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Old 07-24-2002, 08:45 PM   #1
VetteVert
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Talking Get Steady 15psi boost for $0.00 -more restrictor mods-

OK, first off let me state that this goes away from the idea of trying to keep PTHB situations down like the other 3/16" and 3/16" + bleed methods do. This will have roughly the same problems a MBC has, just cheaper. Secondly, DON'T DO THIS WITHOUT A BOOST GUAGE!

I was riding around with my 3/16" x 1/8" x 3/16" T bleeding boost from the FBC via the 1/8" hole and realized that when the FBC completely closes off, I only got ~10psi of boost. So the 1/8" bleed hole itself gave me ~10psi. I decided to take the FBC out of the equation, and run just the connector/restrictor (acting as a restrictor in this case). I went back to the stock 1/8" connector. Now, my stock connector has a larger ID than the 1/8" section of the T, so I knew I would get > 10 psi. What do you know, it worked

So...PULL THE HOSE

Pull the hose from the connector to the FBC, leaving the connector in the hose connected to the T by the wastegate and intake manifold. This produced the following results ON MY CAR:

1st - 3rd ==> goes straight to 14.6 psi and holds, falling down to a little over 10psi at 7200rpm.

4th ==> straight to 14.8, falling to the same

5th ==> straight to 15psi, falling to the same

No wavering or bouncing around. I also tried the same T mentioned above with one of the 3/16" sides in the hose, and the other two in the open (the 3/16" IDs are smaller than the straight 3/16" connector as well). This was too much, crossing 17psi in 5th. A small port/polish on the factory connector would probably be just right.

Well I'm out for the night. Have fun with this, and I'll catch you in the morning

VV

[edit]
Here is a diagram:


[/edit]
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Last edited by VetteVert; 07-25-2002 at 12:34 AM.
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Old 07-24-2002, 09:07 PM   #2
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I'm trying to follow you on this one. Could you get some pic's of what you did?
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Old 07-24-2002, 09:14 PM   #3
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Quote:
Originally posted by Blue_2K2_WRX
I'm trying to follow you on this one. Could you get some pic's of what you did?
From what I gather, he's using the OE inline connector from the "T" to the OE boost solenoid. He's disconnected the hose going to the solenoid. That leaves the OE connector bleeding to atmo. No ECU boost control. Someone correct me if I'm wrong...

Jim
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Old 07-24-2002, 09:17 PM   #4
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im lost.
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Old 07-24-2002, 09:18 PM   #5
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Talking Give me a minute to post a pic

Quote:
Originally posted by Samirr76
im lost.
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Old 07-24-2002, 09:23 PM   #6
MackDaddy
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Wink Alrighty then!

The hose closest to my thumb (dark black in color,) is disconnected. This leaves the "hose connector" or restrictor if you will, bleeding to atmosphere. The black hose that would usually get connected to the factory boost solenoid is no longer an active part of the system.

In the picture I've posted, you're seeing a 3/16" connector with a bleed hole drilled in it (whole different thread.) The factory hose connector is black in color. Just to clerify....

High res pic here http://images.fotki.com/v7/photos/1/...SCN1260-or.jpg

HTH - Jim

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Old 07-24-2002, 09:26 PM   #7
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what i assume he is saying is this:

replace the 3/16" connector with the stock 1/8" one, disconnect the tubing from the factory T that goes to the factory boost control solenoid. thats it! by doing this to his own car he was able to get 14.6psi in 1st-3rd, 14.8 in 4th and 15 in 5th.

he also tried leaving the 3/16" connector and disconnecting the FBC but he was seeing a peak of 17psi in 5th (hmm thats what I am looking for)


gonna try this tonight when i get out of work

WRX300
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Old 07-24-2002, 10:57 PM   #8
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Total n00b checking in...got sick of just reading about mods like this and decided to try it out.

So...on the way out of work I disconnected that hose, and did indeed get near full boost in 1st, and 0.1mpa in all other gears.

I also noticed that it was very possible to get part throttle full boost (completely understandable) but I found that I never really drive >40% throttle to create such a situation.

I was just considering getting an MBC to acheive just this...basically stock boost levels in all gears. But since I'm a total n00b I think I'll read some more!

-=Eric

ps. This just added to my usual happy walk out to my WRX after work...now I was even happier...parking lot mod time!
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Old 07-24-2002, 11:28 PM   #9
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BTW...i had tried the 3/16" restrictor mod a while back...and got wavering/unpredictable boost levels in most gears...basically looked like crap.

This is a totally different thing...needle slams to 0.1mpa and stays there.

Many folk in the 3/16" mod thread said we'd overboost for sure!
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Old 07-24-2002, 11:35 PM   #10
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WOW!

You've invented........

Drumroll please.........

