when does ecm reduce power?
Thread Starter
Pro
Joined: Sep 2009
Posts: 536
Likes: 2
From: Los Angeles California
when does ecm reduce power?
Hi, my stock 2007 z-51 manual trans. seems to have "moods"... sometimes it has more power than others... I have heard there are various situations when the ecm will pull timing/reduce power. Does anyone have info on this,or know where documentation on this can be found?
Thanks
Thanks
Burning Brakes
Joined: Aug 2007
Posts: 769
Likes: 0
From: Cincinnati OH
I don't know of any real time that the car becomes consertive with its output.
However, things to consider are the grade of fuel. Lower octane will retard timing, intake air temp, ambient air temp, and things of that nature will all effect the driveability of the car.
I have never really noted what you are talking about. I know the ECM will learn how we drive and adjust slightly due to that. Some smarter than me should chime in on that subject.
Sometimes the cars are just faster than they feel. The car is built to handle what you can throw at it, its ability to respond so well, can distort what we feel in the seat of our pants.
Mike
However, things to consider are the grade of fuel. Lower octane will retard timing, intake air temp, ambient air temp, and things of that nature will all effect the driveability of the car.
I have never really noted what you are talking about. I know the ECM will learn how we drive and adjust slightly due to that. Some smarter than me should chime in on that subject.
Sometimes the cars are just faster than they feel. The car is built to handle what you can throw at it, its ability to respond so well, can distort what we feel in the seat of our pants.
Mike
Race Director
Joined: Jan 2005
Posts: 10,924
Likes: 854
From: Daytona Beach FL
One of the things that can create problems is if you have a tire pressure sensor go bad, or if they aren't properly registered with the TPMS computer in the car.
At my last track event, after swapping to my track wheels, apparently one of my sensors didn't get properly logged into the TPMS memory. I got a DIC message of "Right Front xx psi", and in a couple of corners when trying to get on the throttle hard the car pulled power (I pulled into the paddock area and did a relearn procedure again, and everything worked well after that). Drag racers have reported similar problems when trying to launch hard with low pressures (less than 24 psi will give a low pressure message in the DIC) in drag radials.
The TPMS is designed to protect you if it gets info of a flat tire, and it will pull power if it detects hard cornering or acceleration. Likewise, if it doesn't get any info from a sensor (a bad sensor, or no sensors installed or not registered) it will reduce power to keep you from losing control when driving aggressively on a flat tire.
Bob
At my last track event, after swapping to my track wheels, apparently one of my sensors didn't get properly logged into the TPMS memory. I got a DIC message of "Right Front xx psi", and in a couple of corners when trying to get on the throttle hard the car pulled power (I pulled into the paddock area and did a relearn procedure again, and everything worked well after that). Drag racers have reported similar problems when trying to launch hard with low pressures (less than 24 psi will give a low pressure message in the DIC) in drag radials.
The TPMS is designed to protect you if it gets info of a flat tire, and it will pull power if it detects hard cornering or acceleration. Likewise, if it doesn't get any info from a sensor (a bad sensor, or no sensors installed or not registered) it will reduce power to keep you from losing control when driving aggressively on a flat tire.
Bob
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
Ignition timing is retarded starting @ 86° intake air temp and 195° coolant temp.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
Instructor
Joined: Apr 2009
Posts: 145
Likes: 0
The ECM has engine torque management that engages when more than the set amount of torque is generated in a given gear at a given RPM. There is a table for each gear including reverse. There are also maximum settings for the transmission input shaft, output shaft, and axle shafts. Get near these numbers, and power will be pulled back.
Disable these tables, and you can melt a set of tires very fast.
Disable these tables, and you can melt a set of tires very fast.
Le Mans Master
Joined: Dec 2005
Posts: 7,753
Likes: 210
From: North Western Connecticut
Ignition timing is retarded starting @ 86° intake air temp and 195° coolant temp.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
How much power is lost (HP) in your best guesstimate when timing is retarded say 12 degs?
Race Director
Joined: Mar 2005
Posts: 10,399
Likes: 26
From: Austin Texas
Very very interesting! I've noticed a big difference in the power when my temp is at 180 versus say 200 degs! I changed the stat to 160 and the car pretty much runs at 180 degs unless I'm in traffic. It used to run pretty much at 195 to 200 degs with the old stat. It seems to make a HUGE difference in SOTP power but it's never been dynoed!
