Closing the EGR Valve *check first post for links*

Re: Closing the EGR Valve

Postby coxy47 on Wed Apr 18, 2012 8:09 am

odie602r wrote:Okay, so with full EGR blank in, is it normal for fuel economy to worsen? On a highway (100kmh) trip yesterday of about 250kms return the MN used almost half a tank. :shock:

I haven't refilled just yet to get an exact calculation but mine on a highway normally gets 9ishL/100kms.

I was expecting fuel economy to improve based on reports from here ....

Yes it is. The problem is that with the egr blank in, when the engine operates the egr valve its cuts the clean air supply via the throttle. This produces a notable vacuum in the manifold causing the engine to run inefficiently. I also believe, but can't be sure, that the engine increases the fuel metering in an attempt to counteract this. There are work around for this and the best solution by far is Longrangers mod though it does require a little work to put it in place.

Without any modifications I find my economy is better around town but worse on Highway.
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Re: Closing the EGR Valve

Postby srb on Wed Apr 18, 2012 8:59 am

coxy is correct!... The EGR valve is open at 100% during highway driving but around town is only open about 60-70%. This maybe the reason why some use more fuel with the blank plate. I have done both LR's bypass but yet to give it a good test on the highway to see if it uses less fuel, though I can say the Tri feels much happier around town with LR's latest bypass. 8-)
Interestingly I have notice less black smoke when not on boost.. Before the bypass there was alway a black puff of smoke when accelerating from a stand still or light acceleration below 1500 rev's. Now there's seems to be hardly any smoke at all, almost nothing! My guess is it creates better air to fuel ratio for much cleaner burning. LR or some of the other gurus might be able to explain why. ;)
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Re: Closing the EGR Valve

Postby srb on Wed Apr 18, 2012 9:16 am

Ben, you might benefit from installing a one way valve in your map line or drilling a hole in your throttle body flap, this will at least insure you don't get any engine codes and might even help with your fuel consumption. Both mod's are easy to do and will only take you about 5-10min. PM if you need instructions. 8-)
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Re: Closing the EGR Valve

Postby odie602r on Wed Apr 18, 2012 9:19 am

does a 10mm hole in it improve the economy? Economy is something I'm not overly pleased with on the Triton (I seem to have got one that uses more).
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Re: Closing the EGR Valve

Postby srb on Wed Apr 18, 2012 9:30 am

Not sure mate cause I never went that way... Something to consider before drilling the hole is you may experience a rough and shaky shut down every time you turn the engine off. For this reason I went with the one way valve. ;) Some Tritons do seem to use more fuel than others though... This could be for many different reasons from engine/transmission and ecu mapping tolerances, the list goes on. :roll:
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Re: Closing the EGR Valve

Postby fraz91 on Wed Apr 18, 2012 9:53 am

odie602r wrote:does a 10mm hole in it improve the economy? Economy is something I'm not overly pleased with on the Triton (I seem to have got one that uses more).


I'd start with a 6mm hole and work your way up. It does cause the engine to run-on a little longer on shutdown, but a 6mm hole equalises the pressure pretty well (in my case anyway). The rough/shaky shutdown is nothing major, just a little extra jitter when it stops. ;)
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Re: Closing the EGR Valve

Postby odie602r on Wed Apr 18, 2012 10:52 am

Hey Lachlan - by equalising the pressure does that mean the economy should at least return to what it was pre-EGR blank?

If fuel economy stays this bad, I'm considering just a catch can instal to stop the carbon build up problem - although I really wanted to do both.
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Re: Closing the EGR Valve

Postby fraz91 on Wed Apr 18, 2012 11:04 am

The 6mm hole won't really do much for economy, but it will stop the P0299 Turbo Underboost code from popping up. It's probably the most dangerous of the codes in the MN, because without an EGT gauge in a manual, it IS possible to melt the engine albeit very difficult.

I've found my economy has been pretty good, but I'm also running a Chip with EGT controller and generally drive by that to keep the fuel usage down ;)
Last edited by fraz91 on Fri Apr 20, 2012 5:29 pm, edited 1 time in total.
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Re: Closing the EGR Valve

Postby odie602r on Wed Apr 18, 2012 1:54 pm

srb wrote:Ben, you might benefit from installing a one way valve in your map line or drilling a hole in your throttle body flap, this will at least insure you don't get any engine codes and might even help with your fuel consumption. Both mod's are easy to do and will only take you about 5-10min. PM if you need instructions. 8-)


PM sent.

hopefully you have pics with the instructions ....
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Re: Closing the EGR Valve

Postby odie602r on Wed Apr 18, 2012 8:45 pm

Okay, more specific info on change in fuel economy pre/post EGR blank - please tell me if you think I'm creating a storm in a tea cup :?:

With engine stock standard (and currently only 3300kms on the clock), best mileage has been 9.43L/100kms (on a 406km trip) at highway cruising at 100km/h. Next best 9.86L/100kms for return of above trip.

