This is going to sound stupid. Please entertain me.
I ohmed my knock sensors and got no reading, which explains why this Q has less top-end power than my last -- the ECU decided to retard timing.
Since timing has been retarded and the knock sensors aren't functioning, does this mean I should be running a lower-octane fuel?
Knock sensors, octane
-
Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: Knock sensors, octane (Jesda)
The main purpose of premium is to get a higher quality fuel.........octane is just a part of that. Detergent and gum levels are added considerations.
The use of ethanol to make regular into premium doesn't count as a quality enhancement.
The use of ethanol to make regular into premium doesn't count as a quality enhancement.
-
Q45tech
- Moderator
- Posts: 14296
- Joined: Tue Apr 30, 2002 3:19 am
- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Re: (Jesda)
Retarded is confusing some.......................the total advance is the SUM of the initial advance [set by CAS] plus a group of individual cell locations.
The maximum advance is like 40 BTDC at cruise and 26-28 BTDC at WOT above 6500 rpm.
The KS circuitry is not smart enough or fast enough to operate much above 4500 rpm .
THE KS may add anywhere from 0 to 12 degrees so retard is not really the correct word....................less than normal is a better explanation.
At WOT the KS is pretty much ignored and the ROM takes over to supply the advance.
The ecu test KS system during idling for signals and proper resistance.
If resistance is not correct it throw s a code if signaling is not correct it set a midpoint [the regular fuel chart say a 3-6 degree decrease from full 12 degree advance.............it still listens for knock and will still decrease more if it hears any .....................most simple knock occurs 1500-2500 rpm during sudden more throttle open transitions..............when the cruise advance needs to drop from40 to 20 to accelerate.
The knock occurs because the throttle is manually opened and there is a delay between MAF and TPS resolution.
The maximum advance is like 40 BTDC at cruise and 26-28 BTDC at WOT above 6500 rpm.
The KS circuitry is not smart enough or fast enough to operate much above 4500 rpm .
THE KS may add anywhere from 0 to 12 degrees so retard is not really the correct word....................less than normal is a better explanation.
At WOT the KS is pretty much ignored and the ROM takes over to supply the advance.
The ecu test KS system during idling for signals and proper resistance.
If resistance is not correct it throw s a code if signaling is not correct it set a midpoint [the regular fuel chart say a 3-6 degree decrease from full 12 degree advance.............it still listens for knock and will still decrease more if it hears any .....................most simple knock occurs 1500-2500 rpm during sudden more throttle open transitions..............when the cruise advance needs to drop from40 to 20 to accelerate.
The knock occurs because the throttle is manually opened and there is a delay between MAF and TPS resolution.
-
ScottJackson
- Posts: 657
- Joined: Fri Mar 26, 2004 6:08 pm
- Car: 91 Q45, 92 Q45a, 93 Q45, 79 BMW 635CSi, 95 BMW 540i
Re: (ScottJackson)
i second that.................i think at 20k.......and hold it like for a couple seconds or so.ScottJackson wrote:Jesda, did you have your ohm meter set to the right position? I know it's basic, but if the dial isn't set on the right position, it'll read as the circuit being open.