7MGTE egr or no egr

[Blackdawg]

i don't think its bad if your rebuilding the engine, why not get rid of it? BUT! that all depends on what your going to be running on the car. If your going stockish...leave it on, might as well. If your running a good tuning system(standalone ecu or MAFT) and running lots of aftermarket parts...then i say why not, get rid of it. It all depends on your situation and if you want to tune around it. I decided i will just tune around it. Ill be adding Meth/water later too.

 

[mirage83]

i don't think its bad if your rebuilding the engine, why not get rid of it? BUT! that all depends on what your going to be running on the car. If your going stockish...leave it on, might as well. If your running a good tuning system(standalone ecu or MAFT) and running lots of aftermarket parts...then i say why not, get rid of it. It all depends on your situation and if you want to tune around it. I decided i will just tune around it. Ill be adding Meth/water later too.

Different situation, as you're accounting for upgrades like stand-alones which can eliminate the need for the EGR rather than just wanting to get rid of it to make your engine bay cleaner or for the awesome increases in power you get from chunking it. :biglaugh:

Way too many people toss them based on what they believe it does (or doesn't do) as opposed to what can be found out by researching the subject.

 

[Rollus]

Hi guys,

I won't giving my opinion about political or ecological consideration (i'm still catted but runing EGRless make me burn 15% less fuel). I wish to enter in the technical debate

EGR is off when THW is 57°C (135°F).
So, why this wouldn't works:

I dont have an afc to tune with but have an adjustable resistor hooked up to the iat, fooling the ecu of the actual temp, which in turn dumps more fuel. Also have a holley 255 fuel pump. Just finishing a rebuild and blocked off the egr. Anyone have this type of setup to know if it will work first hand without an afc?

I don't remember off hands what else is limited by THW, but if it's faked, then ECU is like a JDM one for that temp.

I don't know if I'm right, that's just my feels..

++

RolluS

 

[jetjock]

I've said it before: there's a certain amount of irony when considering those who typically yank this stuff off are the ones who will live with the results longest.

Rollus: Sorry Mon-sewer, some of your post makes no sense and the rest is technically incorrect.

Blackdawg: Sticking to the emissions issues it's not possible to tune around a lack of EGR.

Van: My mistake. I see your reasoning has nothing to do with what I getting at. :icon_razz

 

[3p141592654]

Some comments on the ECU control of EGR

1) There is no adjustment of mixture in the ECU code when EGR is turned on. Since this is a type L system any correction to fuel to maintain stoicheometry is already compensated by the AFM which will see a small drop in air flow when EGR is on

2) There is no timing adjustment when EGR is commanded on. However, the base timing map is certainly set assuming EGR to be functional. I have posted the timing map here http://www.supramania.com/forums/showthread.php?73379-3P-s-TCCS-Disassembly-Analysis&p=1712465&viewfull=1#post1712465, and if someone wants to send me a JDM ECU I will extract it and compare.

3) EGR is commanded only for the following conditions. Load < 45%, AFM freq > 48Hz, coolant > 60C, and throttle not closing rapidly. Under these conditions we can expect the knock sense algorithm to pull timing if knock is sensed. Also, under these conditions the fuel mode will be closed loop.

 

[CyFi6]

Some comments on the ECU control of EGR

1) There is no adjustment of mixture in the ECU code when EGR is turned on. Since this is a type L system any correction to fuel to maintain stoicheometry is already compensated by the AFM which will see a small drop in air flow when EGR is on

2) There is no timing adjustment when EGR is commanded on. However, the base timing map is certainly set assuming EGR to be functional. I have posted the timing map here http://www.supramania.com/forums/showthread.php?73379-3P-s-TCCS-Disassembly-Analysis&p=1712465&viewfull=1#post1712465, and if someone wants to send me a JDM ECU I will extract it and compare.

3) EGR is commanded only for the following conditions. Load < 45%, AFM freq > 48Hz, coolant > 60C, and throttle not closing rapidly. Under these conditions we can expect the knock sense algorithm to pull timing if knock is sensed. Also, under these conditions the fuel mode will be closed loop.

THANK YOU! Finally someone provides some actual FACTS about how the EGR and ECU work together!

 

[Poodles]

Some comments on the ECU control of EGR

1) There is no adjustment of mixture in the ECU code when EGR is turned on. Since this is a type L system any correction to fuel to maintain stoicheometry is already compensated by the AFM which will see a small drop in air flow when EGR is on

2) There is no timing adjustment when EGR is commanded on. However, the base timing map is certainly set assuming EGR to be functional. I have posted the timing map here http://www.supramania.com/forums/showthread.php?73379-3P-s-TCCS-Disassembly-Analysis&p=1712465&viewfull=1#post1712465, and if someone wants to send me a JDM ECU I will extract it and compare.

