DIY split fuel rails Reply #3

[Guest boostcut]

all of them if you can afford them/find them or just the top oring is usually enough. but since your post is 4 days old, im guessing you have done it?

[Leighos]

 boostcut said:

all of them if you can afford them/find them or just the top oring is usually enough. but since your post is 4 days old, im guessing you have done it?

No not just yet, just in the planning stages and wondering if it was necessary to replace them all. So by the top oring you mean on the injector body itself? not just on the cap aye?

[smokn4]

 Leighos said:

Sorry if this has been covered elsewhere...but when replacing injectors, or in this case relocating existing injectors to another right had rail, which of the many seals are recommended to be renewed?

ild say as many as poss

[Guest]

does it matter what size fuel hose is used?? as mine seems to be using way more fuel with this mod

ive blocked of the vac hose coming from tank? and teed the regulators into the manifold

[driftrex]

This alone wont cause more fuel to be used, and the hose you have blocked needs to be vented.

[Guest]

the system works on a pressure so what ever remaining fuel will return back to the tank

[Johnnynz]

So bumping this from the dead I know but if I am using factory regs and rails (2 x Drivers side rails) I have to cut the end that doesnt have the reg and flare it on each. Is that correct?

If so how did you guys cut them? Hacksaw?

Everything else seems fairly explanatory from the pictures...

[slydog]

 Johnnynz said:

So bumping this from the dead I know but if I am using factory regs and rails (2 x Drivers side rails) I have to cut the end that doesnt have the reg and flare it on each. Is that correct?

If so how did you guys cut them? Hacksaw?

Everything else seems fairly explanatory from the pictures...

yer thats the easyest way then use a file to get the sharp bits off, give it a good clean up make sure no metal bits in there

[titian]

If you using two fuel regulators the system will not balance and defeats the work of splitting the rails. ???

One reg will open before the other. Therefore cool fuel to one rail and warmer fuel to the other. :'(

Balanced flow to the rails and balanced return to one reg is the only way to achieve correct fueling for hi powered applications.

using hose clips is also a silly idea. ??? :

Ideally use crimped connections and braided Teflon lines for rail supply and return to and from split points (equal length!! 8mm from here to each rail + same for return). 10mm from tank to filter and split point for supply.

Remote rising rate reg fitted after return split point in the return to tank line.

Equal length supply and return to split points will avoid pressure drop flow losses to and from rails therefore maintaining fuel temp equal at all times. :) Hope this is easy to understand...not easy to explain typed. :

[funkytown]

how do you end up with hot and cold fuel across the rails?? and ive run 300wkw successfully for 3 years on two factory regsso i dont beleive any of the above blurb.

nothing to say flared pipe ends and good hose / clamps cant work just as well... as i have done it. nothing to say though teflon hose and fancy fits dont add safety

[Guest]

I just clamped my hose on without flaring and no leaks at 43.5+15psi.

This bullshit above has been spun a couple of times by memory...

[titian]

 funkytown said:

how do you end up with hot and cold fuel across the rails??

one reg will open and provide flow and pressure control...even if they are "set" the same. :.Therefore one rail will be cooler than the other. Because only one will have through flow, the other will only have injector flow.

Law of fluid dynamics..."a fluid will always follow the path of least resistance"

Don't believe me?...Disconnect both returns from your two regulators and run two equal length hoses into two separate catch buckets...Run engine and you will see the difference immediately!

Hoseclips and rubber hoses : ??? ??????..use at your own peril. ..never seen a professional race car setup using them...Could be wrong...Doubt it though :)

[Guest]

 titian']

[quote name='funkytown said:

how do you end up with hot and cold fuel across the rails??

/quote]

one reg will open and provide flow and pressure control...even if they are "set" the same. : .Therefore one rail will be cooler than the other. Because only one will have through flow, the other will only have injector flow.

Hoseclips and rubber hoses : ??? ??? ??? ..use at your own peril. ..never seen a professional race car setup using them...Could be wrong...Doubt it though :)

Jon that aint no race car...

[Johnnynz]

I am aiming for 200-220 KW, no more. Splitting rails for me is basic safety on injectors that should be more than sufficient for the job.

Its a street car that sees track from time to time...

[titian]

 Johnnynz said:

I am aiming for 200-220 KW, no more. Splitting rails for me is basic safety on injectors that should be more than sufficient for the job.

Its a street car that sees track from time to time...

do it properly then!...best way..."do it once do it right"

[Johnnynz]

Thats the plan. Personal watching of other cars has seen the setup I am planning to use work on cars running well in excess of the power I am looking for and also in cars much much quicker than mine will be.

Everytime I see the points you make raised (seen them a few times now) they seem to be debunked by the masses. I have yet to see an engine go pop on a simple 2 standard rail setup for lack of fuel.

[funkytown]

dude so many people run a split rail with two regs an it works just fine to very good effect. you are talking rubbish

johnny- verry wise idea my freind.LOL

[titian]

 funkytown said:

dude so many people run a split rail with two regs an it works just fine to very good effect. you are talking rubbish

johnny- verry wise idea my freind.LOL

fluid dynamics is science...not rubbish :

[Koom]

 titian']

If you using two fuel regulators the system will not balance and defeats the work of splitting the rails. ???

