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  1. #1
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    Will Catless loose my Tq on my VT2-500 setup??

    hi guys i have the ess vt2-500 on my z4m, im trying to get the MOST performance possible from my VT2-500 setup, im loving the new found horsepower with my new cooling mods that came with the VT2 upgrade, AITs are nice and my new strab oil cooler is doing a great job @ keeping oil temps in the perfect range.... BUT.... as usually with a s/c s54 i want more tq really, i do love revving this thing to get at my 8psi but id just like alittle more down low.....

    firstly some things to note, my VT2 kit for some reason boosts to 7.8ish psi, if i clip the limiter it shows 8psi, no issue and my AFRs are looking bang on where they should be, im wondering if anyones got any idea's to gain alittle more tq on my setup?

    Fr8tdog feels if i run a meth/water kit i can spray on the smallest nozzle on the i/c outlet tube to lower AITs further and gain good power, he infact see's +40hp and +30Tq by this simply approach, no tuninig is needed as this is simply to lower AITs, Tonesta also used this to great effect.

    Exhaust.... the biggy, i wondering if i custom build an exhaust setup if i can gain some Hp + Tq, now i dont know how this works with a s/c car, on a turbo ive always wanted as low back pressure as possible, im guessing the s/c motor relies on back still and wont benefit from say a larger bore pipe work, i was thinking a slightly larger bore with Cat delete would maybe make power BUT ive seen 1 person show losses in power on a s/c s54 with a larger bore exhaust/cat delete. Anyone got any ideas or thoughs on what ive just posted???

    p.s please excuse spelling as im using Iphone 4 :-)
    cheers guys.

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    youd have to check woith your tuner on the meth part, as it is a fuel, you may need a different tune, but shouldnt.

    as for your boost, your fine with 7.8 as opposed to 8.0, thats as close as your gonna get really, and that will fluctuate with different conditions a bit as well.

    the problem with low down tq on s/c motors is that the s/c robs a small amoutn of power down low to get the s/c spinning, so to answer your question on tq increase by going catless, i could be wrong, but i think down low you may loose a small amount, but gain it throughout the powerband, again, i may be and probably am wrong, on that, so wait for someone else to chime in Click here to enlarge

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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    youd have to check woith your tuner on the meth part, as it is a fuel, you may need a different tune, but shouldnt.

    as for your boost, your fine with 7.8 as opposed to 8.0, thats as close as your gonna get really, and that will fluctuate with different conditions a bit as well.

    the problem with low down tq on s/c motors is that the s/c robs a small amoutn of power down low to get the s/c spinning, so to answer your question on tq increase by going catless, i could be wrong, but i think down low you may loose a small amount, but gain it throughout the powerband, again, i may be and probably am wrong, on that, so wait for someone else to chime in Click here to enlarge
    +1 on asking ess about meth system. cat delete can't hurt, your still going to have an exhaust for back pressure, its just going to get to the end of the system alot easier. keep us posted on what you find out from ess.

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    There is no reason why you wont gain power from removing those restrictive cats, you will gain torque everywhere. This is not a naturally aspirated car with a tuned exhaust to take advantage of exhaust scavenge and momentum (which is where the exhaust may need some backpressure). Your car needs to get rid of its exhaust as efficiently as possible, not only that, but it has VANOS which can be tuned for even better cam phase angles at some point if you feel a loss in torque; but I doubt that will happen with a blower.
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    Click here to enlarge Originally Posted by LostMarine Click here to enlarge
    youd have to check woith your tuner on the meth part, as it is a fuel, you may need a different tune, but shouldnt.

    as for your boost, your fine with 7.8 as opposed to 8.0, thats as close as your gonna get really, and that will fluctuate with different conditions a bit as well.

    the problem with low down tq on s/c motors is that the s/c robs a small amoutn of power down low to get the s/c spinning, so to answer your question on tq increase by going catless, i could be wrong, but i think down low you may loose a small amount, but gain it throughout the powerband, again, i may be and probably am wrong, on that, so wait for someone else to chime in Click here to enlarge
    LM thanks bro, RE the boost, its supposed to be 7psi but seems to hit 7.8 most of the time and sometimes 8psi if i clip the limiter, are pulleys a "roundabout figure"?? The car also made slightly more power than its rated for, AFRs are 12.3 at redline so nice and safe....im not complaining as ive got free boost here :-) just wondering if most pulley's have discrepancies?

