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COBB Releases New v220 OTS MAPs - Major Update
- Thread starter BoostBumps
- Start date
I'm just trying to figure out if there is an actual danger or if this is a byproduct of them turning up then wick in terms of advancing the timing like crazy. On v.201 I would get knock sometimes at weird throttle openings in 5th and 6th if I was on boost but only 2/3 throttle. Now it seems to be more prevalent and I just can't imagine COBB would be OK with that. I run 93 octane and NGK one step colder plugs with only 1.5k miles on them.
I just put the new tune in my car (stg1 93oct). The car does feel a lot stronger. Did a couple pulls, monitoring AFR, OAR, Cyl 1-4 Ign Corr, and 1-4 Cyl Knock. After driving around a bit to get -1 OAR, AFR never got below 11.7, Cyl 1-4 Corr got +6, and 0 Knocks on Cyls 1-4. The car now feels like it leaps, when you punch the gas. Before there was slight lag, like something was holding it back.
I'm noticing the same thing. But with a twist.
Running stage 1 93oct, under low throttle and low load but higher gears (think 1/4-1/3 throttle in 4th gear or higher) Cyl 1 Knock is showing 2-3 per pull, but on the other hand, full throttle in lower gears yields no knock. I've also noticed timing is advanced quicker, at lower rpms, particularly in higher gears. Oddly enough, knock count shows knocks, but no negative timing corrections are shown.
I'm thinking of stepping down to a 91oct just to be safe, or sourcing a different gas station to top off on.
Running stage 1 93oct, under low throttle and low load but higher gears (think 1/4-1/3 throttle in 4th gear or higher) Cyl 1 Knock is showing 2-3 per pull, but on the other hand, full throttle in lower gears yields no knock. I've also noticed timing is advanced quicker, at lower rpms, particularly in higher gears. Oddly enough, knock count shows knocks, but no negative timing corrections are shown.
I'm thinking of stepping down to a 91oct just to be safe, or sourcing a different gas station to top off on.
I'm going to call Cobb tomorrow morning. I would be willing to bet that this is the result of changes in the way the new maps advance timing earlier as opposed to the way v201 advanced it at higher rpms. I'll comment with their response.
I'll reflash to the 91 octane map this afternoon and see if I get the same results.
I'll reflash to the 91 octane map this afternoon and see if I get the same results.
Has anybody actually compared the new maps to the old or taken any datalogs yet? It sounds like everyone is just taking random guesses, and there doesn't appear to actually be any solid information to discuss. How are you guys making the determination that timing is advanced more in the earlier rpm's than before, are you monitoring cylinder timing? What load are you guys using for discussion? What are the parameters that need to be met in order to duplicate the problem?
OAR isn't going to change unless you're meeting the criteria for it to change, and it doesn't sound like there is any actual 'problem' to cause that. It also doesn't correct timing in lower loads, but without any actual data to discuss we can't determine how much of an effect it's having. It's tough to discuss whether it has an effect or whether any of these 'problems' are actual problems without data.
OAR isn't going to change unless you're meeting the criteria for it to change, and it doesn't sound like there is any actual 'problem' to cause that. It also doesn't correct timing in lower loads, but without any actual data to discuss we can't determine how much of an effect it's having. It's tough to discuss whether it has an effect or whether any of these 'problems' are actual problems without data.
Many of you have noticed while logging your cars, that you see instances of high knock-correction values and low-rpm and low load situations. There has been much speculation about the cause and effects of these occurrences.
To put your apprehension to rest, Tim Bailey, one of our most experienced and knowledgeable tuners has offered the following explanation of this phenomenon:
Modern engine control computers (ECU) monitor and constantly adjust engine parameters including fuel delivery, variable camshaft timing, and ignition timing. Under light load (low boost or vacuum conditions) the objective of this active adjustment is optimized fuel economy and power.
An important component of this active adjustment is changes to ignition timing. Utilizing the highest possible ignition timing is a simple way to enhance the mechanical energy for any given combustion cycle. This enhancement extracts the most torque for a given quantity of spent fuel.
The processes that manage optimal ignition timing at light load are complex and vary by vehicle type. Some ignition timing adjustments are active and based upon sensor feedback. One such sensor is the "knock sensor." This sensor is a simple microphone that listens for engine noise. Complex signal processing inside the ECU helps discriminate detonation from other types of engine noise. The thresholds for noise vs knock vary not only by engine speed but by engine load. The ECU will react to engine noise by actively removing ignition timing. This low-load "knock correction" is a normal and desirable process that promotes optimal ignition timing.
Other timing adjustments are programmed compensations that are predictive in nature. For example, on some vehicles a sharp increase in throttle position predicts a fast change in engine load. In preparation for a predicted change in engine load the ECU will preemptively remove some ignition timing. This compensation is not really knock correction at all but is instead a predictive ignition timing adjustment. Similar compensations exist for a variety of conditions including but not limited to changes in load, air temperature, boost temperature, and acceleration. Tuning strategies for predictive corrections vary by vehicle but are present in some form in every modern ECU.
Unfortunately, the monitors that allow us to monitor the ECU’s activities do not discriminate between predictive timing adjustments and those responding to sensor input. However, regardless of the type of compensatory timing adjustment, at LIGHT load, these corrections are a normal means with which to optimize power and fuel economy. Under light load there is simply not enough cylinder pressure to allow engine damage. As a result, light load "knock correction" is not something to worry about. This is a normal process that is even more apparent when utilizing stock calibrations designed to utilize a range of fuel quality.
