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Open Loop - Downside?

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Old Jul 22, 2003 | 11:44 PM
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Default Open Loop - Downside?
Other than emissions- what's the downside of running open loop 100 % of the time????
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Old Jul 23, 2003 | 05:33 AM
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Default Re: Open Loop - Downside? (binksZ06)
The converters could overheat and melt down is the biggest problem area.
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Old Jul 23, 2003 | 02:34 PM
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Default Re: Open Loop - Downside? (binksZ06)
Gas mileage for one..

You can get pretty close to open loop all the time if you lower the Throttle % for PE.. If you ride on the hairy edge you get closed loop cruising and the slightest throttle crack it goes open loop..

I have tuned my car with LS1-Edit this way..

Best Tune I have ever run... :smash:


[Modified by chuckster, 2:35 PM 7/23/2003]
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Old Jul 23, 2003 | 03:35 PM
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Default Re: Open Loop - Downside? (chuckster)
You can easily force the car to stay in open loop by bumping up the Closed Loop Enable Temp table. In open loop the car will not learn fuel trims and relies solely on the Volumetric Efficiency tables and Power Enrichment. This is how I have tuned World Challenge cars that lack oxygen sensors. It if much more difficult to do this way and really requires a load dyno instead of an inertia dyno.

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Old Jul 23, 2003 | 04:02 PM
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Default Re: Open Loop - Downside? (Godspeed)
My C5 did not come with any O2 sensors in the exhaust (see my location). I think our PCM calibration does not depend on any O2 sensors. That's why I think that I run in open loop all the time.

I don't know if that's good though :confused:


[Modified by Corvette4ever, 3:04 PM 7/23/2003]
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Old Jul 23, 2003 | 07:27 PM
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Default Re: Open Loop - Downside? (Godspeed)
You can easily force the car to stay in open loop by bumping up the Closed Loop Enable Temp table. In open loop the car will not learn fuel trims and relies solely on the Volumetric Efficiency tables and Power Enrichment. This is how I have tuned World Challenge cars that lack oxygen sensors. It if much more difficult to do this way and really requires a load dyno instead of an inertia dyno.
Godspeed!!! - that's exactly what I'm interested in. I have the Grand Am cam with SDPC heads and it seems like my best alternative ..especially for off idle tuning. I can't see a way to increse my fueling as I increase throttle input off idle with closed loop tables in Edit. Open loop I can use VE and A/F Mult?. Idle map is 70-85 Kpa abs. (30 -15 Kpa vacuum), Idle= 1275 -1400 RPM. Just off idle as vacuum increases (absolute Kpas decrease) fueling is reduced and it goes lean. Something I've learned -> Wacky Kpas and inadequate Timing advance can have you in PE at IDLE!!!!Hey, I'm learning :D ( I sent you an email a while back). With your/Lou's headers and Borla Stingers this thing sounds awesome above 2500 RPM - feels like turbo - lag hitting me in the back of the head!! :yesnod: :yesnod: :thumbs:
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Old Jul 23, 2003 | 07:33 PM
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Default Re: Open Loop - Downside? (chuckster)
Gas mileage for one..

You can get pretty close to open loop all the time if you lower the Throttle % for PE.. If you ride on the hairy edge you get closed loop cruising and the slightest throttle crack it goes open loop..

I have tuned my car with LS1-Edit this way..

Best Tune I have ever run... :smash:


[Modified by chuckster, 2:35 PM 7/23/2003]
Chuckster -thanks for the input. I've followed your part throttle tuning quest on the Edit list. I think your suggestion may be my best alternative to fulltime open loop. :yesnod: :thumbs:
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Old Jul 23, 2003 | 07:36 PM
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Default Re: Open Loop - Downside? (irfgt)
The converters could overheat and melt down is the biggest problem area.
irfgt- Thanks, I wonder if they would be okay as long as I don't lean it out too much - I have an FJO wideband so I can monitor it more closely?????
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Old Jul 23, 2003 | 07:41 PM
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Default Re: Open Loop - Downside? (Corvette4ever)
My C5 did not come with any O2 sensors in the exhaust (see my location). I think our PCM calibration does not depend on any O2 sensors. That's why I think that I run in open loop all the time.

I don't know if that's good though :confused:


[Modified by Corvette4ever, 3:04 PM 7/23/2003]
Corvette4ever- Hmmmmmmm- that's VERY INTERESTING. You don't have front or rear O2s???? I wish you had LS1 Edit and didn't have Ed Wright Tuning!!! :lol: :lol: :lol: :thumbs:
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Old Jul 23, 2003 | 09:57 PM
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Default Re: Open Loop - Downside? (binksZ06)
You don't have front or rear O2s????
Correct. There are no front or rear O2 sensors. Here is a sample Autotap log file. As you can see it does show a fake value for the front O2 sensor (reading doesn't change under WOT).

