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 Afr leaning out in top gear 
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
G,day,
Put this on speedtalk and tuner sent me a picture of his flute like bowl vent which i'll make up and fit.
Thought I'd post this here as well in case anyone see's anything obviously wrong.

Drag car on methanol, belt drive pump, clevo engine.
Afrs are good in low and 2nd gear - 3 rd gear leaner .
2nd gear is 12.8 - 13.0, 3rd is 13.4 - 13.8, 14.0 range.
Doesnt go progressively leaner it is almost fairly flat.
Fuel pressure is fairly flat at around 9 psi, 150 tbou needles, apd methanol 750.
I have a forward facing hornet style scoop, k and n 14 x 5 air cleaner with a solid top, base of air cleaner sealed to bonnet.
I have a rubber hose between tbe bowl vents with a cut out at the top.
Was thinking it was something to do with the install in the car / scoop?
Complete fuel system with engine on engine dyno no issues with fuel system or afrs.
Any ideas?
thanks very much!
Paul


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Tue Apr 25, 2017 12:55 am
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
G,day,
A pic of the data logger info, afr is the blue line in the bottom half of the photo.
Fuel pressure is constant through out the pass as with the engine dyno.
Cheers
Paul


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Tue Apr 25, 2017 12:58 am
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Joined: Mon Oct 21, 2013 12:15 am
Posts: 226
Location: San Diego, CA
If you had no issues on the dyno, I would try a thin piece of aluminum between the lid and the base, that wraps around the front of the air cleaner element. No more than the width of the carburetor itself.


Tue Apr 25, 2017 10:57 am
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Joined: Thu May 08, 2014 7:47 pm
Posts: 234
Can you tell us anything about the calibration?


Tue Apr 25, 2017 4:42 pm
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
G,day,
Thanks for the replys!
Not sure what you mean about calibration, I have a wego 3 that Ive done the free air calibration, I'm using the 0-5v output from that to input into the rpm performance DL10.
I thought it was working ok as the numbers in low gear are fat ( always are ) 2nd gear are pretty right.
Cheers
Paul


Tue Apr 25, 2017 5:29 pm
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Joined: Thu May 08, 2014 7:47 pm
Posts: 234
Basic calibration information would be what the jetting, air bleeds, squirters, power valve's, and any other information you can give in regards to the emulsion stack used, the blocks have a lot to do with it, and how the are set up.


Wed Apr 26, 2017 7:19 am
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
Yeah ok got it!
Away for work at present, have it mapped out and written down at home but not on me.
Be home in around a week.
Thanks!
Paul


Wed Apr 26, 2017 7:53 am
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Joined: Tue Jul 30, 2013 1:48 am
Posts: 29
Not sure how helpful this is but I read a post somewhere that mentioned choke horn milled main bodies don't seem to suffer the same turbulence as the chokeless contoured type and a divider between primary and secondary was useful.

I've never tried the above but slowing/stopping the spillover from primary to secondary when the air through the scoop is hitting the front of the carburettor does have merit (to me anyway) but I'd be dealing with airflow around the filter first as others have suggested.


Fri Apr 28, 2017 2:12 am
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
Gday,
Thanks for the replys! Have attached the calibration paperwork when I measured it.
I am wondering if it simply isnt running out of fuel as even though on the engine dyno the fuel curve is flat the dyno pull doesn't go for long?
Even though fuel psi in the car is fine is the bowl running out of fuel due to the nèdle and seat being a restriction?
A couple of things i noticed from where i run the car last was it wanting to die after the burnout never done that before.
Also next day when i pulled the bowls off i found the front vent whistle sitting under the float.
Now i cant say for sure if i didnt mess up fitting it last time or it has fallen out.
If it had fallen out when i seperated the bowl and block you would think it would fall on the floor.
If it was under the float during the pass it would have been hindering float drop?
With a 150 thou holley tit needle and seat how much fuel pressure is required to make 670 hp
Was thinking of going to the braswell floats and a 164/166 blp needle and seats?
Thanks very much!
Paul


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Fri Apr 28, 2017 6:33 am
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Joined: Wed Apr 03, 2013 8:06 pm
Posts: 169
I see a lot of O2 traces that look similar to that. Almost always richer in low gear, then leaner after the shift. I think some of it is the pump shot, then some fuel slosh in the bowls, and maybe the drop in rpms. What jets are in the carb, and have you tried going up on the jet size at all?
Going down on the HSAB might be worth a try. With MY O2, in MY car, it makes more power running richer than YOUR O2 is showing. As rich as low 12's on the gas scale. I don't think you have a fuel delivery issue with .150 N/S and belt drive @ 9psi, although the belt drive pump does make it easier to run the larger N/S, because you can keep the pressure low at idle. And you would likely want to drop the pressure at WOT as well if you switch.


Fri Apr 28, 2017 3:24 pm
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