Open loop idle surges? $61
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Car: 1980 Jeep CJ7
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Open loop idle surges? $61
Started playing with the open loop tables today. AFAICT, there are only two of them (Open Loop AFR vs CT and Open Loop AFR vs Vac). On initial startup, the engine likes to "hunt" or surge at idle speed. Once it's in closed loop, the idle changes dramatically...MUCH smoother and consistent at 750 rpm with only a minor fluctuation of about 70 rpm either way...hardly even noticeable if you weren't looking at an ALDL screen.
Anyway, I doubt this is a vacuum leak because the idle is so good once it goes into closed loop. You can actually HEAR when the ECM sets C/L.
Any suggestions? Could I disable C/L and try to tune it out like that?
Anyway, I doubt this is a vacuum leak because the idle is so good once it goes into closed loop. You can actually HEAR when the ECM sets C/L.
Any suggestions? Could I disable C/L and try to tune it out like that?
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Car: 1980 Jeep CJ7
Engine: AMC 360 with GM TBI
Transmission: TF727 set for kill...let's get it on!!!
Here's the open loop vs CTS graph. The Jeep idles at about 195F and 50-55 kPa at 750 rpm +/- 70 rpm.
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Car: 1980 Jeep CJ7
Engine: AMC 360 with GM TBI
Transmission: TF727 set for kill...let's get it on!!!
Here's the Open Loop vs Vac graph.
Help please!!! :hail:
Help please!!! :hail:
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Graphs are a little hard to read. . .
I can see why the problem. Take the two graphs at the CTS & MAP points the idle is at, add them together, and it is about 16.9:1 AFR.
Closed loop is at 14.7:1.
RBob.
I can see why the problem. Take the two graphs at the CTS & MAP points the idle is at, add them together, and it is about 16.9:1 AFR.
Closed loop is at 14.7:1.
RBob.
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Car: 1980 Jeep CJ7
Engine: AMC 360 with GM TBI
Transmission: TF727 set for kill...let's get it on!!!
That would explain it. Thanks Rbob! So basically, I need to make sure that the open loop stuff adds up to 14.7 at the idle point. Now I can see why Grumpy says this shouldn't be done without adult supervision. If I have a 16.x:1 AFR in O/L idle, that is probably really bad for the engine. PING CITY. BUT, I am not logging or hearing any detonation out of it. Strange...
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Car: 1980 Jeep CJ7
Engine: AMC 360 with GM TBI
Transmission: TF727 set for kill...let's get it on!!!
This kinda begs the question...How do you anticipate for the myriad ranges of MAP and CTS combinations that are possible?
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Car: 1980 Jeep CJ7
Engine: AMC 360 with GM TBI
Transmission: TF727 set for kill...let's get it on!!!
Combine the two. Now you have a 3d table being made out of two 2D tables with what I see as many possible combinations of values.
Am I nuking this out?
Am I nuking this out?
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Its not really a 3d table of course, but the easy way to think of it is::: the ecm looks at one talbe first, then after say, the given map value is found, it then searches for the given cts value.
I'm sure in newer model vehicles, the computer has a nice 3d table for open loop afr, but we have limited space in ours, so gm I guess, thought this dual 2D table would do.
Its been said before, but its too bad that were stuck with all that EGR crap, that has alot of memory tied up.
So your right in thinking that the tables will give afr's that probably are a little off, but I think that it works OK.
I'm sure in newer model vehicles, the computer has a nice 3d table for open loop afr, but we have limited space in ours, so gm I guess, thought this dual 2D table would do.
Its been said before, but its too bad that were stuck with all that EGR crap, that has alot of memory tied up.
So your right in thinking that the tables will give afr's that probably are a little off, but I think that it works OK.
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Car: 1980 Jeep CJ7
Engine: AMC 360 with GM TBI
Transmission: TF727 set for kill...let's get it on!!!
Another question from that one...which happens first...the CTS lookup or the MAP lookup? That in itself would answer a lot of questions. If you knew that, tuning O/L might take a completely different turn.