Engine Speed,Throttle Pos Ang,O2 Sensor Volts B2S1
1894,18.8,442.7
1898,18.8,447.0
1886,18.8,442.7
2243,100.0,447.0
3429,99.6,451.4
4473,99.2,451.4
4808,99.2,447.0
4897,99.6,447.0
4963,99.2,442.7
5030,99.6,442.7
5114,99.6,447.0
5204,99.6,455.7
5333,99.6,451.4
5487,99.6,447.0
5702,99.6,451.4
5854,99.6,447.0
6008,99.6,447.0
6141,99.6,451.4
6292,99.6,442.7
6449,99.6,451.4
6547,99.6,442.7
6218,99.2,447.0
5098,99.6,442.7
5000,99.6,447.0
5018,99.6,442.7
4958,51.0,451.4
4340,20.8,447.0
4032,19.6,442.7
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Old Jul 24, 2003 | 05:50 AM
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Default Re: Open Loop - Downside? (Corvette4ever)
Corvette4ever - Thanks. Looks like they must have thrown a resistor inline O2 sim) to keep the PCM happy. :thumbs:
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Old Jul 24, 2003 | 06:01 AM
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Default Re: Open Loop - Downside? (Godspeed)
You can easily force the car to stay in open loop by bumping up the Closed Loop Enable Temp table. In open loop the car will not learn fuel trims and relies solely on the Volumetric Efficiency tables and Power Enrichment. This is how I have tuned World Challenge cars that lack oxygen sensors. It if much more difficult to do this way and really requires a load dyno instead of an inertia dyno.
I have a wideband O2 for my tuning. Does this simulate a load dyno?
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Old Jul 24, 2003 | 06:02 AM
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Default Re: Open Loop - Downside? (chuckster)
Gas mileage for one..

You can get pretty close to open loop all the time if you lower the Throttle % for PE.. If you ride on the hairy edge you get closed loop cruising and the slightest throttle crack it goes open loop..

I have tuned my car with LS1-Edit this way..

Best Tune I have ever run... :smash:


[Modified by chuckster, 2:35 PM 7/23/2003]
I saw your prior posts about this and I have to say that I'm impressed. Great research!!! :cool:
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Old Jul 24, 2003 | 10:17 AM
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Default Re: Open Loop - Downside? (SpinMonster)
I have a wideband O2 for my tuning. Does this simulate a load dyno?
Not exactly, a wideband will give you a good air fuel reading though. The problem with a inertia dyno like a dynojet is that you can not vary the load. Pretty much you are tuning at WOT only. With a load dyno you can bring the car up to a fixed RPM (say 1200RPM) and then start increasing the load at that same RPM. Then you can increment up to the next RPM and start over with the load. This is the most effective way to build a good open loop tune in my opinion.

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Old Jul 24, 2003 | 10:48 AM
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Default Re: Open Loop - Downside? (Godspeed)
You can easily force the car to stay in open loop by bumping up the Closed Loop Enable Temp table. ....
Godspeed,

Do you know what the closed loop enable temperature is for an unmodified car? The service manual just states "specified temperature" ?

Is there a possibility that running a lower temperature thermostat (would keep a car in open loop operation longer) contributes to the need to "decarb" the engine?

thanks
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Old Jul 24, 2003 | 12:45 PM
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Default Re: Open Loop - Downside? (mapman)
Do you know what the closed loop enable temperature is for an unmodified car? The service manual just states "specified temperature" ?
It's based on coolant temp. On my 2000 it is enabled at 60C from -40c to -20C, then it's 33.5C from -10C up to 140C


Is there a possibility that running a lower temperature thermostat (would keep a car in open loop operation longer) contributes to the need to "decarb" the engine? thanks

No, given that the enable temp is like 90 degrees F. you would have to keep it below that.
Besides a themostat alone will not lower temps without lowering fan on temps.
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Old Jul 24, 2003 | 08:00 PM
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Default Re: Open Loop - Downside? (binksZ06)
Any other opinions or suggestions regarding running fulltime open loop or open loop tuning?????
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Old Jul 24, 2003 | 10:17 PM
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Default Re: Open Loop - Downside? (binksZ06)
Any other opinions or suggestions regarding running fulltime open loop or open loop tuning?????
Do you have ls1edit? If so go ahead and make that part throttle tuning change I mentioned.. You will love it!
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Old Jul 24, 2003 | 11:40 PM
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Default Re: Open Loop - Downside? (chuckster)
Any other opinions or suggestions regarding running fulltime open loop or open loop tuning?????

Do you have ls1edit? If so go ahead and make that part throttle tuning change I mentioned.. You will love it!
Charlie- Yes, I have Edit and EFILive. I think I'll try (using the Main VE table)1.) leaning it out between 0 - 1200 RPM at 0 - 80 MAP to reduce the fatness at idle ( idles at 1275 RPM @ 70- 85 Abs. Kpa. 2.) Then richen it up between 40 - 80 Map at 1200 - 2000 RPM to help with the off idle vacuum increase and subsequent reduced fueling. If this doesn't work I'm going open loop fulltime. I'll set the closed loop Enable Temp to 140*C and tune with IFR,VE
and PE (The FJO Wideband should help Bigtime). I guess I'll need to find a tuner with a load dyno at some point. Thanks for all of the input! :yesnod: :yesnod: :thumbs:


[Modified by binksZ06, 11:44 PM 7/24/2003]
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