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 Post subject: Blow through carb set-up
PostPosted: Mon Feb 27, 2006 6:14 pm 
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Joined: Thu Jul 28, 2005 9:30 pm
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Location: Ulverstone, Tasmania, Australia
I am currently helping a mate with his turbo 13B engine build, but we have run into some problems with working out how to fuel it, it has a 600 Holley (dp) which it will be 'blowing' through.

We were thinking of building a box around the carb or just modifying the carb to cope with the pressure, does anyone know how to makie a 'carb box' or had any experience with them, or does anyone know what needs to be done to a carb for it to work in a 'blow through set-up'????

I know that a high pressure pump needs to be used and a rising rate fuel pressure regulator, and that the floats need to be filled with something to stop them crushing under the pressure, also i know that when not running a carb box there are several things on the carb which need to be sealed

Boost will be around 8psi and the fuel is Avgas

Any help would be great, or maybe someone knows of a good site that explains it 'in full'


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PostPosted: Mon Feb 27, 2006 6:40 pm 
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Lampredi's best buddy
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Location: Hawkins County, Tennessee, USA
Ryacap wrote:
I am currently helping a mate with his turbo 13B engine build, but we have run into some problems with working out how to fuel it, it has a 600 Holley (dp) which it will be 'blowing' through.

We were thinking of building a box around the carb or just modifying the carb to cope with the pressure, does anyone know how to makie a 'carb box' or had any experience with them, or does anyone know what needs to be done to a carb for it to work in a 'blow through set-up'????

I know that a high pressure pump needs to be used and a rising rate fuel pressure regulator, and that the floats need to be filled with something to stop them crushing under the pressure, also i know that when not running a carb box there are several things on the carb which need to be sealed

Boost will be around 8psi and the fuel is Avgas

Any help would be great, or maybe someone knows of a good site that explains it 'in full'


I'm currently running a blow through system on a 1500 Fiat motor I have installed in my Yugo.

http://users.chartertn.net/jseabolt/yugo.htm

All details are covered except for a few you asked. There is some leakage around the throttle shafts but it's not any worse than the IDFs I ran on a Fiat Spider or my friend's dual carb X 1/9.

The only issue I have now I can't seem to figure out is I seem to be using allot of fuel under cruise. The DFTA carb was originally set up for a 55hp 1100cc engine. I thinking I'm making 75hp + 25hp (boost) on a 1500cc engine.

I would think I would need a bigger idle jet (bigger motor) but some people on another forum seem to think I need a smaller primary idle jet.

Otherwise the fuel/air meter says I'm running at stoch at idle but pegged out under cruise.

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James

1980 Fiat Spider 2000 (turbocharged)
1987 Yugo GV (1500 turbocharged)
2003 Subaru Legacy Baja (Liberty Ute to you guys)
2006 Ford Explorer Limited V8
1968 Ford Fairlane 500
1981 Trabant 601 "S"


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 Post subject:
PostPosted: Mon Feb 27, 2006 8:38 pm 
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Uncle Abarth
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Location: Taupo, New Zealand
for info on making a holley boostable goto the tech section of http://www.turbomustangs.com there is a pretty good how to guide, and although the people on the forum might be fans of boat anchors there is some pretty good info there too if you trawl through it a bit.


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 Post subject:
PostPosted: Tue Feb 28, 2006 9:42 am 
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Lampredi's best buddy
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Location: Hawkins County, Tennessee, USA
Testament wrote:
for info on making a holley boostable goto the tech section of http://www.turbomustangs.com there is a pretty good how to guide, and although the people on the forum might be fans of boat anchors there is some pretty good info there too if you trawl through it a bit.


Here's another great site.

http://www.hangar18fabrication.com/blowthru.html

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James

1980 Fiat Spider 2000 (turbocharged)
1987 Yugo GV (1500 turbocharged)
2003 Subaru Legacy Baja (Liberty Ute to you guys)
2006 Ford Explorer Limited V8
1968 Ford Fairlane 500
1981 Trabant 601 "S"


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PostPosted: Tue Feb 28, 2006 4:12 pm 
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Lampredi's best buddy
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Location: Laihia, Finland
Ryacap wrote:
or does anyone know what needs to be done to a carb for it to work in a 'blow through set-up'????


The modifications to the Dellorto DRLA carbs included fitting a rubber tip needle valve and rubber float chamber gasket. Some specially made turbo carbs have also axle seals at throttle axle.

Ryacap wrote:
I know that a high pressure pump needs to be used and a rising rate fuel pressure regulator,


Not rising rate, because the fuel pressure must be kept constant compared to the boost pressure (0.2...0.4 bar above the boost).

Ryacap wrote:
and that the floats need to be filled with something to stop them crushing under the pressure,


Yes. Some of the floats are so rigid that they won't collapse. That can be tested by pressurizing it inside a glass jar.

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My Fiat Pages! Projects, TC Engine List, Other Info... ** Note the new address! **


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PostPosted: Tue Feb 28, 2006 8:44 pm 
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Lampredi's best buddy
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Location: Hawkins County, Tennessee, USA
I'd also highly recommend a dump/blow off valve to prevent fuel pressure spikes between shifts.

Biggest issue I've had with my Yugo is blowing the needle off the seat. Once that happens I have to take the top half of the carb off and put it back on to reseat the float valve.

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James

1980 Fiat Spider 2000 (turbocharged)
1987 Yugo GV (1500 turbocharged)
2003 Subaru Legacy Baja (Liberty Ute to you guys)
2006 Ford Explorer Limited V8
1968 Ford Fairlane 500
1981 Trabant 601 "S"


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