CBV or not CBV? - Pre Tune.

[jellison]

Volvo do not sell the CBV springs and neither do they sell the CBV on there own, you'd need to buy a whole turbo!

Also, I don't believe the CBV springs shown on the Viva website are intended for use with a stock diaphragm. They are intended for use with cars running much higher boost than stock and alloy CBV.

The CBV is intended as an upgrade over the stock CBV with a rubber diagphragm as it is common that the diagphragm degrades over time, being rubber they can crack.

Therefore, if you just replace the CBV with an alloy type and your car is totally stock, then it's adviseable to use the green spring as this has the same rating as the stock spring.

If your car is heavily modded, tuned mapped and running higher than stock boost, then obviously, you'd need to switch to an aftermarket CBV with a stronger spring as you don't want that extra boost leeching away because the stock or green spring cannot hold the valve closed.

My car is mapped peak boost @ peak torque around 21psi and I run a yellow spring on a Forge CBV.

This is the valve with yellow spring spring that I have fitted to my car. As you can see, you'll save a fortune on import costs over the Viva version!

https://www.forgemotorsport.co.uk/Di...uct--1006.html

So if I had a similar tune to what I had on my T5 I could leave as is (the stock CBV and spring).

The boost is via the mapping right? The spring is to control the pressure on lift off to stop the Turbo being harmed?

Did find a video of changing the spring in the std CBV (looks fiddly and probably something (if required I'd get someone that is very familiar with to do).

I presume my old T5 would have had a lot more most to be 60odd bhp up on std. The tune would give more boost (how else would the power go up?). If I was looking to get a similar rise from the R to the T5 50-60bhp (including the benefit of the catback), std CBV or std CBV but with a fresh (as you are in there - presume this is just an OEM part) and yellow spring?

I'm a lot better with NA race engines....

[LeeT5]

So if I had a similar tune to what I had on my T5 I could leave as is (the stock CBV and spring).

The boost is via the mapping right? The spring is to control the pressure on lift off to stop the Turbo being harmed?

Did find a video of changing the spring in the std CBV (looks fiddly and probably something (if required I'd get someone that is very familiar with to do).

I presume my old T5 would have had a lot more most to be 60odd bhp up on std. The tune would give more boost (how else would the power go up?). If I was looking to get a similar rise from the R to the T5 50-60bhp (including the benefit of the catback), std CBV or std CBV but with a fresh (as you are in there - presume this is just an OEM part) and yellow spring?

I'm a lot better with NA race engines....

Kind of. Boost follows Torque on V70R/S60R. Torque is governed by many things including throttle position, air temp, intake air temp, Engine load, knock control etc

You really need to do a lot of reading up on how Turbo chargers work and the corrolation between wastegate and CBV before you make your decision.

If your car is anything other than stock, then my advise is to upgrade the CBV.