EGR experiment (Increase EGR flow for fuel economy)

[samwichse]

You might need to make this mod switchable from the driver's seat.

At least on Hondas, I believe right after start the ECM commands full open then full closed to the valve and sets whatever the wiper pot reads as full open/closed values... a sort of recalibration each time its started. If yours does something similar, you might need to splice in a switch to your resistor circuit so you can turn it on after starting.

[t vago]

Originally Posted by samwichse

You might need to make this mod switchable from the driver's seat.

At least on Hondas, I believe right after start the ECM commands full open then full closed to the valve and sets whatever the wiper pot reads as full open/closed values... a sort of recalibration each time its started. If yours does something similar, you might need to splice in a switch to your resistor circuit so you can turn it on after starting.

I've given it quite a bit of thought, and might end up putting in a toggle switch today or tomorrow. To be honest, I don't know if the engine computer only does a start-up recal, or if it continually monitors the sensor circuit for errors.

I have also bought an MPGuino, and will be installing that once it arrives. I'm not terribly trusting of my UltraGauge's MPG readout right now.

Also considering installing some sort of MAF sensor, and building a circuit to convert MAF to MAP. The increased EGR valve opening is causing MAP sensor readings to be somewhat higher than normal, causing the engine computer to pull back ignition timing, which would explain why my UltraGauge now reports spectacularly awful instantaneous MPG readings (11 MPG - 12 MPG) when I am slowly (<40 MPH) going up inclines. It used to report something along the lines of 18-20 MPG.

[t vago]

A few updates:

The UltraGauge did indeed show a highly inaccurate average fuel economy figure. As was mentioned in this post, one should not rely on a ScanGauge or UltraGauge for noting fuel economy due to this sort of mod. This leads to the next update...

The MPGuino should hopefully ship today. If so, I'll install it next week.

First fillup since I did the EGR sensor modification. The results are shown below:

Date/Time	Miles	EngRunTime	Gallons	AvgSpeed (MPH)	FE (MPG)	FE (L/100km)	%diff	Notes
2013.06.05 12:41	334.4	06:06	14.011	54.8	23.9	9.9
2013.06.09 16:19	337.9	07:02	14.333	48.0	23.6	10.0	-1.2
2013.06.13 01:48	398.7	07:13	15.415	55.3	25.9	9.1	7.7	+EGR Mod

I think that a 7.7% increase in fuel economy is not bad.

I'm still considering installing a MAF sensor, and creating a circuit that will obtain a MAP signal for the engine computer. However, I'm also considering moving my IAT sensor so that it will be before my intake heater. This should maybe provide what I want to do, which is to advance ignition timing. Remember, a higher-than-normal EGR will require that ignition timing be advance to compensate for the higher amount of inert gas inside the combustion chamber.

[AndrzejM]

I have EGR which is working just as an on/off valve so your solution won't help me but thanks for sharing! Maybe I'll run a second pipe and second EGR valve someday? I know that Berta had much worse FE when EGR valve stayed closed all the time. So maybe there's some potential. Good to know!

[Daox]

Keep in mind that diesels and gas engines react differently to increasing EGR flow. For gas engines its almost always a good thing (unless you dillute the mixture so much that you get misfires or an incomplete burn). For diesels, balancing EGR is much more tricky. While it can increase efficiency, it generally does not. However, it almost always decreases NOx emissions in both engine types.

Thanks a ton for testing this out t vago. Still looking forward to seeing more results.

[maxc]

On my 1997 f150 I increase the sensor return voltage from the dpfe so the computer advances the timing. With a relay/resister in parallel turned on by the egr. 20 more miles too tank.

[mikeyjd]

Originally Posted by t vago

A few updates:

The UltraGauge did indeed show a highly inaccurate average fuel economy figure. As was mentioned in this post, one should not rely on a ScanGauge or UltraGauge for noting fuel economy due to this sort of mod. This leads to the next update...

The MPGuino should hopefully ship today. If so, I'll install it next week.

First fillup since I did the EGR sensor modification. The results are shown below:



I think that a 7.7% increase in fuel economy is not bad.

I'm still considering installing a MAF sensor, and creating a circuit that will obtain a MAP signal for the engine computer. However, I'm also considering moving my IAT sensor so that it will be before my intake heater. This should maybe provide what I want to do, which is to advance ignition timing. Remember, a higher-than-normal EGR will require that ignition timing be advance to compensate for the higher amount of inert gas inside the combustion chamber.

good work ^

[t vago]

Update

I relocated the IAT sensor from its original position, after the intake air heater and before the throttle body, to before the intake air heater. I think this should provide the proper amount of extra spark advance that will compliment the EGR resistor mod.

Intake Air Sensor relocation


Air Filter Box, Modified with Intake Air Heater - Top View


Air Filter Box, Modified with Intake Air Heater - Bottom View


Dummy IAT sensor in original IAT spot


Induction system, showing Intake Air Heater coolant hoses (and oil catch can)

[AndrzejM]

Nice setup you have! Haven't seen such a creative air intake heater. Good job!

[ECONORAM]

Another thing that might work for sending a cooler air signal to the PCM is adding a 4.7k ohm resistor to the intake temp wire. I think it's worth a 20* drop in reading.