How to install a blow-off valve (BOV)



Please note that I am not a mechanic by trade and that I nor can be held responsible for any damage, injuries or death caused by work you perform using this website as a guideline.

To install a blow-off valve on a ST185 using the stock top mounted intercooler (TMIC) there are two ways of mounting it:

1) Use a T-hose between the turbo and intercooler
2) Weld a flange on the intercooler itself

This guide is about the first option and based on an HKS Super Sequential Valve (SSQV).

Parts and tools needed

Samco T-hose, 51 mm (Samco part number STP51)
Universal 1" (25 mm) SSQV adapter/flange
2 Hose clamps to clamp 60 mm outer diameter (OD)
Hose clamp to clamp 34 mm OD
Vacuum hoses in 8 mm and 4 mm inner diameter (ID)

Basic socket set
Sharp knife
(Sour-free) Vaseline


Fit the bov on the flange using the O-ring and C-clip which come with the SSQV. There are special pliers for this, but they aren't necessary. If you can't get the clip on, try getting the outer shield off the SSQV by removing four out of the eight Allen screws on the front. See the HKS manual to find out which four.


The TMIC is bolted to brackets on the engine. When standing in front of the car, there are two bolts on the right side of the TMIC and one on the left. Remove them. Remove the hose clamps on the throttle body rubber and hose between turbo and intercooler. Pull the front of the TMIC up so it pops out of the hose on the turbo.

In case of an air-to-air (ATA) intercooled ST185: Remove the intercooler for easy access.
In case of an water-to-air (WTA) intercooled car: Tilt the intercooler to the side for access.

You might also want to clean the intercooler while you're at it, it only takes a few minutes and some petrol.

Remove the original hose between turbo and intercooler:

Cut the T-hose hose to length so it'll fit between the turbo and TMIC: Hold the hose with the big hose clamps on it next to the turbo, mark how much you need to cut off (it's probably be too long). Put some Vaseline on the turbo and intercooler to help you put the intercooler back on with the T-hose.

Put the three bolts back in to clamp the TMIC onto the engine and put the BOV on its flange on the T-hose. Tighten all hose clamps. Connect the vacuum line between the SSQV and engine. There are several points for this, for instance:

1) 8mm nipple on the side of the intake manifold. Use the HKS adapter to change the hose ID from 8 to 4 mm to fit the SSQV nipple.
2) 8mm nipple on the back of the intake manifold. Use the HKS 8 to 4mm adapter.

Secure the vacuum lines with zip-ties. Make sure all hose clamps are tightened again.

Job done!

Related links

HKS SSQV blow-off valve
How to..
How to clean the intercooler