Chris NottMonster Motorsport
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  1. #1
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    Angry 1.8t wossner pistons compression ratio

    Hi there thought I'd let anyone out there know that wossner pistons stated std are not exactly standard fitted forged rods apr bolts bearings and h beam rods dyno printout was 230bhp with a new turbo turns out there not std but actually low compression pistons ie 150psi per cylinder comp ratio end up 8.5.1 were as standard comp ratio for bam engine is 186psi!!!so only good with an agu head and big turbo they actualy robbed me iv power any thoughts ???

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  3. #2
    <tuffty/>'s Avatar
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    Everywhere I have seen wossner pistons advertised they state the compression ratio... 9:1 is std on 210/225's and 9.5:1 on 150/180 hp engines... when I saw the title of thsi I thought you meant the bore but you were either sent the wrong pistons or didn't check what the comp ratio was before buying... std fitment normally relates to the bore in context of pistons... its generally up to the buyer to double check the comp ratio as when building an engine its generally a good idea to know what you are using to build it with...

    This isn't really a problem with the pistons or wossner...

    <tuffty/>
    Silver 2001 AMK S3. Silver alcantara interior... now with added powarrrrrrrr, torques. VAGCOM + KII-USB. >> My build thread...

  4. #3
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    Quote Originally Posted by darren t View Post
    t there not std but actually low compression pistons ie 150psi per cylinder comp ratio end up 8.5.1 were as standard comp ratio for bam engine is 186psi!!!so only good with an agu head and big turbo they actualy robbed me iv power any thoughts ???
    Thoughts: yes - low compression is a stupid old school belief that should have died years ago in 1.8T tuning.

    Also, for record, 150psi and 186psi are not compression ratios, they are compression readings from a compression test.

    Static CR such as 9.5:1 or 8.5:1 has absolutely nothing to do with a compression test, it's worked out mathematically.

    The compression test you carried out is effected by MANY things, cam timing, valve seating, ring seal etc etc....
    -------------------------------------------------------------------------------------------------

    Prawns TFSI Turbo'd 1.8T Track Car

    But I know nothing so ignore me.

  5. #4
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    Hi tuffty they're on Internet stating std size I even phoned tsr who quote that they are slightly lower but like I said when I spoke to them they told me they were exactly same as originals were as there not? 8.5.1 is not same as standard just giving people like me heads up as I'm wating for mine too come back there putting original pistons and goetze rings back in I'll let you know how much diffrence there is when she returns!! And how much bhp she gets on bills rollers as I have 11dyno runs with these pistons on a hybrid ko4 3inch downpipe front mount 230bhp with 256lb of torque was my best well see what happens with standard pistons and rings?

  6. #5
    <tuffty/>'s Avatar
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    Sounds like you were miss sold them... the same pistons are available in 9.5:1 too by the looks... like I said... if you were told they are like std pistons then thats the fault of the supplier rather than wossner so just want to make that clear as having a comp ratio of 8.5:1 is not a problem as such as long as its factored into the spec of your build...

    Most of us run higher comp ratios (9.5:1) as the 20v engine is a good design and doesn't suffer from the issues that older engines did meaning they required lower comp ratios...

    Bills race engine uses 9.25:1 JE's with a thinner head gasket (so higher comp ratio again) on a GT35 making nearly 600hp so clearly higher comp ratios aren't an issue on these... not that it helps you much lol...

    More timing and boost needed then to over come the lower comp ratio :D

    <tuffty/>
    Silver 2001 AMK S3. Silver alcantara interior... now with added powarrrrrrrr, torques. VAGCOM + KII-USB. >> My build thread...

  7. #6
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    Hi there prawn thanks for that just annoyed as I've got too pay 2 xlabour lol I defiantly was mislead 150 psi cam chain tensioner does rattle sometimes on startup but diss spears when revs applied???

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    My hybrid k04 not rs6 wheel but still is maxed out and holding 1.7bar of boost pmsl pulling 218gs of air air fuel12.5 so them figures are crap too say the least I can advance boost any more really on this setup as I'm putting the wossners in a build I'm doing in my garage lol myself fingers crossed going large port head and vf34 I want mabe even a vf35 off a wr1

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    i have had the same problem but because of the advise of someone else. i put wossner low comp in my car set up with a hybrid turbo etc. with very low boost i was getting 262bhp at the flywheel, which was low but mainly due to low boost levels because of a waste gate that likes to open a lot. i would not have thought 8.5.1 comp pistons would have caused you that much of a problem?

  10. #9
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    Hi there dan nice too hear that someone else has encountered my problem sorry too say so yeah I got 230bhp but was told actuator was ent set properly aswell so I have adjusted defiantly quicker what psi on the cylinders were you getting defiantly quicker with standards weren't it or is it just me?

  11. #10
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    Quote Originally Posted by darren t View Post
    Hi there dan nice too hear that someone else has encountered my problem sorry too say so yeah I got 230bhp but was told actuator was ent set properly aswell so I have adjusted defiantly quicker what psi on the cylinders were you getting defiantly quicker with standards weren't it or is it just me?
    I have not done a compression test, once i have some more money i am getting it set up again map wise now that i mostly sorted the boost problem. The car now feels quicker than it ever was, but like i said i dont think there will be a massive diffrence bhp. well i didnt think for me that it was worth changing over, its just a lesson learnt lol

  12. #11
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    My car was a rocket till I bent a rod with standard ko4 beat my mate Subaru now I can't lol and it's got a brand new turbo decat down pipe intercooler ect very annoying defiantly a lesson learnt I'll put them in my own buil I'll let you know results !

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    I'll be gutted if I don't get 180psi per cylinder when it comes back

 

 

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