225 Boost cut issue

Discussion in 'Mechanical - Engine, Gearbox, Exhaust etc' started by hepp997, Mar 28, 2018.

  1. Hi lads,

    Having some issues with my megged clio, wondered if anyone can help. If I'm in a high gear at low-ish revs (e.g. 2500) and I put my foot down, the turbo boosts up but then cuts out after a second or so. If I knock it down a gear and boot it, it seems fine. I've been checking the boost/vac pressure levels via OBD on the Torque app, it reckons I'm reaching 19psi with my foot flat to the floor in the higher gears? Not sure how accurate this is. At idle the vac pressure is about 21psi.

    There's no fault codes logged, only occasionally the EML because of the decat I believe. So far I have replaced:

    NGK plugs,
    4 coils (new bolt threads also),

    The car also has an uprated Walbro fuel pump. The injectors made it a little better, as it was a bit rough on idle. But made no difference to the boost cut problem. I'm now thinking I could have a faulty actuator? Any help/thoughts would be appreciated

  2. Chris79

    Chris79 RSM Club Member

    Possibly boost creep, Your actuator may not be holding the pressure correctly before opening. There's probably a built in ignition cut on Ecu to stop det or pre ignition if the mix is too lean. All being well and good, the car should be able to perform this task but can I ask why are you driving your car like this? You're unnecessarily over working the engine, asking it to produce large torque at low engine speeds and asking for internal failures.
  3. Can the actuator be tested somehow then? And easy to replace?

    The symptoms occur in normal day to day driving on the motorway; if I pull out to come round a lorry at 70mph in 6th gear, I'll get boost cut. Surely that isn't normal?
  4. I had this years ago when my 230 car was first mapped it was overboosting and cutting back when it was on the pull from lower revs but was fine when reving through the gears. Has it been mapped? Is there a dump valve fitted?
  5. Its not been mapped to my knowledge, I had a dump valve on but put it back to standard and it hasn't made any difference. What sorted it for you?
  6. Chris79

    Chris79 RSM Club Member

    Check your vac pipe to the actuator, if it’s damaged and bleeding air off, it will “fool” the actuator into not opening the wastegate at the correct pressure hence over boosting.
  7. Check the plastic pipe were the dump valve t piece would be to make sure the metal insert hasnt came out and is blocking the throttle body i also had this but it did put the car into limp mode until turned off and started again. I had a k&n 57i cone filter on at the time i took it off and paul at rs tuning adjusted the map and it never happened again.
  8. Vacuum tested the actuator today, and the arm didn't seem to move at all. it also wouldn't hold pressure properly. So I will replace this and see how I go. Will get the throttle body off too and check inside as I know when i got the engine that pipe had snapped off inside
  9. The actuator will only open at positive pressure not under vacuum. The actuator stays shut until the desired boost pressure is made and then it will open to allow the exhaust gasses to bypass the turbo
  10. Yeah I realised that after I'd done it lol, I put some positive pressure through it and it moved freely.

    Scratching my head a bit now, as the actuator seems fine, I've already swapped the N75 valve and I've cleaned and checked the throttle body which also seems fine. Whats the next steps?
  11. I’m not sure. Maybe a boost leak? Can you hear any strange noises on boost? I have a similar situation. I occasionally get this boost cut. Sometimes it won’t do it for weeks then it’ll do it three times in a week.

    I’ve replaced, sparks and injectors. And it still has happened once since. Mines weird thought it can do it at full boost which feels horrible. And sometimes I can just be cruising and power completely drops off for a few seconds and then it comes back again.
  12. Chris79

    Chris79 RSM Club Member

    Is it possible that the fuel pump could be on the way out? Thinking is, if the engine is not getting enough juice, the ecu realises this and cuts the ignition? Just a thought
  13. Fuel pumps failing these days is pretty rare. Guess its feasible.
  14. Chris79

    Chris79 RSM Club Member

    Not really, the one on my car was replaced just before I bought it due to failing
  15. Yeah I didn't say its impossible. I just said its not very common. How would you even test that?.
  16. I've got an uprated Walbro pump on my clio, it worked flawlessly on the old engine and is less than a year old so I can't see it being that. I think I'll check for boost leaks next, although surely it'd be under boosting rather than over boosting if its a leak?
  17. Chris79

    Chris79 RSM Club Member

    Is it not a common fault on these for the fuel pump to fail? Thought it was but maybe I’m wrong! I’m not up to scratch completely on these cars but using general knowledge gained over the years regarding fault finding. As for testing the fuel pump, not so sure. Maybe a pressure test of the fuel system or on a dyno?
    I have found on mine that there is a fuel leak where the fuel lines meet at a union on the underside of the car beneath the drivers door. It’s only slight on my car and doesn’t cause the problems that you’re experiencing but if it were worse it may cause fuelling problems. Maybe nothing in your case but also worth a look.
  18. Chris79

    Chris79 RSM Club Member

    Are these actuators pressure or vac operated? Do you have an adjustable actuator and is the lock nut set tight?
  19. They're pressure operated. i don't believe they are adjustable the stock ones, nut seems tight. I've a replacement one coming tomorrow so I'll swap it over and see what occurs
  20. Chris79

    Chris79 RSM Club Member

    If it’s got a threaded rod with a lock nut, it’s adjustable. You use this to adjust the base tension of the spring in the actuator to control boost. Again, not sure on what is std equipment on these but from past experience, the actuator arm is fixed length with no thread and locknut. Take a pic
  21. It has got a threaded rod, so I guess it must be. But does anyone know what the stock setting is?
  22. They are adjustable however I'm not really sure how you set them up correctly.
  23. So I think I've now solved this. I hadn't noticed a squeak from the engine bay on boost (only as I had the windows down) which led me to think it was a boost leak. I mocked a quick boost leak tester together and found a fairly big cut in one of the intercooler pipes, replaced it and it's got rid of the squeal and boost cut
    Mikey4410 likes this.
  24. Thatll be u sorted then dude! Well done
    hepp997 likes this.
  25. Well done I’m glad you found it. Can you hook up your boost leak tester to my car? Haha I could do with mine being tested.
  26. It's only a very basic tester, I've added a couple of pics so you can make your own. Once you've pumped up the system a bit, spray some soapy water over all the connections and any leaks should be obvious and start bubbling up
    IMG_9243.JPG IMG_9244.JPG
    Joe R26 likes this.
  27. Thanks man, I'll definately give it a go. :smile:

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