Ignition timing 101
02-01-2005, 12:16 PM
#41
This is very interesting no doubt. I have had greatly improved results by running additional timing. This was most noticable with my 60 fts not MPH. My car went through a spell where it would jump from the HO table to the LO randomly and the ET would show a loss of power that matched the logged timing table. The gain was almost all in the 60 fts. At that time the HO runs that would hold would give me 1.44-1.45 60fts and when it dropped to the LO table the 60 fts would go to 1.51-1.53 and this was very noticable in the SOTP.
My thoughts are that there may be some realistic gains to have additional timing at the lower (2800-5000) rpm and given load G/cyl and taper the timing back to the higher rpms at given G/cyl. My goal is to get the best of both worlds with minimal strain or damage risk to the motor internals. This motor was also a bit high on the compression so that may also play a role as to why it responded well to low end timing. I just thought I'd share some real world results to support some of the previous theories.
My thoughts are that there may be some realistic gains to have additional timing at the lower (2800-5000) rpm and given load G/cyl and taper the timing back to the higher rpms at given G/cyl. My goal is to get the best of both worlds with minimal strain or damage risk to the motor internals. This motor was also a bit high on the compression so that may also play a role as to why it responded well to low end timing. I just thought I'd share some real world results to support some of the previous theories.
02-01-2005, 02:03 PM
#43
6600 rpm clutch dump of death Administrator
Thread Starter
Good stuff James!
I don't necessarily think adding timing in places is a bad thing. I was more trying to highlight that adding a ton of advance up top is necessarily making more power. If you have empirical data showing your car gains with timing, I would certainly beleive it. I can alos see at low engine speed when you have some overlap needing to add some spark timing to pick up power. Thats why I like an engine dyno. You can see the effect of timing in all the ranges.
I don't necessarily think adding timing in places is a bad thing. I was more trying to highlight that adding a ton of advance up top is necessarily making more power. If you have empirical data showing your car gains with timing, I would certainly beleive it. I can alos see at low engine speed when you have some overlap needing to add some spark timing to pick up power. Thats why I like an engine dyno. You can see the effect of timing in all the ranges.
02-02-2005, 09:07 AM
#44
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Thats how I tune my Monaro. I have 27.5* at around 2400-2800 then tapering off to 22.5* at 5200. Its an uncracked engine with just bolt-ons. Everyone who dirves it or sits in it comments on the TQ delivery.
02-02-2005, 11:49 AM
#46
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02-02-2005, 12:20 PM
#47
Originally Posted by PewterZ28
All I know is I bumped up my entire timing table on my '02 Z28 and knocked about .10~.12 off my ET and gained 1 mph. Max timing used to be about 22 now it's around 30. Maybe I'm playing with fire 
but the gains are real. However, I did have to lower the timing by a few degrees around 4000 rpm because I was getting slight detonation there. After I lowered it the spark knock was gone.
but the gains are real. However, I did have to lower the timing by a few degrees around 4000 rpm because I was getting slight detonation there. After I lowered it the spark knock was gone.
03-01-2005, 03:45 AM
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I have to agree with J-rod on this one. I dynoed my car about year ago with the predator. It made the most power at 25 degrees running lean. about 870-880.(325rwhp) With my timing at 27 it made about (3rwhp less). I never thought about richen it up to see if it would make more power. I didnt know how to use it. In the beging. I redynoed with my headers with 25 degrees and made 350rwhp now..
With 27 it feels quick off the line,but dies out in the topend.
my Mods where lid/magnaflowmuffler/predator/ory-pipe. 2oo2 a4
With 27 it feels quick off the line,but dies out in the topend.
my Mods where lid/magnaflowmuffler/predator/ory-pipe. 2oo2 a4
03-01-2005, 08:34 AM
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Anyone have an HO table for a G5X-3 cam or similar, that was tuned on the dyno. I would like to compare it to mine. I'm running shitloads of timing, and while the car runs great, I am now starting to second guess myself. I pretty much dialed in my timing using the advance till it pings then back off method, and sotp.
04-15-2005, 08:04 AM
#51
6600 rpm clutch dump of death Administrator
Thread Starter
I'm bumping this thread back up since there seems to be some confusion about timing, what it is, what it does, and how much of it you need.
