Creeker
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- First Name
- Jim
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- Nov 19, 2019
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- Hickory, NC
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Interesting SAE paper about pre-ignition (pre-detonation) at low RPM
https://www.fev.com/fileadmin/user_...arged_direct-injected_gasoline_engines_01.pdf
A couple of clips from above.
In contrast to conventional engine knocking in gasoline engines, which is typically controlled by knock control algorithms in the ECU, pre-ignition is considered uncontrollable. According to Heywood [1] knocking is the self-ignition process in the end-gas regime prior to arrival of regular flame front and is dependent on temperature and pressure time history. It can be controlled by spark timing adjustments and all modern gasoline engine control units have specific knock control algorithms in order to react to knocking combustion. Pre-ignition on the other hand is characterized by a start of combustion prior spark ignition without the inducement of local component overheating. These sharp erratic cracks caused by the significantly increased fuel conversion rate can lead to significantly higher cylinder peak pressures, much higher than typically seen in knocking events. The peak pressures and maximum rise rates as measured during pre-ignition can lead to instant severe engine damages. Therefore it is important to understand the Page 2 of 20 mechanisms which lead to pre-ignition in order to make engines less sensitive to pre-ignition. Only then it will be possible to push the envelope to even higher load levels within gasoline engines.
From the results obtained by the performed DOE test runs it can be furthermore derived that fuel quality (B) seems to have by far the biggest impact on pre-ignition threshold variance (8bar), followed by enrichment (G) and intake temperature (D), whereas spark plug design (E), and injection timing (H) strongly influence pre-ignition threshold robustness.
Granted that the paper above focuses on turbo engines and direct injection issues. However, pre-ignition can be heard on the 3.6 engine when running 87 octane and wheeling/crawling at low RPM. For the ECU to control knocking (pre-detonation, pre-ignition, pinging, etc.) that means that the ECU is "hearing" the pinging and changing the engine controls to avoid the pinging. Therefore, pinging is still occurring in the engine.
Based on the information in this SAE paper and other SAE papers, IMHO, this pinging sound in a Jeep engine is not good. How bad is the pinging in a 3.6 motor and what are the long term effects, who knows. My rig is going to run on 93 octane. It's your rig, run what you want.
https://www.fev.com/fileadmin/user_...arged_direct-injected_gasoline_engines_01.pdf
A couple of clips from above.
In contrast to conventional engine knocking in gasoline engines, which is typically controlled by knock control algorithms in the ECU, pre-ignition is considered uncontrollable. According to Heywood [1] knocking is the self-ignition process in the end-gas regime prior to arrival of regular flame front and is dependent on temperature and pressure time history. It can be controlled by spark timing adjustments and all modern gasoline engine control units have specific knock control algorithms in order to react to knocking combustion. Pre-ignition on the other hand is characterized by a start of combustion prior spark ignition without the inducement of local component overheating. These sharp erratic cracks caused by the significantly increased fuel conversion rate can lead to significantly higher cylinder peak pressures, much higher than typically seen in knocking events. The peak pressures and maximum rise rates as measured during pre-ignition can lead to instant severe engine damages. Therefore it is important to understand the Page 2 of 20 mechanisms which lead to pre-ignition in order to make engines less sensitive to pre-ignition. Only then it will be possible to push the envelope to even higher load levels within gasoline engines.
From the results obtained by the performed DOE test runs it can be furthermore derived that fuel quality (B) seems to have by far the biggest impact on pre-ignition threshold variance (8bar), followed by enrichment (G) and intake temperature (D), whereas spark plug design (E), and injection timing (H) strongly influence pre-ignition threshold robustness.
Granted that the paper above focuses on turbo engines and direct injection issues. However, pre-ignition can be heard on the 3.6 engine when running 87 octane and wheeling/crawling at low RPM. For the ECU to control knocking (pre-detonation, pre-ignition, pinging, etc.) that means that the ECU is "hearing" the pinging and changing the engine controls to avoid the pinging. Therefore, pinging is still occurring in the engine.
Based on the information in this SAE paper and other SAE papers, IMHO, this pinging sound in a Jeep engine is not good. How bad is the pinging in a 3.6 motor and what are the long term effects, who knows. My rig is going to run on 93 octane. It's your rig, run what you want.
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