How to idle 272 cams with Utec
Thread Starter
Evolved Member
Joined: Sep 2003
Posts: 646
Likes: 0
From: Houston
How to idle 272 cams with Utec
Ok guys, after several attemp to idle my 272s, I gave up. Utec seems to be complete helpless when it comes to tweaking the idle speed. I added fuel at idle, which help bring it back to 14.7. I set my camgears to -4,-1. When it's really cold out, especially at night, my idle jump from 13-18 afr. It never stalled out, but just really annoying.
Is there anything I can do with the utec to help smooth out the idle? I also adjusted the BISS out a bit to let it idle at 900-1000rpm. During the day, it's fine, but only at night when it's cold out. Any help be awesome!
P.S looks like I can use Al's "idel flash".
Is there anything I can do with the utec to help smooth out the idle? I also adjusted the BISS out a bit to let it idle at 900-1000rpm. During the day, it's fine, but only at night when it's cold out. Any help be awesome!
P.S looks like I can use Al's "idel flash".
Evolving Member
Joined: Jun 2003
Posts: 106
Likes: 0
I have to say I didn't see why there was so much talk of 272s idling UNTIL I put a cold air box around my open air filter. Prior to the cold air box, it idled just great with very little tuning. Idle got a lot worse and the entire fuel map had to be retuned after the box install...presumably from the change in IAT reading, but oddly, idle went way lean and load went way rich.
In any event, try setting timing in your idle RPM area (0%, 750-1000RPM). Timing bounces around a lot at idle with the cams and setting your own timing will help. You can try starting with 10-15°, but I've got mine bumped up to about 20° right now and am also adding a bunch of fuel in the same idle areas. Without the cold air box, my idle fueling was only +15%, after the cold air box I had to bump it up to about +24%.
AFR will also jump around at idle from a combination of the cams and the ECU trying to trim the O2 (bouncy timing doesn't help). Mine more or less stays about 14.3:1, but every once in a while when the cams trip over themselves, it will flip between 16.x and 13.x:1 as it falls and corrects.
HTH
In any event, try setting timing in your idle RPM area (0%, 750-1000RPM). Timing bounces around a lot at idle with the cams and setting your own timing will help. You can try starting with 10-15°, but I've got mine bumped up to about 20° right now and am also adding a bunch of fuel in the same idle areas. Without the cold air box, my idle fueling was only +15%, after the cold air box I had to bump it up to about +24%.
AFR will also jump around at idle from a combination of the cams and the ECU trying to trim the O2 (bouncy timing doesn't help). Mine more or less stays about 14.3:1, but every once in a while when the cams trip over themselves, it will flip between 16.x and 13.x:1 as it falls and corrects.
HTH
Thread Starter
Evolved Member
Joined: Sep 2003
Posts: 646
Likes: 0
From: Houston
Thx blackEVo for the reply. I did try to add timing and fuel, but I guess I didnt add enough. I added about 5% at 0% load site. It brought the idle back up to 14.7-.9, but the idle jumps around so much. Timing jumps from 2-13 degrees with afr go as low as 18-19. I'm going to attempt to start adding more fuel and timing.
By the way, I also have an open air intake, which I wish I can go back to stock. But since the car is "too modded", I can't go back. I'll let u guys know what's up with the idle.
By the way, I also have an open air intake, which I wish I can go back to stock. But since the car is "too modded", I can't go back. I'll let u guys know what's up with the idle.
Evolving Member
Joined: Jun 2003
Posts: 106
Likes: 0
Just keep messing with it...you'll get it. You've already adjusted the idle speed, so just concentrate on what you can do with the UTEC. Yeah, I was a little surprised about the amount of fuel I needed to add (on 650s), but unless the wideband is lying, that's where it needs to be.
I've tried as high as 30% on the fuel and 25° on the timing, but it didn't seem to make much of a diff, so I went back to what it was.
When all is said and done, other than allowing the IAT to read cooler temps and the Karman to see denser air (both of which can be tuned around). I actually wanted to try the box just to see what would happen. My IC piping won't allow me to use the stock box either, so I installed an Apex box + PE filter kit. For all the work, temps at the filter were much cooler (ambient+1° = 89°F) compared to 124°F peak where the filter sat without the box (thermocouple measured, not log data). 36°F cooler sounds really impressive, but as I expected, it translated to ZERO measurable difference on the FMIC outlet (AMS FMIC w/GM IAT tapped in). Maybe cooler outlet temps would be translated more on less efficient FMICs/boost levels? Don't know.
The cooler air in should translate into some kind of efficiency/mass benefit through the compressor, but if there are any "big gains" coming from it, I certainly haven't seen them.
