Originally Posted by ShawnQ
That's the way I read it...and I'm not disagreeing with him (HDDP) at all, just curious if that is how he meant it.
It seems like the car would adjust to minor air increases...it definitely feels like it runs much better when it is colder (dense air = more of it).
SQ
No, That's not quite what I meant, but that's probably because of the way I wrote it... What I meant is that the ECU will do everything in it's power to a maintain stoichiometric state... Which is 14.7:1...
As everbody knows, an internal combustion engine should produce its maximum / optimum HP betwween 12.5:1 to 13.2:1 AFR with a lambda of 0.85... But since the OEM ECU will always try to force this engine to maintain 14.7:1, even if you introduce more air, or more gas into the system, your HP gains will probably be much less than if you just adjusted (tuned) the ECU to optimize the air / fuel to the stock set-up...
Please don't get me wrong guys... this engine WILL benfit from various mods, but it won't develop the HP expected unless you tune it to specific changes... And keep the AFR somewhere in the 13 range...
As far as the previous post stating that the AFR was running at 11:1 under full throttle, I can't discount that fact... (running very rich) I've done many dyno's before and they are usually done full RPM for only a few seconds , which means you MASH the pedal for a few seconds to get a reading at redline... This usually produces a "rich" AFR like 11:1 because you've just stuffed a ton of gas into the cylinders without adding the approriate air... My guess is that if you had maintained that RPM for a minute or so, you would have rapidly seen the AFR go back to the mid 14 range as the ECU adjusted the injectors, timing, etc...
I know I have belabored this point to death, but if you really want to see what happens with this OEM engine when fuel or air is added, you have to monitor the AFR and timing simultaneously... You'll be surprised to see how the ECU adjust things...