IACV with Megasquirt... how's this work?

[krazydriver]

I know some people run megasquirt, and i'm planning on getting it myself sometime or other.

I was just wondering if there was a workaround for the IACV yet. I know some people have had to piggyback the stock ecu just to get the engine to idle.

I'm still searching around but if anyone has megasquirt and has some pointers I'd really appreciate the info.

The more i know about MS the better i'll feel when i do install it.

[The_Chosen_One]

ummm all the IACV needs is a switched 12 volt and a ground. Its how mines setup and I get a solid idle. I dont see why people would use the stock ecu.

or convert to a stepper motor.

[ZiG]

I'm also facing this problem.. I am trying to figure out exactly how to wire it to the MS.. I only ordered the kit last week, so maybe when it gets here I will be able to figure it out. If I do, I'll post in here.

[The_Chosen_One]

If you want MS to control even all it will do is just turn it on, since the IACV is a solenoid with 2 wires it just needs power and ground. On MS the FIDLE wire is actually a ground, so take the power from MS or injectors and splice into 1 wire on the IACV plug, than the other wire goes directly to the FIDLE wire on MS.

than in Megatune for idle valve settings pick Solenoid.

[ZiG]

Why would you have MS control the Fidle valve at all? I thought the only thing you used that for was AC? And in that case it would automatically turn on as soon as you push the ac button?

For the iacv, are you saying there already are those 2 wires coming out of it, and all you have to do is connect them to the iacv solenoid? Sweet!

[ZiG]

Ok, I just read over some stuff on MS.info and I think I get it now. Since the fast idle solenoid is either on or off, you can just use it con control idle.

Now, is the standard iacv solenoid a pwm style? If you disconnected the power, would it go to open or closed?

edit: oh crap, it looks like only the msII will control a pwm valve. I have the MSI.
Modified by ZiG at 10:12 AM 7/29/2007

[The_Chosen_One]

Alright for KA/CA/SR when I looked at them they utilize the same style idle valve. IACV = Idle Air Control Valve its a blob of a thing it also houses the thing for the A/C so when you turn on the a/c it activates and allows more air to pass through.

theirs some specutlation on what type of valve the Nissan is, I asked the peeps at MS and they stated it acts exactly like a on/off fast idle valve. Some peeps on here say its a stepper motor. I highly doubt it because usually stepper motors work by polarity and have more than 2 wires, also stepper motors work in steps. Our valve just goes on and off, the stock ecu may however do the on/off repeatedly fast which can mimick a stepper motor.

Anyways heres a pic what I'm refering to.

[ZiG]

Yup, I agree with all that. I was sort of afraid though, that the solenoid had multiple positions, like a spring pulling it closed and the ecu would vary the current. Is that what a PWM iacv is? I still havent been able to figure out if that's what PWM is.

Anyway, if it's just an on/off that cycles real fast, great. That makes things easier.

(And yeah, I can verify that it is NOT a stepper motor. I've taken mine apart to clean before, so I know what it looks like real well )

[The_Chosen_One]

PWM stands for Pulse Width Modulation, pretty much certain supply of current will make the device funtion differently so what you said would be a good idea. Also PWM is what injectors are depending the length of current supplied effects how much it sprays and stays open.

http://en.wikipedia.org/wiki/P...ation

http://www.megamanual.com/v22manual/minj.htm#pwm

Quote »Pulse Width Modulation

Injectors are either high impedance or low impedance. High impedance injectors (usually about 12-16 ohms) can take a 12 supply directly, without a form of current control. Low impedance injectors (generally below 3 ohms) require some form of current limiting. With MegaSquirt, you can use resistors to limit current, or you can use Pulse Width Modulation (PWM), which is a software solution built in to MegaSquirt.

PWM works by switching the 12 volt ground to the injector on and off very rapidly (in about 0.000059 seconds!). The ratio of the "on" time to the "off" time determines the current through the injectors. However, the easiest way to think of the PWM% is as a percentage of the supply voltage, so 50% PWM on a 14 volt supply becomes effectively 7 volts on average, 28% would be 4 volts, etc.

Remember that pulse width and PWM% are two different things. Pulse width is the total duration of the signal whereas PWM% is the ratio of 'on-time' to 'off-time' within the pulse. So in the above illustration, the pulse width for both is the same, but the PWM% for the first is 50%, while for the second it is 25%.

The PWM% you will be able to use depends on the flyback circuit you have. Version 2.2 hardware generally requires about 55% to 75% PWM. Often the engine will run with lower values, but will not have enough voltage to re-start. Note that using embedded code version 2.986 or higher will disable PWM during cranking, allowing somewhat lower PWM% values. The FlyBack Board allows you to lower the PWM% dramatically, generally to 30% or less. It also helps close the injectors faster.