I have an idea here....before I post it, I want to see if it works. Results tomorrow or Wednesday. I have to put a comprehensive Genetics final together tomorrow morning.
Thanks for the input gents! It kinda fueled my fire.
I have an idea here....before I post it, I want to see if it works. Results tomorrow or Wednesday. I have to put a comprehensive Genetics final together tomorrow morning.
Thanks for the input gents! It kinda fueled my fire.
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Originally posted by jeepguy553
Another question from that one...which happens first...the CTS lookup or the MAP lookup? That in itself would answer a lot of questions. If you knew that, tuning O/L might take a completely different turn.
I have an idea here....before I post it, I want to see if it works. Results tomorrow or Wednesday. I have to put a comprehensive Genetics final together tomorrow morning.
Thanks for the input gents! It kinda fueled my fire.
Another question from that one...which happens first...the CTS lookup or the MAP lookup? That in itself would answer a lot of questions. If you knew that, tuning O/L might take a completely different turn.
I have an idea here....before I post it, I want to see if it works. Results tomorrow or Wednesday. I have to put a comprehensive Genetics final together tomorrow morning.
Thanks for the input gents! It kinda fueled my fire.
The Open Loop AFR vs. Map is a lookup done 40 times a second.
Coolant temperatures don't change too quickly.
Shouldn't see ping at idle as there is very little load on the engine.
JP did something where he combined the two tables and displayed them as a 3d table. For viewing purposes only. Should be able to hack out an Excel dohicky for this.
RBob.
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Originally posted by RBob
Graphs are a little hard to read. . .
I can see why the problem. Take the two graphs at the CTS & MAP points the idle is at, add them together, and it is about 16.9:1 AFR.
Closed loop is at 14.7:1.
RBob.
Graphs are a little hard to read. . .
I can see why the problem. Take the two graphs at the CTS & MAP points the idle is at, add them together, and it is about 16.9:1 AFR.
Closed loop is at 14.7:1.
RBob.
Originally posted by jeepguy553
So basically, I need to make sure that the open loop stuff adds up to 14.7 at the idle point.
So basically, I need to make sure that the open loop stuff adds up to 14.7 at the idle point.
Open Loop AFR vs. Coolant @ 49.7 Deg C = 13.30
+
Open Loop AFR vs. Vacuum @ 50 Vac kpa = 2.40
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Engine: check
Transmission: check
Originally posted by adambros
If this is the case, why is a 15.7:1 AFR achievable on the factory APTX.bin ?
Open Loop AFR vs. Coolant @ 49.7 Deg C = 13.30
+
Open Loop AFR vs. Vacuum @ 50 Vac kpa = 2.40
If this is the case, why is a 15.7:1 AFR achievable on the factory APTX.bin ?
Open Loop AFR vs. Coolant @ 49.7 Deg C = 13.30
+
Open Loop AFR vs. Vacuum @ 50 Vac kpa = 2.40
RBob.
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Originally posted by adambros
If this is the case, why is a 15.7:1 AFR achievable on the factory APTX.bin ?
Open Loop AFR vs. Coolant @ 49.7 Deg C = 13.30
+
Open Loop AFR vs. Vacuum @ 50 Vac kpa = 2.40
If this is the case, why is a 15.7:1 AFR achievable on the factory APTX.bin ?
Open Loop AFR vs. Coolant @ 49.7 Deg C = 13.30
+
Open Loop AFR vs. Vacuum @ 50 Vac kpa = 2.40
It's amazing how rich they have the AFRs in open loop as well. Kind of makes you wonder if that's why the ANLU calibration has a lower VE after 80kpa (90 and 100kpa have less fuel). Very strange things.
As for the program that displays the AFR, let me compile it and work out a few bugs. The software is a tuner that does all the complicated tables and gives you actual values. I was going to wait until I finished the VE table adder (also helps visualize the tune) but the Main SA table has a LOT of compensation tables that make it hard to program. I get lost in my visual basic code when the program gets this large.
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