It came to my attention that If only a small ammount of O2 remains unburned to give an o2 sensor reading, what happens when we put in cams with lots of overlap? Won't our sensors read leaner than we are? So we may be burning at 11:1 AFR but our AFR in our exhaust may be 13:1? Does anyone have any more information about this? I would think this would make a significant difference in o2 sensor readings.

 

bump for more info.

 

Also, since we are on the topic, how does an o2 sensor really know the AF ratio? if you are at 14.7:1, it should have enough fuel to combine all the o2 into co2, right? So how does read anything richer than 14.7:1?

 

bump.

 

another one

 

damn, no one even answered yet... bump for some info.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by gsrious &raquo;</TD></TR><TR><TD CLASS="quote">damn, no one even answered yet... bump for some info.</TD></TR></TABLE>



...and another one

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Cyphear &raquo;</TD></TR><TR><TD CLASS="quote">what happens when we put in cams with lots of overlap? Won't our sensors read leaner than we are? </TD></TR></TABLE>

The sensor would read richer than actual conditions, and lean out the combustion. Although at wide open throttle isn't the 02 sensor in closed loop, and does not collect info from the sensor?

 

Kinda funny this came up. A freind recently had a motor go down due to overlap. All the gauges and meter used checked fine. Including EGTs. As of not I do not know that there was any way to resolve it.

It was actually like this.... it began to generate heat due to pre-detonation. Because of all this going on the in cylinder chamber... the freash air from the intake side was actually directed out throught the exh valves to some degree. Thus the reason everything apeared fine.

 

yes, some info already... come on you engine builders and tuner... don't be shy.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MK3NORTH &raquo;</TD></TR><TR><TD CLASS="quote">

The sensor would read richer than actual conditions, and lean out the combustion. Although at wide open throttle isn't the 02 sensor in closed loop, and does not collect info from the sensor?</TD></TR></TABLE>

no, it'd read leaner. Yes, at WOT it wouldn't effect the "tune" since it'd be in open loop.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Cyphear &raquo;</TD></TR><TR><TD CLASS="quote">It came to my attention that If only a small ammount of O2 remains unburned to give an o2 sensor reading, what happens when we put in cams with lots of overlap? Won't our sensors read leaner than we are? So we may be burning at 11:1 AFR but our AFR in our exhaust may be 13:1? Does anyone have any more information about this? I would think this would make a significant difference in o2 sensor readings.</TD></TR></TABLE>

I look at it like this ...at the end of EX stroke- first the exh valves open BTDC (gases exit for 02 snsr to decide the afr) followed open by the intakes still BTDC (during this period the fresh charge- pure 02 will flow out ouf the exhaust as u mentioned but after the burnt gasses have left) and both IN/EX stay open a little ATDC on the intake stroke to create a momentum to help draw in fresh air. but it is interesting to see if overlap does have any effect to make the o2 see the afr leaner than it actually is during combustion, i can see where you coming from .

 

one last bump before I let this one die...

bump for mechanical engineers that are avoiding finals.