Hi all. Posting this as a follow up to a previous post as I have managed to successfully fit a vacuum actuated dump valve (BOV) to my 2.3 Mk4 Focus ST, and I want to share my experience with others as for me it was difficult to find any info on this modification. Hoping this will be helpful. Link to my original question.
The motivation for fitting one of these valves was obviously the sound aesthetic, then reliability, and more direct control from intake manifold pressure as I plan to increase boost pressure maps in the near future.
I was actually told before that this would not work, as the car relies on an electrically actuated diverter valve (DV), and tampering with that could throw up all sorts of warning lights and trigger limp mode and so on. But in spite of that, I assessed the overall risk as low and went ahead as an experiment. And what I’ve discovered is that the intake system is actually very forgiving. Ahead of the charge pipe, there are no sensors which I could see that meter air pressure other than the MAP sensor on the front of the intake manifold, which is good news for this mod - as it will change the airflow dynamics - but on the flip side reduces diagnostic coverage for boost leaks.
To summarize before I get into the details: I have the valve attached to the outlet of the original tap where the DV solenoid mounts to. This is located on the charge pipe beneath the intake pipe behind the engine block. The DV solenoid has been screwed off, and a TurboSmart blanking plate was attached to the top to seal it. It has been left connected (for now) and is zip tied tightly to the replacement valve with the DV left free to operate as normal to avoid any check engine lights. To operate the valve, a boost tap for the previous gen RS was used and slides snugly beneath the original MAP sensor. A (outrageously) long vacuum hose routes the manifold air signal to the back of the valve.
The valve I am using here is the HKS SSQV4 Black Edition with the high frequency fins. Below is a BOM list of what you’ll need for this mod;
Materials;
Tools;
1. First disconnect the battery. Always isolate the battery before attempting to work in the engine bay. Use a 10mm hex socket to remove the bolt first from the negative lead. Disconnect the sensor connector to the side of it but pushing firmly on the tab, slide the lead off the terminal, and push it behind the battery out of the way. Do the same for the positive lead, and wedge the red cap between the terminal and the lead as an additional precaution.
2. Remove the engine cover. Should be an 8mm hex bolt that will take a bit to unscrew. The other side is secured by a ball socket and just needs a firm tug to remove.
3. Remove the intake. If it helps, there are many aftermarket intake kits available for this car which have nice pictorial instructions for these next steps. I recommend using the one from Direnza. First start with the mounts for the air box. These should just pop out from their grommets with a bit of vertical force. There should be two trim clips either side of the front air scoop. Use the trim tools to gently remove these, they should come off in two parts. Don’t bother trying to separate the air box from the air scoop, it’s too difficult for now. You’ll have to remove it all as one part.
4. Now carefully remove the intake temperature sensor just behind the air box. You should be able to rotate this anti-clockwise to remove. Disconnect from the connector at the back by pushing firmly on the clip and pulling, and set aside in a safe place.
5. Disconnect the crank case breather from the top of the intake pipe. Should be a blue clip, gently pull this away from the pipe and pull to disconnect.
6. You are going to absolutely despise this step. At the back of the top pipe section is the recirculation pipe. It is held in place by ******* spring clips. You will need to apply a great deal of pressure on the two “fins” to squeeze it open, and at the same time gradually slide it down the recirc pipe to a point where you can shimmy it off the intake port. Be patient with this - you will be replacing these with the jubilee clips later, as they are ****ing awful to work with.
7. With the recirc pipe disconnected you should be able to remove some parts of the intake system already. There might be special OEM jubilee clips holding these parts together. Just loosen these with a flat head screwdriver and rotate anti-clockwise to release them.
8. At this point you should just be left with the intake turbo elbow exposed, and will have a nice view of the charge pipe and factory DV solenoid. Take the other ******* spring clamp off the recirc pipe and remove this completely. This is going to take quite a bit of force, as it is really held on tight to the recirculation port which is threaded for extra grip. Set this aside in a safe place and burn the spring clamps (I’m kidding).
9. We’ll move to the front of the engine now. The MAP sensor should be visible on the front of the intake manifold as a little square box looking thing. It should be easy to see now with the air scoop gone. With a T30 Torx bit, carefully unscrew the Torx bolt securing it to the manifold. It might be a bit stiff at first (bear in mind this part gets really hot during normal use). Set the bolt safely aside and carefully pull the MAP sensor free from the intake manifold.
