2004 T6 Compressor Bypass Valve missing???

[jimmy57]

The bypass was in the central location and they did away with it with the engine revision for 2002 model year. The intake noise was louder, not too bad on S80 but louder on XC90 and the rubber foam lined plastic engine top cover was the sound dampening to address noise. The short version 3.0 T6 engine that came out in 2007 in 2008 models (all P3) had the electric bypass valve on the turbo. I have a pair of integral manifold B6294T turbos and there are no bypass valves on the turbos and the vacuum bypass valve connecting the hard hose to throttle to the fresh air hose just past flex section by MAF sensor is gone on 2002 and later.
Does your scan tool have the ability to display whether the 6806 code is too high or too low description? The code is not specific without that. Too high indicates higher MAF signal than is expected with TCV signal. Too low is low boost with the TCV signal at high control signal. The low performance seems to lean towards it being the too low version. A wastegate diaphragm failure (like weak or broken spring) where the wastegate on one turbo is able to be pushed open and TCV signal is increased to reduce wastegate pressure to get more boost. TCV being replaced should eliminate TCV as source so that is why I mentioned diaphragm. I have seen this code with too high descriptor when the wastegate actuator hose was broken or off..The car ran better than it was supposed to. I can't recall the too low code but improper hose connection to TCV could do it in addition to wastegate actuator failure. I suppose a sticking open wastegate is on the list too.

[Katronite]

Hi Jimmy.

This is what really confuses me, because many sparepart dealers, like the one SuperHerman linked to, shows that the Bypass valve exists on the normal location, all the way up to P3 T6 models.
I believe that it's actually still installed on the first editions of the newer B6294T engine, but removed somewhat later than 2002. I think you can actually find the Bypass Valve up untill late 2003 models, mounted on the hard hose.

Do you know if its comepletly gone, or just relocated?? It seems kind of stupid to remove it, as its actually doing some good for the turbos.. When running automatic, its not at every shift you need bypass, but still... To delete it from a turbo engine, seems kind of stupid...

As I have mentioned earlier, I tried to install a Manual Boost Controller, on the line going from the TCV to the wastegate diaphrams. I put this to 11-12psi. (I guess thats somewhat near the value of the software tune).
This resulted in nothing at all, so I´m really thinking of finding the leak on the pressure side of the turbos. IC, Wastegate flaps and now also the wastegate actuators. (As mentioned, the line from the TCV holds vacum for at least 10sec. I released the vacum myself after 10 sec.)

Last sunday I removed all the hard pipings on top of the engine, to get access to the purge valve. All pipings were ok, without cracks. The same goes for the purge valve. I have not orderred a new purge valve, as an error on that one, would most likely throw some other errors as well as the ECM-6806.

BSR has mentioned that its most likely i'll find the error on the pressure side, as an error on the vacum side, would throw some other errors as well. If theres a leak on the the vacum side, something else will most likely fail.

And that brings me back to the Bypass or overflow valve. Is it completely gone on the later P2 T6 models?? I know that the Bypass Valve (Diverter Valve) was known to fail on those earlyT6 models. But if its gone, and not replaced with something else, I dont need to look for this.

It's really driving me crazy, because 2 things:

1. If some kind of bypass valve still exists, theres a big chance that it's leaking.
2. I cant imagine that Volvo removed the valve completely, without anything to replace it.

Hopefully you can confirm.

[Katronite]

Quick question. Does an OBD2 bluetooth reader, tell the boost pressure that the engine "thinks" it get?? If yes, I could buy one, connect it, and see what kind of boost the engine "thinks" it get, and what kind of boost it actually performs.

Would that be possible, or will this only tell me if the pressure sensor is defective? (I did install a brand new pressure sensor on the IC outlet, but according to the diagram from SuperHermans link, there might be another pressure sensor, and a temp sensor. I havent checked that yet)

[June]

Yes mine shows boost/vacuum number the computer is given via sensor. June

[jimmy57]

P2 all have an intake pressure sensor. 99-01 it was on the tube from intercooler over to the throttle with an intake temp sensor separate mounted next to it. 2002 brought the temp/pressure sensor stuck into a hole on intercooler right in front of where the tube to throttle connects to the intercooler.
The first pic is a 2002. Look just behind the green pinch clamp on hose on end of intake plenum. Now look at the second photo of the 99 engine in that same spot. The 99 has the worm clamp on the hose to the bypass/diverter valve. In 2002 when the hose was changed to delete holes for the temp and pressure sensors it also lost the nipple for the bypass valve. The small turbos are not as at risk from the pressure surge on throttle lift. Turbos did not have bypass valves for many years. One reason that they got them was due to the MAF sensor not being directional. Any air passing through either direction would be measured. Software on newer engine management with much faster processors can deal with MAF signal spike over fuel. The injector cycling is shut down more quickly with a better processor. The engine cover mentioned is only fitted to XC90 and I think it may not have come until late 2004 production T6 models.

