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Post by lanceslambos on Apr 6, 2012 8:34:38 GMT -6
many of us look for every scrap of power we can find so after seeing sall's question on the matter, i thought this would make for be an educational thread:
the claim - blocking off the EGR increases fuel economy and gains horsepower by dropping intake temps.
certainly that's possible but is unlikely to add much. if anything it might have the opposite effect on our cars. this is an old school trick and is more suitable for turbo diesels and / or cars running NOS. but may be fairly worthless on cars with computers.
in theory it makes sense, as hot recycled gases are forced back into the intake. however, this mod won't work without a proper cat. the ECM adjusts fuel and spark according to MAF, MAP, IAT & O2 readings. if your cat is hollowed out like mine and others here, the brain is already seeing a rich condition (even though the engine is not actually running rich, it's just not burning up the waste inside the cat)
i have done a good bit of online research on this and found information by some camaro guys that claimed as much as a 10 degree drop in engine temps, and at the same time, an increase of 1 - 1.5 mpg it's hard to say how much actual power was gained but sometimes it can lose power too.
the EGR is really more of an environmental protection system just like the cat. but, it is also there to save your engine in times of running lean. some car techs claim egr delete can hurt the motor over an extended time. others say it won't make any bit of difference. one thing is certain though, an EGR delete can create engine knock or rather amplify it.
the benefits vs disadvantages are about as abundant or rather back and forth as a political or religious debate. if the EGR delete creates a knock, just up the fuel grade. if the ECM needs the EGR to control proper fuel mix, why mess with it? & on and on, etc. etc. it's actually an easy to do manually job, or one can have (at least 90-92 GM) The brain flashed to compensate.
will it throw a code? most likely. without going through the hundreds of codes our cars can throw; there is a code (i cant recall the #) having to do with the EGR system. i know this because my car threw it last summer. when i looked it up, it had to do with a valve off the gas tank which takes fumes that build up in the gas tank and runs it back to the intake. separate system? yes and no as they work together.
i have heard it's a fairly useless mod on OBD I & II cars. i have also read it's useless on OBD I but not OBD II. in fact, i have found conflicting information all around the board. some claim that it can only be beneficial to brain controlled cars, some claim just the opposite.
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Post by sall on Apr 6, 2012 9:00:29 GMT -6
lol must have saw my question to Shelby yesterday. I see info all across the board too. With no concrete conclusions.
I know 'the brain' had completed an egr delete on one of his classics. I'll shoot him an email and see if he has a good answer for us.
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Post by lanceslambos on Apr 6, 2012 9:10:09 GMT -6
you're quick on the draw man! i think the bottom line is you'd have to see some very specific engine parameters within the ECM. i mean you'd really have to know what you're doing because surely by switching octane level or by going to hotter or colder plugs, you could find the advantage, otherwise not.
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Post by shelbyracing on Apr 6, 2012 12:18:38 GMT -6
It reduces nox and let's exhaust gas enter intake increasing fuel economy, but consequently reducing power. I have mine on and took the plates off. I would want it tuned out if I were to remove it as the engine is programmed for it. Less oxygen in intake equals less power and more fuel mileage and vice versa.
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Post by wireless on Apr 6, 2012 12:37:46 GMT -6
When I was consulting Westers, this is what he told me. He asked if I would like to disable the EGR, and I said I didn't know if I should or not, and what his opinion was..  |
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Post by ntrenn on Apr 6, 2012 13:07:47 GMT -6
Not sure where these guys got their engineering degrees, but the whole purpose of EGR is to reduce combustion temperatures so that the cylinder temperatures don't run in the range that is favorable to NOX production - typically in the 1800-2200 F range. When the NOX leaves the cylinder and cools, even slightly, it freezes in the NO and NO2 state.
EGR generally hurts fuel economy and power production, but greatly reduces the amount of NOX that the catalyst needs to convert to N2. A better, but still illegal strategy on EGR control is to turn it off at throttle positions above say, 50%. You then keep the emission control strategy in place for normal driving and during any smog tests, but when you need full power, you have the power but not the EGR.
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Post by Marc on Apr 6, 2012 14:31:18 GMT -6
I think that the EGR cuts out at WOT. It shouldn't have any effect on maximum power output. If I'm wrong about that, let me know!
