Back in the early '80s, I drove my dad's mid-70's Chevy Nova with the 6 cylinder engine. I disabled the EGR, 'cause back then, everyone knew that the emissions controls robbed power and should be disabled at every opportunity. The car started pinging under moderate load, so I hooked it back up again and the ping went away. Besides the ping, I didn't notice any other change.
Blocking off EGR
- Thread starter SyntheticShield
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Yes, on some cars the engine will ping if the EGR isn't working. That's one of the first things the manual may have you check.
Energy is not lost by compressing the gas. The compressed gas pushes down on the piston with a force equal to what the piston pushed up on the gas (assuming that intake/exhaust valves aren't leaking, and that there is good ring sealing).
You will observe this phenomenon when turning an engine with a breaker bar. Suddenly it gets a bit hard to turn..and then what happens..the engine turns itself without any help from you!
You will also notice, if you ever have the occasion to have your fuel pump take a crap on you in a vehicle with a manual transmission while moving at speed in gear, that engine braking is greatly reduced when you floor the gas pedal in a futile attempt to make the car speed up.
Obviously, flooring the gas pedal increases the amount of useless (without fuel anyway) gases entering the cylinders (and reduces intake manifold vacuum) but the fact that engine braking is reduced when that happens tells a lot about what the effects of increased EGR flow are..and energy losses aren't one of them.
[ February 08, 2005, 02:12 AM: Message edited by: brianl703 ]
Engine braking is not effected by throttle position..Throttle open or closed, makes no difference. "Pumping losses" increase dramaticly as RPM increases, caused soley by reciprocating mass...
Now, would you like to talk about Jake Brakes??
Now, would you like to talk about Jake Brakes??
Yes, engine braking IS affected by throttle position.
In Ford vehicles, the idle air control valve (which is a bypass around the throttle) is fully open when the throttle is open.
When the throttle closes, the fuel is turned off and the idle air control valve closes slowly to gradually increase engine braking. This prevents what Ford calls "lift throttle snatch"..in other words, they want the vehicle to decelerate in a smoother fashion than would be the case if the throttle just slammed shut.
As far as Jake Brakes, here is what one site has to say about how they work.
http://www.straightdope.com/mailbag/mjake.html
"The jake brake slightly opens the exhaust valves when the piston is near top dead center (where ignition normally occurs). On the upstroke, the piston compresses the air in the cylinder to 1/15th its original volume. This creates a lot of drag on the engine. The Jacobs Engine Brake then releases the compressed air, and the energy stored in it, before it can push back on the piston during the downstroke."
Opening the exhaust valve and dumping the compressed air is KEY to the operation of a Jake Brake.
Otherwise, what I've put in bold will happen, and greatly reduce if not eliminate the engine braking effect. This is what happens in a gasoline engine.
Put another way, the energy used to compress the air isn't wasted. It's stored for a short period of time (as potential energy), and unless dumped, will push back on the piston with a force equal to what the piston compressed the air.
More about Jake Brakes:
http://www.bankspower.com/tech_howexhaustbrakeworks.cfm
"Diesel engines control engine speed and power output by throttling the amount of fuel injected into the engine. A diesel has no air throttle. Because it has no air throttle, a diesel engine offers virtually no engine braking when the driver lifts off the accelerator pedal. There just isn’t a pumping loss to retard engine speed as the piston descends on the intake stroke. "
Pumping losses decrease as the load on the engine increases.
RPM has nothing to do with it.
I myself have never had problems with EGR, and there are two reasons I would think twice before removing it:
1)Tampering with vehicle emissions systems can result in a pretty hefty fine.
2)We have emissions inspections here. I'm not talking about the piddly two-speed idle test, either. It's all about Acceleration Simulation Mode (ASM) tests, and a vehicle with a tampered EGR will fail with excessive NOx. (NOx is not tested on the two-speed idle test, so a vehicle with a tampered EGR may still pass).
In the areas of Virginia without emissions inspections, a visual check of the emissions equipment is still done as part of the safety inspection. Removing the EGR valve, blocking it off, or any other tampering (unless hidden very well) will make it fail.
1)Tampering with vehicle emissions systems can result in a pretty hefty fine.
2)We have emissions inspections here. I'm not talking about the piddly two-speed idle test, either. It's all about Acceleration Simulation Mode (ASM) tests, and a vehicle with a tampered EGR will fail with excessive NOx. (NOx is not tested on the two-speed idle test, so a vehicle with a tampered EGR may still pass).