3) EGR is commanded only for the following conditions. Load < 45%, AFM freq > 48Hz, coolant > 60C, and throttle not closing rapidly. Under these conditions we can expect the knock sense algorithm to pull timing if knock is sensed. Also, under these conditions the fuel mode will be closed loop.

You thought that you could switch between EGR and non-EGR with a resister on the GE ECU, did you ever confirm it for the GTE ECU?

 

[3p141592654]

I confess I dropped the GE analysis and haven't looked at it in a long time. It is true that two resistors controlled the operating mode and one was for sure AT vs M/T. and the other I think was JDM vs USDM (it did disable EGR).

Unfortunately, the *GTE* ECU firmware does not have that feature as there was not enough memory to hold all the maps needed for multiple modes.

 

[Poodles]

Damn, would be nice if it did.

 

[Rollus]

Hi Pi,

First, thank you for your clarifications

Then, for my knowledge, I'd like to go further:

Assuming that:

1) There is no adjustment of mixture in the ECU code when EGR is turned on.[...]

2) There is no timing adjustment when EGR is commanded on. However, the base timing map is certainly set assuming EGR to be functional[...]

and:

I confess I dropped the GE analysis and haven't looked at it in a long time. It is true that two resistors controlled the operating mode and one was for sure AT vs M/T. and the other I think was JDM vs USDM (it did disable EGR).

If they were 2 ignitions table in the GE ECU (do you remember?), I think this should confirm that "the base timing map is certainly set assuming EGR to be functional"
If If they were only 1 ignitions table in the GE ECU, this this

3) EGR is commanded only for the following conditions. Load < 45%, AFM freq > 48Hz, coolant > 60C, and throttle not closing rapidly. Under these conditions we can expect the knock sense algorithm to pull timing if knock is sensed. Also, under these conditions the fuel mode will be closed loop.

I think there is also the EGR Vacuum Modulator is also "mechanically" commanded by the Throttle Valve.



How is the Load% value computed? (I can't find in the TCCS Analysis thread, is this post confirmed?)

++

RolluS

 

[3p141592654]

The GE analysis was terminated before I knew enough to reliably find the timing maps and such. Given very few people are GE enthusiasts, it is not a priority to dig into it.

Load is essentially just volumetric efficiency,

VE = K(P/T) x Vel / RPM
Where:
VE = volumetric efficiency
K(P/T) = constant which varies with air pressure and temperature
Vel = air velocity measured by an AFM

 

[Rollus]

Thanks pi for the answear..

I really think that fuel isn't affected by EGR off, because the gaz which doesn't come from exhaust comes from AFM (no egr, no drop of admitted air, no drop of fuel).

As you've already told:

1) There is no adjustment of mixture in the ECU code when EGR is turned on. Since this is a type L system any correction to fuel to maintain stoicheometry is already compensated by the AFM which will see a small drop in air flow when EGR is on

and I've found a nice explanation from Reg Riemer here:

The total amount of fuel injected into the engine is calculated in a number of steps by the TCCS. The air flow meters square wave signal as well as RPM, air temp, coolant temp & throttle position are all calculated to determine the initial pulse width value for fuel delivery under the present conditions. This initial calculation or best educated guess is called the BASIC FUEL CALCULATION. It is used as the starting point for the amount of fuel that is injected into the engine.

When the TCCS is controlling the BASIC FUEL CALCULATION on the fly to accommodate the rapidly changing engine conditions it is using input data from the oxygen sensor. When the TCCS is LEARNING about the amount of fuel correction that is taking place under the engines operating range It is watching and learning what is taking place with the fuel requirements.

By using a system called LEARNED VALUE {Vf} or the FUEL TRIM correction system. The TCCS uses its best guess or BASIC FUEL CALCULATION plus a +/- 40% floating correction factor determined by the LEARNED VALUE Vf system to give the engine the correct required amount of fuel under all conditions. In short, a very smart and well designed system indeed.

This + or - correction amount is controlled by an active control system in the TCCS called the LEARNED VALUE SYSTEM, Vf fuel trim. Under this system the TCCS uses two types of fuel trims called the long and short fuel trims.

The LEARNED VALUE Vf system is used by the TCCS during both open and closed loop operation to fine tune the fuel control to the engine in relation to engine wear, sensor shift and other problems such as combustion leaks and intake air leaks.

This long and short fuel trim is an automatic on the fly correction system that uses the engines sensors to add or subtract fuel from the BASIC FUEL CALCULATION to keep the fuel mixture going out the tail pipe on target under the fast and slow changing engine conditions, examples: Hot, Cold, idling, redline, wear in cylinders and head, or any number of engine operation conditions.

