Author Topic: 2 injectors with vems  (Read 9445 times)

Offline Regler

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2 injectors with vems
« on: March 16, 2009, 03:47:28 pm »
Hello,

follow question

I will drive 2 injectors per cylinder and conect parallel.

The injectors are high impedanz 12 ohm parallel is 6 Ohm

the current is at 1 injector 1A (12V/12Ohm=1A) at 2 injectors are the current 2A is this possible with the vems injector drivers or request a forward resistor?

Offline MWfire

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Re: 2 injectors with vems
« Reply #1 on: March 16, 2009, 04:25:03 pm »
Vems can driver more that 10A,  so you just connect two injectors parallel and connect to vems directly. Don't forget flyback.

Offline rob@vems.co.uk

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Re: 2 injectors with vems
« Reply #2 on: March 16, 2009, 05:37:42 pm »
When the engine is running the V should be considered to be ~14.4V.  14.4/6ohm = 2.4A
This is true, it is also worth considering your PW and duty, this will probably be reduced by using two injectors, so the 2A will not be constant if you have a duty cycle of 75% The current draw will still be 2.4A but the heating effect will be 2.4 * 0.75 = 1.8A or 14.4*1.8 = 25.92W each channel.
If I remember correctly you have a 5cylinder engine which means you'd have 129.6W which may result in a fair bit of heat to dissipate, so you might need to put some balast resistors in there, I've used 6R8 50W resistors with lowZ injectors and found that they don't get much over body temperature even after hard running for some time.

Offline MWfire

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Re: 2 injectors with vems
« Reply #3 on: March 16, 2009, 09:26:51 pm »
Heat on mosfet(vems)=I^2*0.055 . Meaning 2.4A is 0.3W on mosfet.

Offline rob@vems.co.uk

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Re: 2 injectors with vems
« Reply #4 on: March 17, 2009, 02:38:36 am »
I dare you to touch the FETs when the engine is running flat out ;)

Rob

Offline MWfire

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Re: 2 injectors with vems
« Reply #5 on: March 17, 2009, 03:06:13 am »
I dare you to touch the FETs when the engine is running flat out ;)

Rob
Without problem, becouse they are cold. Most of the heat is dissipated in injectors. And most hi-ohm injectors don't work with resistor(greater than 6ohm).