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AFR does affect idle RPM, suprised!
#1103880
10/29/11 10:35 PM
10/29/11 10:35 PM
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Joined: Aug 2003
Posts: 43,190
Bend,OR USA
Cab_Burge
OP
I Win
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OP
I Win
Joined: Aug 2003
Posts: 43,190
Bend,OR USA
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I learned something new today, the AFR can and did affect the idle RPM by changing the AFR from 13.8 to 14.5 and then leaned out to 16.8 to 17.5 AFR. I had the motor idling around 1200 RPM when it was at 16.8 AFR so I enrichened the idle mixture screws one full turn which brought the AFR down to 13.5 to 14.3 or so, it also dropped the idle RPM 150 to 200 RPM  down to 950 to 1000 RPM  I was testing and setting up a new to me HP 9375-2 Dominator so I could drive the car, this carb. fought me all the way, leaking, flooding and not working properly at all  I whupped it though  Now if it will run as good as the old one I will be a happy camper, and carb tester 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: AFR does affect idle RPM, suprised!
[Re: Dragula]
#1103883
11/01/11 03:32 AM
11/01/11 03:32 AM
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Joined: Jan 2003
Posts: 4,448
Phoenix, AZ
MoparBilly
master
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master
Joined: Jan 2003
Posts: 4,448
Phoenix, AZ
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Vacuum?? AFR?? You guys are making my head hurt.
Let go at the first flash of yellow,
add fuel between rounds...that's enough to remember right there!!!
"Livin' in a powder keg and givin' off sparks"
4 Street cars, 5 Race engines
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Re: AFR does affect idle RPM, suprised!
[Re: MoparBilly]
#1103884
11/01/11 03:38 AM
11/01/11 03:38 AM
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Joined: Dec 2006
Posts: 3,667
Arizona
Chris'sBarracuda
master
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master
Joined: Dec 2006
Posts: 3,667
Arizona
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Quote:
Vacuum?? AFR?? You guys are making my head hurt.
Let go at the first flash of yellow,
add fuel between rounds...that's enough to remember right there!!!
 
Chris.. 
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Re: AFR does affect idle RPM, suprised!
[Re: Dragula]
#1103886
11/01/11 11:35 AM
11/01/11 11:35 AM
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Joined: Jan 2003
Posts: 4,448
Phoenix, AZ
MoparBilly
master
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master
Joined: Jan 2003
Posts: 4,448
Phoenix, AZ
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Dragula,
Was talking with an extremely successfull racer last weekend who has a reputation for his meticulous approach.
He mentioned converting one of his cars to E85. We questioned whether the stuff at the pump was consistant. He told us he bought 2 separate meters, buys E98 and mixes his own to get consistant E85! He stated the pump stuff generally tests out at 86-88. So I have little doubt that you are correct about dealing with the E10.
"Livin' in a powder keg and givin' off sparks"
4 Street cars, 5 Race engines
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Re: AFR does affect idle RPM, suprised!
[Re: joedust451]
#1103890
11/01/11 09:50 PM
11/01/11 09:50 PM
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Joined: Aug 2003
Posts: 43,190
Bend,OR USA
Cab_Burge
OP
I Win
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OP
I Win
Joined: Aug 2003
Posts: 43,190
Bend,OR USA
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Quote:
Cab, you didn't know that . Do you have that much time on yours hands
Anytime you change the IFR in the idle it will affect the RPM
I didn't change the idle fuel restrictors, I changed the air fuel ratio by adjusting the idle mixture screws. I have been able to slow a motor idle RPM down by adjusting the idle mixture in (leaner) and I have been able to make them richer with the idle mixture screws  This is the first motor and carb. that I can remember speeding up the RPM by making it leaner from 13,8 or so to 16.3+ AFR  I have seen the idle vacume go up with RPM going up, but not change if the RPM didn't change
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103891
11/01/11 11:16 PM
11/01/11 11:16 PM
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Joined: Jun 2003
Posts: 9,225
Charleston
sixpackgut
Drag Week Mod Champion
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Drag Week Mod Champion
Joined: Jun 2003
Posts: 9,225
Charleston
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does it idle better fatter or did it idle better leaner?
Gen 3 power 6.22@110, 9.85@135
Follow @g3hemiswap on instagram
performance only racing, CRT, ultimate converter, superior design concepts, ThumperCarbs
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103893
11/02/11 01:16 AM
11/02/11 01:16 AM
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Joined: Jan 2003
Posts: 2,309
Tomorrow.
Damned67
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,309
Tomorrow.
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Quote:
Quote:
does it idle better fatter or did it idle better leaner?