How much power is lost (HP) in your best guesstimate when timing is retarded say 12 degs?
How much power is lost (HP) in your best guesstimate when timing is retarded say 12 degs?
Try this link for timing corrections for coolant temp;
http://forums.corvetteforum.com/phot...a/1124/ect.jpg
Somebody must have a link for timing corrections for intake air temp, the ones I have are dead.
Last edited by haljensen; Sep 12, 2009 at 10:16 AM. Reason: correct links
Burning Brakes
Joined: Jun 2008
Posts: 1,096
Likes: 1
From: Chesapeake Va
My 05 is the same way. Some times when I'm getting on the freeway the thing runs like a raped ape all on its own. Other times I have to go down on the pedal and it acts like a car without all that power. Maybe it's the throttle sensor? I've heard these are not cable, but have a sensor that relates the throttle input to the engine. Maybe's its how the ecm interprets that input? Beats me, but if you ever figure it out, PLEASE let me know. I want all that power all the time, not just when it wants to lavish it out on an unexpecting driver.
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Safety Car
Joined: Nov 2007
Posts: 4,446
Likes: 878
From: Bay Area CA
Ignition timing is retarded starting @ 86° intake air temp and 195° coolant temp.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
Example : Coolant temp is 220 degrees, timing gets pull -3, at the same time IAT temp is 90 degrees, timing gets pulled -2 . Is total timing pulled -5 degreess collectively or -3 the greater of the two amounts ?
Safety Car
Joined: Nov 2007
Posts: 4,446
Likes: 878
From: Bay Area CA
Hi, my stock 2007 z-51 manual trans. seems to have "moods"... sometimes it has more power than others... I have heard there are various situations when the ecm will pull timing/reduce power. Does anyone have info on this,or know where documentation on this can be found?
Thanks
Thanks
Le Mans Master
Joined: Dec 2005
Posts: 7,753
Likes: 210
From: North Western Connecticut
Don't know if there is anyway of telling HP loss from timing retard. The only example I have was my '05. On the dyno one day the Knock Retard kicked in at around 4,000 RPM and I lost 25 RWHP. It was very obvious on the Dyno chart.
Try this link for timing corrections for coolant temp;
http://forums.corvetteforum.com/phot...a/1124/ect.jpg
Somebody must have a link for timing corrections for intake air temp, the ones I have are dead.
Try this link for timing corrections for coolant temp;
http://forums.corvetteforum.com/phot...a/1124/ect.jpg
Somebody must have a link for timing corrections for intake air temp, the ones I have are dead.
Thread Starter
Pro
Joined: Sep 2009
Posts: 536
Likes: 2
From: Los Angeles California
Ok, sounds like coolant temp and intake are temp are two reasons... Let me suggest another couple of things I have heard about or noticed...
first, I have heard some say the ecm "learns" how you drive and responds accordingly. Is this true? If so, on what time scale does it learn? In other words if you want a fast dragstrip time do you need to drive aggressively in the hours or days before your runs? If it has "learned" to be conservative, how long does it take to teach it otherwise?
Second, fuel octane. If the knock sensor is pulling timming, then does 100 octane prevent that from happening, and again, how long do you have to run the 100 before the positive changes take effect?
I went to the dragstrip twice recently. The first time, on 91 octane, the power seemed to increase with each run (trap speeds rose with each run). The car also seemed unusually quick on the way home... On the second trip to the dragstrip I ran 100 octane and the same thing happened, but trap speeds rose even higher, and on the way home the car seemed to have more power than ever...
thanks for any sharing any info or experiences you may have.
first, I have heard some say the ecm "learns" how you drive and responds accordingly. Is this true? If so, on what time scale does it learn? In other words if you want a fast dragstrip time do you need to drive aggressively in the hours or days before your runs? If it has "learned" to be conservative, how long does it take to teach it otherwise?
Second, fuel octane. If the knock sensor is pulling timming, then does 100 octane prevent that from happening, and again, how long do you have to run the 100 before the positive changes take effect?
I went to the dragstrip twice recently. The first time, on 91 octane, the power seemed to increase with each run (trap speeds rose with each run). The car also seemed unusually quick on the way home... On the second trip to the dragstrip I ran 100 octane and the same thing happened, but trap speeds rose even higher, and on the way home the car seemed to have more power than ever...
thanks for any sharing any info or experiences you may have.
