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 Post subject: blow through car ideas
PostPosted: Sat Mar 22, 2008 10:01 am 
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330ft
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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

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Posted: Sat Mar 22, 2008 9:21 pm 


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 Post subject: Re: blow through car ideas
PostPosted: Sat Mar 22, 2008 9:21 pm 
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60ft

Joined: Thu Feb 28, 2008 2:50 pm
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With closed or mostly closed trottle blades, there is low flow past the booster, whether or not your forcing air into the carb, also the pressure differential (across the booster)is nill, if your getting too much fuel, it's not coming from the boosters. Wacking the throttle open will cause real problems, all that pressurized air is gonna accelerate faster than normal, making accelerator pump shot critical (and LARGE). A given size engine is only going to ingest a certain amount of air , under light loads, closed throttle blades, boost should be low then anyway , so the tune for part throttle should be close to normal.(but on the fat side) Unfortunatlly , power valves open on low pressure , so that's not going to help, the easy way out would be square jet it, block the power valve, and tune the heck out of the accelerater pump

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 Post subject: Re: blow through car ideas
PostPosted: Sun Mar 23, 2008 9:55 pm 
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330ft
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Quote:
the easy way out would be fuel injection
:lol:

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 Post subject: Re: blow through car ideas
PostPosted: Tue Mar 25, 2008 9:08 am 
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330ft

Joined: Thu Feb 28, 2008 9:45 am
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Gameracing wrote:
With closed or mostly closed trottle blades, there is low flow past the booster, whether or not your forcing air into the carb, also the pressure differential (across the booster)is nill, if your getting too much fuel, it's not coming from the boosters. Wacking the throttle open will cause real problems, all that pressurized air is gonna accelerate faster than normal, making accelerator pump shot critical (and LARGE). A given size engine is only going to ingest a certain amount of air , under light loads, closed throttle blades, boost should be low then anyway , so the tune for part throttle should be close to normal.(but on the fat side) Unfortunatlly , power valves open on low pressure , so that's not going to help, the easy way out would be square jet it, block the power valve, and tune the heck out of the accelerater pump



Why not use boost referenced power valves. You can adjust them so they open at whatever boost you would like.

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 Post subject: Re: blow through car ideas
PostPosted: Wed Mar 26, 2008 3:27 pm 
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go blow thru or dont go at all :).

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 Post subject: Re: blow through car ideas
PostPosted: Mon Nov 03, 2008 11:04 am 
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Renting Helmet

Joined: Mon Nov 03, 2008 11:00 am
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I wish some one would come out with a BRPV that could be purchased seperately. :)


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