Page 1 of 2 1 2 LastLast
Results 1 to 10 of 16
  1. #1

    Join Date
    Aug 2006
    Location
    Gonzales, La
    Posts
    2,145
    +1
    9

    Fuel injector size discussion (interest to turbo guys)

    Ok folks, with my current turbo setup I either have to figure out a way to lower the boost, or add fuel. Adding fuel seems to be more fun, so I decided to do some calc's on injector sizing. There are some exciting new things on the market, such as 79 lb/hr High-Z injectors, so us 3-injector guys have some new possiblities.

    Starting out, I wanted to make sure I could get my calc's to line up with what we've seen regarding stock injectors, which max out around a Stage 2 or roughly 230 hp.

    Yes, we all know by now that the stock fuel pressure is 58 psi, while most injectors are rated at 44 psi. But what most fail to consider is that the stock fuel pressure may be 58 psi, but the stock dP is fuel pressure minus boost pressure, or only about 51 psi.

    Sooo. . . the stock injectors at 51 psi will flow around 42 lb/hr. I knew that boosted motors usually have BSFC's between .5 and .6, so I ran the calc's there and in between. Lo and behold, at a BSFC of .55 and 42 lb/hr, I get a max hp of 229 hp, which is exactly what Riva claims from their Stage 2, which runs stock injectors.

    Everyone also seems to agree that upgrading a Stage 2 with a RR/Green/A-kit wheel makes it run lean and you need to upgrade to 42's. Coincidentally, the RR/Green/A-kit wheel adds 10 hp to the 230, and by the same calc's, they 42's will support about 240 hp at 10 psi boost (48 psi injector dP).

    So, everything is lining up quite well.


    Now, moving on to some 50's, since they are next on the "most common" list since because they work with the Riva S3 ECM.

    Assuming 11 psi boost as with the supplied Riva S3, the injector dP becomes 47 psi, and the 50's act like 52's. A 52 lb/hr injector will support 284 hp. Depending on who's dyno numbers you believe, that will cover the regular Riva S3. Most of the guys in-the-know are saying the S3 is nowhere near the 296 hp they claim, but more like 255 hp.

    Now for the turbo people... Assuming 15 psi boost, the fuel injector dP is now only 43 psi. Essentially, the 50 lb/hr injectors really just flow 50 lb/hr since they are rated at 44 psi. Also, I dropped the BSFC down to .52 since it will be lower for a turbo. Other 4-valve turbo engines have demonstrated a .52 also. Either way, they will only support 285 hp at that pressure, or as high as 295 hp if you're willing to lean it out a bit. I think that's around the range where Jerry max'd out his 50's. Either way, don't expect more than 300 hp (14 - 15 psi boost) out of the 50's and Riva ECU without a rising rate regulator.


    Moving on to the bigger stuff. . .

    A 63 lb/hr injector is a common high-Z injector. I had to iterate a bit to get the max hp of these injectors because of the whole boost/hp/flow relationship. I found that the 63's will max out at a little over 340 hp, which is reached at about 19 psi boost. Keep in mind that our injector dP is now only 39 psi, so they actually flow less than 63 lb/hr.

    Going up to the big dogs. The newest high-Z injector is a 79 lb/hr and I believe it will cover the needs of all but 1 or 2 guys in the world. Iteration revealed that these bad boys will support about 405 hp at 25 psi boost. Again, this is at the stock fuel pressure of 58 psi, for a dP of only 33 psi.

    Of course, adding a rising rate regulator could increase these power thresholds quite a bit, especially on the bigger injectors. Assuming a base pressure of 58 psi and a 1:1 rising rate regulator, the limit of the 50 becomes 330 hp, the 63 will support 415 hp, and the 79 will go to a whopping 525 hp.

    Comments?

