997 acceleration
05-03-2005, 07:51 PM
#16
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That's the other thing that was making me crazy. Sometimes it's there and sometimes it's not. I was starting to think that I might be letting off the gas. Btw I only use 93 octane
05-03-2005, 07:56 PM
#17
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This is a normal power curve for the 997. In third gear, you get a power drop at around 5700 rpm and lasts for about 2000 rpm's. Other than that, the power curve should be smooth. The S gets hit twice with this drop in power. The 3.6 996 has a similar drop but not as sharp and the 3.4 does not have a drop, but goes flat for a second.
05-03-2005, 09:01 PM
#18
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Originally Posted by Gary R.
I fixed mine. I simply accelerate harder and there is no "burp". It only happens to me during a slow acceleration and even then not all the time...
05-04-2005, 09:09 AM
#19
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You can't do a thing about it, if it is the nature of the power curve. The torque curve of the 997 is suddenly flattening around 4000, while the S shows a litlle peak around 4600 rpm.
However, 'm not sure it is the power/torque curve what I'm experiencing. I will watch closer to the rpm's next time when I notice it.
However, 'm not sure it is the power/torque curve what I'm experiencing. I will watch closer to the rpm's next time when I notice it.
05-04-2005, 01:15 PM
#20
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After watching this debate, I had to pipe up and make some comments coming from a fair amount of ECU controlled engine design and dyno time.......
You can't compare the WOT (wide open throttle) output curves to a part throttle response issue. You would be amazed at how different the shape of the output curve is at less than WOT conditions.
The ECU is using completely different A/F mixture, timing and variocam settings depending the throttle/load conditions.
Based on the WOT output curves, there is no flat spot.........those factory torque curves are absolutely normal and will feel great at WOT conditions.
The flat spot you're feeling, if it is that noticeable, would look like a definite dip in the torque and HP curves at that point under partial throttle conditions.
Problem is, we don't have the partial throttle output curves that would show this issue.
What you may have here, imho since I haven't dynoed a 997, is a part throttle, low-medium load, change in either A/F ratio, timing, variocam or other engine control valve setting
either as a result of the knock sensor or some map parameter which is changing as a part of the greater throttle/load portion of the map.
I can't speak to the extent that the aftermarket software modifies the A/F ratio, timing and variocam settings. But if the tuners have access to all of these parameters, this response issue should be able to be tuned out.
The exception would be if their is a feedback system/control valve which is either faulty or not ECU controlled, or the tuner does not have access to that portion of the code/map.
Bring it up to Porsche. Good luck....lol....they may actually know about it or have a service bulletin/fix related to the issue.
Enough complaints might start the ball rolling although frankly, they should and probably do already know about this.
If that doesn't resolve the problem, talk to the software tuners and those with their ECU changes and see if they addressed the issue or inadvertently tuned it out through their changes.
The octane issue is a possibility. But if multiple people running 93 octane are experiencing it, the solution is most likely elsewhere.
$.02 etc.
You can't compare the WOT (wide open throttle) output curves to a part throttle response issue. You would be amazed at how different the shape of the output curve is at less than WOT conditions.
The ECU is using completely different A/F mixture, timing and variocam settings depending the throttle/load conditions.
Based on the WOT output curves, there is no flat spot.........those factory torque curves are absolutely normal and will feel great at WOT conditions.
The flat spot you're feeling, if it is that noticeable, would look like a definite dip in the torque and HP curves at that point under partial throttle conditions.
Problem is, we don't have the partial throttle output curves that would show this issue.
What you may have here, imho since I haven't dynoed a 997, is a part throttle, low-medium load, change in either A/F ratio, timing, variocam or other engine control valve setting
either as a result of the knock sensor or some map parameter which is changing as a part of the greater throttle/load portion of the map.
I can't speak to the extent that the aftermarket software modifies the A/F ratio, timing and variocam settings. But if the tuners have access to all of these parameters, this response issue should be able to be tuned out.
The exception would be if their is a feedback system/control valve which is either faulty or not ECU controlled, or the tuner does not have access to that portion of the code/map.
Bring it up to Porsche. Good luck....lol....they may actually know about it or have a service bulletin/fix related to the issue.
Enough complaints might start the ball rolling although frankly, they should and probably do already know about this.
