Diesel EGR Defeat

[jmcc]

Diesel engine controls don't add fuel when they're cold as a strategy, they put in whatever fuel is required to deliver the torque demanded by the driver/vehicle. So, cold start means more losses so to achieve the required torque more fuel is added. If the ECU detects a cold engine but in truth it isn't it will only add the fuel needed to run. Thd only problems you may have are if the idle speed setpoint is raised for cold conditions. Otherwise there will only ever be the right amount of fuel to run the engine.

For a diesel to overcome rough cold idle it would back out EGR ANC advance the timing. It might increase pilot injection and raise rail pressure, but it won't change main fuelling significantly.

This is in contrast to a gasoline engine which CAN alter the fuelling under cold conditions, generally to help cat light off. The gasoline engine will limit the air or retard the timing and lose efficiency.

FC = fuel consumption, sorry!

[Josh8loop]

Originally Posted by jmcc

Diesel engine controls don't add fuel when they're cold as a strategy, they put in whatever fuel is required to deliver the torque demanded by the driver/vehicle. So, cold start means more losses so to achieve the required torque more fuel is added. If the ECU detects a cold engine but in truth it isn't it will only add the fuel needed to run. Thd only problems you may have are if the idle speed setpoint is raised for cold conditions. Otherwise there will only ever be the right amount of fuel to run the engine.

For a diesel to overcome rough cold idle it would back out EGR ANC advance the timing. It might increase pilot injection and raise rail pressure, but it won't change main fuelling significantly.

This is in contrast to a gasoline engine which CAN alter the fuelling under cold conditions, generally to help cat light off. The gasoline engine will limit the air or retard the timing and lose efficiency.

FC = fuel consumption, sorry!

Check out some of this information on a modern diesel engine:

http://api.viglink.com/api/click?for...13324324882321



page 46 has some interesting information on start fuel quantity as it relates to cold conditions. There are also varoius other pages describing how the fueling system uses coolant temperature, fuel temperature, and intake air temp to control injected fuel volumes.


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[jmcc]

There isn't much in that document TBH, it mentions temperatures being used but not how.

FWIW I am a Diesel calibrator by profession so get the pleasure of reading the full OEM calibration documentation for a living!

[Josh8loop]

I've been eyeballing my car(2002 VW Jetta TDI) lately and thinking about this whole EGR delete thing. I had a working "Dynamic" EGR circuit up and running for my wifes 2005 E320 CDI but the EGR emmulation part of the circuit caused strange and erratic shift quality. Now that I know I have the "Dynamic" portion of the circuit down pat I just need to figure out how exactly I want to implement it on my TDI. I have options such as vacuum pressure switch on the N-18 output to the actuator, or perhaps use the relay to switch in the N-18 when cold and out when warm. Once operating temp is met, then a resistor can be substituted in place of the N-18 so the computer doesn't throw a code while the PWM signal can be sent to the EGR emmulator circuit to fool the MAF. There is also the MAF twist mod that may prevent a CEL light when the EGR is deleted too-some have had luck with this method.

[UFO]

I don't like the MAF twist method as it affects the MAF output across the entire load range, not just at idle where the EGR function is verified. It would be easy enough, given the temperature input, to switch the EGR in or out with a relay.

I hope I will have the opportunity to take another long road trip from Denver to Crestone. I got 51mpg on B100 with the EGR defeated. I may go again in late summer; if I do, I will re-connect the EGR and compare.

[Josh8loop]

Originally Posted by UFO

I don't like the MAF twist method as it affects the MAF output across the entire load range, not just at idle where the EGR function is verified. It would be easy enough, given the temperature input, to switch the EGR in or out with a relay.

I hope I will have the opportunity to take another long road trip from Denver to Crestone. I got 51mpg on B100 with the EGR defeated. I may go again in late summer; if I do, I will re-connect the EGR and compare.

I don't particularly like the MAF twist method either for those reasons. Although, for quick testing purposes it may be helpful. Did you incorporate a temperature dependent On-Off to your EGR delete? Are you noticing an increase in engine responsiveness from the EGR delete?


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[UFO]

I have not incorporated a temperature switch yet. As far as responsiveness, it seems just the same as with the EGR enabled. But I can sure tell a difference in response with the EGR disabled and the CEL set, I don't like it at all. I think it's the engine computer removing fuel timing in response to the EGR loss.

[Josh8loop]

Originally Posted by UFO

I have not incorporated a temperature switch yet. As far as responsiveness, it seems just the same as with the EGR enabled. But I can sure tell a difference in response with the EGR disabled and the CEL set, I don't like it at all. I think it's the engine computer removing fuel timing in response to the EGR loss.

So it sounds like you have just unplugged your N-18, or unplugged the vacuum line going to the EGR valve. I was thinking you had your EGR emmulator circuit in which should preclude any CEL's.

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[UFO]

Originally Posted by Josh8loop

So it sounds like you have just unplugged your N-18, or unplugged the vacuum line going to the EGR valve. I was thinking you had your EGR emmulator circuit in which should preclude any CEL's.

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No, I do have EGR emulated so I do not get CELs. I cannot tell the difference in drivability with EGR enabled or disabled, as long as the engine computer is fooled. I just have not designed in the temperature enable to kick out EGR when the engine is up to temperature. I'd like to incorporate that into my design before winter.

[Josh8loop]

Originally Posted by UFO

No, I do have EGR emulated so I do not get CELs. I cannot tell the difference in drivability with EGR enabled or disabled, as long as the engine computer is fooled. I just have not designed in the temperature enable to kick out EGR when the engine is up to temperature. I'd like to incorporate that into my design before winter.

Alright, gotcha. Some say that the ALH EGR system uses the ASV to help promote EGR flow into the engine by throttling it under certain circumstances. What has been your experience with this? not sure if I need to factor that into my emmulation scheme. Certainly don't want pumping losses increased from the ASV throttling!

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