I am still workinh on the 85 vette. I have my 7730 installed for some diacom scanning and help in finding the bug. car still will nto run good.
I want to see if the car will run in open loop ok. question.
I set closed loop enable to 250 degrees. basically so it will not enable.
Is there a O2 reading I should try to achieve so no damage to the motor.I belive the O2 will stay constant just like WOT.
but at idle should the O2 mv be near 600??

Merry christmas to all
Dennis

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85 vette,383,miniram,ZF6,4.10's..best ET 11.66@1187.00 60' 1.62
w/100HP nirous 11.05@127
http://geocities.com/bowtie8

 

The oem ones are of the switching type. Less than .44 is leaner the 14.7:1 and richer then 14.7 is over .44v

14.7 is strictly an emission AFR.
Engines can idle and cruise at leaner AFRs then that. Some SBCs can go down to 15.8 at those areas of operation.
Too lean at cruise and idle are quite noticable. Lean enough to do damage in cruise drives miserablely, IMO. If you have highway fuel in your calibration even in close loop you can run down to O2 that are less then .2..
The ecm can estimate AFRs other then 14.7:1, based on what it takes to run 14.7 before swtiching to Highway mode.

 

You can program in open loop, although I have never done it with a stock O2, always wide band, so I don't know what voltage to recommend, but I think your 600-650mv should be close enough. When the prom gets close I usually turn off the Block Learns and just use the integrator, I usually shoot for ~123 integrator number as this seems to give a much better/smoother transient response. If the injector constant is correct it usually equates to 1 integrator number is one number in hex. This is also considering you haven't scewed the P/I (proportional/integral) controls as well. Did you fix the vacuum leak yet??? Did vacuum rise??? What is the diff between this cam and the 219 cam you were using??
-Carl

[This message has been edited by InTech (edited December 25, 2000).]

 

Q about the stock O2,

as ive been tuning, ive noticed that I had some areas that were rich and some were lean, as i whittle away at getting it closer I notice the O2 is now bouncing around a hell of alot. All I did was lock BLM and INT at 128 to keep the o2 from cycling and it seemed to work until I presume I got it closer to 14.7.. Does the o2 get extremely sensitive as it gets down to .440 such that its nearly impossible to hold a steady .440 like it would if it were much richer? (in the spots that it was rich it would hold .650 pretty steadily until i leaned it out.. now it seems to bounce around between .1 and .6 and everything inbetween

[This message has been edited by Pablo (edited December 26, 2000).]

 

Pablo,
As the engine becomes lean to this point it will lose a little vacuum which usually makes it "bounce" to the higher KPA numbers, therefore giving you the O2 swing you are seeing. Again, once I am to the point where you are at, I turn on the integrator only so you can fine tune what the algo is actually doing, keep in mind that differences in timing between different KPA cells can induce or reduce scavenging and therefore alter tuning. hth's
-Carl

 

thanks Carl, do you suggest going after the spark table at this point? Since timing can increase/decrease scavenging etc. I have the timing table pretty well roughed out but havent focused on it it would probably make sense to get that closer and then get back to the fuel side right

 

btw dennis, be sure to set up your coolant afr in clsd loop table to read 14.7:1 (if the 730 has one i presume it does) also, the 7747 has a table for AFR adder vs map and that also affects your closed loop AFR calc... not sure if the 730 has it but you could end up working against yourself if you dont zero that out or just make sure the two tables add up to 14.7 exactly

I just locked out blm and Int myself

 

Pablo,
Are you sure your response to Dennis you didn't mean open loop AFR??? anyway, I would turn on your integrator at this point and then do some timing, if you are using a DVM to watch the O2 it can only update a couple times a second and even though the datastream is pretty poor on the 747 it can show you better trends than the DVM, keep in mind the datastream has nothing to do with the CPU update ability. my $.02
-Carl

 

Thanks guys,
Well I am only setting open loop to diagnose this motor. This is a buds car with mods similiar to mine.
It seems once it hits closed loop it acts up.
I believe in open loop the blm and int are locked at 128 but the O2 still gives a reading. But doesnt swing like it does in closed loop.
Here are some diacom files. check out the ones that are "90KARL"
http://bowtye8.tzo.com/hovmovies/diacom
Dennis

------------------
85 vette,383,miniram,ZF6,4.10's..best ET 11.66@1187.00 60' 1.62
w/100HP nirous 11.05@127
http://geocities.com/bowtie8

 

I do not understand why you have to set the closed loop enable temp in order to go into open loop???? The engine will go into open loop anytime you go wide open throttle. On the scan tool you will see that the "learn mode" is off and this means you are open loop. The standard ZrO2 oxygen sensor you are using is primarily designed as a switching sensor made to transition at 14.7 air/fuel ratio. It is completely normal for the sensor to rapidly switch from about 100 mV to 800 mV as you are in closed loop and the computer is correcting the A/F ratio. In Power enrichment mode(some refer to as WOT mode) The Air/Fuel ratio should ALWAYS be rich which means an O2 voltage from 800-950 mV. The most power will be made with an A/F ratio of around 12.7:1. Many people shoot for an O2 voltage of 850-900mV to get close to the desired 12.7:1. While the O2 output voltage is a function of MANY engine operating parameters when in the rich region, it can be used as a guide. The main point is that you do not go lean under full load and WOT. If your O2 readings fall below 450mV you are lean, if you get below 100mV you are getting very lean.

------------------
Dave Zelinka

 

Yelfvr, @ WOT the ecm does not go into open loop, it goes into "WOT mode". It still reads all the sensors and utilizes them (except the O2).

