Re: Carb Tuning
[Re: DusterKid]
#2474745
03/31/18 03:47 AM
03/31/18 03:47 AM
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Joined: Aug 2003
Posts: 43,173 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,173
Bend,OR USA
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Last edited by Cab_Burge; 03/31/18 03:49 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Carb Tuning
[Re: DusterKid]
#2475085
03/31/18 09:56 PM
03/31/18 09:56 PM
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Joined: May 2008
Posts: 1,131 Thigh-Gap Junction
@#$%&*!
New user name, Same old jerk!
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New user name, Same old jerk!
Joined: May 2008
Posts: 1,131
Thigh-Gap Junction
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I got my Air Fuel gauge hooked up and at idle it is right at 13.3. I built the car up to 2500 rpm like I do when I launch and it goes to 10.2. ... You might just look down the throat of the carb under those conditions and see if you've got a bunch of fuel coming outta the boosters. If so, tuning on the idle/transition circuitry might not make any difference at all.
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Re: Carb Tuning
[Re: @#$%&*!]
#2475091
03/31/18 10:12 PM
03/31/18 10:12 PM
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Joined: Jan 2005
Posts: 1,772 Keymar, MD
DusterKid
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,772
Keymar, MD
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I got my Air Fuel gauge hooked up and at idle it is right at 13.3. I built the car up to 2500 rpm like I do when I launch and it goes to 10.2. ... You might just look down the throat of the carb under those conditions and see if you've got a bunch of fuel coming outta the boosters. If so, tuning on the idle/transition circuitry might not make any difference at all. I'll have to check that out. I have a reading of 12.4 at WOT
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Re: Carb Tuning
[Re: DusterKid]
#2475110
03/31/18 11:08 PM
03/31/18 11:08 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
I Live Here
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I Live Here
Joined: Jan 2004
Posts: 13,247
Mt. Vernon, Ohio
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I got my Air Fuel gauge hooked up and at idle it is right at 13.3. I built the car up to 2500 rpm like I do when I launch and it goes to 10.2. ... You might just look down the throat of the carb under those conditions and see if you've got a bunch of fuel coming outta the boosters. If so, tuning on the idle/transition circuitry might not make any difference at all. I'll have to check that out. I have a reading of 12.4 at WOT power valve in the primary? if so it may be opening too soon, you really need to map the afr to find out what it does down track, sounds like your idle isn't terrible but it fattens up with rpm,the csrb I just took off my car did the same thing and found the high speed bleed's were WAYYYY off, and I am running 88 rear and 78 front jetting with a 5.5 PV and it would tank all the way down into the upper9. to lower 10.afr range ,, seriously pig fat but the idle was 13.9 to 14.0.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: Carb Tuning
[Re: DusterKid]
#2475116
03/31/18 11:22 PM
03/31/18 11:22 PM
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Joined: Jan 2003
Posts: 19,363 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,363
Las Vegas
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Want my advice. DONT get hung up on numbers on a gauge. Pay attention to what the car is telling you about what it wants. Then look at the gauge to get a good baseline. There is NO perfect AFR that fits all cars and situations.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Carb Tuning
[Re: Al_Alguire]
#2475119
03/31/18 11:33 PM
03/31/18 11:33 PM
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Joined: Mar 2010
Posts: 632 MD-USA
Dodgeguy101
mopar
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mopar
Joined: Mar 2010
Posts: 632
MD-USA
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Want my advice. DONT get hung up on numbers on a gauge. Pay attention to what the car is telling you about what it wants. Then look at the gauge to get a good baseline. There is NO perfect AFR that fits all cars and situations. I agree, dont worry about what the idle #'s are, every engine is different.
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Re: Carb Tuning
[Re: Dodgeguy101]
#2475626
04/01/18 10:01 PM
04/01/18 10:01 PM
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Joined: Jan 2004
Posts: 13,247 Mt. Vernon, Ohio
dartman366
I Live Here
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I Live Here
Joined: Jan 2004
Posts: 13,247
Mt. Vernon, Ohio
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Want my advice. DONT get hung up on numbers on a gauge. Pay attention to what the car is telling you about what it wants. Then look at the gauge to get a good baseline. There is NO perfect AFR that fits all cars and situations. I agree, dont worry about what the idle #'s are, every engine is different. I agree also,,,,to a point, I think afr meters are like dyno's just a tool to get you close and set a baseline, then you can tweek from there, then you can tell what the car want's or don't want,, if you loose your way then you can go back to your baseline setting as long as you write all your info down, I did this to the carb I just built and have every thing in a notebook, now it's time to go out and see what the meter has to say and make my baseline from there, then start tweeking from that point. p.s.with the afr meter I found what I thought was a good running carb ended up being a slow pathetic pig and realized that somewhere along the way I had lost sight of what the car wanted.
Light travels faster than the speed of sound,,,this is why some people seem bright untill you hear them speak.
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Re: Carb Tuning
[Re: DusterKid]
#2475635
04/01/18 10:20 PM
04/01/18 10:20 PM
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Joined: Jul 2004
Posts: 19,317 State of confusion
Thumperdart
I Live Here
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I Live Here
Joined: Jul 2004
Posts: 19,317
State of confusion
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What size t-slots.........
