Before I start I just want to say that this is an honest attempt to educate myself and hopefully contribute to the community about what seems like the never-ending debate of whether or not it is beneficial to block/unplug the EGR. I've already learned so much from the TL enthusiasts on here and I will thank ahead of time those more knowledgeable and experienced than me who will contribute to this discussion.

I didn't want to derail the other EGR thread right now and so I elected to start my own after seeing OP's request to not derail his thread since he was talking about a different/specific EGR issue as it relates to the ECU.

But after reading comments in that thread about the benefits of EGR block/unplug, I got curious and I searched the 3G TL forum for EGR threads. (I just searched thread titles with "EGR" in the 3G TL section)

Basic facts that I (think) understand about the EGR:
EGR functions mainly to reduce NOx emissions at partial/mid-range throttle

EGR does the above by letting exhaust gas recirculate into the intake, reducing cylinder temp and this reduces emissions.

EGR also has beneficial side effect of helping to protect against pre-detonation in our high CR motor (11:1) due to the lower temp

EGR is a non-issue at idle and WOT

If the EGR is intentionally blocked/unplugged/deleted. There is a difference in opinion regarding if this causes more good than bad or vice versa.

As far as I understand the debate, if EGR is deleted, it can improve mid-range/partial throttle response. However there is a counter-opinion that the ECU will notice the hotter temp and thus ECU will pull back timing to prevent knocking thereby negating any "free HP" gains. And also EGR delete may actually cause motor to be more prong to knocking unless higher octane/quality gasoline is used, thereby causing causing more headaches for the minimal, if any power gains.

Again I do not claim to be an expert, this is what I've distilled in my mind after reading several threads regarding this issue and I wanted to see what the opinion is on this issue these days.

Please feel totally free to correct any mis-understanding/mis-information in my post.


Pro EGR delete:
source: https://acurazine.com/forums/third-g.../#post15190434


EGR not even used in certain outside countries:
source: https://acurazine.com/forums/perform.../#post10703323


Anti EGR delete:
source: https://acurazine.com/forums/perform.../#post10653840



Modern ECU's not affected by "crude" EGR delete:
source: https://acurazine.com/forums/perform.../#post10702376


ECU may need to be tuned/chipped/burned/etc. to change timing map, otherwise simple EGR delete may result in knocking:
source: https://acurazine.com/forums/perform.../#post10713304


If nothing else, it will cause annoying CEL to come on:
source: https://acurazine.com/forums/perform.../#post14891815


Annoying for those needing to pass smog tests and no real practical daily gains:
source: https://acurazine.com/forums/perform.../#post14919285



So basically my own personal question would be: If I just bought a base TL and I'm looking at something that can potentially improve partial throttle response (which will be a majority of my driving, I doubt I'll be WOT too much) then is there any practical gains to be had from deleting the EGR in the 3G TL?

And will the car need significantly higher octane/knocking protection?

Or will this not even matter because modern ECUs are too "smart" for this apparently simple and cheap trick?


Source/reference threads:
https://acurazine.com/forums/third-g...ugging-919277/
https://acurazine.com/forums/perform...ck-off-784470/
https://acurazine.com/forums/perform...ck-off-715349/
https://acurazine.com/forums/perform...delete-905780/
https://acurazine.com/forums/perform...ye-egr-729573/

 

I'll be back in a few hours to break it down but over the past year with no EGR and after monitoring for knock, and the vastly improved drivability and part throttle power, I'll never enable the EGR on the TL again other than for smog checks. One thing to mention, my car actually has less knock without the EGR functioning.

 

My car doesn't have any knock with EGR functioning.

 

^^ yeah ok! thats rediculous this car knocks easily

 

Here is a link to a thread where I tried to make this car knock using 87 octane. It was not easy.

https://acurazine.com/forums/third-g...ok-use-907704/

Honda makes crappy engines that knock easily and last forever. I think something doesn't make sense in this statement.

 

Dang, well then if this is the case I shall also look into unplugging the EGR if there is only gains to be had and no knocking!

