One for the Carb Guru's
10-10-2011, 03:49 PM
#1
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One for the Carb Guru's
Engine: 540 cid, cam:237/242dur, carb:1050 Dominator (model 8082, 2-circuit), Dart single plane intake, fuel pressure 7 psi through elect fuel pump
Ok, I rigged up a wideband O2 sensor to jet the carb. Ended up with 88's pri, with 4.5 PV, 90's sec, 3.5 PV
A/F ratio looks like this:
1000 13
1500 11
2000 11
2500 11
3000 12
3500 12.6
4000 12.8
4500 13.2
5000 13.0
5500 13.0
So, the question is. How do I get the a/f leaner from 1-3K. Is my pv too large in number??
How do the other numbers look?
Ok, I rigged up a wideband O2 sensor to jet the carb. Ended up with 88's pri, with 4.5 PV, 90's sec, 3.5 PV
A/F ratio looks like this:
1000 13
1500 11
2000 11
2500 11
3000 12
3500 12.6
4000 12.8
4500 13.2
5000 13.0
5500 13.0
So, the question is. How do I get the a/f leaner from 1-3K. Is my pv too large in number??
How do the other numbers look?
Charter Member
10-11-2011, 08:28 AM
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I agree....way lean.
Having spent my summer w/my Fast 02 meter tuning here's where I started.
1. Have someone look down your carb as you move the throttles forward (MOTOR OFF!!). Take a piece of tape an marker to mark when the secondaries start opening. So when your running you know to tune primary or secondary jetting.
2. Do you have a vacuum/boost gauge? if not get one you will need it for tuning the power valve (http://www.youtube.com/watch?v=6vKlAnKdcB4)
Having spent my summer w/my Fast 02 meter tuning here's where I started.
1. Have someone look down your carb as you move the throttles forward (MOTOR OFF!!). Take a piece of tape an marker to mark when the secondaries start opening. So when your running you know to tune primary or secondary jetting.
2. Do you have a vacuum/boost gauge? if not get one you will need it for tuning the power valve (http://www.youtube.com/watch?v=6vKlAnKdcB4)
10-11-2011, 02:19 PM
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iTrader: (1)
I agree. Using the vac guage can tell you when you need more fuel or not. IE: Heavy vs light load.
Aren't you planing from 1500-3000rpm ? If so, you need a little richer A/F ratios then cruise A/F ratios.
Heavier the load more you want to be on the rich side.
You may find out by the way your boat runs (load vs rpm vs AF ratio) that going to 1 PV and more of a spread P to S you may get it the way you want it.
============================
Just conjecture above of course. You need to load vs rpm vs AF first.
Aren't you planing from 1500-3000rpm ? If so, you need a little richer A/F ratios then cruise A/F ratios.
Heavier the load more you want to be on the rich side.
You may find out by the way your boat runs (load vs rpm vs AF ratio) that going to 1 PV and more of a spread P to S you may get it the way you want it.
============================
Just conjecture above of course. You need to load vs rpm vs AF first.
10-11-2011, 05:42 PM
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more testing
Ok, I went out today and did some more testing.
Increased secondaries to 92's. It brought the WOT a/f ratio numbers down into the 12.2-12.7 range. The motor sounds better (like I know what better sounds like). It just sounds safer if that makes any sense. Not so loud.
Top speed was pretty much the same. I tried a different prop today. Went with a Turbo 3 blade 26p. Turning it at 5400 doing 82.5 gps.
Increased secondaries to 92's. It brought the WOT a/f ratio numbers down into the 12.2-12.7 range. The motor sounds better (like I know what better sounds like). It just sounds safer if that makes any sense. Not so loud.
Top speed was pretty much the same. I tried a different prop today. Went with a Turbo 3 blade 26p. Turning it at 5400 doing 82.5 gps.
10-12-2011, 08:27 AM
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Your running too much main jet and the high speed air bleeds are to big. Leave the rear power valve in with soft progressive linkage or change the to progressive linkage. You need a vacuum gauge to dial power valves in. A/F ratios 14.3 to 13.6 cruise, best power is 13.1, heavy acceleration 11.8. The idle will be 15.1 in gear and 12.5 out of gear. Power valves should be half of what idle vacuum reads to start with. Make sure your timing is correct!!!
10-12-2011, 10:25 PM
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Your running too much main jet and the high speed air bleeds are to big. Leave the rear power valve in with soft progressive linkage or change the to progressive linkage. You need a vacuum gauge to dial power valves in. A/F ratios 14.3 to 13.6 cruise, best power is 13.1, heavy acceleration 11.8. The idle will be 15.1 in gear and 12.5 out of gear. Power valves should be half of what idle vacuum reads to start with. Make sure your timing is correct!!!
