I just realized I don't know what a fast idle valve actually does...

[740ATL]

So I was all types of fretting about fast idle valves and PWM idle valves and trying to decide which to use for MS when I realized that I don't know wth a fast idle valve does.

When I turn the key on my LH2.2 740 in the morning, or any time of day, it starts and idles at around 700rpm.... doesn't go any higher or lower.

I think back to the other cars I've owned, 84 244, 88 4-runner, 79 camaro, vw rabbit, dodge ram, and the ONLY 2 cars that did anything different than what I described previously were the carburated camaro and dodge truck... When started, they idled at about 1200-1500rpm, then after the bi-metallic coil warmed up, the idle came back down.

I did some searching on msefi and the MS HP, but I can't locate anything that really drives it home for me.

So what does a 2-wire F-idle valve do for me?

What is a 3-wire PWM idle valve going to do for me?

and how the H are people running MS'd vehicles without either of these?

does the F-idle valve mimic the bimetallic coil of old? Does the PWM valve mimic the unit that's in my lh2.2 volvo?

this inquiring mind would like to know.

muchas gracias.

Mike

[Lord_Athlon]

The fast idle valves let air into the engine to keep the car at a user specified idle. The pwm valve does the same thing. I dont have either, and i cracked the throttle plate a little and my idle is always at 800 rpms. I finished tuning warmup so no matter how hot or cold it is, the car will idle at 800

[swedefiend]

Does the PWM valve mimic the unit that's in my lh2.2 volvo?

The 2.2 valve is a Pulse Width Modulated valve.

Two wire PWM valves go from open to close based on XX% to 100% DC (think square wave). some of them can be wired like the old school bi-metal type. You have to be careful though because at 100% DC some valves will overheat.

AFAIK the Volvo ones tolerate 100% DC just fine. Also, the most common two wire LH valve is closed at 30% DC and opens from there. If you have less than 30% DC, the valve is open again (as a fail safe to allow the car to "limp" when the valve or wiring fails)

Three wire valves are a little more sophisticated in that they do not have a "open" and "closed" position. The are the "butterfly" type valve that flutters all over the place at variable speeds in order to correct idle (think alternating current - but with DC voltage). They are generally more tolerant to sudden changes in idle requirements because of a thing known as hysteresis.

But, that is a lesson in calculus and physics that I will defer to more knowledgable persons.

[fryea]

im not running one right now, my idle is around 8-9, but when i first start up and i just barely crack and throttle, or if i really hammer around the power steering without any gas, then it will have a tendency to sputter or die (usually 60 degrees out)

what i plan on getting sometime is a valve from an older k-jet based car. It only needs 12v and ground, and opens/closes based on how hot the surrounding engine is, and then you dont have to sacrifice pin 30 for spark output (or you can be fancy and use led17 for spark)

[towerymt]

and how the H are people running MS'd vehicles without either of these?
With LH2.2 and the IACV unplugged, it would idle low, about 500-700 depending on temp. Using the thumb screw I got a nice idle that was steady, probably up around 900. Now with MS and no idle valve of any kind and no thumb screw (still using LH3.1 TB, about to switch back to the 2.2 TB w/screw though), I get a shakey and low cold idle, then quickly it becomes an 1100-1200 idle when warm. Sometimes it hangs around 1300-1350. I had the ign. advance set at 17 in the 4 lower corners of my spark table, so I dropped those today and was able to get a stumbly & lower idle, so I just need to play with timing I think. With an idle stuck between my 1000 and 1500 bins, it's probably close to 20° and I couldn't seem to lean it out.

I think you can fine tune a good idle w/o a valve, but the valve may make for an easier cold idle with less tuning difficulty. YMMV

[740ATL]

Hey guys, thanks for the replies.

I understand the concept of bypassing the TB to let additional air in...

swedefiend, thanks for the clarification with the pwm type.

Is that it tho? a pwm valve is simply a bit more elegant than a f-idle valve? They both do the same thing? I just figured because of the name fast-idle valve, that maybe it would force the engine on startup to remain at a higher idle, then once it warms up, drop the idle back down to a 700-900rpm level.

