Knock Control..

91 XR7

Registered User
I tried searching, but couldn't find it?

But while driving around in my '91 SC today (first time since owning it) I believe i was hearing Knock/Pinging but rarely and usually only on the 2nd to 3rd shift? under mild acceleration, also could get it on the odd time when either in 2nd or 3rd and getting on it pretty good.. but only there for like a Second at the most..

But it got me wondering on how the EEC controls Knock.. DUH retards the timing, like no ..... But does the EEC just retard the timing as long as the knock sensor is sensing knock and then comes back fully? OR does it take awhile for the EEC to add that timing back after the knock sensor doesn't register knock??

Thanks
 
Sounds like your talking about spark knock, I also noticed loud spark knock on my 93 sc. Im change the plugs and wires today for other reasons but I would look into that.

Jerry
 
The eec senses boost and pulls timing on a preset table.
If knock is sensed the eec pulls even more timing until no more knock is detected.
There is never full timing under boost like an N/A engine would have,there must always be timing removed when in boost.
 
The EEC pulls back timing up to a certain point and holds that until knock is no longer heard and then adds it back it. If you are hearing knock then it remains that a) your knock sensor does not work, or 2) you have a condition such that your motor is generating such severe knock that the EEC cannot control it by removing timing.
 
1st, I know the EEC retards the timing compared to Boost/load calculation (i'm thinking this is how since their is no MAP sensor? :) ) and i on my car persay.. since it's only there for a split second, i say the knock sensor is working and whatever timing it pulls is doing it's job... OH and i am running 94 octane (at $1.60/liter @$5.80us/Gallon) so..

So the EEC pulls the timing in one go, or Gradually untill the knock is gone?

IE: If there is a totall of 6 degrees of Retard for the knock control, it Pulls it all or does it first start off with 2degrees, and if that doesn't help it does another 2, and then the last 2??

And it Gives back all the Advance once the knock is gone?

Where i work, we had a Engine made up (Semi hi-pro) that had Knock control, and the Guy who made up the engine/EFI said the Knock control retards the timing 3 degrees at a time for a total of 6 degrees, and once there is no more knock it will Slowly add back in that timing 1-2 degrees at a time over a certain amount of time (like 1-2 degrees a minute?) which got me thinking of How the EEC in the SC controlled knock...

But i do plan on a Full tune up (since i have no idea the history of this car, Mind you i could ask the service rep at Ford, was alway serviced there) which would include Plug wires, plugs, Fuel Filter, PCV, Oil and FIlter, MAYBE O2 sensors... Already sent through 2 bottles of `injector Cleaner' (at only 1/2 a tank, hey it worked on my '89 XR7 when i got a `injectors out of Balanced' code :) )

Mind you there is another EEC related question i have... But i'll hijack my own thread later :p
 
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As soon as knock is detected the EEC will pull the full amount its set up for, which in the 89-90 is 8 degrees. After a preset amount of succesful revolutions with no knock the retard is completely removed.

The EEC knows nothing about how much boost you are making. It only knows how much air is going into the motor which is used to calculate load. In the 89-93 cars, spark is basically based on Load and RPM, but once it goes into WOT mode, spark then comes from RPM only (just the basics of it).
In the 94-95 cars Spark comes basically comes from Load and RPM at all times which a whole wack more tables to determine the ending spark.

Frit
 
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