If that doesn't resolve the problem, talk to the software tuners and those with their ECU changes and see if they addressed the issue or inadvertently tuned it out through their changes.
The octane issue is a possibility. But if multiple people running 93 octane are experiencing it, the solution is most likely elsewhere.
$.02 etc.
05-04-2005, 02:31 PM
#22
Race Car
Originally Posted by CARV
After watching this debate, I had to pipe up and make some comments coming from a fair amount of ECU controlled engine design and dyno time.......
You can't compare the WOT (wide open throttle) output curves to a part throttle response issue. You would be amazed at how different the shape of the output curve is at less than WOT conditions.
The ECU is using completely different A/F mixture, timing and variocam settings depending the throttle/load conditions.
Based on the WOT output curves, there is no flat spot.........those factory torque curves are absolutely normal and will feel great at WOT conditions.
The flat spot you're feeling, if it is that noticeable, would look like a definite dip in the torque and HP curves at that point under partial throttle conditions.
Problem is, we don't have the partial throttle output curves that would show this issue.
What you may have here, imho since I haven't dynoed a 997, is a part throttle, low-medium load, change in either A/F ratio, timing, variocam or other engine control valve setting
either as a result of the knock sensor or some map parameter which is changing as a part of the greater throttle/load portion of the map.
I can't speak to the extent that the aftermarket software modifies the A/F ratio, timing and variocam settings. But if the tuners have access to all of these parameters, this response issue should be able to be tuned out.
The exception would be if their is a feedback system/control valve which is either faulty or not ECU controlled, or the tuner does not have access to that portion of the code/map.
Bring it up to Porsche. Good luck....lol....they may actually know about it or have a service bulletin/fix related to the issue.
Enough complaints might start the ball rolling although frankly, they should and probably do already know about this.
If that doesn't resolve the problem, talk to the software tuners and those with their ECU changes and see if they addressed the issue or inadvertently tuned it out through their changes.
The octane issue is a possibility. But if multiple people running 93 octane are experiencing it, the solution is most likely elsewhere.
$.02 etc.
You can't compare the WOT (wide open throttle) output curves to a part throttle response issue. You would be amazed at how different the shape of the output curve is at less than WOT conditions.
The ECU is using completely different A/F mixture, timing and variocam settings depending the throttle/load conditions.
Based on the WOT output curves, there is no flat spot.........those factory torque curves are absolutely normal and will feel great at WOT conditions.
The flat spot you're feeling, if it is that noticeable, would look like a definite dip in the torque and HP curves at that point under partial throttle conditions.
Problem is, we don't have the partial throttle output curves that would show this issue.
What you may have here, imho since I haven't dynoed a 997, is a part throttle, low-medium load, change in either A/F ratio, timing, variocam or other engine control valve setting
either as a result of the knock sensor or some map parameter which is changing as a part of the greater throttle/load portion of the map.
I can't speak to the extent that the aftermarket software modifies the A/F ratio, timing and variocam settings. But if the tuners have access to all of these parameters, this response issue should be able to be tuned out.
The exception would be if their is a feedback system/control valve which is either faulty or not ECU controlled, or the tuner does not have access to that portion of the code/map.
Bring it up to Porsche. Good luck....lol....they may actually know about it or have a service bulletin/fix related to the issue.
Enough complaints might start the ball rolling although frankly, they should and probably do already know about this.
If that doesn't resolve the problem, talk to the software tuners and those with their ECU changes and see if they addressed the issue or inadvertently tuned it out through their changes.
The octane issue is a possibility. But if multiple people running 93 octane are experiencing it, the solution is most likely elsewhere.
$.02 etc.
05-04-2005, 02:32 PM
#23
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Not true, there are many stations around each big city in California with 100 oct unleaded for you to mix with..........
Since I don't have my 997S yet, I can't go out and test the octane/knock issue.
What I can tell you is that the car shouldn't be pulling timing under partial throttle with 93 octane fuel like some are hinting at.
Octane is most likely not the problem if 93 oct is showing the issue unless they got some incorrectly marked fuel.
Since I don't have my 997S yet, I can't go out and test the octane/knock issue.
What I can tell you is that the car shouldn't be pulling timing under partial throttle with 93 octane fuel like some are hinting at.
