Help tuning carbs with a wideband a/f gauge on a blower motor
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Help tuning carbs with a wideband a/f gauge on a blower motor

  1. #1
    Thrasher187 Steve Slostad's Avatar
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    Default Help tuning carbs with a wideband a/f gauge on a blower motor

    I installed a Innovate wideband O2 gauge and it did not come with any "tuning" suggestions. I Got some good info from my old thread "Teague 509 blower motor jetting. Where to start suggestions? I'm real lean" I would like to know more about what is a safe WOT A/F reading for poker run type driving. There is a stretch of river by my house that is about 15 miles long and I want to jet to be able to hammer it through there. and not melt down my motor. As well as what A/F range is good for idling, and cruising around 55 mph. I have a 28 Daytona with the teague 509, Merlin iron block, Brodix 2x aluminum heads, Bravo xr 135 gearing ,28 pitch prop. I added a new Weiand 8:71 with a superchiller and brand new Holley 750 blower carbs running 34 deg finish timing, 5 pounds of boost.
    Last edited by Steve Slostad; 08-10-2013 at 09:05 AM.
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    gn7
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    Shoot for for 11.5 at WOT. You can worry about the other throttle opening AFR later. First you have to get the WOT where it belongs and work back to the rest. Is this thing square jetting now, or do you still have the PVs in it? If so, which ones?



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    Senior Member Hass828's Avatar
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    Quote Originally Posted by gn7 View Post
    Shoot for for 11.5 at WOT. You can worry about the other throttle opening AFR later. First you have to get the WOT where it belongs and work back to the rest. Is this thing square jetting now, or do you still have the PVs in it? If so, which ones?
    correct, then it would be nice to see around 13-1 @ cruise rpm and 14-1 to 14.5-1 at idle.
    But with no power valves you will probably have to live with a richer cruise a/f than what I stated.
    "if we keep doing it the same way we always do..we will always get the same results"
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    gn7
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    Quote Originally Posted by Hass828 View Post
    correct, then it would be nice to see around 13-1 @ cruise rpm and 14-1 to 14.5-1 at idle.
    But with no power valves you will probably have to live with a richer cruise a/f than what I stated.
    Who said no power valves. Baby steps Hass, baby steps.
    But I will say, it doesn't take much to open them if the boat is big enough.



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    Senior Member Hass828's Avatar
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    Quote Originally Posted by gn7 View Post
    Who said no power valves. Baby steps Hass, baby steps.
    But I will say, it doesn't take much to open them if the boat is big enough.
    You did!
    Quote Originally Posted by gn7 View Post
    I don't disagree with any of this. Its very sound advice. I just got the feeling that the OP saw 1300 and shut it down in a panic without ever really driving it to see where it settled out at. Jetting seems way out there. I agree, I would jack in a few more degrees of timing. Late timing will send the EGTs thru the roof.
    Personally I would dump the PVs and deal with them later once I got the thing where I wanted it at WOT MAX RPM full boost. Then back into the PV tune.
    Putting 80s in the primaries and dropping the PVs to 2.5 wasn't helping his cause. Doesn't matter once its in boost, but the 2.5 sure isn't helping the lean AF when its not in boost.

    I wouldn't be one bit shy about putting 33-34* in that thing. You cas throw all the fuel you want at the thing, and the exhaust temps are just going to go up and up if the timing isn't there.

