Any difference with Japan spec 7mgte vs US/Europe

AaronB

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#1
Did some research on this and couldn't find any info. I was reading up on Subaru's EJ205 engine, and there were a number of differences between the Japan version and the "world" version. Got me thinking about the 7m.

Obviously the 1jz was the main engine later on, but those first few years, was there any differences to the 7m?
 

suprarx7nut

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#2
JDM 7M did not use an EGR system. The blocks are the same, as far as I know, as are the heads. The heads for the JDM market had a block off plate for the EGR passages. The JDM ECU, therefore, is tuned with no EGR system factored in.

That's about the only difference I know of.
 

Nick M

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#6
Since it was brought up here by a distinguished member many times....

Experiments were performed on a 2.4L boosted, MPI gasoline engine, equipped with a low-pressure loop (LPL) cooled EGR system and an advanced ignition system, using fuels with varying anti-knock indices. The fuels were blends of 87, 93 and 105 Anti-Knock Index (AKI) gasoline. Ignition timing and EGR sweeps were performed at various loads to determine the tradeoff between EGR level and fuel octane rating. The resulting engine data was analyzed to establish the relationship between the octane requirement and the level of cooled EGR used in a given application. In addition, the combustion difference between fuels was examined to determine the effect that fuel reactivity, in the form of anti-knock index (AKI), has on EGR tolerance and burn rate. The results indicate that the improvement in effective AKI of the fuel from using EGR is constant across commercial grade gasolines at about 0.5 ON per % EGR. In addition, there was a detectable difference in burn rates between fuels, the magnitude of which varied with operating condition. At the only condition where all three fuels could be compared on an equal basis, no detectable difference was found in EGR tolerance between fuels. Emissions results confirm the effect of higher fuel reactivity on burn rate, with lower AKI fuels leading to higher NOx emissions at a constant EGR level and load.
 

suprarx7nut

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#7
Since it was brought up here by a distinguished member many times....
From your text I gathered that EGR can be used to effectively improve the AKI of fuel. I have no idea what the units are for EGR, though. % what?How is EGR "level" measured and what are the programmed "levels" in the 7M?

The theory and results mentioned make sense. EGR certainly reduces likelihood of knock. However, I don't think that helps us determine if the EGR system in the 7M provides an effective increase in AKI of .01 ON, .1 ON, 3 ON, etc...
 

Piratetip

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#8
Other similar tests have been done on multiple engines relating EGR to AKI to Reformation Index.
Lots of whitepapers out there.
If anyone has an SAE subscription this is another.
https://www.sae.org/publications/technical-papers/content/2016-01-0712/

Looks like the note above is just a copy / paste of the summary from the following study / whitepaper.
https://www.sae.org/publications/technical-papers/content/2012-01-1149/

A full read / review on these papers would need to be done to get into the real details and data.

Agreed suprarx7nut:
A research study would need to be done on the 7M to determine if the same characteristics / outcomes in relation to EGR are also found on this specific engine.
We are all aware of the benefits that EGR brings with it.
Though without quantitative data results on the 7M behavior its difficult to definitively say to what level this system performs to.
Comparing it to a much more modern engine would be difficult.
 

Nick M

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#9
The theory and results mentioned make sense. EGR certainly reduces likelihood of knock.
Of course it does. It introduces inert gas into the air charge. Some time back...not quite but maybe 2 decades and continuing here, the clowns said things like EGR causes knock and head gasket problems. And it was repeated and the explanations ignored. The engines are the same, the tune is not, and the engines without EGR have the block off plate, as mentioned.

I remember an entire thread deleted (elsewhere) over the false information that led to internet bickering.
 

3p141592654

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#10
EGR pros are as mentioned in the paper, you can run more timing at cruise without knock which leads to better gas mileage. The units are % charge dilution vs anti-knock index. The % dilution is governed by the vacuum modulator and the EGR valve orifice diameter, neither of which is tunable. The ECU only commands EGR on/off, and its "on" only for cruise conditions. The whole thing is off and has no effect at WOT or idle. Deleting it can lead to knock at cruise (in principle), but really there is enough dynamic range in the ECU knock sensor loop that this should not be an issue. You will fail a NOx test badly with it deleted. Exhaust temps are a little higher without EGR at cruise. Enough to matter? I don't know. Some people were pretty vehement about it.

