2012 WRX STI - Engine Internals (ie. Pistons, Connecting Rod, etc) to support 600WHP+ - Page 2
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This is a discussion on 2012 WRX STI - Engine Internals (ie. Pistons, Connecting Rod, etc) to support 600WHP+ within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; I wouldn't bore the case halves all the way to 100mm unless you're sleeving it....

  1. #16
    OMG WTF MainFrame's Avatar
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    I wouldn't bore the case halves all the way to 100mm unless you're sleeving it.

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  3. #17
    Registered User sky_night's Avatar
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    Even with a closed deck build? I may be thinking of two separate things (still new to engine internals) but I though the closed deck helped when you bore things out.

  4. #18
    OMG WTF MainFrame's Avatar
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    What are they using to close the deck? Seems like it would be a little tougher (then again closed deck blocks tend to have overheating issues).. but that doesn't change the fact that 100mm leaves you with very little of the iron sleeve left, then if you ever need to rebuild it in the future that block is trash and you'll have to get a new one. Which wouldn't be a big deal, except that you're paying to have this one filled in, correct?

    The stock sleeves are already ridiculously thin on the 2.5L blocks.. going closed deck has no effect on that. Plus, what's the point in boring it more than is absolutely needed? You're not going to gain any power from the extra .5mm. Personally, I would prefer to keep the sleeve as thick as possible.

  5. #19
    Registered User sky_night's Avatar
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    Ok, I will discuss that with my tuner when I get a chance. Thank you for the very valuable input. Did you have any input on the 9.8:1 compression ratio? I've read a few threads where they say that's kind of high if you are trying to run pump gas. Now keep in mind on my 91 octane map the PSI will be low (probably similar to my pre-rebuilt engine boost levels). Just want to be sure I'm not getting a compression ratio that is "track only". Don't get me wrong I plan to go to the track, but also plan to drive to the grocery store

  6. #20
    OMG WTF MainFrame's Avatar
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    9.8:1 .. I would only run that with meth, e85, or race fuel. Even 9:1 is pushing it for 93 octane.. you would likely make more power with an 8.6:1 compression ratio on pump gas with more boost than with anything over 9:1. Not that you can't drive it with 9.8:1 cr on pump.. it would have great power off boost, but you probably wouldn't want to turn the boost up more than about 15psi. Where as the same setup with a lower compression ratio you could run closer to 25psi. It's a trade off. If you aren't putting expensive high octane fuel in it, then basically the higher the compression ratio, the less boost you can run before it starts knocking. It will make more power down low, but considerably less up top.

  7. #21
    OMG WTF MainFrame's Avatar
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    Oh yeah.. I wouldn't bother with the lower temp thermostat either. The only thing it would do is prevent the oil from reaching proper operating temperature.. if your oil is going to be too hot with the standard thermostat, installing a lower temp one won't do anything to change that. And you need to be sure your oil reaches 210 degrees to boil off any moisture that might be in your crank case.

  8. #22
    Registered User sky_night's Avatar
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    I can probably live with low boost on 91 octane. It will just force me to drive slower The more power you have the more you tend to use it. When I do go to the track I would definitely be using race fuel so would get to really enjoy the advantages to the cp at that point. Also do you have any recommendations on how to empty your fuel tank to put in race fuel? I've heard it's bad to aftermarket fuel pumps at less than 1/4 tank of gas but you need the tank empty when filling with race fuel

  9. #23
    OMG WTF MainFrame's Avatar
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    Empty empty.


    If your tune is on straight race gas, and you try to run it with 1/8 of a tank of 91 and the rest race gas, your engine will explode (or at least spin a bearing and lock up). If your tune is for 100% race gas, I wouldn't run that tune with anything less than 99% race gas in the tank. You can either pull the drain plug on the tank and drain it, or pull the feed line and cycle the pump to drain it.

    Whoever said not to run less than 1/4 of a tank was probably talking about racing the car with low fuel and a high flow pump in tank. I know a few people with dual 340 hangers in tank that can't race the car with less than 1/2 a tank because the pump sucks the saddle dry. That's why surge tanks are needed.

    Now if you're just putting around town, it should be fine to run it down to E.. just don't get on it unless you have a surge tank installed.

  10. #24
    Registered User sky_night's Avatar
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    I think they were referring to the fact that the gas in the tank keeps the fuel pump cool. So if you run it on less than 1/4 tank of gas then the fuel pump will start heating up and could cause failure of the fuel pump. I'll have my tuner show me where the drain plug is on the tank so I can use it next time. Also by race gas I mean 100 octane unleaded. At least that is what I was able to run on my 400whp tune (not that I ever got to test it out). It may be that after the rebuild with the higher HP tune it may require leaded fuel in which case a mix of fuels would be a problem. That is what you are referring to correct? Mixing leaded with unleaded fuel?

  11. #25
    OMG WTF MainFrame's Avatar
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    I was talking about mixing any fuel with any other fuel that has different octane and/or combustion properties. If your tune is on a fuel with 120 octane.. mixing that with some 91 left over in the tank you could wind up with something like 116 octane, and boom, there goes your engine.



    Also, I don't really think 100 octane would be enough to run any decent amount of boost on a 9.8:1 compression engine. I'm not sure if e85 would be high enough octane for that either. When I said racing fuel, I was talking more like c16.. or VP Import, which is over 120 octane.



    Honestly, unless you're building a dedicated drag car and have excessive funding, I would go with something closer to 9:1 compression ratio (or perhaps lower with your ACN 91 octane). You can baby the car on the street, and put VP Import in it at that track.. but then you're paying over $30/gallon on fuel. Spending over $500 to fill up a car is just beyond me. And having no power on the street with a very temperamental engine doesn't sound much fun either.

  12. #26
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    So I've been talking to my tuner and it looks like they are also going to have to upgrade some parts on the fuel rail. My question is at what point would I need to start looking at things like 2000cc injectors (vs. my 1000cc injectors), getting a fuel surge tank, etc?

  13. #27
    Registered User sky_night's Avatar
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    For the injectors I just found the following link Fuel Injector Calculator from WitchHunter Performance. So it looks like even up to 900HP at the flywheel my 1000cc injectors are enough.

  14. #28
    Registered User sky_night's Avatar
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    Well crap, newb mistake. I didn't update the number of injectors on the page. Looks like I may hit the max of my injectors with what we are currently trying to get out of the new engine build

  15. #29
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    2000cc injectors won't idle right on gasoline, you can't set the pulse width low enough to get it stoich.


    I've seen one person hit 500whp on e85 with 1000cc injectors, but he had his base fuel pressure set at 90psi, running a surge tank with inline Bosch 044 fuel pump. I wouldn't recommend pushing the fuel pressure that high.. he had all sorts of problems with it. On 1000cc injectors, aftermarket rails, a good high flowing pump, adjustable regulator, etc, I think 450whp on e85 is reasonable. You could probably hit 500whp on something like c16.

  16. #30
    Registered User sky_night's Avatar
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    After speaking with my tuner some more he stated that injectors larger than 1000cc are not needed unless running E85. So now here is the extra list of stuff for my car:
    316 Custom Fuel Rails
    Radium FST-R Fuel Surge Tank W/ integrated FPR and Walbro F90000267
    Radium Integrated Wiring Harness

    They also found after tearing apart my engine that the clutch is completely toast so getting the following clutch to replace it:
    Clutch Masters 6MT FX350 Sprung Fiber Clutch

    Hopefully everything comes together and I can start driving the car in the next couple weeks so I can hurry and get through the 1,500 break in phase.

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