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Originally Posted by hsitko
Firstly, having exhaust in the combustion chamber does not mean it will displace oxygen and fuel.
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Absolutely it means that air and fuel are displaced.
Quote:
Originally Posted by hsitko
Like i said a compression ratio is only a best case scenario. VERY BEST CASE.
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I'm not sure how you are relating compression ratio and un-evacuated exhaust from the chamber. Neither static, nor dynamnic compression, or compression measured in any other way will be changed or affected by exhaust being left in or fully expelled from the chamber.
Quote:
Originally Posted by hsitko
It is truthfully dependent on a lot of things. So keep in mind that when your engine is running its not running to its full potential almost ever..
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I agree with this. Aside from WOT your engine is constantly being starved of air/fuel mixture by the throttle plate. And even at WOT there's likely only a small sliver of RPM rev range in which you're engine will attempt to reach 100% VE. In reality it will probably be something less than 100%.
Quote:
Originally Posted by hsitko
So having some exhaust in the chamber because of high back pressure means one thing basically. A leaner mixture in certain rpm ranges.
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This is where you lose me. I believe that your theory on this is flawed. Your mixture could not possibly be leaner with additional exhaust in the chamber. Exhaust has had it's oxygen used up already and is inert, cannot be burnt anymore. Therefore, if there was additional exhaust in the chamber that was not scavenged because, lets say, your RPMs were too low or too high this would be metered either by your MAF system or it would have been programmed into the ROM to your speed density system's VE map lookup table by a calibration engineer at the OEM in question. Either way, exhaust left in the chamber is simply one of they many ways in which VE does not equal 100%
Quote:
Originally Posted by hsitko
You do know what a leaner mixture will do right? It will increase torque
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Actually from my tuning experiences with a wideband, I find that an AFR of just under 13.0:1 (12.8:1 - 12.9:1) on gas creates the best torque from peak torque to peak HP, and then further richen after that for safety.
@6.5psi, I'm finding a lambda of about .85 from peak torque to peak HP feels good. In this case I'm on E85
These are my experiences with my KA, both N/A and turboed. When you say lean mixture, I'm not sure what you mean since you didn't add any points of reference to your story.
Quote:
Originally Posted by hsitko
This might be a different story if this car had a wideband stock that the ecu could add fuel with if it saw a leaner than normal mixture. But it cant.
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We are talking about WOT conditions here where VE is at peak for a given engine. Under these conditions a conventionl narrowband O2 sensor is disregarded and the ECU is running in open loop with an additional long term trim modifier added to the equation. In this case the ECU is running off of a target AFR table where values have been stored (again by a calibration engineer at a given OEM) as to how much fuel to add/modify by at a given load and rpm.
Quote:
Originally Posted by hsitko
It only reads grams per second of oxygen which will not change if you dont expel all your exhaust and run lean.
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From my experience our Nissan ECU's don't convert or scale to grams per second of air (not oxygen), fuel or any other . It's a more simple 8 bit or 16bit load value. However, for the record, I will comment on this. If you don't expel all of your exhaust, your VE will be lower than if you did. In this case, this would be metered by your MAF since less air is able to enter your engine.
Quote:
Originally Posted by hsitko
Keep in mind i'm not talking massively lean here. Only a little. And like i said. Its a small amount of torque and a small amount of horsepower i'm talking about here. Seriously less than 5 on average. An engine does not fill the combustion chamber to its maximum potential while the engine is running and thats a fact.
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Well we do agree that an engine rarely if ever hit 100% VE. I'll add that this is assuming WOT. From what I have read, forced induction will cause an engine to get closer to and possibly hit 100% or greater VE (greater than 100% would be completely unburnt, unused air/fuel mixture out the tailpipe).
OP, sorry for threadjacking. This will be my last post of this nature.