- Aug 21, 2002
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I recently came across a car Forum and I had been reading through some of the performance mods they have stickied. One peaked my interested... blocking off the EGR (Exhaust Gas Recirculation) passage. Basically what they were suggesting is that you block off the EGR passage and then cut the EGR temp sensor wire and solder a resistor inline to "fool" the computer into thinking the temp was at a certain level. Supposedly this increases power.
If anyone here is planning to do that, please don't. This "mod" is a bunch of crap. Emissions devices are there for a reason, and the computer is calibated to run the engine with those devices in place and operating properly. The purpose of EGR is to reduce oxides of nitrogen emissions under certain conditions. Exhaust gas is inert as far as combustion is concerned, it doesn't burn, and it doesn't accelerate the burn. It is recirculated into the combustion chamber to slow combustion and keep temperatures below the point at which oxides of nitrogen form. Oxides of nitrogen are one of the main components of acid raid... ya know... the rain in California that eats away at the paint on your phat ride that you just blocked off the EGR passage on.
One of the side effects of EGR is increased gas mileage... since the exhaust gas takes the places of fresh air, less fuel is needed to maintain the correct air/fuel ratio.
Why is the "mod" a bunch of crap? Because EGR only operates under part throttle conditions. At WOT (wide open throttle) there is no exhaust gas being recirculated if it's operating properly, and WOT is the only condition we really care about the engine making maximum power. So... you get absolutely zero useful power gains by performing this "mod." The only thing you do is reduce your gas mileage and pollute the air.
DON'T DO IT!
*EDIT* Forgot one more point. The author of this "how to" that I found on the Forum also said this'll keep your intake manifold free of carbon build up. That's also a bunch of crap. Those carbon deposits are not from EGR... they're from when you shut the engine off and there's a little unburned fuel in some of the cylinders that had a fresh charge of air and fuel and the engine was shut off before it was ignited. The unburned fuel evaporates and makes it's way up through the intake manifold where it collects on all the hot surfaces and forms carbon deposits.
**EDIT** Addition to the last paragraph. Don't rev an engine before you shut it off. That use to be a semi-good thing to do back before computers. The theory behind doing that was that if the car had been idling, there would be some carbon buildup, because combustion wasn't very clean at idle with carburetors. Revving the engine would increase the temperature of the combustion chamber and get rid of those carbon deposits on the valves and spark plug electrodes so it would be easier to start next time. With fuel injection, combustion is much more clean at idle, and these carbon deposits don't form. When you rev up the engine and shut it off, all you're doing is loading up the cylinders with more fuel before you shut it off... so you have more fuel to evaporate and create carbon deposits in the intake and up around the throttle body.
If anyone here is planning to do that, please don't. This "mod" is a bunch of crap. Emissions devices are there for a reason, and the computer is calibated to run the engine with those devices in place and operating properly. The purpose of EGR is to reduce oxides of nitrogen emissions under certain conditions. Exhaust gas is inert as far as combustion is concerned, it doesn't burn, and it doesn't accelerate the burn. It is recirculated into the combustion chamber to slow combustion and keep temperatures below the point at which oxides of nitrogen form. Oxides of nitrogen are one of the main components of acid raid... ya know... the rain in California that eats away at the paint on your phat ride that you just blocked off the EGR passage on.
One of the side effects of EGR is increased gas mileage... since the exhaust gas takes the places of fresh air, less fuel is needed to maintain the correct air/fuel ratio.Why is the "mod" a bunch of crap? Because EGR only operates under part throttle conditions. At WOT (wide open throttle) there is no exhaust gas being recirculated if it's operating properly, and WOT is the only condition we really care about the engine making maximum power. So... you get absolutely zero useful power gains by performing this "mod." The only thing you do is reduce your gas mileage and pollute the air.
DON'T DO IT!
*EDIT* Forgot one more point. The author of this "how to" that I found on the Forum also said this'll keep your intake manifold free of carbon build up. That's also a bunch of crap. Those carbon deposits are not from EGR... they're from when you shut the engine off and there's a little unburned fuel in some of the cylinders that had a fresh charge of air and fuel and the engine was shut off before it was ignited. The unburned fuel evaporates and makes it's way up through the intake manifold where it collects on all the hot surfaces and forms carbon deposits.
**EDIT** Addition to the last paragraph. Don't rev an engine before you shut it off. That use to be a semi-good thing to do back before computers. The theory behind doing that was that if the car had been idling, there would be some carbon buildup, because combustion wasn't very clean at idle with carburetors. Revving the engine would increase the temperature of the combustion chamber and get rid of those carbon deposits on the valves and spark plug electrodes so it would be easier to start next time. With fuel injection, combustion is much more clean at idle, and these carbon deposits don't form. When you rev up the engine and shut it off, all you're doing is loading up the cylinders with more fuel before you shut it off... so you have more fuel to evaporate and create carbon deposits in the intake and up around the throttle body.
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