violacleff Posted April 24, 2004 Share Posted April 24, 2004 I'm using the z31 ECU with MAF. I heard that venting to the atmosphere will cause a momentary richness between shifts. I think Bastaad mentioned this when he tried venting his DSM bov. If I use a Greddy/HKS SS Bov will I encounter this problem if I vent to the atmosphere, or is there a way to do this properly without having to recirculate it? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 24, 2004 Share Posted April 24, 2004 I think with most aftermarket units it's not as much of a problem, they can be adjusted to open and close more rapidly, minimizing the rich spot. Anyways I'm running a 280zxt ecu, can't say how it would affect a Z31. Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted April 24, 2004 Share Posted April 24, 2004 Once you have the air measured(AFM or MAS) you should recirculate and not vent...The type/manufacturer of device doesn't matter. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted April 24, 2004 Share Posted April 24, 2004 If you use a computer that calculates fuel from MAP reading then it doesn't matter, vent to atmosphere. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted April 25, 2004 Share Posted April 25, 2004 If you use a computer that calculates fuel from MAP reading then it doesn't matter, vent to atmosphere. Lucky megasquirt users..... I agree, with factory Z ecu (at least 280zx or Z31... dont know anything about Z32) you should recirculate it or you will hurt performance... that doesn't stop a lot of guys though... Quote Link to comment Share on other sites More sharing options...
fl327 Posted April 25, 2004 Share Posted April 25, 2004 I agree, with factory Z ecu (at least 280zx or Z31... dont know anything about Z32) you should recirculate it or you will hurt performance... that doesn't stop a lot of guys though... Like me Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 26, 2004 Share Posted April 26, 2004 The proper way to do it with any MAF set-up is to recirculate. As the other people mentioned, a speed density system does not require it. My JWT set-up, which uses a MAF had a very pronouced flat spot when you shifted gears, it was very rich, and the car was way more fun to drive once I recirculated the BOV. And while some people like it to make noise, trust me, it makes plenty of noise recirculating, trust me, you can hear it, and so could the cops I BOV'd 3 times getting on the interstate last year, without speeding. Got to love a T5 and 3.90's. Man were they ever looking. Quote Link to comment Share on other sites More sharing options...
fl327 Posted April 26, 2004 Share Posted April 26, 2004 Cant have a recirculator, I freakin love the rice shots. Love seeing blocks of my fellow rocketeers stare in awe of the scary 70s car audibly venting off the pain. Recirculated is audible, but open venting IS AUDIBLE. First thing I did when I got the car running was go for the loud BOV, to me its one of the joys of a turbo system, all the noises.. Quote Link to comment Share on other sites More sharing options...
cygnusx1 Posted April 29, 2004 Share Posted April 29, 2004 Blow off valve? Why would you take your foot off the gas anyhow? Quote Link to comment Share on other sites More sharing options...
fl327 Posted April 29, 2004 Share Posted April 29, 2004 good one Quote Link to comment Share on other sites More sharing options...
Guest bdropped Posted May 2, 2004 Share Posted May 2, 2004 if you have your maf located between the bov and the throttle body you can vent with out riching. but if you recirculate it will help keep your turbo spooled but you better have a good sized intercooler if you recirculate to keep from getting heat soak. so you can have good performance with either veting will help keep the air cooler=hp. recirculating keeps turbo spooled not as much lag=hp. thats my 2 cents Quote Link to comment Share on other sites More sharing options...
violacleff Posted May 3, 2004 Author Share Posted May 3, 2004 if you have your maf located between the bov and the throttle body you can vent with out riching. but if you recirculate it will help keep your turbo spooled but you better have a good sized intercooler if you recirculate to keep from getting heat soak. so you can have good performance with either veting will help keep the air cooler=hp. recirculating keeps turbo spooled not as much lag=hp. thats my 2 cents Interesting. Does anyone else attest to this? I do have a pretty good intercooler. Its a large HPI model. I would like to vent but if recirculating will give better boost response then perhaps that is the way to go. I have the Greddy type R, which I don't think makes as cool as sound as the type S does anyway, so no use in sacrificing performance for sound as I got a pretty big turbo which I'm hoping won't lag too much as it is. I guess with a full t4, any method to fight lag is the way to go. So recirculation it is. Quote Link to comment Share on other sites More sharing options...