Octane is most likely not the problem if 93 oct is showing the issue unless they got some incorrectly marked fuel.
05-04-2005, 02:45 PM
#25
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Originally Posted by 1999Porsche911
...it has a "power drop spot". This starts at around 5600 rpm and continue to drop for the next 2000 rpm's or so...
05-04-2005, 02:49 PM
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CARV: thanks for expanding in that area. I know of all the differences in the curves at different loads and throttle conditions. Maybe we need to spend a thread on that subject.
When talking about flatening, I'm not talking about the power curve, but about the torque curve.
The experience hint to mapping. I can't imagine that the computer system is delayed, as it is so much faster than anything else happening. However, it sometimes looks like there is a late response of something.
Indeed, maybe some of the tuners or even a Porsche experts silently reading with us, knows about this. Would be great if somebody steps up and shares that knowledge.
When talking about flatening, I'm not talking about the power curve, but about the torque curve.
The experience hint to mapping. I can't imagine that the computer system is delayed, as it is so much faster than anything else happening. However, it sometimes looks like there is a late response of something.
Indeed, maybe some of the tuners or even a Porsche experts silently reading with us, knows about this. Would be great if somebody steps up and shares that knowledge.
05-04-2005, 02:52 PM
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1999, there are two seperate issues going on in this thread. One is a "hard acceleration" flat spot from 4800-5000 rpm that the original poster related to which I'm assuming was WOT.
The other is a partial throttle flat spot in the low-mid 3000rpm range which others have related to.
I have driven the 997S enough to notice the variocam increase in torque beginning around 4000rpm, but did not notice your 5600rpm "power drop spot".
I think you mean 5600 rpm torque reduction as the power is still increasing at that point, although as you should know, it's just a calculation off of torque and engine speed.
The torque curve in the 997S felt like a normal curve after the variocam change to me.
So we have you talking about a torque issue at 5600rpm, another guy talking about a 4800-5000rpm flat spot under heavy acceleration and others talking about a partial throttle flat spot in the low-mid 3000rpm range.
Each issue should be addressed seperately to isolate what's going on imho.
The other is a partial throttle flat spot in the low-mid 3000rpm range which others have related to.
I have driven the 997S enough to notice the variocam increase in torque beginning around 4000rpm, but did not notice your 5600rpm "power drop spot".
I think you mean 5600 rpm torque reduction as the power is still increasing at that point, although as you should know, it's just a calculation off of torque and engine speed.
The torque curve in the 997S felt like a normal curve after the variocam change to me.
So we have you talking about a torque issue at 5600rpm, another guy talking about a 4800-5000rpm flat spot under heavy acceleration and others talking about a partial throttle flat spot in the low-mid 3000rpm range.
Each issue should be addressed seperately to isolate what's going on imho.
Last edited by CARV; 05-04-2005 at 03:23 PM.
05-04-2005, 02:54 PM
#28
Race Car
Originally Posted by PV
CARV: thanks for expanding in that area. I know of all the differences in the curves at different loads and throttle conditions. Maybe we need to spend a thread on that subject.
When talking about flatening, I'm not talking about the power curve, but about the torque curve.
The experience hint to mapping. I can't imagine that the computer system is delayed, as it is so much faster than anything else happening. However, it sometimes looks like there is a late response of something.
Indeed, maybe some of the tuners or even a Porsche experts silently reading with us, knows about this. Would be great if somebody steps up and shares that knowledge.
When talking about flatening, I'm not talking about the power curve, but about the torque curve.
The experience hint to mapping. I can't imagine that the computer system is delayed, as it is so much faster than anything else happening. However, it sometimes looks like there is a late response of something.
Indeed, maybe some of the tuners or even a Porsche experts silently reading with us, knows about this. Would be great if somebody steps up and shares that knowledge.
Todd has a good example on his site.
http://www.evoms.com/porsche%20ec%20art%20test.htm
05-04-2005, 02:55 PM
#29
Rennlist Member
I just got back from a nice backroad romp. I will make one last comment... Drive the car hard and the little "stumble" at around 3000 RPM is non-existant. My car pulls hard in 1st-4th gear up to 6800 (as high as I want to go) and i'm sure would to 6th if I had a place to do it safely. I thought this "stumble" was what we were talking about, not the "Power Curve".. if I missed the point I apologize.
