hashman626

My car is a 1991 Non-turbo coupe. Standing on the driver side looking at the engine bay, two solenoid valves on top, and a row of three on the bottom. Which one of these do i apply vacuum pressure to so i can check the EGR while the car is warm/idling. my book does not specify. List five solenoid valves but none of those is listed as the EGR solenoid.

clokker

iTrader: (2)

S5' NA's don't have EGR.

hashman626

Are you sure? My Haynes book has an egr section specifically for turbo and non turbo. Does not clearly show where the solenoid is for the egr.

satch

iTrader: (1)

The S4 has the EGR while the S5 does not. If you are certain that you have an S5 then it is not an item you will find on your car.

lastphaseofthis

iTrader: (8)

so is it harder to pass emissions on an s5?

jjwalker

If anything it's easier.

j9fd3s

iTrader: (3)

the haynes book is written for the 86-88's, and Mazda made some big changes in 89, which aren't documented in the haynes book.

the FACTORY manuals are here, Foxed.ca - Mazda RX-7 Manuals

j9fd3s

iTrader: (3)

its easier. firstly because there is no EGR for the tech to fail when its bad, and secondly because the EGR doesn't turn on during the test.

lastphaseofthis

iTrader: (8)

i'm taking my ASE L1 test tuesday for a $2.50/hr raise.. the least i know about these 80s systems the better...
that being said.. it's fun to learn...

jjwalker

Almost all modern engines have EGR.

EGR is used to reduce NOx emissions. NOx is created when N2 and O2 are subjected to high temperature and pressure, which just happens to be present in an internal combustion engine. As engines started running leaner and with higher compression, NOx emissions shot up. EGR was added because the inert exhaust gas displaced some of the normally available air and lowers combustion temperature.

EGR is relatively useless on a rotary due to the long combustion chamber area. You don't get the localized high pressure areas like you do in a piston engine due to the combustion chamber being long and constantly moving. The rotary engine still produces NOx, but from an engineering and performance standpoint, you are better off throwing a 3 way catalyst and better ECU management at it rather than EGR. Probably why mazda tossed the system on the S5. Even on the S4 you can disable the EGR and still easily pass emissions in Texas (We're pretty strict). If you did this on most piston engines you would most certainly fail.

lastphaseofthis

iTrader: (8)

egr lowers flame speed so it's also like octane on demand.. however u can't use the octane to fight boost as egr lowers VE... right?

egr made a comeback on the rx8 tho.... whom has to meet stricter emissions then the 7.

j9fd3s

iTrader: (3)

also with the Rotary there is a lot of exhaust gasses that don't leave the engine, and just get recycled into the next intake event. Mazda calls this "internal EGR" and its quite a big effect, to the point where in the Rx8 SAE paper they were measuring CO in the intake stroke, and its around 2% in a pre renesis engine.

so the EGR valve is a big redundant, its like bringing sand to the beach...

fight boost? :head scratch: Volvo pioneered a system where they could run 14.7:1 AFR's in boost, by replacing the fresh air fuel mix with inert, cooled, exhaust gasses. total gas flow is the same, but they limit power by filling the combustion chamber with gasses that don't burn. not sure how that effects the actual VE calculation, as the gas flow is the same, its just that some % is from a big cooled EGR valve.

the Rx8 doesn't have an EGR valve. in fact if you read the SAE paper the porting revisions were in part to REDUCE the amount of exhaust gasses in the intake stroke. one of the reasons the older engines need to run rich at idle is because you need a rich mixture when there is a lot of exhaust gas dilution.