The cons are carbon buildup in the intake but other than blocked EGR pipes, the impact is negligible compared to the affect of the PCV system. There have been claims the exhaust flow through the "EGR cooler" leads to cylinder 6 overheating. Hardly seems likely given the very small gas flow volume compared to whats going through the exhaust ports and combustion chamber 1 inch away from the cooler surrounded by water jackets. This is usually "supported" by the claim that the head gasket for cylinder 6 always fails. In practice, and there's lots of pictures of failed head gaskets on this site, the gasket failures seem random by cylinder and is definitely not "always #6".
 
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suprarx7nut

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#11
EGR pros are as mentioned in the paper, you can run more timing at cruise without knock which leads to better gas mileage. The units are % charge dilution vs anti-knock index. The % dilution is governed by the vacuum modulator and the EGR valve orifice diameter, neither of which is tunable. The ECU only commands EGR on/off, and its "on" only for cruise conditions. The whole thing is off and has no effect at WOT or idle. Deleting it can lead to knock at cruise (in principle), but really there is enough dynamic range in the ECU knock sensor loop that this should not be an issue. You will fail a NOx test badly with it deleted. Exhaust temps are a little higher without EGR at cruise. Enough to matter? I don't know. Some people were pretty vehement about it.

The cons are carbon buildup in the intake but other than blocked EGR pipes, the impact is negligible compared to the affect of the PCV system. There have been claims the exhaust flow through the "EGR cooler" leads to cylinder 6 overheating. Hardly seems likely given the very small gas flow volume compared to whats going through the exhaust ports and combustion chamber 1 inch away from the cooler surrounded by water jackets. This is usually "supported" by the claim that the head gasket for cylinder 6 always fails. In practice, and there's lots of pictures of failed head gaskets on this site, the gasket failures seem random by cylinder and is definitely not "always #6".
Awesome, thank you. This is a great explanation that pulls together some scattered knowledge I had assumed true.
 

Asterix

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#12
EGR gives the same results as water/methanol injection! (Slowing and cooling combustion)
I like to think NOx reduction is a side effect, with the primary effect being able to use lower AKI/octane rating fuel for a given compression ratio and timing.

Most people latch onto the emission reduction aspect and immediately hate it due to their ignorance.

Nice to see knowledgeable discourse here!
 

Piratetip

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#13
It also lowers pumping losses therby increasing engine efficiency.
Another key result is the reduction in engine displacement since the inert gas is taking up a volume of space in the cylinder.
Lower displacement while cruising = better MPG.

There are many many benefits to a properly functioning EGR system.

Besides a dedicated race car I see no reason to not utilize EGR on a vehicle that will see cruising usage on the street.
 

SupraDrew

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#14
I would like to give my observations with running no EGR system for many years.

I did my Turbo swap way back in 99, i never had an EGR system on my turbo motor. I was running a US ECU up until this year, i had picked up a JDM turbo manual ECU many years ago but never got around to installing it. I did install it this year and my cruising EGT temps dropped about 100C or more.

Just my observation, making no recommendations on EGR either way.
 

f00g00

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#15
I can see why they don't have an egr system on their cars. When I was stationed there in the 80's and 90's the driving was mostly city and there weren't too many places to highway cruise except the highway to Narita airport. They were a few toll roads too but for the most part it was stop and go traffic.
 

Nick M

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#17
There have been claims the exhaust flow through the "EGR cooler" leads to cylinder 6 overheating. Hardly seems likely.
The same people promote a front facing intake saying it doesn't change cylinder distribution to number 1.
 

suprarx7nut

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#18
I would like to give my observations with running no EGR system for many years.

I did my Turbo swap way back in 99, i never had an EGR system on my turbo motor. I was running a US ECU up until this year, i had picked up a JDM turbo manual ECU many years ago but never got around to installing it. I did install it this year and my cruising EGT temps dropped about 100C or more.

Just my observation, making no recommendations on EGR either way.
That right there is excellent anecdotal evidence why it's important to match your ECU to your EGR status.