With better flyback control, you can reduce injector opening times (recall that the injector opening time is really the sum of the opening and closing times), and increase the duration of the 'controllable' part of the pulse width (i.e. after the opening time),

The important thing about the injector open time is that it sets a lower bound for the pulse width (regardless of whether PWM is on, etc.). so if you have injector opening at 1.7ms, you cannot set it to 1.6 or anything lower, even with VE=0. MegaSquirt assumes no fuel is injected during this time, but some is, though it is hard to calculate how much. The longer it takes to open, the more fuel is likely injected during opening. With lower opening times (by allowing full voltage (i.e. no PWM), you can get the injectors open quicker.

Your engine will need a certain amount of fuel to run correctly at idle when fully warmed up. If this amount is below that injected during the injector opening time, you will always be rich and have no way to lean it out, short of reducing the fuel pressure.

Note that PWM is disabled (in v2.986 code) during cranking so the injectors get full battery voltage. This makes 'severe' starting conditions (lower cranking voltages, etc.) less likely to result in the injectors not opening. This is not possible with resistors, unless you devise a way to bypass them during starting (like the older cars did for the ignition coil).

When using low-impedance injectors, which are also called peak and hold injectors (P&H), you wire them in parallel. The wiring is the same for P&H or saturated [high-impedance].

To exceed the recommended number of injectors (see below) either requires resistors in series with each injector or a modified flyback setup.

The following is a guide as to whether you need to use resistors or the flyback board:

[/quote]

[krazydriver]

If you want MS to control even all it will do is just turn it on, since the IACV is a solenoid with 2 wires it just needs power and ground. On MS the FIDLE wire is actually a ground, so take the power from MS or injectors and splice into 1 wire on the IACV plug, than the other wire goes directly to the FIDLE wire on MS.

than in Megatune for idle valve settings pick Solenoid.

thanks for clearing that up. I'm planning on installing megasquirt within the next 2 or 3 months. I know awhile back someone wanted to start a megasquirt thread so everyone could share setup info but i don't think it ever got started.

When i do get started with it i'm going to fully document the whole process. That way people won't have to be afraid of attempting MS, because we'll have a walkthrough for it.

[ZiG]

When i do get started with it i'm going to fully document the whole process. That way people won't have to be afraid of attempting MS, because we'll have a walkthrough for it.

You have my support.. And I'll make sure to document everything when I do it in a couple weeks (hopefully it will be here soon! )

[The_Chosen_One]

thanks for clearing that up. I'm planning on installing megasquirt within the next 2 or 3 months. I know awhile back someone wanted to start a megasquirt thread so everyone could share setup info but i don't think it ever got started.

When i do get started with it i'm going to fully document the whole process. That way people won't have to be afraid of attempting MS, because we'll have a walkthrough for it.

are you gonna be using EDIS or KA ignition.

I made a write up over a yr ago converting to EDIS here it ishttp://forums.nicoclub.com/zerothread/164446

a lot of info their.

[krazydriver]

i'm going to be doing the direct coil drive as outlined here.http://www.nicoclub.com/articles.php?id=242073

i didn't really want to go through all the work involved in setting up EDIS.

honestly it's gonna be awhile before i order the kit, and i'm sure i'll proceed in my usual OCD way of going extremely slow and testing constantly. Which means it will take me forever to build it but at least i can be sure that it will work in the end

[ZiG]

Well I have an update for ya Krazy. First of all, you need to upgrade a transistor in your board if you're gonna run a PWM IACV. Since I didnt know this, I had to set it up to use my fidle solenoid for the A/C. Once I get the new transistor I will switch to the PWM valve.

Oh, and right now I am having a no spark issue. I think it's the coil. It kind of looks as though I will have to replace it with a stock mopar style one, so be aware of that.

[krazydriver]

hmm. i got an MSD now.. hopefully i can figure out some way to get that to work with the MS.

Zig if you get things going would you be able to post up your msq file somewhere just for me to take a look at for reference.

[ZiG]

Oh sure, sure. I'll post the msq and more info on how to get it all installed.

Just.. yeah, be aware that there is a lot more work involved than what is mentioned in the writeup. I actually bought my MS kit from the guy that made the writeup and I'm in contact with him right now about it. Still don't have any spark..

[ZiG]

So that car is running, with none other than the AC valve. Looks like it will do just fine. Though it does lope a bit while coming to a stop. I can only imagine that it is a combination of a rough tune and perhaps the valve isn't able to flow quite enough air.

In any case, I'll be posting in detail, what exactly you need to do to install the MS as a full standalone, as well as I will be posting my tune.

[ZiG]

zer...d=170

Here ya go.