IAC for engine?

[ReadySetGo]

Are you using an IAC to keep the motor running?

We made it so we dont need an IAC to keep the car idle, but when we floor it then release off the throttle it wants to die and not go back to idle. So I'm thinking of putting a IAC motor on.

Should I do it?

-Omar Barker
CSU, Sacramento
Hornet Racing Development
http://gaia.ecs.csus.edu/~formula/

[ReadySetGo]

Are you using an IAC to keep the motor running?

We made it so we dont need an IAC to keep the car idle, but when we floor it then release off the throttle it wants to die and not go back to idle. So I'm thinking of putting a IAC motor on.

Should I do it?

-Omar Barker
CSU, Sacramento
Hornet Racing Development
http://gaia.ecs.csus.edu/~formula/

[Dan Deussen @ Weber Motor]

Since you don't have to worry about emissions and air conditioner compressors kicking in, I wouldn't bother putting the IAC on.

Here are a few things to try:

1) Try adding injection pulsewidth below your idle rpm. You might be going to lean when the engine decellerates.

2) Try playing with the spark advance. See what a few more degrees will do.

3) Again, since emissions are not an issue, just try bumping up the idle screw on your throttle body. A 3000 rpm idle won't hurt anything and should be a lot more stable.

What engine, injectors, throttle body, ECU are you running?

Daniel Deussen
www.walbro-italy.com (http://www.walbro-italy.com)

[Ryan Schoffer]

yeah, those are good suggestions - we run a highish (~1250 RPM) idle, and i have it advanced a good amount, and mapped real rich under the idle RPM, that way it wont stall out even from WOT

having a high idle also helps keep the battery charged, and makes the engine more responsive

Vehicle electronics leader

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[ReadySetGo]

Cool cool, great ideas. Zx6r, accel dfi, stock cdi. So we cant really mess with ignition, but I will definetely bump up the under idle injector pulses. We currently have an idle of about 4000.

Also, are you guys running on alpha-N or MAP speed density?

We currently have alpha-N but it looks like we can hold a pretty steady manifold pressure. We are going to try and do another fuel map based on manifold pressure and see if its any better.

-Omar Barker
CSU, Sacramento
Hornet Racing Development
http://gaia.ecs.csus.edu/~formula/

[murpia]

For those that can alter timing, try picking an idle RPM, say 1500rpm, then adjusting your idle screw to achieve say 1650rpm at normal spark timing.

Now back the spark off in the 1450rpm->1700rpm range until your idle drops back to 1500rpm. Now, in the event of any stumbles below 1450rpm your spark map will ramp in extra advance and therefore torque to help stabilise.

Keep the mixture stoich, or a little bit rich, and you should be fine. An IAC is overkill, unless of course you also use it for your downchange throttle blips...

Ian

[Ehsan]

[QUOTE]Originally posted by Dan Deussen @
3) Again, since emissions are not an issue, just try bumping up the idle screw on your throttle body. A 3000 rpm idle won't hurt anything and should be a lot more stable.

Actually, a 3000 RPM redline does cause trouble. It will grind the heck out of your gears when you try to shift from neutral into first. The motor is spinning too fast for the gears to engage correctly. My team kept ragging on me for building a bad shifter cause "it wouldn't shift out of neutral" but eventually, while riding my own motorcycle, I discovered that the sequential transmission on a motorcycle does not like going into gear at anything above 2000 rpm. So try your best to keep your idle below that unless you enjoy the sound of gnashing gears.

[Matthew]

i thought about an IAC because of the pain of watching the idle during warm up. a normal idle when first started up in march in minnesota turns on you once the oil has gotten up to temp. but we desided againsed it because our time could be spent better elsewhere.

as far as prblms go when relaseing the throttle our M4 has an en-lean funtion that tempor. holds fuel back when the throttle closes suddenly, like the opposite of the en-rich function which gives a burst of fuel as it opens. Our car had throttle response issues untill we sorted out thoose values, now it runs like a dream.

-Matthew Hetler
hetl0020@umn.edu

[B Lewis @ PE Engine Management]

If you don't want the trouble of an IAC but you still want "fast idle" ability when it is cold, try using a simple solenoid. With our engine controller (and most others I believe) you can control a solenoid as a function of temperature. I personaly wouldn't want the added expense and weight but for about $30 you can easily configure one.

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems for $798"

[Jon Prevost]

I see no need for such a device in our application. Maybe if we drove this on the street and spent a fair amount of time at idle.
Also the usage of an IAC would require that you have room imbetween your throttle and restrictor. With that being said, and most designs have rather large divergers meaning the further away from the restrictor the larger your throttling device. Large is bad because it's too heavy. Then for the flow to be really slick right before the restrictor you wouldn't want to have an IAC passage port! Keep in mind there is to be no throttling device downstream of the restrictor so this brings us back to the size issue.
K.I.S.S. don't go with an IAC. Oh, and FWIW, IAC's on street cars are also a pain. They're only there for bad drivers with stick, stupid drivers that think little tip in on throttle and there car is fast, and people that hug trees (it's an emissions thing).
I've limited my iac throttle follower steps in my personal vehicle to 20 steps. Those 20 steps are just enough to keep the car from stalling if my tune is way off. It's more fun blipping the throttle and having the idle drop down http://fsae.com/groupee_common/emoticons/icon_wink.gif .