 

My recommendation is to tune the entire Fuel table with closed loop on, trying to get the BLM values to 128, as was designed. Then, your Open Loop values should be tweakable rather easily to get you your desired (richer/consistant) results.

IE, the Fuel Tables are designed to be 14.7:1 engine operation, thus relagating BLM to hang around 128 in the OEM engine combo... You could then use some calcs and change the Open Loop table to add x% to get your enrichened results. Tune while fully warmed-up and EGR on (or disconnected with EGR advance off), of course.

A different example with the same results: As an example of what I tried, I tuned a table for BLM's of 128 (with no EGR or EGR spark, not using them). I then added percentages of fuel to the VE #1 cells to get the enrichment I desired (ie 12-13:1 or add percentages if you like, to get used to it) Then, make the "warm engine" Open Loop AFR at 14.7 (ie, 80-90 deg C) (this way computer will just use the Cell data!) and turn CL temp to max, so you are always in OPen Loop, as was stated. You will end up with an Open Loop table that will be very good if you use a good scan tool and take the time to fill in the table with appropriate VE values. Then, monitor your O2 sensor to fix any blatant lean/rich areas as you drive/race. You will have to add quite a bit of spark advance to get max power from this setup, again requiring a scan tool and knock sensor and should actually make a couple of iterations in the process because of spark-change induced fuel requirement changes...

Have fun no matter which way you do it.

 

Thanks for all the input but I am having trouble diagnosing this car. Its a new 355,215 cam,AFR190 heads headers etc.
All warmed up the car just stumbles and vacum goes way up or low 8". I posted on thius a few weeks back and am still at it. I jsut want toconfirm more wiring is ok.
The open loop enable is only foe some idle diagnosing, no racin.
sorry for the misleading.
Here was my original post
https://www.thirdgen.org/messgboard/...ML/000326.html



------------------
85 vette,383,miniram,ZF6,4.10's..best ET 11.66@1187.00 60' 1.62
w/100HP nirous 11.05@127
http://geocities.com/bowtie8

 

yeah carl, thats what i meant , the open loop afr table that is, slip of the fingers

 

Ok made some good progress today. Like I said I set closed loop enable to 200 .Well car stayed in open loop and idle great map at 50kpa. idle at 750 then I burned another chip to 700. everything great.
The o2 was swinging in the 500mv rng.
I burned a chip with all the same but closed loop enable to 170 and bad news again.
Then cyclinder is firing. I unplugged the injector and pull the wire all is fine there.. The header are hooker emission type the O2 6 inched down on the primary. wit full exhaust and a cat.
What else enables with closed loop. or what else does the ecm look at for closed loop.
All diaocm readings seem right on in open loop.
here is the latest diacom
http://bowtye8.tzo.com/hovmovies/diacom
the file is karlt5.gdf
I guess my plan is another o2. I have a heated one to try.
When I did unplug the injector for that cyclinder the o2 went to 100mv. plugged bak in and all O2 reading again.
In the program I have inj set to 25. They are bosch 24lb factory 85 cleaned and checked by LPE.
press set to 42.
The car is holding fuel press when shut off.
if the heated o2 dosnt work out the maybe I will try a O2 in the collector. This is what I have on my 85 . I am running a heated O2 though.
Dennis

------------------
85 vette,383,miniram,ZF6,4.10's..best ET 11.66@1187.00 60' 1.62
w/100HP nirous 11.05@127
http://geocities.com/bowtie8

 

It is tough to diagnose over the net. I have had O2 readings look fine on a scanner and have had replacement of O2 absolutely help. If the O2 swing is incorrect, all hell breaks loose in the ecm. Let us know.
-Carl

 

If there has been some engine work done, sounds like some silicone has started killing the O2. Leave it Open Loop, get it running good, and put 200-300 miles on it to purge all the sili out of the system. Yes, it can take that long to clean it out of the system. If a local yard will sell you some used ones, use them for a while after the 200 even. Had one car it took a total of almost a thousand miles to clean the system up. BTW, after getting some crap in the system it can take a couple minutes or 4 weeks to kill an O2

 

Grumpy
Explain,
You mean blue RTV on the intake ports/intake ends will/can kill a O2????
I did swap in a second o2 already. Actaul sislicone particles or fumes?

In the 90 progrmaming I can turn off teh open closed loop enable. but his original ECM is the 85. I just installed my ECM to get some diacom to find this all out.
In gmepro I really didnt see a open loop enabel temp or time enable.
Thanks
Dennis


------------------
85 vette,383,miniram,ZF6,4.10's..best ET 11.66@1187.00 60' 1.62
w/100HP nirous 11.05@127
http://geocities.com/bowtie8

 

Yep, Blue kills!!! Only use Permatex Ultra Black for all engine stuff...

 

Hey Bowtie...have you tried moving the O2 sensor into the collector? O2 sensor might be seeing pulses in the stream, trying to compensate is causing probs. Hth's
-Carl

 

Carl,
Yep thats the plan. I installed a new heated O2 and it was intermitent. somtimed good then other go right to 1050 mv. then the car just went bad. I gave the car back . He is gettign custum exhaust with a heated O2 in the collector I belive this will do the trick. IF that all works out he wnat to convert to the 7730 ecm. So it will be back in my hands. Thanks for everybodys help. I was pullin my hair for a few days there.
Dennis

------------------
85 vette,383,miniram,ZF6,4.10's..best ET 11.66@1187.00 60' 1.62
w/100HP nirous 11.05@127
http://geocities.com/bowtie8