One reg will open before the other. Therefore cool fuel to one rail and warmer fuel to the other. :'(

Balanced flow to the rails and balanced return to one reg is the only way to achieve correct fueling for hi powered applications.

using hose clips is also a silly idea. ??? :

Ideally use crimped connections and braided Teflon lines for rail supply and return to and from split points (equal length!! 8mm from here to each rail + same for return). 10mm from tank to filter and split point for supply.

Remote rising rate reg fitted after return split point in the return to tank line.

Equal length supply and return to split points will avoid pressure drop flow losses to and from rails therefore maintaining fuel temp equal at all times. :) Hope this is easy to understand...not easy to explain typed. :

[quote name='funkytown said:

dude so many people run a split rail with two regs an it works just fine to very good effect. you are talking rubbish

johnny- verry wise idea my freind.LOL

/quote]

fluid dynamics is science...not rubbish :

So how are you guaranteeing "balanced" supply to both legs of a split system? If the fluids are going to follow the path of least resistance, what are you doing to ensure that one side doesn't have better flow performance than the other due to any of the constraints of flowing through the fuel rail system creating a path of least resistance?

Surely if you were going to go to those extremes, you'd correctly size the system so that it flows in at one end, steps down past each injector, flowing past all four, and then back to the pressure regulator in an inline setup so then there cannot be any "backwater legs" for the hot fuel to stagnant in and no longer be balanced.

How about trying your test with running the two separate lines into two buckets while the engine is under high load so that each injector is flowing much closer to their capacity and the regulator(s) are bypassing much less fuel because its going into the motor?

[titian]

Mr Koom...Obviously you are a scientific geek

My system has equal length flow and return hoses both "teed" so that common supply and return lines can be connected.

As both rails and lines are equal including elbows, fittings to the mm. A calculated assumption has taken place. Yes! there is possibly a very slight pressure drop difference between both sides. I did not perform a pressure drop test on each line as i am reasonably sure this pressure drop would be less than 10-20 Millibar and will not overly affect flow despite, :- "fluid will follow the path of least resistance"

This way of splitting the supply does work better than a two regulator system.

I have carried out the test i suggested on the two reg system...With OEM and aftermarket adjustable regs.

I could not achieve equal flow at all through both rails using two regs.(so i didn't bother going further)

With the setup i have installed i have measured temp of the fuel on both rails and found it to be within 0.3degC at all powers.(Non contact laser thermometer)

It is not possible to disconnect each return at the "tee" point as there is no pressure control to run engine.

I have therefore concluded that flow is as close to equal as practically possible and most certainly better than the standard across the engine setup or a two reg setup.

I suppose i could do this...:- Run the pump manually to see the difference..But given the temp is as near equal as damn it, i am pleased with the setup. :)

My opinion is that a one reg split rail system does work best. So long as equal pressure drop is maintained as near as one practically can

I hope this helps clarification and answers your Question/statement

FOR TEMP control..Nothing to do with pressure control.

[Guest]

Wouldnt the fuel temp increase be miniscule anyway if it even mattered? The only logical way I can see a difference in pressure per rail is if the regulators are slightly different. Obviously still close enough though... You can tune dc anyway? I really have no idea but hey hazard a guess for giggles.

[funkytown]

 evowrx said:

Wouldnt the fuel temp increase be miniscule anyway if it even mattered? The only logical way I can see a difference in pressure per rail is if the regulators are slightly different. Obviously still close enough though... You can tune dc anyway? I really have no idea but hey hazard a guess for giggles.

fuel temp cooling or heating has been proven to be a total misnomer many times. so for the purposes of this argument it doesn't make any difference.

i think youl find that pressure and flow are being confused also in this argument. regardless of which reg gives the highest FLOW, the PRESSURE will equalise across both rails as they are connected together and the excess will leave one reg slightly faster.

This will happen to a point where PRESSURE is equal. Injectors rely on PRESSURE, not FLOW so if PRESSURE is equal the injector can be tuned accurately and accordingly safe.

if you dont think its pressure they need, unplug your reg all together and you will have EPIC flow across the rail and no pressure, see how long the motor lasts at WOT

[Guest]

That sir is what my simple mind was trying to say just couldnt compound it in a regular sentence.

[titian]

Volume and Quantity are not the same. Temperature is the difference. ::)injector will deliver less fuel if it is heated above that which is cooler.(just like the red stuff in a thermometer expands)(Coloured alcohol)Petrol also expands quite well for small heat changes.

injectors provide a timed release. Less volume is released if fuel is heated above another injector that is releasing cooler fuel, Although the same quantity is released by both....Get it?

Why does No3 have BE failures = leaness/detonation.Why?..As above. Less burnable volume BUT the same quantity admitted compared to other injectors,In particular the first one serviced in the supply line flow, (No2 in OEM setup)

Equal temp of fuel for each injector is as important as correct pressure control and volume of supply. esp when WOT is being used a lot. or when achieving higher than OEM powers for longer than the OEM car.

[Guest]

Dwight started to explain something like this IIRC. Was he telling you this? He said no2 was tuned especially too for a different reason to 3 which he wasnt going in to.

 scottspeed said:

A properly tuned (ie motorsport) early model subi normally needs a tad more fuel in number 3 cylinder due to the chamber temperature from the exhaust and uppipe wrapped up around that cylinder. Version 5/6 open deck blocks normally require more fuel in number 2 cylinder but for a different reason. (Im talking stock or blueprinted engines and not forged/built engines btw)