It sped up when I leaned it down, I liked it better It started to stink at 14.2 to 14.8 AFR The other carbs and motors I have had in the car with this dual wideban (Innovate) idled fine at 14.3 to 15.3 and din't stink
When was the last time you calibrated the meter?
I think mines due, as my plugs indicate a richer mix than the meter is showing.
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103894
11/02/11 01:22 AM
11/02/11 01:22 AM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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Cab, normally, well in all cases, IF your idle is on the righer end, leaning it out will raise the idle, once you get to that sweet spot where you get the highest vacuum, you will get the highest idle, going too lean will effect the idle also, so if the idle came up as you "leaned" it out it was too rich to begin with. IMO the best AFR for idle/cruise is in the mid-upper 13s, best WOT is 12.6-12.8, 14s is better for fuel economy, but might feel abit lazy over mid-upper 13s in a perf. engine.
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Re: AFR does affect idle RPM, suprised!
[Re: Damned67]
#1103895
11/02/11 01:23 AM
11/02/11 01:23 AM
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Joined: Aug 2003
Posts: 43,190
Bend,OR USA
Cab_Burge
OP
I Win
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OP
I Win
Joined: Aug 2003
Posts: 43,190
Bend,OR USA
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Quote:
Quote:
Quote:
does it idle better fatter or did it idle better leaner?
It sped up when I leaned it down, I liked it better It started to stink at 14.2 to 14.8 AFR The other carbs and motors I have had in the car with this dual wideban (Innovate) idled fine at 14.3 to 15.3 and din't stink
When was the last time you calibrated the meter?
I think mines due, as my plugs indicate a richer mix than the meter is showing.
I just calibrated both sides two months ago before going to the bracket finals, probally around twenty runs and 8 to 10 street miles, all on unleaded non ethanol 93 octane Oregon pump gas Four different carbs and a bunch of jet channging also in that time  I can't leave a good thing alone 
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103896
11/02/11 01:25 AM
11/02/11 01:25 AM
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Joined: Feb 2005
Posts: 5,221
Branson, Mo.
joedust451
super gas
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super gas
Joined: Feb 2005
Posts: 5,221
Branson, Mo.
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Quote:
Quote:
Cab, you didn't know that . Do you have that much time on yours hands
Anytime you change the IFR in the idle it will affect the RPM
I didn't change the idle fuel restrictors, I changed the air fuel ratio by adjusting the idle mixture screws. I have been able to slow a motor idle RPM down by adjusting the idle mixture in (leaner) and I have been able to make them richer with the idle mixture screws This is the first motor and carb. that I can remember speeding up the RPM by making it leaner from 13,8 or so to 16.3+ AFR I have seen the idle vacume go up with RPM going up, but not change if the RPM didn't change
Sorry Cab, I ment AFR my badd
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103897
11/02/11 10:30 AM
11/02/11 10:30 AM
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Joined: Jun 2003
Posts: 9,225
Charleston
sixpackgut
Drag Week Mod Champion
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Drag Week Mod Champion
Joined: Jun 2003
Posts: 9,225
Charleston
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Quote:
Quote:
does it idle better fatter or did it idle better leaner?
It sped up when I leaned it down, I liked it better It started to stink at 14.2 to 14.8 AFR The other carbs and motors I have had in the car with this dual wideban (Innovate) idled fine at 14.3 to 15.3 and din't stink
FWIW, my idle afr is almost 17-1. i dont know why nor do i care, thats where it works best. when cruising and everything else its spot on but idling its just doesnt seem to either read right or thats what it likes and i dont and cant find any exhaust leaks or anything like that
Gen 3 power 6.22@110, 9.85@135
Follow @g3hemiswap on instagram
performance only racing, CRT, ultimate converter, superior design concepts, ThumperCarbs
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103898
11/02/11 11:47 AM
11/02/11 11:47 AM
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Joined: Jan 2003
Posts: 642
New Jersey
Craig
mopar
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mopar
Joined: Jan 2003
Posts: 642
New Jersey
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CAB, if this is an automatic trans, was your idle mix testing in park or in gear? I have found that the idle mix that gives the highest idle rpm in park is often not the same setting for in gear. I prefer a solid idle in gear to prevent loading up or stalling at a light.
67 Dart, 426 Hemi, 9.23/145mph, 3400lbs, footbraked, owned since 1982
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Re: AFR does affect idle RPM, suprised!
[Re: Cab_Burge]
#1103899
11/02/11 12:13 PM
11/02/11 12:13 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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I dont use the A/F meter to set the idle... I get it to where it idles the best in N and in gear... then if I feel like I want to know what the A/F ratio is then I put the meter on it 
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