EGR valve
 

My P5 sometimes has a surge under excel. Kind of like the air kicking on, but air is off. In past cars that had this problem I have found the EGR valve opening/closing caused it. I just plugged the vacuum line and all was well.

Looked last night and saw the classical line coming from the exhaust manifold for an EGR valve but due to falling light I could not see it under the intake.

So, is there a EGR valve hiding under there? Have anyone else had a slight surge?

Yes there is a EGR valve adn it could be causing the surging i get it from tiem to time too

what's an EGR valve?

Its an emissions control EGR= Exhaust Gas Recirculator it opens from time to time to let exhaust gas pass back through the motor to lower emissions. If you want better performance you can remove it but then your car would not be emmisions legal. I am going to take mine off as I have ahook up with inspections.

i like what I hear, can someone post pix?

would you burn more gas?? (edited) acctually i read my manual and it seems it would burn more gas at lower rpms when the engine is warm/hot. also on the 3rd gens the egr valve electronically controlled. so my question is will the engine light come on? and sense it is electronically controled you think we could hook up a switch to it?
Speaking of switches anyone heard of the IAT Mod where you put a resistor in line with the sensor and it tricks the ecu into thinking its lower air temp? if you have how would you hook a switch up to either??

I am goign to make a block off plate so that the valve will still be there but nothing connected to it. SO the computer will think it is still working but it isn't. As for the IAT mod no one has tried it on a Protege I know of but it can be done people seem to think that it will throw a CEL code. As for burning more gas on idle without the EGR I would think I would run leaner at idle since it won't be feeding hot air into the intake manifold just the air from the actually intake and not the exhaust.

I will plug the vacuum line soon. This is not as good as Design's solution buy building a block off plate and plugging the line from the exhaust manifold.

I will try and take pictures, but finding the EGR valve is easy. One large metal line in from exhaust and one vacuum line on top of the valve.

The EGR isn't utilized during WOT so making a block off plate or plugging the vacuum line ins't going to net you any free horsepower. Secondly, when the EGR valve is open, there is a noticable drop in RPM's. The ECU will look for this drop when activated under certain conditions to check it's operation and throw a code if a problem comes up. Also, if Mazda borrowed any tech from Ford, there will also be a pressure sensor in the EGR system to check operation. Another item which will throw a code if correct data doesn't come in.

Just so you know removing the EGR will not net any WOT gains true but your throttle responce throughout your throttle will be increased. Spoolin has removed his EGR tubing and does not get any codes thrown from it jsut so you know.

Below is some info on the ERG valve just for kicks. Found on the net - I am not that smart:)

EGR Valves have been around for a long time. Way back in 1972 GM used them in an attempt to reduce emissions of oxides of nitrogen (NOx) which were a major cause of air pollution, mainly photochemical smog, that kind of smog which is formed when strong sunlight shines down on the exhaust gasses we puke out of our tailpipes by the billions of cubic feet a day.

A short chemistry lesson is in order here. It was discovered way back when, that high combustion chamber peak temperatures (the really short duration high temperatures near the end of the combustion process) caused oxygen and nitrogen to combine chemically and form these oxides of nitrogen mentioned above. Most of the anti-pollution devices of the day did a pretty good job of reducing the other bad by-products of combustion, namely excessive hydrocarbons and carbon monoxide, however they tended to induce the formation of oxides of nitrogen. Something had to be done else we would all die of smog diseases.

The automotive engineers figured that they needed to do something to lower the peak combustion temperatures which only occurred under certain high load driving conditions. They figured they could do so at the expense of power and fuel economy but what the heck, ya can't have everything! If they could only add something to the combustion chamber that would act like sort of a fire extinguisher to cool the combustion temperatures that would do it.

So they invented a way to allow some very inert gas to get back into the combustion chamber only when needed. They needed a source of this gas - it wasn't air, cuz that contains oxygen and nitrogen which caused the problem in the first place. So they chose carbon dioxide. Where to get a supply of carbon dioxide . . . ??? Hmmmm, how about the exhaust system? That is mainly carbon dioxide and water (plus a zillion other noxious chemicals) Suppose we allow some of the exhaust gas to get back into the intake manifold under strict control and only when we need it? That would cool the combustion chamber and prevent the formation of the NoX. Maybe we should call it recirculated exhaust gas (REG??). But a guy named Reginald voted no cuz he didn't want his name associated with a car part, so they called it exhaust gas recirculation (EGR) since there was nobody around with that name.

And futher into the artical it did say that if the EGR valve did not open, the hot flame front could cause a ping situation. I never had this problem with other cars. With the new fuels and the compression of the P5 motor, this should not be a problem. If it is, just go to a higher grade of fuel.

Have fun

The main thing that EGR does (as explained previously) is bring combustion temperatures down. It only works during cruising conditions so it SHOULD NOT affect stop and go driving or all out acceleration. It puts a percentage of exhaust gas back into the intake to take up space that would normally be occupied by fuel air mixture. Typical is around 8-10%. This has a damping effect on combustion. NoX is very bad for the atmosphere and is what makes visible smog as well as contributes to acid rain. Acid rain is basically water molecules combining with the NoX to form Nitric acid. This is also very hard on anything organic that it hits which is why the government requires it on passenger cars.