scottyMIz Posted February 5, 2002 Share Posted February 5, 2002 ok here's the scoop i want to turbocharge the mazda b2000 cuz it's dog slow.The thing is in my bible(maximum boost)it says with a carb system you need a bov to release the pressure or you get it to run rich between shifts and it won't run right.So my question is can i use an egr valve as a bov? it's the same concept except it lets exhaust in when vaccum is applied to the egr valve.I figure i can mod it so i can use it for low boost sound like a good idea or not?I just don't want to spend money on a bov just for a truck that will only get low boost.Plus the truck isn't worth it and i have everything else to do it just not a bov. Quote Link to comment Share on other sites More sharing options...
Len Posted February 5, 2002 Share Posted February 5, 2002 Scotty I think Tim is right. You can pick up a cheap BOV easier than trying to rig up a EGR.Although anything is possible. Even an EGR made into a BOV. But time spent on that project can be constructivly applied elsewhere to more benefit! Tim please give me the name of the wrecking yards in TX giving those 1st Gen BOV's away; they are charging $50 bucks if you can find one here in OKC. Len Quote Link to comment Share on other sites More sharing options...
scottyMIz Posted February 5, 2002 Author Share Posted February 5, 2002 tim the only reason i haven't done that yet is cuz there aren't any close to me.The closest one is like an hour away i think and i don't feel like driving that far for a bov.But i might need a adjustable fuel pressure regulator too so i just might.I have to check out if i can set mine a bit higher so i won't have to get one.This is a very low budget plan so every corner i can cut i will.If you find one at the wrecking yard and it isn't too much could you ppick one up ror let me know how much and i'll give you money to get it for me? Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted February 6, 2002 Share Posted February 6, 2002 Yeah, the stock 1G DSM BOV is good to about 21psi or so, if you plan on running that then you can "crush" the BOV so that it will hold more. Quote Link to comment Share on other sites More sharing options...
Len Posted February 6, 2002 Share Posted February 6, 2002 Another thought; My stock 280ZXT came W/O a BOV. It ran 5 PSI. I don't know what year Car builders decided a stock BOV was a good idea. I also don't know what is a safe boost to run W/O a BOV. You mentioned you weren't going to run a high boost. Maybe you would be safe putting your turbo together; running it; finding what boost you will run and if you can run it till you find a cheap BOV. Quote Link to comment Share on other sites More sharing options...
DAW Posted February 6, 2002 Share Posted February 6, 2002 The creative thinking is good on the BOV idea and I tried the same approach using an Air Pump regulator valve from the early Z. There was a problem in adapting it due to it blowing off at too low a vacuum signal, dumping boost you wanted to use. The Talon/Eclipse approach is good, although I didn't like the constriction of the short pipe segment which incorporates the base of the BOV. I took a larger diameter turbo pipe from a Volvo, cut a hole in it where I wanted the valve base to locate, then split the Eclipse pipe along its length opposite the valve. After shaping the eclipse piece around the larger dia. of the Volvo piece, I welded the perimeter of the Eclipse piece on and I had a BOV without restricted flow, and a mounting bracket (part of the Eclipse piece) DAW Quote Link to comment Share on other sites More sharing options...
Guest Tim78zt Posted February 6, 2002 Share Posted February 6, 2002 Hey Scotty, just go to the wrecking yard and get a BOV from a 1st Gen Eclipse. They are practically giving them away, and they are reliable. Tim78zt Quote Link to comment Share on other sites More sharing options...
scottyMIz Posted February 6, 2002 Author Share Posted February 6, 2002 hey len i ran 18 psi of boost on the stock turbo with out a bov so that's safe but i'm concerned about this being a carberated car and it making it run crappy from the difference in pressures on the other sides of the throttle plate.But i just might break down and get a eclipse bov i dunno yet but thanks guys Quote Link to comment Share on other sites More sharing options...
Guest Tim78zt Posted February 6, 2002 Share Posted February 6, 2002 Hey Len and Scotty! Alamo here in Texas has used 1GEN BOVs for $25. I'm sure they will gladly ship you one if you call them at 817-860-4300 ask for Larry or Brice and tell them I sent you. If they are not willing to ship let me know and I will go over and get it and ship it to you. Tim78zt Quote Link to comment Share on other sites More sharing options...
scottyMIz Posted February 9, 2002 Author Share Posted February 9, 2002 thanks tim i'll check it out Quote Link to comment Share on other sites More sharing options...
Len Posted February 9, 2002 Share Posted February 9, 2002 Wow Tim; your the man! Thank you! You came thru for me once again! I'll wait till Monday to call so that Scotty will have a chance to call first, since you asked first Scotty. By the way Tim I've been squirting that PB Blaster on my O2 sensor. I just returned from Autozone with those removal sockets you told me about. She's not budging yet but I'm still a spraying, if I run out of PB Blaster then I have a few cans of WD-40 & Liquid wrench. I figure a day or two before I take the next step of downpipe removal. Quote Link to comment Share on other sites More sharing options...
Arif Posted February 12, 2002 Share Posted February 12, 2002 What is the limit on the 1st Gen BOVs? I plan on running upwards of 17-18psi, will it hold that kind of boost? Quote Link to comment Share on other sites More sharing options...
