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Thread: Forged internals.

  
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    chuntnigton101's Avatar
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    Forged internals.

    just wondering at what point (psi, power, torque) you guys are switching to forged pistons and rods? does anyone still use the their car every day that runs forged internals? i have seen some pistons and rods on sone tuners sites.

    also how much "can" the stock bottom end take? is the stock crank pretty robust?

    im new here so please dont kill me

    thanks Chris.

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    mattcoupturbo's Avatar
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    Depends which engine you are refering too, if its the Z20 LET the generally thought of level is around 280-300 Bhp before you need to uprate the internals. If its the VXR engine then its higher as this comes with better pistons, under piston oil spray nozzles and also does away with the crank balancer on the Z20 LET. If your thinking of upgrading your engine by fitting a new turbo and you want it to be reliable and last a while then sorting everything would be a good idea. As you said you can get forged pistons, conrods etc already for the Z20 LET so is a good idea. If you could get hold of a VXR bottom end you could have the crank etc all balanced properly.

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    as matt said, from everything i read before i started my upgrade, if your planning anything more than 300hp you should uprate the internals..
    The VXR already has forged internals and oil sprays to cool the pistons..but it would be guessing how high you can go, but IMO you might see closer to 400 before needing anything stronger.

    i am getting some ARP rod bolts anyway as some have mentioned the Z20LET's are a bit of a weak point, even tho i prolly wont get that close to 300 hp...

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    MarkyG's Avatar
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    get some mahle forged pistons from the c20xe, theres a sweedish car running 550hp on those with no problems. more expensive forged pistons can take upwards of 600 hp.

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    300 bhp is thought to be about the limit for an everyday car (Z20LET).

    As suggested, the LEH already has uprated internals including forged pistons with teflon coated skirts, under piston cooling via an oil spay bar, and single balancer shaft rather than the twin design of the ZLET.

    One of the biggest problems for the ZLET is cooling, so anything to help that is going to give you safer higher bhp.

    You don't actually say what bhp you are aiming for - so it is difficult to advise you of what you may need?

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    sorry Scottyboy it was just a general question. its like everything i guess, you can "make" anything run for a while, but how long is normally dont to the components you run and the power levels you are at!

    i just wondered if there was a general rule of thumb that said at xx psi, xxxbhp or xxxlbsft its recomended to upgrade to forged internals.

    so is it fair to say anything below 300bhp you are cool with the stock stuff?
    after 300bhp you need to start to look into getting a LEH bottom end (or just the whole block lol)?
    and anything near 400bhp you may as well look at proper forged pistons and rods?

    also and i haven't seached so if i need to just say, what the majour cause of these engines going bang?? is it cooling, people getting gready with the boost, fueling, etc, etc????

    thansk Chris.

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    All just my opinions of course Chris - but basically to get over 300bhp on the ZLET you need to change the exhaust manifold and turbo which gets into serious money and of course because of this there are not many options available.

    Therefore most only reach just shy of the 300bhp mark, and I've only ever heard of one engine going pop - which was an early turbo (which had weaker piston crowns) - and it was because it was running extremely lean. So it's reasonable to assume that up to 300bhp is 'safe' with stock internals - for all we know really, they may be safe higher too, but nobody really knows for a road environment.

    Personally I didn't want to risk it and was planning to rebuild my ZLET, however it worked out cheaper to completely transplant an LEH (vxr) complete new engine, which already has the strengthened parts. Again nobody has tuned this past around 305bhp (Jom's car) as the same problem exists with the manifold and turbo. Hopefully my car will be a test bed for reaching 350bhp and then some - so who knows whether it will go pop or not.

    So the short answer to your question Chris is that nobody really knows - we can only go by what we have learned from the forums, members experiences and advise from the tuners. Gearbox's however, seem to be suffering far more from failure than the actual engines themselves

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    Neilc's Avatar
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    Always nice to find a good thread and read up

    I think the VXR bottom end is going to be a very popular upgrade when Vauxhall release it
    Insignia CDTI 160
    200bhp DTUK
    2007 Suzuki GSXR for the weekends

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    thanks Scottyboy. im guessing the major reson people aren't going bigger on the trubo is the space restrictions with the turbo at the fron! has no one tried to move the turbo to above the gear box like the Ford guys do??? it would need a new exhast and intake route but it shoukd free up quiet a lot of room for the turbo!

    hmmmmm maybe a tuner should try some compound boosting?!?!? lol

    thanks Chris.

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    The problem is the standard exhaust manifold design - it's too restrictive to flow the air capacity needed to increase the performance much past 300bhp. It's very expensive to cast a new design manifold, and tubular ones tend to crack. As the tuners need to offer some kind of warranty, it is just not worth the investment cost vs the amount of people they would have interested vs the amount they would need to charge to get tooling fees back vs a big question over reliability. Dbilass really missed a trick here imo, as they could have really opened up their manifold design to get much, much more from it.

    There is also a distinct lack of room under a ZLET G bonnet as you say - removing the battery is an option. Sequential charging is interesting, with twin seq turbo's or even a turbo and a s'charger, but again very expensive to develop with too many unknowns.

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