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 Fuel curve shaping 
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
G,day,
Had a recent post in regards leaning out in top gear, think we have got on top of that .
Put in some nicer needle and seats and got rid of the vent whistle from under the float! bumped the fuel pressure up slightly.
Car has picked up .03 and 1 mph in virtually identical air , has picked up at every increment.
My questions relate to going slightly leaner straight after the gearshift, then you watch it pull gradually down rich.
How do you get rid of that initial lean area after the gearshift?
I come across some old stuff from Shrinker ( used to talk to him every few months to say hello, he was a good friend of one of my work colleagues)
He mentioned going lean after the shift and what I think I took from it was to reduce the size of the top e holes, not sure if I understood it properly or not?
Any thoughts? or worth trying to sort out?
I have some genuine old holley alcohol metering blocks off a 9645 carb and I see the 2 holes line up with my top and third hole and they are 28 thou id.
Didn't get a chance to put the flute on it as only got two passes before getting rained out.
Need to go to the next meeting basically ready to go as want to gain prediction data for the following weekend of racing.

Thanks very much!
Paul


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Fri May 19, 2017 8:36 pm
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
G,day ,
Any suggestions on this one?
Thanks in advance!

Hey Mark,
Another one if you don,t mind.
The quickfuel fuel chute bowls are they available with that black diamond coating and is it ok with alcohol?
Haven't been able to see them listed seperately.
Cheers
Paul


Tue May 23, 2017 5:42 am
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Joined: Sun Oct 23, 2016 5:52 pm
Posts: 138
Location: Canada
I have a theory. The angle of the fuel in the secondary bowl upon gear shift, or any rapid forward motion, can't only affect fuel running away from secondary jets out back. Depending on how hard it shifts, on how much g-force there is initially with each shift, the second e-holes down from the top with that black block might not be submerged in fuel anymore at that time, making for two (instead of one with the bowl having correct float/fuel level set (or maybe none of the e-holes are submerged...)) for each barrel then admitting "emulsion" air... but then again submerged with fuel level after the initial gear-change leap forward... if my thinking is correct, but it's somewhat cloudy to me whether extra or too much emulsion air creates initial richness or leanness with your circumstances... ? ... and something (something I see mentioned often enough around here, returning to using only the old school positions like your block on the left) to try might be to use the top and third e-hole positions only, blocking the second and fourth e-hole positions...

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Mike

1986 Mustang convertible. Originally 3.8L V6 with EEC-IV CFI.
Now has a Holley List-4412-2, and averages 34 (28 US) MPG.
If you're ever bored - some narrow band O2 tuning video of this thing:
http://www.youtube.com/channel/UC9glRIa3jAAtNhaXfg_cZXQ


Tue May 23, 2017 11:37 am
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Joined: Fri May 20, 2016 5:18 am
Posts: 117
Go in on YouTube BLP N&S and look at the video Jmark put up there and se how the float level in sec bowl instantly up on launch changing to a 45 degree angel


Tue May 23, 2017 12:43 pm
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Joined: Fri May 20, 2016 5:18 am
Posts: 117
Just looked to it again and it actually is a lot more than 45 degree at launch


Tue May 23, 2017 12:47 pm
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Joined: Sat Jun 01, 2013 8:02 pm
Posts: 390
These are 2 runs with different emulsions, one is 028x028x027 with a .029 bleed
other is .0225x.019x.018 with a .026 bleed, you can see how i'm lean til into high gear in second pic.
I went back to the smaller emulsions which by the way equal 2 .028's in area like factory Holley
Blocks with 2, Haven't been back to track yet since my change back


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74 Firebird 3600 lbs
9.95 @134.32 1.370 60 ft
Tue May 23, 2017 2:33 pm
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
Gday
Thanks for the info!
.good to look at those graphs for sure, what is the go with the rpm section of the graph?
Is the track very loose, lot of wheel spin?
Interesting on that 2nd graph staying lean untill the next gear, doesnt seem to be any black and white in this stuff!☺
Which picture has which bleed setup?
Cheers
Paul


Tue May 23, 2017 8:12 pm
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Joined: Fri Feb 08, 2013 5:50 pm
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Try putting .026 in the top and 3rd position. And lower your idle feed.


Tue May 23, 2017 9:59 pm
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Joined: Sat Jun 01, 2013 8:02 pm
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tuffxf wrote:
Gday
Thanks for the info!
.good to look at those graphs for sure, what is the go with the rpm section of the graph?
Is the track very loose, lot of wheel spin?
Interesting on that 2nd graph staying lean untill the next gear, doesnt seem to be any black and white in this stuff!☺
Which picture has which bleed setup?
Cheers
Paul



2nd pic was the bigger emulsion setup... i've always had issues with this rpm converter on my LM1 not being real smooth

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74 Firebird 3600 lbs
9.95 @134.32 1.370 60 ft


Tue May 23, 2017 10:05 pm
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Joined: Tue Aug 20, 2013 3:22 am
Posts: 32
jmarkaudio wrote:
Try putting .026 in the top and 3rd position. And lower your idle feed.


Gday Mark,
If this reply is to me, thanks very much!
.026 in 1 and 3, rest blocked i take it?
Leave the hi speed alone eh?
So when relocating the ifr simply tap the block and relocate it?

Do you happen to know anything about the availability of those quick fuel bowls?

Thanks very much!☺


Tue May 23, 2017 11:33 pm
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