How much Hp Loss???
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How much Hp Loss???

  1. #1
    Senior Member overpriced hallett's Avatar
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    Default How much Hp Loss???

    So Just curios how much Hp loss do you think I could get from a TT Autronic EFI deal from changing exhaust??? 519 ci Dart pro 1 325cc heads 14 psi boost no big deal cam +/- 630 lift full roller. (Meaning from open shorty dumps to threw transom) Water exit's at the end of the tails double walled +/- 2 in from exhaust stream with threw transom exhaust as opposed to no water at all with the shorty dumps?? pics to follow. Shortys are 3 in i.d and threw transom i.d are 3 in stepped to 3-1/2 to 4 to 4-1/2 i.d. First pic shortys, second pic threw transom, (and I have already taken out the mufflers due to thinking restriction) And I've already spoke to some very knowledgeable guys so please don't call your guy to elaborate as I am not looking for their opinions, Im just looking for you guys that have knowledge on this site about these things before I have a guy come out and perform the tune. And I'm just blown away on how much change that I have noticed. Thanks.
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    Last edited by overpriced hallett; 03-18-2012 at 08:59 AM.

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  3. #2
    AAARRRRRGGGGGGG!!!!! Motomatt68's Avatar
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    I would say you have lost 20% in the upper range and 40% in the lower range.

    You did mean hearing loss from running the shorties In a play boat didn't you?

    Matt

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    Senior Member Hass828's Avatar
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    Theres a good chance that the additional back pressure caused by the through transome setup has caused more of your exhaust to exit through your waste gates, thereby reducing your boost pressure. Backpressure in the exhaust is a real hp killer. The only way to regain it is to turn the boost back up with the boost controller or return the exhaust as it was. JMO.


    Nice setup
    "if we keep doing it the same way we always do..we will always get the same results"
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  6. #4
    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by overpriced hallett View Post
    ...I'm just blown away on how much change that I have noticed.
    Out of curiosity, what changes have you noticed?

    BTW, Sweet boat. Very sano.
    Last edited by Budweiser; 03-22-2012 at 08:06 AM.

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    Senior Member HighVoltage329's Avatar
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    I'm planing on doing the same exhaust on my Vector. Never thought it would choke down the out put.

  8. #6
    Senior Member overpriced hallett's Avatar
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    Quote Originally Posted by Budweiser View Post
    Out of curiosity, what changes have you noticed?

    BTW, Sweet boat. Very sano.
    Noticed a big difference in mid range and top end power. Meaning while cruising at around 70mph and standing on it it just lags, does not come to life like with the shortys, also after changing the exhaust it would not break 100 then when changing back it went over with ease. I know for a fact with this new exhaust it is way fat and can tell by the soot on the transom. I guess I was just looking to see if anyone else has experianced this.

  9. #7
    Senior Member overpriced hallett's Avatar
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    Quote Originally Posted by HighVoltage329 View Post
    I'm planing on doing the same exhaust on my Vector. Never thought it would choke down the out put.
    If it was tuned for it I guess it would be fine, I just have not had my tune up done yet. And besides I thought yours was a blower deal?

  10. #8
    Senior Member HighVoltage329's Avatar
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    It's at GT for some changes...

  11. #9
    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by overpriced hallett View Post
    Noticed a big difference in mid range and top end power. Meaning while cruising at around 70mph and standing on it it just lags, does not come to life like with the shortys, also after changing the exhaust it would not break 100 then when changing back it went over with ease. I know for a fact with this new exhaust it is way fat and can tell by the soot on the transom. I guess I was just looking to see if anyone else has experianced this.
    Seems odd that the EFI didn't correct for the rich condition. Are you running closed loop?

    How many RPM did you lose at WOT with the through transom exhaust?

  12. #10
    Senior Member overpriced hallett's Avatar
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    Quote Originally Posted by Budweiser View Post
    Seems odd that the EFI didn't correct for the rich condition. Are you running closed loop?

    How many RPM did you lose at WOT with the through transom exhaust?
    No open loop autronic system.

  13. #11
    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by overpriced hallett View Post
    ...I've already spoke to some very knowledgeable guys...
    Since there doesn't seem to be too much input from the group here, do you mind sharing the input you've gathered elsewhere? What opinions have you come across so far?
    Last edited by Budweiser; 03-23-2012 at 08:17 AM.

  14. #12
    Senior Member SoldHondaBoughtHondo's Avatar
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    Quote Originally Posted by Hass828 View Post
    Theres a good chance that the additional back pressure caused by the through transome setup has caused more of your exhaust to exit through your waste gates, thereby reducing your boost pressure. Backpressure in the exhaust is a real hp killer. The only way to regain it is to turn the boost back up with the boost controller or return the exhaust as it was. JMO.


    Nice setup
    X2 While i haven't messed with V8 turbo stuff i have done several m/c turbo deals and they all ran best with short/fat exhaust pipes. I tried a 2 bros carbon fiber exhaust can on one deal and it was the difference packing the front wheel most of the way through 3rd gear or not at all.
    Bike made 290/@22 psi (74 c.i.) on a dyno and on a guess 230 with the can.
    Same can on a n/a motor makes 1-2% less than open exhaust and jet changes didn't help.

    Seems like turbos just don't like any kind of restriction.

    The ignorant thing is, the can did a decent job on a n/a motor, with the turbo deal, not so much and turbo with a short pipe made about the same noise as n/a with the can.
    "A liberal paradise would be a place where everybody has
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  15. #13
    Or Seth, either one Budweiser's Avatar
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    A quote from the following article.

    Alameddine's attention to detail paid off when Thomson began making full dyno pulls, but there was something clearly holding back the engine. It was making more than 1,500hp, but was stymied by the mufflers on the dyno's exhaust system.

    It was a simple matter of too much exhaust backpressure and once Thomson's technician's uncorked the system, the engine blew unrestricted and instantly hit the 2,000hp mark. Keep in mind that the performance-hampering backpressure wasn't anticipated because the dyno's exhaust system already measured a large five inches in diameter.
    Twin Turbo LSX Engine - Super Chevy Magazine

    I never would have guessed!
    Last edited by Budweiser; 03-23-2012 at 11:09 AM.

  16. #14
    Senior Member oldschool's Avatar
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    I spoke with someone the other day about this very thing. He said that they saw little to no difference in performance between the two.

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