In the areas of Virginia without emissions inspections, a visual check of the emissions equipment is still done as part of the safety inspection. Removing the EGR valve, blocking it off, or any other tampering (unless hidden very well) will make it fail.
But its sooo much fun to tweak a car, LOL. You summed it up pretty good TanSedan. I dont think there is enough evidence to support removing or defeating the EGR. But again, my concern was the effect it supposedly has on TBN depletion of an oil. I would think from making such a statement that Lubrizol would have had some available data to show the contrast, but I didnt see any.
But I think what Im going to do in the mean time is clean out my EGR and see if UOA will show anything. A stabilization in the TBN levels or if the nitration and oxidation numbers may drop. We'll see. I'll be sure to post the UOA's, though Im still about 2000 miles or so from one being due.
Plenty of arguments -- to the good -- as to "why" EGR is bad.
But if it came from the factory that way, just fix it with best quality parts (usually dealer) and put this energy into the stuff that counts:
Planned maintenance (including replacement of components before they wear out);
Dead accurate, true, cost-per-mile of ownership/operation;
Upgrading some systems or components where known better than factory;
Staying on top of it all.
What good is a car that performs poorly at 150k or ten years (whichever arrives first)?
One may argue all day about small-changes-to-factory-designed/installed systems being efficacious, but
in my experience and observation
anything but a weekend toy car is best left in factory tune; and performance crutches avoided.
If it doesn't peform well -- and the expense and dedication of putting aright small problems is irksome -- get another vehicle.
Todays oil/filters can easily handle EGR.
But if it came from the factory that way, just fix it with best quality parts (usually dealer) and put this energy into the stuff that counts:
Planned maintenance (including replacement of components before they wear out);
Dead accurate, true, cost-per-mile of ownership/operation;
Upgrading some systems or components where known better than factory;
Staying on top of it all.
What good is a car that performs poorly at 150k or ten years (whichever arrives first)?
One may argue all day about small-changes-to-factory-designed/installed systems being efficacious, but
in my experience and observation
anything but a weekend toy car is best left in factory tune; and performance crutches avoided.
If it doesn't peform well -- and the expense and dedication of putting aright small problems is irksome -- get another vehicle.
Todays oil/filters can easily handle EGR.
On my '97 Taurus SHO I have the EGR system disabled. This particular engine is very sensitive to intake manifold and surge tank heating. I found that while cruising on the highway in 90F temps the EGR system would raise the surface temp of the intake track ~40F.
That plus the fact that the head and reverse flow coolant design are superior means no pre-ignition on 87 octane, no EGR and a 10:1 CP.
I do have a custom chip that will take care of the codes so no SES for me because of it.
That plus the fact that the head and reverse flow coolant design are superior means no pre-ignition on 87 octane, no EGR and a 10:1 CP.
I do have a custom chip that will take care of the codes so no SES for me because of it.
I couldn't agree more that tweaking is fun. Have done a little too much of it in younger days.
Today, believe that improving airflow in/out of engine is the one thing (when products are proven independently) worth doing. Engines are quite tightly engineered.
As to accelerated wear, the tow vehicles referenced above were made in the mid-1970's when emissions controls were at their worst. But solid maintenance kept those engines alive up (and past, according to one second owner) the quarter-million mile mark. 3-mos/3000-miles was easy to adhere unto.
And since compression was excellent past 150k (despite consumption of oil increasing from 1-qt per 1000 to 1-qt per 750; typical GM [Cadillac] consumption) while pulling an 8000# trailer, I have a hard time now -- thirty years later -- ever wishing to advise bypassing a system as simple in operation as an EGR valve.
Contaminants kept in check by a free-flowing oil filter, proper oil choice, and maybe a "maintenance" dose of ARX (or use of LUBE CONTROL) easily outweighs, IMO, any "worry" over EGR problems.
Good luck.
Today, believe that improving airflow in/out of engine is the one thing (when products are proven independently) worth doing. Engines are quite tightly engineered.
As to accelerated wear, the tow vehicles referenced above were made in the mid-1970's when emissions controls were at their worst. But solid maintenance kept those engines alive up (and past, according to one second owner) the quarter-million mile mark. 3-mos/3000-miles was easy to adhere unto.
And since compression was excellent past 150k (despite consumption of oil increasing from 1-qt per 1000 to 1-qt per 750; typical GM [Cadillac] consumption) while pulling an 8000# trailer, I have a hard time now -- thirty years later -- ever wishing to advise bypassing a system as simple in operation as an EGR valve.