Travis Geny
COBB Tuning
I came upon this post when I searched "engine knock at low load and rpm". Came from an Evo forum, concerning what seems to be the same issue.
To put your apprehension to rest, Tim Bailey, one of our most experienced and knowledgeable tuners has offered the following explanation of this phenomenon:
Modern engine control computers (ECU) monitor and constantly adjust engine parameters including fuel delivery, variable camshaft timing, and ignition timing. Under light load (low boost or vacuum conditions) the objective of this active adjustment is optimized fuel economy and power.
An important component of this active adjustment is changes to ignition timing. Utilizing the highest possible ignition timing is a simple way to enhance the mechanical energy for any given combustion cycle. This enhancement extracts the most torque for a given quantity of spent fuel.
The processes that manage optimal ignition timing at light load are complex and vary by vehicle type. Some ignition timing adjustments are active and based upon sensor feedback. One such sensor is the "knock sensor." This sensor is a simple microphone that listens for engine noise. Complex signal processing inside the ECU helps discriminate detonation from other types of engine noise. The thresholds for noise vs knock vary not only by engine speed but by engine load. The ECU will react to engine noise by actively removing ignition timing. This low-load "knock correction" is a normal and desirable process that promotes optimal ignition timing.
Other timing adjustments are programmed compensations that are predictive in nature. For example, on some vehicles a sharp increase in throttle position predicts a fast change in engine load. In preparation for a predicted change in engine load the ECU will preemptively remove some ignition timing. This compensation is not really knock correction at all but is instead a predictive ignition timing adjustment. Similar compensations exist for a variety of conditions including but not limited to changes in load, air temperature, boost temperature, and acceleration. Tuning strategies for predictive corrections vary by vehicle but are present in some form in every modern ECU.
Unfortunately, the monitors that allow us to monitor the ECU’s activities do not discriminate between predictive timing adjustments and those responding to sensor input. However, regardless of the type of compensatory timing adjustment, at LIGHT load, these corrections are a normal means with which to optimize power and fuel economy. Under light load there is simply not enough cylinder pressure to allow engine damage. As a result, light load "knock correction" is not something to worry about. This is a normal process that is even more apparent when utilizing stock calibrations designed to utilize a range of fuel quality.
Travis Geny
COBB Tuning
I came upon this post when I searched "engine knock at low load and rpm". Came from an Evo forum, concerning what seems to be the same issue.
This is exactly why I keep bringing up datalogging. Without knowing exactly when and under what circumstances problems are occurring, you can't actually tell whether something is actually a problem. This isn't much different than the people that were convinced that the 91 octane tune was so much more responsive than the 93 octane tune, when the only actual difference between the two was a couple degrees of timing in the high-load/high-rpm areas of the map.
That's really good information.
As for more Ignition Advance earlier, in my case, in 4th gear or higher at 1/2 throttle or better, in earlier maps, I would routinely see 2.5-3 degrees of advance under 4k rpm, on the same roads, with the v220 update, I'm seeing 4.5-5.5 degrees under the exact same conditions. And before, the only time I would ever see 6 degrees was WOT in 3rd or 4th gear when I let it spin all the way up to 5k rpm or greater, as I usually only do going up an interstate on ramp. Now I see 6 degrees at WOT but even if I shift out at 4-4.5k rpm.
As to the knock, I did a few pulls this afternoon on dry roads (first we've had in about a week) and got no knock at any load, gear, or rpm. Maybe in my case knock sensors picked up small surges from the slippery road at the right frequency to interpret them as knock. Pure speculation of course.
That reminds me, do we have the ability to measure EGTs with the Accessport? A spike in EGTs along with a knock count could go along way to clearing up false knock issues we see people report (like when everyone was worrying about the RMM causing false knock)
As for more Ignition Advance earlier, in my case, in 4th gear or higher at 1/2 throttle or better, in earlier maps, I would routinely see 2.5-3 degrees of advance under 4k rpm, on the same roads, with the v220 update, I'm seeing 4.5-5.5 degrees under the exact same conditions. And before, the only time I would ever see 6 degrees was WOT in 3rd or 4th gear when I let it spin all the way up to 5k rpm or greater, as I usually only do going up an interstate on ramp. Now I see 6 degrees at WOT but even if I shift out at 4-4.5k rpm.
As to the knock, I did a few pulls this afternoon on dry roads (first we've had in about a week) and got no knock at any load, gear, or rpm. Maybe in my case knock sensors picked up small surges from the slippery road at the right frequency to interpret them as knock. Pure speculation of course.
That reminds me, do we have the ability to measure EGTs with the Accessport? A spike in EGTs along with a knock count could go along way to clearing up false knock issues we see people report (like when everyone was worrying about the RMM causing false knock)
I can induce full knock-sensor advance at 2k rpm and below, so long as I meet and hold certain conditions, and see at or less than 3 in WOT. And that's only KS advance, which is only one single addition to the base borderline tables, and not a good indication of overall timing advance. In short, it's not a good performance indicator for the discussion.
As for EGT, what we can monitor is inferred. It's in the monitor list.
As for EGT, what we can monitor is inferred. It's in the monitor list.
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