Ignition Timing Advance or Retard The Why's and How's

[8541Hawk]

I think I still have a print out of the HRC map around here somewhere. I'll try to dig it up for you guys, if not I'll post up what I remember as even that might be a bit of a help for a good starting point

[8541Hawk]

Oh and good write up Carl

[freeridenick]

The above Diagram shows the Point of Valve Open and Closing times

I'm triple checking my cam timing before I button everything up and start it up. Am I right in thinking this diagram is a view from the right-hand side of the engine (clockwise rotation) but the degree valves would be from the left?

I other words from TDC on the compression stroke everything is closed. Next time round to TDC the exhaust valve has nearly closed and intake is just opening. At which point, and this is the important bit, if the above is the rear cylinder coming back to TDC on the exhaust stroke, the front cylinder is on its way up to TDC on the compression stroke.

Right?

[VTRDark]

Oh man that's getting the old eltrodes vibrating in my skull That diagram is one cylinder and does not matter which one or which stroke as they are all the same but at diffrent points of rotation on the camshaft. The outer circle is the Inlet valve and the Inner circle is the exhaust and rotation is clockwise. That diagram is a basic diagram that shows valve opening and closing times.

To work out Cam Timing and how one cylinder relates to another on diffrent strokes you need a more detailed graph. Something along the lines of the following:

Sample Image (note this is not a VTR)

Source

rear cylinder coming back to TDC on the exhaust stroke, the front cylinder is on its way up to TDC on the compression stroke

With the rear cylinder moving towrds TDC on the exhaust stroke the front wont be travelling in the same direction. The pistons are not travelling in sync with each other.



This thread is aimed more torwards Ignition Timing not Cam Timing and it's important to not confuse the two. I was going to do a thread on Cam Timing but never got around to it. That's a lot more complicated and would reguire degreeing and taking measurments of both inlet and exhaust cams to draw up a graph and then to try and explain things in technical and laymans terms.

[Mallebollia]

IGNITION TIMING
...
Ignition timing on the VTR 1000F as standard is set to fire the Spark Plug at 15° Before Top Dead Centre (BTDC) at idle as the Piston moves up on the Compression stroke and advances to 42° BTDC at 9,500 rpm.
...

How do you know that its 42°? Where did you get that inforamtion from?

[tony.mon]

IGNITION TIMING
...
Ignition timing on the VTR 1000F as standard is set to fire the Spark Plug at 15° Before Top Dead Centre (BTDC) at idle as the Piston moves up on the Compression stroke and advances to 42° BTDC at 9,500 rpm.
...

How do you know that its 42°? Where did you get that inforamtion from?

You can measure it easily enough by using a degree wheel and a strobe connected to the plug lead.