Discussion in 'Fiesta ST Chat and Discussion' started by D1JL, Jun 4, 2014.
Fiesta ST with BOV
I like it. I do miss however the sound of my old 88 Toyota Supra with a Tial wastegate... that sounded mean
I can already hear the bypass valve with the Cobb 93 tune and an induction hose and K&N filter. It's not as loud as the video, but definitely noticeable.
I like the sound but don't want the drawbacks of a vent to atmosphere BOV.
A wastegate is an entirely different sound and would require a major exhaust manifold rebuild and special tuning.
What drawbacks do you speak of?
To my knowledge, both systems do the same thing.
Just one is much harder to hear.
I have all the same things and I don't hear anything.
Maybe that's another post for the Old Farts thread, "Can't Hear".
This was done for another person that asked me for it.
I just proved that it could be done but I am not the first.
It basically is just for the sound as all the OE systems are still connected.
Yes it is a BOV but is just an overdone Sound Symposer.
I can definitely hear the turbo spool and the bypass. You're running the 91 MAP due to lack of availabilty of 93 octane, right? I am running the 93 map.
I have run both the 91+ & 93+ maps.
Although it is true we do not have 93+ at the pumps, we do have 100 octane at some locations.
It is just more pricy.
The CRV (compressor recirc valve) on the stock turbo routes the recirculated air right to the front of the compressor wheel, which keeps up turbo speed during the shift and doesn't open the system. A BOV sends the air to the atmosphere which the computer doesn't realize so the ECU adds unnecessary fuel, causing an overly rich condition. With a CAI I think a CRV is plenty loud anyways...
I am not defending or condemning either system.
However I still believe that they are doing the same thing.
The CRV relieves pressure by venting in front of the compressor.
This is atmosphere but just the inside of the air filter.
And noise is controlled.
The BOV vents to atmosphere however before/outside of the air filter.
In both systems at the point of operation the throttle plate is closed.
Therefore pressure must be relieved to prevent compressor stall.
Since the throttle plate is closed, nothing gets to the intake and the ECU sees nothing.
Agreed, but assuming you want to get back on the throttle quickly after letting off (shifting or on an autox/road course), then if the turbo speed doesn't drop off as much you have a performance advantage, and you don't have extra fuel dumped into the cylinder which will mess with the mixture when you get back on the throttle, delaying response further. Sure it might not be a big difference on a small turbo but small things like that do add up.
Even with a CRV you are just dumping the air into the intake pipe and it will take the path of least resistance, that is out the bigger hole and out the air filter.
Also remember that when this is happening the throttle plate is closed.
Therefore no air extra air is getting in the intake manifold, so no extra fuel can be dumped.
With all turbo systems you will get some turbo lag this can not be avoided.
With proper parts, adjustments, and tuning you can get rid of most of it.
The throttle isn't completely closed, the engine is still pulling a significant vacuum. No air is going to turn around and go out the air filter!
I am not arguing with you just to argue?
I am trying to understand.
Because what you say defies what I was taught.
If what you say is correct and the throttle plate is not closed then the engine cannot draw a vacuum because it is still receiving air (vacuum means no air).
Therefore the ECU would see the air and add fuel to prevent a lean mixture.
If on the other hand the throttle plate is closed as commanded by throttle peddle/ECU.
The engine draws a high vacuum (deceleration) you can watch your boost gauge and see this.
The MAP sensor sees vacuum and adds no fuel.
Now it is possible, as it has been a very long time since I took a science class, that the laws of physics may have changed.
But any contained gas will exhaust through any possible path.
No, the laws of physics haven't changed. The engine will not continue to run even at idle if the throttle plate is completely closed and the engine isn't getting any air.
Derp derp derp
I understand that.
However this is considered closed and only adjusted by the stepper motor to keep the engine at idle.
The rich condition only occurs if the engine is running a MAF sensor, MAP systems or speed density if you like, can compensate for a BOV.
As I stated above this was only tried because someone asked.
They wanted to add the sound and I had all the parts.
As it turns out because of our tiny turbo it is hardly worth the cost of parts.
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