O2 sensor draws 2A.

Then there's the fuel pump 3A-7A and the cooling fan 4A-10A, but will draw a lot of power on startup, say 15-25A

My total maximum power consumption, I estimate at less than 16A. on a two cylinder

Hope that helps
Geoff

Guy's, that helps alot.

But also throws some things in to the mix.

I only have a12v, 20amp alt. on a 32 HP engine.

I am not sure what the D/C of the coils will be BUT, Max engine rpm is 3600.

Is it posssible to run a single/ dual output coil?

would that DECREASE the amp draw.


There is nothing I can do about the inj's

the F.P, I have is mind is about 5.5 amps @ 40 psi. I can run the inj's at a lower pressure to decrease the draw but that will raise the d/c.


My biggest conern is running all the F.I. equip while also running lights,

Keith

You should be okay to set it up on microsquirt, and then measure your current after its going.

If you're close then you can reduce your draw as needed.

Search the boards for small fuel pumps, there are some low current ones that would work well for your size. I seem to recall something about 2A-ish from a scooter.

Also you should consider what you tail/brake lights are running usually they're 15-25W a pop which is about 1-2A, LED lights bring that down to about 200-300mA. What size headlight are you running? 100W is about 8A.

Plan on saving 2A to charge the battery. Also if this was originally designed to power just lights and charge the battery after starting, then you may have some noise to the 12V, don't worry about it too much now, but tuck it away in the back of your mind.

Thank's,

I've been keeping my eye on the baby fuel pump thread. I looked at that Apriila pump but it's intank, I need inline. I took a look at the Walbro pumps. they have one that draws about 4.5amps @ about 40psi.

One option I am looking into is running big inj. @ a low fp to keep the amp draw down on the pump and the d/c down on the inj.

Would you have a guestimate on the what the d/c would be for the ign. coils @ 3600 rpm??

Currently I am running 4 lights.

3 55w halogen's
1 small light for the front running red/ grn light

I can remove 1 of the 55w lights and change it and the red/grn front light(it's a boat) to LED's

The other two are headlights and I don't think the LED's will work for those.

All that being said, I MIGHT be able to keep it all under the 20a mark, but just barely.

I am also looking into a higher amp regulator from another engine of the same size.

Wow 12A of lights.

Yeah definitely replace the red and green with LED, if for no other reason than never needing to replace them. You could also replace the three headlights with one HID, for example there is one on ebay now for $50.

LED and HID would bring your lighting load down to about 5-6A.

It looks like that will work.

Is there a difference between the it and the replacement bulb as far as amp draw?