..... On five consecutive eighth mile passes at the local drag strip with NO changes to the car , and , after having made some adjusted runs ... pass #1 and #4 went pretty rich AE off the line ... 10.44 AFR on #1 ... 11.8 #2 ... 11.22 #3 ... 10.88 #4 ... 11.67 #5 ............ On pass #1 the car hesitated to the tune of a .225 reaction time and on pass #4 a little hiccup with a resulting .112 reaction time ... all the other reaction times for the night were in the .030 range

My question is this : What is affecting the AE that I'm overlooking here ? There are only two variables that I can think of ... one being where the BLM is when I mash the go pedal ... the other being the PW correction vs battery voltage table ? On #2 here , I run the engine cooling fan and turn on the parking lights for EVERY pass to keep voltages consistent , but they do drop slightly the longer it takes for everyone to get staged because of the brake lights ... voltage will dip to 12.3 on the line ... A possible third is the ACTUAL idle speed at the time of pedal mashing ?? Any ideas ???

 

Once triggered by the delta tps%, the AE pulse size is primarily dependent upon (delta LV8 - 20) * the delta LV8 factor from the table. 20 is the min delta LV8 for AE and this value is subracted off from delta LV8 before the pulse is calculated.

Assuming that your MAF flow, rpm and throttle opening are all consistent, delta LV8 value itself shouldn't vary too much. Wheel spin will tend to reduce the LV8 and delta LV8 values, since the rpm may be rising faster than the airflow.

I suspect that the richer runs were made in open loop, where the AFR target may be richer due to the LV8 influence.

For consistency, you may want to zero the open loop % change vs LV8, and also zero the open loop % change vs coolant temp (for warm coolant temps) to eliminate this as a source of error. This will keep your target AFR consistent between open and closed loop including PE.

For delta LV8, only way to be sure what its doing is to add it to the data stream and log data during your runs.

You might also want to avoid abrupt changes in the AE vs delta lv8 table to keep the gain consistent vs delta LV8, or you could reduce the gain for the larger delta LV8 values, to reduce the gain in order to have a more consitent pulse.

Gotta datalog and observe all the relevant signals to really determine what is going on.

 

Note: The (delta LV8 - 20) signal is pretty close to what you would see by just stepping through the datalog and observing the LV8 signal from sample to sample.

Just subtract the old LV8 value from the new value and then subtract 20. This will give you a good idea of the delta LV8 - 20, and from that you can determine which gain value is being used from the table to calculate the pulses.

 

..... Thanks for the reply ... my open loop vs coolant temp settings are all zeroed from 68* C to 116* C ... open loop vs load are all zeroed from 0 to 80 ..... should I zero them all ? From 192 to 256 they are all set at 16.80 ...

..... The AE vs delta Lv8 table is at 0.22 for 256 , 0.20 for 192 , 0.16 for 128 , and 0.12 for 64 & 0

..... the hot engine O2 timer is set at 66 secs ... I have a heated O2S ... I'm certain that the car enters closed loop before I get into the bleach box and it definitely is before staging ... I try not to be first in line for that very reason ...

..... I have also leveled the SA vs rpm vs load at all points up to 1200 rpm and 96 load at 26*

..... The same leveling on the BPW vs load ... ALL are leveled under 1200 rpm ..... Idle rpm is at 800 .........

..... I will do some data logging and look more closely at Lv8 values ... I might have to duct tape the laptop to the passenger seat ... lol ...

..... Thanks again for your input ........... Bob ..........

 

..... Made some passes on Weds and noticed that the Lv8 drops a lot when I mash the go pedal ... At first , rpm drops from 800ish to 700 with load indicated as 255 ... on the next sample RPM is 900 with load down to 162 ? ... the load gradually increases to 208 at around 2700 rpm ... this is where the road speed indicates 1 mph ... ( 2500 rpm stall converter ) ... All the while the AFGS is climbing along with the rpm ..... The AE came in anywhere from 1400 to 2100 rpm and varied in intensity ... I altered some of the AE tables and got it to stay closer to 11.00 but I want it in earlier and more consistently to improve my 60 foot times ... the best on Weds was a 1.79 and the car has pulled 1.70's from time to time , so I know its got it in itself ........

..... The BIG question is : What is affecting my initial acceleration ? There is no spark retard , but the spark follows the changes in Lv8 and RPM ... The commanded AFR changes ... also following changes in Lv8 and RPM ... AND , the load changes ... perhaps following changes to AFR ... Chicken and egg ... which one is the culprit ??? And where to adjust to smooth things out ???

 

Question: How do you know its in AE between 1400 and 2100 rpm? Did you add AE info into the datastream? Normally this info is not available.

From what you've described, I would expect AE to begin when you mash the gas as the LV8 goes from 80-100 (whatever) to 255. Delta LV8 would be approx. 160. Which would use something between 0.20 or 0.16 from your delta LV8 table.

From this point, you should get 12 AE pulses...

After this first AE event, with only a gradual rise in LV8, the delta LV8 is expected to be very small, so I wouldn't expect much AE if any at all after the first event.

For the LV8 to drop from 255 to 162 between 800 and 900 rpm, the MAF flow must also be dropping significantly.

~42.5 gm/sec at 800 rpm should be LV8 of 255.

~30 gm/sec at 900 rpm should be LV8 of 162.

I would look at the MAF signal and perhaps max maf flow vs rpm table for an explanation.

I think your fueling variation is due to MAF flow variation and/or variability in your PE target AFR vs rpm table.

The commanded AFR at WOT should be the PE target if in closed loop already. This will vary only by coolant temp and rpm. Your PE target AFR vs rpm settings may have too much variability with respect to rpm in the vicinity of your launch rpm.

 

Just a thought, is the load changing due to tire spin ? If the car spins more or less on a pass I think maybe it would show up as a load variation.

 

Mph doesn't show up on the datalog til the converter locks around 2700 rpm ... so I'm figuring no wheel spin ... none detectable by me either ... by that time I'm well past the area where the Lv8 drops .......

I got it to calm down a bit by smoothing the WOT vs RPM tables ... commanded AFR was messing with the Lv8 ... the problem is that the BPW and Lv8 are dropping or rising in between the RPM's on the table ... ie @ 2200 rpm and at 2600 while the table values @ 2000 , 2400 , and 2800 are OK .......... Tuner Pro and $32B ...