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bobsblue95
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Post by bobsblue95 on Apr 6, 2012 17:04:42 GMT -6
I think that the EGR cuts out at WOT. It shouldn't have any effect on maximum power output. If I'm wrong about that, let me know! Same thing with the A/C compressor. Turns off under WOT, which is kinda cool. |
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Post by ntrenn on Apr 6, 2012 18:53:18 GMT -6
I think that the EGR cuts out at WOT. It shouldn't have any effect on maximum power output. If I'm wrong about that, let me know! Marc - it all depends on how picky the EPA is with the programming. They busted the diesel engine guys because they turned off their emission controls when the engine was in long runs, but it really helped with the fuel economy. There have been enough consent decrees about when the computer turns off the emission controls that one never knows unless you actually pull the code and examine it. You have about a 50/50 chance of being right. It may actually vary from year to year.... |
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Post by nelson480 on Apr 7, 2012 0:42:01 GMT -6
If you really want to decrease intake temps and add true cold air, disable the coolant that runs through the throttle body. It will destroy your fuel economy but you'll gain about 10hp
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Post by shelbyracing on Apr 7, 2012 7:23:28 GMT -6
That coolant is to cool your TB from the heat the egr adds.
Egr reduces exhaust temp not intake. Less power is less btu's.
I also believe it is closed at wot. It would actually benefit fuel mileage if it flowed more at low throttle position. I get a little less mileage having less back pressure in my exhaust because of that.
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Post by caleditor on Apr 7, 2012 9:29:22 GMT -6
The EGR is put in place to lower combustion chamber temperatures by lowering the compression ratio. The inert gas will lower the compression ratio at an unequeal amount. The rate and amount is not metered also. The EGR is the only emissions device the hurts MPG and performance. This is why you won't find them on most cars any more.
If you understand what MBT is then you would know why an EGR is bad.
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Post by caleditor on Apr 7, 2012 9:45:22 GMT -6
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Post by ntrenn on Apr 7, 2012 17:45:06 GMT -6
Compression ratio does not change, ever.
EGR typically is used at higher loads. When it is introduced at low loads and speeds, it really messes with the driveability - just ask anybody that ever had an EGR pintle stick in the open position.
In the newer vehicles, they have added tons of cost primarily to control emissions while maintaining performance and improve fuel economy. EGR was cheap and easy.
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Post by caleditor on Apr 7, 2012 18:03:18 GMT -6
The EGR valve lowers the compression ration by allowing an inert gas into the combustion chamber this intern lowers the combustion chamber temps and this lowers NOx
I am not sure how you could not understand that
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Post by shelbyracing on Apr 7, 2012 19:03:22 GMT -6
It is not direct injection, it is introduced through the intake manifold displacing oxygen and fuel. It reaches the combustion chamber thereafter.
If there was a direct injected egr it would create less heat in the intake, be cleaner, and it would be able to change compression in the cylinder.
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Post by lanceslambos on Apr 12, 2012 9:17:18 GMT -6
If you really want to decrease intake temps and add true cold air, disable the coolant that runs through the throttle body. It will destroy your fuel economy but you'll gain about 10hp since this made no sense to me, i did some research online. this mod is like the EGR delete, i find arguments back and forth. bypassing the TB in theory won't really lower the temp, since air coming in is moving so fast that the air particles aren't in there long enough to really heat up much at all. (if any) if a person who lives in cold areas did this mod, it could cause the TB plate to freeze. if that happens, all you have to do is turn the car off a few minutes (if it was warmed up) or to avoid this problem, let the car warm up before driving it. it's disadvantage is taking longer to warm the car up and a rough or choppy idle until it is up to temp. 10 hp is dreaming though. a few people have supposedly tested this mod on a dyno. a stock 305 saw 1-2 hp gain. thinner oil will gain more than that lol & a built 350 actually saw 5 hp at the rear wheels. that was the biggest gains i found online. it seems that the only real advantage may be faster coolant circulation, since the intake will surely heat up on it's own as under the hood temps increase. a lower thermostat makes more sense to me. even better, just pull the engine cover off or run water wetter in your coolant. |
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Post by poofables on Apr 19, 2012 14:33:53 GMT -6
OK, first off. The only way to change the compression ratio on a car is to change engine internals (head, piston, con rod, crank). All the EGR does is exactly what it's name implies. It recirculates exhaust gasses in an effort to reduce NoX. That's all. Because of this though it can cause the intake manifold to get dirty (look at the back side of your throttle butterfly). As far as power and fuel economy go, if it does have an effect, it will be minimal. Just disconnect the electrical connector and try it off, and try it on. See which way you like better. It's going to throw a code and you won't pass e-check with it disconnected though.
