Help! failed smog AGAIN

[Schrade]

... and that makes a big difference vs. stock when it comes to this kind of troubleshooting! ...

I say this EVERY thread.

My nOX levels were very low on both test. If memory serves me, that indicates low combustion temps, does it not?

Yup.


But this throws me:

Done intentionally so I would not have to mix gas (av gas +pump gas) or retard the timing or flatten out the advance curve to prevent knocking.

A gas drenched, cooled-fired mix won't knock against spark (spark knock) detonate early, without getting REAL HOT (and showing up as HIGH oxides of Nitrogen, like you don't have).

Coolant temp tells little of ignition in 1 or 2 cylinders. Even 3 could be fouled and coolant system will keep temps close to spec.

 

[navy2kcoupe]

I'm gonna TRY not to become obsessed with #7....it just bugs me!

Would it be possible to have the splits in all 3 rings lined up on that #7 cyl?
That happened to a buddy of mine "way back in the day" (like 1968). I believe that the ring installation instructions tell you to have 120 degrees between each ring split. Just thinkin' out loud.......
Andy

 

[boomdriver]

Andy,
I suppose thats possible, but it would have to happen on its own, cause it was "right" when assembled..

I'll plan on pulling the rails and checking injectors. That one could have a damaged nozzel "that just sprays too much fuel or poor atomization. Going to look at valve seal condition as well.
There are a couple other things to do before I get to that point...

Schrade
this.........

".........Done intentionally so I would not have to mix gas (av gas +pump gas) or retard the timing or flatten out the advance curve to prevent knocking...."

Was in reference to the compression ratio when the motor was being built. I did not want to go too high because in Ca there is'nt pump gas higher than 91 and that will go away as they lower the max legal octane levels for the general public. An 11:1 in perfect tune might run on that, but I did not want to risk it, so I intentionally kept the compression down under 11 to give my tuning "window" a little larger opening to work with. The higher the compression the more exact everything else has to be. And I was unable to get forged pistons and crank, I did'nt want to risk it. So, most of the upgrades were in the top end and I just balanced the bottom end for longevity.
Its a street car and there was also the Ca smog to consider. I just did'nt want the hassles of a hi compression motor living on cheap gas.

 

[geekinavette]

A tad off the topic, but since you bring it up (and just out of curiosity) what is the Dynamic Compression Ratio? (much more important than Static)

 

[c4c5specialist]

HI there,

I am still of the mindset, replace the 02 sensor and replace the catalyst and you will be just fine.

Walker makes an OEM replacement for under $200

Allthebest, c4c5

 

[boomdriver]

Thats a good question....:confused
Since making some physical changes to the engines displacement/volume, the stock numbers are useless. I know that the calculated or static ratio is just over 10:1. Assuming that the stock figure of 8.5:1 is correct, that fits with the larger bore, and increased intake effiency. But, thats just a number since its not "real" unless the throttle is WFO and the volume is 100% of the displacement.

I should know that answer....but my calculator-lazy brain barely got thru figuring the atmospheric pressures x displacement...to arrive at some PSI figures.

The dynamic ratio would be effected by cam timing (way outta my league) and other factors.
All dynamic amounts to, is the TRUE accounting of actual compression, not calculated volumetric equasions. The figures for volume get reduced by open valves, and crankshaft rotation, so dynamic ratio will be lots lower than the static/calculated CR everytime. From what I understand, even cam or valve over-lap at certain RPMs changes the dynamic ratio.

Wish I were smart enough to answer your question!
Heck...I wish I were smart enough to drive my calculator and have IT give an answer !:L

 

[boomdriver]

HI there,

I am still of the mindset, replace the 02 sensor and replace the catalyst and you will be just fine.

Walker makes an OEM replacement for under $200

Allthebest, c4c5

c4c5,

I am inclined to agree.

I went back and tried to document some figures from the o2 sensor today but,

it was shooting wild signals from 100mv to1000 when it was stone cold.
It did not really get better as it got hot, although the range of output did seem to rise a bit. The Voltage was still flopping around like a fish before the eng temp hit 150 degrees. It was never stable or operating in one area. It jumped everywhere from the beginning to end. The new sensor WILL get installed.

I also traded plugs in the #7 hole yesterday and was able to put some miles on it. Now the old dark plug is burned clean living in the #5 hole, and the white clean plug that I put in #7 is still an acceptable shade of white.
I did notice a definate change in the engine tone (more like a muffled mis?)after a couple start ups and it makes me wonder if there is some trash in the fuel rails that gets pushed into injectors but too large to pass thru...trash floating around that is trapped there.This evasive sound will vanish and re-appear whenever it wants.
I dunno. I am positive that I will be pulling the rails off to properly clean and inspect, and maybe some FIC top shelf injectors might be laying around at that time.

 

[c4c5specialist]

uHi there,

When its cold, that means that the sensor is doing something wrong.

Like I said, you have the movement, but I bet once you put in the new sensor, alot will change. It will take up to 2-4 minutes, depending on ambient temperature to correctly start to react with the oxygen content.

Take it step by step, replace the sensor and really do not be fixed on the #7, because the truth is anything can cause what your dealing with. The sparkplug might not be radiating heat correctly.

Allthebest, c4c5

 

[geekinavette]

Boom...

Wallace Racing: Dynamic Compression Ratio Calculator

Its accurate, I just used it after doing a cam swap myself...cranking pressure was right on the money.

Now, go change that O2 sensor!

 

[boomdriver]

lol...
well, i DID try to change the sensor, but its in there so tight that my sensor socket twisted halfway around the thing and stuck.....oooops.

