I know this knock sensor thing has been beat to death but I have read all the post I can find about it & all I see is do not bypass or you will grenade your engine.My question is does this ks constantly monitor the system & take it just up to knock & then back off?If not I do not understand how it would damage the engine as long as you are not running the engine w/clatter in my experience all the ks does on most cars is retard if there is a knock outside of that it just runs it's preset curve.I am a mechanic by trade for over 20 years but I work on all makes more domestic than import but this Q I just traded for is a different breed I do like the way it drives & plan on keeping it.
Thanks again, Clint
Knock sensor again
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bullittandy
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Re: Knock sensor again (vmaxed69)
What do mean "bypass"?
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Q45tech
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Re: Knock sensor again (bullittandy)
Yes!, the knock sensor circuit constantly monitors the knock and inserts A NUMBER into the equation that adds/subtracts up to create a total number of degrees of advance. Just like coolant temp and air temp add or subtract values in the equation, just that the KS swings 3-4 times higher numeric depending on conditions.
When in fail safe a zero is inserted in it's numeric place in the equation.
The total advance might be 3-5-7 degrees less than optimum for cruise or acceleration......why the engine feels sluggish.
In summer heat gasoline usually knocks so even this 3-5 degrees is not anywhere near sufficient when the KS can remove 10=15 degrees to stop the knock.
You cannot hear knock with AC fan on high or radio on or windows closed.
At steady cruise advance might be 40 degrees and the very moment acceleration begins it might drop to 5 then ramp up to 20 [so called tip in retard to stop knock before it starts]. The rate of ramp up and exact number is controlled by KS circuit.
Prior to and during gear shifts the advance falls to zero then ramps back up to ~~ 20.................so lots od changes constantly going on.
"The ECU monitors the detonation sensor and processes the voltage information into a measurement called "knock counts". Knock counts are reported to dataloggers for the OBDI models (1991-1993) and for 1994-1995 models. For OBDII models (1996+) knock detection is not reported according to the OBDII protocol. When the ECU detects knock above 8 counts (18.75% of 43) and engine load is above the third "load row", it starts to retard timing. If the knock count increases, the ECU continues to reduce timing advance up to a maximum of 12 to 15 crank-angle degrees. If knock counts reduce or remain constant, the ECU can advance timing. The number of degrees the ECU increases or decreases the "knock delay" is based on what is called the "octane value" (the long-term timing advance trim) and another look-up table called the "delay map". Below a knock count of 3 the octane value is increased toward its maximum value, leading to less knock delay (more timing advance). If the knock count is above 5 the octane value is decreased toward its minimum value, leading to more knock delay (more timing retard). There is a fixed value in the ECU programming controlling how fast (step size) the octane value is increased or decreased. The octane value is reset to its maximum (no knock delay) when the ECU is reset (power removed for 15 seconds or so). "
From:http://www.stealth316.com/2-ignitionsystem.htm
When in fail safe a zero is inserted in it's numeric place in the equation.
The total advance might be 3-5-7 degrees less than optimum for cruise or acceleration......why the engine feels sluggish.
In summer heat gasoline usually knocks so even this 3-5 degrees is not anywhere near sufficient when the KS can remove 10=15 degrees to stop the knock.
You cannot hear knock with AC fan on high or radio on or windows closed.
At steady cruise advance might be 40 degrees and the very moment acceleration begins it might drop to 5 then ramp up to 20 [so called tip in retard to stop knock before it starts]. The rate of ramp up and exact number is controlled by KS circuit.
Prior to and during gear shifts the advance falls to zero then ramps back up to ~~ 20.................so lots od changes constantly going on.
"The ECU monitors the detonation sensor and processes the voltage information into a measurement called "knock counts". Knock counts are reported to dataloggers for the OBDI models (1991-1993) and for 1994-1995 models. For OBDII models (1996+) knock detection is not reported according to the OBDII protocol. When the ECU detects knock above 8 counts (18.75% of 43) and engine load is above the third "load row", it starts to retard timing. If the knock count increases, the ECU continues to reduce timing advance up to a maximum of 12 to 15 crank-angle degrees. If knock counts reduce or remain constant, the ECU can advance timing. The number of degrees the ECU increases or decreases the "knock delay" is based on what is called the "octane value" (the long-term timing advance trim) and another look-up table called the "delay map". Below a knock count of 3 the octane value is increased toward its maximum value, leading to less knock delay (more timing advance). If the knock count is above 5 the octane value is decreased toward its minimum value, leading to more knock delay (more timing retard). There is a fixed value in the ECU programming controlling how fast (step size) the octane value is increased or decreased. The octane value is reset to its maximum (no knock delay) when the ECU is reset (power removed for 15 seconds or so). "
From:http://www.stealth316.com/2-ignitionsystem.htm
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Q45tech
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1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: Knock sensor again (Q45tech)
It is more the inaudible constant low level knock's effect on rod bearing life that concerns engineers. Really bad knock will usually be noticed by most drivers.
Unfortunately you can fill up with defective gasoline and get back on interstate radio blaring at 80 mph you'll never hear the destructive clatter.
Knock sensors are extremely life threatening important with moded ECU because almost all the safety has been removed by advancing the timing way beyond factor specs under acceleration................even the best premiums will knock sometimes.
Unfortunately you can fill up with defective gasoline and get back on interstate radio blaring at 80 mph you'll never hear the destructive clatter.
Knock sensors are extremely life threatening important with moded ECU because almost all the safety has been removed by advancing the timing way beyond factor specs under acceleration................even the best premiums will knock sometimes.
Re: Knock sensor again (Q45tech)
qtech,so on a 96q- bad knock sensors affect performance more or less than on an obd1 q?
Obviously not recommended to bypass them but I have one of mine bypassed for the time being. I have the new ones already and they will go in as soon as I get a day to do my plenum job. I was having trouble with emissions with the bad one so I bypassed it to get by that. Definitely a huge difference if you are using stock or modded ECU's. On the dyno my NICO ECU gave me 70 more horsepower over the stock ECU when there was a knock code in the ECU. I'm not sure why Tech feels it is more important to have the knock working with the modded ECU tho because the knock map on the modded ECU is very mild (if not non existent). Says to me it doesn't change much even if the knock is bad. Possibly that you are more likely to get knock with a modded ECU if you get a bad batch of fuel.