Page 1 of 3 1 2 3 LastLast
Results 1 to 15 of 34

Thread: Something about Pully sizes I don't understand

  1. #1
    Registered User
    Name:

    BlairTruck's Avatar
    Join Date
    Dec 2004
    Location
    Edmonton, AB
    Posts
    3,934
    Like
    7
    Liked 111 Times in 76 Posts

    Something about Pully sizes I don't understand

    From what i have read on here in the past month about pully size is that a lightning pully will add basically 2 more pounds of boost then if you put it on a harley

    IE. 6lb pully make approximatly 4 pounds on a Harley

    here is my question, if this is true, does that mean if i put a 2lb Lightning pully on my Harley i will get zero boost gains out of it?
    This has me stumped

    Am i totally missing something here?

  2. #2
    Registered User
    Name:


    Join Date
    Feb 2003
    Location
    DFW, Texas
    Posts
    6,995
    Like
    0
    Liked 0 Times in 0 Posts
    ok... this is simple... everyone over thinks this.

    an L has a 2.9X" upper pulley the HD has one X.XX" that & ECM tuning are the main reasons for the 2lbs less boost. If you swap an L upper pulley or snout you will gain 2 lbs of boost. Period.

    {edited:} Ryan explains this perfectly below... I was working off bad information & faulty logic...

    the bigger issue is the discrepancy between one company's quoted "6# lower" versus another's which is not the same diameter. If they are different diameters they both can't be a 6# pulley.

    A couple of the original guys started a table of Vendor "X" has a 6# pulley X.XX" in diam & Vendor "Y" has a 6# X.XY" in diameter.

    All you can do is look at your boost gauge (you did put one in right?) & see what your truck makes before & after.

    Rob W.
    Last edited by 2002GreyHD150; 05-03-2005 at 01:13 PM.

  3. #3
    Registered User
    Name:

    BlairTruck's Avatar
    Join Date
    Dec 2004
    Location
    Edmonton, AB
    Posts
    3,934
    Like
    7
    Liked 111 Times in 76 Posts
    Thats what i was thinking, doing the searching i seem a million times that a 6lb is only 4 on Harley
    And a few people say that 6lb was 6lb,

    When i get this 6lb pully i should see closer to 12lbs then 10 right

    my boost gauge is in the mail and was supposed to be here before xmas. And The LFP 6lb and predator should have gone in the mail this week

  4. #4
    Registered User
    Name:


    Join Date
    Feb 2003
    Location
    DFW, Texas
    Posts
    6,995
    Like
    0
    Liked 0 Times in 0 Posts
    {edited} since I was th idiot

    You will like the parts for LFP mark is agreat, Stand up guy... next E-Fan & Factory Tech Valve Body (FTVB!) you'll be screamin!

    Rob W.
    Last edited by 2002GreyHD150; 05-03-2005 at 01:11 PM.

  5. #5
    32V SC 5.4L #001
    Name:

    Madferraristi's Avatar
    Join Date
    May 2003
    Location
    Northern California
    Posts
    2,174
    Like
    0
    Liked 0 Times in 0 Posts
    If you put a +2 0n a Lightning you will see ~10 psi, same pulley on a Harley will give ~8 psi. A +4 will yield ~12 on an "L" and ~10 on a HD.

    The increase will be about the same, just a different baseline.

    The confusion lies primarily in the name the various pulleys were given by somebody.

    I have all sizes available, $199.90 with Gatorback belt, for any size.

    ************************CLICK TO VISIT MAD'S SITE************************


    '02, 32V, 5.4L #001, 14psi Whipple and a few other mods. 640 rwhp, 610 tq. CA Smog legal

  6. #6
    Registered User
    Name: Randell

    lerandell's Avatar
    Join Date
    Feb 2005
    Location
    San Antonio, TX
    Posts
    116
    Like
    2
    Liked 2 Times in 2 Posts
    Can this be made a sticky or added into the FAQ? I was totally confused by all the back and forth from everyone's post about 6=4 or 6=6.... this thread and specifically 2002GreyHD150's explanation nails it.
    Randell Kelly
    Black 2003
    http://www.kellymanor.com

  7. #7
    Yeah... I drive fast.
    Name:

    Speedin Bob's Avatar
    Join Date
    Oct 2003
    Location
    Indianapolis, IN
    Posts
    1,965
    Like
    0
    Liked 0 Times in 0 Posts
    Stuck...

