675.cc • Triumph 675 Forum

BikeTuna's winter turbo build

Discussion in 'Images & Videos' started by Biketuna, Nov 12, 2015.

  1. Tease ... Is it a weapon?!
  2. StMarks

    StMarks PTG

    Location: HU15 2DS
    Absolutely no reason to feel ashamed mate, I think I'm speaking for pretty much all of us when I point out that we were all very impressed by your ingenuity & determination despite all the setbacks you encountered.
    Frankly we've been missing your updates.
    • Agree Agree x 2
  3. D675hogg


    Location: Glasgow
    Second that. Great commitment to such an out of the box idea. Well impressed!!!
  4. Biketuna


    Thread Starter

    Location: oxfordshire
    It was a monumental failure and I was shameful of it. I stretched myself financially and technically and all I got was 2 years without a bike and an unrideable mess.

    But it was a steep learning curve, and I learned if many things that I would have done differently with hindsight...

    So I did. This is almost an all new build. A genuine Garrett GT25 is on an all new manifold, custom boost pipe, fully plumbed into the cooling system and running a manual boost controller. Its much more serious than the first one.

    Its just gone back together, and it's had 2 road rides since MOT. It's currently running a measily 3psi while I fiddle with the oil setup, but once that's sorted it's off to the dyno once again.
    • Like Like x 1
  5. Biketuna


    Thread Starter

    Location: oxfordshire
    ... And yes, it's an absolute weapon!
    • Winner Winner x 1
  6. Captain Steffydog

    Captain Steffydog Moderator Staff Member

    Location: East London/Essex
    Well done mate, honestly, give yourself a pat on the back for effort, ingenuity and gusto.
  7. Cracking build, I want one!
  8. farmer1


    Location: oxford
    So pleased to hear you've got her back up and running.
    I salute you for all the hard work and perseverance.
    Are you still in Oxfordshire?
    Give me a shout if you ever head up to h cafe, I'd love to have a look/listen.
  9. Stu675


    Location: Gu1
    Awesome mate awesome

    When’s a ride out?
  10. cpszx


    Location: Chatteris
    Absolutely no need to be ashamed of it. No need at all.
    You started something that you had no knowledge of, learnt everything along the way, applied some great ideas, and gained valuable experience. You stretched yourself technically and gained massively from it.

    The ambition to build things yourself, and the steep learning curve when you encountered have only done you good.

    The financial stretch caused you problems with budget used parts. But in most cases you were just unlucky with them, that's all.
    It was still a good idea, and would have worked if you had had a bit more good luck than bad.

    The unfortunate part is that you had 2 years without a bike. That is all.

    A measly 3psi is still positive pressure, increased performance, and a massive grin factor that you have made it!
    • Agree Agree x 1
  11. TripleJimmy

    TripleJimmy Moderator Staff Member

    Location: Dover
    I saw you post on FB and was looking forward to an update. Well done for pushing through and it's definitely something to be proud off. If things come to easy you don't appreciate them, nice work.
  12. Biketuna


    Thread Starter

    Location: oxfordshire
    I'll try and bring you all up to speed, I'll type it here and then edit it on my phone to add the pics, so if you don't see them they will be ehre in a tick.

    The reason the first build failed so badly on the dyno was that the GT15 turbo could not flow the exhaust gases fast enough over 8krpm. The only solution was to fit a bigger turbo. The recommendation was a GT2560 hybrid but it was out of budget, so the next best thing was the GT25. It'll be big enough to flow the gases, just slightly laggier than the 2560 as it has a slower spool up time. The search begins, finding a few cars running the GT25, a mix of escort cossie small turbos, Nissan 200s and the reliable beast that is the Saab 9000T.

    I find a Saab turbo, low mileage from a breaker and the pics of the car show body damage, which implies its a good running unit. It arrives and its massive. Much bigger than the GT15 and clearance is tight!


    The manifold is taken off, cut as short as possible to raise the height and a new flange is fabbed and welded on (same process as last time).


    The turbo has had to be mounted the other way round to the GT15 due to the shape of the compressor housing and the coolant connections, but now everything is backwards, and clearance dictates the charge pipe goes under the turbo and up the same side as it used to. The pipe diameter has been reduced to keep the volume down and try and recude lag, and the whole thing is welded to minimise pressure loss from multiple joins and powdercoated to keep it hidden.


    The big problem ive had for the whole build has been oil flow. it now runs a catch tank underneath and the fuel pump from the last system runs constant. The coolant line from the bottom of the rad has been interrupted to go via the turbo, and all the pipes are insulated from the exhaust.


    Everything else remains the same - the airbox, ecu, fuel pump and reg, and overall it's a much more comprehensive and technical build. I have added a manual boost gauge (that red thing just above) as the wastegate that's on there is pretty weak, and I don't want to depend on it.

    The fairings have been refitted, with major modification. The boost pipe wasn't close enough in to be able to go behind the panel so it's cut for access and because the panels were cut for the other system it's now all a bit gappy, but while it's all in progress i'll leave as is.
    Last edited: Sep 3, 2018
    • Like Like x 1
  13. Biketuna


    Thread Starter

    Location: oxfordshire
    I took it to MOT so I could start some road testing, and towed it there for safety. I finally got a towball on the back of my own car so I don't need to keep borrowing cars, but I think my setup got more looks than the bike!


    It passed the MOT with the addition of rear indicators and a bumper plate light which I bought fron the MOT station and fitted there and then while we had a cup of tea (I like garages like that - Sheps in horspath if you are in Oxfordshire, mine goes nowhere else).


    Ive started doing some road testing, its been off the road for 2 years now and its been apart a lot so it needed a good shakedown. Oil is again the issue, it can comfortably boost over 8k, and 3psi is as high as I've had it so far, but while the airflow faults are all sorted by the bigger turbo, the oil issues are coming back to bite me. The oil started filling the catch tank overflow header over 8k (and overspilled down my leg), so I need to decide wether to restrict the oil rate into the turbo or up the pump somehow, but I think at least for the short term I'm going to feed the overflow pipe back into the engine so it runs fine from the pump on regular riding and just overflows and dumps it back in when on full chat.

    The bike is insane! Winding the throttle back and hearing the turbo whistle up is even more intoxicating as the original bikes whine. Despite the phenomenally loud exhaust the whistle stands out by a long way. The feel of the boost coming on isn't instantaneous, but it's very progressive, and quite predictable. It feeds in and swells into power at around 6k very much like a inline 4 picks up around there, but with the power of a much bigger bike. Fast gearchanges give the atmospheric dump valve its split second of spotlight with a lovely but not overloud whoosh of air before the spool winds up again.

    Either an evening this week or next weekend the bike is coming apart again. The panels will be off and the oil spillages cleaned up, then work out an oil return setup before getting back out, to start pushing over the 8krpm and see what the thing really does.

    Short of pistons melting, I'll be at fest next year.
    Last edited: Sep 3, 2018
    • Like Like x 7
  14. Wow mate what a story. I'm so pleased for you that you've managed to get to this point with your build. And what a machine you have created. Massive well done
  15. Good on yer for sticking with it, just remember
    I have not failed. I've just found 10,000 ways that won't work. (Thomas Edison)
    I used to work at Garrett Turbochargers as a maintenance engineer until they closed us down and moved somewhere cheaper abroad:mad:, a really interesting job for a petrolhead who was in the middle of his scooby phase:D.
    I remember the guys in the workshop used to do a few hybrid specials as foreigners, also remember having to smash up hundreds of perfectly good Turbo's (possibly T25's) as requested by Fords for some reason, it had to be videoed but i'm sure some "escaped" along the way.:p

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