I"ll be going to a local BP that has 100% gasoline fuel at 93 ocatne!

Well that should be the case....the theory is that with EGR delete there may be increased risk of knocking.

But I would not use 87 octane in the TL. The reason it's NOT knocking with 87 octane may just be because the TL has a good knock sensor and the ECU is pulling the timing back far enough to prevent the knock. But I don't think it would be a good idea to use that for long-term. Sure if you're stranded out in the Arizona desert highway then yeah any fuel would do to get you to the next gas station but otherwise I don't know if I want to use 87 octane regularly.

In fact I am going to use a loca BP station with 93 octane that's also 100% gasoline

 

What's probably happening with the EGR being non functional is timing is lower. EGR causes a loss in power so to partially make up for it, just about every manufacturer bumps the timing a few degrees when EGR is on. This timing bump likely does not occur once the EGR is declared non functional by the ECU. I have a feeling in some cases Honda might have overdone the timing bump which is why mine runs better and with no knock with no egr.

Remember, this is an emissions device. It would not exist without emissions testing and does not exist in some cases on the same model sold elsewhere. Engineers have done a good job of mitigating the downsides to EGR but there is no upside other than emissions. Some more advanced setups are using cam phasing to control NOx with a sort of natural EGR effect rather than running exhaust gas through the intake manifold.

 

^^^ Sounds good. On one of the accord forums I read someone mentioning that blocking the EGR is better than simply unplugging it? I think the poster mentioned something like there will be a cascade of things going on in the ECU if you simply unplug the EGR. Is there a difference between the two methods or would unplugging do the same job? I'd rather not have to spend the extra cash (even if its ilke $20) if I can simply unplug and go.

 

Anyone know of a mod to defeat the CEL other than tuning? Like a resistor or something? I'd delete mine if I didn't have a CEL, my emissions are plug in only, just wouldn't want to look at the CEL every day, my last Chevy DD always had lights on the dashboard, drove me crazy.

 

Citation:

Kumano, K. and Yamaoka, S., "Analysis of Knocking Suppression Effect of Cooled EGR in Turbo-Charged Gasoline Engine," SAE Technical Paper 2014-01-1217, 2014, doi:10.4271/2014-01-1217.


The cooled EGR system has been focused on as a method for knocking suppression in gasoline engines. In this paper, the effect of cooled EGR on knocking suppression that leads to lower fuel consumption is investigated in a turbo-charged gasoline engine.
First, the cooled EGR effect is estimated by combustion simulation with a knock prediction model. It shows that the ignition timing at the knocking limit can be advanced by about 1 [deg. CA] per 1% of EGR ratio, combustion phasing (50% heat release timing) at the knocking limit can be advanced by about 0.5 [deg. CA] per 1% of EGR ratio, and the fuel consumption amount can be decreased by about 0.4% per 1% of EGR ratio.
Second, the effect of cooled EGR is verified in an experimental approach. By adding inert gas (N2/CO2) as simulated EGR gas upstream of the intake pipe, the effect of EGR is investigated when EGR gas and fresh air are mixed homogeneously. As a result, the ignition timing at the knocking limit is advanced by 7 [deg. CA] and the combustion phasing at the knocking limit is advanced by 5 [deg. CA] when the EGR ratio is 8%, which proves the validity of the simulation result. Next, by introducing the actual EGR gas in two ways, low pressure EGR and high pressure EGR, the effect of EGR mixing conditions is investigated. The result shows that the effect on knocking suppression is nearly the same in all conditions, but the effect on fuel consumption differs because of the combustion speed difference. Furthermore, EGR drastically decreases the exhaust gas temperature. Therefore, under high engine speed condition, the maximum boost pressure, which is limited by the maximum allowable exhaust gas temperature, is improved at higher EGR ratios, so the maximum torque increases by 1.5% per 1% of EGR ratio.