Contaminants kept in check by a free-flowing oil filter, proper oil choice, and maybe a "maintenance" dose of ARX (or use of LUBE CONTROL) easily outweighs, IMO, any "worry" over EGR problems.
Good luck.
detroit got rid of the egr system since it found a way to do it without the extra parts. with more exhaust valve overlap you are also sucking a little exhaust gas back into the cylinder during the intake stroke. this decreases volumetric efficiency at all times (instead of just part throttle operation).
As RPM increases, flow velocity in the ports and header prevent exhaust backflow and actually help increase efficiency. NOx production is tolerated under these conditions.
Brian, it is inertia losses that ultimately limit the RPM in piston engines.
Example: Take a 455 cu.in. V-8 with the heads off and cam out. Use a 20 horsepower electric motor to spin the short block. It won't spin very fast with that limited amount of power. In order to spin that short block to, say, 5000 RPM would require an input of about 200 horsepower! 6000 RPM would require 400 horsepower! You can't start and stop all that mass (which at 5000 RPM weighs many TONS) for nothing! That's what downshifting on a hill does. It raises engine RPM so these looses can be used for "engine braking"..Compression or lack of compression has NOTHING to do with it! The Jake Brake simply adds compression load to inertia load.
Brian, it is inertia losses that ultimately limit the RPM in piston engines.
Example: Take a 455 cu.in. V-8 with the heads off and cam out. Use a 20 horsepower electric motor to spin the short block. It won't spin very fast with that limited amount of power. In order to spin that short block to, say, 5000 RPM would require an input of about 200 horsepower! 6000 RPM would require 400 horsepower! You can't start and stop all that mass (which at 5000 RPM weighs many TONS) for nothing! That's what downshifting on a hill does. It raises engine RPM so these looses can be used for "engine braking"..Compression or lack of compression has NOTHING to do with it! The Jake Brake simply adds compression load to inertia load.
I guess we'll have to agree to disagree on the effects of pumping losses on engine braking.
I've posted links 3rd-party sources that validate what I'm saying, and I've unwillingly (when the fuel pump failed) done the science experiment to prove it.
You haven't.
I've posted links 3rd-party sources that validate what I'm saying, and I've unwillingly (when the fuel pump failed) done the science experiment to prove it.
You haven't.
With the throttle closed, the vacuum in the intake tract is increased dramatically. Multiply this much higher vacuum by the piston area, and you can see that the resistance to rotation of the crankshaft is also increased dramatically. So throttle position does make a difference - a big one.
With regard to reciprocating mass, what happened to the concept of conservation of energy? Once the parts are accelerated to speed, they retain the energy that was used to accelerate them in the form of kinetic energy, which they can then give back during their deceleration. This is the priciple behind the flywheel on the engine, also. There is no loss of energy. Granted, the more mass the parts have the longer it will take to accelerate and decelerate them, but they still retain their energy.
If we accept this to be true, and the EGR is there to reduce NOX, doesn't it make sense to leave the EGR functional?
Right 3000. If I built a turbine vacuum pump, once started, would it run without further power since it didn't have any reciprocating parts, just a restricted intake? Crap, the narrow minded Patent Office still won't let me patent my perpetual motion machine.
I am not sure how the compression, expansion would balance out in the real world. The faster you compress or expand a gas, the more energy lost. Why do air compressors have cooling fins, and air motors get cold? On the other hand, the air in the cylinder would adsorb heat from the engine, and be hotter when it started to expand, delivering more energy. If you propped all the valves open, and did not turn the engine, it would still take energy to pump air past a throttle, through the manifold, valves, and the exhaust manifold. It takes energy to pump air through the engine, and the more the throttle restricts it, the more energy it takes. Higher RPM's means more air pumped and more energy yet.
I am not sure how the compression, expansion would balance out in the real world. The faster you compress or expand a gas, the more energy lost. Why do air compressors have cooling fins, and air motors get cold? On the other hand, the air in the cylinder would adsorb heat from the engine, and be hotter when it started to expand, delivering more energy. If you propped all the valves open, and did not turn the engine, it would still take energy to pump air past a throttle, through the manifold, valves, and the exhaust manifold. It takes energy to pump air through the engine, and the more the throttle restricts it, the more energy it takes. Higher RPM's means more air pumped and more energy yet.
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