Per this locked thread...
https://ls1tech.com/forums/showthrea...=1#post2765921
Per this locked thread...
https://ls1tech.com/forums/showthrea...=1#post2765921
04-15-2005, 09:03 AM
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This is great. I can't wait to get home from work (firewall 
) to read the rest. I've only started and have found a few terms I have been mis-applying.
Thanks man.
) to read the rest. I've only started and have found a few terms I have been mis-applying.Thanks man.
04-15-2005, 10:40 AM
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SAE 2000-01-0932: Cylinder-Pressure-Based Engine Control... Excerpts from SAE 2000-01-0932 Cylinder-Pressure-Based Engine Control Using Pressure-Ratio-Management and Low-Cost Non-Intrusive Cylinder Pressure Sensors
Over the last two decades, advanced engine control systems have been developed that use cylinder pressure as the primary feedback variable. Production application has been limited by cost, reliability, and packaging difficulties associated with intrusive cylinder pressure sensors. Now, a low-cost cylinder-pressure-based engine control system has been developed that utilizes Pressure-Ratio Management (PRM) and non-intrusive cylinder pressure sensors mounted in the spark plug boss of four-valve-per-cylinder engines. The system adaptively optimizes individual-cylinder spark timing and air-fuel ratio, and overall exhaust gas recirculation (EGR) for best fuel economy and lowest emissions over the life of each vehicle.
...
Development of advanced engine control systems for the modern 4-stroke gasoline engine is being driven by demand for higher fuel economy and increasingly stringent exhaust emissions standards. Additionally, emissions compliance must be maintained for increasing service duration while On-Board-Diagnostics (OBDII) requirements are satisfied.
Individual-cylinder, cylinder-pressure-based feedback control is an ideal method to optimize engine operation [1, 2] (numbers in brackets indicate references found at the end of this paper) over vehicle life while fulfilling diagnostics requirements. Cylinder pressure is a fundamental combustion variable, which can be used to characterize the combustion process for each combustion event. Optimal engine control can be maintained by monitoring the pressure in each cylinder and using this information for feedback control of spark timing, exhaust gas recirculation (EGR), air-fuel ratio (A/F), and combustion knock. The system is not proposed, however, as a replacement for stoichiometric A/F control using an oxygen sensor, however, for lean systems, such replacement has been demonstrated.
The ability to sense and adapt for factors that produce deviations from the best open-loop calibration yields a wide range of benefits. These benefits are summarized in Tables 1 and 2 below. Fuel economy may be increased and nitrogen oxide (NOx) emissions decreased by operation with higher levels of EGR or with leaner A/F ratios than would normally be practical. Further efficiency gains result by operation of each cylinder at Minimum Spark Advance for Best Torque (MBT), thereby compensating for burn rate and spark requirement differences from cylinder-to-cylinder. Cylinder-pressurebased control can adapt for environmental factors, component manufacturing variations, component wear, and component degradation of various types, effectively reducing exhaust emissions dispersion and deterioration for an aging fleet. Cold start fueling algorithms that are based on cylinder pressure measurements may substantially reduce exhaust hydrocarbon (HC) emissions.
Improved detection of combustion knock and pre-ignition enables safe operation closer to MBT spark advance, while cylinder pressure sensing provides outstanding detection of misfire and partial burn cycles for the full range of engine operating conditions. As future automotive engine systems become more complex, cylinder-pressure-based control enables reduced dependency on expanding open-loop calibrations and may simplify calibration requirements while speeding the overall calibration process.
...
The most common type of cylinder pressure sensors are intrusive devices that package through the combustion chamber wall [7-20]. While intrusive sensors are evolving into smaller designs, production viability of packaging these sensors within the crowded space of an engine cylinder head remains a formidable challenge throughout the industry. Cost of these devices is generally high and the hostile thermal and mechanical environment of the combustion chamber introduces serious durability concerns.