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[B Lewis @ PE Engine Management]

Amen, John http://fsae.com/groupee_common/emoticons/icon_biggrin.gif!!!

Brian Lewis
Performance Electronics, Ltd.
www.pe-ltd.com (http://www.pe-ltd.com)
"Complete Engine Management Systems for $798"

[Frank]

listen to ian

put a "lump" in the map and force the thing to idle (handy when you have large throttles.. like formula SAE cars tend to have)

Frank

[Jon Prevost]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Frank:
listen to ian

put a "lump" in the map and force the thing to idle (handy when you have large throttles.. like formula SAE cars tend to have)

Frank<HR></BLOCKQUOTE>
I don't agree with this unless you can't figure out how to do it right. Even then I'd rather have a high idle than a spark plug fowling or piston top ring land chipping kind of idle.
Why do you have large throttles? I found that most FSAE cars have rather small throttles, at least they should.

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[Charlie]

In my opinion that is the way to 'do it right'. Production cars do the same thing. What is your opinion on the 'right' way to get a car to idle Jon?

-Charlie Ping

I just need enough to tide me over until I need more.

[Jon Prevost]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Charlie:
In my opinion that is the way to 'do it right'. Production cars do the same thing. What is your opinion on the 'right' way to get a car to idle Jon?

-Charlie Ping

I just need enough to tide me over until I need more.
<HR></BLOCKQUOTE>
Can you give me a few examples of the production cars that put lumps in there maps for idle. My experience is limited to aftermarket, OEM GM and Ford calibrations up until OBD-2. Not one of the GM calibrations has a lump in the idle areas of the tables. The reason for "lumps" in those areas of say the main ignition map is because most if not all calibrations have code specificly for idle conditions. Usually looking at vehicle speed below a threshold and then TPS% away from "idle" or the "zero" TPS learned. I could be more informative if you give me an applications and then if you knew if the system ran in open or closed loop idle. Oh, and probably most importantly, if the application were for stick or auto. You'll find a lot of funny looking maps in an auto calibration because of the torque converter. You usually load an engine with a stick at an above idle engine speed. Auto's get put into gear right from idle and there is anticipation if it's a good computer control, if not, "lumps" are used.

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[Ryan Schoffer]

my 4.7L 5 speed dakota has a lump in the map at idle - and has an IAC

i took the lump out with the piggyback computer because it was causing a bit of bogging, its mostly for people who suck at driving stick

Vehicle electronics leader

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[Jon Prevost]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Ryan Schoffer:
my 4.7L 5 speed dakota has a lump in the map at idle - and has an IAC

i took the lump out with the piggyback computer because it was causing a bit of bogging, its mostly for people who suck at driving stick

Vehicle electronics leader

http://www.ucalgary.ca/fsae<HR></BLOCKQUOTE>
How did you come to the conclusion it was a lump in the map? When exactly was it bogging? The whole scenario, like was it at low engine speeds low vehicle speeds high TPS and lots of load (clutch grabbing)? If that's the case then I can only assume that Dodge was dodging the tune, not lumping it. GM used to drive the vehicles with a heads-up controller plugged into an ECM and they would tune on the fly trying every possible scenario. A lot of the tunes are simulations, then real time tuning and if the driver doesn't go into that area of the map it's likely they wouldn't tune it. You'd be surprised at how underdeveloped Dodge is with there onboard electronics. It's almost a joke how many corners they would cut just to make a profit. A lot of there stuff is lacking fine tuning, as you have found. They are in my opinion, the bottom of the barrel when it comes to computer controls. Look at GM and Ford, they know exactly how to do it and still profit.
Out of curiosity, what piggyback computer are you using and what have you done with it?
The IAC in production vehicles is to reduce the emissions from fast closing upstream throttles. They are also used but not limited to usage in cruise control, idle learn, increased idle for small engines with high accessory loads like a/c or alternator, easier to drive with a stick, cold engine warm-up, and "power enrichment" mode for more air if the throttle is a restriction in keeping atmosphere pressures in the manifold for an extended period of time (high gear low vehicle speed). I still fail to see a usage in FSAE. Don't get me wrong, I'm not taking any of this personally. I just don't want to see a team waste there time trying to develop good usage of the IAC without burdening themselves with MORE problems.
Another hint: If you can't get the engine to idle you're tune is really off OR look into vacuum leaks!

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[Ryan Schoffer]

agreed - the IAC has no place in FSAE

as far as my truck, i was able to get the maps off the computer, but not flash adjusted ones back on - from them (and dyno runs) you can see the lump, which assists the IAC in maintaining idle - it was bogging right off idle if you punched the throttle - it would hesitate a bit before picking up, but thats all gone now

the adaptive controls only adjust the map values +- 5% or so from altitude or gas differences

im using a split second FTC-1, since you were wondring, and the dodge electronics arent bad, but their tuning does suck ass, considering i picked up just over 50 horse at the rear whels on a moderatly modified engine with jsut better fuel and spark mapping

strangely enough, i find a car with a manual that has no IAC to be easier to drive than one that has an IAC

go figure

Vehicle electronics leader

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)