The logic is there, the physics are there and there is a big measureable diff in temps before the turbo (and presumably to the FMIC inlet) between box/no box, BUT I just don't see it manifesting itself greatly between the FMIC outlet and wheels. In short, it certainly couldn't hurt to have a box (probably moreso if you road race and the like), but I wouldn't be overly concerned about not having it if you have tuning control....and you do
I've tried as high as 30% on the fuel and 25° on the timing, but it didn't seem to make much of a diff, so I went back to what it was.
When all is said and done, other than allowing the IAT to read cooler temps and the Karman to see denser air (both of which can be tuned around). I actually wanted to try the box just to see what would happen. My IC piping won't allow me to use the stock box either, so I installed an Apex box + PE filter kit. For all the work, temps at the filter were much cooler (ambient+1° = 89°F) compared to 124°F peak where the filter sat without the box (thermocouple measured, not log data). 36°F cooler sounds really impressive, but as I expected, it translated to ZERO measurable difference on the FMIC outlet (AMS FMIC w/GM IAT tapped in). Maybe cooler outlet temps would be translated more on less efficient FMICs/boost levels? Don't know.
The cooler air in should translate into some kind of efficiency/mass benefit through the compressor, but if there are any "big gains" coming from it, I certainly haven't seen them.
The logic is there, the physics are there and there is a big measureable diff in temps before the turbo (and presumably to the FMIC inlet) between box/no box, BUT I just don't see it manifesting itself greatly between the FMIC outlet and wheels. In short, it certainly couldn't hurt to have a box (probably moreso if you road race and the like), but I wouldn't be overly concerned about not having it if you have tuning control....and you do
There is one thing that gets tricky, I posted this in another thread.. cold start and cold idle, most of the stuff your battling is your trying to work around while fighting with closed loop fuel control.. You need to somehow force the car into open loop control..
FWIW when you get very weird anomolous readings, the car drops out of closed loop fueling, into open loop, it tries to stabilize timing and fuel by using a base value (usually starts with the base map and offsets what the trims insist it should be) I have personally seen this, then my idle would drop and the AFR's would swing to very rich.. When idle speed came back up, and it stabilized again, it would go back into closed loop...
So the trick to resolve this without fighting with the closed loop is to somehow disable it (disconnect the front O2 sensor) and get your idle as stable as possible, then reconnect the O2 sensor and clear the CEL code.. reset the ECU and see if that helps.
with Cams you'll need to try to maintain around 1000rpm (900 is ok too) but keep in mind that until the ECU finishes learning, putting on the A/C or loading the engine slightly from the alternator (Headlights, defogger, etc... at the same time) could let the RPM's drop and stall..
Like everyone said, its going to take time to resolve, everyone ends up dealing with this stuff regardless of your engine management, most won't notice issues until the weather gets really cold and the car runs in open loop for an extended time and runs lean, lean is bad (remember the Choke on older carb cars, its a fuel enrichment feature) You basically need to do something similar when the car is in open loop..
When your dealing with really cold temps IAT values, the ECU may be trying to go into an enrichment mode, and further throwing things off..
FWIW when you get very weird anomolous readings, the car drops out of closed loop fueling, into open loop, it tries to stabilize timing and fuel by using a base value (usually starts with the base map and offsets what the trims insist it should be) I have personally seen this, then my idle would drop and the AFR's would swing to very rich.. When idle speed came back up, and it stabilized again, it would go back into closed loop...
So the trick to resolve this without fighting with the closed loop is to somehow disable it (disconnect the front O2 sensor) and get your idle as stable as possible, then reconnect the O2 sensor and clear the CEL code.. reset the ECU and see if that helps.
with Cams you'll need to try to maintain around 1000rpm (900 is ok too) but keep in mind that until the ECU finishes learning, putting on the A/C or loading the engine slightly from the alternator (Headlights, defogger, etc... at the same time) could let the RPM's drop and stall..
Like everyone said, its going to take time to resolve, everyone ends up dealing with this stuff regardless of your engine management, most won't notice issues until the weather gets really cold and the car runs in open loop for an extended time and runs lean, lean is bad (remember the Choke on older carb cars, its a fuel enrichment feature) You basically need to do something similar when the car is in open loop..
When your dealing with really cold temps IAT values, the ECU may be trying to go into an enrichment mode, and further throwing things off..
Trending Topics
Evolving Member
Joined: Jun 2003
Posts: 106
Likes: 0
So the trick to resolve this without fighting with the closed loop is to somehow disable it (disconnect the front O2 sensor) and get your idle as stable as possible, then reconnect the O2 sensor and clear the CEL code.. reset the ECU and see if that helps.
Can I ask how you were able to tell at idle that it was going into open loop and it wasn't just a closed loop fuel trim swinging the AFR? AFAIK, on DSMs, a reading needs to completely out of range (ie. trashed signal/no signal = dead or disconnected sensor) for it to resort to the base tables...
