blow through car ideas
Posted: Sat Mar 22, 2008 10:01 am
heres my therory on blow through carbs and part throttle drivablity . the booster signal is only a psi differential not a "vacume suck "
. so the higher air velocity through the carbs venturi still pulls major fuel even threw the almost closed throttle plates . a normal carb will atomize well and the boosters do a ok job in even ditribution . but the extra volume of air will require less throttle opening for a given rpm use and likly will draw most of the fuel to the front and back cyl.'s do to the throttle plate angle ramping it from the booster . when you lessen the given throttle angle for the load with preasurized air you will agravate this transition part of the fuel curve . at wide open throttle all bets are off and all should work even matched as long as you get your high speed bleed ,emulsion bleed and jet right. this is why i think that carb shops will use a anular booster in these applications to keep as much fuel flowing past the high side of the throttle angle . it would be like trying to use a 1150 dominator set up for dual carbs on a 302 w/ single plane . it will idle and run at wide open but trying to tune it will give ya a anurism !!!! heres the catch 22
if a carb sized for your actual air volume say 16 psi no inter cooler is going to net you about double your cubes of air injested then size wise a 350 would want 1200 cfm . the comprimise is how much air volume you have at part throttle v.s. a n/a motor that size . ...... that is why most peple cop out of a carb on a turbo /super charged car that must have street manners and let the fuel maps handle the load/volume delivery .
the trick is to be able to build a carb that has the cfm req. to not be a restiction and be able to evenly atomize fuel into all parts of the manifold at high psi low throttle angles .. a dog leg or straight booster is to low and a anular booster is a major flow restriction .
it seems that looking at wet flow inside a carb we need to lower the venturi and or raise the booster . still keeping the signal strenth to draw fuel . this will put us into a land not alot will travel .... ............ i would bet that a huge dominator carb with hogged out bores would serve well with a high triple booster like a q-jet and possibly a venturi draft tube for high speed enrichment .
dont get into a huff the q-jet was a extreamly efficient carb at distribution on part throttle and wide open. just tunning the caverness vacume secondarys was on a case by case bassis . ...
i think this is why some carb shops use the previous pictured high mounted draft tubes for their max cfm carbs .it still get a signal but will keep the fuel evenly spread on part throttle...
what do ya think did i hit it or miss ,????
ive been known to out think myself sometimes and be way off base
. so the higher air velocity through the carbs venturi still pulls major fuel even threw the almost closed throttle plates . a normal carb will atomize well and the boosters do a ok job in even ditribution . but the extra volume of air will require less throttle opening for a given rpm use and likly will draw most of the fuel to the front and back cyl.'s do to the throttle plate angle ramping it from the booster . when you lessen the given throttle angle for the load with preasurized air you will agravate this transition part of the fuel curve . at wide open throttle all bets are off and all should work even matched as long as you get your high speed bleed ,emulsion bleed and jet right. this is why i think that carb shops will use a anular booster in these applications to keep as much fuel flowing past the high side of the throttle angle . it would be like trying to use a 1150 dominator set up for dual carbs on a 302 w/ single plane . it will idle and run at wide open but trying to tune it will give ya a anurism !!!! heres the catch 22
if a carb sized for your actual air volume say 16 psi no inter cooler is going to net you about double your cubes of air injested then size wise a 350 would want 1200 cfm . the comprimise is how much air volume you have at part throttle v.s. a n/a motor that size . ...... that is why most peple cop out of a carb on a turbo /super charged car that must have street manners and let the fuel maps handle the load/volume delivery .
the trick is to be able to build a carb that has the cfm req. to not be a restiction and be able to evenly atomize fuel into all parts of the manifold at high psi low throttle angles .. a dog leg or straight booster is to low and a anular booster is a major flow restriction .
it seems that looking at wet flow inside a carb we need to lower the venturi and or raise the booster . still keeping the signal strenth to draw fuel . this will put us into a land not alot will travel .... ............ i would bet that a huge dominator carb with hogged out bores would serve well with a high triple booster like a q-jet and possibly a venturi draft tube for high speed enrichment .
dont get into a huff the q-jet was a extreamly efficient carb at distribution on part throttle and wide open. just tunning the caverness vacume secondarys was on a case by case bassis . ...
i think this is why some carb shops use the previous pictured high mounted draft tubes for their max cfm carbs .it still get a signal but will keep the fuel evenly spread on part throttle...
what do ya think did i hit it or miss ,????
ive been known to out think myself sometimes and be way off base
.