Non-intrusive sensors [21-35] do not require direct access to the combustion chamber. Pressure is detected indirectly by sensing stress in an existing engine component (e.g., head bolt). Because of their integration into existing components, non-intrusive devices are generally lower cost than intrusive sensors. However, signal quality depends strongly on the mechanical load path of the resulting package and is often below requirements. In-spark-plug devices [36-43] have been of interest since they do not require an additional access port to the combustion chamber. Significant engineering resources have been applied recently to develop an integrated spark plug pressure sensor as part of the ignition subsystem. Unfortunately, use of piezoelectric, fiber optic, or magnetostrictive sensing technology has not resulted in a practical, low-cost, in-spark-plug device.
...
SENSOR LOAD PATH DESCRIPTION – The SPB pressure sensor operates in a structural load path that is very linear and well behaved. Cylinder pressure acting on the combustion chamber creates a force that is elastically transferred through the cylinder head structure to the head bolts. A portion of this total force is transferred in compression through the spark plug boss and has a magnitude of about 2200 N at maximum cylinder pressure (6.8 MPa). This provides a reasonable but not excessive force for sensing. To detect the force, a shoulder is machined on the inner diameter of the spark plug boss and the sensor is preloaded onto the shoulder using fastening threads. To accommodate the sensor, the cast outer diameter of the upper spark plug boss is increased about 6 mm. Because the sensor is located high within the spark plug boss, the sensor has no detrimental effect on spark plug cooling. The sensor is responsive to compressive forces applied through the sensor bottom face (see Figure 3).
...
The advantages of this overall sensing concept are:
1. Direct access to the combustion chamber is not required
2. Due to abundance of cooling water surrounding the spark plug boss, sensor operating temperatures and hot soak temperatures are relatively low (140 C maximum).
3. Due to mounting outside of the combustion chamber, the sensor is insensitive to several common types of thermal errors including intracycle flame arrival effects and signal drift during engine load transients.
...
SPARK-PLUG-BOSS CYLINDER PRESSURE
SENSOR – Referring to Figures 5 and 6, The Spark-Plug-Boss Sensor is a simple force transducer with an annular cross sectional shape. The inner diameter of the sensor equals the diameter of the spark plug well. The sensor is comprised of six components arranged on a single axial centerline [73]. This enables low-cost assembly of the sensor using automated tools and procedures. A deep-drawn aluminum can shields the sensor assembly on the inner diameter. The assembly is sealed hermetically using dispensed silicone sealants.
Mechanical loads acting on the sensor are transferred upward in compression through the sensor shield, the protection washer, and the piezoceramic element to the threaded shell. The fastening threads on the shell are a 5-degree buttress design that align thread loads axially for linear load transfer characteristics [74]. To minimize thermal-induced error signals, the shell is fabricated from high-strength aluminum alloy, which has a coefficient of thermal expansion equal to that of the aluminum cylinder head. The shell is nickel plated to prevent thread galling and corrosion.
...
AIR-FUEL RATIO BALANCING – Cylinder-to-cylinder A/F imbalances in spark-ignited engines may originate from both unequal fuel flow and unequal airflow to the cylinders. Typically, production injectors have matched flow rate within 3 to 6 percent. Over life as injectors age, fuel delivery may be altered by an additional + / - 10 percent. The combined effect can be substantial, and may approach a four A/F spread. A/F imbalances can also result from fuel transport among cylinders caused by strong intake back flows at light-load operating conditions.
A/F imbalances can significantly compromise engine operation and control in a variety of ways. Driveability problems can arise because of reduced dilution tolerance for cylinders with leaner mixtures. This may limit maximum calibrated EGR levels. Air-fuel control accuracy may also be compromised and may result in both increased emissions and increased variation of emissions vehicle-to-vehicle. Generally, engine performance will be reduced by A/F imbalances since one or more cylinders may not be fueled optimally for maximum power generation.
...
KNOCK DETECTION – The Spark-Plug-Boss Sensor is located a short distance directly above each combustion chamber. The mechanical load path between the combustion chamber and the sensor is very stiff and provides good response to knock-induced structural vibrations over a wide range of frequencies. Valve train noise, such as noise created at valve closing, occurs outside the knock interval and may be windowed out using available signal processing techniques. Since the SPB Sensor is located relatively far from the engine block, sensitivity to block noise is generally low.