technicalninja Posted May 3, 2004 Share Posted May 3, 2004 Depends on type of compressor bypass valve(CBV). If the valve is open anytime a vacuum (non-boost) conditions exist behind throttle plate then some benefits can be had. When the car is driven below boost threshold the bypass system is open which can improve throttle response (shorter intake tract) and more importantly the air charge is not passing through the turbo. This has two benefits- less heat in air charge and the turbo spins slightly faster as fewer air molecules are passing through it thus allowing earlier boost threshold. This will always be a small improvement not a major one and requires extra piping between CBV and intake tract. Some CBVs, especially "blow off valves" only vent when boost has already been produced and then a vacuum condition has been sensed by the valve. This style of valve does not allow the non boost bypass to occur during normal cruise and the above mentioned gains will not occur. Recirculating from one of these valves would help by allowing pressure difference across turbo to equalize quicker (reducing pressure on discharge side while increasing pressure on intake side) thus making it "faster" at reducing compressor surge. Secondly it would create a higher pressure on intake side during fast shifts and would allow the turbo to come on slightly quicker. This is not very noticable as during this style of driving the turbo normally is very quick at regaining boost (6000 rpm shift from 2nd to 3rd at full throttle boost comes back really fast with out any bypass valve at all). It is not mandatory to have an intercooler to use a recirculating bypass valve. The air charge will never go through turbo more than twice and as it is allowed to depressurize it reduces in tempature (not back to ambient but not a full boost temp either). as it is the first air repressurized it suffers less reheating than it got the first time through the turbo. Its already at a higher pressure than ambient and the turbo does take a little time to reach full boost so it escapes the large pres/temp rise it got the first time. The open (any time vacuum is present) bypass valve has all of the gains of the "blow off style" valve and the gains from the first paragraph also. It is the way to IMO. It can make noise at both boost on-set and at throttle close/normal blow off. The boost on-set noise can be strange and disquieting if you don't know about it (sort of a sucking-popping noise) and is much quiter than at blow-off. The blow-off noise is lower that a normal open blow off and if you like the PSSST sound this set up is not for you. Basically open compressor bypass valve= faster surge control, better off boost throttle response, increased compressor response (both full throttle and cruise operation), more complexity, and quieter operation. The gains are minor but real. They are most noticable going from cruise to boost (hiway passing type manuver). A compressor bypass valve (any style) is almost mandatory on a blow through carb set up or you can get a massive rich condition at throttle close. Hope this answers your question Rick Quote Link to comment Share on other sites More sharing options...
violacleff Posted May 4, 2004 Author Share Posted May 4, 2004 I'm using the greddy type R bov rick. What would you suggest with that system? Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted May 4, 2004 Share Posted May 4, 2004 I think the bottom line is you will get better performance with recirculated, no matter what kind of BOV you're running. Open air BOV's are for the sound.... personally I choose performance... let the guy that just got dusted wonder whats under my hood. Quote Link to comment Share on other sites More sharing options...
fl327 Posted May 4, 2004 Share Posted May 4, 2004 Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted May 4, 2004 Share Posted May 4, 2004 Face the truth! Hey... to be honest there are days (usually after just blowing the doors of some ricer) that I would LOVE to leave mine open to atmosphere... IF it didn't cause me to blow huge puffs of black smoke and feel like I was driving thru 3 ft deep mud between shifts Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted May 4, 2004 Share Posted May 4, 2004 One issue that might rise with using the MAF between the "CBV" and the throttle is the sensor is calibrated to operate in ambient and colder conditions. Intake air, even when intercooled, is quite a bit hotter than ambient, and the sensor may have linearity problems (measurement error). Just a thought, don't know if that's the case. Quote Link to comment Share on other sites More sharing options...
Jersey Posted May 4, 2004 Share Posted May 4, 2004 I like mine open to atmosphere as well 327 Must be my middle age thing (36 ) lol. I don't get the bog between shifts as you mention 525 so, doesn't seem to be affecting me performance-wise and i can tell if she's leaking. Oh yeah, and my 4 yr old son thinks it's "cool dad" 8) Quote Link to comment Share on other sites More sharing options...
240hoke Posted May 4, 2004 Share Posted May 4, 2004 YOU HAVE TO HAVE IT OPEN TO THE ATMOSPHERE. you just cant do it any other way. NOTHING beats the whooooosh noise and the "what was that????" from passengers. You guys are talking about reponse here. And im sorry but i really have never seen a BOV on a race car that is recirculating. And if it was that much better they would have a recirc one. Id say that if you're running the stock EMS then recirc is the way to go to prevent richness, but I really cant see how recirc could possibly be better. Hot air before the turbo seems bad to me. Also is you have a BOV which is open during cruising, isnt that just a big leak since it is going back in before the turbo. Seems like it would take longer to spool. Just me I really dunno... lemme find my corky book.. I'll be back -Austin Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.