10. The Forge boost tap for the Mk3 RS is ready to install now. It’ll come with its own fitting instructions. Lubricate the little O-ring on the tap with a bit of silicone spray and slide it in gently to the MAP port. Orient the boost tap upwards and, using the hex screw supplied with the kit, align the hole with the tapped hole in the intake manifold and secure this.
11. Slide the factory MAP sensor into the hole in front of the boost tap, and using the factory T30 Torx screw, secure this to the new boost tap. Be careful here - I found that the screw is not a perfect fit, so, do not over tighten this. Only go far enough that it feels secure.
12. Back to the DV solenoid behind the block. Gently undo the 3 6mm E-Torx bolts from the solenoid and set these aside in a safe place. Remove the DV solenoid and set this on top of the engine for now, being extremely careful not to put too much tension on the wires on the back. If it helps, remove the solenoid connector entirely, but in my experience it isn’t necessary.
13. Install the TurboSmart blanking plate to where the factory solenoid would have sat and secure it with the 3 factory 6mm E-Torx bolts. You may need to rotate it around a few times - the hole positions on the mount aren’t symmetrical. In my case only 2 of the 3 screw holes ever did line up, but the O-ring fits snugly on the inside.
14. Take your 90 degree 25mm silicone hose and first measure the length of one side against the threaded DV port. Measure how much you can trim. You want the ends to be as short as possible whilst maximizing contact with the port. Do the same with the flange port. For me I was using a hose with a 100mm leg length and found I could trim 30mm from the charge pipe end and 20mm from the flange end. Cut this to size with a razor blade (be extremely careful not to slice yourself).
15. Now slide the hose onto the DV port and secure using a jubilee clip. Make sure that the hose is rotated so that the open end is facing the firewall.
16. With your new vacuum valve, secure this to the flange mount. Specifically for the SSQV4, place the O-ring against the top of the flange, rotate the circlip around the bottom of the valve, and using circlip pliers squeeze the clip and push the valve into the flange. Make sure that the circlip is properly seated. Give the valve a good tug from the flange to confirm that it is secure, and inspect for uniformity on the circlip. This is important - this part will be under a lot of sustained pressure.
17. Slide the port of the flange onto the open end of the 90 degree silicone elbow and secure tightly with a jubilee clip. Angle this towards the firewall - there will be enough space for it there.
18. With the factory DV solenoid still connected, zip tie the mechanism tightly to the new dump valve pipe, keeping the solenoid actuator free to move in and out, so that the ECU will still see it connected.
19. Now you will need to attach the 4mm vacuum hose supplied with the Forge boost tap. Unravel this out and attach one end to the vacuum tap at the front of the engine. Then feed it around the side and use some zip ties to hold it in place, taking care not to attach it against any hot components. Then cut it to length with a razor blade, making sure not to cut it too short. Give it a bit of slack. Take the little end cap off the back of the SSQV4 (or whatever vacuum valve you’re using) and slip the hose onto the vacuum port. For additional security, secure the two ends of the hose with zip ties.
20. Plug up the open port of the intake manifold where the recirc pipe would have been connected with the 25mm silicone blanking plug, and reassemble the intake system including the air scoop.
21. Reattach the crank case breather and temperature sensor. Give one last visual check, make sure everything is tightened up and secure, make sure you haven’t missed anything.
22. Refit the engine cover.
23. Now reconnect the battery and give the engine a full power cycle to remove the under-voltage errors from the ECU.
This is what it should look like in the end;
![Image]()
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![Image]()
You should be good to test this on the road now! One word of caution - go easy on it first. Always have your oil up to temperature before building boost. Test it under light load at first before giving it full pressure. If things are not tightened or seated properly it is possible things will blow apart under pressure. But curiously, this will not throw a check engine light. If that happens, just go back to base, inspect what came off, and refit and retighten. In my first pull I blew the dump valve right off the flange because the circlip wasn’t seated properly. Contrary to how this sounds, it’s not a massive problem - this is just a small risk with DIY mods.
Anyways, guys, please let me know if you have any feedback or concerns with this modification. If this helps you, also let me know
I’m very happy with this mod. It’s made a real impact on how my car sounds, gave it more presence on the road, and holds the same boost pressure as it did before.
The motivation for fitting one of these valves was obviously the sound aesthetic, then reliability, and more direct control from intake manifold pressure as I plan to increase boost pressure maps in the near future.
