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Thread: Turbo advice

  1. #1
    Mechanic beeRS's Avatar

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    Turbo advice

    Been contemplating forced induction for my 2.5 Duratec for a while. This would be my first turbo installation - I like a challenge. The engine is a new 2.5 Duratec I4 (not the V6) and currently internally stock. It's a street car, so as much as I like to see huge BHP figures, this engine can't be all about top-end and turbo lag. It needs to be usable.

    Can anyone offer me any advice on the following...

    1. What compression ratio should I aim for?
    2. Do I need forged pistons?
    3. Any recommendations on the turbo type / size? bearing in mind its a street car
    4. I don't mind fabricating manifolds, but easier if there is something available off the shelf for the 2.5?

    Any help or ideas would be much appreciated.

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    Re: Turbo advice

    I've never done a car only bikes but the principles are the same........so first thing i'll say is that boost is addictive - its automotive crack! Once its tried, you'll want more and more costs - either up front or in parts through rebuilds! First determine what power you think is enough then add 50% more headroom and build to that. Forged pistons should IMO be considered essential for serious power - cast will survive for a while with sub 1 bar boost but most will fail eventually and can cause a mess as the best option. With modern turbo's, sized correctly, lag is not an issue. A ball bearing turbo such as a GT3071R will easily give a reliable 400hp, a GT28R will squeak 300+hp but the former will also happily give 300hp but at lower and hence cooler boost temps! It is all a juggling act but a good sized intercooler will repay cost with reliability for boosted requirements. Engine management again, IMO, allows greater scope over fueling and ign. timing accuracy - the tighter the control, the better for off and on boost running. My best bike build was 1460cc, 370hp with Motec and intercooled, all steel internals, forged pistons, one off cams, 9.5:1 CR. I ran out of injector flow and never tried the upgraded ones that have 80% more flow potential, but its built to make 500+hp and its still a streetbike. Build a strong low comp N/A engine and adding boost is easy, build a weak one and boost will blow it to bits eventually! If your fabrication skills are good then the end result 'can' be better than 'one size fits all' off the shelf - I got my stuff fab'd by others but how I wanted it. Its not an easy question to answer but hope that helps - a bit?

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  4. #3
    Bodger

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    Re: Turbo advice

    Jesus you're building a 2.5? Is safe 350whp not enough for you? EFR6758 is the droid you're looking for. Should be making about 200ftlbs by 2500rpm on the 2.5 and tops out around 400-450hp depending on what fuel you use.

    But if you're looking to build the 2.5
    1. if you are going to run 93 I'd stick with 9-9.5:1, or if you're going to run E85 I'd go with 11-12:1
    2. Stock or forged are really your only choice, no non-stock cast pistons really exist
    3. EFR7163 would be the answer for you. Should be making 200ftls by 2800rpm and top out at 450-500hp.
    4. Probably nothing off the shelf that fits your chassis. There is the fab9tuning manifold for the NC miata that is 100% pimptastic level, all the other ones are junk.

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