Instructor
Joined: Apr 2009
Posts: 145
Likes: 0
Ok, sounds like coolant temp and intake are temp are two reasons... Let me suggest another couple of things I have heard about or noticed...
first, I have heard some say the ecm "learns" how you drive and responds accordingly. Is this true? If so, on what time scale does it learn? In other words if you want a fast dragstrip time do you need to drive aggressively in the hours or days before your runs? If it has "learned" to be conservative, how long does it take to teach it otherwise?
Second, fuel octane. If the knock sensor is pulling timming, then does 100 octane prevent that from happening, and again, how long do you have to run the 100 before the positive changes take effect?
I went to the dragstrip twice recently. The first time, on 91 octane, the power seemed to increase with each run (trap speeds rose with each run). The car also seemed unusually quick on the way home... On the second trip to the dragstrip I ran 100 octane and the same thing happened, but trap speeds rose even higher, and on the way home the car seemed to have more power than ever...
thanks for any sharing any info or experiences you may have.
first, I have heard some say the ecm "learns" how you drive and responds accordingly. Is this true? If so, on what time scale does it learn? In other words if you want a fast dragstrip time do you need to drive aggressively in the hours or days before your runs? If it has "learned" to be conservative, how long does it take to teach it otherwise?
Second, fuel octane. If the knock sensor is pulling timming, then does 100 octane prevent that from happening, and again, how long do you have to run the 100 before the positive changes take effect?
I went to the dragstrip twice recently. The first time, on 91 octane, the power seemed to increase with each run (trap speeds rose with each run). The car also seemed unusually quick on the way home... On the second trip to the dragstrip I ran 100 octane and the same thing happened, but trap speeds rose even higher, and on the way home the car seemed to have more power than ever...
thanks for any sharing any info or experiences you may have.
Fuel octane will only add power in a car that was previously experiencing knock. The ECT and IAT add/subtract tables will pull timing based on temperature regardless of how much octane you are running. Also, without changing the main spark table, you are not really taking advantage of the added octance (again assuming there was no knockto begin with).
For the other person who asked, the IAT and ECT addre tables work independently and can both pull timing at the same time. For example, if you are at the ECT and IAT temperatures that each wants to pull 2 degrees of timing, then 4 degrees will be pulled. Other tables also can add or pull timing.
Team Owner
Joined: Sep 2000
Posts: 25,033
Likes: 2,722
From: Far NW 'burbs of Chicago
St. Jude Donor '13
Don't know if there is anyway of telling HP loss from timing retard. The only example I have was my '05. On the dyno one day the Knock Retard kicked in at around 4,000 RPM and I lost 25 RWHP. It was very obvious on the Dyno chart.
Try this link for timing corrections for coolant temp;
http://forums.corvetteforum.com/phot...a/1124/ect.jpg
Somebody must have a link for timing corrections for intake air temp, the ones I have are dead.
Try this link for timing corrections for coolant temp;
http://forums.corvetteforum.com/phot...a/1124/ect.jpg
Somebody must have a link for timing corrections for intake air temp, the ones I have are dead.
Le Mans Master
Joined: Dec 2007
Posts: 5,738
Likes: 81
From: Milford NH
Ignition timing is retarded starting @ 86° intake air temp and 195° coolant temp.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
As much as 9° retard from coolant and 12° retard from intake temps.
One chart from the Forum showed ADVANCED timing ADDED with coolant temps below 158°.
Those of us with daytime air temps in the 100° range and coolant temps around 220° really suffer.
Noticed a loss in the" seat of your pants" acceleration during an unusual 6 day heat wave (95* plus temps )
Team Owner
Joined: Sep 2000
Posts: 25,033
Likes: 2,722
From: Far NW 'burbs of Chicago
St. Jude Donor '13
Racer
Joined: Dec 2006
Posts: 250
Likes: 0
From: Florida
TIMING Question LS6 Z06
To get around the warmer temps, can we add, say 3* to total timing? Then when the ECT registers 212* and pulls 3*, the net effect is zero pulled. Same with the IAT which pulls 2*'s at 86*. Question is how safe is this for the engine? Lets asume first a stock engine. Next a Tuned engine with only CAI and a Tune that has the A/F around 12.5-12.7 and no mods to the ECT, IAT tables. Will a 3* total advance produce too much additional heat for these examples? Anyone?