    Mike


  2. #2
    HORSEPOWER JUNKIE 9secZO6's Avatar
    Join Date
    Jun 2007
    Location
    Belle Chasse, La.
    Posts
    2,006
    +1
    1
    u are confirming what I suspected of the 63s, nice. Using the r/r reg. AND a LOT of tuning on the idle/bottom-end/transition to high (7k+)rpm will be need via fuel controller, but doable. The person perfecting this map would be my hero (u listening Brian?) Killer work Mike

  3. #3
    Site Admin Green Hulk's Avatar
    Join Date
    Apr 2005
    Location
    Morgan City, LA
    Posts
    36,398
    +1
    2,524
    damn good info Mike

  4. #4
    ctriverguy's Avatar
    Join Date
    Aug 2007
    Location
    Ipswich, Massachusetts, United States
    Posts
    1,509
    +1
    8
    This stuff is the very reason I cant stay away... hats off to ya, thanks for sharing.

  5. #5

    Join Date
    Aug 2006
    Location
    Gonzales, La
    Posts
    2,145
    +1
    9
    Quote Originally Posted by 9secZO6 View Post
    ...AND a LOT of tuning on the idle/bottom-end/transition to high (7k+)rpm will be need via fuel controller, but doable.
    I got something in the works.

    The first challenge I have is choosing between 63's and 79's. There's not much price difference, but I hear the very large High-Z's are tricky to tune at low PW's.

  6. #6

    Join Date
    May 2005
    Location
    Toronto, Ontario, Canadian "EH"
    Posts
    97
    just get the new 212lb/hr injectors and your good to go


    i have seen 65's and 75's around, i don't no if they would work for you though

  7. #7

    Join Date
    Aug 2006
    Location
    Gonzales, La
    Posts
    2,145
    +1
    9
    Quote Originally Posted by SHEP View Post
    ...i have seen 65's and 75's around, i don't no if they would work for you though
    Yea there's a whole slew of low-Z injectors available. I've been running 84 low-Z's on my Z28 for years now. However, the peak-and-hold injector driver circuit is way more complicated than the conventional, so I'm going to stick with High-Z for simplicity's sake.

    BTW, I've seen 120's and 160's. The 160's would support over 1000 hp on our engines with the rising rate regulator!
    Last edited by engineermike; 12-24-2007 at 03:05 PM.

  8. #8
    EZ Dock of Long Island Shibby1485's Avatar
    Join Date
    May 2005
    Location
    Long Island, NY
    Posts
    9,464
    +1
    4
    and the maximum we can push the stock fuel pump is like 75-80psi?

    so safely with a FPR and 20psi of boost, the starting point of the FPR shouldn't really exceed 65psi, maybe a little more?

    good thread!

  9. #9
    home of the dislexic fingers breon's Avatar
    Join Date
    Aug 2007
    Location
    port st lucie fl
    Posts
    3,471
    at what point is the stock fuel pump not able to keep up with the volume required anymore.... pressure is one thing... volume is another

  10. #10
    HORSEPOWER JUNKIE 9secZO6's Avatar
    Join Date
    Jun 2007
    Location
    Belle Chasse, La.
    Posts
    2,006
    +1
    1
    go w/ the 63s mike, that thing does have to idle u know atomization won't be for chit if too big....and "at what point is the stock fuel pump not able to keep up with the volume required anymore.... pressure is one thing... volume is another"
    the pump seems to be good to at least 20 psi of boost, but retro-fitting another is pretty easy. I have had the whole thing out and another bosch unit would fit easy, but u could put damn near anything in there and not spend more than a couple hundred doing it. U could then feed 500 ponies w/ no issues

Page 1 of 2 1 2 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Stock fuel injector size?
    By tornado34 in forum 4-Tec Performance
    Replies: 26
    Last Post: 06-09-2015, 10:00 AM
  2. honda f15X turbo stock injector size
    By gzk in forum Honda Performance
    Replies: 12
    Last Post: 08-25-2013, 09:40 AM
  3. Fuel Consumption from 42's to 60 lb Injectors
    By rxpxfire in forum 4-Tec Performance
    Replies: 11
    Last Post: 11-02-2009, 11:23 AM
  4. How to test Fuel Injectors
    By Mr Bill in forum Yamaha How To & FAQs
    Replies: 6
    Last Post: 07-18-2007, 04:23 PM
  5. Stock Fuel Injectors: What size are they???
    By Importracer in forum Kawasaki PWC Performance (4-stroke)
    Replies: 3
    Last Post: 04-08-2007, 08:31 AM

Posting Permissions

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