    i will try Catless and see what happens, the car made 450Whp @ around 7.8 psi..... id ideallly like to get this figure to 500Whp WITHOUT adding anymore boost, so now im going to try and build a response motor, Shrick cams, larger throttle bodies, larger bore catless exhaust system, port and polish work, okada coils,......... most of these bits are aready purchased and just need putting in :-) im trying to build a screamer here :-)

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    well, different conditions will slightly affect the boost you get, but the fact your not catless yet could be why your hitting 8 psi and not 7. i know i dropped about 1-2 psi by going fully ctaless on my Lightning.

    once you do all that motor work, im sure you already know, you'll definatly need a retune. all of the more free flowing mods you do are gonna drop that boost back down a bit as well

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    Youre gonna need to retune the motor especially with the new cams, your volumetric efficiency is different when you change the cams hence needing the retune. Exhaust MAYBE you could get by without a retune but cams a must. Show us pics of your build, this thing sounds like its gonna be awesomem.
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    Click here to enlarge Originally Posted by beedub Click here to enlarge
    Fr8tdog feels if i run a meth/water kit i can spray on the smallest nozzle on the i/c outlet tube to lower AITs further and gain good power, he infact see's +40hp and +30Tq by this simply approach, no tuninig is needed as this is simply to lower AITs, Tonesta also used this to great effect.
    I would heed Fr8tdog's advice here, you don't need a new tune (although that wouldn't hurt) but lowering IAT's is always a good thing.

    Click here to enlarge Originally Posted by beedub Click here to enlarge
    Exhaust.... the biggy, i wondering if i custom build an exhaust setup if i can gain some Hp + Tq, now i dont know how this works with a s/c car, on a turbo ive always wanted as low back pressure as possible, im guessing the s/c motor relies on back still and wont benefit from say a larger bore pipe work, i was thinking a slightly larger bore with Cat delete would maybe make power BUT ive seen 1 person show losses in power on a s/c s54 with a larger bore exhaust/cat delete. Anyone got any ideas or thoughs on what ive just posted???
    What exhaust are you using currently?

    Going catless won't cost you power or torque, you will pick it up. Maybe if you were NA some people make the backpressure argument (which I don't believe in anyway) but you will not lose torque boosted going catless especially if you have the factory cats all in place and not high flow cats.

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    I would heed Fr8tdog's advice here, you don't need a new tune (although that wouldn't hurt) but lowering IAT's is always a good thing.



    What exhaust are you using currently?

    Going catless won't cost you power or torque, you will pick it up. Maybe if you were NA some people make the backpressure argument (which I don't believe in anyway) but you will not lose torque boosted going catless especially if you have the factory cats all in place and not high flow cats.
    never understood that argument. if you dropped the cats on your e46 then you put some kinda after market headers on to accomplish that. and we've seen comparable gains from the ebay stuff vs name brand (although fitment reflects cost)

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    Click here to enlarge Originally Posted by dreikraft Click here to enlarge
    never understood that argument. if you dropped the cats on your e46 then you put some kinda after market headers on to accomplish that. and we've seen comparable gains from the ebay stuff vs name brand (although fitment reflects cost)
    I never understood it either, all I know is when I dropped cats I gained power.

    The integrated cat into the US E46 M3 header cost power, pure and simple.

  11. #11
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    im a uk owner so already have the really well designed CSL headers, exhaust has bone stock mid section with stock "400 cell cats" and RPI Xpipe and straight pipes.........

    im sure i read about a e46 on this very site with vt2 that lost substantially low down when he ditched the stock cats...... im worried about spending big cheese to loose power....

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    Click here to enlarge Originally Posted by beedub Click here to enlarge
    im sure i read about a e46 on this very site with vt2 that lost substantially low down when he ditched the stock cats...... im worried about spending big cheese to loose power
    Hmmm, who was it?

    Click here to enlarge Originally Posted by beedub Click here to enlarge
    im a uk owner so already have the really well designed CSL headers, exhaust has bone stock mid section with stock "400 cell cats" and RPI Xpipe and straight pipes.........
    I see no reason why you would lose anything down low by ditching the stock cat. Even a higher flow cat should make a nice difference.

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    ill give it a go and see.......

  14. #14
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    im tellin ya, you may lose it down low, but you may also need a retune because of it to get it back and then some. theres no way to know for sure

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