  8. #8
    Drivetrain Calibration
    Name:

    Ryan@RhynoTune's Avatar
    Join Date
    Feb 2004
    Posts
    1,431
    Like
    0
    Liked 0 Times in 0 Posts
    Originally posted by 2002GreyHD150


    Lower pulleys are lower pulleys. The don't make less or more boost based on HD & L respectively. A quoted 6# pulley will ADD roughly 6# of boost to either engine. PERIOD. An 8# will gain how much? EIGHT POUNDS on an L on, an HD, on a Tbird S/C, on a Ford GT, heck even on a Pontiac Grand Prix... simple simple simple.

    The fact that so many people beat themselves in the head over the whole L versus HD thing is a complete mystery to me. Forget about the L. It doesn't mater. It doesn't even matter if you add the L-upper for 2 more pounds of boost... the 6# lower will add SIX MORE POUNDS to what you already have.

    the bigger issue is the discrepancy between one company's quoted "6# lower" versus another's which is not the same diameter. If they are different diameters they both can't be a 6# pulley.
    People need to reference their pullies in terms of diameter, not gains in PSI. Bottom line is a 8.5'' pulley will not gain the same on both engines.

    This is a simple calculation, the hardest part is figuring out why people can't grasp this simple concept.

    7.5/2.93= 2.55 blower ratio for a Lightning @ 8 PSI
    7.5/3.25= 2.30 blower ratio for a HD @ 6 PSI
    8/2.93= 2.73 blower ratio w/ 8'' lower (2#) for a Lightning
    8/3.25= 2.46 blower ratio w/ 8'' lower (2#) for a HD
    - Time out, so with a 8'' lower, you still aren't even at the same blower speed as a stock Lightning. So how do you gain two pounds? Do I really need to go on? I guess I must.
    8.5/2.93= 2.90 blower ratio w/ 8.5'' lower (4#) for a Lighting
    8.5/3.25= 2.60 blower ratio w/ 8.5'' lower (4#) for a HD
    - Another time out, so with a 8.5'' lower on your HD, your not even at the same rate as a Lightning with a 2lber. So you start w/ 6PSI, buy a so called 4lber, slap it on with your stock upper, and bam your at 10PSI!!! But the odd thing is, your still spinning your blower slower to get that same 10PSI than a Lightning does. It's magic
    I assume after reading that, someone is saying that isn't much of a difference. These numbers are small and meaningless. This is the part where I multiply the given ratio times 5250 RPM.
    5250x2.73 (L blower ratio for a 8'' lower aka 10 PSI)=14332.5
    5250x2.60 (HD blower ratio for a 8.5'' lower aka 10 PSI)= 13650

    So you have a difference of 900 RPM for the supposed same amount of boost. Bottom line, you do not get the same amount of increase on the two engines with the different uppers.
    2002 HD - 631 RWHP - 757 RWTQ
    Currently fabbing twin-turbos

  9. #9
    Registered User
    Name:

    PgreenSVT's Avatar
    Join Date
    Mar 2005
    Location
    Abingdon Md
    Posts
    1,599
    Like
    0
    Liked 0 Times in 0 Posts
    Thank you Ryan. That is exactly what I was thinking as I read the above posts. The larger the crank pulley the more difference in final boost between the L and the HD for the very reasons you explained. As the lower becomes larger the difference in the ratios for the 2 setups become larger resulting in a increasing disparity in boost levels as the lower pulley becomes larger. Swap on a 2.93 upper and then the pulley will be the advertised increase.

