08-09-2007, 06:11 PM
ok...so i got my o2 sensor(for future header)and egr disable programs sent to me...heres the deal...its known that egr will help cool the combustion chamber by hundreds of degrees with normal driving(disabled automaticaly at idle and wot).....so i was a bit worried about disabling it for that reason....but randy/focus sport told me that the cold/cool air coming in from the intake is cooler than the egr anyway....so i shouldnt have any issues.....it does make sense....the 800 degree(cooler) exhaust gas(egr)isnt as cool as the air coming thru your intake.....so wouldnt the egr actually be helping to heat up the cooler intake air?.....
so, heres my question....would'nt a cai/sri and a header with a good flowing cat back actualy help to lower combustion chamber temps anyway?....i mean you have more cooler air flow coming in from the cai/sri, thru the intake and then to the valves.... and easier exhaust flow(header/cat back) going out thru the exhaust valves....this to me would result in slightly lower combustion chamber temps....at least enough to make up for the 800 loss from disabling the egr.....and i know that there are possibilities of lean or rich mixtures too(detonation)with disabling the egr....could somone explain how all that ties into combustion chamber heat and the egr system.
....thanks and no bashing here.....strung.
08-10-2007, 01:01 AM
anyone?....im just curoius if anybody agrees with any of that or not.
Exhaust gas recirculation (EGR) is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique used in most gasoline and diesel engines.
EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Intermixing the incoming air with recirculated exhaust gas dilutes the mix with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mix lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mix of nitrogen and oxygen is subjected to high temperatures.
EGR is considered a `metered intake leak' and was developed to reduce the combustion temperatures to below 2,500 degrees, the threshold where NOx is created. Not unlike putting a brick in your lavatory to lower the volume of water used, the EGR valve meters a readily available inert gas (actually exhaust gas which contains a lot of very inert Carbon Dioxide) into the combustion chamber to effectively reduce the volume. Smaller effective displacement means less fire, and less heat and thus lower temperatures, thereby controlling NOx emissions.
Obviously we don't want to `reduce' the volume of the combustion chambers (effectively reduced engine displacement) during hard acceleration, so EGR is turned off when you need full power (WOT (Wide Open throttle) conditions). At idle, the engine is very sensitive to air/fuel mixture ratios and swirl in the combustion chamber, so introducing EGR at idle is not on either. However at cruise the Fuel/Air mixture is set as lean as possible for maximum economy and this in turn generates the highest temperatures, and so the EEC-V uses these conditions to inject exhaust gas into the inlet manifolds to reduce emissions.
It doesn't really 'cool' the charged air, but reduces the combustion temperature by displacing volume.
08-10-2007, 02:52 PM
ahhhh...thanks egz...i read up on the wiki article a while back but ive never seen the fordcorpio...one.....so, is the egr recycled directly to the combustion chamber or is it routed bach thru the intake first.
08-10-2007, 02:59 PM
if im not mistaken it goes into the middle of the intake manifold, before the runners, at least on non-svt zetecs.
dunno for sure about your motor...
08-10-2007, 05:45 PM
Most of the time, on most engines, it is routed somewhere in the intake, typically before the runners.
On ours, it gets routed through the head, and then dumps out shortly after the TB.
08-10-2007, 06:57 PM
interesting....some egr setups route from the exhaust manifold....that would explain why we dont have to screw with any of that when installing a header.....but what about the pzev?....the f2 header for the pzev has a strange pipe that runs across the top of it.
Thats for the AIR injection system. Upon startup, the air pump injects air into the exhast manifold to warm up the catalytic converter really quickly.