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PostPosted: Mon Sep 14, 2009 7:07 pm 
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There are a couple of arguments supporting the idea of using EGR to improve fuel economy. The first is that it can reduce pumping losses by requiring a wider throttle opening for the same power output, similar to the effect of a shorter duration, lower lift "economy" XFI cam. The second is that by lowering the peak combustion temperature, it allows more ignition timing advance, thus improving fuel economy. (And the same line of thinking suggests the possible use of higher compression ratios.)

I thought it might be interesting to hear what other Team Swift members think about EGR and its effect upon MPG. There have been other threads about EGR. But not specifically about its effect upon FE.

Edit: The Wikipedia article on EGR provides a good outline of the arguments for improved fuel economy, including some points which are more esoteric than what I've mentioned:

http://en.wikipedia.org/wiki/EGR

Edit: Another interesting article: http://autospeed.com/cms/title_EGR-Come ... ticle.html


Last edited by sbergman27 on Fri Sep 25, 2009 10:58 pm, edited 1 time in total.

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PostPosted: Thu Sep 17, 2009 3:41 pm 
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I'm 100% convinced that the EGR improves economy at part throttle. There is also a white paper somewhere on line that demonstrates that EGRs are usually tuned for the best emissions performance and that efficeincy can usually be improved by reducing EGR opening around 10%.
I don't believe that it requires a wider throttle opening, the EGR is after the throttle so the engine should pull the maximum mixture allowed by the throttle and some exhaust gas. The exhaust gas is used as a 'filler' to improve the effective compression ratio and improve combustion.


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PostPosted: Wed Sep 23, 2009 11:04 pm 
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Rhinoman wrote:
I don't believe that it requires a wider throttle opening, the EGR is after the throttle so the engine should pull the maximum mixture allowed by the throttle and some exhaust gas. The exhaust gas is used as a 'filler' to improve the effective compression ratio and improve combustion.

So you would expect that at the same throttle opening... say, 2/3rds throttle... EGR results in greater power, less power, or the same power as without?

That EGR gas does not flow past the throttle is a good point. And I hadn't considered its effect on "effective compression ratio", as you put it. One problem that I have when thinking about this is that I tend to think of recirculated exhaust gases as "poison" to the combustion process, and not simply as "inert gas". I keep having to remind myself.

-Steve


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PostPosted: Thu Sep 24, 2009 10:29 am 
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sbergman27 wrote:
So you would expect that at the same throttle opening... say, 2/3rds throttle... EGR results in greater power, less power, or the same power as without? -Steve


I would expect it to make more power for the same throttle opening. Theres a lot of information on the net but most of it is for diesels, although the same principles apply. The main manufacturers seem to be moving towards EGR intercoolers to gain further improvements in efficiency.


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PostPosted: Thu Sep 24, 2009 3:27 pm 
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Rhinoman wrote:
I would expect it to make more power for the same throttle opening. Theres a lot of information on the net but most of it is for diesels, although the same principles apply. The main manufacturers seem to be moving towards EGR intercoolers to gain further improvements in efficiency.

One could run a vacuum line from the modulator, and another from the EGR valve, through an existing grommet into the passenger compartment. And then connect them up, and disconnect them at a consistent speed on the highway to find out. Seat of the pants, sure. But if the effect is pronounced in either direction, it should be detectable that way. I may try it out.

Of course, even if there is a power decrease with EGR, it does not mean that economy is not improved. But still it would be interesting to know. If power *is* increased, that would be pretty conclusive. I just keep thinking about how if I suck on the EGR line at idle... the engine just dies. No coughing. No sputtering. No trying to go on. It just... dies.

-Steve


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PostPosted: Thu Oct 15, 2009 7:40 pm 
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the EGR is not designed to function at idle or at Wide Open Throttle ,
EGR opens at cruise or part load .

when EGR is introduced to combustion , it effectively makes the engine smaller because it displaces 02 with INert gases that will not support combustion And the INert gases act like a "cushion" and effectively lower compression ratio s .
so the engine does not produce the same amount of power as it would without EGR so , the driver steps down slightly on the throttle to make up for the difference ...
which lowers suction throttling loss.

so you end up with a smaller engine that runs more efficiently ... if all is working as designed .
you can view relative combustion pressure with and without EGR by monitoring secondary spark voltages as you drive the car , using a scope on the passenger seat .

