I recently just bought a Rx7 FD3S 1994 car and its been running ok but has been doing some major backfiring , now being that im not all that gen'd up on motors i could do with some help (and i thought id ask the experts). so here goes , the guy that i bought it off has recently put a bov valve onto the car , in the area between the intercooler (standard) and the manifold which is all good and dandy but i think the car has already got a bov valve (air bypass valve) which mazda put on as standard.

Now the standard valve which is already there (the air bypass valve which everyone seems to call the bov) is plugged in still and has a hose to it with another going to the manifold. now when the car is started this releases air (lots) which in my understanding is ok as its part of the quick warmup process but once the car has warmed up still releases air ? is this normal secondly i dont think the new BOV valve has been installed correctly and has nothing from the manifold telling it to do anything and is just sat there which makes me think that the car is not getting enough air and pumping to much petrol into the engine therefore backfiring (alot)

does anyone know how i could solve this ? , i thought about taking the manifold to the aftermarket bov and hopfully that would make the other redundant but dont know if its as easy as that , or looking like what im going to have to do would be to take the aftermarket part out and buy a new hose from the intercooler to the manifold which takes the second bov out of the equasion...

or am i just being stupid and worrying over nothing and this is how its meant to be ?

cheers guys if anyone reads this and replys i will be quite suprised but also greatfull i can upload picstures of this if it helps anyone to understand my problem

Cheers

and hello to all!

 

If you have a camera you may want to take some pictures to help us understand. From the factory there are two BOV's....one is the actual BOV the other is the CRV (charge relief valve). The charge relief vale will exhaust air up until 4500 rpm when it shuts to allow boost from both the primary and secondary turbo the actual BOV is the one hooked to the manifold and will release boost under decelerate condition (vacuum). If your after market BOV is not plumbed into the manifold then it will not release the boost pressure. Do you have a boost gauge ? as this will help greatly in figuring out your problem.

 

Spot on i will take some pictures soon to make my blabber easier to understand but that that youve said has made me understand it all better anyway, i dont have a turbo timer at the moment but its somthing i will be investing in soon cheers matey

 

Yes, pictures will help tremendously. Also keep in mind the stock sequential turbo system has two bypass valves, one for the secondary turbo prespool and a proper BOV. You can see where/how they're supposed to be plumbed:

 

Skip the turbo timer and spend some time reading the faq in this forum.

The backfiring is unrelated. The car has a MAP sensor that will keep the right air/fuel *as long as the boost remains below the stock limit of 10psi*. If the boost goes over 12psi, really bad things happen.

The leaking air at the BOV is probably really annoying, but not necessarily a major problem. I would remove it and plug the bung until you get things working well and then decide whether to replace the stock BOV. I say this because aftermarket bov's are not a performance mod on this car, and it's just an extra variable to potentially complicate matters until the car is well sorted.

IMHO, your first priority is to put in a boost gauge and see what the boost is. Then if the boost is normal and you still have backfiring, see what kind of ECU and injectors are installed and how it's tuned. Backfiring is usually caused by poor tuning.

Dave

 

Thanks guys , for all the info will be uploading pictures shortly, thanks for the info tho , now i know that its not a major malfunction al have to invest in a turbo timer , and see what it gives me!

 

Don't waste your money on a turbo timer. It isn't going to solve or prevent anything

 

you mean boost guage right.. not a turbo timer. 2 complete different things..
just giving you a heads up =)

 

Not all together true. For what it's worth most turbo timers have other functions or readouts than just keeping your car running. Because most of you guys think they are junk I was able to pickup an Apexi TT for less than the price of a decent voltage gauge. It's not nearly as large as the guage would be and of course has other features. I've found the voltage feature to be quite helpful in catching an alternator failure, battery crapping out on me and just the general health of the charging and electrical circuict on the car. Being these cars are so sensitive to electrical issues i'm glad you guys feel this way, perhaps he'll find one as cheaply as I did. While the boost gauge is most deffinately needed so is a voltage gauge. IMO