Blow off Valve
02-10-04, 08:28 PM
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Blow off Valve
I am in the process of installing a new engine. I am using the stock twins and stock configuration. The engine will have a street port but use the stock exhaust system. Only reliability mods will be done. Do I need a blow off valve? Would it be something which my set up can utilize? I will be running stock boost. I see there different types of valves as in the way they operate. I also see them sold as stand alone valves. Via the pictures I can't tell how they are installed. Are there ones which you can install into stock pluming? I understand the basic concept however sifting through adds etc is not like hearing from real owners/users. Send me to a link if you have one, or some Rx7 specific information. I hope to get my FD running this weekend.
02-10-04, 08:39 PM
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BOV not necessary for stock turbos and stock boost level. the bov would only be for the woosh sound. if thats all you want than go for the xs bov. i think they are they loudest one out. there is no practicle use in stock conditions.
if you were boosting higher amounts then perhaps bov would help (depending how much you are boosting). the bov is to release the shockwave created when the throtle body shuts. it does not relieve PRESSURE! common misconception that it releases pressure. if it were pressure that would mean you would be boosting even afer releasing throtle.
check/search threads im sure there is much more out there.
if you were boosting higher amounts then perhaps bov would help (depending how much you are boosting). the bov is to release the shockwave created when the throtle body shuts. it does not relieve PRESSURE! common misconception that it releases pressure. if it were pressure that would mean you would be boosting even afer releasing throtle.
check/search threads im sure there is much more out there.
02-10-04, 08:48 PM
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Thanks for the heads up. I can live with out the sound. That makes sense concerning the operation of the BOV. The shock wave as I have read is just beating on things with no up side with a closed throttle. I will be running on no or low boost for some time during brake in.
02-10-04, 09:19 PM
#6
jsj welcome and be careful who you listen to on the boards. theres a lot of little kids who just repeat everything they hear. what type of engine did you get? a reman? no boost for the first 1k miles is critical especially if the engine has new bearings!! Theres people that argue that breakin isnt needed but I say why not do it just in case it is...it cant hurt anything except youll miss out on some fun for a couple thousand miles ohh well. You should change out your oil after a couple hundred miles on the motor and also flush the coolant again in case it was dirty inside the coolant passages of the motor or your throttle body/thermostat cover...these things arent needed but just good practice with a new motor.
Now an upgraded blow off valve isnt needed for stock boost levels or even much higher. I believe that anything you do with the twins the stock bov is fine. It also uses a charge relief valve in the sequential form. Yes there are kits that replace the bov that run a hose to the y pipe area instead of being on a pipe with a flange. Same thing but the size of the hose restrics how much pressure it can release when the throttle snaps shut. ALSO this is important. If you ever do get a bov mount it as close to the throttle body as possible. This will do the least amount of damage to the turbos.
if the bov isnt letting out enough air or opening fast enough when the throttle closes youll get what is called compressor surge...air will travel back to the turbo and slow it down and youll hear this sound in this video of my car
http://216.98.9.98/rx7/118-1897_MVI.AVI
good luck
Now an upgraded blow off valve isnt needed for stock boost levels or even much higher. I believe that anything you do with the twins the stock bov is fine. It also uses a charge relief valve in the sequential form. Yes there are kits that replace the bov that run a hose to the y pipe area instead of being on a pipe with a flange. Same thing but the size of the hose restrics how much pressure it can release when the throttle snaps shut. ALSO this is important. If you ever do get a bov mount it as close to the throttle body as possible. This will do the least amount of damage to the turbos.
if the bov isnt letting out enough air or opening fast enough when the throttle closes youll get what is called compressor surge...air will travel back to the turbo and slow it down and youll hear this sound in this video of my car
http://216.98.9.98/rx7/118-1897_MVI.AVI
good luck
02-10-04, 11:24 PM
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SurgeMonster,
Thanks for the information, and yes I see I'm an old man in this forum. I do remember when I was young and just regurgitated bits and peaces of information but didn't really know enough to elaborate further. I have made the biggest error and haven't picked up a factory manual as yet. I am getting one this week. I have been doing tune-up and drive-ability work at General Motors dealers for 20 years but this rotary/turbo/non on board diagnostic stuff is starting to grow on me. I am used to be able to see a data stream and interact with the CPU/ECM. I am hoping the factory manual go's into detail concerning the actual program sensor criteria. This is the life blood of a diagnostician. The mix of CPU and no available data stream is much like the old days with a HUGE twist. The video clearly showed what you were talking about. I see how a BOV must be matched with the volume and speed in which its going to be used for. I am getting a street port from a Texas rotary shop called "Dirty South Rotary Performance" the owner builder was recommended to me by some old friends and I have had good communication thus far. I was going to overhaul the engine but chickened out. I have another turbo motor so I may build it as a spare. It's a Cosmo 13b *** and it has real low miles on it. I would have to fab some motor mounts but that just R&D. Thanks again for the input.
Thanks for the information, and yes I see I'm an old man in this forum. I do remember when I was young and just regurgitated bits and peaces of information but didn't really know enough to elaborate further. I have made the biggest error and haven't picked up a factory manual as yet. I am getting one this week. I have been doing tune-up and drive-ability work at General Motors dealers for 20 years but this rotary/turbo/non on board diagnostic stuff is starting to grow on me. I am used to be able to see a data stream and interact with the CPU/ECM. I am hoping the factory manual go's into detail concerning the actual program sensor criteria. This is the life blood of a diagnostician. The mix of CPU and no available data stream is much like the old days with a HUGE twist. The video clearly showed what you were talking about. I see how a BOV must be matched with the volume and speed in which its going to be used for. I am getting a street port from a Texas rotary shop called "Dirty South Rotary Performance" the owner builder was recommended to me by some old friends and I have had good communication thus far. I was going to overhaul the engine but chickened out. I have another turbo motor so I may build it as a spare. It's a Cosmo 13b *** and it has real low miles on it. I would have to fab some motor mounts but that just R&D. Thanks again for the input.
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02-11-04, 12:43 AM
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JSJ,
What you need is an Apex'I PowerFC and Datalogit.
Full data logging and access to sensor data. Not to mention the ability to tune all of the injection and ignition maps (don't do this without a wideband o2 and training - one can detonate fairly easy).
What you need is an Apex'I PowerFC and Datalogit.
Full data logging and access to sensor data. Not to mention the ability to tune all of the injection and ignition maps (don't do this without a wideband o2 and training - one can detonate fairly easy).
