How To Increase Primary Boost - I Have The Answer!, B4 / GT-B Twin Turbo BE5 / B

[Garryg]

I found this on a UK Legacy Site.....Anyone tried this here??

What's your thoughts?? THIS IS NOT FROM ME.....(just in case someone tries it and it goes wrong!!)

"All the information that follows relates to my GT-B BH5 TT Estate but may well be relevant to other models.

As probably most of you are aware, as standard, twin turbo's run a lower boost on the primary turbo (~7psi - ~11psi) and a higher boost when running on both turbo's (~13psi - ~16psi).

Since having my car ECUTEK remapped my primary boost achieved has remained exactly the same at ~11 psi and my twin boost achieved has increased from 1 bar to 1.25 bar (~15psi - ~18.5psi) with a corresponding increase in top end performance. The guy who remapped my car (Bob Rawle) said that he set both of the boost 'target' maps to 1.25 bar (i.e. there is a boost map for primary turbo mode and a different boost map for twin turbo mode). As mentioned above despite increasing the boost 'target' map for the primary turbo there was no physical difference to the actual boost my car was achieving when running in primary mode.

Prior to the ECUTEK remap I don't know what the primary target boost map was set to but I would guess 1 bar, i.e. the same as the standard twin turbo target boost map. However, I know that on my car, as a result of the ECUTEK remap, both the primary and twin turbo target boost maps were increased to 1.25 bar.

Bob said that he was going to investigate and get back to the people, who's cars he had remapped, so that he could attempt to increase the actual primary boost achieved. After a year of waiting I thought I would investigate myself to see what was going on in the system preventing the primary boost rising above ~11psi.

After a couple of weekends of testing I have discovered that the system is plumbed in such a way so that the system is physically ‘naturally’ limited to ~11psi and that the boost achieved has nothing to do with the control of the ECU. If the ECU had it's way then primary boost would rise, in my case, to 1.25 bar and with a standard unmapped ECU 1 bar.

After testing many different scenario's and lots of runs up and down the road I have now successfully come up with a solution that now gives the full 'target' boost whilst running in the primary mode (1.25 bar ~18psi) as well as the full target boost in twin turbo mode (1.25 bar ~18psi). There is no 'bleeding off' any air to atmosphere and the system still has full 'closed loop feedback' control.

Before everyone starts saying 'what about overspooling the primary turbo' the answer is, as a result of this modification, I don't know how close to the limits of the primary turbo’s capacity it is now running. However, what I can say is that the boost rises very quickly to 1.25 bar and it holds it there very easily, so my guess would be it is still within its limits.

The car has been transformed in terms of primary turbo performance and goes like a rocket up to 4000 rpm as well as going like a rocket above 4500rpm (after you get over the VOD!)".

""And here is the answer!

Donations gratefully received for all my hard work (& several burnt fingers and small cuts on my hands!)

Surprisingly the answer does not lay with the boost controller end of the system (as you might expect) instead the answer lay with where the exit of metal pipe 10, from the solenoid box, goes to.

This basically needs re-routing to change the dynamics of the system so that the full primary boost pressure can be achieved.

Take a look at the two attached pictures (you may need to adjust your browser to view these at 100% zoom level so that you can read the text).

The pictures are of a before and after the modification and are hopefully self-explanatory as to what you need to do. The whole mod should take you about five minutes if your pipes are not 'stuck' on"".

http://www.uklegacy.com/forums/index.php?showtopic=7815&st=0

Pictures are at this Link.....and more details.........

Interesting!!!!

[aim]

can you download the pics and post here? as we have to sign up to see it

[Garryg]

If someone can PM me there email address, I 'll email the pics then they can add them...I can't do it from work....

The thread goes on to say thay no other modifications are required to achieve this...no re-mapping, etc

Cheers

[pharnos]

Here's the pics from the UK Legacy forum...

[Garryg]

Thanks........

[Pappu1]

i have heard of some other TT guys doing this mod and they say the car boosts much better.. have not personally done it or been in their car so only taking their word for it..

perhaps some CS member wants to try on their TT ... 8)

(and report back.....)

[Carbon]

I might give it go - although Im just trying to work out if the plumbing shown is actually the same as my rev c

[ReubenH]

1.25bar within the primary's limits? I doubt that.

I'm just going to say this. If you mess with these TT systems, without knowing how they work, they are likely to bite back. Pick up some technical info on how they work before fucking with them.

http://www.veloce.pwp.blueyonder.co.uk/technical%201.htm

[Joker]

that 'seems' cooler than that onegreeky fellow just unplugging a line.. (free boostin it)

[Hailz]

 ReubenH said:

1.25bar within the primary's limits? I doubt that.