 

EGR dilution is a promising way to improve fuel economy of Spark-Ignited (SI) gasoline engines. In particular, at high load, it is very efficient in mitigating knock at low speed and to decrease exhaust temperature at high speed so that fuel enrichment can be avoided. The objective of this paper is to better understand the governing mechanisms implied in EGR-diluted SI combustion at high load. For this purpose, measurements were performed on a modern, single-cylinder GDI engine (high tumble value, multi-hole injector, central position). In addition 0-D and 1-D Chemkin simulations (reactors and flames) were used to complete the engine tests so as to gain a better understanding of the physical mechanisms.
EGR benefits were confirmed and characterized at 19 bar IMEP: net ISFC could be reduced by 17% at 1200rpm and by 6% at 5000rpm. At low speed, knock mitigation was the main effect, improving the cycle efficiency by a better combustion phasing. At high speed, stoichiometric operation could be achieved, avoiding fuel-costly enrichment. It was also observed that the EGR tolerance decreases with the engine speed: maximum EGR rate was over 30% at low speed, vs. 22% at high speed. EGR composition was varied using synthetic EGR (N2, CO2 or a mixture of N2 & CO2) in order to control the diluent heat capacity (Cp). These results, coupled with Chemkin simulations showed that the Cp value of the diluent is the main driving mechanism that explains the better auto-ignition resistance of the diluted air-gasoline mixture. The Cp of the diluent is also the 1st order parameter that controls the laminar flame-speed (SL), chemical effects being of 2nd order and mainly attributed to CO2, which is implied in many elementary reactions of the fuel oxidation process. Then equilibrium constants can be modified when CO2 concentration varies. However the relative importance between thermodynamic (Cp) and chemical effects of the diluent greatly depends on the ambient temperature and pressure conditions. A split-of-losses analysis was also performed. It helped to show that a diluent with a high molar Cp has a greater potential to re-phase the combustion, mitigating knock. A side-effect is a significant increase of thermal losses that almost completely balance the combustion phasing gains that can be obtained with a high-Cp diluent. Engine tests and simulations also showed that a minor species like NO, which is present in the EGR gases, can significantly affect the auto-ignition delay of the fresh gases. A maximum reactivity of the fresh gases was observed for approximately 100ppm NO in the intake air/EGR mixture.

 

This paper studies the effect of cooled EGR on fuel consumption and anti-knock performance of a boosted port fuel injection (PFI) SI engine. Experimental results show that the cooled EGR increases the thermal efficiency by 2%∼18% depending on the operation conditions. Compared to low load operations, more improvements of the thermal efficiency are obtained at higher loads, primarily owing to the enhanced anti-knock performance, advanced combustion phasing, elimination of fuel-rich operations as well as reduced heat transfer loss with cooled EGR. The anti-knock performance of cooled EGR provides further potential to improve the thermal efficiency by increasing the compression ratio. To this end, a 1-D thermodynamic model of the engine is built and calibrated using the GT-Power code. A knock prediction correlation considering EGR is developed and validated with the experimental data. The geometric compression ratio of the engine with EGR is optimized by a strategy combining artificial neural networks (ANNs) with genetic algorithm (GA) with the 1-D engine cycle simulations. A further improvement of the thermal efficiency is obtained without significant penalty of the engine torque output performance.

 

Here is another long read, if you have any interest just follow the link

http://www.swri.org/3pubs/ttoday/Sum...n-and-Cool.pdf

 

Now explain in your own words what those papers mean lol.

For anyone with a factory turbocharged TL and cooled EGR, those papers might be relevant. However, we don't have a turbo and we dont have a heat exchanger for the EGR so it's not cooled. EGR reduces power and we can't add more boost to make up for the power loss. All we have is timing and for us we're lucky if we can break even in the power department. Therefore those papers do not apply in the slightest to a TL.

Back to the topic at hand, I went for a drive today with near 90 degree ambient temps and I was surprised at how good it was running. Part throttle power was improved as evidenced by lower shift points. It just felt better with smoother power delivery. It was then I remembered the EGR was disconnected. That's the best way to notice an improvement because it eliminates the placebo effect.