SG2 will provide fuel economy calculations , with and without EGR connected .

you have studied up on the EGR systems so what do you intend to do with your new found knowledge ?

if you were to weld a port in the exhaust after the cat and run a line to the EGR , would not that result in cooler EGR gases reaching the combustion chamber ?

yes it would .


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PostPosted: Sat Oct 17, 2009 3:05 pm 
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mwebb wrote:
it displaces 02 with INert gases that will not support combustion And the INert gases act like a "cushion" and effectively lower compression ratio s .

if you were to weld a port in the exhaust after the cat and run a line to the EGR , would not that result in cooler EGR gases reaching the combustion chamber ?

yes it would .


No the exhaust port is much smaller than the throttle opening, the engine pulls in just as much O2 and fuel plus an amount of exhaust gas which, raises the effective compression ratio.

Modern diesels are using EGR intercoolers to lower exhaust gas temperature.


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PostPosted: Mon Oct 19, 2009 1:33 pm 
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the size of the EGR port into the intake relative to throttle body opening is essentially irrelevant as EGR flow is controlled by the EGR valve pintle rise at the time and pressure differential between the intake and exhaust

when there are EGR gasses present in the combustion chamber , the effective compression and combustion pressure and combustion temperature are all
lowered
compared to when there are no EGR gases present in the combustion chamber

sorry
that's the way it is.

.......................
Rhinoman wrote:
mwebb wrote:
it displaces 02 with INert gases that will not support combustion And the INert gases act like a "cushion" and effectively lower compression ratio s .

if you were to weld a port in the exhaust after the cat and run a line to the EGR , would not that result in cooler EGR gases reaching the combustion chamber ?

yes it would .


No the exhaust port is much smaller than the throttle opening, the engine pulls in just as much O2 and fuel plus an amount of exhaust gas which, raises the effective compression ratio.

Modern diesels are using EGR intercoolers to lower exhaust gas temperature.

..................
true enough
but , you can also get lower temperature exhaust gases from the exhaust down stream where temperatures have already been reduced ....

it accomplishes the same goal , it costs less and it is less complex to implement
so why not ?


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PostPosted: Thu Oct 22, 2009 10:16 am 
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Remember that the stock EGR system is already cooled in its passage through the head and intake manifold. The cooling passages, as we all know, carbon up and plug. So we must design our coolers to be easy to clean.
With that in mind, we might well consider if increased EGR flow, combined with a multistrike CD ignition might produce further improvement in economy with downsides acceptable to hypermilers.
The EGR valve used on the GM 3.1 V6 has three solenoids, probably graduated 1-2-4 in area, and are common junkyard items. This should allow large percentages of EGR, if helpful, and under digital control.
Therein lies the rub, as I see it. The MAP will no longer reflect the required fuel, so in the proposed high EGR cruise mode, the EFI system would have to work from either a MAF sensor upstream of the throttle or the TPS and RPM. Another possibly useful input would be the torque measured by a load cell replacing the rear motor mount donut. This output would be proportional to axle torque, so this could be used only in top gear, or the gear detected and calculated out (UGH).

This can be done in Megasquirt 2. See http://www.msextra.com/index.php
BTW, the exhaust gasses are not entirely inert. There is enough combustion product water to participate in combustion events. The Bible on this is Heywood, and long discussions can be found on not2fast.com.
Throttle response is sure to suffer, since the pressure difference across the throttle is reduced by the EGR. The stock setup, even when clean and working, probably flows 5 to 10 % of exhaust, enough to control NOX, but not to seriously disturb the MAP for fueling calculations. We are proposing, as I see it, to operate for any given output at the highest MAP consistent with effective ignition.
I am currently fitting an Accel 300+ ignition box to Old Blue. I went spejunking and brought back most of the connectors, relays, and underhood fuseboxes from a couple of metros. The Accel box will connect at the coil with matching connectors, to ease AABBAA testing (and failure recovery on the road).
BTW, the stock setup, with the EGR modulator working, expects the stock exhaust restriction to be there in order to work. It's not as simple as with a flathead Ford; a free flowing exhaust disturbs not only EGR backpressure input, but the effective cam timing also.

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PostPosted: Sun Oct 25, 2009 11:28 am 
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How about bypassing the EGR transducer?

