TDC Offset Angle range

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Shuriken
Posts: 9
Joined: Thu Jan 28, 2021 10:45 pm

TDC Offset Angle range

Postby Shuriken » Tue Mar 02, 2021 12:14 am

I'm in the tuning of my 3S-GTE now and I'm curious about the the TDC Offset Angle parameter.
When I set offset angle at the first start I used reference 365 degrees from here https://support.haltech.com/portal/en/k ... 3sg-engine. The engine was successfully starting and idling, lock mode at 10 deg perfectly "shots" to the value from the crank pulley (checked with a timing light). Then I decided to check TDC with the timing light at revving and noticed that mark was drifting significantly from the 10 deg position, So, I subtracted 360 degrees, set the TDC Offset Angle to 5 deg, and checked timing. Everything is ok, the mark was stabilized at 10 deg on revving. The engine works ok, I've already driven 500 km, but...
Yesterday I read the next thing (from here https://fullspeedtech.com/info/?p=33):
"Keep in mind 2 things though – (1) even a keyed, consistent crank wheel is independent of engine stroke, so you could be off by 360°, and (2) whatever you do you want the TDC Offset value to be larger than the largest advance angle you plan to run (for a 2nd/3rd gen 3SGTE I want the TDC offset angle to always be 55° or more). Hint: if your value works out to under your target max advance, use (720 – value) instead." :roll:
I don't understand why the bolded requirement is needed. It turns out that I incorrectly set the TDC Offset Angle and it should be (how much?) 720-5 = 715 deg?

Thanks a lot!

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