Guest jt240z Posted July 6, 2002 Share Posted July 6, 2002 Hey ZR8ED, If you're using an Air Flow Meter or Mass Air Flow meter, then you need to plumb the BOV back between the AFM/MAF and the compressor intake. If you don't do this and just vent the discharge to the atmosphere, you'll go very rich when you let off the gas. Sound familiar The reason for this is that your AFM/MAF sees all the air that is being pumped out your BOV, that is not getting to you engine, and your ECU is adding gas to compensate. Try plumbing the BOV discharge back in and see if that helps. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted July 7, 2002 Share Posted July 7, 2002 Soounds like it might also need to be tightened up a little if it's venting that easily. Venting it into the intake is the correct way to go but it won't sound as cool Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted July 7, 2002 Author Share Posted July 7, 2002 Hmm I'm having some troubles with fine tuning the VG. Its running pretty rich most of the time. My air/fuel monitor is telling me I'm cruising around 11-12.8 to 1 fuel ratio. when ever I shift, my BOV blows, and the reading goes straight to 10:1 then works its way back. Under WOT it goes to 10:1 that part I know is good for fighting detonation. Getting terrible mileage.. everything seems to check out. so far, can't figure why its running so rich...it used to get good mileage...28+.. I've been battling I/C pipe connectors popping off. I have it down to only 1 popping off for the last few weeks..now they are all holding. They held 10 psi no probs.. but 15.. it would pop off eventually. that is a big monkey off my back. I was ready to shoot the car there for a while. Ok heres the current issue.. I think it may be because the car is running rich, or my BOV. When I'm running the car moderately.. as in running near the boost/vacuum threshold, any release of my gas pedal.. even just a bit, and the BOV opens up making the car a bit jerky to drive like that. also when under very light throttle, if I want to spool up just a bit.. 0-5 psi, the car wants to fall on its face and hesitate..the boost then comes on by this time my rpms are nearing 3-3.5K (in first gear) when this happens the car gets up and goes.. and with the stereo turned down, I can hear the tires spinning. WOT the car just hauls ass. 15psi makes for some fun. On a side note.. my Khumo Victoracers are working very well. I can't spin the tires when shifting gears now. 265's and an LSD are able to hold the power at this time... for now.. with a treadwear of 50, I can't afford too much wheelspin. BTW my BOV is a turboXS type H it is adjustable, but idon't want to play with it till I know which way to adjust it, and the effects it will have. It just seems like it goes off too easily. I had some club memebers play with it a bit, and I have no idea how it was set from the factory. (no I didn't let them touch it.. ) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 7, 2002 Share Posted July 7, 2002 Btw, on your TurboXS that basically means tighten (clockwise) the screw. I totally agree on the bov-intake, right now you're sending metered air to the atmosphere. Its just like running a n/a with one of the vacuum lines removed between afm-mas/tb. And yeah.. I've done this before.. reconnected everything but the crankcase breather tube, and couldn't understand why the car would BOG under WOT, till I popped the hood and heard the horrible hissing sound About the bov-intake, I wondered if this wasn't somewhat counter productive. Well, provided that your venting is past the i/c the charge air returning to the intake isn't TOO much hotter than ambient (w/ efficient i/c and comp.), however the air is just gonna get even hotter running back through the compressor again. See what I mean? I'm glad I don't have to deal with this- sds. Well I hope you fix your problem, I still have a million of my own... -980mak Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted July 7, 2002 Share Posted July 7, 2002 The BOV must be plumbed back in the system on the MAF set=up. Mine fell flat on its face every time I shifted until I plumbed it back in front of the turbo. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted July 7, 2002 Author Share Posted July 7, 2002 Thanks 980mak on the adjustment. As far as plumbing it back in..?? mine has several openings all around the base of the BOV (the bov is approx 1 &3/4 inches in diam) each opening is blocked by an internal piston, when the BOV opens, it retracts this piston and reveals these 4- 1/2" dia holes which let out the air. I don't think I can plumb this BOV back to the intake. I do have it located approx 12" from the throttle plate. Darn.. I don't want to buy a new BOV. They aren't cheap.. and this one is loud as hell.. scares people on the sidewalks and other cars!! I guess I'll just dive right in and adjust that bov.. Though my motto has always been to "GO FOR IT!!!!" I have learned with experience, that this is not always the best way..or cheaper way.. So I'm a bit more hesitant these days. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted July 7, 2002 Share Posted July 7, 2002 Doh, you're right that isn't going to be easily plumed back in Sounds like it's either time for an SDS MAP based system or a different BOV. I need one myself but I'm not sure I want one super loud - just effective. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 7, 2002 Share Posted July 7, 2002 Ouch.... that's a tough one. Obviously yours was designed for atmo.. or it would have a symmetrical discharge flange. You could try tightening it, it would definitely help as it wouldn't dump so quickly or easily. Otherwise you may have to get a type that is able to vent back.. if yours is new you could probably get near-value back if you sold it on ebay, if you have the box/instructions etc. and you make a good flange cut (it was welded in, correct?). Heck I might even bid the type of BOV you're looking for has a certain name, I can't think of it at the moment. -980mak Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted July 10, 2002 Share Posted July 10, 2002 blowing off pipes?......you arent using radiator clamps are you?...i got some of those "heavy duty" s.o.b. clamps (still blew off my j-pipe once)....its kinda hard to tell how tight they are......s Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted July 10, 2002 Share Posted July 10, 2002 Originally posted by theschmaydee:blowing off pipes?......you arent using radiator clamps are you?...i got some of those "heavy duty" s.o.b. clamps (still blew off my j-pipe once)....its kinda hard to tell how tight they are......s NAPA sells the really nice T-bolt clamps supposedly. The Supra guys rave over them but I've yet to switch. Blown a few pipes off myself and if I weren't MAP I'd have been getting a tow home at least once already Quote Link to comment Share on other sites More sharing options...
scottyMIz Posted July 10, 2002 Share Posted July 10, 2002 i use radiator pipe hoses and the only time mine blow off is when i forget to tighten them I plan to get better ones later but i dunno where to get them Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 10, 2002 Share Posted July 10, 2002 When you start upping the boost, you have to make the investment in having "lips" at the ends of the pipes and use T-bolt clamps. Since I did this I have not blown off a single hose running 24psi. We rushed to get the RX-7 to the track last week with no lips and plain screw clamps and gave up after 3 runs. Same goes for tires. Only thing worse than blowing away the tires on a run is doing with with the wheels not straight. Regular street radials will not cut it. Quote Link to comment Share on other sites More sharing options...