The EGR vacuum signal comes from a timed port in the carburetor. But the signal is weakened by the transducer under low load (light throttle) conditions, where NOx is not a problem. (Remember that the manufacturer thinks of EGR as an emissions system and not an economy system.) Light throttle is where pumping losses would be greatest. So increasing EGR there might be expected to improve FE.

Then again, too much EGR under those conditions could also hurt FE.

Update: I've now done some driving with the transducer bypassed. And experimented a little with the transducer. It does cause some drivability issues at very light throttle. Think 25-35 mph on a level road in 3rd or 4th. The engine feels irregular. And from experimenting with the transducer, I get the impression that it stops bleeding the EGR signal at a fairly small throttle opening. So overall, I suspect that disabling it has little actual potential for benefit.


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PostPosted: Wed Nov 04, 2009 2:17 am 
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For those that don't know why the egr system was introduced, we stopped burning leaded fuels in the early 1970's. For the older people I am sure you can remember all the head cracking, cracked exhaust manifolds, and burned valves all those early unleaded fuel cars had.
Lead was introduced into fuel in the early years of automobiles to help cool the valves by allowing better heat transfer from the valves to the valve seats. It also help lubricate compression rings. And the most important part of burning lead in fuel was reducing detonation on lower octane fuel.
Also unleaded fuel does not require distillation, it can be centerfuged. Cheaper to make. But the bad part is centerfuged fuels still retain some of the sulfur that normally comes out with distillation.
Once we took the lead out of fuel, we ran into all the same problems that early engine manufactures did. And the engineers could not find a good substitute for lead.
So they where left with the second option of lowering the combustion chamber temperatures without resorting to going to higher octane fuels. They had to lower the combustion chamber temperatures also to reduce detonation issues.
Having a properly working egr system on a good engine is essential today with the unleaded fuels we burn. The fastest way to get better performance and better fuel mileage is to burn premium fuels. With todays engines and all the electronic controls that are installed, burning premium fuels allows more advanced timing before the knock sensor begins to do its retard trick.

My geo is basicly all stock. And the following mileage has been taken over the past seven years I have owned my car. Highway speeds are usually between 65 to 70mph.

Regular fuel: highway 39, city 24mpg.
Premium fuel: highway 45, city 28mpg.

So at todays fuel prices it is cheaper for me to burn premium the regular fuel.

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97 Geo Metro LSI,1.3L-GT-DOHC-16v,4.10 5-speed,A/C,170,000,suspension lowered 1",4 wheel disk brakes,15"alloy wheels with 185/50-15 Toyo's,GT bucket seats,analog oil pressure gauge,cruise control, new paint job. 40 mpg at 65 mph.
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PostPosted: Wed Nov 04, 2009 1:01 pm 
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fainya wrote:
Having a properly working egr system on a good engine is essential today with the unleaded fuels we burn.

But quite a few engines never came with an EGR. I wouldn't call it essential.

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1994 Metro - MPG project (getting an XFi G10)
1992 Swift - Parts car (gone)
1991 Swift - Parts car (gone)
1990 Swift - Parts car
1997 Metro - Parts car (gone)
1993 Metro - Parts car
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PostPosted: Wed Nov 04, 2009 1:45 pm 
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Gasoline Fumes wrote:
fainya wrote:
Having a properly working egr system on a good engine is essential today with the unleaded fuels we burn.

But quite a few engines never came with an EGR. I wouldn't call it essential.


Cars that came with EGR systems usually run more efficiently if the system is in proper working order. I am having some EGR troubles right now and my around town mpg has dropped into the high 30s compared to low 40s and my highway has dropped from 50-57 down to 46-48. My fix should be done this weekend. Total cleaning of the EGR port and all hoses didn't work, changing to a new EGR valve also didn't work, but replacing the EGR Pressure Transducer Valve should fix it.

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01 Voyager V6 / no mods yet / 24 mpg
84 Horizon / 1760 lbs / was 17.9, now 23.0 mpg
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95 Neon / unk mpg so far


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PostPosted: Fri Nov 06, 2009 8:06 am 
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Gasoline Fumes wrote:
fainya wrote:
Having a properly working egr system on a good engine is essential today with the unleaded fuels we burn.

But quite a few engines never came with an EGR. I wouldn't call it essential.


Including the 98 and up four cylinder Metro/Swift. The problems he's referring to were handled back in the eighties, the only reason for EGR today is to reduce NOX, and the newer catalytic converters do that after the fact.

