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Throttle body bored 308

Discussion in 'Technical Q&A' started by Gianluca, Oct 14, 2004.

  1. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    I was thinking to bore my throttle body. Any reasons why I should not do it?
    1981 GTSi.
    Can I expect any real improvments without modifying anything else?
    It is my understanding that the Bosh fuel meter should be able to adjust accordingly.
    Thanks.
     
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  3. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    I have to say without a doubt, yes. However, I am the one who does that, just so the cards are on the table. After spending weeks in flowbench testing, I developed the 70mm TB.
    I have been waiting for at least one of those out who are running one to post, but I suspected this might happen. You see, it is a perfect "sleeper mod" No one can tell, unless you do, or they catch you with the air hose off and see it. Quite frankly, I would like to have gone more, perhaps a 75mm but the stock TB casting just would not survive long term, so 70mm was the limit. I have driven 308's with them, and I find that the only differance is it has a bit more upper RPM power, just as expected. No low end problems, no flat spots, it just pulls harder as the RPM's go up. Thats the beauty of the Bosch system, it is to a greater extent self adjusting. The motor pulls the air door down, the fuel delivery increases. Whether the TB is 17mm or 70mm the distributor "flapper" is what controls the fuel end, so it really does not effect the siz of the TB. However, there is a bit of a catch there. You must not over extend the fuel distributor. By this, I mean the air door must have a bit of travel left at full throttle. EXTENSIVE flow bench teting proves that is not a problem.
    BTW: No dyno #'s yet, as they don't stay stock long enough!!!!!!!!! Soon I hope.
    Kermit
     
  4. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    Kermit,
    thank you very much for the explanation.
    I am able to perform the operation but needed a little "reassurance" that you have provided.
    I will post some results once I am finished. I am sure I will need to ask more questions.
     
  5. Mike C

    Mike C F1 Veteran
    Lifetime Rossa Owner

    Aug 3, 2002
    6,075
    Southeast USA
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    Mike Charness
    Matt: How important is it to also bore out the plenum to match?
     
  6. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    Very important IMO, Mike.
    It can easily be done with a cheap rotary file and a drill motor if thats what is handy. Running into a lip will cause serious turbulance, as it disrupts the laminar column of air when it hits something. Falling of, or going to a slightly larger hole will have very little effect, as it just leaves a "void" in the flow in that area, no bucking up into the air stream, which is what happens in the case of hitting something. Watch a river. It will flow smoothly over a hole in the riverbed. If it hits a rock,watch how far downstream the water eddies.
    HTH
    Kermit
     
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  8. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,491
    MO
    How helpful would it be to also bore/polish the inlet manifolds?
     
  9. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,491
    MO
    Also, can you explain a KRANK™ VENT, and the benefits of it over not having one?
     
  10. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
    1,726
    Roswell, Georgia
    Full Name:
    Charles
    Matt--I have not gotten the 75mm TB on my car yet---still planning on it but other things keep steeling my time---lol
     
  11. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    Charles, you have some time left to steal? LOL.
    Let me answer the questions as best I can:
    Auraraptor, On the runners, it does help to port and polish them, but not nearly as much as one would think, as the passages in the heads are more restrictive, due to valve guides, etc.
    I prefer to open the plenum a bit, smooth it out, and to enlarge the air horns inside on the END runners(#'s 1-4 and 5-8). By opening the end runner openings, a more even flow is attained. This is a carry over from working on US V8's that ran the singl plane or X type manifolds, as they usually starve "being fed after the rest".
    The Krank Vent is the invention of an old friend of mine, DR Ted Schrode, of E.T. Performance. The "Dr." is a Masters Degree in Physics, and he retired from the Aerospace Industry.
    The KV is Patented as a quick action one way valve, and came into being as a cure for Harleys oil leaking, due to pressure buildup inside the engine.
    then as time went on, a few of Ted's friends were running turbo's on 4 cylinder motors, and blow by was a problem. So on went a KV, and it cured the problem, to probably everyones amazement, as it was for V twin motors,not multi cylindered ones.
    The actual "Valve" part that is inside weights less than a gram, so very little air movement is necessary to actuate it. This is why it works well on other motors, as it creates a vacuum in the crankcase.
    Now I do not claim to completely understand how that helps ring seal, but I have seen that it in fact does. Valve guide seal leaks are greatly reduced as well, as is most gasket weeping.
    A good example was about 18 months ago, when Larry stopped by on a Sunday morning, with his GT4 dripping oil so badly on his alternator, it was no longer chargeing. Not haveing much choice, as he was on his way to Vancouver from Seattle, he dropped in just hoping I might be here.(side note,it's Sunday, and I'm here,LOL). As I didnt have a spare set of cam cover gaskets, and there was no way to stop the leak, I came up with a set of KV's, put them on, and the leaking slowed to almost nil. IMO that had to be the result of vacuum in the crankcase, as he still had oil, and kept driving the car for months without dealing with the bad gaskets. as the leaking problem was amost completely gone.
    The unit itself has changed since it was first adapted to work with the Ferrari motors. I had originally added an oil separator to it as a one piece model. Now the new style simply replaces the hose fiting on the valve covers, and uses the stock oil separator, so they are is out of sight as well.
    I hope that helps clarify it!
    Kermit
     
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  13. Mike C

    Mike C F1 Veteran
    Lifetime Rossa Owner

    Aug 3, 2002
    6,075
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    Matt: I noticed on your website that the example throttle body is plain metal on the outside. Are you doing something to it that removes the factory red paint requiring repaint?
     