A bleed valve MBC.......!

WEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!
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Old 07-25-2002, 12:05 AM   #11
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Maybe so but I see a couple of problems.

1. If you remove FBC you have NO FUEL CUT safety.

2. I think you will have an 'open' or 'closed' loop (not sure which one) and you will not be able to compensate boost at altitude or under high temps.

If you have an MBC you can do all these things.
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Old 07-25-2002, 12:20 AM   #12
VetteVert
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Nice sarcasm. I appreciate that

I never said I created anything new here...just that I had tried it and it works. I'm sorry to have taken your time...

To those that care:
Tonight it was cooler outside and I was hitting almost 16psi in 4th and 5th. And I'm going to edit my original post, as I was reading my boost at redline wrong. It is right around 12psi, not 10.

VV

Quote:
Originally posted by Red Rocket
WOW!

You've invented........

Drumroll please.........

A bleed valve MBC.......!

WEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!
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Old 07-25-2002, 12:24 AM   #13
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If you pulled the line going to the factory boost controller, and you are running 14 psi 1-3rd gears, how does the computer know how much boost you are running? Doesnt sound safe to me, but maybe I dont quite understand.......explain

late
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Old 07-25-2002, 12:27 AM   #14
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Default Sorry......

I just found it funny that nobody had picked up on this simple fact.

People just shouldn't get the idea that it is a "safe mod", with no strings attached.......in fact you should use the same care as with a MBC.

But for $0.00, you can't beat how effective it is.

Kevin
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Old 07-25-2002, 12:31 AM   #15
IMPREZIV
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Default

Quote:
Originally posted by Drews_WRX
If you pulled the line going to the factory boost controller, and you are running 14 psi 1-3rd gears, how does the computer know how much boost you are running? Doesnt sound safe to me, but maybe I dont quite understand.......explain

late
Yeah thats what I was thinking!

Although the description is a little confusing too.

Pete
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Old 07-25-2002, 12:32 AM   #16
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Quote:
Originally posted by VetteVert
Nice sarcasm. I appreciate that

I never said I created anything new here...just that I had tried it and it works. I'm sorry to have taken your time...

Sorry I didn't mean to sound like I was being sarcastic.....Just highlighting a couple of points.

Later.
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Old 07-25-2002, 12:33 AM   #17
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Default Plus.....

I think a large number of people on this thread need to do some basic reading up on how the car works before playing around with thier boost control (not you VetteVert). Not that I'm an expert or anything.

Kevin
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Old 07-25-2002, 12:43 AM   #18
VetteVert
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Default Re: Sorry......

The $0.00 was my point, maybe I got lost in my rambling We were trying to make a combination of bleed valve and FBC to allow higher boost, while taming PTHB somewhat. I was afraid to just pull the hose until I noticed what was happing with my "3/16 + bleed" setup.

and it is in no way a safe mod. I tried to get that across first. It is a MBC, just not adjustable.

On another note...I don't think it is coincidence that the factory restrictor keeps boost below 16psi. If the FBC somehow malfunctioned and hung open, this would keep the car from self destructing. (I know the FBC shouldfail in the closed position, but anything can happen)

As far as the other responses...this works exactly like a MBC (which it is, as red rocket noted). Boost isn't "read" from the FBC, incoming air is measured by the MAF.

I just thought for free, it's a great mod. Even if it is a track only mod. Drive around with everything stock, and pull the hose at the track.

VV
Quote:
Originally posted by Red Rocket
I just found it funny that nobody had picked up on this simple fact.

People just shouldn't get the idea that it is a "safe mod", with no strings attached.......in fact you should use the same care as with a MBC.

But for $0.00, you can't beat how effective it is.

Kevin
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Old 07-25-2002, 12:50 AM   #19
VetteVert
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I wasn't aiming that at you, your points are completely valid...except for fuel cut. How is a MBC going to allow fuel cut? How is fuel cut determined? The ECU adds fuel based on amount of air measured by the MAF, so that's covered. But I don't think it measures boost. Does it calculate amount of air/time to determine if it is too much?

VV

Quote:
Originally posted by michaelwrx


Sorry I didn't mean to sound like I was being sarcastic.....Just highlighting a couple of points.

Later.
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Old 07-25-2002, 02:10 AM   #20
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Does the WRX use a MAP (manifold absolute pressure) sensor? If so, it could be using this so the ECU knows how much boost is being produced...
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Old 07-25-2002, 02:21 AM   #21
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In a way this is a good point - Where does the ECU get it's boost reading from for fuel-cut?

For my MBC install I have the following setup.

1. The 'in' end of the MBC is T'd to the BOV line.
2. The 'out' end of the MBC is connected to the wastegate
3. I have only had to remove the line that was originally connected to the wastegate and plug the end with a screw.

