Aftermarket Fuel Rails

[BBGTR]

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The manifold has valves opening and closing, i once modelled an inlet manifold using Computational Fluid Dynamics software...it took a looong time to model and even then it was kinda crude, but what goes on inside a manifold cant be modelled by blowing a bit of water through a pipe...so if Nissan made the manifold the way they did...then for good reason.

I wasn't questioning the plenum design, like I said OEM stuff is usually very good. I was musing over the similarities to the question at hand.

We can even start talking about splitting the atom, at the end of the day I don't think an after market fuel rail is worth the money, particularly if you can fit different types of injectors to a standard unit.

They only way to deal with this is a bench test - I guess you would measure spray pattern at various flow levels and pressures. Anyone got a few hours and $$ to spare???

Regards

Andrew

[R31Nismoid]

you can see this in an off car efi cleaner. all injectors behave different, some injectors spray pattern suffer from over pressure, others dont. keep in mind that all factory parts are designed to operate inside set parrameters, when you start doubling boost pressure, you automatically double yor fuel pressure, which then starts to ask the question of the fuel pump. fuel is probably the most important aspect of a turbo car, and one you should not cut corners with. modify your system to suit your application. Upgrading fuel pump is a no brainer as most peoples pumps would be at least 10 years old anyway. Upgrade injectors if needed.

You will kow on the dyno if your at 90% duty, you have to upgrade. then the rail is sometimes necessary to be replaced depending on your style rail to suit new injectors, although you can now get high flow side feeds. after market reg is sometimes necessary with aftermarket rail as they do not incorporate the standard reg. Depending on the extent of your engine modifications, you should modify fuel system to suit.

everyones needs will be different, so posting that you do need this and dont need that is incorrect.

We seem to be agreeing on a number of things lately

Although this point i find interesting... only because we are talking about RB motors here

Depending on the extent of your engine modifications, you should modify fuel system to suit.

everyones needs will be different, so posting that you do need this and dont need that is incorrect.

Being that RB's are the topic of discussion, and there is such a large range of big flow injectors (over 700/800cc in some cases) and they provide enough fuel for the vast majority of applications and some very serious horsepower

Granted there are some special applications of course

Its then debatable that you are required to change the rail at all under 600hp, obviously the power ceiling was capped @ 600hp (i think) in application.

And thats all we are talking about, the rail... obviously not surge tanks/lift & supply fuel pumps etc

In reality, it would seem you dont need a fuel rail under 600hp in todays age on an RB.

2-3 years ago you would have as aftermarket parts were not as common...

And to be honest, i dont know of anyone that has upgraded thier fuel rail under that mark.

[R31Nismoid]

They only way to deal with this is a bench test - I guess you would measure spray pattern at various flow levels and pressures. Anyone got a few hours and $$ to spare???

Regards

Andrew

i have 550 (i think) Nismo's sitting in my bedroom waiting to go on my RB26 later this year.

Whilst not a large upgrade for the RB26... they are bigger either way.

If someone wants to also help out, im more than welcome to use those on a flow bench

Whilst not as big as the 740's i had in my RB25 (which would have been great to test) its still an interesting test with the 550's i would imagine

[N I B]

I always fit dual entrys and a center outlet to the stock rail.Stock rail has a bigger ID than most aftermarket rails.

[Adriano]

I would tend to agree with NIB, at horsepower above 600hp dual feeds and a center return is a cheap and relaively simple mod, i think the aim is to prevent leaning out in cylinder6 and to a lesser degree 5 which is due to the inlet manifold design and possibly slightly due to the rail, this is a very common problem wiht WRX's.

[Sydneykid]

Very interesting replies and some good questions, leaving me a few things to express my opinion on.