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PostPosted: Sun Nov 08, 2009 1:43 am 
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I would be curious to see what would happen to your valves if you ran your post 98 with the egr disconnected. And while your at it keep track of your mileage. Disabling the egr on a post 98 car will have the ping sensor worn out in a year. your timing will be retarded all the time and your mileage will go to hell. The combustion chanbers will run hotter, and most likely you will burn a valve or two. Oh what the heck take a head gasket out while your at it too!

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PostPosted: Sun Nov 08, 2009 10:24 am 
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Well, since my 98 came from the factory without EGR (as I just said two posts ago) and no Metro ever had a ping sensor, I'm feeling pretty confident about this challenge.

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PostPosted: Wed Nov 11, 2009 8:17 pm 
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fainya wrote:
For those that don't know why the egr system was introduced, we stopped burning leaded fuels in the early 1970's. For the older people I am sure you can remember all the head cracking, cracked exhaust manifolds, and burned valves all those early unleaded fuel cars had.
Lead was introduced into fuel in the early years of automobiles to help cool the valves by allowing better heat transfer from the valves to the valve seats. It also help lubricate compression rings. And the most important part of burning lead in fuel was reducing detonation on lower octane fuel.
Also unleaded fuel does not require distillation, it can be centerfuged. Cheaper to make. But the bad part is centerfuged fuels still retain some of the sulfur that normally comes out with distillation.
Once we took the lead out of fuel, we ran into all the same problems that early engine manufactures did. And the engineers could not find a good substitute for lead.
So they where left with the second option of lowering the combustion chamber temperatures without resorting to going to higher octane fuels. They had to lower the combustion chamber temperatures also to reduce detonation issues.
Having a properly working egr system on a good engine is essential today with the unleaded fuels we burn. The fastest way to get better performance and better fuel mileage is to burn premium fuels. With todays engines and all the electronic controls that are installed, burning premium fuels allows more advanced timing before the knock sensor begins to do its retard trick.

My geo is basicly all stock. And the following mileage has been taken over the past seven years I have owned my car. Highway speeds are usually between 65 to 70mph.

Regular fuel: highway 39, city 24mpg.
Premium fuel: highway 45, city 28mpg.

So at todays fuel prices it is cheaper for me to burn premium the regular fuel.


:goodpost:
Fainya has some great insight (and first hand experience, obviously) into the history of the EGR.
I wonder if he remembers the GM 'gulp' valves of the 60s...probably.

Do a Wiki on Svante August Arrhenius.
Check out his equation here:
http://en.wikipedia.org/wiki/Arrhenius_equation

As combustion temps increase, so do your 'oxides of nitrogen'.
Thus, the EGR is usually included in engines where laws require lower oxides of nitrogen.

Whether you're into miles per gallon, or power per gallon, you want to burn that fuel as efficiently as you can without destroying your engine and environment.

To restate:
A daily driven vehicle with a working EGR system is specifically designed to lower combustion temperatures and not only prolong engine life, but also lowers Oxides of Nitrogen (NOx).

This:
http://sustainablog.org/2009/05/18/prev ... in-causes/
mentions that NOx (not just CO2) is involved in our 'carbon footprint'.

If you are new to automobile repair, read cautiously some of the posts from Teamswift members claiming that disabling the EGR will help your MPG. Those who suggest those things will NOT be helping you fix your engines.

Bottom line?

Keep your EGR system in good working order for maximum engine life and efficiency.
(...and so you can brag about your carbon footprint :roll: :roll: :roll: :roll: :roll:)

Of course, if your engine did not come with an EGR system, or you are using it for 'full tilt boogey' racing, then by all means, have at it.

The EGR Wikipedia article mentioned above also discourages vehicle owners from disabling their 'external' EGR systems:
In almost all cases, a disabled EGR system will cause the car to fail an emissions test, and may cause the EGR passages in the cylinder head and intake manifold to become blocked with carbon deposits, necessitating extensive engine disassembly for cleaning

If you look carefully under the side view mirror
Image
and above the side clearance light of the red swift (above) you will see some chrome lettering.
Unfortunately, you can't make out the "VVT" which stands for variable valve timing.
Thus, that engine might have an 'internal' EGR system, and no EGR diagram under the hood sticker.

Maybe the European members can confirm with some closer photos.