Most MBC instructions (mine anyway) said to disconnect the FBC from under that black cover and stick a cap over the end of the nozzle. When I did this with the above setup I was playing around and hit 20psi with no cut.

I have since installed this back in the hope that fuel cut is re-activated as the only line I have pulled off is the wastegate line.


Michael


Quote:
Originally posted by VetteVert
I wasn't aiming that at you, your points are completely valid...except for fuel cut. How is a MBC going to allow fuel cut? How is fuel cut determined? The ECU adds fuel based on amount of air measured by the MAF, so that's covered. But I don't think it measures boost. Does it calculate amount of air/time to determine if it is too much?

VV

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Old 07-25-2002, 07:52 AM   #22
VetteVert
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It could definitely get the kind of data it needs from a MAP sensor, but I have no idea if we have one or not. Don't you usually have one or the other (MAF or MAP/speed density)?

VV

Quote:
Originally posted by 2.0 guy
Does the WRX use a MAP (manifold absolute pressure) sensor? If so, it could be using this so the ECU knows how much boost is being produced...
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Old 07-25-2002, 08:00 AM   #23
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Default We have both

Quote:
Originally posted by VetteVert
It could definitely get the kind of data it needs from a MAP sensor, but I have no idea if we have one or not. Don't you usually have one or the other (MAF or MAP/speed density)?

VV

If I'm not mistaken.

Jim
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Old 07-25-2002, 09:32 AM   #24
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Default It can easily be adjustable

It can easily be adjustable... just put a good quality 1/8" ball valve on the end of the line venting to atmosphere. Close it up when you want less peak boost, open it for more. The only problem with this setup is that when you want to go back to stock (i.e., less boost to combat FBPT), you have to actually reconnect the line to the stock boost controller. Not a real big deal but may be a PITA (pain in the a$$).

As for how the car's ECU controls such things... I've learned that the ECU, when less than 40-60% throttle, will use the MAF signal to adjust fuel for more boost. However, it will purposely run lean in this area as the ECU is trying to achieve good fuel economy. Therefore, when lean conditions are combined with higher boost levels, EGT's will rise to about 1600 F. Now, when you go past 60% throttle, the ECU doesn't try to run so lean because it recognizes that you are "stepping on it" and reverts to a richer fuel mapping, and EGT's decrease slightly. These two modes are commonly referred to as "closed loop" (<40%) and "open loop" (>60%).

You see, the stock fuel controller (FC) has 3 settings - 33%, 66% and 100%. When throttle is less than 33%, the fuel provided is less than 33% as well. So, in idle, you are running 0% throttle and boost and 33% fuel. As you get to 33% throttle and boost, you are running 33% fuel, which is much leaner. Then, when you hit 34% throttle, the map fueling jumps to 66% and you go rich again. This continues until WOT, when the fueling jumps to 100% at 100% boost.

This explains two phenomena with the WRX:
1. the surging felt as you depress the throttle is somehwat due to the amount of fuel being provided.
2. When you run full boost at partial throttle, you can get high EGT's if you have 33% throttle and boost running at 33% fueling. This will create a lean condition and if you stay there for a while (i.e., cruise control) high EGT's might arise. This also explains why some people with MBC's don't have issues - they simply don't drive with such a steady foot as they vary the throttle more regularlily. This also explains why many people with MBC's say that if they "try" to get the EGT's to rise they can - yeah, by keeping the throttle around 33% for a long period of time with the car under heavy load.

Anyway, to sum up, any MBC can work you just have to realize what to do and what not to do. No MBC is really free because you really need a boost gauge and an EGT gauge to do it safely. And, I assume if you're interested in "free" mods, like me, you probably can't afford either...

I may oversimplified this topc and if any of the above is incorrect in any way, please bring this to my attention immediately.
JC

EDIT: I think the reason that the stock boost levels don't result in elevated EGT's (i.e., approx 1400 F) is that less heat is generated at a given A/F ratio and at a given pressure. So, when running higher boost levels the pressure increases, and, even though the ECU may have added more fuel and the A/F ratio may be the same as stock, the pressure is higher so more heat is generated due to higher cylinder pressures and hotter intake charge from a hotter turbo since the turbo is working harder. The EGT's appear to max out about 200 F higher (i.e, 1600 F) than stock at partial throttle BTW. Whether this "slight" increase is detrimental or not is still a topic of debate.

Last edited by thejean; 07-25-2002 at 10:16 AM.
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Old 07-25-2002, 10:06 AM   #25
Darryl
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Default Vettevert

Thanks for experimenting with this mod. I wonder if anyone with an egt gage would care to measure the temps with this mod. I'm going to post this link on Cobb's WRX forum where I passed along the connector mod from having read it here.
teh beat goes on!
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