Len Posted February 12, 2002 Share Posted February 12, 2002 Arif From what I've read 18 PSI is really the Max. So you wouldn't want to use the stock 1g DSM BOV for more than 15PSI, unless you "crush it". You could then get to about 22PSI. Len Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted February 18, 2002 Share Posted February 18, 2002 No, you're thinking of a "Pop-Off" valve, which is a boost limiting safety device that opens under a certain pressure.. Some BOV's can be setup as a pop-off valve, but most of them aren't. BOV's are operated by intake manifold vacuum, rather than intake manifold pressure (although, there is really no such thing as vacuum, it's just a relative term to atmospheric) However, you are correct with your terminology of the CBV. Some manufacturers call a BOV a CBV, with aftermarket manufacturers referring to it as an actual BOV (HKS, GReddy, Blitz, etc...) Quote Link to comment Share on other sites More sharing options...
DAW Posted February 18, 2002 Share Posted February 18, 2002 The Nissan valve is an Emergency Relief Valve, and the Mitsubishi valve is a Compressor Bypass Valve (according to them). DAW Quote Link to comment Share on other sites More sharing options...
DAW Posted February 18, 2002 Share Posted February 18, 2002 I think we're all not on the same page on this topic. BOV term was used but in the context of a CBV, so I assumed that's what was being discussed. A BOV was used on 280ZXT (it's that canister-looking thing on top of the intake manifold towards the rear cyls), it's a fail-safe if the wastegate fails so the engine doesn't blow; not present on Eclipse. A CBV (compressor bypass valve) was not used on the Datsun but was used on the Eclipse. It has a totally different purpose than a Blow Off Valve, it vents boost which is in the piping between throttle plate and turbo outlet when the throttle is closed quickly (like shifting) so that the built up pressure doesn't slow or try to stall the turbo impeller. It's a great feature to have and should be on any turbo'd car, especially manual trans. Nissan just left it off, along with the intercooler. DAW Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted February 19, 2002 Share Posted February 19, 2002 You're right, a Mitsubishi does indeed have a CBV, but it does not relieve pressure if the boost gets too high. The only failsafes Mitsubishi has for too much boost is fuel cut (feels like you've hit a brick wall!!) CBV's and BOV's are pretty much always plumbed into the intake tract between the turbo and the throttle plate, while pop-off valves are oftentimes plumbed directly into the intake manifold after the throttle plate. There have been a number of turbo cars built among the years that have not had a BOV. Archer Racing (6 time SCCA champion for it's class) never once used a BOV on their car from what I remember. Quote Link to comment Share on other sites More sharing options...
DAW Posted February 19, 2002 Share Posted February 19, 2002 yeah, most turbo cars don't have a valve on the intake manifold that blows off if the motor is going to blow up. Maybe that should be called a BUV (blow-up valve). The reason I tried to make a distinction was because posts were coming in with questions like...will my stock BOV handle 18 lbs of boost... as if a CBV (aka BOV) were going to act as a safety valve and limit boost. That's not what it does. When operating at WOT and high boost, the valve is held closed by a spring and the diaphram is seeing the same pressure (boost level) on both sides because the signal is from the same big chamber (turbo outlet, intercooler, hoses, intake manifold) with the throttle plate open. If the throttle plate is slammed shut, then that signal (from intake) becomes a vacuum signal and helps the residual boost under the valve push against the spring and the boost is loose..zzzzingh! so that it makes a cool sound instead of worsenning turbo lag when the throttle is reopened. This is just a clarification. Better one long diatribe than scores of posts all using the same terminology but meaning completely different things. DAW Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted February 19, 2002 Share Posted February 19, 2002 ahh...yeah, I see what you mean. LOL, actually, now that I think about it, you can actually use a 2G Eclipse BOV as a popoff valve...they just refuse to stay closed at anything above 12psi and make it very difficult to build boost past that point... Quote Link to comment Share on other sites More sharing options...
DAW Posted February 19, 2002 Share Posted February 19, 2002 It may be that the valve surface itself presents enough surface area that at high boost it augments the ported signal going to the underside of the diaphram, and is overcoming the otherwise equalizing pressure on the top side of the valve. If the valve is flipped over, you can see a small opening which is ported to the underside of the diaphram. I'm wondering if a fix on high boost cars would be to place a restrictor in that port to reduce it's contribution wanting to unseat the valve. This isn't solely speculation, I have a valve in my hand and when the ported signal to the underside of the diaphram is eliminated, the closing force of the valve is definitely increased. What might be a better fix would be to plug the underside port altogether with a ballbearing, or a base gasket that occludes the port. A small hole should be drilled into the port column which runs along the side of the valve so that there's not an airtight compartment which would require force to compress its air. I think this modification might fix the unwanted pop-off of the BOV, but at the expense of some of the original function of the valve because it needs a stronger vacuum signal now to open as intended. Many turbo'd cars use electric vacuum pumps, solenoids, and/or reserve tanks for various signals; maybe a throttle switch to send a vacuum signal to the BOV between shifts would work. DAW Quote Link to comment Share on other sites More sharing options...
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