In real life, my TL runs considerably better without EGR. Results may vary by location and octane.

 

That would be an annoying thing. Though hopefully for me I'll just be used to it. No smog testing in my county so that'll be good. But then again for inspection they may not like having a CEL on....so might need to plug back in around safety inspection time anyway.

Good point. At least I'll try experimenting with this EGR unplug once the DMV/insurance paperwork clears and see if I notice any difference.

A confounding variable would be that since the owner I bought it from probably just got any old E10 91...I'll be going to a BP with reportedly E0 93 gas. So that may cause the car to run better anyway. So maybe I'll do half a tank with the 93 and EGR on, then 2nd half tank with 93 with EGR off and see if there's noticeable difference.

Also, how long did it take to plug the EGR back in before the CEL went away? Guessing should be pretty quick right.

 

What was interesting is the CEL came on very quick the first time when I physically blocked it off (just a piece of aluminum barstock crudely cut to the basic shape of the EGR. Aluminum is soft enough to not need an additional gasket as long as it's flat) as soon as I took it down the street. It won't come on until you drive it, mine had been idling about 2 minutes before I drove it. I would say the light came on in under 30 seconds of driving.

When I returned it to normal it took 2 days of normal driving for it to go away. I wasn't sure how long it would take so I hooked it back up a week before my smog check. I remember the next morning on the way to work when I was half asleep and not thinking about EGR how horrible it drove. It's not a drastic difference but it's real considering I noticed a difference when I disabled it and when I enabled it.

Ironically, this time when I disabled it I unplugged it electrically. It took much longer this time to throw a check engine light. In fact, for the first 15 minute drive there was no check engine light. I didn't drive it again until the next morning for work and that was when I noticed the check engine light which I think was on from the moment I started the car.

The reason I blocked it off instead of simply unplugging it the first time was with the hope it might not set off the check engine light. On the old cars you could disable the EGR by blocking it or plugging the vacuum line and the ECU didn't know the difference. The pressure differential sensing EGRs have been around for a long time now so I figured it would throw a check engine light but I did it the hard way (an extra minute lol) on the off chance it might not throw a light which of course was wishful thinking.

What I think is good is the fact that modern cars can sense when there's no flow or obviously if it's unplugged. I think this is the reason there's no detonation. The ECU knows EGR is not functional so it doesn't add the additional timing that it adds when EGR is functional.

Of course, you have the long term benefits of the intake manifold staying much cleaner and since ours is not a cooled EGR, you don't have the hot exhaust gasses heating up the charge air. Basically the intake charge is cooler and more dense without an inert gas taking up space that could be used for power making oxygen.

Around here it gets pretty hot in the summer. Most days have been in the mid to upper 90s with a lot of days pushing 99-102F surprisingly often. These are the days I can feel the difference the most. That's why I said it may vary by location. There's a chance that if you live in a cooler area you may not notice as big of a difference although I can feel the difference in winter, it's just less of a difference. I think in summer the EGR compounds the problem because it's on the verge of pinging already and at least in my car's case, the EGR just isn't enough to counter act the additional timing. Not only do I get a less dense/"contaminated" charge, there's more pinging. One thing about the pinging, it's best to have none in the first place. Once it starts, the ECU has to remove more timing to stop it than if your base timing was low enough that it didn't ping in the first place. This is another reason that if 93 is available to you, you might not feel as big of a difference, more of the subtle difference as I feel in the winter.

For what it's worth, I can't feel a difference between blocking it off and unplugging it. If there is a difference, it's very small.

 

I have no idea why you would not place me on ignore list by now.

 

I hate cars, thanks for your advice and story sharing. I'll update this thread later when I get to do this myself and see about the difference. It's getting colder here so may not be as much but we'll see. But in the summer we do get quite hot here in KC with mid to upper 90s not too uncommong.

Acura-OC, hey man it's all good. We're all here to learn and discuss and debate. I remember some smart man once said....everyone you meet knows at least one thing that you don't. So keep open mind.

