Bruce
01-14-2004, 03:47 PM
Plug the hose and your done.
I mean you've disabled it, so it can't work, so now you don't need to worry about it do you?, or do you?.
Just in brief review, the EGR valve allows some exhaust gases to be admitted into the intake manifold. By doing this they limit the amount of O2 present in the intake charge, as well as introduce gases that have been already thru the combustion process. This lowers the max possible chamber temperatures, and thus lower the amount of NOX that can be produced.
Some points to consider,
With the vacuum line off, the valve stops working, right?.
Well, not always.
The EGR spring does lose some of it's tension over time, and depending on the boost your running, and exhaust system, Backpressure can force it open. Hmm, so then you wind up with EGR at the higher boost levels.
Unlike the newer ecm codes there is no added timing for when EGR is present. It's already incorporated in the existing spark table. Being's that EGR reacts rather poorly, extra timing is needed when EGR is in use. Take the EGR away, and then you have a calibration running more then optimum timing.
With a NB (Narrow Band) O2 sensor, timing slightly effects the O2 content that the O2 reacts to. While this may sound slighthly out of line the NB O2s are slightly sensitive to CO2, and HC, so at TIMES you can get to add things happening. Not to mention they are EGT sensitive.
So while you can get close in getting the AFRs right to really get them correct you'll really want to use a WB (Wide Band) O2 sensor.
For details on the actual NB O2s responding to other then O2 all I can say for the time being was there was a lenghtly discussion about this on the DIY-EFI list and if it ever fully recovers, you can read thru the archives there for the specifics. It was mostly from a CARB report.
Also, by now not running continual exhaust gas thru the intake manifold the manifold will be cooler. On the Syclones, it's been noted that the MAT drop can be 30-60dF. Which is automaticlly good, right?. Well, not completely. The process of vaporization, can/does alot for evening out the fuel distribution. During the overlap event (both valves open), the fuel laying around the runner's floor gets hit with a VIOLENT blast of exhaust gases for a moment. This ATOMIZES, slightly vaporizes, the fuel there, AND blows some back on to the plenum floor. Normally with the plenum floor being heated by the EGR passage way that fuel is then vaporized, and then the next inhaling cylinder get some nice vaporized fuel, from that process.
So, you want to disable the EGR, CORRECTLY?.
You first remove the valve, and bolt on a plate.
You drop 3-4d of timing in the low load areas of the chip (non-idle).
Then redo your fuel curve accordingly.
The above is for off-road, and racing purposes only, ie not to be confused with achieving lean cruise or improving MPG.
I mean you've disabled it, so it can't work, so now you don't need to worry about it do you?, or do you?.
Just in brief review, the EGR valve allows some exhaust gases to be admitted into the intake manifold. By doing this they limit the amount of O2 present in the intake charge, as well as introduce gases that have been already thru the combustion process. This lowers the max possible chamber temperatures, and thus lower the amount of NOX that can be produced.
Some points to consider,
With the vacuum line off, the valve stops working, right?.
Well, not always.
The EGR spring does lose some of it's tension over time, and depending on the boost your running, and exhaust system, Backpressure can force it open. Hmm, so then you wind up with EGR at the higher boost levels.
Unlike the newer ecm codes there is no added timing for when EGR is present. It's already incorporated in the existing spark table. Being's that EGR reacts rather poorly, extra timing is needed when EGR is in use. Take the EGR away, and then you have a calibration running more then optimum timing.
With a NB (Narrow Band) O2 sensor, timing slightly effects the O2 content that the O2 reacts to. While this may sound slighthly out of line the NB O2s are slightly sensitive to CO2, and HC, so at TIMES you can get to add things happening. Not to mention they are EGT sensitive.
So while you can get close in getting the AFRs right to really get them correct you'll really want to use a WB (Wide Band) O2 sensor.
For details on the actual NB O2s responding to other then O2 all I can say for the time being was there was a lenghtly discussion about this on the DIY-EFI list and if it ever fully recovers, you can read thru the archives there for the specifics. It was mostly from a CARB report.
Also, by now not running continual exhaust gas thru the intake manifold the manifold will be cooler. On the Syclones, it's been noted that the MAT drop can be 30-60dF. Which is automaticlly good, right?. Well, not completely. The process of vaporization, can/does alot for evening out the fuel distribution. During the overlap event (both valves open), the fuel laying around the runner's floor gets hit with a VIOLENT blast of exhaust gases for a moment. This ATOMIZES, slightly vaporizes, the fuel there, AND blows some back on to the plenum floor. Normally with the plenum floor being heated by the EGR passage way that fuel is then vaporized, and then the next inhaling cylinder get some nice vaporized fuel, from that process.
So, you want to disable the EGR, CORRECTLY?.
You first remove the valve, and bolt on a plate.
You drop 3-4d of timing in the low load areas of the chip (non-idle).
Then redo your fuel curve accordingly.
The above is for off-road, and racing purposes only, ie not to be confused with achieving lean cruise or improving MPG.