My PMO ITB Project

[Trog]

Originally Posted by dfink

Did you use an idle air control valve, if so which one and how did you plumb it.

To be quite honest, I have no idea how I would go about plumbing in an ICV? The engine seems to idle rather nicely without one.

[TimT]

With ITBs an idle control valve is kind of difficult. You end up setting idle speed by adjusting the throttles. Not a value entered in the ECU

[dfink]

TimT and Trog thanks for the info. I couldn't figure out how it would be done so I guess one less thing to worry about. Plenty of others.

[scarceller]

You could achieve some idle control and stability by simply doing it via idle ignition map. I currently do this in my 3.2L Motronic in addition to the ICV.

The idea is to set the ignition to some value that works well at the target idle. For example: say the target idle is 880RPMs and the ignition is set to 0deg. Then in the map you simply advance the ignition if the idle drops below the target and retard if the idle increases above the target.

In my car the target idle is 920RPMs and ignition is set to 5deg BTDC if the idle drops I start advancing the idle as much as 11deg BTDC if it drops to 800RPMs. Then I also retard to -3deg ATDC if it increases to 1000RPMs.

You would be surprised how much you can influence the idle by simply altering the ignition at idle. Adjusting idle in this manner also compensates much faster than a mechanical ICV valve.

I'd hope that any modern day Engine Managment System could do this.

[Trog]

The TECgt allows for TPS input for idle purposes. Should the MAP prove to be excessively erratic at idle (due to Hi perf cams), then it's an easy matter to dial in TPS sensor inputs.

[scarceller]

Originally Posted by Trog

The TECgt allows for TPS input for idle purposes. Should the MAP prove to be excessively erratic at idle (due to Hi perf cams), then it's an easy matter to dial in TPS sensor inputs.

Trog, the TPS measures throttle position, right? But at idle the throttle plate does not move so the TPS value should never change once the idle is set. Am I missing something? I'm sure the TPS signal is used to setup the target idle but I don't see how it could help correct a drifting idle.

Common causes for idle drift are things like Alternator Load and AC Load. Without idle compensation idle often will drift/drop by simply turning on the headlights which cause Alternator Charging system load.

[dfink]

What are all the little cams for that come with the TPS?

[Trog]

Originally Posted by scarceller

Trog, the TPS measures throttle position, right? But at idle the throttle plate does not move so the TPS value should never change once the idle is set. Am I missing something? I'm sure the TPS signal is used to setup the target idle but I don't see how it could help correct a drifting idle.

The Throttle Position Sensor (TPS) wont correct for a drifting idle, but it reduces the effect of the erratic MAP signal at idle.

As you reported, the timing map would address any drift.

[Trog]

Originally Posted by dfink

What are all the little cams for that come with the TPS?

Little engines?

Are you making reference to the throttle linkages?

[scarceller]

Originally Posted by Trog

The Throttle Position Sensor (TPS) wont correct for a drifting idle, but it reduces the effect of the erratic MAP signal at idle.

As you reported, the timing map would address any drift.

I understand that using only MAP at hi intake vacuum (lo-load) would be tricky so they also use TPS. Makes sense, thanks for clearing this up.

[dfink]

Originally Posted by Trog

Little engines?

Are you making reference to the throttle linkages?

That's a good one.
In the package with the throttle sensor were several little round clips that look like cams. Looked up the CTS TPS sensor on the internet but they didn't show them. The TPS just attaches direct to the throttle shaft from what I can tell.

[Trog]

Originally Posted by dfink

That's a good one.
In the package with the throttle sensor were several little round clips that look like cams. Looked up the CTS TPS sensor on the internet but they didn't show them. The TPS just attaches direct to the throttle shaft from what I can tell.

Those clips are used to lock the fuel injectors into the fuel rail. I needed to file the clips to get them to slide in. They're really tight.

T...

[Trog]

Originally Posted by MrPerkles

great vid and neat install ,how tempting is it to run without airfilters and show of those lovely trumpets

Best of both worlds:

[scarceller]

Trog,

I saw your video, very nice to have it running now.

Did you start monitoring with your WBO2 yet? If so what's your AFR at idle?

[Trog]

Originally Posted by scarceller

Trog,

I saw your video, very nice to have it running now.

Did you start monitoring with your WBO2 yet? If so what's your AFR at idle?

The initial cold idle AFR is approx 10:1

After 5-minutes running, it gets to 12:1

The cold engine enrichment bias appears to be a tad generous. Plus, the ambient air is pretty cold up here this time of year (approx 10degC).

I plan to start tuning this weekend.

T...

[scarceller]

Originally Posted by Trog

The initial cold idle AFR is approx 10:1

After 5-minutes running, it gets to 12:1

The cold engine enrichment bias appears to be a tad generous. Plus, the ambient air is pretty cold up here this time of year (approx 10degC).

I plan to start tuning this weekend.

T...

In my car (stock 3.2 Motronic) cold AFR=12.8 to 13.4, depends how cold it is.

Once warm at idle (open-loop no O2) I have it set to AFR=14.2 and this makes for nice smooth idle.

I also found that idle timing between 0 to 5 deg advance works well for idle.

Hope these help.

[Trog]

Originally Posted by scarceller

In my car (stock 3.2 Motronic) cold AFR=12.8 to 13.4, depends how cold it is.

Once warm at idle (open-loop no O2) I have it set to AFR=14.2 and this makes for nice smooth idle.

I also found that idle timing between 0 to 5 deg advance works well for idle.

Hope these help.

I would be happy with those numbers.

[Trog]

With the help of Richard Clewett, I’m now ripping up and down the street logging data for fine tuning. The idle AFR was much too rich, so I had to reduce the IOT value. (“IOT” is the value in the TECgt that is equivalent to the idle jets in a carb). I still need to set the TOG value correctly in order to set the base-line fuel curve. However she’s running pretty good as-is.

First driving impressions...... Well I don’t really know if the car is any faster, but the sounds out the rear are sublime!!!! Sounds like something out of Formula-1.

Throttle response is instantaneous. My neighbors are going to hate me.

Trog

[porschenut]

Trog, this is one of the most informative threads I've ever seen in almost 5 years on this site - outstanding work, and many thanks for documenting all this for us.

Anything interesting new to report? I'm curious how the tuning went.

[dfink]

Originally Posted by Trog

With the help of Richard Clewett, I’m now ripping up and down the street logging data for fine tuning. The idle AFR was much too rich, so I had to reduce the IOT value. (“IOT” is the value in the TECgt that is equivalent to the idle jets in a carb). I still need to set the TOG value correctly in order to set the base-line fuel curve. However she’s running pretty good as-is.

First driving impressions...... Well I don’t really know if the car is any faster, but the sounds out the rear are sublime!!!! Sounds like something out of Formula-1.

Throttle response is instantaneous. My neighbors are going to hate me.

Trog

Two hours at a dyno and you would be done. I tried the bring it in slow method didn't work well, too slow. Then Richard said I had to find the maximum first in your case TOG in my case UAP. That means full load pulls all the way to what ever you decide on for redline. Then back down load to make sure that is OK then back high again. The VE table should be nearly all 0 when completed. My only problem right now is that when I am doing really hard full loads my cylinder head temp reading is going to 5V and fails. Not sure what it will read on a track. This is only on a dyno. Oil temps all look pretty good. I am using an old factory sensor which may also be part of the problem.