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B4 VOD reduction


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#1 B4AUS

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Posted 30 August 2015 - 01:49 PM

Looking for some assistance on methods of reducing lag between the b4 turbos. I had read on a thread recently about how modifying the vac lines can have an affect on this area, however I have not been able to find it since. Any links, recommendations on this would be greatly appreciated.

Also, is their anyway of tweaking psi via the vac lines aswell

#2 cowie165

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Posted 30 August 2015 - 02:17 PM

Hey mate,

 

It was at the end of the Guide to Twin Turbo thread:
 

 

LINE #1 MOD

(Used without permission courtesy of ClubSubNZ, cheers cubts)

*Figures given may not be accurate or performance gains guaranteed as this is 3rd party untested information.

Outline:

Insert a 0.8mm restrictor pill into line #1 (Intercooler Air Control Valve)

Benefits:

- Primary boost loss throughout the entire VOD is less than 2psi*
- Primary boost loss to full TT boost is less than one second*
- Completely smooth and powerful transition into sequential operation*
- Stable boost throughout entire RPM range*

Instructions:

- Pull hose # 1 from the top/front port of the BBOD.
- Insert the pill into hose #1, use wire to push it up the hose at least 50mm (2 inches).
- Refit hose 1 onto BBOD.

If you do not have a 0.8mm restrictor pill, the OEM Subaru Part Number is:

0.8mm Pill - 22326AA260
1.0mm Pill - 22326AA010

​ Alternatively, a second-hand unused stock boost control line contains an 0.8mm restrictor from the compressor outlet to tee-piece.

http://www.clubsub.o...nside-the-BBOD/

 

 

Was that the one you're thinking of?


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#3 B4AUS

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Posted 30 August 2015 - 09:31 PM

That's the one thankyou

#4 Dav_fre

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Posted 05 September 2015 - 10:15 AM

Just remove the tee'd vacuum line from the BOV (and plug it off) so the BOV is plumbed straight to the intake and get a retune.

Your boost curve will then look like this, pretty much like a single turbo.

1361d4e179b42f6565183267e477adde.jpg


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#5 cowie165

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Posted 05 September 2015 - 04:31 PM

Yep. That's the line 10 mod from the same post.

 

Dave do you have a better pic of that graph? With the scale on it, and some more info on your engine? RevA-C seems to benefit more from these mods.


"Installation is the reverse of the removal procedure."
 
BH9 02-05 / BD9 07-14 / BE5 14-> / GGA 18->
 
2001 Legacy B4-RSK / 1999 ZX-9R C2


#6 Dav_fre

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Posted 05 September 2015 - 05:22 PM

Here is with the scale

The blue line is before the BOV line change and with only a stainless turbo back exhaust.

979f58f6a0b45519f095af92eaa0b3c4.jpg


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#7 Jimbo

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Posted 05 September 2015 - 05:43 PM

I'm totally convinced the reasoning behind the extra BOV line is purely for economy reasons. This graph shows clear as day, how much the factory BOV leaks. 

Though, I would say the results are probably skewed a bit by the TBE. TT's have funny habits when it comes to consistent  boost.


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#8 Dav_fre

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Posted 05 September 2015 - 05:53 PM

You're pretty much right there Jimbo, the other reason is once it's removed I takes a little of the 'safety' out of de-tuning...in the red line the Wastegate Duty Cycle is 0%...

That's fine for me, it just means you're bleeding out boost at 100% of capacity and still making 20psi (at 6500rpm in sequential mode obviously)

Only mod's are;
Skimmed air manifold,
SS Inductions air intake (big mouth snorkel/de-resonated chamber),
Silicone turbo inlets & outlets,
AVO TMIC,
And the TBE (2.5 & 3inch dumps)


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#9 Dav_fre

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Posted 05 September 2015 - 05:58 PM

Also had a GFB BOV fitted on both dyno runs...so the leak is not necessarily Factory BOV dependant, although I do remember a marginal improvement from the change from Factory to GFB-even before the line 10 change


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#10 duncanm

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Posted 05 September 2015 - 06:37 PM

Jimbo,

I think the hunting/sensitive throttle at cruise is a bigger reason for the Line 10 factory bleed - economy is a second order effect, I guess.

Dave - how does this achieve 18-20psi with 0% WGC? I thought the wastegate spring on TT's was around 7psi.

#11 Dav_fre

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Posted 05 September 2015 - 06:45 PM

You are correct about the Wastegate Actuator Spring being 7psi Duncanm, but your boost solenoid is tee'd in to the turbo vacuum line.

You'd only see 7psi if you ran a straight vac hose


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#12 duncanm

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Posted 05 September 2015 - 08:01 PM

yars -- but 0% WGDC is like running a straight hose.

#13 Jimbo

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Posted 05 September 2015 - 08:03 PM

Interesting about thew WGC.

Going back to the tech notes the ECV and primary WG take turns in boost control. 

During single operation the WG controls boost. During secondary prep, the WG hands over that job to the ECV, and once in full operation the primary WG is active again.

Edit: I'm confused too, now, Dave.

With 0% WGC, VOD would be the size of the Grand Canyon, due to the volume of exhaust being wasted.


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#14 duncanm

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Posted 05 September 2015 - 10:09 PM

Jimbo - yes.

0% WGDC means the bleed solenoid is never open - so boost pressure at the wastegate actuator is manifold pressure - bingo, mechanical actuator boost levels (7psi).

100% WGDC has the bleed solenoid open all the time - boost is then controlled by the ratio of the pill size on the boost line vs the amount of bleed the solenoid can maintain.

https://static.cobbt...rol_System.html

Its a nice fail-safe system - if the solenoid craps out, you don't get over boost, you get safe boost.

#15 Dav_fre

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Posted 06 September 2015 - 08:40 PM

You've got me thinking, I've just picked the car up from the tuner in the last few days...I'll plug in the Delta Reader and get back to you


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#16 KONG

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Posted 06 September 2015 - 08:59 PM

Sounds like a wastegate delete. 



#17 Dav_fre

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Posted 09 September 2015 - 06:07 PM

My bad boys...100% WGDC @ 6500rpm, not 0%

I had it the wrong way around

#18 Legacyrskbe5

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Posted 10 July 2019 - 11:52 PM

Has anyone with a Legacy RSK BE5 D 2001-06 and above have done this? i tried and read the Hose 10 mod is not meant for the Late model D, But this might work?

 

Cheers

 

https://www.instagra...source=ig_embed






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