rebuild issue

Discussion in 'Engine, Fuel and Exhaust' started by hargun2, Oct 26, 2010.

  1. hargun2

    hargun2 Member

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    I had my motor rebuilt on a 2006 Classic by a company in the mid west and got it back, installed it, got a break in map from fuelmoto (awesome guys to work with) then after break in had it dyno'd at my local Harley shop here in Salt Lake. Since I was doing a complete re build I had it punched out to a 95 cube, they also put bigger intake and exhaust valves in the heads along with longer valve springs and a set of gear drive Crane cams 1-3005's with a .619 lift. The problem I'm having now is that there is a quite noticeable stutter/miss with the throttle at the 10 to 15 % open position that can not be tuned out by the shop. I'm being told by my local shop that the cam is way to extreme and the builder is claiming that my problem is a tuning issue. I have a master tuner on the bike with Vance and Hines slip on's. Any ideas this stutter/miss is driving me crazy?
     
  2. Hoople

    Hoople Account Removed

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    What makes a cam street-able is intake valve closing and overlap numbers. Would you know the rest of the specs on the cams. Until you get the inertia of the intake air working for you (high RPM), extreme degree numbers (intake closing/overlap) will work against you.

    Based on that crazy amount of lift, it sounds like you have a cam for true racing/performance.

    Is that base circle lift or after rocker ratio multiplier?
     
  3. hargun2

    hargun2 Member

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    I'm guessing base circle lift, It is listed on Cranes web site as a .619 lift along with the durations and it also states that this cam selection requires performance intake and exhaust systems. Based on the dyno run the torque and horsepower is not coming on until the engine is above 3500 rpm's and that's the point I'm trying to make with the builder. I shared my configuation with them along with my riding style which never see's the RPM needle rise above 3200 RPM. Since he claims no foul I dodn't know where to go from here. Idea's....
     
  4. Hoople

    Hoople Account Removed

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    You should upload the specs of the cams so all can see. With a base circle lift like that, I would expect the intake closing to be very late along with having a large amount of valve overlap for scavenging of spent gases. So expect to pay for it in a reduction of intake manifold vacuum. Vacuum is what makes the engine street-able when air inertia is high. How does it run under WOT at higher RPM?

    So many things come into play when dealing with engine VE, so getting a direct "here it is answer" is a long shot unless someone has been through the exact same setup issue/problem.

    Sometimes adding more spark advance just in the RPM band of your performance sag can help. But you need to first see what those advance numbers are before you add any more and you must know what intake valve closing point is. Do you still have the Ion knock retard sub-system still working.?
     
  5. hargun2

    hargun2 Member

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    It smooths right out once the throttle is opened above I'm guessing 15 to 20 percent. I guess not knowing exactly what components were installed I/you would not know what cam would have been a better selection, is this fair to assume? And from what information that I have provided would you agree that the cam is the issue preventing my local shop from tuning the sputter/ miss out....
     
  6. Hoople

    Hoople Account Removed

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    The answer could be a very simple map(s) change but you need to collect more data and check several key points before jumping to any conclusion. Like I said earlier, only a person who has the same setup as you or has already worked through a similar problem could tell you the answer you want to hear as quickly as you need/want it.

    Whenever you take any 1 ingredient (bore, compression, cam profile, stroke, head design, exhaust etc) to an EXTREME, you can easily cause other problems.

    In most cases you have to work through and troubleshoot a problem/issue like this. That is what troubleshooting is all about. I wish I could tell you what the combination to the safe is without studying it, but I can't.

    I am sure others will chime in with some good direction.
     
  7. Jack Klarich

    Jack Klarich Expert Member

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    Lift and duration will alter everything in a build, timing is going to be tricky at best, you have to ask your self what kind of power band you want, some compromise is going to be here IMO There are lots of formulas out there for builders to choose from, The owner of he bike needs to make hard decisions on what compromises he will live with, and there will be some, this is not an exact scienceIMo give and take, Good Luck, did you say what your compression ratio was? I missed that, it could be a factor also, Capital Jack
     
  8. hargun2

    hargun2 Member

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    I don't know if I made it clear that the motor is done and I'm stuck with a miss/stutter at minimal throttle position. The compression ratio is 10.25 to 1. and I was just wondering if you guys agreed with my local Harley dyno tuner that the use of a .619 lift cam is way extreme for a bagger cruiser and probably was not the best choice. Even went as far as to remove the Power Commander that was on the bike and installing a Master tuner so there would be more parameters to adjust and six hours of dyno time they could not tune out my problem. Just don't know which way to turn when the builder won't work with me, frustrating !!!!I
     
  9. Hoople

    Hoople Account Removed

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    Looking at valve lift ALONE tells you very little/near nothing.. What is more important is intake valve closing and overlap duration. Just based on that insane amount of lift, I would bet intake valve closing is Very late and overlap is well above your average everyday performance cam. Those numbers would be like that because the cam was really made for wide open-near wide open performance.

    You are in a tuff position because you did not build the engine and your not the one tuning it. You are passing information on to another person which is the worst spot you can be in.

    As I earlier said, intake manifold pressure is KEY when tuning a Delphi system. If the cam destroyed your intake manifold vacuum at part throttle, all you Map settings will not be correct. When I say the word MAP, I am not referring to look up tables. I mean manifold absolute pressure sensor settings.
     
  10. Jack Klarich

    Jack Klarich Expert Member

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    That seems like a lot of lift and will probably come alive outside of the power band you will be riding in, any chance they would swap it for a more user friendly cam?