bov mod
 

ok so i modified my bov because i'm putting a manual boost controller in my 85 300zx turbo. Is there anyway to make the bov too stiff, i believe i have it right because i read about it on franks modification page(google). If i have it too stiff just more boost right? I ordered a gauge i'm hooking it up, as long as i stay around 10 lbs i should be fine right? I also looked at the inexpensive brew system that frank has on his page, anyone think it's a good idea? For now i'm just going to use the brass needle valve, a brass tee, boost gauge, modified bov and bleed to the atmosphere this should be good till i get other parts correct?

you mean your pov?

"pop off valve" is for stock cars where the valve "pops up" to release intake pressure, where a "blow off valve" has the ability to release only a certain amount of pressure at a pre-set level that is set up by the user.

POV= stock, hard to adjust piece of crap, that doesnt sound good.(look at the safety release valve on an air compressor)

BOV= modified, easy to adjust, sounds cools, looks good, will make people crap their pants, cant be set to only release a certain amount of boost..

if you want a BOV because of the sound, you're a ricer. You buy a BOV for the function, not for the sound.

POV is also called an EMERGENCY relief valve. And that's exactly what it's for. It's there in case the wastegate fails. It's to help prevent you from blowing up your engine. A POV/ERV goes after the throttle body and relies solely on manifold pressure to force it open. Do not rely on this to control boost. Most open at a certain pressure and don't reclose until a much lower pressure.

A BOV goes between the turbo and throttle body and relies on a few variables to help make sure that the turbo doesn't stall when you take your foot off the gas when the turbo is spooled up. This is to prevent an excess buildup of pressure in the intake piping as well as allow the turbo to slow itself down rather than nearly suddenly stop when the throttle is closed.

They are NOT the same thing. One is for the turbo. The other is for the engine. You really should have both.

Ignore hoov100. He is a little confused.

yes pov i'm sorry about that. I completed the bleed to the atmosphere and i got around 7 pounds of boost and 8 max. I was hoping for more but thats all i could seem to squeeze out. If i upgraded to a bigger turbo what should i get? Also should i get a better intercooler first?

dont most people... just eliminate teh POV and rely on teh wastegate actuator... that what all cars do any ways besides teh 280zx turbo... why does it have to be different?

A stock Z31 turbocharger can go WELL above 8psi. You've obviously overlooked something in the system.

#1... To increase boost, you need some way to adjust when the wastegate opens (hence the need for your boost controller). Manual boost controllers SUCK and aren't reliable. Get an electronic one. :D

#2... If you keep the POV (emergency release valve) installed, it WILL limit how much boost you can run. Once it opens (which sounds like @ 8psi for you) it will bleed off excess boost... How did you adjust the POV? Did you add a washer under the spring?

I SUGGEST READING THE BOOK MAXIMUM BOOST BEFORE TOUCHING YOUR CAR AGAIN :D

Yes, most people cap the POV if they have built a strong reliable setup.

I removed the POV on my car. Using a manual boost controller set to 11psi. No issues yet. My next set of mods will be an intercooler and a bypass valve. Then and only then will I up the boost any further.

if your in North Carolina it should be getting cold... you probaly can run 15 at night if its around 40 degrees and be fine... I have and had no problems... they say its more of that you dont have enough fuel past like 12 or 13 PSI, and you have a 86 which is a t3 so you have more options than say a crappy t25 :P

i modified the pov by drilling a hole above the spring in the plate(after you disassemle it) and placing a 30mm spring in to stiffen it up, it definatly did get much stiffer. I just dont see what i could have over looked, there just isn't much to overlook on this bleed off. I cut the hose from the turbo to the wastegate and put a barbed t in it and then used hose clamps, hooked the two i cut onto the t and then another hose on the top side of the t and hooked my needle valve to it, the only thing is how i have the needle adjusted and i'm sure that doesnt do a whole lot. Any suggestions

get a real boost controller...

i was told not to waste my money on a boost controller, but i guess everyone has their different opinions

The POV is NOT a boost controller. It's an emergency valve for if/when the wastegate on the turbo fails. It prevents overpressurizing the intake when the wastegate is stuck closed (for what ever reason).


And for what it's worth, you can't run any boost over stock without any form of boost controller or shimming the wastegate actuator (to stiffen the internal spring).

No offence, but a bleed is one of the worst forms of boost control to use. They can creat spikes and horrible inacuracies with different temperatures. I have been using Grainger type valves for the past 6 years on my turbo cars. I've found that they do not spike at all. And, if you keep the vacuum/boost signal lines short, they are very fast to react.

By the way, did you install a restrictor (oriface) on the wastegate line before the "T" fitting, bleed, and wastegate actuator? If not, then the bleed is worthless. You won't be able to slow the flow of the air from the source enough for the needle valve to do it's job.

Just my $0.02,

Who ever told you that is an idiot.

+1

Who ever told you that, doesn't understand the concept of a turbocharged setup.

good thing i have the luxury of zdriver then. I will be purchasing a boost controller then, thanks guys, well i guess could be girls too. Shouldnt there already be a orifice installed on the line already ?

Not necessarily. I've never seen one in the vacuum schematics of the 300zxt's. I know my old dodges had them. Only because it used a bleed type boost control setup from the factory. I think the 300zxt's are only controlled by direct vac/boost to the actuator from the source.

by the way which is the best manual boost controller to buy? I was told turbo xs is a good one to buy. I was looking on ebay and i saw some by the brand of voodoo and others similar, is there crappy ones and great ones?

if they're built right, they're all good.

I'm personally using a ball check-valve unit from Grainger. Added a couple hose barbs on it. And drilled a vent bleed on the one end.

I don't have any personal experience with the ebay units. Nor any with the TurboXS units. But the one's I've used worked well for me.

The unit that I currently have installed on my 300zxt is from 3 Bar Racing. Here is the link to the unit. http://www.3barracing.com/product_7.htm

That's the Grainger check valve that's been modified to work as a manual boost controller.


Enjoy,