As far as the coolant lines running to the throttle body, those are in place to keep it from icing up in the winter. They keep it warm, not cold. The EGR injects the gasses behind it anyways (downstream).
The post-cat oxygen sensor does not have any role in engine management. It's only purpose is to monitor emission levels after the cat. Your up stream o2 sensors which are on each exhaust manifold and your pre cat down stream are the ones that monitor air fuel ratio etc. If you remove your cat, remove b2s2 and plug off the hole.
Just register your vehicle in a non emissions controlled area and remove all emissions equipment and take the CEL bulb out. IMO it gives the engine a more responsive feel, but you aren't going to see a difference in numbers at the track by disconnecting your egr. True story.
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Post by caleditor on Apr 19, 2012 16:14:32 GMT -6
OK, first off. The only way to change the compression ratio on a car is to change engine internals (head, piston, con rod, crank). All the EGR does is exactly what it's name implies. It recirculates exhaust gasses in an effort to reduce NoX. That's all. Because of this though it can cause the intake manifold to get dirty (look at the back side of your throttle butterfly). As far as power and fuel economy go, if it does have an effect, it will be minimal. Just disconnect the electrical connector and try it off, and try it on. See which way you like better. It's going to throw a code and you won't pass e-check with it disconnected though. As far as the coolant lines running to the throttle body, those are in place to keep it from icing up in the winter. They keep it warm, not cold. The EGR injects the gasses behind it anyways (downstream). The post-cat oxygen sensor does not have any role in engine management. It's only purpose is to monitor emission levels after the cat. Your up stream o2 sensors which are on each exhaust manifold and your pre cat down stream are the ones that monitor air fuel ratio etc. If you remove your cat, remove b2s2 and plug off the hole. Just register your vehicle in a non emissions controlled area and remove all emissions equipment and take the CEL bulb out. IMO it gives the engine a more responsive feel, but you aren't going to see a difference in numbers at the track by disconnecting your egr. True story. #1 the EGR actually does change the compression ratio, but not the static compression ratio. You can find many SAE paper about how an EGR system works, or you could take a course at a engine management university like the one at Madison WI #2 the post O2 sensor actually does play a role in the engine management. Do some good research or you could ask for the documents No reason to explain why the post O2 sensors would have an effect on the engine management if you don't understand how an inert gas would effect the compression ratio. On way to look at it is that the post O2 works with the PCM to make the Cat last longer and not cause any damage to it. Cat Over Temp is just one way |
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Post by ntrenn on Apr 19, 2012 21:48:52 GMT -6
Caleditor - I think you are mixing up a couple of terms - there is what is identified as effective compression ratio and actual compression ratio. The compression ratio is the ratio of volumes of the cylinder at BDC divided by the volume of the cylinder at TDC. Those volumes are fixed at the factory when they build the engine and size the cylinder head volume. You cannot change the compression ratio on any standard internal combustion engine without changing critical mechanical dimensions. That takes a teardown.
There have been engines built that had variable compression ratios but they have not found favor in the commercial realm.
It's been a long time since I took ME440 - internal combustion engines - but the definition of compression ratio has not changed since then.
Additionally, exhaust gases are not inert - that designation is limited to Argon, and it's brothers in the Noble gas column of the periodic table. They are, however, spent gases that replace a portion of the intake charge with non-combustible gases, which lowers the 'effective' compression ratio, as there is less combustible gas mass in the chamber and less power is produced due to the partial combustible charge.
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Post by caleditor on Apr 20, 2012 5:40:58 GMT -6
Compression Ratio = The volume of the cylinder at the bottom of the stroke VS the volume when the piston is at the top of the stroke --- Correct?
