cam timing vs. ignition timing
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From: Sugar Land, TX, USA
Re: cam timing vs. ignition timing (vspec12)
Just like it sounds
Cam timing affects how early or late the lobes open the valve.
Ignition timing affects how early or late the spark plug ignites.
Cam timing affects how early or late the lobes open the valve.
Ignition timing affects how early or late the spark plug ignites.
Honda-Tech Member
Joined: Mar 2001
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From: Where the streets have no, name., USA
Re: cam timing vs. ignition timing (vspec12)
The answer has multiple parts to it. I have never done either of these myself, but have an understanding of what is involved. For simplification, let's assume a DOHC engine: Ignition timing only afects when the spark is sent to the spark plugs relative to the intake cam's postion. Adjusting the cams (with cam gears) changes when each set of valves (Intake / Exhaust) are actuated in respect to each other and the pistons. Note below, that this also has an effect on the timing.
1) Ignition Timing is dependent on the intake cam for DOHC engines. [The only cam for SOHC engines.] That is because the distributor rotor is directly attached to the Intake cam. For every one rotation of the cam, the distributor also rotates 360 degrees.
2) Due to this, if you use a cam gear to advance the intake cam, you are also advancing the Ignition Timing. (because they are attached)
Therefore if you want to advance the intake cam (to increase overlap of the intake and exhaust cams) you will have to retard the Ignition Timing to maintain the same timing setting. Retarding the Intake Cam 2 degrees should be accompanied by 2 degrees Advance for the Ignition Timing.
Hot Rod magazine has a great article on cam timing. Just remember that Igntion Timing is relative to the Intake Cam in DOHC engines.
I hope something here is helpful.
WOTTEG
[Modified by WOTTEG, 1:46 PM 3/4/2002]
1) Ignition Timing is dependent on the intake cam for DOHC engines. [The only cam for SOHC engines.] That is because the distributor rotor is directly attached to the Intake cam. For every one rotation of the cam, the distributor also rotates 360 degrees.
2) Due to this, if you use a cam gear to advance the intake cam, you are also advancing the Ignition Timing. (because they are attached)
Therefore if you want to advance the intake cam (to increase overlap of the intake and exhaust cams) you will have to retard the Ignition Timing to maintain the same timing setting. Retarding the Intake Cam 2 degrees should be accompanied by 2 degrees Advance for the Ignition Timing.
Hot Rod magazine has a great article on cam timing. Just remember that Igntion Timing is relative to the Intake Cam in DOHC engines.
I hope something here is helpful.
WOTTEG
[Modified by WOTTEG, 1:46 PM 3/4/2002]
Honda-Tech Member
Joined: Jan 2000
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From: Woodbridge, NJ, USA
Re: cam timing vs. ignition timing (WOTTEG)
hello,
yes thats pretty much close, just couple corrections, +2 cam degrees typically mean +4 crank degrees for 1 mark on: AEM, Unorthodox, Skunk2, STR pulleys. fro 1 mark on JUN, its 4 degrees cam and 8 at crank.
second point, only on b-series is the intake cam driven with distributor, for h-series its the exhaust cam that drives distributor.
Thrid point, not all distributors are adjustable, some OBD2 H-series needs to be slotted in order to adjuts.
Greg
yes thats pretty much close, just couple corrections, +2 cam degrees typically mean +4 crank degrees for 1 mark on: AEM, Unorthodox, Skunk2, STR pulleys. fro 1 mark on JUN, its 4 degrees cam and 8 at crank.
second point, only on b-series is the intake cam driven with distributor, for h-series its the exhaust cam that drives distributor.
Thrid point, not all distributors are adjustable, some OBD2 H-series needs to be slotted in order to adjuts.
Greg
Joined: Nov 2001
Posts: 1,770
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From: Racine, WI, USA
Re: cam timing vs. ignition timing (1SlowSi)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1SlowSi »</TD></TR><TR><TD CLASS="quote">Just a question... when you advance the intake cam +3* or so, wouldnt the ECU automatically retard the ignition timing back to specs?</TD></TR></TABLE>
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