APEXi PFC + Setting Ignition Timing ?

[JasonO]

Hi Guys,

I've been checking the base timing on my RB25DET with a digital timing light.

After adjusting the CAS to display a very accurate 15 degrees against the marks on the crank pulley, I checked the Commander IGN monitor and found that the PFC was saying 18-20 degrees.

What causes this, and which should I be adjusting the CAS to agree with the Crank pulley or the PFC ?

Can sopmeone confirm the basic method of doing this, rpm's etc. so I know I'm not doing it wrong.

[Craved]

how are you checking the timing -- from the marks on the harmonic balancer? which mark is the timing at?

[JasonO]

Craved,

I set the gun to 15degrees, then adjusted the CAS so the first mark (the redish one) on the crank pulley (harmonic balancer) lined up with the mark on the lower timing belt cover.

If you were looking into the engine bay, stright down on the pulley, then it was the first mark clockwise.

ie. The one with the asterix on it

*

|__|__|__|__|__|

-------> Direction of Rotation.

My idle RPM at the time was abt 800rpm, is this too fast ?

How do I get the PFC to agree with what I see on the timing gun ?

[Craved]

what if you tried setting the gun to 0, then using the timing marks on the harmonic balancer to see if it show the 18-20 degrees.. perhaps the guns out!!

should be around 4th notch if my memory is working at 3:30am

[Kane Bodiam]

to get true top dead centre, drop number 1 spark plug out, check that it is on compression stroke, bring the piston all the way to the top, making sure it doesnt start its next stroke, at top dead centre see were the timing mark is at as your harmonic balancer might of slipped

[JasonO]

to get true top dead centre, drop number 1 spark plug out, check that it is on compression stroke, bring the piston all the way to the top, making sure it doesnt start its next stroke,  at top dead centre see were the timing mark is at as your harmonic balancer might of slipped

How can the harmonic balancer slip if it's keyed on the Crank ?

Where will the timing mark be if everything is OK ?

[Craved]

the harmonic balancer is keyed so it cannot slip!!

although the gears up top may not be lined up properly.. take the cam cover off and see if the marks on the cam gears are lined up on both sides when the HB is at 0 or TDC!!!

[Craved]

beat me to that one jason! as i said the cam gears may be off...

[JasonO]

The cam gears are spot on, I checked them several times at assembly, and have them checked again since. Everything lines up as it should.

The only problem I have is the PFC doesn't agree with the timing light......

[The Alchemist]

what I did is set my PFC ignition settings around the idle zones to 20 degrees (GTR) so the PFC has to be giving me 20 degrees regardless then set the timing using a timing light, in the manner you described, until it reads 20 degrees...easy....

or are you describing the PFC display screen showing a timing figure changing by itself between the 18 to 20 degrees....despite that fact you have the map set at 15 in the idle zone(s)...?....

I have noticed my GTR doing exactly that during warm up mode....is your engine fully warmed Engine temp over 70 degrees C when you set the timing?

[Sydneykid]

I have yet to find an accurate retard on a timing light, 2 to 3 degrees is not unusual.

[JasonO]

I have yet to find an accurate retard on a timing light

Oi, I try to be accurate

Hmmm Intresting........I can't get my engine temp over 70 degrees at idle.

I have an N1 water pump and thermostat fitted, and it idles at about 68-70º, only ever gets over 80 degrees at the end of the 1/4, or after a sustained high speed run.

[Sydneykid]

Oi, I try to be accurate

Hmmm Intresting........I can't get my engine temp over 70 degrees at idle.

I have an N1 water pump and thermostat fitted, and it idles at about 68-70º, only ever gets over 80 degrees at the end of the 1/4, or after a sustained high speed run.

Thermostat?

[JasonO]

Sorry not an N1 thermostat, but a NISMO low temp thermostat, IIRC it opens at 62ºC rather than 76.5ºC that the stock thermostat opens.

[Sydneykid]

Sorry not an N1 thermostat, but a NISMO low temp thermostat, IIRC it opens at 62ºC rather than 76.5ºC that the stock thermostat opens.

And that is why it won't go over 70 degrees, the thermostat is opening. :uh-huh:

Plus it is summer time in Scotland, if it was winter the water would be frozen anyway. :jk:

[JasonO]

SK, I've sked before elsewhere about the engine temp, maybe you can answer this one.

The PFC has a Water Temp Correction, Cranking Time Correction, and several other corrections applied below 80ºC which is the normal running temp.

Will my engines lower running temp bring these into play, or can I disregard them as the temperature difference is minimal ?

[JasonO]

SK, You ignoring me, or have I found one you can't answer

Incidentally, The soution to the ignition timing problem required some lateral thinking.

The PFC only shows what it's own IGN Map timing is, it has no way of knowing what the actual timing is as set ont he crank pulley. So, assuming eveything is correctly setup the way forward is to adjust the static timing to match that which is displayed on the PFC. This way what the PFC outputs is relevant to the actual timing on the engine.

So, to answer my original question for future referance.......

The CAS should be adjusted so that the static timing as measured against the crank pulley (harmonic balancer) matches that displayed on the PFC, at idle.

[Sydneykid]

SK, I've sked before elsewhere about the engine temp, maybe you can answer this one.

The PFC has a Water Temp Correction, Cranking Time Correction, and several other corrections applied below 80ºC which is the normal running temp.

Will my engines lower running temp bring these into play, or can I disregard them as the temperature difference is minimal ?

Yes, you lose power under 80 degrees.

[Sydneykid]

SK, You ignoring me, or have I found one you can't answer

Sorry, I was asleep.

[ylwgtr2]

I cut and pasted this from another thread that i contributed to....could be use ful just to make sure you get the pulley in the right spot,and ofcourse to fix those people up that think the pulley cant move or be out of position

First of all to be anal you would want to make sure the crank pulley is accurate(of which it will not be)To do this put a degree wheel on the front and line the "0" up to the original TDC mark,then get an old sparkplug with the guts taken out and a bolt welded in it(make sure it hangs out an inch or so)Put the piston down at BDC and screw the modded sparkplug in.Turn your engine clockwise untill the piston hits the plug.Write down the figure on the degree wheel,then go anticlockwise and write that figure down.Then after work out the half way point from the two figures you got and move the wheel to that point......Now you have your True TDC stamp the front pully with a chisel(however this possition may change after time,so i like to scribe the mark down onto the centre of the pulley and check it out now and then)My pulley was out about 3 degrees or so....I have never seen one thats right!