I'm just going to say this. If you mess with these TT systems, without knowing how they work, they are likely to bite back. Pick up some technical info on how they work before f***ing with them.

http://www.veloce.pwp.blueyonder.co.uk/technical%201.htm

Bloody good call!

I dont know all that much about this buuut I've been told that alot of suby engine failure is caused by the injectors not keeping up with the amount of boost being expected of them, here's a thought - would the computer tell the injectors to up the amount of fuel for that primary turbo boost of 18psi or will you eventually end up leaning it out and then needing a new turbo soon after?

Although I am rather keen to give this a try for a short wee boost or two ;D

[telemekas]

The AUDM BE5 Rev D is essentially set up this way (after diagram) from factory.

No metal pipe 10 just a rubber hose into the intake with step-up hose just before 2nd turbo.

Rubber hose 10 with step-up hose into intake just before primary turbo.

[ReubenH]

 Hailz']

[quote name='ReubenH said:

1.25bar within the primary's limits? I doubt that.

I'm just going to say this. If you mess with these TT systems, without knowing how they work, they are likely to bite back. Pick up some technical info on how they work before f***ing with them.

url]http://www.veloce.pwp.blueyonder.co.uk/technical%201.htm[/url]

Bloody good call!

I dont know all that much about this buuut I've been told that alot of suby engine failure is caused by the injectors not keeping up with the amount of boost being expected of them, here's a thought - would the computer tell the injectors to up the amount of fuel for that primary turbo boost of 18psi or will you eventually end up leaning it out and then needing a new turbo soon after?

Although I am rather keen to give this a try for a short wee boost or two ;D

The injectors inject the right ammount of fuel for a given ammount of air that goes through the AFM, so yes, they keep up. The problem lies with when the injectors reach 100% duty cycle, and are pumping as much fuel as they can, after that is when you lean out. All BG's that aren't manual GTB's have grey injectors that will have difficulty with 18psi. However, all manual GTB's, and all BE/BH's have yellows, which can keep up with the demand.

Also note, 18psi on primary ≠ 18psi on both. The primary boost may show the same on your boost gauge, but it's flowing far less air than when both are working, so yes, the injecotors can EASILY keep up with it if they are yellows (grey's probably could too)

But have any of you guy's seen one of these turbo's on their own!? They are tiny! On their own, they'd be pretty much at home on a 1L at 16psi, making them do 18psi on a 2L is just pure torture! Man, i have big ol VF39 to do my 18psi... Ok, sure, it's only at low revs that the primary is boosting that much on it's own, but still, it's allot to ask of your primary.

[Hailz]

My primary's a VF31 off a BH would that make any difference or have all Legacys been whacked with the tiny turbo stick? Alsoooo, having 18psi on tap all the time would surely put more stress on the motor thus making it do the BEB far sooner? Am I right? ???

[ReubenH]

Yes, all TT's got slapped with the tiny turbo stick, that's what happens when you put 2 on a 2L. And you're especially tempting fate with an EJ20R too, given their reputation.

What boost does the car make at the moment?

[GravelBen]

AFAIK the VF33 primary on the BE/BH Rev-D is bigger than any of the earlier ones?

[Hailz]

 ReubenH said:

What boost does the car make at the moment?

I would'nt actually know, never had a gauge on it ( I think they're tacky ) But it does go bloody good ;D

[ReubenH]

Tisc tisc, one should not even consider touching anything turbo related under the bonnet till they have a gauge.

If you think modyfing is going to become your game, invest in a good gauge so you know what your car is doing. Get to know what your car is doing, how it does it's thing, well before you mess with it!!!

[Carbon]

I use tari racing software and a tactrix cable - logs all the info you need when messing around.

Shame the ECU is not writable though

[Guest]

 telemekas said:

The AUDM BE5 Rev D is essentially set up this way (after diagram) from factory.

No metal pipe 10 just a rubber hose into the intake with step-up hose just before 2nd turbo.

Rubber hose 10 with step-up hose into intake just before primary turbo.

I can confirm that my Rev D makes and holds 1 bar on Primary and it was peaking at 1.05 yesterday (gotta reset my warning light as it has defaulted back to 1 bar lol!).

[Hailz]

 ReubenH said:

Tisc tisc, one should not even consider touching anything turbo related under the bonnet till they have a gauge.

If you think modyfing is going to become your game, invest in a good gauge so you know what your car is doing. Get to know what your car is doing, how it does it's thing, well before you mess with it!!!

Hmm good point, might invest in one so I can look all boy racey lol, Reuben I've been told that my model is the latest revision of the BG5 with the limited front ect (like yours) and they had a different ECU setup - no secondary wasegate ect and different boost settings is that right? I drove three before I brought mine and mine was definatley the best performing one and standard too, the others were pre 97 model.