93 LT1, 6 spd, hot cam, Trick Flow 185 heads, EM LT headers. Since I rebuilt my motor this winter have had cam surge. The tuner has almost tuned it out, but it's still there below 1800 rpm.
Here is my question, since the purpose of two o2 sensors is for emissions and the cats (using two instead of just one). Why not just use one o2 sensor and split the computer wire (I have heated o2's now) so the computer still thinks there are two but really there is only one.
As I understand it the problem with cam surge in a fuel injected car is the split BLM's. The computer can't react fast enough to the o2 readings because they are jumping all over the place from the cam overlap at lower engine speeds. I can see in my data log's the split BLM's and o2 readings all over the place at lower engine speeds. My car is speed density too, don't know if that is better or not.
I also notice that my 02's are right in the header collector. When I look in the collector at the o2 I can see it can really only get exhaust readings from the two top pipes of the headers, the lower two are so far below the o2 that no wonder the readings are all over the place.
I decided to move the both sensors back to the exhaust pipe about 12" after the collector merges, hopefully this will smooth out the readings it gets in the exhaust.
Any thoughts/ comments are greatly appreciated from those of you who have experience with this, being the perfectionist I am, I want this to go away as much as possible.
How is so difficult to post pix???? Anyway copy and past this address for pix;
1.http://s1113.photobucket.com/albums/...t=IMG_4534.jpg
2.http://s1113.photobucket.com/albums/...t=IMG_4535.jpg

 

O2 readings always jump all over the place...down to around 0.2mV and up to around 0.9mV. This is perfectly normal. You are trying to "fix" an issue that isn't there.

Split BLMs are not the reason for cam surge, not to mention they typically only happen at idle due to reversion in the intake manifold. Nonetheless, a split of 5% or so isn't unusual even on factory stock engines and programming. If you have significant split BLMs while driving, you may have a vacuum or exhaust leak.

Cam surge is a result of duration. If you want to get rid of it, you need to run open loop all the time and fix the VE tables and the timing.

What are your cam spec?

 

.......... In reality, the hot cam isn't all that hot ..... 218 / 228 ........ have your tuner level out the spark advance tables around your idle rpm / load range and things should improve for you ...... also try to set the IAC counts ( minimum idle ) to around 35-40 in neutral ..... double check the TPS settings as well ........

 

I missed the mention of the hot cam by the OP :o I'd also have the tuner take a look at the VE tables in the area where you are having cam surge. Probably need to lower VE a tad more.

 

I'm running a larger cam 224/230 605/622 112, and have 0 cam surge even at 1100 rpms. It's all in the tune. My car is a MAF car, but even with speed density it can be done.

 

Leave the 02s right where they are also. They are ideal

 

He did take out timing, helped a bunch, timing was going up to 50 at lower speeds, now it's around 34 - 36.
How do I set the IAC counts? I have checked the TPS it's right on the money .56 volts.

 

hot cam 218 / 228 duration .525 lift on both intake and exhaust.

 

Did you do your own tune or have someone else do it, if so do you mind saying who? Did you have any cam surge ever? Did the tuner take several tries to get rid of it?

 

Last LT4 hotcam package I spent time in had low speed surge.
The tuner had leaned it out a lot perhaps "on the line".

 

What do you mean "tuner had leaned it out a lot perhaps "on the line?

 

This is in the manual for my wideband o2 sensor. It seems to be saying that too much data simply makes the 02 sensor too hard to read. That is the same reason I moved the stock 02 sensors out of the collector where it will obviously get skewed readings from the two top header tubes and very little reading from the lower two, to further back in the exhaust where the whole exhaust charge is much more blended, make sense?

"The second parameter determining the logging speed is the statistical nature of the combustion process itself. No two combustion events in an engine are identical. Therefore, to get meaningful data, multiple combustion events must be averaged to see the overall effects. If each combustion event is analyzed and recorded, meaningful tuning data can’t be seen in most cases. At 6000 RPM an engine goes through 50 engine cycles per second (a 4-stroke engine cycle requires two rotations per cycle). At a logging speed of 12.5 samples per second this would mean that the resulting data is the average of 4 engine cycles.
The above means that data logging engine data needs to be done at 10-15 samples per second. Anything more creates only more data points which do not contain any additional information, but are harder to analyze."

 

I do my own tuning, and it did take several runs to get it right.

 

............ Set the IAC counts by turning the throttle blade stop screw while watching IAC on your scanner .......... Or , by setting the minimum idle speed per the directions in the factory service manual .... any adjustments made here will affect TPS so recheck it when you're done with min idle ...........
........... Its not so much as taking timing out as it is to level it or equalize it in all the idle rpm and load ranges ... ie ... the advance should be the same number all around your idle speed zone ... mine is currently at 26 degrees from 400-1200rpm from 32-96Lv8 ........ but I have a LOT more cam than yours .......

 

Here is one of timing tables, it seems like a lot of advance, what do you think? Do you mean by "It's not so much as taking timing out as it is to level it our equalize it in all the idle rpm and load ranges" that it should be 26 at all Kpa ranges say at 900 rpm? Thanks
http://s1113.photobucket.com/albums/...t=IMG_4512.jpg
http://s1113.photobucket.com/albums/...t=IMG_4511.jpg

 

................ What kpa and rpm are you idling at ? in gear and also in neutral ?... my car is MAF so the load Lv8 is calculated by the ecm ...... What you want is the same advance number in your idling kpa range ... lets just say you idle at 30-50 kpa and all potential idle speeds from 400 to at least 800 rpm should be at the same number ... lets say 36 ... yours currently vary by 6-8 degrees from 32 to 40 ... that much change in advance will contribute to surge as the IAC tries to control the idle speed .... what is your commanded idle speed ? .......... Do you have a scanner ? .........

 

Kpa at idle is 45-50, 850rpm

How do I find the "commanded idle speed"?

No, I don't have a scanner

Thanks for the reply

 

the commanded idle speed will be found under these 2 tables:
"Target Idle RPM Vs Coolant Temp(In Drive)"
"Target Idle RPM Vs Coolant Temp (In P/N)"