Next best was then another 400km trip, towing 750kg enclosed trailer (just below height of canopy) at highway speed (100km/h) 10.7L/100km.

Now, with EGR full blank just installed, and 332kms travelled (with approx 250kms highway cruising at 100km/h) it returned 11L/100kms.

That's approximately a 16% increase in fuel consumption, if I did the maths right. :geek:

Will srb's one way valve trick fix the increase, or will the Chip IT chip do the same when I get that in the next month or so?

All criticisms, comments, wisdom, and reality checks welcome :P
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Re: Closing the EGR Valve

Postby coxy47 on Wed Apr 18, 2012 9:15 pm

Your maths are correct. I cant comment on the one way valve approach but it should have a similar effect to installing the chip it with the map mod.

The one way valve acts by allowing air through when the manifold is below atmospheric pressure so this will produce a boost reading or 0psi or slightly below depending on the valve and piping when the egr valve is fully opened and the throttle is closed. This will not truly fix th vacuum though as its too restrictive.

The chip it achieves a similar result through clipping the voltage of the map sensor. Long story short the chip sees the real value and lies to the ecu about what it is.

This will fix any problems with boost codes but i dont know about the fuel usage as i never when down that path but my suspicion is it wont give the full result. The only true way to fix the problem is to ensure that the engine always recieve a full supply of clean air.

I wouldnt go down the throttle body hole path though this may help. At this point in time im running a switch that manually disables the throttle flap from closing when running but allows it to shutdown properly when the switch is in the on position. Not the best method as it regulaly produces engine lights but quick and dirty and it works. THis will be gone when i get around to doing LR's mod as this is the best solution by far.
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Re: Closing the EGR Valve

Postby odie602r on Wed Apr 18, 2012 9:36 pm

And LR's mod is the one where something needs to be welded or brazed near the radiator - is that it? I seem to remember reading it on one of these 41 pages.

I'm assuming that mod is one that cannot be hidden from a Mitsu dealer, and hence would definitely void the warranty ...

Maybe I need to question ChipIT support further re this clipping the voltage of the map sensor. They seemed a bit vague on it when I first asked (although I was vague in describing it also)

I was hoping to avoid that.

Is a 16% fuel increase but no carbon deposit in manifold a fair trade?
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Re: Closing the EGR Valve

Postby sierra on Wed Apr 18, 2012 11:11 pm

coxy47 wrote: The only true way to fix the problem is to ensure that the engine always recieve a full supply of clean air.

THis will be gone when i get around to doing LR's mod as this is the best solution by far.


Surely LR's mod tricks the MAP pressure reading and doesn't do anything to solve the problem of restricted airflow?
The low manifold vacuum is still there but the ECU doesn't know. That the MAP reading is positive when the manifold is negative might result in some extra fuel?
The one way valve simply stops any negative pressure reading.
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Re: Closing the EGR Valve

Postby srb on Wed Apr 18, 2012 11:41 pm

sierra wrote:
coxy47 wrote: The only true way to fix the problem is to ensure that the engine always recieve a full supply of clean air.

THis will be gone when i get around to doing LR's mod as this is the best solution by far.


Surely LR's mod tricks the MAP pressure reading and doesn't do anything to solve the problem of restricted airflow?
The low manifold vacuum is still there but the ECU doesn't know. That the MAP reading is positive when the manifold is negative might result in some extra fuel?
The one way valve simply stops any negative pressure reading.


Sierra, LR has two mod's! 8-) The one you mentioned was the first step... Then he plumbed a larger 3/4 hose from the steel intercooler pipe strait into the bottom of EGR valve. So in effect he has re-intrudused the EGR valve with out the EGR gasses, so now we have clean intercooled boosted air flowing strait into the intake manifold. 8-) By the way... Im super impressed on how this improves these engines!
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Re: Closing the EGR Valve

Postby sierra on Thu Apr 19, 2012 9:40 am

srb wrote:Sierra, LR has two mod's! 8-) The one you mentioned was the first step... Then he plumbed a larger 3/4 hose from the steel intercooler pipe strait into the bottom of EGR valve. So in effect he has re-intrudused the EGR valve with out the EGR gasses, so now we have clean intercooled boosted air flowing strait into the intake manifold. 8-) By the way... Im super impressed on how this improves these engines!


