Idle Air control

[al lkosmal]

i am planning to provide an Idle Air Control option for my ITB kits.....eventually providing a MAP manifold with the option built into the manifold....but 1st, it has been a while since I've incorporated IAC into one of my systems.........so luckily, one of my local friends, Rick......who has the x-faktory PMO/Megasquirt system I installed a while back in his 911SC ( the infamous Dildorado) volunteered to be my Beta tester.

I have not typically installed an IAC valve on the 911 ITB systems...instead opting for simplicity and tuning/timing to provide good cold/warm starting....however, for this mini-project the intent is to plumb the IAC valve into the system to provide much improved cold starting...basically will make it start like a flippen new Toyota.

I did use the IAC valve that came with the Triumph Speed Triple ITBs on a couple of my 1st ITB systems and the worked well.....but for this project, I've opted for the IAC system from DIY Autotune (who i buy my M'squirts from), that is designed to be used with the valve from a Jeep.

This.......



Goes in here.........



stay tuned......

[Jeff Higgins]

Rick has had trouble with cold starts for as long as I've known him. His car has always run fine, though.

[al lkosmal]

Originally Posted by Jeff Higgins

Rick has had trouble with cold starts for as long as I've known him. His car has always run fine, though.

yep...so sad....definitely some "air control" issues as well.

[jpgroth]

Sweet! I’m assuming this is stepper style? What Megasquirt is the test car running? MS2 3.57?

[RSBob]

Originally Posted by Jeff Higgins

Rick has had trouble with cold starts for as long as I've known him. His car has always run fine, though.

D@m you Higgins!

[al lkosmal]

Originally Posted by jpgroth

Sweet! I’m assuming this is stepper style? What Megasquirt is the test car running? MS2 3.57?

Yes & yes.......

[shamrok]

I've been eyeing this very thing, as cold weather starts are my only lingering issue and I'd love to just start it like a Camry.

I see 2 vacuum barbs, one to the manifold, the other to what? Just plumb one of the 6 lines (e.g. from cylinder 1) from the ITBs onto this, then the IAC to the manifold?

[shamrok]

Hey Al, just wanted to bump this and see if you've got this figured out. The air plumbing is probably my biggest question mark at this point. I think I'm going to eliminate my vacuum manifold and just run my FPR from the right bank of ITBs, and possibly run the IACV to the left bank? Or should the IACV plumb into the manifold and push air to all 6 throttles?

[al lkosmal]

Shamrok,
I do have this working pretty well. The air plumbing is pretty straight-forward. There are two ports in the IAC valve mounting block. The one farthest from the IAC valve is for incoming air (I added a small filter to a short length of hose) and the other port is the air outlet, controlled by the valve. This gets routed to the intake for idle air. Since my test setup was Independent Throttle Bodies, I routed the IAC valve outlet to the Vacuum manifold, which in turn, routes the air to the Intake. This manifold is used to average out the MAP signal. This is important for Speed Density type tuning mode.

My 1st approach was to route all 6 ITB vacuum hoses to the manifold...However, i found that when the IAC valve was full open for cold starts......the map signal would peg as if the throttle was wide open and as it warmed and closed, the VE cells used would be some of the same ones used for normal idling/no-load/low load revs......so i could achieve either great cold starts or great idles and tip-in...but not both at the same time...I soon realized that there is definitely a delicate balance required between the cold start fuel enrichments and the IAC valve position and temperature, timing etc...... after much testing, it is working quite well.

As I was experimenting, I tried routing two of the ITB vacuum lines directly to the MAP sensor, with the remaining four routed to the IAC valve. I'm not sure this is Kosher, but it worked great......excellent MAP signal and good IAC control......that combined with pretty rich after-start enrichments and warm-up enrichments and wide open IAC at very cold temps....that tapers off quickly as the engine warms was the right combo..... you only get one truly cold start/day...maybe two, so this can take some time to dial in at different temps.

I bent up a simple mounting bracket and used the mounting studs formerly used for the throttle bellcrank.....works good, but I'd be tempted to install this in a more hidden location ....next time.

Note: The 911 I tried this on is tuned using Speed Density, so having a strong MAP signal with good resolution is a must for good tuning....and this car has been running quite well for a couple of years, so i did not want to change the tuning at all, if not required.

However, if you are tuning with Alpha-N mode (TPS) that does not rely on the MAP signal for indication of engine load....the tuning/IAC interaction may be minimized........

Anyway, it works great with good cold start down to 35F or so.........





While I was working on this, my friend Rama, from RHD Engineering sent me a vacuum manifold he designed with the IAC mount threaded directly into it.....for a smaller package and tidier install......that will be my next test unit....maybe

[evan9eleven]

Al, I’ll bet your setup with the Jeep IAC will be the bees knees. Having had ITBs in the car for a couple seasons now, I can honestly say that this is a must-have addition, at least in colder climates.

I don’t want to hijack the thread here, so apologies in advance, but here is a little info on my setup. I can imagine switching out to the new IAC from Al in the future, and as he said in a more hidden location. But for now it is in and working great.

A while back Al sent me a Triumph IACV. Its a 4-wire stepper motor type, so I connected it up to my Megasquirt 2 ECU and confirmed it was alive and working. I decided the best place to add idle air would be on the vacuum manifold connected to my ITBs— I’m tuned on Alpha-N and not MAP, so just getting more air into all 6 throttles with fuel added should do the trick. So I drilled out a threaded plug for one end of the manifold and welded in a hose barb:




Here is the air inlet installed:




Then on to making a common manifold for the Triumph IACV. This way I could have one hose connection feeding the multiple connections on the valve. I also rigged up a little air filter:






Here is the IACV installed in the car:





I ended up with a combo of lots of cranking air and fuel, followed by a big dose of After Start Enrichment (ASE), all of these amounts tapered off by temperature. The Warm Up Enrichment (WUE) follows the same curve I set up for my car otherwise. The colder the engine is, the more air and fuel it gets, and as it warms up these get tapered off until everything is humming along nicely. It took a lot of cold mornings to get this right, but it was worth it— works great!

Now back to your regularly scheduled X-Faktory feed!


.

[al lkosmal]

Evan,
greetings and thank you for sharing your IAC experience. Evan and i have been sharing IAC tuning tips. When I 1st started adapting the Triumph speed triple ITBs to 911s....I ended up with a box full of those IAC valves......they work great. I initially installed one on the 1st ITB kit i built & tested......it worked very well, but that was on the engine stand and you and i both know....it takes some testing , under different loads/temps to dial these in

I went to my youtube channel and found the video of my 1st EFI with IAC valve install. you can just barely see the Triumph IAC valve, mounted over the breather cover......it's taken me 10 years to feel the need to play with these again......enjoy

[evan9eleven]

Thanks Al... I know that video well. It lured me to the slope... good memories.

[shamrok]

Al and Evan, thanks for the info. Great stuff, lots to absorb. I'm currently scheming a different way to route all my vacuum lines to clean things up...mostly cuz I can't just leave well enough alone.

[al lkosmal]

Here is another alternative to consider. The early 911s had a manual throttle.......a simple , mechanical, cold-start device. Combined with proper fueling at different temps.....these work great too! Old school, combined with new engine management is a good thing.


regards,
al