B/v %

Many post about fuel system , talked of barrel valve % . Can somebody explain me the way to check it.
Thanks

 

barrel valve leakage

first thing to do is probaly check your butterfly clearence on your injector usually somewhere between .010 to .012 is a good starting point. typically you block off all injector inlet and return lines except for the hat nozzles then connect your leakdown gauge to barrel valve inlet. if you are using a dual gauge set the air gauge to 100 on the pressure gauge then connect the air line and read leakdown percentage on second gauge. here is a little saying to remember right is rich and left is lean. by turing the hex adjuster bar you will richen or lean your barrell valve or add more or less leakdown percentage. you can also use a single gauge which is the type we sell or as some refer to as the old sun style i think also childs and albert offer a single gauge hook it up all the same attach gauge set at 100 and then adjust link bar until desired leak down is achived. there is probaly some different variations but this should get you close.

 

Thanks rbs for your answer . it's very well explained. I want also know what is considered when you adjust bv leak % , is it the way the car react at the starting line and 0-60 feet time . Is it the same % for funny car with clutch and the car with converter an automatic trans
Thanks

 

Bonjour Claude !!!

L'explication de RBS pour ce qui est de BV% est tres precise et correct , le model de leakdown que tu utilise pour faire cette ajustement est tres important et porte a confusion. Si tu veux en parlez , envoie moi un courriel , serge_blanc@hotmail.com.

Effectivement cette ajustement peu produire un gain considérable sur la performance du temps de reaction ainsi que le 60 FT , mais tout dépend de ton FUEL SYSTEM , avez vous un DATA RECORDER sur votre voiture ???

Salut !!! Serge (du Québec)

 

Huh? Dang,and i have a hard time with english.LOL Barrel leakage is tied into idle check and butterfly clearance. If your leak is high as on a blown app (sbc around 65% to hemi around 78 to 82% alc) and your idle check is low,the idle slot can be close to closing off and cause the engine to go rich on the part throttle no load condition as in burnout and staging instead of building heat.When it does that,it will cool off the cylinders and make the engine lazy until it can get enough load on it to recover if it ever does. On the other hand ,if its too lean,it can and will back fire.You can back the leak off and increase the idle pressure to get it further away from the transition to main. You want enough idle fuel to be able to cover up the big hole when opening the throttle as their isnt any accelerator pump and not too much to milk the oil and make the engine go cold.It usually takes all 3 in balance to make it happy.

 

Sorry Leon ( for the french )

Just said to Claude to be aware of want kind of leakdown he actually use to do this setting , sometimes people get confused when they set the barrel % with the number ( say 60% leakdown )that people recommand and they end up going in the wrong direction because they do not use the same type of leakdown.( or they did not read the tool the same way)

As you probably know , 20% of leakdown is 20% , on a single gauge leakdown tester , it will indicate 20 but on a 2 gauge leakdown tester it will show 80. I agree with you about your statement and hope you understand my poor english.

Have a great Hollidays....... Serge.......

 

No thats fine. I admire someone that can talk 2 diff languages.Thats y i said what i did.

 

Leak Down % on What ????

I have an old sun tester that is from the 60's and have been leaking down barrel valves ever since. The percentage of leakdown depends on many factors, type fuel, blown or naturally asperated, staging rpm, type of clutch,
etc.etc. Just remember when setting the fuel flow at idle or for staging always err on the rich side. As stated by another racers post fuel injectors unlike carburaters have no excellator pump. Therefore you must have enough fuel either puddled in the manifold and intake runners to satisfy the engine the instant you open the big butterflies. Unless it is way lean you might think the engine sounds good and cannot visually detect it bogging. However when given more fuel flow at idle the 60 foot time will improve if the engine is a little lean on the bv adjustment. That has been my experience anyway with blow and injected nitro engines.

 

Just for discussion, we set our idle by setting the fuel flow to .9 gpm, with RacePak reading in real time, then open or close throttle blades to get 1800 rpm. Have never used leakage, but am going to check it to see what we have.

 

I wish i could afford a flow meter and a race pak. Santa....Santa,you listening?

 

Leon comented (You want enough idle fuel to be able to cover up the big hole when opening the throttle as their isnt any accelerator pump) this is at launch RPM i expect, what is your opinion on what you should do with the idle return hole in the B/V scroll. I have seen lots of them modified i.e elongated so that at launch they are still open and lots that are still standard. Any thoughts....