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TIMING DIFFERENCES


Gary Mounsey
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Hi Guys, Bit of a weird one..... i swapped to the G4 plugin (for a rb25det S1 Skyline) from a original GTS-T LINK PLUGIN . Here's the only problem i found (aside from the Auto tps switch problem !) The base timing is set correctly on both of them, and on max power with the original GTST LINK, i was running 14 degrees. With the new G4 installed and timing zeroed, i ended up at 26 degrees full load (20psi) to get the same power ..... This freaked us out abit.... and we re-checked the timing many times with a few lights , incase the wastespark setup was throwing things out. So, can anyone tell me why this is so ? I can only think of something triggering of an opposite edge (falling to rising etc) to cause such a difference. I didn't hold the timing light on the crank when doing a run to verify it was 26 deg, as i didnt have a helper with me when i did the dyno. Asking on the skylines forum, another tuner said he noticed similar as well going from a POWER FC to the G4 ..... so i feel justified is asking on here ...... Gary

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This is nothing too scary... 

With the older (G1) ECUs timing numbers were on top of the base timing.  So, if your base timing was 12 degrees and you had 14 in the ECU the final timing value would be 26 degrees.

In G2 onwards ECUs the timing numbers are absolute.  The numbers you type in the table are what you will get on the crank (assuming you set base timing correctly).

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Hi Ashley. Hmm ok, that may explain it.. i have the G1 map but i think it won't display the timing area until connected so i cant check what the base was. I did find a problem though. I was setting the timing on the G4 via the timing loop (No.1 primary loop) , as most people would in an R33. However when timing it on weekend via a lead i had made up off the coil directly...... it was 11-12 degrees retarded , relative to the primary loop. I assume the wastespark is causing the confusion to the timing lights. Gary

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So you learnt the lesson that every good tuner has learnt once before...  The timing loop is bad and is only there for Nissan designed timing lights.  ALWAYS set the timing off a HT lead.  The timing off the HT lead will always be correct.

If you open your G1 file in old G1 PCLink (V2.5) the ignition table will be visible.  You will not be able to see what your offset was as it used to be set mechanically by altering the CAS position and twiddling the sub board dip switches.   That is why the numbers are relative not absolute in G4.

My suggestion is that you time your engine off no.1 HT lead to give a timing light reading of 10 degrees BTDC with the Lock Timing to Reference function tunred ON and the Reference Timing value set to 10.  Then the numbers in the table will be exactly what the engine is getting.  After that, re-tune ignition properly rather than trying to replace the numbers that your G1 used.  If you do not know what the G1s offset was then the G1 numbers are useless.

If you really want to use your G1 n umbers, plug it back in, set the advance limit to 0 then use a timing light (off no1 coil) see what the timing value is.  That is the G1 timing offset.  Add that to the numbers in your ignition table to get what the actual igntion timing was.  Note, the G1 offset number is NOT the same as the Timing Offset that you adjust in G4 so dont expect to type it in there!

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