I was actually told before that this would not work, as the car relies on an electrically actuated diverter valve (DV), and tampering with that could throw up all sorts of warning lights and trigger limp mode and so on. But in spite of that, I assessed the overall risk as low and went ahead as an experiment. And what I’ve discovered is that the intake system is actually very forgiving. Ahead of the charge pipe, there are no sensors which I could see that meter air pressure other than the MAP sensor on the front of the intake manifold, which is good news for this mod - as it will change the airflow dynamics - but on the flip side reduces diagnostic coverage for boost leaks.
To summarize before I get into the details: I have the valve attached to the outlet of the original tap where the DV solenoid mounts to. This is located on the charge pipe beneath the intake pipe behind the engine block. The DV solenoid has been screwed off, and a TurboSmart blanking plate was attached to the top to seal it. It has been left connected (for now) and is zip tied tightly to the replacement valve with the DV left free to operate as normal to avoid any check engine lights. To operate the valve, a boost tap for the previous gen RS was used and slides snugly beneath the original MAP sensor. A (outrageously) long vacuum hose routes the manifold air signal to the back of the valve.
The valve I am using here is the HKS SSQV4 Black Edition with the high frequency fins. Below is a BOM list of what you’ll need for this mod;
Materials;
- Forge Motorsport boost gauge fitting for the Mk3 Focus RS (comes with a generous amount of 4mm vacuum hose).
- TurboSmart blanking plate for the 2.3 EcoBoost (I picked up one for the 1.0 as these are stupid expensive, same size, fits 2 out of 3 screw holes but seals just as well).
- 90 degree 25mm (1”) silicone hose elbow.
- 2x jubilee clips to secure the 25mm hose.
- 25mm ID silicone blanking cap for the factory recirc port.
- HKS SSQV4 (or similar vacuum actuated valve).
- Flange for your chosen valve with 25mm OD port.
Tools;
- Ratchet.
- 10mm hex socket.
- 8mm hex socket.
- 4mm hex driver.
- T30 Torx driver.
- Flat-head screwdriver.
- 6mm E Torx socket.
- Trim removal tools.
- Spring clip tool.
- Circlip tool (if using the HKS valve).
- Blades for cutting the hose.
1. First disconnect the battery. Always isolate the battery before attempting to work in the engine bay. Use a 10mm hex socket to remove the bolt first from the negative lead. Disconnect the sensor connector to the side of it but pushing firmly on the tab, slide the lead off the terminal, and push it behind the battery out of the way. Do the same for the positive lead, and wedge the red cap between the terminal and the lead as an additional precaution.
2. Remove the engine cover. Should be an 8mm hex bolt that will take a bit to unscrew. The other side is secured by a ball socket and just needs a firm tug to remove.
3. Remove the intake. If it helps, there are many aftermarket intake kits available for this car which have nice pictorial instructions for these next steps. I recommend using the one from Direnza. First start with the mounts for the air box. These should just pop out from their grommets with a bit of vertical force. There should be two trim clips either side of the front air scoop. Use the trim tools to gently remove these, they should come off in two parts. Don’t bother trying to separate the air box from the air scoop, it’s too difficult for now. You’ll have to remove it all as one part.
4. Now carefully remove the intake temperature sensor just behind the air box. You should be able to rotate this anti-clockwise to remove. Disconnect from the connector at the back by pushing firmly on the clip and pulling, and set aside in a safe place.
5. Disconnect the crank case breather from the top of the intake pipe. Should be a blue clip, gently pull this away from the pipe and pull to disconnect.
6. You are going to absolutely despise this step. At the back of the top pipe section is the recirculation pipe. It is held in place by ******* spring clips. You will need to apply a great deal of pressure on the two “fins” to squeeze it open, and at the same time gradually slide it down the recirc pipe to a point where you can shimmy it off the intake port. Be patient with this - you will be replacing these with the jubilee clips later, as they are ****ing awful to work with.
7. With the recirc pipe disconnected you should be able to remove some parts of the intake system already. There might be special OEM jubilee clips holding these parts together. Just loosen these with a flat head screwdriver and rotate anti-clockwise to release them.
8. At this point you should just be left with the intake turbo elbow exposed, and will have a nice view of the charge pipe and factory DV solenoid. Take the other ******* spring clamp off the recirc pipe and remove this completely. This is going to take quite a bit of force, as it is really held on tight to the recirculation port which is threaded for extra grip. Set this aside in a safe place and burn the spring clamps (I’m kidding).
