Exhaust Sizing on VR engines

Discussion in 'VR5, VR6 & Wx' started by drunkenalan, Sep 4, 2017.

  1. drunkenalan Paid Member Paid Member

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    I have searched and cannot find anything on the VR engine.

    I have a AUE which is going into my Bora, being an engine from a 4 motion and not having a 4 motion car I need some sort of jigsaw exhaust system, a mix of v6 up front and 1.8t at the back with a custom joining bit in the middle. unless someone knows of a 2wd V6 on the mk4 platform

    what size is going to be best? the engine will remain fairly standard, that doesn't mean a few bolt on's wont make an appearance.

    I see on ebay a manifold and downpipe kit, looks a bit like a copy of the Milltek stuff. would there be gains on the midrange torque from a better flowing manifold?

    I have almost secured a milltek sports cat, the ones I have are blowing.

    the rest is up to me.. 2.5 or 2.75? I think a 3 inch system would be too big.
     
    Last edited: Sep 4, 2017
  2. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    You will have such a jump in torque going from a 115bhp 8v to a 205bhp 2.8 24v, I really think you just need to forget semantics and get the job done and dusted.

    2.5 inch diameter exhaust is what you require dude.
     
    erreesse likes this.
  3. drunkenalan Paid Member Paid Member

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    I know Ed, I was for many years a planning engineer, planning mechanical builds and installations at power stations. its in my nature to plan everything out and do it all in one go, with as few return visits as possible, hence asking about manifolds and downpipes etc.

    if you tell me 2.5 is fine then I can work with that, I just don't want to build any additional limiting factors into the car.
     
  4. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    With unfamiliar automotive territory, you get the basics correct and as you get use to it, tweak or add more enginering. That is always the best bespoke option.
    Going from say 120lbft to 200lbft in a wider rev range, will be quite a large step and it will take a while for the novelty to wear off.
    The only reason to modify for all out performance is if you were competing. But that is a different category to what you are doing.
    With modern engines, additional performance tweaks will come from mapping.
     
  5. daffe New Member

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    As toyotec said just befor, in an N/a VR6 VR6 (12v & 24v) with serious mods ( head porting/cams/increasing compression ratio etc...) the one way to increase hp and your car's drivability is to tune/flashing your ECU...You could be impressed by results.
    if you' re Always interested by changing your exhaust pipes, you can see relantionship between exhaust diameter and engine power

    diam simple pipe double pipe
    1"1/2 ===> support 78hp 155hp
    1" 5/8 ==> 92HP 185HP
    2" ====> 144HP 290HP
    2"1/4 ===> 185HP 371HP
    2"1/2==> 232hp 463hp
    2"3/4==> 283hp 566hp
     
  6. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    Very old post from Alan, when he had plans to fit an AUE 24v to his Bora 8v.
    Not sure what happened to that exercise. I must ask him.
     
  7. daffe New Member

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    important is that he had find an answer to his question.
    let' get him give usan answer about that,hope he doesn't use too big exhaust pipe….
     
  8. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    He will be fine.
     

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