Hearing knock w/ 2.85 pulley and 60# injectors
06-04-2008, 12:50 PM
#28
what happens to our engines is the ecu sees the increased airflow and instructs the injectors to dump more fuel in an attempt to maintain the commanded afr. if the injectors cannot supply enough fuel to maintain commanded afr, then the injectors go static and the afr will lean out.
so the theory is correct, but that doesnt mean you want to apply it to your car...
so the theory is correct, but that doesnt mean you want to apply it to your car...
06-04-2008, 01:00 PM
#29
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I was tell him to up pulley size to reduce heat, and increase blower efficency even though it is only by a fraction of an inch. I wasn't say to change pulley size to adjust AFR
06-04-2008, 01:10 PM
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To the OP, get some cooling mods and be sure you're getting a good tank of gas. Also, pull the plugs and give them a check as well. You might want to have the tuner do a quick scan and take a degree or so out. Finally, be on the lookout in September time frame because I will be back in town in Nashua, NH for some leave!
06-04-2008, 01:12 PM
#32
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what happens to our engines is the ecu sees the increased airflow and instructs the injectors to dump more fuel in an attempt to maintain the commanded afr. if the injectors cannot supply enough fuel to maintain commanded afr, then the injectors go static and the afr will lean out.
so the theory is correct, but that doesnt mean you want to apply it to your car...
so the theory is correct, but that doesnt mean you want to apply it to your car...
06-04-2008, 01:40 PM
#33
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well you really need to determine exactly what the knock is being caused from. Did GM scan the car and see the knock? You should take it to the tuner and have them do a scan and see if the car is actually seeing knock or if you have some other problem.
Check to see if its RPM related, put the car in neutral and rev the engine, if your still hearing the knock chances are its not fuel knock but something related to the internals. I know a loose wrist pin can cause something similar to knock, where it only happens between a certain RPM range, but this will happen in neutral.
First a foremost STOP MAKING IT KNOCK. Take it to the tuner and have them scan it. Also the tune could very well be the problem, there is a difference between how and engine needs to be tunned for road as compared to a dyno. Dynos usually putting less stress on the motor than the road.
From my experience badgas will cause the car to trip and stumble as opposed to making audiable knocks. Do you notice a power decrease with the knocks? You said it only happens at WOT? Have you been keeping an eye on the PSI at the time?
Check to see if its RPM related, put the car in neutral and rev the engine, if your still hearing the knock chances are its not fuel knock but something related to the internals. I know a loose wrist pin can cause something similar to knock, where it only happens between a certain RPM range, but this will happen in neutral.
First a foremost STOP MAKING IT KNOCK. Take it to the tuner and have them scan it. Also the tune could very well be the problem, there is a difference between how and engine needs to be tunned for road as compared to a dyno. Dynos usually putting less stress on the motor than the road.
From my experience badgas will cause the car to trip and stumble as opposed to making audiable knocks. Do you notice a power decrease with the knocks? You said it only happens at WOT? Have you been keeping an eye on the PSI at the time?
06-04-2008, 06:39 PM
#34
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well you really need to determine exactly what the knock is being caused from. Did GM scan the car and see the knock? You should take it to the tuner and have them do a scan and see if the car is actually seeing knock or if you have some other problem.
Check to see if its RPM related, put the car in neutral and rev the engine, if your still hearing the knock chances are its not fuel knock but something related to the internals. I know a loose wrist pin can cause something similar to knock, where it only happens between a certain RPM range, but this will happen in neutral.
First a foremost STOP MAKING IT KNOCK. Take it to the tuner and have them scan it. Also the tune could very well be the problem, there is a difference between how and engine needs to be tunned for road as compared to a dyno. Dynos usually putting less stress on the motor than the road.
From my experience badgas will cause the car to trip and stumble as opposed to making audiable knocks. Do you notice a power decrease with the knocks? You said it only happens at WOT? Have you been keeping an eye on the PSI at the time?
Check to see if its RPM related, put the car in neutral and rev the engine, if your still hearing the knock chances are its not fuel knock but something related to the internals. I know a loose wrist pin can cause something similar to knock, where it only happens between a certain RPM range, but this will happen in neutral.
First a foremost STOP MAKING IT KNOCK. Take it to the tuner and have them scan it. Also the tune could very well be the problem, there is a difference between how and engine needs to be tunned for road as compared to a dyno. Dynos usually putting less stress on the motor than the road.
From my experience badgas will cause the car to trip and stumble as opposed to making audiable knocks. Do you notice a power decrease with the knocks? You said it only happens at WOT? Have you been keeping an eye on the PSI at the time?
My tuner is about 400 miles away during the whole summer, so I'm gonna see if I can get it scanned by a local shop (btw if anyone knows of any good shops that can do this in S. New Hampshire let me know). However the problem did not begin for over 700 miles after the tune was performed. It does not knock when revved, I doubt it is internals because it does not sound like rod knock, lifter tick, valve slap, etc and I have a pretty keen ear when it comes to that stuff. Dealer did not scan it, but tech was certain it was "fuel ping," and I trust this guy he's been around these cars a lot. As soon as the problem is diagnosed I'll be sure to update. Thanks guys.
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