Pressure Line Question
#1
Pressure Line Question
I just lengthened my fuel line to make sure I don't have issues when I am upside down. However, my car has recently become hard to start. I think it is because I have less pressure now because of the added fuel line. Assuming I am right, should I shortened or lengthen the pressure line or leave it as is and try and re-tune. What changes should I expect when the fuel line has been lengthened?
Also, my car has started faming out at pit stops. Is this related or something completely different?
Also, my car has started faming out at pit stops. Is this related or something completely different?
Last edited by petevette; 11-01-2009 at 04:29 PM.
#2
There are so many factors that can cause the symptoms you have described. How many gallons is through the engine, what engine, how is your glow plug, how soon does it flame out after you flip, how is your clutch (Shoes, springs, bearings).
I think I read somewhere the pressure line should be half the length of the fuel line, but i could totally be wrong. I just have my lines nice and clean and tight, sorta like my racing line
I think I read somewhere the pressure line should be half the length of the fuel line, but i could totally be wrong. I just have my lines nice and clean and tight, sorta like my racing line
#3
The engine has 1 gallon and runs well. I haven't had a flameout problem when upside down, but wanted to prevent getting one since we have some slow turn marahalls. I haven't checked the plug in a few races.
The flameouts come only on refuel once my car has been dropped and I gun it. Half way out of the pit it stalls. Oh, on warms up I heard a sound twice like a backfire.
The flameouts come only on refuel once my car has been dropped and I gun it. Half way out of the pit it stalls. Oh, on warms up I heard a sound twice like a backfire.
#4
Tech Master
iTrader: (34)
i found that longer fuel line is worse for slow marshalls, if they are slow then there is a bigger bubble in the line once they flip it and you flame out every time. just tune your motor right and it should idle fine upside down, if you sit there and rev the motor it sucks more air into the line quicker. the best solution is a clunk style tank, like losi, and this mod can be done to any tank very easily (as long as the tank does not have really tall internal chambers that can make the clunk stick on top higher than the fuel) with the use of an airplane tank clunk and a drill bit that is about 2mm smaller than the od of the fuel line used.
#5
Changing fuel line length alters your tune. Retune.
Don't overdo it. The line routing in AE's or XRay's instructions is about right for most cars. I keep my pressure line as short as possible, about 8 inches as I want its bends to be smooth.
Fresh air filter, fresh clutch and bearings, fresh DUBRO fuel line, fresh glow plug and retune with fresh fuel.
You engine will change tune at 1 gallon and again at 2. It's hard to recommend stuff without being there, take it to the track, make a fellow racer help you tune by holding him at gunpoint.
Don't overdo it. The line routing in AE's or XRay's instructions is about right for most cars. I keep my pressure line as short as possible, about 8 inches as I want its bends to be smooth.
Fresh air filter, fresh clutch and bearings, fresh DUBRO fuel line, fresh glow plug and retune with fresh fuel.
You engine will change tune at 1 gallon and again at 2. It's hard to recommend stuff without being there, take it to the track, make a fellow racer help you tune by holding him at gunpoint.
#7
The engine has 1 gallon and runs well. I haven't had a flameout problem when upside down, but wanted to prevent getting one since we have some slow turn marahalls. I haven't checked the plug in a few races.
The flameouts come only on refuel once my car has been dropped and I gun it. Half way out of the pit it stalls. Oh, on warms up I heard a sound twice like a backfire.
The flameouts come only on refuel once my car has been dropped and I gun it. Half way out of the pit it stalls. Oh, on warms up I heard a sound twice like a backfire.
#8
Great input guys, I will check/try some of this stuff next time out.
So to summarize, the shorter the pressure line the better? Meaning that the shorter the line the higher the pressure?
So to summarize, the shorter the pressure line the better? Meaning that the shorter the line the higher the pressure?
#9
Tech Addict
Also, if your fuel line is too long it will cause problems. Imagine if you hook up a hose to a hose bib and turn the water on. If you add another hose you lose pressure at the end. Keep adding hoses and eventually the water will just dribble out. The pressure at the source has to push more and more fluid at once.
#10
After reading everyones suggestions I would add taking a look at your fuel tank itself! Sometimes the rubber seal thats in the lid goes bad causing all kinds of problems! Suberse it in water leaving the lines connected to the tank out of the water and blow in your pressure line. If bubbles appear around the lid you've got a bad seal.
#11
Tech Initiate
what engine and tune pipe you are running ?
#13
Tech Elite
iTrader: (45)
Join Date: Jun 2003
Location: Somewhere in Penang Island, Malaysia
Posts: 3,495
Trader Rating: 45 (98%+)
+1.......when your pit crew refueling and before he drop your car on the pit lane, try rev your engine to clean up your low end and this I feel can solve your stalling problem after refueling. Looking to hear from you soon what you find. I also learning.
#14
8 " Pressure 8" supply
My engine guy (Monty Houston) swers by that rule. I haven't had any issues with mine when she's turtled. I just cycle the throttle to keep the pressure up. If your clunk has a line long enough to keep it picking up fuel I dont think the motor cares which way it is as long as you give it fuel. just remember to let off the throttle while the marshaller picks it up.