I'll take it to a shop tomorrow and get them to change it and do a couple other things while its on the lift.

c4c5,
I'm not worried about that one cyl...I'm satisfied that there is nothing wrong mechanically and all that it can be is poor injector spray. Even that will come & go. I think there is some trash floating around in the fuel rails or something thats already lodged in the injector screen. Am disassembling soon to inspect and clean.

 

[Schrade]

Thats a good question....:confused
Since making some physical changes to the engines displacement/volume, the stock numbers are useless. I know that the calculated or static ratio is just over 10:1. Assuming that the stock figure of 8.5:1 is correct, that fits with the larger bore, and increased intake effiency. But, thats just a number since its not "real" unless the throttle is WFO and the volume is 100% of the displacement.

I should know that answer....but my calculator-lazy brain barely got thru figuring the atmospheric pressures x displacement...to arrive at some PSI figures.

The dynamic ratio would be effected by cam timing (way outta my league) and other factors.
All dynamic amounts to, is the TRUE accounting of actual compression, not calculated volumetric equasions. The figures for volume get reduced by open valves, and crankshaft rotation, so dynamic ratio will be lots lower than the static/calculated CR everytime. From what I understand, even cam or valve over-lap at certain RPMs changes the dynamic ratio.

Wish I were smart enough to answer your question!
Heck...I wish I were smart enough to drive my calculator and have IT give an answer !:L

Static = NOT in motion. Dynamic = in motion. Fuel pressure, timing, compression, tire balancing, etc.

Static compression is squeeze gauge in the hole, turn the crank with a breaker bar to 0 on the timer mark, and observe gauge. You might get some indication of leakdown too. Then go to #8 hole, turn the crank to 90 on the timer mark. Then #4 = 180, #3 = 270, #6 = 0, etc.

Dynamic is with crank in motion. I did a carbed motor while running. For FI motors, maybe pull the fire from all cylinders, and just turn by starter power for this read.

Engine assembly lube, or gear oil, around valve stems, during static test will show valve seating efficiency (bubbles). Some say putting a few drops of oil in cylinder will show ring condition, but the cylinder is not sitting horizontal, so I'm less a believer in ring/squeeze test...

 

[TedC]

Boom, Can't you soak the treads with penetrating solvent, cut the o2 wire, and use a 6 point deep socket to remove? I had similar problems on my 1988. Felt like it was welded on. Used the same procedure on my 1989, and it turned right away. Had no plans in saving the old o2 sensor, so I just used the o2 socket during the install process.

 

[boomdriver]

Ted,
yeah, been soaking the thing with penetrant and am more than willing to sacrifice the old sensor in the name of Texas smog laws:eyerole, but the big problem is finding an angle to get a decent amount of turn from a wrench or cheater. This thing is screwed into an aftermarket Y pipe and the sensor is kinda angled right toward the oil cooler and its hoses...so from above there is only MAYBE 1/8 turn available and from below its only gonna be maybe 1/2...but it has to be 2ft off the ground to have a chance.

I'll just give it to a little shop that I know around the corner and get them to swap my power steering hoses as well. I darn sure don;t want to do those!

Smog....episode 422

for those following the drama, no progress today. Too busy with other things....The vette just gets most of my time and attention, as it should. After all, it is a relationship..

I even FOUND the elusive ABS sensor for my rear wheel....and got it at a good (real good actually) price. That'll be here next week. The one that I thought I had coming turned out to be damaged so they did'nt send it.

So, hopefully that o2 sensor will get changed somehow this weekend, and maybe I'll seek another retest if things seem like they;re in order. Worst case, I'll get the viper guy to build me a nice new cat with flanges....

 

[boomdriver]

Geek,
Thanks for that link!
I'll have to find half that info they ask for, but when I do that'll be a real useful tool to have !

 

[boomdriver]

Late Update..

Problem solved. I just noticed that I never posted the end result of the failed smog issues...

Rotted wire in the left side fuel injector harness was causing injectors to get poor signals and/or broken signals that caused rich conditions. The ECM appearantly tried to compensate which resulted in even more confusion. Semi dead cylinders, random plug fouling...very mysterous.

New wire soldered in the harness, new injector plugs soldered in,. everything is perfect.; There remains one wire issue with the oil pressure sender circuit that is definately wire harness related, but it is inaccessable for now.
There were no signs of wire rot on the other injector bank or harness.

 

[G Winter]

Reading some of this thread I noticed you added alcohol to the gas. I think you do this to reduce HC ? which makes sence. It also was stated that it burns hotter. I am not so sure that this is true when you put in a high percentage. I have always though alcohol burn cooler. Some one clear my up on this.

Glenn

 

[boomdriver]

Reading some of this thread I noticed you added alcohol to the gas. I think you do this to reduce HC ? which makes sence. It also was stated that it burns hotter. I am not so sure that this is true when you put in a high percentage. I have always though alcohol burn cooler. Some one clear my up on this.

Glenn

I think "hotter" was a poor choice of words...To say, it burns "cleaner" would be more accurate. Yes, the alcohol was added to try to get the HC numbers down. Less gasoline and more alcohol. Bad for rubber but great for the smog nazi.
AT the time I had no idea that the real problem was the fuel injection being completely randomly screwed up due to the rotted wire. Shorts, signals from one wire effecting another, half signals, weak signals, I found a fouled plug in #7 on day, and a week later that cyl would be clean and the fouling would be in #3...Very difficult to track down. The only thing in common was that the physical clues always came from the left bank. All from wire rot.

The alcohol did lower the HC with the wire issues still present but it was not nearly enough to pass. As soon as the wiring was repaired it was a very dramatic difference in the numbers as well as performance.