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Igntion timing for VTEC


Mindfreakattack

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Hi, have some qjestion regarding VTEC tuning.

1. may i ask if the ignition timing is normally retarded or advanced when the engine cross into VTEC? I just got a Honda civic with a B16A (updgraded with B16B internals) in it.. downloaded the map and realised the ignition map seems to be 5-8deg more retarded in VTEC than in Low cam. Was thinking it should be advancing timing since the engine is higher in rpm.. would want to have the timing advanced to support combustion. 

2. My Current map is set to switch between ignition tables 1 and 2 during VTEC engagement. Ive seen maps where there is only 1 table for ign. In this case, whether u r in vtec or not, we are using that table's timing correct? If this is correct, why would anyone want to do this? Pure simplicity of tune? 

 

 

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  1. When the Vtec is engaged at the correct RPM, the VE will increase.  That means there is more air and fuel in the cylinder, and cylinder pressure during combustion will increase more.  The flame front can travel faster through the more densely packed mixture so generally the ignition would need less advance with higher cylinder pressure.  
  2. With two separate tables it means you can change the VTEC switch point later without having to re-tune it.  I dont usually bother, I finish the tune after I have already found the best switch point and it generally wont be changed.  
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2 hours ago, Adamw said:
  1. When the Vtec is engaged at the correct RPM, the VE will increase.  That means there is more air and fuel in the cylinder, and cylinder pressure during combustion will increase more.  The flame front can travel faster through the more densely packed mixture so generally the ignition would need less advance with higher cylinder pressure.  
  2. With two separate tables it means you can change the VTEC switch point later without having to re-tune it.  I dont usually bother, I finish the tune after I have already found the best switch point and it generally wont be changed.  

Thank you very much Adam.. :) understood. Thanks for the very clear explaination!!

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