do's and dont's for fitting external wastegates

Thread in 'Technical Questions' started by yogi bear, Aug 3, 2010.

  1. yogi bear

    yogi bear Active Member

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    what are they? I mean, any tips on where to put them and where not to put them, and how far from the manifold they should be? and what grade stainles pipe should i be using too?
     
    #1 yogi bear, Aug 3, 2010
    Last edited: Aug 3, 2010
  2. croustibat

    croustibat Member

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    They are wastegates. they do the same job as internal wastegates, and are used to control boost. Depending on the flow used you might want a bigger or smaller one. It allows screamer pipes (which are useless anyway). It also allows to use turbos that comes without internal wastegate, or when this wastegaste is too small (which means boost creep, seems to happen on holsets).

    Obviously, the nearer from the turbo the better, but i guess there are heat issues. The exit should be plumbed back in the downpipe, far from the elbow so it does not disturb the flow.

    Why would you want one ?
     
  3. GKD

    GKD Member

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    Why would u want an external wastegate....well There's a reason that any turbocharged race car uses external gates, because they are far superior to an internal gate, flow, torque and power are increased due to less turbulation around the turbine wheel exit and wastegate valve, and as for screamer pipes being useless....u should do ur homework before giving advce on something u obviously knw nothing about. There is a reason for venting the wastegate to atmosphere, it's easier to release prssure to atmosphere than venting back into the exhaust downpipe.....due too exhaust pressure......obviously..... Resulting in a more controlled boost curve. If ur gonna plumb the wastegate exit back into the system then over 18" is recommended. 304 stainless is fine for exhaust systems, as well as a few others.
     
  4. topi

    topi KlutchKickKidz

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    Do put them on car.
    Don't have sex with them.
     
  5. yogi bear

    yogi bear Active Member

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    i was not paying much attention to the first post. i know exactly what they are and how they work, was merely looking for any technical as to where to fit them. or where not to fit them.
    Its def not gong to dump back into the exhaust, it gonna be vent to atmos.

    do you think 304 1.5mm is thick enough to fab a screamer from?

    any idea hoe far away from the manifold i can fit it before it stars becoming a problem?

    i can the logic in that:smash::smash: lol
     
  6. croustibat

    croustibat Member

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    Dumbest reason to fit something is "because race cars have it".

    Did you fit the 38mm intake throttle to your car too ? Because WRC cars have them. :wave:

    screamer pipes will also get you raped by policemen, hated by your neighbours, and eventually banned from tracks. What a nice item to use.

    Also, dumping in the exhaust is BETTER than dumping to atmo, as gas flow tends to create a vacuum in the wastegate plumbing :nod: That goes for the obviousness.

    All the talk about "not disturbing the flow at the exhaust turbine" is true, but what is the *real* difference in performance between a "disturbed" and a "non disturbed" ? I cant see it.

    The reason why old race engine uses external wastegate is because internal wastegate did not exist back then, or were fragile.
    Same thing is currently happening with dump/recirculating valves, they get integrated in turbos nowadays, and i think they will perform the same if not better than any "external dump/recirculating" one.

    So, yes, in theory an external wastegate *should* be better. In reality, it just adds 10kg of tubing to your engine bay and nothing more, unless you use a crappy ebay turbo with flawed designs.

    Hence my question which was directed to yogi bear : "why would you want one?"
     
  7. RyanH

    RyanH Lacks skills

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    Only if you're on full boost outside your house, surely? :wack:

    Proper screamer pipes sound cool, but that's the only reason I know for having them. :D
     
  8. yogi bear

    yogi bear Active Member

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    if my wastegate is open and im near a policeman, im pretty sure to be getting a telling off regardless of wether i have an external or not. in the same sentence you could add that neither do i drive at 100mph down my road so im sure my neighbors will not mind.
    And lastly, i generally do not care if i upset people in this manner.

    not that it has anything to do with my first question but ill answer it so you can satisfy yourself. the reason behind now going for an external gate is clear.
    after alot of messing about, and alot of pulling my hair out(well what left of it), it is aparant that my turbo is not happy. its partly because i dont have a very intelligent boost controller that does not have rpm dependant boost.
    and partly because even if i did have one im concerned that the wastegate is and would still be getting blown open.

    I have a greddy t518z which is a td05 18g with a modded front housing. and as you mention yes, it doesnt seem to be a great design and the thus it struggles to control boost.

    sooooo, if you have any info that can help me fitting an external then please, let me know
     
  9. cptsideways

    cptsideways Active Member

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    Most bigger turbo's don't have internal gates, so you have to fit an external one, simple as that doh, vented atmospherically or not is up to you. They don't have to be loud, depends where you vent them.