The current amount of fuel correction the long and short fuel trims systems are adding or decreasing from the BASIC FUEL CALCULATION can be read by reading the voltage coming out of the TCCS's Vf data output terminal in the diagnostics connector under the hood of the Supra. The Vf line feeds five stepped voltage values of 0,1.25, 2.5, 3.75, 5.0 volts. Each step in voltage is an indication of the amount of fuel trim to the BASIC FUEL CALCULATION that is taking place.

This tend to tell us that fuel should be correctly corrected (or not corrected for egr)..

Problem could be ignition...but

On Pi analysis, EGR VSV depends of Load and Velocity.
On the table from TSRM (post #50), EGR vacuum modulation depends on Throttle.
On the ignition timing map and description of from Pi, there is no correction of the advance according to throttle position (there is warmup, cranking, to hot, idle, and A/C)

If all data are here and if I've understood it, I would like to think that EGR gaz are not took in account to compute corrections.

++

 

[CyFi6]

I think the point 3p was making was that in the GTE USDM ECU there are no corrections for EGR flow, but the base timing map is formulated in a way that it relies on and expects EGR flow (correct me if I am wrong).

 

[Rollus]

I was thinking the same for the timing map, but:
- EGR is ON or OFF from the ECU, and ECU knows that.
- EGR flow is not constant and depends on throttle angle, intake vacuum, and exhaust pressure
that bring me to think that the ECU doesn't seem to take account of throttle angle in its correction or in the map, it doesn't know exhaust pressure. perhaps that throttle angle and manifold air pressure are enough, but their would be an egr flow map then.
If EGR flow was integrated in the timing map, even a modded exhaust would change the data that base timing calculation relies on...

So I doubt egr flow is assumed by the ECU, but just what 3p explain in this post: http://www.supramania.com/forums/sh...bly-Analysis&p=1712465&viewfull=1#post1712465

I may be all wrong, just trying to feed the thread with my (maybe bad) ideas.

 

[jetjock]

What Cy said.

Although there's a lot more to it Reg Riemer's "explanation" is lifted word for word from one of the factory technical manuals. I know because it's one of a half dozen TCCS books I have in my library. It happens to be the same manual the information in post #19 came from.

 

[Nick M]

So your saying when the EGR is active, the ecu advances the timing to make up for the loss of fuel. So when its not active or blocked off, there is more fuel. So my question is, how can disabling it cause detonation?

The fuel determined is from the load and rpm sensors. EGR displaces air, not fuel. Causing a very light stumble compared to not having it. This lowers combustion temps and NOx. This thread is up to more than 50 posts now and should have been answered.

 

[Rollus]

The fuel determined is from the load and rpm sensors. EGR displaces air, not fuel. Causing a very light stumble compared to not having it. This lowers combustion temps and NOx.

Air velocity is a part of load.
When EGR is blocked, the air which isn't displaced by EGR is seen by AFM as pi said:

1) There is no adjustment of mixture in the ECU code when EGR is turned on. Since this is a type L system any correction to fuel to maintain stoicheometry is already compensated by the AFM which will see a small drop in air flow when EGR is on

Because the drop in air flow is seen, stoicheometry (amount of fuel per AFM metered intake air), remains the same with or without egr. I think we are sure of that now.

In fact, I understand that air from EGR is completly inerted, there is an heat exhange between egr gaz and exploding air/fuel.
It's just like reducing the combustion chamber volume in terms of power. We can consider that when EGR is opened, it's like having a smaller displacement engine, which runs colder.

The ignition timing correction w/ or w/o EGR remains misunderstood for me ATM.

++

 

[Nick M]

Air velocity is a part of load.

Right.

When EGR is blocked, the air which isn't displaced by EGR is seen by AFM

right.

Because the drop in air flow is seen

Right. The fuel isn't changed from EGR, it is changd from the load and speed.

In fact, I understand that air from EGR is completly inerted, there is an heat exhange between egr gaz and exploding air/fuel.

Right. It doesn't increase detonation like the myth that rumored the Supra community for a long time and wouldn't go away. It is inert.

 

[3p141592654]

That is all correct. Now consider the purpose of the EGR modulator and related vacuum circuits. The ECU can only command EGR on or off. It is the job of the modulator to ensure the correct blend of recirculated exhaust for the range of operating conditions where it is normally on.

The ECU timing map assumes that the EGR dilution is a set amount (thanks to the EGR modulator) for the given load and rpm, and therefore the timing will be appropriate for the expected amount of dilution. That is why there is no feedback between the timing and the EGR system.

 

[Rollus]

Sounds logic, thanks Pi for your explanations

To conclude this thread, we can say that for those who wanna go EGRless a fuel management piggyback isn't necessary.
An ignition piggyback may be recommanded.

BTW Pi,can you please confirm that knock correction of TCCS will be efficient enough or not?
What kind of timing issue would guys without EGR and with TCCS may have?

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