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Ignition Timing & Knock ?

gL3nJaMiN88

By gL3nJaMiN88,
in General Maintenance

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gL3nJaMiN88 Collaborator

gL3nJaMiN88

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hey guys i'm tryin to adjust my timing but no mechanic knows and i cant find anything on this website - or google for a fact and its starting to really get me annoyed .. My car is knocking and i wanna fix it .. So i've got a timing light and know how to use it on rb 25 but does anyone have any info on what line is what on the crank and what a medium modded skyline should be , also what is considered high knock and what is low knock on a skyline running powerfc ? I cant any info on that question either ? someone please help me before i go insane

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blind_elk Grand Master

blind_elk

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I'm sure there are dozens of threads that describe the marks on the crank pulley.

So, once again:

there are 7 marks on the pulley, each represents 5 degrees of crank rotation, and 1 mark on the timing case cover. As you look at the engine from front on, the timing marks "move" from left to right. The last mark is TDC.

Regardless of the level of mods, base timing should be 15BTDC. This then puts the "trigger" in the correct relative position to let the ECU calculate correctly when to fire the spark, based on what is programmed into the internal load maps.

My experience is that RB engines don't seem to respond all that well to ignition to alter detonation, they seem to respond much better to fuel adjustments. Depending on the age and condition of the engine, the knock the PFC is detecting may not necessarily be detonation, it could be noisy lifters, or maybe piston slap.

gL3nJaMiN88 Collaborator

gL3nJaMiN88

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ok this is the part that gets me all mixed up .. The PowerFC Is Reading 15* on idle and when i advance or retard the CAS the timing still reads 15* even if i adjust it all the way untill i cant anymore it still is reading 15* .. is timing also altered by powerFC or only the CAS .. Every mechanic i call wont help me over phone they want money before they can help me .. car isnt knocking at all now but it feels like someone has my handbrake up and has a shit idle and its set at 15* with on the crank with a TIMING LIGHT

mad082 Grand Master

mad082

Posted
Posted

yeah bubba is right. you can spin the CAS to any position and it won't alter what the ecu thinks the timing is, however if you chack it with a timing light it will show as being changed.

the reason the car feels sluggish is because the tune was done at a different base timing. it really comes down to why it was pinging to start with. it may have been a fuel issue causing the pinging rather than a timing issue. in which case backing off the timing is just a bandaid fix.

EdGTR Enthusiast

EdGTR

Posted
Posted

Ok guys I also have a pfc and having just read this thread how do you set the base timing? I think this is the next step, With a stock comp dont you hav to bridge out a connector or somthing but what do you do witha pfc? Do you have to check that the cell its in at idle is set to 15 degrees advance and then use the timing light on the crank.

Im a mechanic and have set timing on hundreds of efi cars but a pfc changes things a little. Ive never had to on my car so havnt looked into it but it is a good question.

Just be aware gl3n that if you dont know where you were when you started then it could well be a case of setting the base timing and then going back to the tuner to at least get it all checked.

blind_elk Grand Master

blind_elk

Posted
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how do you set the base timing?

RTFM, perhaps?

I suspect it is a matter of setting the idle timing in the PFC, then while checking timing with a timing light adjust the CAS until the timing light gives the same value as you have programmed in the PFC.

With a stock ECU, it is simply a matter of checking with the timing light because you know that the ECU is programmed for 15BTDC @ idle.

EdGTR Enthusiast

EdGTR

Posted
Posted

Yeah fair call, I did read it and yes you just point and shoot. The only other thing that it says to do is attach the timing light pick up to the loop near the igniter and if you are not sure which way try both and the correct one the timing will have less advance. So make sure the pfc is reading 15 degrees and hook up the timing light and adjust the base until it says 15 and you should be done. If it still feels sluggish its back to a tuner or try and see if there are any marks where the bolt were before you first touched it but as the weather is getting hotter it will want to knock more so better to be safe

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