tuning for pump gas
+ Reply to Thread
Page 1 of 2 1 2 LastLast
Results 1 to 14 of 17

Thread:
tuning for pump gas

  1. #1
    northern member Canuc's Avatar
    Join Date
    Jan 2008
    Location
    Nechako
    Posts
    602

    Arrow tuning for pump gas

    do any of you guys running pump gas have a hard time keeping the egt below 1500*. I always find that I need to jet way rich with pump 91 compared to race gas and today was no different , was tuning a new 516 bbc 10:1 compression afr 305 heads ,victor intake with 850 demon , comp xr292r , dry headers . to get egt below 1600* square jetted at 97's with no power valves ,timing set at 36*. it's in a 19.5 tunnel with B impeller @ 6200 and ran out of time with egt 1400* @ 4-4500 cruise 1550* @ wot. more jet , smaller air bleeds ? oh and no a/f meter but would like to get one . any suggestions thanks Rick .

  2. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  3. #2
    Highaboosta Unchained's Avatar
    Join Date
    Dec 2007
    Location
    Ada, Michigan
    Posts
    3,431

    Default

    When I ran 850 holleys I ran # 80 jets with power valves.
    If you dump too much fuel in it will still be burning coming out the pipes and your egts will be high. Is the motor sluggish with that much fuel ?

    I would not tune by the EGTs.
    I removed my EGT gauge and tune 100% from the O2 sensor.

    36 degrees of timing might be high for pump gas.

    Twin Turbo 1800 HP V-Drive lake boat

    http://s621.photobucket.com/albums/t...t=MAH05771.mp4

    Quote Originally Posted by Trigger View Post
    No one cares about your buddies old antiquated garden hose technology.
    Quote Originally Posted by MAXIMUS View Post
    I think I could run more boost but it's a real hand full right now

  4. #3
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    I would try the timming at 32 then try again. Pump gas is not what it used to be and when you buy 91 your lucky if your getting 89.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  5. Remove Advertisements
    PerformanceBoats.com
    Advertisements
     

  6. #4
    Lurker
    Join Date
    Dec 2007
    Location
    NC
    Posts
    1,417

    Default

    We have found that going from race gas (leaded 110) to Unleaded race (I think it is 107) requires going up 3-5 jets. Going to Unleaded Pump Gas (93) needs between 5-7 jet sizes to stay at a baseline AFR.

  7. #5
    northern member Canuc's Avatar
    Join Date
    Jan 2008
    Location
    Nechako
    Posts
    602

    Default

    the 850 Demon has annular boosters and was 80 pri. with a p.v. and 88 sec. out of the box ,with 30* timing the first time out saw over 1700* yikes. pulled the p.v. and jetted square with 92's and 32* timing better but still saw 1650* at wot.then it got 94's with 34* better but still around 1600*finally the 97's with the timing at 36*. runs nice but started to feel a little fat the last time on the bottom coming out of the hole if you just were rolling into it. what do you guys that use pyro get your egt at ? btw water temps steady at 160 * and the plugs show no signs of meltdown on them thanks Rick

  8. #6
    northern member Canuc's Avatar
    Join Date
    Jan 2008
    Location
    Nechako
    Posts
    602

    Question what should max egt be

    going to try this again on the weekend . engine builder says timing should be good at 36*. going to jet up to a couple sizes and try timing up and down a couple * and try to get pyro's to stay under 1500* anybody got egt # 's to share ? what are the bad ass 800hp pump gas guys running at ? this is just a 600 hp 516 some leaded gas with some octane would do it but the owner wants to be able to run 91 unleaded

  9. #7
    TEN THIRTY ONE RCB19's Avatar
    Join Date
    Dec 2007
    Posts
    1,293

    Default

    On my deal we never measured EGT's on the dyno just AFR and re-jetted to get that correct. We ran 100 oct unleaded on our first hard pulls to be safe and found that the motor didn't like any more or any less than 33* of timing. We then tried the 91 oct pump gas and made the final tuning on that. If I remember correctly we did jet up a untill the HP started to fall off and then went back. Ended up with 907 on the final pull. However I don't trust the consistency of the 91 from pump to pump. My motor is right at the edge at 11.5 to 1 comp so I mix 1 part 111 race fuel with 4 parts pump gas to get 95 oct. Insurance!!! I wish we did measure EGT's but one day on the dyno is just not enough time.
    RCB

  10. #8
    cfm
    cfm is offline
    Banned
    Join Date
    Jan 2008
    Posts
    1,263

    Default

    Most AFR BBC's between 8.75:1-10:1 I've seen in boat application end up around 35º-36º, however these have less overlap cams for I/O wet exhausts.

    Too much fuel can raise EGT's.
    Less compression can have higher EGT's than more compression. Are we sure 10:1 ? Is this measured or guessed ?
    Not enough timing can raise EGT's. Worth to try another few degrees for a run but be careful.

    Also, do you have another 850+ carb to swap on and see how that works ?