9. We’ll move to the front of the engine now. The MAP sensor should be visible on the front of the intake manifold as a little square box looking thing. It should be easy to see now with the air scoop gone. With a T30 Torx bit, carefully unscrew the Torx bolt securing it to the manifold. It might be a bit stiff at first (bear in mind this part gets really hot during normal use). Set the bolt safely aside and carefully pull the MAP sensor free from the intake manifold.
10. The Forge boost tap for the Mk3 RS is ready to install now. It’ll come with its own fitting instructions. Lubricate the little O-ring on the tap with a bit of silicone spray and slide it in gently to the MAP port. Orient the boost tap upwards and, using the hex screw supplied with the kit, align the hole with the tapped hole in the intake manifold and secure this.
11. Slide the factory MAP sensor into the hole in front of the boost tap, and using the factory T30 Torx screw, secure this to the new boost tap. Be careful here - I found that the screw is not a perfect fit, so, do not over tighten this. Only go far enough that it feels secure.
12. Back to the DV solenoid behind the block. Gently undo the 3 6mm E-Torx bolts from the solenoid and set these aside in a safe place. Remove the DV solenoid and set this on top of the engine for now, being extremely careful not to put too much tension on the wires on the back. If it helps, remove the solenoid connector entirely, but in my experience it isn’t necessary.
13. Install the TurboSmart blanking plate to where the factory solenoid would have sat and secure it with the 3 factory 6mm E-Torx bolts. You may need to rotate it around a few times - the hole positions on the mount aren’t symmetrical. In my case only 2 of the 3 screw holes ever did line up, but the O-ring fits snugly on the inside.
14. Take your 90 degree 25mm silicone hose and first measure the length of one side against the threaded DV port. Measure how much you can trim. You want the ends to be as short as possible whilst maximizing contact with the port. Do the same with the flange port. For me I was using a hose with a 100mm leg length and found I could trim 30mm from the charge pipe end and 20mm from the flange end. Cut this to size with a razor blade (be extremely careful not to slice yourself).
15. Now slide the hose onto the DV port and secure using a jubilee clip. Make sure that the hose is rotated so that the open end is facing the firewall.
16. With your new vacuum valve, secure this to the flange mount. Specifically for the SSQV4, place the O-ring against the top of the flange, rotate the circlip around the bottom of the valve, and using circlip pliers squeeze the clip and push the valve into the flange. Make sure that the circlip is properly seated. Give the valve a good tug from the flange to confirm that it is secure, and inspect for uniformity on the circlip. This is important - this part will be under a lot of sustained pressure.
17. Slide the port of the flange onto the open end of the 90 degree silicone elbow and secure tightly with a jubilee clip. Angle this towards the firewall - there will be enough space for it there.
18. With the factory DV solenoid still connected, zip tie the mechanism tightly to the new dump valve pipe, keeping the solenoid actuator free to move in and out, so that the ECU will still see it connected.
19. Now you will need to attach the 4mm vacuum hose supplied with the Forge boost tap. Unravel this out and attach one end to the vacuum tap at the front of the engine. Then feed it around the side and use some zip ties to hold it in place, taking care not to attach it against any hot components. Then cut it to length with a razor blade, making sure not to cut it too short. Give it a bit of slack. Take the little end cap off the back of the SSQV4 (or whatever vacuum valve you’re using) and slip the hose onto the vacuum port. For additional security, secure the two ends of the hose with zip ties.
20. Plug up the open port of the intake manifold where the recirc pipe would have been connected with the 25mm silicone blanking plug, and reassemble the intake system including the air scoop.
21. Reattach the crank case breather and temperature sensor. Give one last visual check, make sure everything is tightened up and secure, make sure you haven’t missed anything.
22. Refit the engine cover.
23. Now reconnect the battery and give the engine a full power cycle to remove the under-voltage errors from the ECU.
This is what it should look like in the end;
You should be good to test this on the road now! One word of caution - go easy on it first. Always have your oil up to temperature before building boost. Test it under light load at first before giving it full pressure. If things are not tightened or seated properly it is possible things will blow apart under pressure. But curiously, this will not throw a check engine light. If that happens, just go back to base, inspect what came off, and refit and retighten. In my first pull I blew the dump valve right off the flange because the circlip wasn’t seated properly. Contrary to how this sounds, it’s not a massive problem - this is just a small risk with DIY mods.
Anyways, guys, please let me know if you have any feedback or concerns with this modification. If this helps you, also let me know
I’m very happy with this mod. It’s made a real impact on how my car sounds, gave it more presence on the road, and holds the same boost pressure as it did before.