  10. #10
    Registered User
    Name:


    Join Date
    Feb 2003
    Location
    DFW, Texas
    Posts
    6,995
    Like
    0
    Liked 0 Times in 0 Posts
    thanks for clearing that up so perfectly Ryan... that makes a HUGE difference in my understanding...

    learned a new math forumla today... I hate math but like boost...

    Ryan, just to be sure I am clear where are the measurements taken? on the ribs I assume no the outer lip correct?

    Rob W

  11. #11
    Drivetrain Calibration
    Name:

    Ryan@RhynoTune's Avatar
    Join Date
    Feb 2004
    Posts
    1,431
    Like
    0
    Liked 0 Times in 0 Posts
    I usually take the measurement on the outermost rib wher the belt rides... Somewhere inside the pulley, not the lip that holds the belt if that makes sense?

  12. #12
    Registered User
    Name:


    Join Date
    Feb 2003
    Location
    DFW, Texas
    Posts
    6,995
    Like
    0
    Liked 0 Times in 0 Posts
    total sense to me... I am slapping myself for not thinking about the upper interms of ratio before.... it is just one of those "DOH!" things I guess..

    thanks again for the great info!

    Rob W

  13. #13
    Fast with Class
    Name: Tony


    Join Date
    Mar 2003
    Location
    Yorktown VA
    Posts
    1,644
    Like
    1
    Liked 7 Times in 6 Posts

    Lightbulb do a search for pulley formula

    if you do the above all you need to know is the pulley size. If you do not know, do another search for that also.

    Do your math and compute the boost for your truck.

    T
    DSG #50, Steig Stage V+-ported intake & plenum-TB 1650 cfm-Perf intercooler-SCT 2600 MAF-Cone filter-TCP dual e-fan-Kooks headers-JDM cat back-Hi flow cats-MP braclet-Billet 90 mm pulleys-2.93upper-6 lb lower-Grounding 0 ga wire kit-0 pos wire kit-AFCO dual fan heat exchanger-DM* oil catch can-J&S vampire anti knock-Chiller killer-3row rad-3 micron reusable SS oil filter-mag fine filter-FS2500 oil filter kit-Breed vlv covers-Trans vlv body mod-Mag Hytec trans&diff covers-pan hard bar-Rear sway bar-Bilstein ft shocks-QA-1 rr shocks-Police laser jammer-Cabin air filter mod-Fuctional Shaker Ram air hood-Sound deadening in cab-Innovation west SS rad cover-Laser jammer

  14. #14
    Registered User
    Name:


    Join Date
    Feb 2005
    Location
    s. e. Michigan
    Posts
    114
    Like
    0
    Liked 0 Times in 0 Posts

    duh?

    Rob and Ryan are to be commended for their efforts to help us understand, but this old fart has gotten nowhere in two tries, so far. Rob's X.XX is not for me and Ryan's details are great but I do not know what the L and HD start with. To make it simpler for this blockhead, could someone tell me what is the difference between the L and HD powerplants? Is it just pulleys? If so, is it upper and lower that are different? Thnx for this info and your patience but I know nothing about this stuff and own two HD's. Do I want to mess with them? Yes? How? No? Why not? thnx again!

  15. #15
    ResFirma Mitescere Nescit
    Name: stew

    bgstew6's Avatar
    Join Date
    Jun 2004
    Location
    Charleston, SC
    Posts
    18,059
    Like
    0
    Liked 0 Times in 0 Posts
    lightning upper pulley = 2.93 stock size
    Harley Upper pulley = 3.25 stock size

    both stock lowers are the same size.

    The lightnings smaller upper pulley increases the RPMs of the blower which in turn provides 2 more pounds of boost (8lbs) over the Harleys (6lbs).

    The lightning also has a more agressive stock tune. Couple this tune with the smaller upper pulley and that is why the Ligtning puts down Higher HP/Tq numbers than the Harley.


    How is that?

Page 1 of 3 1 2 3 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •