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Discussion Starter #1
ok screwing around with my data logger tonight. i have a boost gauge from the carb hat just for reference. the gauge read 5lbs foot braking and the logger read 1.06. ive heard 2-3 difference but is 4 ok?? primaries and secondaries fully opened.

discuss.........
 

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Before I got all worked up I would log underneath the carb with the logger and then back on top of the carb with the logger to eliminate the differences in gauges.
 

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Discussion Starter #4
Havent been down the track so no real data yet. Will know this coming Saturday

Very good point on the differences between gauges. Fuel pressure says 5.5lbs and logger says 6.27lbs
 

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Typical. Ive seen 7-8.. A carb has to have that pressure differential to work....
 

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Discussion Starter #6
ok i just did a little data log. im going off fuel pressure as it come from the same fitting the boost gage does that i have in the carb hat. fuel pressure went up 3.07lbs. my boost reading was at -.23lbs so i guess when the motor sees 0.00 or begining to see positive pressure under the carb it should have 3.30lbs in the hat. that means the auto meter gauge is 1.7 lbs off lol.

so second issue is well not sure if its an issue yet but when foot braking it my o2 reading says 12.7 idle and 13.9 foot braking it. now my BRPV dont open till 5lbs so im thinking it should be ok. im worried foot braking it at 4lbs on the line that the motor is going to lean out and hurt something. am i wrong thinking this way?? also timing is still at 35* at 4lbs. dont pull any till 5lbs
 

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Wouldn't the differential pressure between abve and below the carb be dependent on flow/boost pressure, so at really low boost say 1psi there should be minimal differential pressure between above and below, but at say 15psi above the carb you may only see 10psi in the intake?
 

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Its not enough boost to.worry about it... 4 psi aint alot...and you are on c16....

I might put a jet in the secondary side in it...13.9 is a touch lean.
 

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Is it on a 2 step when your reading the foot brake air fuel. If so that is not a good reading.
 

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Discussion Starter #10
Haven't used the two step yet Tim. Just foot braking it to around 4000

John I figures as much. I plan on jetting it up. Think its going to lean out with the new changes. Wont know till I get the brpv open
 

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Discussion Starter #12
so if going down the track i still only see 4lb difference will it be hard to pull more fuel from the boosters??? maybe under full boost it will be different. slow speed with a little motor might be the issue im thinking but once the turbo lights off it might be ok. 331sbf with a 750cfm
 
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