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Thank you for the info. I have that exact BOV. I followed your directions and it made a world of difference. Thanks again!
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #22
Update:

I got the 3SX generic "like Greedy Type-S" blow off valve.
Also ordered the barbed plug linked in this thread previously.

I am venting to atmostphere now... its audible in the car (windows up) but not obnoxiously loud.
No more HOOOOOOOting when Im driving around, and it generally FEELS better. (im guessing it was very rich before)

My car still does not run as it should, often missing... but its much better!
I suspect I still have vacuum leaks (among other issues)
 

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It will never run properly with an atmo BOV and an airflow meter. If you want it to run properly you'll need it recirculating.
 

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So I read this post when you posted originally and realized that my plastic OE BOV was shot and it was hooting. Lmao. Thought it was a weird noise.

Searched Facebook market place and Craigslist for Evo 8/9/X parts and found a OE Mitsu BOV from someone. Picked it up an Evo X metal one for $80 and it hooks up almost identically to the factory original.

Lol!!! I didn’t realize how much of a boost leak that was until afterwards. She really woke up allot.
 

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They all hoot, they're supposed to. I've never seen a "shot" one either. The only problem with a stock BOV is that it'll open and leak at about 13 pounds boost. If you're running less than that there's no problem but more boost than that then the easy cheap way is to modify it which takes about 5 minutes and costs nothing .Once modified there's no limit to how much boost it'll hold without leaking. All factory mitsubishi BOVs open at a preset pressure. The evo3 type opens at a higher pressure than the 3k / GTO ones as do the evo x type metal ones, they're all easy to modify.
 

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Well kewl. Have had one VR4 prior to this one and it’s plastic BOV never sounded like this current one did

Also, with this current VR4 with partial/full throttle it just seemed like it was lacking some oomph.

Immediately after putting in the Evo BOV the throttle response and oomph was what I remember it being in my other VR4. Boost feels constant mid/upper rpms now too.

Also, the old plastic one was leaking under boost it seems.

The plastic flapper valve inside of Plastic BOV also didn’t look like it was seating evenly. Was kinda tilted.
They all hoot, they're supposed to. I've never seen a "shot" one either. The only problem with a stock BOV is that it'll open and leak at about 13 pounds boost. If you're running less than that there's no problem but more boost than that then the easy cheap way is to modify it which takes about 5 minutes and costs nothing .Once modified there's no limit to how much boost it'll hold without leaking. All factory mitsubishi BOVs open at a preset pressure. The evo3 type opens at a higher pressure than the 3k / GTO ones as do the evo x type metal ones, they're all easy to modify.
 

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Yea, I’ve seen the crushed BOV’s from DSM days. But can’t really crush the plastic ones.

And with how many times I know I’ll be taking the intake in and out in future having the plastic in there just makes one more thing to break and leak.

They all hoot, they're supposed to. I've never seen a "shot" one either. The only problem with a stock BOV is that it'll open and leak at about 13 pounds boost. If you're running less than that there's no problem but more boost than that then the easy cheap way is to modify it which takes about 5 minutes and costs nothing .Once modified there's no limit to how much boost it'll hold without leaking. All factory mitsubishi BOVs open at a preset pressure. The evo3 type opens at a higher pressure than the 3k / GTO ones as do the evo x type metal ones, they're all easy to modify.
 

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Crushing is the incorrect way to try to fix it. There's just one hole needs drilling in the plastic and another hole to fill. Google will put you on the right track.
Maybe your old one was just broken by the previous owner?
 

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Nah, you crush the metal ones.

Plastic one I’m just throwing in the recycle bin. Lol. Not gonna bother with it. May just throw it in my box of parts actually.

It wasn’t holding pressure.
 

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91 VR4 wish scissors BBK wheels and tint
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Discussion Starter #32
It will never run properly with an atmo BOV and an airflow meter. If you want it to run properly you'll need it recirculating.
As an update, I did get the "generic type S like" from 3SX:
it had it setup as both recirculating and to atmosphere... I didn't notice a difference .
to note though:
my car is basically stock, and even though Its getting better all the time... it still isnt running perfect.
Also, my right arm is 90% paralyzed (motorcycle accident) so Im not exactly banging gears...
 

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You need a datalogger so you can check the fuel trims.
Eg if there's an air leak pre turbo, it'll want to run lean so the trims will peg out at 118% or so.
If the idle fuel pressure is too high then it'll want to idle too rich and the fuel trims will decrease, to 88? or whatever and stay there, Old cars, the o2 sensors die and cause it to run rich, that's easy, look inside the tailpipe, it's black .There's always more than 1 problem.
 