  14. Auraraptor

    Auraraptor F1 World Champ
    Lifetime Rossa Owner

    Sep 25, 2002
    11,491
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  15. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    On the paint issue, I generally use a paint remover of sorts, as just about every one that comes in has the paint pretty rough, so I remove it, then glass bead them, both for finish, and some slight surface hardening.
    And Auraraptor, It depends on what time of the day. I'm boss, babysitter (for crew) scapegoat, etc., LOL!
    Kermit
     
  16. atheyg

    atheyg Guest

    I am one of those that has a bored throttle body for my 328 from Kermit, since the purchase of my Boxer I have yet to take the time to install it but I must say his work is first rate. Kermit also gave me some heat shields and plenium gaskets which are excellent also.Kermit did the extras with the TB boring which makes a difference also by putting a smaller machined butterfly shaft and butterfly plate in and screws, Kermit really knows 308/328s well and I fully believe the bored TBs will make a difference of at least 10+ hp in a 328.Remember the Bosch FI was primarily used as a way for Ferrari to meet tightening US and worldwide emmission requirements and was not put on for performance so Ferrari missed out at the time IMO on some hp, especially on the QV and 328s as they have bigger air requirements due to 4v heads but use the same size bore TB as the 308GTSi, a definate bottleneck in the system.
     
  17. Mike C

    Mike C F1 Veteran
    Lifetime Rossa Owner

    Aug 3, 2002
    6,075
    Southeast USA
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    Mike Charness
    Matt: Side question... did you ever get dyno numbers just comparing the Krank Vent effects? I saw old posts talking about getting dyno numbers "real soon" back in 2003...
     
  18. Matt Morgan, "Kermit"

    Matt Morgan, "Kermit" Formula Junior

    Nov 12, 2003
    405
    Ferndale, WA
    Mike, I am almost embaraesd to say it, but no not yet on the KV Dyno Numbers. HOWEVER.. As the 308 that was being setup for this had to be put n "hold" due to the owner leaving for a 2 week holiday, and disapearing for 4months without a word.I'm happy to say that it is now withinn a cuple of weeks of going to "the Rollers", I WILL have them soon. It's kind of embarassing having a deal go "sideways" like that, and the necessary rescheduling has made it a challenge, but it is almost there. I am looking forward to it believe me, as I can then back what I say with the printouts!
    Wanna side bet?
    Kermit
    And Jeff, I thank you for the kind words!
     
  19. Mike C

    Mike C F1 Veteran
    Lifetime Rossa Owner

    Aug 3, 2002
    6,075
    Southeast USA
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    Mike Charness
    I hope you'll also be doing numbers on the bored TB too.
     
  20. racespecferrari

    racespecferrari F1 Veteran

    Jan 31, 2006
    7,539
    Suffolk, Uk
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    Pete.G By The Sea
    Hi Kermit, I know this an old thread but did you get any dyno figures for your throttle bore, alsp how much does your conversion work out at, Thanks Pete
     
  21. racespecferrari

    racespecferrari F1 Veteran

    Jan 31, 2006
    7,539
    Suffolk, Uk
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    Pete.G By The Sea
    Hi Kermit, I know this an old thread but did you get any dyno figures for your throttle bore, alsp how much does your conversion work out at, Thanks Pete
     
  22. GrigioGuy

    GrigioGuy Splenda Daddy
    Global Moderator Owner

    Nov 26, 2001
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    Dindu Nuffin

    As of today, Kermit has not published any data. Independent testing showed a 6 HP loss using the bored throttle body on a stock plenum. Further independent testing is planned using a matched TB/plenum combination

    See http://ferrarichat.com/forum/showthread.php?t=88743 for details
     
  23. racespecferrari

    racespecferrari F1 Veteran

    Jan 31, 2006
    7,539
    Suffolk, Uk
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    Pete.G By The Sea
    Hi, Thanks for the info it made very intersting reading,, its people like yourself who help us newbies, Thanks again
     
  24. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
    Rossa Subscribed Owner

    May 4, 2001
    31,326
    Birmingham, AL
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    Tommy
    We will have all the numbers in Mar. I need to fix my waterpump/alt belt first.
     

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