And I know of at least 2 people now currently running without any idle valve. It just seems like there's something more that I'm missing. Perhaps my real question is, do engines simply want to idle at a specific rpm? I'm hopefully not sounding too dense here, but does there exist a specific set of operating conditions where any engine will idle at a set rpm?

many thanks.

Mike

[740ATL]

With LH2.2 and the IACV unplugged, it would idle low, about 500-700 depending on temp. Using the thumb screw I got a nice idle that was steady, probably up around 900. Now with MS and no idle valve of any kind and no thumb screw (still using LH3.1 TB, about to switch back to the 2.2 TB w/screw though), I get a shakey and low cold idle, then quickly it becomes an 1100-1200 idle when warm. Sometimes it hangs around 1300-1350. I had the ign. advance set at 17 in the 4 lower corners of my spark table, so I dropped those today and was able to get a stumbly & lower idle, so I just need to play with timing I think. With an idle stuck between my 1000 and 1500 bins, it's probably close to 20° and I couldn't seem to lean it out.

I think you can fine tune a good idle w/o a valve, but the valve may make for an easier cold idle with less tuning difficulty. YMMV

cool. Thanks Mike! Good to know.

I have basically one of each now... Ihave a regular no-thumbscrew TB, a thumbscrew TB, a volvo 2-wire valve, a volvo 3-wire valve, a ford 2-wire valve, and an old kjet bimetallic air valve. Not sure which to try first... probably just get it running, then try the tumbscrew TB, then pick a valve.

Mike

[The Aspirator]

I forget, are you running MS on anything yet or not?

I'm not running any idle valve on my car, nor is Erik. Adrian isn't either. We've all just got the thumbscrew TB. My car idles cold around 800, it sometimes dies right after the first start, but always idles on it's own by the second start. Warm idle gets up to about 1000. About a year ago I had my car idling really well, when hot I took it down to 400 for fun one day and it was beautiful.

Right now my car idles great, except for that first cold start. At 1000 rpm I'm pulling 30kpa, which is 21" of vac. Pretty strong!

[740ATL]

I forget, are you running MS on anything yet or not?

I'm not running any idle valve on my car, nor is Erik. Adrian isn't either. We've all just got the thumbscrew TB. My car idles cold around 800, it sometimes dies right after the first start, but always idles on it's own by the second start. Warm idle gets up to about 1000. About a year ago I had my car idling really well, when hot I took it down to 400 for fun one day and it was beautiful.

Right now my car idles great, except for that first cold start. At 1000 rpm I'm pulling 30kpa, which is 21" of vac. Pretty strong!


Thanks John, this is also very good to know. I can now cross this off the list of questions I have stored in my brain and move on to the next.... :)

I think the thumbscrew approach is the way for me to go first. I still want to take spark (when I do it) from LED17 so I can free up pin 30 for an idle valve in the future.

Right now, the car is sans everything. I had it wired up for MS, got it started, then apparently killed it sitting still. I'm told it's the cullen award... not sure how crazy I am about that. Things will start moving faster now that payday is here... engine hoist, a weekend of lifting, then hopefully in the next 2 weeks, I'll try turning the key again.

But you answered my question. Apparently, with the right combination or air, fuel, and timing, and engine will naturally want to idle at a certain rpm.... change those combinations, and the idle rpm changes.

many thanks.

Mike

[jpbturbo]

I'm also not running any sort of idle control.
I get around a 1300rpm idle when hot.
I really haven't messed with the idle for a few months though, I could probably get it to idle a little lower.
Right now the only problem I have with the high idle is that the synchros going into reverse don't seem to be too happy about letting me in at that rpm.

[ovlov760]

what i plan on getting sometime is a valve from an older k-jet based car. It only needs 12v and ground, and opens/closes based on how hot the surrounding engine is, and then you dont have to sacrifice pin 30 for spark output (or you can be fancy and use led17 for spark)
What do these valves look like and has anyone tried one with Msns?

I'm running without a idle valve. I put a plumbing ball valve in the line that I can adjust the idle with. :rofl:

[fryea]

http://megasquirt.sourceforge.net/extra/setup-msns.html

2nd picture down

[ovlov760]

Thanks. Guess I will have to head back to the jy soon.

[Matt Dupuis]

I just switched to MSII: haven't done much actual tuning yet - that's to come tonight - but I think there's a cold engine spark advance to further reduce the need for additional air at cold idle. In fact, there might even be one in MSnS-Extra, though I haven't been keeping up on that lately.