    I guess you question is where should it live in the bay? where you can access it easily, it can be close to the manifold or a little downstream, the shorter the piping the better I'd guess, but you need to avoid heat as much as possible.

    [​IMG]

    [​IMG]

    [​IMG]
     
  10. Mr Bizzle

    Mr Bizzle In Safe Hands

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    Lots of bullshit as per usual.

    If you have two buckets full of water, then cut a 25mm hole in the bottom of one and a 50mm hole in the bottom of another. Which one will drain the water out fastest?

    A waste gate's job is to vent exhaust gas away from the exhaust wheel to control the rotational speed of the compressor. An internal gate is limited in size because it's located in the exhaust housing - depending on the size of the turbo they are usually 25-30mm max.

    Decent External waste gates are independent of the turbo, usually much larger (50-75mm) and can vent gas away from the turbo more accurately. In the same way you can run up rated actuators on internal gates, you can swap out the springs on external gates.

    A good external gate will always outperform good internal gate.

    Keeping the WG shut tight until you hit the desired boost pressure, means you spool quicker and produce a better spread of power.

    Atmospheric vs Exhaust venting makes such little difference that it's not even worth discussing.

    Your neighbours won't hear an external gate at idle or while your off boost, neither will the rozzers.
     
  11. GKD

    GKD Member

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    like i said they are superior in every way....power,flow , torque...."why wouldnt u want one......" and as for added weight....come on....a few kg's at the most dont u think....

    Im not saying fit it because race cars use them....im saying race cars want power and u wont find no internal gate on anything thats trying to get the most from the set up, internal gates are a compromise.... an accountants choice,not an engineers/designers.

    And no i dont have a 38mm inlet restrictior and i didnt say use one either because there arnt any power restrictions on road cars or drift cars......unlike WRC...:wave:...next

    Oh and does anyonre give a fuc about 1. the neighbours
    2. five-0
    3. tracks....its all about streeto...

    YOGI- my first post wasnt aimed bad at u mate.....i think someones a little bitter they dont have an external, maybe it was on the christmas list but no one got him one:euge:
     
  12. GKD

    GKD Member

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    Bizzle- im sure keeping the extra volume of wastegate gasses out of
    the exhaust system will help, minimal like u say but still better or...?
    if not for flow then for the factor of the extra heat in the system.... it may be very little....but dont we all do all these little things here and there that all add up and give us the extra bit of power/torque we all are aiming for.....

    Yogi, if ur gonna plumb the wastegate exhaust back into the system dont forget to allow for theremal expansion with slip joints.
     
  13. Stavros

    Stavros Active Member

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    People massively underestimate the flow thru an external WG.

    Seen 450bhp cars drop almost 50bhp by plumbing back into the system.

    A car with a 3in system with no restriction and a screamer might need a 3.5in to be as good with it plumbed back in.

    IMO this is the biggest advantage of one, a seperate pipe for the WG means the pissy 3in off the shelf systems arent restrictive till much higher power. 3in is noticably restrictive with internal gate beyond about 450. But with a seperate WG pipe its higher.

    Dont have to have an unsilenced 'screamer' either, and they dont take much silencing. Ive driven a 605bhp cars with a single box seperate silencer off the wastegate and you couldnt even tell when the WG opened.
     
    • Funny Funny x 1
  14. GKD

    GKD Member

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    Thats what i thought...cheers stav
     
  15. sideways.taff

    sideways.taff - www.tafftune.com -

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    Who is this croustibat person? I've seen lots of 'technical' posts from him that are ever so slightly off key to what would be considered correct and it really is starting to do my head in now.
     
  16. Mr Bizzle

    Mr Bizzle In Safe Hands

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    Indeed.

    [​IMG]

    [​IMG]

    [​IMG]
     
  17. kieran_e1

    kieran_e1 In need of practice

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    he's just been booted off sxoc for being a troll and an argumentative frenchie hence why he's now dropped onto here.
     
  18. Stavros

    Stavros Active Member

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    Easy to get banned from SXOC just for not agreeing with their tuning 'ways', but simple fact with this dude, he is mostly wrong.
     
  19. GKD

    GKD Member

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    Ok....so now we figured out crustybats a bit of a dork....im with Clarkson here.....France: Level it...Mac it...drift it....:thumbs:
    yogi, theres a book by Corky Bell called Maximum boost, u can get it from amazon, well worth investing....it explains and shows how to build turbo systems, simple and complex information explained, troubleshooting, etc. u wont go wrong if u buil/ design ur system around the info in this book.
     
  20. Captain Muppet

    Captain Muppet Pro-tard

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    Holy crap - you advising someone to read a book? Actual knowledge, published and proof read and everything? Winner.

    Excellent advice, I can only add that this book and indeed all others are available free from your local library - just sign up and order it.

    Libraries are like google, but with significantly less bullshit.
     

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