That's interesting.
The exhaust pressure is a lot higher than the boost so the manifold pressure will still be lower than standard but the results are what count.
Hats off to LR for getting stuck into sorting it out!

I'm just so glad that mine has been code free since I blanked the EGR and strangely, runs better with the throttle valve operating than off and open. There has to be a stealthy method to overcome the operation of the throttle valve.
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Re: Closing the EGR Valve

Postby coxy47 on Thu Apr 19, 2012 11:39 am

The part you have overlooked sierra is that because the exhaust system is essentially open and doesn't get blocked off under egr operation, the pressure from the egr will hardly be above atmospheric. The majority of the gasses still exit the exhaust pipe rather then into the manifold.
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Re: Closing the EGR Valve

Postby srb on Thu Apr 19, 2012 1:33 pm

Thats right coxy! There is more air pressure coming from the intercooler pipe! 8-)
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Re: Closing the EGR Valve

Postby sierra on Thu Apr 19, 2012 4:15 pm

coxy47 wrote:The part you have overlooked sierra is that because the exhaust system is essentially open and doesn't get blocked off under egr operation, the pressure from the egr will hardly be above atmospheric. The majority of the gasses still exit the exhaust pipe rather then into the manifold.


If that's the case coxy, then why do people get problems with low pressure MAP signals when the EGR is blocked?
I realise that only a small part of the exhaust gas enters through the EGR valve.
I have also read that the exhaust pressure is always higher than the boost pressure.

Edit. Just had a read up and the exhaust back pressure is usually around twice+ that of the boost pressure but that ratio reduces with lower boost. Certainly couldn't find any circumstances where the boost would be higher than the exhaust, even at light throttle.
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Re: Closing the EGR Valve

Postby coxy47 on Thu Apr 19, 2012 4:50 pm

sierra wrote:If that's the case coxy, then why do people get problems with low pressure MAP signals when the EGR is blocked?
I realise that only a small part of the exhaust gas enters through the EGR valve.
I have also read that the exhaust pressure is always higher than the boost pressure.


Not 100% certain as this is only theory but i believe the its not so much a low pressure code as in the pressure is a vacuum but more that the MAP sensor is reading a pressure lower then what it predicts for the corresponding MAF and rail pressure readings. The blocked MAP line due to EGR gasses will act as a restriction and minimise the pressure that reaches the sensor. This is because air flow will always follow the path of least resistance.

The pressure in the cylinder will always be higher then the boost pressure (i.e. the cylinders air pressure will be higher air post combustion then pre combustion) but as above the air will always follow the path of least resistance which in 99% of cases will be the exhaust pipe as it is also under negative pressure between pulses.

Exhaust gas is not quite a constant flow. There is effectively a high pressure front at the start of the pulse and subsequently a negative presssure wake behind the pulse. This vacuum actually aids in pulling the enxt puls of exhaust gas out of the exhaust manifold. This is also why its important not to go to large and free flowing with an exhaust pipe size.

This principle coupled with the relatively restrictive egr piping will lead to more gas flowing through the exhaust pipe then the egr.
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Re: Closing the EGR Valve

Postby srb on Thu Apr 19, 2012 5:26 pm

srb wrote:Thats right coxy! There is more air pressure coming from the intercooler pipe! 8-)


What I probably should have said was the air from the turbo will be more free flowing than the amount of exhaust gas that normally would flow from the EGR pipe. LR's bypass allows the intercooled air to bypass through the EGR valve when the throttle flap is partially closed. I would assume the cool dense air would flow much easier through intake manifold than hot exhaust gas. This will be most effective when cruising at highway speeds when the EGR valve is 100% open. Since doing this mod I've noticed my engine is smoother and EGT's are about 50 degrees cooler at cruising speeds. I can't report on fuel economy yet as it was only last week when I did the mod. Will report that once I've done some highway driving. ;)

LR might tune in because he's has had good reports with he's truck.
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Re: Closing the EGR Valve

Postby sierra on Thu Apr 19, 2012 6:30 pm

coxy47 wrote:
This vacuum actually aids in pulling the enxt puls of exhaust gas out of the exhaust manifold. This is also why its important not to go to large and free flowing with an exhaust pipe size.
This principle coupled with the relatively restrictive egr piping will lead to more gas flowing through the exhaust pipe then the egr.