Over the last two decades, advanced engine control systems have been developed that use cylinder pressure as the primary feedback variable. Production application has been limited by cost, reliability, and packaging difficulties associated with intrusive cylinder pressure sensors. Now, a low-cost cylinder-pressure-based engine control system has been developed that utilizes Pressure-Ratio Management (PRM) and non-intrusive cylinder pressure sensors mounted in the spark plug boss of four-valve-per-cylinder engines. The system adaptively optimizes individual-cylinder spark timing and air-fuel ratio, and overall exhaust gas recirculation (EGR) for best fuel economy and lowest emissions over the life of each vehicle.
...
Development of advanced engine control systems for the modern 4-stroke gasoline engine is being driven by demand for higher fuel economy and increasingly stringent exhaust emissions standards. Additionally, emissions compliance must be maintained for increasing service duration while On-Board-Diagnostics (OBDII) requirements are satisfied.
Individual-cylinder, cylinder-pressure-based feedback control is an ideal method to optimize engine operation [1, 2] (numbers in brackets indicate references found at the end of this paper) over vehicle life while fulfilling diagnostics requirements. Cylinder pressure is a fundamental combustion variable, which can be used to characterize the combustion process for each combustion event. Optimal engine control can be maintained by monitoring the pressure in each cylinder and using this information for feedback control of spark timing, exhaust gas recirculation (EGR), air-fuel ratio (A/F), and combustion knock. The system is not proposed, however, as a replacement for stoichiometric A/F control using an oxygen sensor, however, for lean systems, such replacement has been demonstrated.
The ability to sense and adapt for factors that produce deviations from the best open-loop calibration yields a wide range of benefits. These benefits are summarized in Tables 1 and 2 below. Fuel economy may be increased and nitrogen oxide (NOx) emissions decreased by operation with higher levels of EGR or with leaner A/F ratios than would normally be practical. Further efficiency gains result by operation of each cylinder at Minimum Spark Advance for Best Torque (MBT), thereby compensating for burn rate and spark requirement differences from cylinder-to-cylinder. Cylinder-pressurebased control can adapt for environmental factors, component manufacturing variations, component wear, and component degradation of various types, effectively reducing exhaust emissions dispersion and deterioration for an aging fleet. Cold start fueling algorithms that are based on cylinder pressure measurements may substantially reduce exhaust hydrocarbon (HC) emissions.
Improved detection of combustion knock and pre-ignition enables safe operation closer to MBT spark advance, while cylinder pressure sensing provides outstanding detection of misfire and partial burn cycles for the full range of engine operating conditions. As future automotive engine systems become more complex, cylinder-pressure-based control enables reduced dependency on expanding open-loop calibrations and may simplify calibration requirements while speeding the overall calibration process.
...
The most common type of cylinder pressure sensors are intrusive devices that package through the combustion chamber wall [7-20]. While intrusive sensors are evolving into smaller designs, production viability of packaging these sensors within the crowded space of an engine cylinder head remains a formidable challenge throughout the industry. Cost of these devices is generally high and the hostile thermal and mechanical environment of the combustion chamber introduces serious durability concerns.
Non-intrusive sensors [21-35] do not require direct access to the combustion chamber. Pressure is detected indirectly by sensing stress in an existing engine component (e.g., head bolt). Because of their integration into existing components, non-intrusive devices are generally lower cost than intrusive sensors. However, signal quality depends strongly on the mechanical load path of the resulting package and is often below requirements. In-spark-plug devices [36-43] have been of interest since they do not require an additional access port to the combustion chamber. Significant engineering resources have been applied recently to develop an integrated spark plug pressure sensor as part of the ignition subsystem. Unfortunately, use of piezoelectric, fiber optic, or magnetostrictive sensing technology has not resulted in a practical, low-cost, in-spark-plug device.
...
SENSOR LOAD PATH DESCRIPTION – The SPB pressure sensor operates in a structural load path that is very linear and well behaved. Cylinder pressure acting on the combustion chamber creates a force that is elastically transferred through the cylinder head structure to the head bolts. A portion of this total force is transferred in compression through the spark plug boss and has a magnitude of about 2200 N at maximum cylinder pressure (6.8 MPa). This provides a reasonable but not excessive force for sensing. To detect the force, a shoulder is machined on the inner diameter of the spark plug boss and the sensor is preloaded onto the shoulder using fastening threads. To accommodate the sensor, the cast outer diameter of the upper spark plug boss is increased about 6 mm. Because the sensor is located high within the spark plug boss, the sensor has no detrimental effect on spark plug cooling. The sensor is responsive to compressive forces applied through the sensor bottom face (see Figure 3).