If you displace the initial volume with an inert gas then recalculate the CR it will be lower Correct?
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Post by ntrenn on Apr 20, 2012 6:38:15 GMT -6
Nope...the volume of gas will be the same, it just will have a different composition. The electron boys need to adjust their fueling to account for the composition.
What the emissions guys are trying to do is to limit the NOX formation (danged EPA). When you mix in the exhaust gases, it affects the burn rate in the cylinder and hence the peak temperatures in the cylinder. If you can slow the burn and extend it over a longer period of time without EGR, then you accomplish the same thing without the detrimental effects of EGR.
I continue to be amazed at what has happened to engines over the last 10-15 years. They have gotten 90% cleaner, get WAY more HP/cylinder, and still get better mileage. That's mostly due to manufacturing precision, but the controls have gone a long way toward helping too.
Our engines are 1.02 HP/cu in. That used to be the holy grail of engine building. There are cars out there now in NA form that are way over that. The econobox Cruze is at 1.26 HP/cu in. My GN with a turbocharger was only 0.82 in 1984.......
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Post by genone on Apr 20, 2012 6:57:11 GMT -6
The EGR is put in place to lower combustion chamber temperatures by lowering the compression ratio. The inert gas will lower the compression ratio at an unequeal amount. The rate and amount is not metered also. The EGR is the only emissions device the hurts MPG and performance. This is why you won't find them on most cars any more. If you understand what MBT is then you would know why an EGR is bad. Ding ding ding. Tell him what he won. |
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Post by poofables on Apr 20, 2012 7:14:53 GMT -6
Caleditor - I think you are mixing up a couple of terms - there is what is identified as effective compression ratio and actual compression ratio. The compression ratio is the ratio of volumes of the cylinder at BDC divided by the volume of the cylinder at TDC. Those volumes are fixed at the factory when they build the engine and size the cylinder head volume. You cannot change the compression ratio on any standard internal combustion engine without changing critical mechanical dimensions. That takes a teardown. There have been engines built that had variable compression ratios but they have not found favor in the commercial realm. It's been a long time since I took ME440 - internal combustion engines - but the definition of compression ratio has not changed since then. Additionally, exhaust gases are not inert - that designation is limited to Argon, and it's brothers in the Noble gas column of the periodic table. They are, however, spent gases that replace a portion of the intake charge with non-combustible gases, which lowers the 'effective' compression ratio, as there is less combustible gas mass in the chamber and less power is produced due to the partial combustible charge. Well said. I was about to post something similar. I'm just as blown away as you with modern engine accomplishments. Think that v6's now are making far more power than a v8 was 10 years ago, and they are getting the fuel economy that the 4's were! Car makers have been forced to become so good at what they do. The engines have become so efficient and are continuing to improve quickly. Look at what Mazda did with their skyactive "technology", there is nothing technology about it, they just have moved the internal combustion engine closer to its absolute potential by using existing technologies and methods. Beautiful. Truly an exciting time to be in the automotive field. |
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Post by genone on Apr 20, 2012 7:24:46 GMT -6
Honestly my favorite new engine is the Ford Ecoboost family. Direct injection, high output turbo, crazy power and excellent economy. All while producing nil emissions.
