Loss if power/boost after gear change

[montez]

The car has a problem where by if I change gear after 5000rpm and go back onto WOT the boost hovers around 0.3 - 0.4 bar then after a second or two it picks back up to about 1.1 bar. I have tested this in 1st to 4th gear and I get the same.

I see about 1.1 - 1.2 bar in each gear which I am guessing is not high enough for a homefries 3B, so maybe the two problems are related.

[Rusty]

What DV do you have? Sounds like it's tired...

[montez]

Replaced it about a week ago with a forge 007p with yellow spring, did not really make a difference just ran smoother.

[driftin jo]

Did you replace the vacuum line to the DV ? If not it could be the cause as it may have collapsed internally , this would cause it to hold vacuum for a few seconds after you get back on the throttle causing the DV to stay open for a bit.

[montez]

That was changed by a silicon one about 2 months ago, you can hear the dv opening so I am guessing it is working ok.

One other thing I have seen and am unsure about is the placement of the DV, I have seen some pictures of early 3B's with the DV attached directly to the maf to turbo hose, mine is connected to the turbo to inter cooler hose, is this correct?

[driftin jo]

It should be between those two hoses, so when it opens it dumps boost back to the MAF to turbo hose.

I take it you are dumping to atmosphere ?

[montez]

No it is a diverter/recirculation valve

[newsh]

So the end opposite the vac line goes to the Turbo-IC hose and the side outlet goes back into to the MAF-Turbo hose.

[montez]

I have tried the dv in both positions and I get exactly the same thing both ways around, the car feels better with the dv in the reversed position as it feels less laggy at lower revs

[S2central.net]

@montez - I just PM'd you about this... can you post a photo of how you have it fitted... The 3B hoses are a bit convoluted to say the least and I know access is tight for a photo but something is silly wrong here.

Make sure the DV only flows air when you are sucking on the control pipe... it must be shut all other times.

[montez]

Here is the photo

Paul I PM'd back

[S2central.net]

This is another reason why I like to do the boost test at that intercooler hose - you can pressurise to say 1bar - with the system blocked before the throttle body. Then using a vac pump (or sucking the tube with your mouth - gross I know but needs must) you should hear that pressure moving to the MAF hose as the DV/TBV opens.

I think you might have leaks in the control pipes... if it is old original braided stuff then deffo replace it with good 4mm silicone stuff - do it carefully a piece at a time if you are unsure about the routing/purpose of all those hoses... There are some 1-way valves and stuff related to this for the cars vacuum reservoir and aircon (where fitted).

You can do a quick check by removing each control hose from the manifold and applying boost or vacuum to see if its airtight - again vacuum is easier with your gub if you dont have a hand pump.

Search here for 'vacuum tree' and you should find a diagram for the control hoses - cannot remember if I posted 3B and ABY variants here - but note there are some little differences so don't use an ABY as gospel - it is just a guideline.

[montez]

I have replaced the majority of the control hoses already so I will continue to do the last few awkward ones! I will have a go at your way of boost leak testing next weekend I just carried on with mine for now as I could hear a prominent leak which has now been fixed. Its just really frustrating as it feels like the car is almost there, I will be at Castle Comb this weekend with the forum so seeing and hearing the car may just trigger an idea from someone.

[S2central.net]

FOund this in the archives ---> http://www.s2forum.com/forum/attachm...8&d=1201606537

[montez]

Cheers I will systematically go through that mid week as I got a day off, Does anyone know roughly what length of 4mm hose I would need to do the whole system?