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Manual EGR control; Possible?
Topic Started: Jun 2 2010, 04:27 PM (1,222 Views)
Switchblade8588
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Well I would like to know if it's possible to make a manual egr control of some sort. An adjustable one would be the best but a set on off would work also. I would think if you could control the amount of egr gas at highway speeds you would be able to get a mpg increase. I believe the pruis runs something like 30% at some times. If you can't control the amount would it be possible to control it on an on/off switch and run the egr more maybe above 30mph or something. Just a thought and was wondering what you guys thought. Thanks Dan
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bogs
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Duct tape heals all wounds

Mwebb will be along shortly, however if you see this and can't wait, go find the altitude = mpg thread, he explains it pretty fully there :)
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JellyBeanDriver


Where did you read that EGR improves MPG?

EGR valve is actuated using vacuum generated at a TBI port that is uncovered when the open the throttle.
That line is in series with a 12V solenoid to turn the capability of the EGR working on or off. The vacuum line then goes to the EGR modulator that bleeds off the vacuum depending on the exhaust pressure at the EGR exhaust sense port. This helps meter the EGR flow. Finally the vacuum line goes to the EGR valve.

You can plumb out the modulator and then control the solenoid using a switch, tying the other side of the switch to a manifold vacuum line vs a ported line. Don't know how you would meter it depending on engine load as this method is full ON/OFF and would likely decrease MPG if anything.

Edited by JellyBeanDriver, Jun 2 2010, 09:07 PM.
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nerys
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Grr

it would increase mpg if you are using "more power" than you need. IE if you make the engine "smaller" (which is what egr does in essense) then as long as that smaller engine is "enough" to do what you need you will GAIN MPG

but if you put the system BELOW what you need and therefore have to "add more foot" to get what you want then you will LOOSE MPG. since you will in essence be "overworking" a smaller (effective) engine now.
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mwebb
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FOG

the two ways that EGR increases fuel economy are by
Decreasing effective engine displacement / size by diluting the air fuel mixture with INert gas
( exhaust gas is used as the INert gas )
and
Reducing suction throttling loss , which happens when the driver un consciously steps down farther on the throttle during the EGR "on" time , to maintain the same level of "power" as when the EGR is "off" .

suction throttling loss;
is caused by the engine pulling a vacuum against the mostly closed throttle plate as the piston goes down with the intake valve open and exhaust valve closed , at low engine loads .
it decreases efficiency significantly .

you can add too much EGR
which would decrease combustion temperature and combustion pressure to the point that the engine would misfire , you could monitor the 02 sensor waveform to see when that was beginning and adjust EGR flow to prevent it
if you had a mind to and a scope .
============================================
on ecomodder a poster named DAOX is experimenting with this on his toyota paseo
Edited by mwebb, Jun 2 2010, 10:03 PM.
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nerys
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Grr

any results? I am getting a scope (drooling while waiting for it from china) to connect to O2 would I just put a lead on the O2 lead and the other on ground?

got a link to that thread on ecomodder?
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Switchblade8588
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So if I understand right it might be possible to increase mpg aslong as your not over working it? And you could also possibly lower mpg if to much is added but adding higher levels could possibly help? Just a thought I've been playing with
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mwebb
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FOG

Switchblade8588
Jun 2 2010, 11:23 PM
So if I understand right it might be possible to increase mpg aslong as your not over working it? And you could also possibly lower mpg if to much is added but adding higher levels could possibly help? Just a thought I've been playing with
yes , theoretically correct .
and
it may help to take EGR gases from Post cat , after the cat , downstream of the cat
and pipe them back up to the intake
using and EGR valve from something else
( Ford F150 ) , controlled by the same Geo Metro EGR solenoid with NO EGR back pressure transducer.
max EGR flow can be restricted ....
as needed
to prevent misfire as monitored by scope on 02 sensor waveform BEFORE it can be felt
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Switchblade8588
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Well what I was thinking is if there was a way to control the amount of egr gases going in on something like a manual control I could adjust from inside the car I would be able to test the effects of different amounts of egr gases and the effect it has on mpg. Anyone have an idea on building a manual adjustable egr control? If I could get an adjustable unit built I would do some a-b-a-b on different lvls.
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mwebb
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FOG

Switchblade8588
Jun 2 2010, 11:54 PM
Well what I was thinking is if there was a way to control the amount of egr gases going in on something like a manual control I could adjust from inside the car I would be able to test the effects of different amounts of egr gases and the effect it has on mpg. Anyone have an idea on building a manual adjustable egr control? If I could get an adjustable unit built I would do some a-b-a-b on different lvls.
you should know that the ECM probably makes allowances in the MAP value for when EGR is open ,
so
you should let the ECM open the EGR with the EGR solenoid connected to an EGR diaphragm as the stock system does .
you can control flow with whatever valves you may design .

if you open EGR your self without the ECM
it will decrease intake vacuum and therefore increase MAP as MAP = Baro - intake vacuum

that will piss off fuel trim and have an effect on ignition timing that you do not want

so
yes
your idea may work -
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