Taylor-Racing

I think I'd go one further than that.
I've yet to see a convincing arguement that any change in the pressure line/resevior available to the fuel system could make a significant difference to life.

I'd be happy to be educated, though.

Francis M.

iTrader: (2)

the volume canister just gives the same effect as running
a longer pressure line. I really don't know what the magic
number is for pressure lines but i run 6-8 inches just enough
to minimize pulsing and not affect the fuel pressure too much.

Taylor-Racing

Yep, OK, but here's a couple of things that run through my mind.

No matter how long the pressure line (within reason) the pressure available to the fuel system is the same.

Having said that, with the engine continually going up and down it's rev range during a race, it will deliver variable pressure.

The available air volume when the tank is full is probably a couple of cc's and when it's near empty it's probably over 70cc's.

Given the above, how does a couple more cc's in a canister make any difference?

Fire

that makes sense, i guess the increase in volume helps when the tank is full maybe?

Francis M.

iTrader: (2)

it doesn't do nothing to on power pressure on the tank.
running a longer pressure line will minimize reverse pulsing
when you back of the throttle.

the pipe also pulls some vacuum out not just pushes air in to
the tank.

Taylor-Racing

Yep, I understand the negative pressure pulses. The pressure pulses cycle positive to negative continuously, at a high frequency rate equivelent to the engine RPM. The engine is just an air pump and I'd suggest the net result is always positive pressure - but yes, lower on the overrun as there is less work being done.

Given that air is compressable, and noting the large difference in air volume between an empty tank and a full one, I think it would be difficult to show the small volume difference afforded by an additional length of pressure line could have any significant influence.

Nitropimp

thanks.....Yeah, come out. Next time I'm at RC Tech on Tuesday I'll try to find you... What kind of car are you running??? You know MILF I'm sure....

V-One S

The extra length of fuel pressure line helps in a "Fuel Up" process...
In a car, you would hear your best setting is 14.7parts air to 1 part fuel...
That is actually only for emmisions...
12.5Parts air to 1 part fuel is best for PERFORMANCE,
Now we would usually tune for a 12.5-13parts air...
Now we all know air flows quicker then fuel...

Now just remember all that...


When your on the throttle, your engine is pumping so much pressure out of the exhaust, and into your fuel tank (via pressure line) and forcing fuel into the engine (instead of a pump pulling it)
Now when we lengthen that line, our fuel pulses are evened out, and actually slowed down, but there is still the same amount of pressure, but over a further distance,
Now as your racing along and you come off the throttle with a REALLY SHORT fuel line, the pressure in your tank drops, and as you hit the throttle, air moves in quicker then petrol, and so you drop out of your awesome tune...

Now we do the same thing but with a LONGER fuel line, now as we come off the throttle for our corner, the pressure does not drop as rapidly, so fuel is still being forced into the engine, so your carburettor is full of fuel...
Now we jump back on the throttle and all this air rushes in, and is imediately met by the already there fuel, and keeps that good tune, and sometimes runs slightly rich, so that as the fuel takes its time to build up its pressure again, the extra fuel is burnt off, giving a much better exiting acceleration...

If you followed that... well done...

Now it is probably given, that TOO LONG of a fuel line is bad in some parts of the race, mainly the start...
Think of it, your sitting at the line, waiting to go, you have your engine bueatifully tuned, and BAM, you slam the throttle open, now your engine doesnt have the extra pressure in you fuel tank to force fuel out quickly, it has to build it up, so you jump off the line, and what happens? you get a little stutter, and sometimes flame out... not good...
So really, you have to find that special "sweet spot" of fuel pressure line length, which, dependant on track is usually 6-8inches i believe...

Now a very tight and slow track, that then comes on really quick, to a fast and straight section, would probably prefer a shorter pressure line...
Why you ask?
Your in those tight corners, puttering around, not revving very hard, and so not a high pressure in the fuel tank, then you come onto your main straight, and WHAM with a long fuel pressure line, she stutters and dies out really...

But alot of people won't actually notice a difference at club meets...
really only top runners would "feel" a difference

Taylor-Racing

1. Pressure pulses, and the acoustic pulses, are generated and determined by the cycle of the engine. They will not be "slowed down" i.e. decreased in frequency by virtue of a adding length to the pressure line.

2. The pressure in the fuel tank and the pressure line are equal.

3. When you come in for a fuel stop and your pitman opens the tank to refuel, does the engine immediately stop? Granted, it won't run for ever with the tank open, but it won't immediately stop, either.

I submit that atmospheric changes during a race often have much more influence on engine tune than 4 inches of pressure line. But then again, as we're in Melbourne, maybe we see more of that than most.

So, I say again:
"Given that air is compressable, and noting the large difference in air volume between an empty tank and a full one, I think it would be difficult to show the small volume difference afforded by an additional length of pressure line could have any significant influence."

rjl

Gav, stop being pedantic. They make neat little pressure line cannisters and must sell them to show a profit. Actually my engine will idle for ever with the tank open, it just won't accellerate.

orangbaligila

guys,.. a little input from my experience.... I sucked real bad on my last race in a small track (engine stutters out of tight corners because fuel is not reaching the carb and stalls when WOT is applied right after a half-throttle corner),... this happened because I was running the car on a big track the week before (long pressure line suits the long track good, as you apply throttle and release it smoothly. however, in a smaller and tight, twisting track,.... short pressure line suits best, as you go on and off throttle rather quickly, the shorter line will be much more responsive

Taylor-Racing

Oooop's, forgot about that. I hear the Kawahara ones are the best.

V-One S

As i said would happen... Its to do with how long it takes the pressure to get to the tank... longer line, longer time... shorter line, shorter time...

rjl

Maybe the extra fuel line or volume just damps the pulses but the pressure at both ends tries it's best to be equal.

rjl

Don't know if they make one at all, if they do I'll get one for ya.