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Old 03-19-2008, 04:17 PM   #1
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What are the effects of having different (short or longer) lengths of the pressure line from the pipe to the tank? Whats recommended for on road applications?
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Old 03-19-2008, 04:25 PM   #2
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What are the effects of having different (short or longer) lengths of the pressure line from the pipe to the tank? Whats recommended for on road applications?

I second that question
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Old 03-19-2008, 04:31 PM   #3
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I was going to go off on one of my detailed in depth explanations here but She has cold beverages. What are we talking about, .12 or .21?
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Old 03-19-2008, 04:36 PM   #4
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I was going to go off on one of my detailed in depth explanations here but She has cold beverages. What are we talking about, .12 or .21?

for me .12 Picco
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Old 03-19-2008, 09:35 PM   #5
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.12-.18
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Old 03-19-2008, 10:07 PM   #6
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What are the effects of having different (short or longer) lengths of the pressure line from the pipe to the tank? Whats recommended for on road applications?
The Problem
If you've done much gas racing, you've probably encountered the dreaded lean bog that occurs right after a pit stop with a full tank of fuel. Right after the tank is filled, for about the next 3 or 4 laps the engine sags (lean bogs) when accelerating off of tight right-hand corners. On most tracks this happens when accelerating onto the straight. Seemingly, the lean bog magically goes away after a few laps but sure enough, after the next pit stop, it frustratingly returns-slowing lap times for several laps once again.

The key to eliminating full tank lean bogs is pressure tube position, length of the pressure line from the pipe to the tank, or adding a pressure reservoir.

To solve this frustrating issue, it's important to understand what's causing it.
Here's the scoop. As the throttle is released entering a turn, the pressure in the tank is now greater than the reduced pressure in the pipe. When the tank is full, some of the fuel sloshes up into the pressure line. The centrifugal forces encountered in a right hand turn further pulls the fuel into the pressure line, causing reduced pressure in the tank. When the throttle is cracked open to accelerate, the engine goes lean because of this reduced tank pressure and hence the dreaded lean bog occurs.

The reason it only lasts for a couple of laps is that as the fuel level goes down in the tank it's less likely to slosh as much into the pressure line and, as the fuel level goes down there is a larger open space in the tank that's pressurized, maintaining adequate pressure long enough to prevent the low pressure lean bog problem. (If your exhaust system is mounted on the left side,, then this phenomenon will occur in left hand turns.)

The Fix
Keep the fuel out of the pressure line! That's sometimes easier said than done. We've had the most success by rerouting the pressure line so that as it comes off the pressure nipple, the tubing goes to the right side of the fuel tank, then makes a loop on the right side of the tank. This prevents the centrifugal force of a right hand turn from filling the pressure tube. We've also had good success by adding one of the big reservoirs (they look like a big aluminum fuel filter), in the pressure line. Many manufacturers have recognized this problem and are making special pressure pickups and tank lids with large open volumes in the lid itself. You may have noted that many top drivers' cars have several loops of fuel tubing wrapped in their cars and wondered what was the purpose. Now you know. The key to fixing this issue is to experiment with pressure tube routing, length, and if necessary, installing a pressure reservoir in the pressure line.

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Old 03-20-2008, 12:59 AM   #7
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Take a short and a long piece of fueltube an blow trough it. The longer one will give more resistance and will cause less pressure in the tank.
Bogging or Cogging can be solved with the pressureline.

I minimise pressure with just making an airleak in the line:

It is just an empty fuelfilter with at the side a nipple made and a piece of fueltube to flow away the oil from the exhaust.

With this you will get a different pressure characteristic with a better picking up engine and a bit more fuel economic
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Old 03-20-2008, 01:50 AM   #8
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Take a short and a long piece of fueltube an blow trough it. The longer one will give more resistance and will cause less pressure in the tank.
Bogging or Cogging can be solved with the pressureline.

I minimise pressure with just making an airleak in the line:

It is just an empty fuelfilter with at the side a nipple made and a piece of fueltube to flow away the oil from the exhaust.

With this you will get a different pressure characteristic with a better picking up engine and a bit more fuel economic
with this air pressure outlet, won't this reduce the pressure in the tank and lean out the engine more? i would assume you will have to tune rich to compensate the effect.

i always thought those bogs right after refueling were due to being rich rather than being lean.
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Old 03-20-2008, 02:34 AM   #9
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with this air pressure outlet, won't this reduce the pressure in the tank and lean out the engine more? i would assume you will have to tune rich to compensate the effect.

i always thought those bogs right after refueling were due to being rich rather than being lean.
Yes, you have to re-tune the engine a bit richer but it makes the engine less pressure sensitive and so you will loose the problems with a full tank.
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Old 03-20-2008, 03:31 AM   #10
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Had anyone tried this from Team Orion used @ 1/8 IFMAR Worlds


Team Orion CRF Constant Pressure Device CPD #ORI88551

When an engine is running at full throttle, a large volume of burned gases flow through the exhaust. Part of the gases are expelled out of the exhaust pipe and part of the gases find their way towards the fuel tank.

Engines have 2 main settings, High Speed Needle HSN and Low Speed Needle LSN. Engines are tuned to have the highest speed possible with the HSN and to be stable at idling with the LSN.

When the engine stands idling, only a small amount of pressure is created, when the engine runs a full throttle a large amount of pressure is created.

Problems arise when you switch from full throttle to low speed, high pressure generated from running at full throttle is still present and it is pushing fuel to the carbutaror inlet though the carburator is closed. Because of this the mixture will become too rich, causing slower acceleration and wasting fuel.

The CRF CPD acting as a pressure valve system, effectively resolves this problem by regulating the amount of pressure going to the fuel tank. The valve allows a constant amount of pressure to be sent to the fuel tank, by opening or closing itself depending on the engine’s rotation speed.

Constant pressure allows for:

• Easier adjustement for ANY type and size of engine.
• Better low end response because the mixture always remains
correct and does not enrichen because of the excess pressure.
• Longer run times because there is no excess pressure pushing
un-needed fuel inside the engine..

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Old 03-20-2008, 06:18 AM   #11
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Is this CPD roar legal??
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Old 03-20-2008, 07:07 AM   #12
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now that the explanation has been given, whats the length people run on average?
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Old 03-20-2008, 08:46 AM   #13
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now that the explanation has been given, whats the length people run on average?
I run between 8 and 10 inches pressure line on my .12 Piccos

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Old 03-20-2008, 11:06 AM   #14
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I run between 8 and 10 inches pressure line on my .12 Piccos

AFM
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Old 03-20-2008, 11:42 AM   #15
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I use a pressurechamber from Mugen and that works great.

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