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: Carb Tuning
[Re: DusterKid]
#2476067
04/02/18 01:30 PM
04/02/18 01:30 PM
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Joined: Jan 2003
Posts: 19,363 Las Vegas
Al_Alguire
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 19,363
Las Vegas
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One further point that often seem to go ignored in a lot of posts. Different fuels have different "target" AFR's. Pump gas(which is a blend and rarely the same season to season, ad any percentage of ethanol and its changed again) is one number, E85(another blend, 9.8-1) another, I use VP fuel and you will find that C10(14.56-1) C12(15.0-1), C25(15.07), Q16(13.6-1), C14+(15.08-1), C45(13.12) etc ALL have a different stioch number based on the fuels characteristics. Just one more reason that there is not and "ideal", one size fits all number. Not to mention things like burn rate, cooling affect, and energy value of a given fuel. Just something that seems to get left out in these conversations.
Each combo will also want different requirements to achieve best ET. Chasing an "ideal" number often is not going to be the quickest ET or best MPH. Also bear on mind when using a single O2 in a collector you are taking an average for the bank which could be biased by one or two cylinders running better or worse than others, air leaks etc. My point is don't go chasing a number thinking ok now my car is as good as its going to get. Pay attention to the old schools things as well, reading plugs, checking timing the things we have always done to tune for the BEST MPH, that will tell you when you are making the best power. Not when a gauge reads 13.7-1. Once you achieve that best MPH then look at the gauge and make note of what you are after. MPH is the ultimate determination of power not a number of a gauge. Hopefully you can have the ability to log as that will help greatly. I see so many people chasing what they believe is an ideal number on a gauge when one, they are not sure what that number should be or two paying attention to the time slip and the car.
Plenty of people here like Dom to help you get the carb tuned to work best for what you want it to do. Just don't forget all the other variables when at the track trying to achieve a goal all for the sake of a number on a gauge. I am sure Dom can lead you in the right direction for what you are after.
One last tidbit for comparisons sake. I work on 3 cars and have two of my own. NONE of them run best at their given fuels STOICH number, none of them. The heads up car runs best MPH and ET at about 1.5 points RICHER than Stoich. The dragster is best at .7 and my car work best at .9 richer. Our fuel curves are pretty flat from .5 to the end of the run on an average, generally within .1-.15 and those numbers listed Just FYI. Oh yeah on 3 of those cars we are reading 8 O2's, one on each cylinder.
"I am not ashamed to confess I am ignorant of what I do not know."
"It's never wrong to do the right thing"
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Re: Carb Tuning
[Re: Thumperdart]
#2476084
04/02/18 02:00 PM
04/02/18 02:00 PM
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Joined: Jan 2005
Posts: 1,772 Keymar, MD
DusterKid
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,772
Keymar, MD
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What size t-slots......... Not sure I'll have to check it out when I get off work. It a 850 Proform that hasn't been touch, so should be whatever they are from stock.
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Re: Carb Tuning
[Re: polyspheric]
#2476107
04/02/18 02:27 PM
04/02/18 02:27 PM
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Joined: Feb 2015
Posts: 2,075 CA
crackedback
top fuel
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top fuel
Joined: Feb 2015
Posts: 2,075
CA
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Where is your idle spark setting? That's one thing or sure the total timing people miss the boat. If it's locked out, not an issue. I was going to post idle timing and that the IFR is probably a bit too big.
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Re: Carb Tuning
[Re: DusterKid]
#2476114
04/02/18 02:34 PM
04/02/18 02:34 PM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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A lot of great advice in this thread. Al's is really well written. I agree with Cab's, and pretty much all the others too. The question I have for Dusterkid is: How interested are you in tuning? Do you just want to do jets and have fun racing; or is getting into the tuning a little bit more, or a lot more part of your agenda and enjoyment? Since you are already taking passes at the track, IMO the immediate use of the AFR gage is whether main jet changes cause the expected change in AFR, and whether the AFR stays steady from shift into top gear to end of the track. Under WOT it should flatline. Under other conditions, it can and should be different AFRs. Wideband & AFR Focus on one aspect and change just one thing at a time.
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Re: Carb Tuning
[Re: Thumperdart]
#2482346
04/13/18 10:39 PM
04/13/18 10:39 PM
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Joined: Jan 2005
Posts: 1,772 Keymar, MD
DusterKid
OP
top fuel
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OP
top fuel
Joined: Jan 2005
Posts: 1,772
Keymar, MD
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The t-slots can vary but need to be measured w bits but not just on the metering block face but underneath where the base mounts as they can and will be sized down in that location. Totally agree w/Al in that each fuel has it's burn rates and afr needs and see more power these days leaner like in the 13's and even low 14's than what was considered max power like the 12.5 range. I talked to a VP rep about the 101 unleaded I run and he said just because a fuel is oxygenated doesn't mean it needs richer afr's and my car screams in the 12.8-13.2 zone on the street and plugs look like new but not sure that translates into better et's yet...............Test and test again............. Finally measured the t slots. They are 1/8" in the metering block and are .028" wide at the base There are no emulsion bleeds installed at all. All 4 of the emulsion bleeds are open.
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