baix2

i came across this earlier while i was reading about detonation. http://www.turborx7.com/detonation.htm "2. Check for loss of EGR. The Exhaust Gas Recirculation (EGR) system is one of the engine's primary emission controls. Its purpose is to reduce oxides of nitrogen (NOX) pollution in the exhaust. It does this by "leaking" (recirculating) small amounts of exhaust into the intake manifold through the EGR valve. Though the gases are hot, they actually have a cooling effect on combustion temperatures by diluting the air/fuel mixture slightly. Lowering the combustion temperature reduces the formation of NOX as well as the octane requirements of the engine. If the EGR valve is not opening, either because the valve itself is defective or because its vacuum supply is blocked (loose, plugged or misrouted vacuum hose connections, or a defective vacuum control valve or solenoid), the cooling effect is lost. The result will be higher combustion temperatures under load and an increased chance of detonation." i done some basic search and the closest thread i found is egr removal=detonation with piston engine? so the above passage that i quoted is only true for piston engine? as many ppl here are removing/blocking off the EGR, pretty sure it's safe doing so. btw was reading the sticky 3rd gen FAQ also. it mentioned "note: many japanese RX-7's don't use EGR valves, including the 99+ models" i was under the impression (from many other EGR related post as well) that ALL FDs from japan don't have EGR at all. now i am a bit confused if some of the earlier models have EGR? (i am actually buying a 95 jdm FD soon) hope someone can clear this up. thanks in advance

DaleClark

EGR is a VERY worthless system on the FD. Mazda knew it, I think they just had to put it on there to check off a box for federal emissions that it has EGR.

I think the Mazda engineers knew it, the gasket for the EGR system has a PINHOLE for exhaust gasses to come through. This clogs shut with carbon in no time flat.

'95s didn't have EGR, and neither did any JDM FD's.

Yes, EGR can reduce combustion temps, but it does so by replacing part of the air fuel mixture with inert gas - you're using some of the combustion volume for something that doesn't explode. Also, EGR systems only work at cruise/light load, not full load where we're typically concerned about detonation.

In other cars and piston engined cars this might be a different story, but the above holds true for RX-7's. Don't sweat it.

Dale

RotaryEvolution

rotaries already recirculate a decent amount of exhaust gasses with the fresh intake cycle so it has a built in EGR system already(partly why they will never be as efficient as 4 stroke piston engines will be).

in '89-91 they somehow managed to let the cars by without an EGR valve for the USDM market but then required it again with the introduction of the FD3S. as Dale mentioned there is virtually no way that the EGR valve on the FD can fail to an open state because of the large restriction they built into the gasket. if it fails closed it will hardly be noticable if at all(engine temperature wise).

many modified cars omit the EGR valve, though it can help as a detonation deturrent it is marginal and also has the negative side effect of losing a small amount of power as that inert gas replaces combustible power producing space(replacing the intake charge as it goes into the engine).

arghx

If you follow industry trends you'll notice that on most new gas engines actual EGR valves are being abandoned. Basic variable valve timing systems can produce sufficient EGR by opening the intake valve earlier (advance the intake cam) and/or closing the exhaust valve later (retard the exhaust cam). This creates overlap between the intake and exhaust stroke.

The Rx-8 doesn't have an EGR valve and it has 10:1 compression and zero overlap between intake and exhaust stroke. It actually has far less internal EGR compared to the REW.

RotaryEvolution

that's because we no longer have inferior fuel injection systems or carburetors.