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Thread: twin turbo Vs Big single?

  1. #61
    RXWPN's Avatar

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    i mounted mine in the front so didnt have to modify much at all. way easier to service

    turbo in car.jpgTurbo Manifold 2.jpgturbo.jpg

  2. #62
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    @RXWPN
    Hi justin, what manifolds are you using for this setup. complete custom, modified originals or complete standard originals?

    i remember this thread you did. not much detail from the pipe on the exact pipework. i believe the exhaust manifold output ran under the car and joined at the front by the turbo and then the exhaust downpipe whet back under the car to the normal exhaust location.
    how is the tuning going on it did you reach your targets?
    am i right in thinking you converted you car to rear wheel drive only?

    Bye for Now!

  3. #63
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    Just using standard manifolds with pipes joining them up at the front. Made 265kw at the wheels at 18psi but ignition system couldn't cope with much more so in process of going coil on plug. Nope still 4 wheel drive and will keep it that way lol it rains way too much here.

  4. #64
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    Quote Originally Posted by RXWPN View Post
    Just using standard manifolds with pipes joining them up at the front. Made 265kw at the wheels at 18psi but ignition system couldn't cope with much more so in process of going coil on plug. Nope still 4 wheel drive and will keep it that way lol it rains way too much here.
    Did you open up the outlet holes in the stock manifolds at all they are very small. I was thinking it might help the exhaust flow. There is quite a lot of metal that could be removed to make the hole bigger.

    Sent from my MI 5s using Tapatalk

  5. #65
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    I'm in the process of building a new engine out of one of my spares that one will be opened up with forged internals etc. Will do all of the porting then but I'm happy how it goes at the moment for the money spent it was well worth it.

  6. #66
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    here is another single vs twin with a slightly different take on it.


  7. #67
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    Interesting video, Dave! Conclusion of "size your turbo(s) right and there's little difference between twins and a single"

  8. #68
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    yeh, as long as the turbo/turbos are size correctly there does not seem to be that much difference, apart from correctly sized twins seem to handle the back pressure issue a little better but go to big on the twins and spool suffers. even if they revatively smaller than the big single.

    i would love to have a definitive answer to the CFM flow of our heads and the flow at different valve lift that would go along way to suggesting what the max power would be with the correctly sized turbos.

    i have a plot of valve lift with respect to duration. but not flow.

    on a side note:-
    i am in the process of working out the best place to drill my front manifold for a EGT sensor and a back pressure sensor on the engine i am building. i have to sort out the details of the pressure damper to be able to get a stable reading whe the engine is running and the exhaust pulses are firing through the manifold. i have the rest of the parts to isolate the sensor so it does not melt with exhaust gas temp. i have a 100psi, 200psi, 300psi sensor so i might have to order a 60 psi sensor as i will see what happens with various different boost pressure from about 0.5 bar to 1.5bar (7psi to 22psi) on the standard turbos. 7psi is actually 7psi+14.7psi (ambient) so absolute pressure that the sensors measure will be 21.7psi to 36.7psi. so a 40-60psi sensor should do. well it will be better than 100psi, more resolution in the measurements.

  9. #69
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  10. #70
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    If you're going the route of stock ported manifolds it will work good only till around 380whp. After that it's gonna start back pressuring. We suffered from valve float over 400whp. We decided after to build a set of manifolds and that solved all our issues. IMG_20200124_123823.jpg

  11. #71
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    i have some stiffer valve springs to fit when i get round to gettig the cam reground for a bit more lift.
    i was going to open up the standard exhaust manifold outlet to the turbo for more flow as it does seem very small. but i am goingto put sensors all over the engine for pressure and temp (to calculate air density) and exhaust egt and back pressure. this will allow me to make an informed decision on what needs to change and where.

    do you know what is the flow rate of the standard heads. just wondering if they flow enough or do they need porting as well. or is it just the exhaust manifold that is the restiction to start with.

  12. #72
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    here is a bit of a manifold runner length debate in a video.

    actually i dont want to do it here i will start its own thread about it.
    Last edited by Davezj; 10-07-2020 at 05:59 PM.

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