draw through VS. blow through
02-12-2003, 11:21 AM
#1
1.0 BAR
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Join Date: Feb 2003
Location: Wisconsin
Posts: 461
draw through VS. blow through
sorry guys, i went and checked out those groups on yahoo and a lot of the were complete dicks and said "don't ask noobie questions here." WTF
!!! Where the hell am i supposed to ask them then? So,here i am, back to you guys. Hopefully you can help me out. I looked at F. I. and that's way out of my price range. Big Time. I also looked at aftermarket custom carbs for pressurized systems, and that ain't much better. Also, they aren't very good at calibrating the mix. They're too rich at low boost and get lean toward the top. a draw through system would be awesome cuz all you gotta do is calibrate it for all of the extra flow, no pressure problems there. My questions are, does the fuel/air charge do damage to the turbo when it flows through? Also, would it still be possible to intercool the system? because the charge will have to run through the intecooler would that do any damage there? Right now the draw through system looks really really good, any reasons for me not to use it? Thanks guys. Josh
!!! Where the hell am i supposed to ask them then? So,here i am, back to you guys. Hopefully you can help me out. I looked at F. I. and that's way out of my price range. Big Time. I also looked at aftermarket custom carbs for pressurized systems, and that ain't much better. Also, they aren't very good at calibrating the mix. They're too rich at low boost and get lean toward the top. a draw through system would be awesome cuz all you gotta do is calibrate it for all of the extra flow, no pressure problems there. My questions are, does the fuel/air charge do damage to the turbo when it flows through? Also, would it still be possible to intercool the system? because the charge will have to run through the intecooler would that do any damage there? Right now the draw through system looks really really good, any reasons for me not to use it? Thanks guys. Josh
02-12-2003, 01:43 PM
#2
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Join Date: Dec 2002
Posts: 13,991
Re:draw through VS. blow through
like I said, I dont think many of us have delt with this stuff.. But I could be wrong... From what I have read, the draw through system does have some negitive areas, cold starts can be incredibly hard. If the engine backfires you will have serious problems. I really dont see how the system could be intercooled.
We are doing a blow through system on a SB 400, with a stock carb, dont know how well its going to work yet. If more fuel is needed at the top end, we will add injectors on the upper charge pipe and have them run off a boost activated switch.
I am not suprised the blow through guys dicked you, I am sure this question has been asked many many times on their, so it gets old to them just like "how much boost can my d16 take" or "what turbo should I get for my d16" Its just going to happen anywhere with newbs. My best advice is just keep doing research, the maxium boost book by corky bell is really good man, especially when talking about different types of blow through/draw through setups.
Jeff
We are doing a blow through system on a SB 400, with a stock carb, dont know how well its going to work yet. If more fuel is needed at the top end, we will add injectors on the upper charge pipe and have them run off a boost activated switch.
I am not suprised the blow through guys dicked you, I am sure this question has been asked many many times on their, so it gets old to them just like "how much boost can my d16 take" or "what turbo should I get for my d16" Its just going to happen anywhere with newbs. My best advice is just keep doing research, the maxium boost book by corky bell is really good man, especially when talking about different types of blow through/draw through setups.
Jeff
02-12-2003, 05:10 PM
#5
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Re:draw through VS. blow through
I did alot of research on this.. What you need is a pressure carburator, or a carburator pressure box..
The whole blow through thing is very very dangerous..
Intercooling is out of the question "they explode in this type os setup"
One avenue i researched is the minnow fish carburetor..
This thing is oblivious to pressure changes , altitude , boost, whatever.. only problem is they are no longer produced in the us. I wrote to Bob Hendrickson who invented the thing.. He claims he still makes them but refuses to export them to to the us, also claims thet he wont sell them for turbo use unless his shop does the turbo kit...
Bob claims that the carb is so responsive to pressure changes that they have never had any lag on any of their turbo kits.. None of these "kits" use intercoolers.
its a very interesting topic.. Blow through can crush your floats, cause fuel to backup in the system, the only way to offset this is to crank up the fuel pressure, but this will blow all the seals on a carby.. There are only a few carby's that can handle it..
you will do much better searching on "pressure carburators"
Wildman
The whole blow through thing is very very dangerous..
Intercooling is out of the question "they explode in this type os setup"
One avenue i researched is the minnow fish carburetor..
This thing is oblivious to pressure changes , altitude , boost, whatever.. only problem is they are no longer produced in the us. I wrote to Bob Hendrickson who invented the thing.. He claims he still makes them but refuses to export them to to the us, also claims thet he wont sell them for turbo use unless his shop does the turbo kit...
Bob claims that the carb is so responsive to pressure changes that they have never had any lag on any of their turbo kits.. None of these "kits" use intercoolers.
its a very interesting topic.. Blow through can crush your floats, cause fuel to backup in the system, the only way to offset this is to crank up the fuel pressure, but this will blow all the seals on a carby.. There are only a few carby's that can handle it..
you will do much better searching on "pressure carburators"
Wildman
02-12-2003, 05:21 PM
#6
1.0 BAR
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Join Date: Feb 2003
Location: Wisconsin
Posts: 461
Re:draw through VS. blow through
i looked at a couple of pressure capable carbs and they were close to or over 1000 dollars. I was thinking about the pressure box thing too. I once saw a 454 chevy making over 800 that ran a supercharger and it used a pressure box around the carb to keep the seals from heading south on it. A guy i talked with uses an adjustable fuel pressure regulator and plumbs it into is intake pipe, so when the pipe pressure rises, the fuel regulator responds to the increase in pressure by boosting fuel pressure. A system like that would be fairly cheap and should be reliable. What do you guys think?
02-12-2003, 06:08 PM
#7
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Join Date: Feb 2003
Location: Wisconsin
Posts: 461
Re:draw through VS. blow through
i got my hands on a copy of Maximu, Bosst and read the chapter on the blow through carb setup and it actually doesn't sound that bad to fix the pressure problem, i just have to epoxy the ---- out of every joint and port and plug on my holley 670 and it should work just fine. Josh
02-13-2003, 04:58 PM
#8
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Re:draw through VS. blow through
isn't maximum boost like a real old book? I think i have a copy somewhere..
The best and easyiest way is to use a pressure box..
this creates even pressure on the inside and outside of the carb.. The fmu is required to raise the fuel pressure to match boost. otherwize your fuel will be blown back into the system by the boost pressure against the venturi of the carb.. Just about any carb can be used in a pressure box. Alot of people have made their own boxes "I dont remember what site I saw them on"
Most of this type of application would require water injection and alot of timing retardation apon boost.
otherwise detonation can take place. Some real good setups have been acheived this way. its quite possible.
The best and easyiest way is to use a pressure box..
this creates even pressure on the inside and outside of the carb.. The fmu is required to raise the fuel pressure to match boost. otherwize your fuel will be blown back into the system by the boost pressure against the venturi of the carb.. Just about any carb can be used in a pressure box. Alot of people have made their own boxes "I dont remember what site I saw them on"
Most of this type of application would require water injection and alot of timing retardation apon boost.
otherwise detonation can take place. Some real good setups have been acheived this way. its quite possible.
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