[ovlov760]

I just switched to MSII: haven't done much actual tuning yet - that's to come tonight - but I think there's a cold engine spark advance to further reduce the need for additional air at cold idle. In fact, there might even be one in MSnS-Extra, though I haven't been keeping up on that lately.
There is a IAT or CLT ignition advance and retard setting in extra.

[Matt Dupuis]

Oh right - it was IAT retard and CLT advance, wasn't it? I kept thinking it was just IAT retard.

So there ya go - advance the ignition during low CLTs, and it should idle a bit nicer when cold without the need for a fast idle valve. With lower heat in the chambers, you should be running more spark advance during warmup anyway.

[ovlov760]

Looking at MT right now I see the old IAT/CLT related ignition window. You can advance timing based on IAT or CLT. You can retard timing based on the IAT. There is a new thing I haven't even messed with yet called Idle advance settings. Looks like it can advance timing to a set TPS, RPM or CLT threshold.

[Matt Dupuis]

Looking at MT right now I see the old IAT/CLT related ignition window. You can advance timing based on IAT or CLT. You can retard timing based on the IAT. There is a new thing I haven't even messed with yet called Idle advance settings. Looks like it can advance timing to a set TPS, RPM or CLT threshold.

In the newest of the new MSnS-E, I think there's something called a forced idle, where it locks down the PW and spark advance below a certain RPM and TPS. At least, it was being talked about on MSEFI under high tech topics, but it might not actually be part of an official release yet.

[dl242gt]

Just to clarify the idle motor and fast idle valve. The fast idle valve gets 12V and ground and works like an air bypass for a higher cold idle. It warms up and closes. Looks like a flat disc with an electric connection and hose fittings on each side. This is as used on the 1976-1981 kjet B21F 240 series. The idle motor is a motor that opens and closes the air bypass channel to regulate the idle and is controlled by the engine fuel system computer or it's own stand alone ecu like the Volvo Constant Idle System. Like what's used with Volvos CIS or LH and newer fuel injection.

If you are going to keep the a/c you'll want some type of idle system to compensate for the increased load at idle from the a/c compressor. Running an idle control motor or valve lets the idle control circuit compensate immediately for the a/c coming on or a cold start.

MS has an idle motor control circuit now?

[miguels244]

The 2.2 valve is a Pulse Width Modulated valve.

Two wire PWM valves go from open to close based on XX% to 100% DC (think square wave). some of them can be wired like the old school bi-metal type. You have to be careful though because at 100% DC some valves will overheat.

AFAIK the Volvo ones tolerate 100% DC just fine. Also, the most common two wire LH valve is closed at 30% DC and opens from there. If you have less than 30% DC, the valve is open again (as a fail safe to allow the car to "limp" when the valve or wiring fails)

Three wire valves are a little more sophisticated in that they do not have a "open" and "closed" position. The are the "butterfly" type valve that flutters all over the place at variable speeds in order to correct idle (think alternating current - but with DC voltage). They are generally more tolerant to sudden changes in idle requirements because of a thing known as hysteresis.

But, that is a lesson in calculus and physics that I will defer to more knowledgable persons.


Bosch pn 0 280 140 500 application
83-84 b23 at least...
Is this a two wire pwm valve?
thnx
Miguel

[swedefiend]

Bosch pn 0 280 140 500 application
83-84 b23 at least...
Is this a two wire pwm valve?
thnx
Miguel

Google images says it's a three wire valve ;-)

http://catalog.masterautoparts.com/item.wws?mfr=BOSCH&sku=BSH006996&price=242.97&orpartno=912593&cookieID=1SJ0WVIW21SJ0WVIW1&image=http%3A%2F%2Fcatimages2%2Esophio%2Ecom%2Fweb app%2Fwcs%2Fstores%2Fservlet%2Fimc%2Fimages%2Ftn%2 F0280140500%2Ejpg&clientid=masterautoparts&clientid=masterautoparts

[tequila_gundam_no_chaser]

I too have been researching the fast idle valve vs pwm idle valve. From what I've read, the fast idle valve is a bi-metallic unit similar to what was found in k-jet 240s that simply used 12v. It had a bi-metallic strip inside that would heat and automatically close off, sealing off any extra air, bringing once the engine was warm and the strip was warm. The PWM idle valve is a little bit different, as it is a stepper motor attached to a butterfly that clutters, allowing in bits of air to keep the idle constant. MS does allow for control of the valve using Fidle and a modification of P7 transistor if your running a 2.2 board (3.0 is different). It is a stepper motor, so you've got to have stepped voltage going to it, from the MS, but I was also thinking of possibly using an rpm sensor (tach maybe?) to do the same? Anyone thought of that?