...
The advantages of this overall sensing concept are:
1. Direct access to the combustion chamber is not required
2. Due to abundance of cooling water surrounding the spark plug boss, sensor operating temperatures and hot soak temperatures are relatively low (140 C maximum).
3. Due to mounting outside of the combustion chamber, the sensor is insensitive to several common types of thermal errors including intracycle flame arrival effects and signal drift during engine load transients.
...
SPARK-PLUG-BOSS CYLINDER PRESSURE
SENSOR – Referring to Figures 5 and 6, The Spark-Plug-Boss Sensor is a simple force transducer with an annular cross sectional shape. The inner diameter of the sensor equals the diameter of the spark plug well. The sensor is comprised of six components arranged on a single axial centerline [73]. This enables low-cost assembly of the sensor using automated tools and procedures. A deep-drawn aluminum can shields the sensor assembly on the inner diameter. The assembly is sealed hermetically using dispensed silicone sealants.
Mechanical loads acting on the sensor are transferred upward in compression through the sensor shield, the protection washer, and the piezoceramic element to the threaded shell. The fastening threads on the shell are a 5-degree buttress design that align thread loads axially for linear load transfer characteristics [74]. To minimize thermal-induced error signals, the shell is fabricated from high-strength aluminum alloy, which has a coefficient of thermal expansion equal to that of the aluminum cylinder head. The shell is nickel plated to prevent thread galling and corrosion.
...
AIR-FUEL RATIO BALANCING – Cylinder-to-cylinder A/F imbalances in spark-ignited engines may originate from both unequal fuel flow and unequal airflow to the cylinders. Typically, production injectors have matched flow rate within 3 to 6 percent. Over life as injectors age, fuel delivery may be altered by an additional + / - 10 percent. The combined effect can be substantial, and may approach a four A/F spread. A/F imbalances can also result from fuel transport among cylinders caused by strong intake back flows at light-load operating conditions.
A/F imbalances can significantly compromise engine operation and control in a variety of ways. Driveability problems can arise because of reduced dilution tolerance for cylinders with leaner mixtures. This may limit maximum calibrated EGR levels. Air-fuel control accuracy may also be compromised and may result in both increased emissions and increased variation of emissions vehicle-to-vehicle. Generally, engine performance will be reduced by A/F imbalances since one or more cylinders may not be fueled optimally for maximum power generation.
...
KNOCK DETECTION – The Spark-Plug-Boss Sensor is located a short distance directly above each combustion chamber. The mechanical load path between the combustion chamber and the sensor is very stiff and provides good response to knock-induced structural vibrations over a wide range of frequencies. Valve train noise, such as noise created at valve closing, occurs outside the knock interval and may be windowed out using available signal processing techniques. Since the SPB Sensor is located relatively far from the engine block, sensitivity to block noise is generally low.
04-15-2005, 10:40 AM
#54
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SUMMARY AND CONCLUSIONS
A production-viable cylinder-pressure-based engine control system with extensive system benefits has been demonstrated on a spark-ignited four-cylinder gasoline engine. The system adaptively optimizes combustion for every cycle in each cylinder over the life of each vehicle. Precise engine control was demonstrated for a variety of functions including spark timing control, dilution control, A/F balancing, cold start fueling, misfire detection, and knock detection.
The current work offers a new solution to the technical and commercial limitations of other pressure-based control systems. The technology developed reduces the cost and complexity historically associated with pressurebased systems, while providing increased control functionality. An essential objective of the work was to develop robust, computationally efficient algorithms that do not require highly accurate or absolute measures of cylinder pressure. Pressure-Ratio-Management was presented and the ratio of fired-to-motored pressure was established as a means to efficiently estimate combustion phasing and mixture dilution for each cycle.