SHANE Posted July 10, 2002 Share Posted July 10, 2002 just leave the blow off valve alone. venting to atmosphere wont hurt anything. i still have the mass air meter and the same bov as you, i just turned the idle up to about 1000rpms and it does just fine. you would have a hell of time recirculating that one anyway!! Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted July 10, 2002 Share Posted July 10, 2002 FYI guys - We seem to have a terminology issue here. A BOV (Blow Off Valve) vents the intake manifold to atmosphere to avoid overboost situations. some manuals refer to it as an 'Emergency Relief Valve'. What we are talking about here is a Compressor By-Pass Valve - designed with the purpose of keeping the turbo from spooling down rapidly because the throttle is closed and the air pumping out of the turbo backs up and slows the unit down. It does this by routing the air stacked up in front of the throttle plate (after the compressor) and routing it to just in front of the compressor. Since you're not on the throttle, the temperature increase is of no significance, but the effect when you get back on the throttle is nothing short of miraculous! It seems every so often people start mis-applying the terms. Everyone that has said the air from the valve needs to get routed to in front of the turbo after the mass air sensor is correct, otherwise the sensor is telling the engine you are USING the air being dumped and run too rich. One of the reasons for using one of these is because we want to make our cars as driveable and responsive as possible. Failing to duct the air back properly in my mind means the effort is half wasted. JMHO, Brad Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 10, 2002 Share Posted July 10, 2002 Brad, I probably have some confusion interpreting what you are saying and if so I apologize. I do not know what a "compressor bypass valve" is, but your description of it is indeed that of a BOV, except for the part about routing it back in front of the compressor. A BOV can vent back into the itake system or the atmosphere depending on the application. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted July 11, 2002 Author Share Posted July 11, 2002 Your right Scottie. The pipe that pops doesn't have a lip on it. hmm more adjustments. I'll check for those clamps you mention..the only ones I've seen like it are for exhaust systems.. (really heavy looking) So far tho, the pipes are holding the increased boost. Amazing the effect of using a properly designed i/c hose. Though I'm only using 1 piece of high temp silicone stuff. The BOV is a done issue. its stays.. too much $$. I'll just deal with it. I'm more interested in solving the running on the rich side all the time. There are so many customized connections, and deleted support equipment/emmisions stuff, it is very hard to track down why the engine is running rich during normal drving (ie highway cruise) The 300zxt had a lot of weird ancillary junk on the motor, and about a thousand vacuum lines many of which did not make the swap to the 280Z. My motor looks very simple looking under the hood. Any ideas of items to check for rich condition? ecu codes are good. ecu is stock for now I do have a head temp sensor fuel tem sensor fuel pressure reg and vacuum knock sensor crank angle sensor timing is stock. o2 sensor air/fuel ratio guage from o2 stock 300zxt afm start up air bypass. (for high idle) not sure if injectors are firing in group or sequential... manual says it starts sequential, and switches to group when at temp. don't know what controls that? EGR valve works (new) no cat not much else on this motor.. suggestions of what else to look at that controls fuel? Thanks guys for the advice. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted July 11, 2002 Share Posted July 11, 2002 Please feel free to correct if I'm wrong, but this is what I believe to be the correct terminology for the various pieces of hardware hanging on the intake... A BOV (blow-off valve) is mounted between the compressor and the throttle body, and releases pressure when triggered by manifold vacuum (throttle closure). Typically the pressure is released into the air. A "compressor bypass" valve and a "diverter" valve are identical, and function similarly to a BOV, only the vent is typically routed back to the intake on a factory ECU (for emissions reasons). And finally, a "pop-off" valve is a Nissan factory pressure relief valve mounted on the intake manifold after the throttle to release the manifold pressure to atmosphere if it gets too high (factory Nissan vents around 8-9 psi, for margin over stock 5-6 psi boost). Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted July 11, 2002 Share Posted July 11, 2002 Scott, if you are running rich in all operating ranges, then the 2 most obvious, especially with swaps like yours, are: some missing or malfunctioning temp sensor that has the ECM believeing that the engine is not up to normal operating temperature or fuel pressure too high because of a malfunctioning or incorrectly set FPR. It is a common mistake to set the FP with the vacuum line connected. FP should be set in the no vac/no boost condition. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted July 12, 2002 Author Share Posted July 12, 2002 Doh! Scottie you may have hit the nail on the head.... fuel pressure... I don't recall setting it with the vac line on, but ya never know.. that, and I recall having the pressure set slightly higher than stock..to fight detonation, back when I was not I/C'd... hmmm I guess I'll haul it out and check the FP again to be sure... I've been spending some time reading the FSM on this engine. I read it 10 times+ cover to cover before I did the swap...I guess I need a refresher. Thanks guys. I've been working on so many different problems as well as a new job etc.. Just needed some ideas to get the brain working again in Z mode. Quote Link to comment Share on other sites More sharing options...
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