fuel only install... what do I need to wire up?

[ochizon]

As is frequently recommended on this board, I am going to install the megasquirt (MS-I, V3, msns-E) as a fuel only setup to start, before moving on to full control down the line.

Anyway, I was wondering what I should switch over to the ms's control? I know I need switch the injectors over from the stock ECU, but I figure I will take a signal from the TPS, but leave it wired into the stock ecu as well. I figure I will do the same with the tach signal and the coolant signal.

I was thinking also of leaving the fuel pump under the complete control of the stock ECU, as well as the IAC funtion.


Do I need to even istall the IAT at this point? Will the msns-e refer to it for fueling adjustment?

[78Spit1500Fed]

...I was wondering what I should switch over to the ms's control? I know I need switch the injectors over from the stock ECU, but I figure I will take a signal from the TPS, but leave it wired into the stock ecu as well. I figure I will do the same with the tach signal and the coolant signal.

If you're controlling the injectors with MS, you'll have to switch them over. You can usualy split the TPS signal without too much headache. The tach signal is a question... what kind of signal is it? 1 pulse per spark? Something else? The coolant signal can not simply be split like the TPS, read the Sharing Sensors section of the MegaManual.

http://www.megasquirt.info/v22manual/sharesen.htm

I was thinking also of leaving the fuel pump under the complete control of the stock ECU, as well as the IAC funtion.

That's probably fine. The safeguards built into the MegaSquirt are probably built into your stock ECU. (Fuel Pump shut-off if no RPM's are seen)

Do I need to even istall the IAT at this point? Will the msns-e refer to it for fueling adjustment?

The MS uses the ideal gas law to determine fueling requirements, and it absolutely MUST know the incoming air temperature to make an accurate calculation. If your vehicle is presently Fuel Injected, it surely has one somewhere. (Some IAT's are integrated into an MAF)

-Brian

[ochizon]

Thanks,

Yeah, my truck does have an IAT (of course), but I am still so unfamiliar with the different versions of the MS, I wasnt sure if all of them have the ability to make fuel adjustments on their own... and the IAT, being a info source for the processor to determine fuel correction, would be useless if the processor could not do that...

I will wire it up, its very easy, I was just checking.

Also, what bearing does the CLT on the fueling with the MS, if I am keeping the idle control with the stock ECU?

[78Spit1500Fed]

Also, what bearing does the CLT on the fueling with the MS, if I am keeping the idle control with the stock ECU?

The CLT is used in warm-up fuel enrichment calculations.

If you live in an area where it's a constant temperature, you might be able to leave it out and use the idle control alone... if your temperature varies much at all, however, you'll have some hard starts on cold mornings!

-Brian

[ochizon]

Miami, FL... coldest start up temp is about 65 degrees at worst, hahaha

[oughtsix]

Can you control the idle with the stock CPU and the rest of the fuel with the MS? It would seem to me that fast idle would be a function of letting in extra air and adding extra fuel. How could you use the stock cpu to add extra air and MS to add extra fuel?

I am just a beginner trying to understand also.

[GeorgeGt]

on my first install , stock ecu did the fuel pump and rpm/ignition , megasquirt did all the rest. so only crank sensor and fuel pump was connected to Motronic , everything else was connected to MS , worked fine for me.