    EGT's can be nice but don't always tell you what to try next. I suggest to keep reading plugs especially with a light and magnifying glass to make sure there are no tiny and shiny aluminum specs (from your pistons!) showing up on it.

    If anyone's interested in the cam specs to give an idea of this motor:
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	compxr292r.jpg 
Views:	52 
Size:	87.4 KB 
ID:	8620  

  11. #9
    cfm
    cfm is offline
    Banned
    Join Date
    Jan 2008
    Posts
    1,263

    Default

    Quote Originally Posted by Canuc View Post
    this is just a 600 hp 516 unleaded
    Not too many times I here someone sandbagging on a forum. Like your style.

    Then again, are you running at higher elevation ? If so, what ?

  12. #10
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    I have found that mechanical advance is not my friend. Locked the distributor and set it at 32 (bbc 496) major difference. At anything below 33-3500.. well lets just say I didnt need to start the bbq. That carb needs to go. Jets that big are for alc. lol
    Last edited by 71hallett; 05-16-2008 at 05:13 AM.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  13. #11
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    Quote Originally Posted by cfm View Post
    Not too many times I here someone sandbagging on a forum. Like your style.

    Then again, are you running at higher elevation ? If so, what ?
    I was kinda thinking that if it didnt make 675 ish it should be put on the bottom of the river with those parts.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  14. #12
    northern member Canuc's Avatar
    Join Date
    Jan 2008
    Location
    Nechako
    Posts
    602

    Default

    Quote Originally Posted by cfm View Post
    Not too many times I here someone sandbagging on a forum. Like your style.

    Then again, are you running at higher elevation ? If so, what ?
    ya should of mentioned that were at 1800' , RCB19 907 on pump wow very nice! we get 91 from a bulk agent who gets it direct from the local refinery in town so far it's been reliable but other than that it's a gamble what your getting . cfm comp. calculated at 10.1:1 using specified comb. and dome volumes with measured quench clearance . thats the cam but it was ordered with a 112*LCA to flatten the torque curve . carb is new have had it apart and looks ok and the distribution is even but what warp said 3-5 sizes bigger on the jets for pump gas has always been enough . have a 1050 holley that we could try but that's not what the boat owner wants to hear. thanks for the feedback guys will update you after the next time out . Rick

  15. #13
    Cantard 71hallett's Avatar
    Join Date
    Mar 2008
    Location
    snow bank
    Posts
    5,017

    Default

    Quote Originally Posted by Canuc View Post
    ya should of mentioned that were at 1800' , RCB19 907 on pump wow very nice! we get 91 from a bulk agent who gets it direct from the local refinery in town so far it's been reliable but other than that it's a gamble what your getting . cfm comp. calculated at 10.1:1 using specified comb. and dome volumes with measured quench clearance . thats the cam but it was ordered with a 112*LCA to flatten the torque curve . carb is new have had it apart and looks ok and the distribution is even but what warp said 3-5 sizes bigger on the jets for pump gas has always been enough . have a 1050 holley that we could try but that's not what the boat owner wants to hear. thanks for the feedback guys will update you after the next time out . Rick
    Wasnt trying to be an ass, it just drives me crazy when using jets that big because it is normaly covering up a fuel issues or under carbed badly. One of my customers has almost a twin motor to yours and he was running an 850 race demon. I made him put on the dominator and car instantly picked up 1/2 a second and 8 mph. Went from 98 jets to 83. Runs much cleaner. By looking at were you are having trouble seems at lower rpm were it is prob real rich then at the top prob almost goin lean but just cant get enought out of the carb.
    Last edited by 71hallett; 05-17-2008 at 04:43 AM.
    Quote Originally Posted by gn7 View Post
    It would be a balmy 85* in Steel's shop if he would move a little faster

  16. #14
    northern member Canuc's Avatar
    Join Date
    Jan 2008
    Location
    Nechako
    Posts
    602

    Default

    71hallett , no i didn't take you serious so it's all good . were actually happy with the power , on a dyno with a bigger carb it might pull 675 ? but i've found from tuning in a boat and looking at the impeller charts there not as generous , teaches you to build for torque . the guy has a history of flat footing everything to death so he bought the 850 thinking it would limit the top end while still making around 600 hp. btw advance is locked out . anymore ideas i'm all ears sounds like your doing a lot of similar stuff to what we are , how's your 8-71 coming along ?did the impeller and helped with the tune-up on one couple years back 433bbc A-B Aggressor impeller @ 6000 with 8lb's boost. be good to hear from more 500 to 700 hp guys must be a ton out there .

+ Reply to Thread
Page 1 of 2 1 2 LastLast

Quick Reply Quick Reply

Register Now

Please enter the name by which you would like to log-in and be known on this site.

Please enter a password for your user account. Note that passwords are case-sensitive.

Please enter a valid email address for yourself.

Please select your insurance company (Optional)

Log-in

Tags for this Thread

Digg This Thread

Posting Permissions

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95