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Discussion Starter #34
You need a datalogger so you can check the fuel trims.
Eg if there's an air leak pre turbo, it'll want to run lean so the trims will peg out at 118% or so.
If the idle fuel pressure is too high then it'll want to idle too rich and the fuel trims will decrease, to 88? or whatever and stay there, Old cars, the o2 sensors die and cause it to run rich, that's easy, look inside the tailpipe, it's black .There's always more than 1 problem.
Curious, my plugs look PERFECT.
but the tailpipes are pretty black (more than my tuned ecoboost truck)
on the stock exhaust tips i see the shorter one obviously putting soot on the longer tips.

when you say leak pre turbo what does that include?
 

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Have you replaced your O2 sensors?

They may only pop a CEL if the heaters are done for.

If you have a data logger you can monitor them and see if they are slow, okie or dead.

Curious, my plugs look PERFECT.
but the tailpipes are pretty black (more than my tuned ecoboost truck)
on the stock exhaust tips i see the shorter one obviously putting soot on the longer tips.

when you say leak pre turbo what does that include?
 

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Discussion Starter #36
Have you replaced your O2 sensors?

They may only pop a CEL if the heaters are done for.

If you have a data logger you can monitor them and see if they are slow, okie or dead.
I have not done the sensors.

what "heaters" ?
 

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The O2 sensors have internal heaters....

How it Works
The O2 sensor works like a miniature generator and produces its own voltage when it gets hot. Inside the vented cover on the end of the sensor that screws into the exhaust manifold is a zirconium ceramic bulb. The bulb is coated on the outside with a porous layer of platinum. Inside the bulb are two strips of platinum that serve as electrodes or contacts.

The outside of the bulb is exposed to the hot gases in the exhaust while the inside of the bulb is vented internally through the sensor body to the outside atmosphere. Older style oxygen sensors actually have a small hole in the body shell so air can enter the sensor, but newer style O2 sensors "breathe" through their wire connectors and have no vent hole. It's hard to believe, but the tiny amount of space between the insulation and wire provides enough room for air to seep into the sensor (for this reason, grease should never be used on O2 sensor connectors because it can block the flow of air). Venting the sensor through the wires rather than with a hole in the body reduces the risk of dirt or water contamination that could foul the sensor from the inside and cause it to fail. The difference in oxygen levels between the exhaust and outside air within the sensor causes voltage to flow through the ceramic bulb. The greater the difference, the higher the voltage reading.

An oxygen sensor will typically generate up to about 0.9 volts when the fuel mixture is rich and there is little unburned oxygen in the exhaust. When the mixture is lean, the sensor's output voltage will drop down to about 0.1 volts. When the air/fuel mixture is balanced or at the equilibrium point of about 14.7 to 1, the sensor will read around 0.45 volts.

When the computer receives a rich signal (high voltage) from the O2 sensor, it leans the fuel mixture to reduce the sensor's reading. When the O2 sensor reading goes lean (low voltage), the computer reverses again making the fuel mixture go rich. This constant flip-flopping back and forth of the fuel mixture occurs with different speeds depending on the fuel system. The transition rate is slowest on engines with feedback carburetors, typically once per second at 2500 rpm. Engines with throttle body injection are somewhat faster (2 to 3 times per second at 2500 rpm), while engines with multiport injection are the fastest (5 to 7 times per second at 2500 rpm).

The oxygen sensor must be hot (about 600 degrees or higher) before it will start to generate a voltage signal, so many oxygen sensors have a small heating element inside to help them reach operating temperature more quickly. The heating element can also prevent the sensor from cooling off too much during prolonged idle, which would cause the system to revert to open loop.

Heated O2 sensors are used mostly in newer vehicles and typically have 3 or 4 wires. Older single wire O2 sensors do not have heaters. When replacing an O2 sensor, make sure it is the same type as the original (heated or unheated).

Bob.
 

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Discussion Starter #38
The O2 sensors have internal heaters....

The oxygen sensor must be hot (about 600 degrees or higher) before it will start to generate a voltage signal, so many oxygen sensors have a small heating element inside to help them reach operating temperature more quickly. The heating element can also prevent the sensor from cooling off too much during prolonged idle, which would cause the system to revert to open loop.

Bob.
Once again, your knowledge impresses!

What happens if I unplug both? does it have a failsafe map to run?

and finally Is there a testing procedure?
 

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Bob is the man. Great explanation for the o2 sensors and heater.

When no signal is received from the O2 sensor, as is the case when a cold engine is first started (or the 02 sensor fails or unplugged), the computer orders a fixed (unchanging) rich fuel mixture. This is referred to as "open loop" operation because no input is used from the O2 sensor to regulate the fuel mixture. the car will run rich as a protective measure. If the o2 sensor are old and sluggish it’ll still run rich.

Closed loop the sensors will detect a rich or lean condition and adjust the fuel trims accordingly.

Once again, your knowledge impresses!

What happens if I unplug both? does it have a failsafe map to run?

and finally Is there a testing procedure?
 

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You can use a multimeter or data logger to monitor the voltage output from the sensors. They should change predictively when you play with the throttle you’ll see it fluctuate.

If the reading is constant or is sluggish in response to throttle they are dead or dying.
 
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