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PostPosted: Wed Nov 11, 2009 10:39 pm 
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I've got Old Blue's engine piece from part, and it looks to me like the brass tubes that convey the EGR onto the intake valve are the major restriction. Has anyone drilled them out to increase EGR? I am a bit skittish about this, as I see no way to replace them if I don't like the result.With these passages drilled out, the EGR valve would have to modulate exhaust flow.

Am I the first to consider actually doing this?

bob

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PostPosted: Fri Nov 13, 2009 11:04 pm 
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ATaylorRacing wrote:
Gasoline Fumes wrote:
fainya wrote:
Having a properly working egr system on a good engine is essential today with the unleaded fuels we burn.

But quite a few engines never came with an EGR. I wouldn't call it essential.


Cars that came with EGR systems usually run more efficiently if the system is in proper working order. I am having some EGR troubles right now and my around town mpg has dropped into the high 30s compared to low 40s and my highway has dropped from 50-57 down to 46-48. My fix should be done this weekend. Total cleaning of the EGR port and all hoses didn't work, changing to a new EGR valve also didn't work, but replacing the EGR Pressure Transducer Valve should fix it.


FINALLY fixed my problem....in addition to completely cleaning out all EGR ports and vacuum lines, new EGR valve, and new EGR pressure transducer valve I had the red wire going to the electrical plug in that controls the EGR valve break. My next tank of gas for highway driving had the FE jump back up to 49 with quite a bit of city driving mixed in!

_________________
36 time NHRA/IHRA Champion
05 SRT4 / 12.79 @ 111 mph / 40.1 mpg!
01 Voyager V6 / no mods yet / 24 mpg
84 Horizon / 1760 lbs / was 17.9, now 23.0 mpg
96 Geo Metro / 1590 lbs / was 46.2, now 60 mpg!
95 Neon / unk mpg so far


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PostPosted: Sun Nov 15, 2009 8:35 am 
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drbobw wrote:
brass tubes that convey the EGR onto the intake valve are the major restriction.

Those aren't for EGR. :search:

_________________
1994 Metro - MPH project (getting a DOHC G13B)
1994 Metro - MPG project (getting an XFi G10)
1992 Swift - Parts car (gone)
1991 Swift - Parts car (gone)
1990 Swift - Parts car
1997 Metro - Parts car (gone)
1993 Metro - Parts car
1989 Swift GTi - Parts car
1998 Metro - Parts car


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PostPosted: Sun Nov 15, 2009 10:25 am 
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VVT and EGR are completely different, unrelated things. The reason newer cars don't have EGR is that the newer "three way" catalysts handle NOx after the fact.

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PostPosted: Sun Nov 15, 2009 1:27 pm 
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Woodie wrote:
VVT and EGR are completely different, unrelated things.

Are they completely different and unrelated if they are used for the same purpose?

...


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PostPosted: Wed Nov 18, 2009 7:50 am 
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If they were used for the same purpose then no, they wouldn't be "different and unrelated". But they accomplish two completely different goals. VVT adjusts the valve timing according to RPM in order to broaden the torque curve of the engine. You can buy a cam that makes a lot of low end torque or you can buy a cam that makes a lot of horsepower up high. Either one is going to compromise the other. VVT allows the engine to act as if it has two different cams in it that switch back and forth as needed.

EGR is a bit of a patch thrown on engines to reduce combustion chamber peak temperatures and thereby reduce emissions of Oxides of Nitrogen (NOx). In the mid nineties they figured out how to get catalytic converters to handle this job (three way cats) so EGR has mostly gone away.

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PostPosted: Wed Nov 18, 2009 10:22 am 
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Woodie wrote:
If they were used for the same purpose then no, they wouldn't be "different and unrelated". But they accomplish two completely different goals. VVT adjusts the valve timing according to RPM in order to broaden the torque curve of the engine.
...
EGR is a bit of a patch thrown on engines to reduce combustion chamber peak temperatures and thereby reduce emissions of Oxides of Nitrogen (NOx).

And if you can adjust the valve timing you can also adjust the amount of overlap which gives you EGR. Though I guess in that scenario it is Exhaust Gas Recycling in stead of Return? :)

So: VVT >= EGR + 2 x cams ?


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PostPosted: Wed Nov 18, 2009 11:47 am 
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After a quick bit of searching it appears to be referred to as IEGR or internal EGR. Fun stuff.


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