 

I'm looking forward to your results, please don't forget to update. I think if EGR helps the majority of us it may become a more common "mod".

I forgot to tell you that my mpg went slightly up without EGR being functional. I don't mention it much because it was 1-1.5mpg which is well within the margin of error for measurement. I did notice a solid 1mpg drop when it was active for the past 2 weeks but I don't believe 2 weeks is anywhere nearly long enough to to call it real. It has now gone back up so that's 3 times now it's tracked the EGR status change. I'm starting to believe there is a true 1-2mpg increase. If there is a difference it's probably due to the lower shift points since I don't have to give it as much throttle for a given acceleration. Still, Im not ready to claim a mpg increase but it might be something to watch.

 

Yup will do. Is the MID MPG monitor good enough? Not sure how accurate those are but tracking it manually would be a pretty PITA. So maybe I'll just use the MID and then maybe reset that (if possible) when I unplug the EGR and change up the variable (or maybe just unplug the battery for a while to reset everything, ha)

I'll definitely report back so this may very well be a free "mod" that people can look into.

Also just as a side note, would this raise the eye brows of the EPA? I mean it is an emissions device and from the "coal rollers" that's been making the news lately...I mean obviously this is probably much less problematic than those diesel truck dudes but not sure about the legality surrounding this "mod?"

 

The MID has been shown to be very accurate. The only problem with it is the resolution, it only reads in whole numbers and not tenths.

Disabling it is definitely not legal. The catalytic converters are good at removing hydrocarbons but not good at NOx. NOx is usually a result of high cylinder pressures and it usually follows throttle opening. It's usually disabled at idle, full throttle, and when the engine is cold with rare exception.

In my case where there is occasional detonation even on 91 octane during the summer (it's not audible but it shows up on the scanner), eliminating the detonation can reduce NOx emissions greatly. When theres detonation, NOx emissions go through the roof. If by chance the elimination of the EGR leads to the elimination of detonation, there's a chance there's not a whole lot more NOx with it disabled.

Of course, much of that is wishful thinking, you will be putting lots more NOx in the air and depending on who you believe (the tree huggers or the more conservative), NOx is an especially bad emission. It reacts with hydrocarbons in the air to help create smog. On the bright side, my TLs last two emissions tests have had zero hydrocarbons but there are already unburned hydrocarbons in the air.

Anyway, I'm just rambling now, half asleep, but looking forward to your results and I would probably just unplug it rather than blocking it off. I have a friend that owns a smog shop, I'll see if I can get him to smog it without the EGR to see just how much more it's putting out but I guarantee its gross polluter status.
One more thing, there's no smell associated with it so no worries there.

 

Bump.

Any more updates to share from the disabled EGR group?

I'm particularly interested in the difference of NOx emissions. While I would love for my car to run a little better by disabling the EGR, my conscience wouldn't be clean due to my contribution of smog.

Also curious, how does the ECU measure the exhaust gas flow? Someone above mentioned the possibility of installing a resistor or something into tricking the ECU that the EGR is functional. While it is more complex than just a resistor, it might be possible to build a component that would trick the ECU into thinking that the EGR is fine. But this depends entirely on how it's monitored.

 

Flow is usually checked by delta pressure. It's looking for a pressure drop from the inlet to the outlet of the valve. I don't see a resistor working because the ECU will be looking for different values. A lot of cars only look for flow but don't care about the rate of flow. In this case you only have on and off delta P values. Some monitor more closely the rate of flow. I have no idea about the TL specifically.

It's been over a year and the car drives great with no EGR. No more slight surge in the powerband at light throttle. No more random pings once ever month or so. It drives much better in the summer and with less change from summer to winter.

The EGR knocks down NOx emissions by diluting the intake air with an inert gas (exhaust) that cools combustion temps at the expense of hp. You can Google NOx emissions for their effect on the atmosphere. They're pretty nasty but before you beat yourself up with a guilt trip, NOx emissions are increased ten fold at full throttle or when there's pinging.