    Ibet I could square jet that thing to match Holleys original 86 in the secondaries, (maybe 88 square)leave out the PVs, set the timing at 34 and the thing would be almost dead nuts. Just wild ass guess.
    You already know this GN, but to the OP , it will be real fat at cruise speeds if you dial in the wfo a/f ratio without powervalves. So as GN has stated, you will certainly want to back into the tune including adding the powervalves back into the equasion(if you can make use of them). Esp with that kind of boat, but depending on just how high your "cruise speed" is and just how much load the engine is under, the powervalves may be open all the time anyway. If this is the case then might as well do away with them. A vacuum guage will be a good tuning tool to take along during tuning.
    Last edited by Hass828; 07-02-2013 at 07:39 PM.
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    Thrasher187 Steve Slostad's Avatar
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    I am going to try the 2.5 PVs first. I have been rich at idle all along. I was battling What I thought was a lean condition as soon as I started getting on it. Whenever I did get on it and I got into boost is when it started getting hot by the EGT reading. The idle has always been ok. I am going to try the stock jetting the carbs came with and go from there. I now know I was not as lean as I thought I was. If things get confusing I will ditch the PVs and jet it square. I am pretty confident it will be okay with the correct PVs for the 6 lbs of vacuum I have. I hope this does not frustrate you GN7 as I really value the time you have spent helping me. Remember, I was chasing a problem that did not exist with my inability to correctly read the spark plugs. I have a vacuum/ boost gauge in the dash.
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    Senior Member Skydog's Avatar
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    32 timming should help cool down egts. I went square on my boat runs great everywhere!!! Sure little fat down low but other than the wideband telling me that I would never know!! GN7 rocks yes :-) :-) :-)
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    Senior Member MACHINEHEAD1's Avatar
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    Idle afr means nothing. If you rap the throttle to 4k and back to idle and it dies its to lean. If it doesnt die try holding it at 4k for 3 seconds and slap the throttle shut. If it dies its too lean. Keep cranking idle mix till it doesnt die. It may begin to surge a little. This is for dock manners and trailer jockeying. Dont want you to kill the motor when your buddy tells you, you're on the bow stop and you pull the stick back quickly. It was on the stop but he didnt get her hooked. Now your dead and drifting of the trailer at site 6 in the wind. Just sayin. 12.0AFR is a starting point if your way out. Thing wont even stay running at 14.5 I bet.
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    Quote Originally Posted by MACHINEHEAD1 View Post
    Idle afr means nothing. If you rap the throttle to 4k and back to idle and it dies its to lean. If it doesnt die try holding it at 4k for 3 seconds and slap the throttle shut. If it dies its too lean. Keep cranking idle mix till it doesnt die. It may begin to surge a little. This is for dock manners and trailer jockeying. Dont want you to kill the motor when your buddy tells you, you're on the bow stop and you pull the stick back quickly. It was on the stop but he didnt get her hooked. Now your dead and drifting of the trailer at site 6 in the wind. Just sayin. 12.0AFR is a starting point if your way out. Thing wont even stay running at 14.5 I bet.
    Nice nice u so on about idle air afr means zero!! On my boosted sleds u set fuel to where sled is happy and put tape over the afr gauge. Great info ty!!
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  12. #10
    gn7
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    Quote Originally Posted by Steve Slostad View Post
    I am going to try the 2.5 PVs first. I have been rich at idle all along. I was battling What I thought was a lean condition as soon as I started getting on it. Whenever I did get on it and I got into boost is when it started getting hot by the EGT reading. The idle has always been ok. I am going to try the stock jetting the carbs came with and go from there. I now know I was not as lean as I thought I was. If things get confusing I will ditch the PVs and jet it square. I am pretty confident it will be okay with the correct PVs for the 6 lbs of vacuum I have. I hope this does not frustrate you GN7 as I really value the time you have spent helping me. Remember, I was chasing a problem that did not exist with my inability to correctly read the spark plugs. I have a vacuum/ boost gauge in the dash.
    No problem with starting over where Holley had them. Better than some crazy big ass jets AND PVs.
    Either one or the other, but not both. Not yet anyway.

    You are aware that the 2.5 PV will delay the enrichment from where Holley had it with the 6.5. You will still be in enrichment mode in boost, but your part throttle "in manifold vacuum" will delay the opening of the PV.

    YOU NEED, absolutley, no guessing here, YOU NEED a vacuum gauge, not your boost/vac gauge in the dash. but an honest to gawd 4-5" vacuum gauge from the auto store, hooked up to the manifold, or you are pissing in the wind when it comes time to pick and chose a PV.
    You need to know the vac or boost, and RPM when watching the O2. Or you are just back to guessing again.



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    Frank my lord Blown$um's Avatar
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    Quote Originally Posted by gn7 View Post
    No problem with starting over where Holley had them. Better than some crazy big ass jets AND PVs.
    Either one or the other, but not both. Not yet anyway.

    You are aware that the 2.5 PV will delay the enrichment from where Holley had it with the 6.5. You will still be in enrichment mode in boost, but your part throttle "in manifold vacuum" will delay the opening of the PV.

    YOU NEED, absolutley, no guessing here, YOU NEED a vacuum gauge, not your boost/vac gauge in the dash. but an honest to gawd 4-5" vacuum gauge from the auto store, hooked up to the manifold, or you are pissing in the wind when it comes time to pick and chose a PV.
    You need to know the vac or boost, and RPM when watching the O2. Or you are just back to guessing again.
    Your right gn7, the guage I use is a kilopascal guage from snap on it reads very accurately vaccum and boost up to 15 lbs. I would check my vaccum referenced pv by putting a "t" in line, note readings. Then I would check a port under carbs to verify same reading. Adjust pv values from their to get correct pv"s.
    "Ill be your huckleberry"
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  14. #12
    gn7
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    Quote Originally Posted by Blown$um View Post
    Your right gn7, the guage I use is a kilopascal guage from snap on it reads very accurately vaccum and boost up to 15 lbs. I would check my vaccum referenced pv by putting a "t" in line, note readings. Then I would check a port under carbs to verify same reading. Adjust pv values from their to get correct pv"s.
    He doesn'tm really need the reading under the carbs because the carbs are referenced to the manifold, not under the carbs, But you have the right idea with the tee to a good vac gauge.



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    Frank my lord Blown$um's Avatar
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    Default Vaccum

    A lot of my testing done with wide band still showed lean conditions even with corrected pv"s in place, we ended up on this particular engine which had a locked out dizzy set at 34 degrees, and went to a dizzy not locked out and set our overall advance to 34degrees and exhaust temps came way down as it was not at full advance while just idling, or part throttle conditions when fuel system was lean the dizzy was no longer contributing to false readings.
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    Frank my lord Blown$um's Avatar
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    We checked several readings is all I'm getting at cause we noticed that even under throttle plates the severity of vaccum was still their even when engine was under boost, the size of carbs directly effect this reading, ultimately carbs are restrictor plates in them selfs, sure motor made boost but pv was never opening correctly because of this effect. So to small of carb is really a lot bigger problem than people realize.
    "Ill be your huckleberry"
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