You know Billy, your approach is neither well written nor accurate. You have a choice:
- Read what I have to say, based on this:
- Or, continue to rationalize what you have done based on speculation.
I do "have a solid grasp on the air metering and the fueling requirements of EGR operation"
Point 1 - You have said a couple times now the VPC output to the TCCS does not matter...it's not the issue. Hate to tell you this but it's a major part of the issue. A VPC outputs the same type signal (square wave...increasing frequency) as the Karman Vortex AFM...the frequency is generated in the VPC based primarily on AIT, intake manifold pressure and RPM. It's still a square wave signal and is interpreted the same way by the TCCS. The VPC "fools" the TCCS by increasing/decreasing the output signal frequency (Vs) to increase/decrease basic injector duration primarily via the gain knob...the initial throttle response knob affects VTA. Regardless of what you said, you are "lying" to the TCCS with a modified/generated signal.
Point 2 - Power Enrichment occurs under heavy engine load...the relevant signals are:
- Throttle position (VTA)
- Intake air volume (Vs)
- Engine Speed (Ne)
- Coolant Temp (THW)
The VPC affect two of these signals (VTA and Vs), but not engine speed or THW. The TCCS will calculate injector volume for power enrichment in the 10-30% range. This is an important point,
Power Enrichment will cause the TCCS to go into open-loop...AFR feedback is inop during open-loop. The AFR correction coefficient is 1.0 during Power Enrichment...the TCCS does not react to the O2 sensor. Therefore, no adjustment for an initial lean AFR...your "explosion detectors" (knock sensors) are your last defense to detonation.
Point 3 - The EGR is inop at idle up to ~4000 RPM (actually 4000 to 4500). The volume of exhaust gas supplied to the EGR is a ratio (not a percentage) based on exhaust manifold pressure as it relates to intake manifold pressure (or vacuum). On the GTE motor, the vacuum modulator controls the volume based on exhaust gas pressure vs vacuum/boost. The GE motor requires an additional vac line to effect EGR flow at low power settings in the same manner when exhaust pressure is low...once exhaust pressure is high, EGR gas is delivered regardless (thanks JJ). EGR piping is a set size...it will only flow a set amount of exhaust gas limited by the vacuum modulator. The bottom line here is exhaust gas present in the cylinders changes based on exhaust pressure...it is not a set percentage of cylinder volume.
Point 4 - The TCCS (without piggyback inputs) is tuned for the EGR both for fuel and timing. When the EGR is active, exhaust gas displaces air in the cylinders per the ratio above...this is less O2 available for combustion, therefore requiring less fuel. This is why the EGR will help with gas mileage. If you introduce more air (i.e. no EGR), the TCCS will react in closed-loop using an AFR correction coefficient of 0.8 to 1.2...since the additional air causes a lean condition, the TCCS will add fuel over time and set the value in learned memory. Basic timing is not affected though...capacity of ECU memory is limited and cannot hold all possible advance angle data. The TCCS selects values from the timing table closest to engine speed and intake air volume and calculates corrective values limited to a minimum of -10 to 0 deg and maximum advance of 35-45 deg . One of these corrective values is EGR flow...again to allow more efficient engine operation due to the resistance to detonation the EGR provides.
Point 5 - It's not the EGR that causes tuning problems, it's TCCS corrections to fuel and timing during closed-loop and the resulting learned values. The learned values change both fuel and timing based on inputs from the AFM (or VPC) and O2 sensor...it attempts to correct AFR and timing to the "normal" value range for the engine.
Now, after reading all this,
I want to point out what I have said all along. For normal driving conditions, including high throttle runs under boost, removing the EGR will likely not cause a problem. Your gas mileage will suffer, but it's not likely you will detonate because the TCCS has time to compensate. Where you get into trouble is at a 3000 RPM cruise in closed-loop (especially with little learned value present in the ECU...i.e. after an ECU reset) and you hit an uphill grade. You downshift, the car goes into boost...power enrichment occurs, but the ECU is using open-loop values (fuel and timing) that assume the EGR is there. You detonate the motor.
Will this always happen...nope. Can you add fuel with a piggyback to minimize the effect...yep, but you will run rich at cruise and the TCCS will adjust fuel/timing in closed-loop and retain the learned values (that nasty piggyback tuning problem again). What ends up happening is you "tune" to the min/max correction values in the TCCS with the same signals used by a VPC...it is the nature of he beast when you basically "lie" to the ECU. It is not optimal. That is why you want to use a JDM TCCS to take the EGR out of the calculations...or, a full standalone.
Concerning the cost issues for those that have removed the EGR. Well, if they took the time to figure it out, they would not have removed it to begin with now would they
If someone finds themselves in this situation, it was self induced...the choice is to roll the dice or bite the bullet and incur the expense of putting it back on. The EGR causing "tuning problems" is simply not true...it was the TCCS causing the problem until you hit the max correction range. This is about as true as "the EGR cooler causing the #6 cylinder to get hot" statement made earlier in this thread. Supported by a guy who knows so little, it's hard to keep up with what he doesn't know
Concerning the guy with the AEM, I told him that the EGR would not be required...his response was:
SWD Fredester 3;1133619 said:
Thanks, mileage and clean air do matter and hopefully I'll be able to pass
emissions next year! I also have the parts so I might as well use them.
A very mature response, that was thought through from the beginning. Unlike what you're saying...cost is not an issue to me (and a lot of others) when it can put my motor at risk. And, the ability to save $3.70 per gallon gas is an issue, especially when it will likely get worse.
The EGR is not a rant and removing it is the real waste of money. It has zero effect on top HP produced and I can see no logical reason for removing it when using a stock TCCS.