[Katronite]

Thanks Jimmy.

That clears out a lot to me, and olso narrows down where to search for a leakage. With the Diverter Valve out of the calculation, I can move on.

Would it be advisable to mount some kind of Diverter Valve or CBV, when the boost hopefully goes up, when I find the leak?? Meaning stock boost at 8 psi might not do serious pressure surge at throttle lift, but I assume that the pressure will eventually go as far as 11 maybe 12 psi with the software tune, when the leak gets solved, and that might do some extra surge and damage to the turbos??

I did get a bit confused with the intercoler diagram from the above link, as it had 2 pressure sensors and a temp sensor installed. On mine the hard plastic tube dont hold all that stuff. I replaced the pressure sensor mounted on the IC outlet, and glad to hear that this is the only one.

You mention the green clamp on the first foto. That exact tube goes to this T-Valve, that I assume is controlling the vacum, comming either from the intake manifold, or the vacumpump when the intake is pressureised. Can this Valve cause a leak, so pressure dissapears this way?? For some strange reason, it feels like theres pressure in the tube going from the T-Valve to the brakecylinder. Shouldnt that allways be at vacum? When the engine is off, and I remove that tube from the T-Valve, theres pressure trapped in the system going to the brakes. (I assume that the tube goes to the brakecylinder.)
The brakes are working fine. A bit mushy, but the car can really brake.
(I'm not 100% sure if its vacum or pressure trapped in this tube. I did only notice a psscchh sound every time I removed that tube. My first thought was "hmmm, was that pressure". I will check that again, next time I'm in the garage.)

Can I block the tube with the green clamp, just to test if this solves anything. In my head, the vacum pump will take over, if vacum is not provided from the intake, but maybe some electronics take over in stead???
If I can build up pressure without the ECM-6806 error, then I know witch valve to switch.

[Katronite]

In combination with this T-Valve (Vacum Switch) theres a Ejector valve installed. What is the function of that one. I know its brake related, but how does it work?? Is it like a non-return valve on one of the connections?

[Katronite]

Hi Jimmy.

I managed to locate the error.

This past weekend, I had planned to pressuretest the IC, and open up the turbos, to check both wastegateflaps, and also the diaphrams.

IC pressuretest was ok, and the diaphrams also ok. Both opening at 6 psi +/- 0,5psi, so that also seemed ok.

Final thing then, was to check the wastegate flaps. To my luck I started with the passengerside turbo. Pulled the exhaust, and the flap was without any damage. But... The flap was completly open... Although the diaphram and arm was shut...
At a closer look, I could see that the axl and the connecting arm (the one with the pin on it) was broken in the welding, so the wastegate flap had basicly no connection to the arm with the pin on it.

This means that the wastegate have been 100% open all the time on turbo 2. (This could be the reason that the car was priced fairly low, if the previous owner expected an expensive defect)
In my ownership (6 months), the car has been working (IMO) fine. A bit sluggish, with some noticable turbolag, but nothing I couldnt excuse with the car being 17-18 years old. At full throttle, it pulled great enough, and could actually pull away from my other Volvo V60 D5 235hp at highway speeds. Not impressivly, but still pull away. (With 272hp and 200kg lighter than the V60, I might have expected more pull, but again, old car.) As mentioned, it was doing 0-60 in 7.8 sec, so no indication of a "missing turbo".

Now I have welded the arm in its original position, reattaced the arm from the wastegate diaphram with a brand new split, and readjusted to opening at 6 psi, and did my first testdrive. (I'm running with stock software, just in case something was wrong).
OMG what a difference... Now the car does feel like a 270hp car, and not an 18 year old grandpa car.
I'm running oct 100 V-power gas (Ron 92 I guess) and now pulls 0-60 in just 6.8 - 6.9 sec (at stock 8.2 psi). My V60 now dont stand a chance at highway speeds. (Its still faster from 0-60, as it runs 5.9 sec) But again, OMG what a difference. No turbo lag, the power is just there, when you need it.
I guess its kind of difficult to tell if your "new" car was running great, if its been defective from the beginning, if you have nothing to compare with.

And I'm suprised that the car can actually run "fine", with only 1 turbo. No enginelamps on, and nothing to indicate anything. Only this ECM-6806 error readout.

This upcomming weekend, I'm putting the BSR tune back in, and exited to see what will happen.

But thanks for all your help. This was a tricky one.

I will post an update when the BSR software is re-installed.