TCV Routing Confusion: red = turbo, and blue = fresh air?

oh-la-la · Post by **oh-la-la** » 09 Sep 2010, 16:19

Hi guys,
I have searched for TCV diagram for my 95 Volvo 850 T5 but getting confused with these 2 diagrams. When i look at both of my cars the wastegate actuator has been marked yellow and also the vacumm hose has a yellow sticker on it. That makes sense if i follow the frist diagram, yellow line will go to the top port of TCV but! the second diagram showing the wastegate vacumm hose must run to the buttom port of TCV. So, this making me confused which diagram should i follow?
Thanks guys for your helps.
TCV and frist diagram, yellow wastegate hose goes to the top port

Second diagram the wastegate actuator hose must run to the buttom port of TCV

Post by **jblackburn** » 09 Sep 2010, 17:03

I think they kept it the same between the years - yellow should go to the wastegate, red to the turbo, and blue to the fresh air hose.

The turbo control valve on my S70 is shaped a little different, but is set up in exactly the same way.

oh-la-la · Post by **oh-la-la** » 09 Sep 2010, 17:17

jablackburn wrote:I think they kept it the same between the years - yellow should go to the wastegate, red to the turbo, and blue to the fresh air hose.

Thanks for your help! Then i should stick with the frist diagram?
Actually i have run with both setups. Routing with frist diagram will give slightly more boost and boost spikes up and settles back between each gear shifts while the second diagram will give slightly lower boost but stays constantly between gear shifts.
So which one sounds normal for you guys?
Thanks again

Post by **thecheat** » 09 Sep 2010, 17:24

I wonder if the differences in the top and bottom hoses affecting boost is similar to how the aftermarket turbo valves for the mk4 vw 1.8 turbo work if you reverse the valve. Nothing much changes except the noise of the valve opening because it still acts as an on off switch but the airflow is changed if it is reversed.

oh-la-la · Post by **oh-la-la** » 10 Sep 2010, 04:00

Even diagram from this pdf file also get mixed up between page 2 vs page 4 and 5
What is this!

Post by **jblackburn** » 10 Sep 2010, 07:19

I think it's normal for it to spike a little bit on shifts (maybe up 2 psi or so). The CBV then recirculates the extra boost. I only had a boost gauge I borrowed for a couple days from a friend while I was trying to figure out what was going on with my car.

SimLyons · Post by **SimLyons** » 28 Apr 2011, 23:22

Yeah, I'm also confused. Justin, this is the thing I was trying to describe that mounts on the bottom of the air filter housing. It has 3 vacuum hoses and an electrical connection. The blue hose, center, should go to the air intake piping, above the Turbo is that correct? and the electrical connector comes from some loom somewhere. I still have to find that one.

SimLyons · Post by **SimLyons** » 28 Apr 2011, 23:25

Oh...and one of the drawings shows a blue center hose. Goes to the fresh air intake piping whatever that device is. That's where I put the center hose and hope all the pothers got connected well enough.

Post by **ojdorson** » 29 Apr 2011, 09:03

The two diagrams say the very same thing. The problem occurs in the second image where the "artist" made color choices that don't match the markings on the BCS. Here is the image properly colored.

: Turbo-proper colors.jpg (63.49 KiB) Viewed 14217 times

Of course, the BCS pictured is "upside down" compared to the one in your hand in your picture.

SimLyons · Post by **SimLyons** » 13 May 2011, 18:21

I was getting frustrated looking for the cause of relatively low boost after doing all the other stuff. Today I did the "sea-foam" treatment into the intake as described by Justin. Lots of smoke and nice smooth engine, but no joy on boost. Same "80%" of what should be.

So back to the garage and off with the intake so I could see. Yep! A hose not connected to anything! It's from the turbo by-pass valve. I can't find where it is supposed to connect on the other end! (I hope not to the intake manifold....I did connect that before replacing the manifold. Broken hose?). Help!! (Again!!)