Anyway, you've got PWM idle within MS and you mainly use it for cold starts and running aircon. It is also nice because your idle will not drop below a certain point. Run an a/c compressor without it, and the noticeable lag will stall your motor, or at least it has in my experience. You can control your idle, using the idle adjustment screw on the manifold as everyone else said and you can also play with the timing. My car idles around 18deg timing and it keeps things at a very nice controllable 900rpms. On the lower end of the map (500rpms, 10kpa), I have the timing jump to 21deg timing, so that every now and again when the idle "hiccups", it will hit that patch of increased timing and bump itself back up to standard rpm range. creative tuning ftw.

[ovlov760]

I got a lh2.4 2 wire iac from the junkyard. Are there any instructions online about how to wire it up to megasquirt? I also pulled a IAC off a 850 turbo but it turns out it's just a physically larger verison of the lh2.2 iac. It's on the same number on it and 3 wires.

[benflynn]

i use no valve, i would use a 2 wire valve wired to a switch, i think the best option is to use a stand alone kjet idle system

[ovlov760]

i use no valve, i would use a 2 wire valve wired to a switch, i think the best option is to use a stand alone kjet idle system
I'm still hunting for one of those. I'll probably visit another junkyard tomorrow if the weather permits it.

[JohnLane]

Electromotive uses the GM stepper motor. I have found these things to be troublesome in my car as well as in dealing with any manner of customer's car that is stuck with one. They have (if memory serves) four wires.

I have seen that the Bosch 'auxillary air valve' which uses two wires and 12 volts to it to warm the bi-metallic spring do not live well in boosted applications.

In my car I have given up on the fast idle valve and use the thumbwheel idle air bypass as we find on the B-280 throttle body. It just idles a little low when cold. No biggie.

Before 'idle speed motors' we used solenoids to open up a passage and allow mo air to bypass the throttle plate for A/C. The Japanese used them for a long time. They were reliable and in some cases adjustable. Could be easily adapted for our uses for very little dough.

[Hank Scorpio]

I forget, are you running MS on anything yet or not?

I'm not running any idle valve on my car, nor is Erik. Adrian isn't either. We've all just got the thumbscrew TB. My car idles cold around 800, it sometimes dies right after the first start, but always idles on it's own by the second start. Warm idle gets up to about 1000. About a year ago I had my car idling really well, when hot I took it down to 400 for fun one day and it was beautiful.

Right now my car idles great, except for that first cold start. At 1000 rpm I'm pulling 30kpa, which is 21" of vac. Pretty strong!

+1. My cold starts were only a bit tricky at first. Ussualy just a little throttle on cranking and hold the idle up around 1500 rpm for a couple seconds and it was fine.

[740ATL]

Hey guys, thanks for all the replies... I've been experimenting a bit on my 740 LH2.2 (it's the only car actually running), I unplugged and corked the factory 3-wire IAC and have just been using the thumbscrew for the past 2 weeks... cold startup is about 6-700rpm and a little rough, but after 20-30 seconds, it smooths out a bit. Once warm, it purrs like a kitten at 800rpm.

I can see where having an idle valve will add a bit of refinement to the whole process.

Mike

[The Aspirator]

Yeah so it's the exact same with LH, though LH is dependant on the idle valve to smooth things out. Good to know.

[ovlov760]

junkyard trip was successful. I got these two bosch valves.
http://www.cramptonstation.com/idlevalve.jpg
http://www.cramptonstation.com/idlevalve2.jpg
http://www.cramptonstation.com/idlevalve3.jpg
http://www.cramptonstation.com/idlevalve4.jpg
One is larger than the other and the connector is in a different place. Both appear to use the same standard 2 wire connector though. Probably get around to trying them out this weekend if it stops raining.