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Post by poofables on Apr 20, 2012 7:31:01 GMT -6
OK, first off. The only way to change the compression ratio on a car is to change engine internals (head, piston, con rod, crank). All the EGR does is exactly what it's name implies. It recirculates exhaust gasses in an effort to reduce NoX. That's all. Because of this though it can cause the intake manifold to get dirty (look at the back side of your throttle butterfly). As far as power and fuel economy go, if it does have an effect, it will be minimal. Just disconnect the electrical connector and try it off, and try it on. See which way you like better. It's going to throw a code and you won't pass e-check with it disconnected though. As far as the coolant lines running to the throttle body, those are in place to keep it from icing up in the winter. They keep it warm, not cold. The EGR injects the gasses behind it anyways (downstream). The post-cat oxygen sensor does not have any role in engine management. It's only purpose is to monitor emission levels after the cat. Your up stream o2 sensors which are on each exhaust manifold and your pre cat down stream are the ones that monitor air fuel ratio etc. If you remove your cat, remove b2s2 and plug off the hole. Just register your vehicle in a non emissions controlled area and remove all emissions equipment and take the CEL bulb out. IMO it gives the engine a more responsive feel, but you aren't going to see a difference in numbers at the track by disconnecting your egr. True story. #1 the EGR actually does change the compression ratio, but not the static compression ratio. You can find many SAE paper about how an EGR system works, or you could take a course at a engine management university like the one at Madison WI #2 the post O2 sensor actually does play a role in the engine management. Do some good research or you could ask for the documents No reason to explain why the post O2 sensors would have an effect on the engine management if you don't understand how an inert gas would effect the compression ratio. On way to look at it is that the post O2 works with the PCM to make the Cat last longer and not cause any damage to it. Cat Over Temp is just one way Calender, a few things that ntrenn missed that I wanted to touch on. I think that when you are talking about compression ratio, you are actually talking about the volume of the combustible mixture in the cylinder. No matter how much is in there, it will still be compressed the same amount. However, if there is more volume in the cylinder the pressure of the compressed mixture will be higher. Regardless, the EGR will not affect this, the EGR is basically a passive system. It is not a forced induction system like a turbo charger or supercharger. there will still be a vacuum (negative pressure) in the intake manifold with or without the EGR. Watch the output of a MAP sensor as you disconnect and reconnect an EGR. Again, the post cat o2 sensor does not affect engine management. It's basically just the babysitter for the emissions system. You are right in saying that it is in place to make the cat last longer and to make sure it doesn't over heat. However it does this only by letting the user know that there is a problem that could damage the cat via the check engine light. I am sure there are plenty of articles out there on this, or you could talk to someone who is into cars or take that class you mentioned if you don't want to take my word for it. |
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Post by caleditor on Apr 20, 2012 8:47:43 GMT -6
#1 the EGR actually does change the compression ratio, but not the static compression ratio. You can find many SAE paper about how an EGR system works, or you could take a course at a engine management university like the one at Madison WI #2 the post O2 sensor actually does play a role in the engine management. Do some good research or you could ask for the documents No reason to explain why the post O2 sensors would have an effect on the engine management if you don't understand how an inert gas would effect the compression ratio. On way to look at it is that the post O2 works with the PCM to make the Cat last longer and not cause any damage to it. Cat Over Temp is just one way Calender, a few things that ntrenn missed that I wanted to touch on. I think that when you are talking about compression ratio, you are actually talking about the volume of the combustible mixture in the cylinder. No matter how much is in there, it will still be compressed the same amount. However, if there is more volume in the cylinder the pressure of the compressed mixture will be higher. Regardless, the EGR will not affect this, the EGR is basically a passive system. It is not a forced induction system like a turbo charger or supercharger. there will still be a vacuum (negative pressure) in the intake manifold with or without the EGR. Watch the output of a MAP sensor as you disconnect and reconnect an EGR. Again, the post cat o2 sensor does not affect engine management. It's basically just the babysitter for the emissions system. You are right in saying that it is in place to make the cat last longer and to make sure it doesn't over heat. However it does this only by letting the user know that there is a problem that could damage the cat via the check engine light. I am sure there are plenty of articles out there on this, or you could talk to someone who is into cars or take that class you mentioned if you don't want to take my word for it. The GM training and the SAE papers that I read over are not correct? The post O2 sensors can offset the way the PCM fuels the engine. Do you have proof that they don't? email me and I will send you some information stating that it does caleditor@pcmcalibrators.com |
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Post by caleditor on Apr 20, 2012 9:03:35 GMT -6
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Post by poofables on Apr 20, 2012 9:26:07 GMT -6
The article is only about how EGR affects A/F, which is measured pre-cat. It wouldn't be a reliable reading from a post cat o2 sensor. |
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Post by caleditor on Apr 20, 2012 9:34:35 GMT -6
The article is only about how EGR affects A/F, which is measured pre-cat. It wouldn't be a reliable reading from a post cat o2 sensor. Correct I was searching out EGR and SAE paper when I found that article. When you purchase the SAE papers you are not allow to redistribute them. I have GM technical papers on the post O2 sensor effect on engine management |
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