A non-intrusive cylinder pressure sensor that satisfies PRM requirements was conceived and developed. The sensor uses piezoelectric sensing technology to detect compressive forces in the spark plug boss of four-valveper-cylinder engines in response to cylinder pressure. The sensor incorporates a linear piezoceramic material and a high-temperature integral electronic amplifier. A single wire connected to the sensor provides a constant current to the amplifier and returns a voltage signal to an electrical interface at the engine controller. The sensor system has potentially excellent durability with estimated cost between one half to one quarter that of competitive intrusive sensors.
The control system has potential to measure trapped air in each cylinder using cylinder pressure measurements. Possibly, the air meter may be eliminated and system cost further reduced. Additional work is needed to develop this functionality. Although the system has been applied to conventional S.I. engines in this work, extension to the common-rail diesel, direct-injection gasoline, and homogeneous-charge compression ignition engines may enable combustion control for these engines as well.
A production-viable cylinder-pressure-based engine control system with extensive system benefits has been demonstrated on a spark-ignited four-cylinder gasoline engine. The system adaptively optimizes combustion for every cycle in each cylinder over the life of each vehicle. Precise engine control was demonstrated for a variety of functions including spark timing control, dilution control, A/F balancing, cold start fueling, misfire detection, and knock detection.
The current work offers a new solution to the technical and commercial limitations of other pressure-based control systems. The technology developed reduces the cost and complexity historically associated with pressurebased systems, while providing increased control functionality. An essential objective of the work was to develop robust, computationally efficient algorithms that do not require highly accurate or absolute measures of cylinder pressure. Pressure-Ratio-Management was presented and the ratio of fired-to-motored pressure was established as a means to efficiently estimate combustion phasing and mixture dilution for each cycle.
A non-intrusive cylinder pressure sensor that satisfies PRM requirements was conceived and developed. The sensor uses piezoelectric sensing technology to detect compressive forces in the spark plug boss of four-valveper-cylinder engines in response to cylinder pressure. The sensor incorporates a linear piezoceramic material and a high-temperature integral electronic amplifier. A single wire connected to the sensor provides a constant current to the amplifier and returns a voltage signal to an electrical interface at the engine controller. The sensor system has potentially excellent durability with estimated cost between one half to one quarter that of competitive intrusive sensors.
The control system has potential to measure trapped air in each cylinder using cylinder pressure measurements. Possibly, the air meter may be eliminated and system cost further reduced. Additional work is needed to develop this functionality. Although the system has been applied to conventional S.I. engines in this work, extension to the common-rail diesel, direct-injection gasoline, and homogeneous-charge compression ignition engines may enable combustion control for these engines as well.
04-15-2005, 03:34 PM
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Leaftye,
That is a very good article. I came across that link about a year ago, and haven't seen anything as detailed since.
Here are a couple more links of interest:
http://zhome.com/ZCMnL/PICS/detonation/detonation.html
http://www.avweb.com/news/columns/182132-1.html
That is a very good article. I came across that link about a year ago, and haven't seen anything as detailed since.
Here are a couple more links of interest:
http://zhome.com/ZCMnL/PICS/detonation/detonation.html
http://www.avweb.com/news/columns/182132-1.html
Last edited by Adrenaline_Z; 04-15-2005 at 04:55 PM.
04-15-2005, 11:20 PM
#57
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Back in 2002, I had a ARE 422ci engine and we tried 4-5 different peak timing settings. We started at 25 and went up to 32. Best was about 28, but 28 only made like 2rwhp more than 25. We put it back to 25. It was an 11.5:1 motor with a lot of overlap at .050.
I need to reread some of the stuff in this thread when I have time.
I need to reread some of the stuff in this thread when I have time.
04-17-2005, 09:17 PM
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Originally Posted by Adrenaline_Z
Why did you cut timing back to 25 degrees, if 28 gave you more power?
Curious.
Curious.
04-17-2005, 09:34 PM
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If it's making more power, it's not knocking.
Detonation would drop power. If the power peak and detonation points are
that close for timing, there's something wrong with the motor.
There is a window of timing advance after best power before detonation occurs.
Detonation would drop power. If the power peak and detonation points are
that close for timing, there's something wrong with the motor.
There is a window of timing advance after best power before detonation occurs.