Project Volvo C70 Projects

Volvo Bov (blow off valve) Install

Some Say Not To Do It But I Did The Volvo BOV Install In The Project C70

When I first got the C70 I had plans on putting a BOV in the thing because I wanted that cool pshhh sound but after reading several forum posts on Swedespeed and Volvospeed I decided to ignore it at the time. Mostly because I was also focusing on the Probe project but since I started to mod the 70, I figured I would look more into it.

After a lot of research I found that several people have issues with their Volvos stalling because they are MAF metered cars. The car is taking into account of how much air is flowing in and adding the correct amount of fuel however when you install a vent to atmosphere blow off valve, that air gets discharged into the air instead of back into the intake tract. This creates a rich condition for a quick second, which in some cases, stalls the car.

I found a write up from someone on Swedespeed and he said how he installed a blow off valve in his volvo in conjunction with the car’s stock compressor bypass valve, which is the stock blow off valve. So I decided to give it a chance. Here’s the link with the write up-> “Finally Did The BOV Mod!”

I found an HKS blow off valve after reading and listening to the different sounding ones out there. I came to the conclusion that the HKS one was the best sounding and overall better design of my favorites. The other I had in mind was the Greddy.

The HKS blow off valve install wasn’t as bad as I thought it would be but the snap rings that secure the bov to the piping is annoying and can be pretty tricky to get on. I got mine on after buying some snap ring pliers at Home Depot for about $11.

Next I tee’d a vacuum line off of the stock CBV vac line and connected it to the HKS bov. Started the car up and tested it out. It sounded very nice and gave me that sound I was looking for. After driving around with the bov installed for about a day I ended up stalling twice. I found out that it was when I would go full throttle and let off the gas to hear it and coast to a stop, that it would stall. I was about ready to take it out but then I read some interesting information about the HKS.

I read that you can adjust the spring tension on the back of the bov. I tried it out and loosened it up a few turns. Drove it around for a few days and it didn’t stall at all. It was working perfect, however my idle was a little off. So I decided to adjust it again and it stopped stalling on me and has a good idle.

In the process of the install I put some new aluminum intercooler piping on where the bov goes and so far it’s worked out pretty good. It looks good in my engine bay and sounds awesome.

One thing I did notice about the bov is that there is a significantly less amount of turbo lag. This was one of the other main reasons why I wanted to install a bov.

I bought a blanking plate to put on the turbo for the install but after I came across the write up of how to install it with the stock cbv installed I decided against installing it. I figure I would just wait until I get my new turbo upgrade and tune so I can get the car tuned for a bov.

In the end I am happy with the install and it was pretty quick and easy. Anyone can do it in a few minutes. It just took a few drives and some fine tuning to the bov to get the car running great. Here’s a video of the bov installed in the car and the sounds. Also some pics of the process. I installed it on the pipe that goes to the turbo from the intercooler but will be moving it to the throttle body intercooler pipe once I get the new plate from Snabb that can be welded onto the intercooler piping. It was either that or pay about $400 for the reverse intercooler piping kit. The way I am doing my own custom kit, I am saving about $200+ so it’s okay for me to wait.

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