I think you will find the exhaust pulses after a turbo are of little consequence, unlike a naturally aspirated engine.

I agree, as I said before, that much less exhaust flows through the EGR pipe than the main exhaust, that much is obvious.
My point is that, since the exhaust pressure is higher than the boost, the amount flowing from the mod must be less than it was from the exhaust. Not more.
How can this mod have any effect when the throttle valve is open to any degree? The flow would simply stop since the source pressure and manifold pressure would be the same, the tiny amount would only be significant when that butterfly is closed.
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Re: Closing the EGR Valve

Postby coxy47 on Thu Apr 19, 2012 7:00 pm

Fair point. I neglected the air resistance provided by the turbo.

I can't quite explain why unfortunately other then the fact that the even with the turbo the resistance of the exhaust will be far lower then that of the egr pipe.

I do know that when my egr is operating normally it sits at a map pressure of maybe 1psi gauge pressure whereas at the same conditions and speed (100kmh ish) with the egr blank in and the throttle flap disabled it sits at about 6-7psi. I can't comment on the effectiveness of LRs mod personally but I would expect a gauge pressure somewhere between the two values.

Wish I could explain it better.
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Re: Closing the EGR Valve

Postby Longranger1 on Thu Apr 19, 2012 7:17 pm

If you wanted to look at it from 'litres per second of gas flow' perspective, then yes, there would be more exhaust gas flow (unblanked) than air flow from the mod. Exhaust backpressure upstream of the turbine ensures this. The VGT would probably be worse than a conventional turbo in this respect. It does however redeem itself with quicker spool up though. 8-)

There is no free lunch, but this at least allows most of the restriction from having an EGR blank in place and the throttle valve still doing its thing, to be minimized. Separate pressure guage readings bear that out (pre and post throttle valve).

You also have to remember that the EGR valve is now able to flow boosted, clean air instead of depleted exhaust gas which has a significantly reduced oxygen content (as well as being hotter and less dense). This helps considerably with a cleaner, more complete burn which consequently lowers EGT's at cruise.
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Re: Closing the EGR Valve

Postby sierra on Thu Apr 19, 2012 7:24 pm

coxy47 wrote:Fair point. I neglected the air resistance provided by the turbo.

I can't quite explain why unfortunately other then the fact that the even with the turbo the resistance of the exhaust will be far lower then that of the egr pipe.

I do know that when my egr is operating normally it sits at a map pressure of maybe 1psi gauge pressure whereas at the same conditions and speed (100kmh ish) with the egr blank in and the throttle flap disabled it sits at about 6-7psi. I can't comment on the effectiveness of LRs mod personally but I would expect a gauge pressure somewhere between the two values.
Wish I could explain it better.


The driving force for the exhaust through the EGR valve is the difference in the pressure of the exhaust and the inlet manifold. They are the same for the EGR as for the exhaust, pre turbo. Forget flow, it's pressure. The throttle valve is there to reduce the manifold pressure and therefore, increase the difference in pressure, increasing the flow.
When you disable the throttle valve you allow the manifold to run at full boost pressure, hence the increase in the MAP reading from 1psi to 6-7psi. The exhaust pressure and hence the EGR feed pressure at that time would likely be about 14psi so you can see the throttle valve literally doubles the flow since it doubles the pressure differential.
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Re: Closing the EGR Valve

Postby coxy47 on Thu Apr 19, 2012 8:36 pm

sierra wrote:
The driving force for the exhaust through the EGR valve is the difference in the pressure of the exhaust and the inlet manifold. They are the same for the EGR as for the exhaust, pre turbo. Forget flow, it's pressure. The throttle valve is there to reduce the manifold pressure and therefore, increase the difference in pressure, increasing the flow.
When you disable the throttle valve you allow the manifold to run at full boost pressure, hence the increase in the MAP reading from 1psi to 6-7psi. The exhaust pressure and hence the EGR feed pressure at that time would likely be about 14psi so you can see the throttle valve literally doubles the flow since it doubles the pressure differential.


I understand that. I'm not quite sure the point I was trying to make with that comment. :oops:

The best I can come up with is that I was trying to make the point that air will always flow to the lowest pressure so once the manifold reaches atmospheric it will stay there or slightly above (read 1psi) and the flow will be diverted out the exhaust. Whereas with the LR bypass mod the boost pressure is still entirely directed at the manifold so it will the map reading will always be higher then with the egr under full operation.

Unfortunately I know what I'm trying to say but I'm hopeless at explaining myself. I think this is one of the times I should just shut up for a bit as the conversation has gone a little of topic 8-)
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