1. You would be surprised at how many RB26's there are with between 500 bhp and 600 bhp that have aftermaket fuel rails, people sucked in by retailers

2. My fluid dynamics is rusty, not that it was much good anyway. My understanding is the fuel pressure increases at the restriction (the fuel pressure regulator). This means #1 and #2 (at some point) will get more pressure than #5 and #6. That is not really the question, the question is at what point? Using the 2 examples I feel safe in saying 600 bhp is not the limit. The people involved are smart enough (and have most likely tested enough) to have left a safety margin. Hence my rule of thumb 700 bhp and the hint for puting the highest flowing injector in #6, then #5 etc.

3. That's 700 bhp with the feed at the rear of the rail and the FPR at the front. I wouldn't even consider duel inlets, centre pressure take off etc under that power target.

4. As Bezerkly pointed out, you can see (on the flow bench) when the fuel pressure gets too high for the injector and it looses spray control. Hence why I have a rule of thumb limit of not targeting higher than 10% additional flow from an injector.

5. Roy asked about spray patterns and fuel rails. When we are flow testing RB25DET injectors we use a standard RB25DET fuel rail. The flow bench comes with its own top feed fittings, so we don't need to use use a top feed rail. But it didn't come with side feed fittings, so we adapted an RB25 rail.

The largest side feed injectors we have flow tested were a set of 740 cc Nismos. Accross the 6 they showed absolutely zero difference in spray pattern at 765 cc (they are a bit underrated) and 73.5 psi of fuel pressure. We test at 73.5 psi as it is the rated pressure at flow for the Bosch fuel pumps that we use. So that's (say) 38 psi of fuel pressure (standard) above 35.5 psi (2 bar) of boost.

That's obviously at 100% duty, the injectors are fully open and stayed open for the full test. Pulsing (less than 100% duty cycle) makes no difference to the spray patterns, that you can see in the glass containers anyway.

The internal dimensions of a standard RB25 fuel rail are slightly smaller than a standard RB26 fuel rail. So I have no hesitation is saying that an RB26 fuel rail would give similar results.

6. (For the rice boys), the standard rail is cad plated stainless steel, if you polish the cad, it will dull down over time. If you polish off the cad plating completely, you are left with stainless steel, which doesn't dull down after polishing for a long time. Then it quickly polishes back up to a mirror finish.

cheers

Edited April 7, 2006 by Sydneykid

[N I B]

Ive found that twin feeds on very big injectors keeps the fuel pressure much smoother and as its easy and cheap and does not cause any problems its worth the effort even if the only gain is peace off mind.

[PHaT MR30]

I think Garry should work for MINES

[Denver]

curiosity question..

what happens if you where to reverse the end of the rail the reg lives on..

Im looking to do the entry at the front of the rail, and the reg on the back, eg piston 6, so i can mount the reg up on the firewall, and then plumb it directly into the hardline return pipe..

would it then make no 1 the lean piston?, or would it just get around the lean out issues with no6?

[Roy]

The largest side feed injectors we have flow tested were a set of 740 cc Nismos. Accross the 6 they showed absolutely zero difference in spray pattern at 765 cc (they are a bit underrated) and 73.5 psi of fuel pressure. We test at 73.5 psi as it is the rated pressure at flow for the Bosch fuel pumps that we use. So that's (say) 38 psi of fuel pressure (standard) above 35.5 psi (2 bar) of boost.

That's obviously at 100% duty, the injectors are fully open and stayed open for the full test. Pulsing (less than 100% duty cycle) makes no difference to the spray patterns, that you can see in the glass containers anyway.

The internal dimensions of a standard RB25 fuel rail are slightly smaller than a standard RB26 fuel rail. So I have no hesitation is saying that an RB26 fuel rail would give similar results.

...answers that then. Std rails still look gay...im goign to polishe it up and get it coated in the hope that someone will go "oooh....aaaaahhhhh" when i next pop the bonnet. Plus it does get very hot

[Sydneykid]

I think Garry should work for MINES

THEY could afford me , based on the prices they charge .

cheers

Edited April 10, 2006 by Sydneykid

[Guest Mashrock]

Its all about the bling lad!!!

[Guest Mashrock]

i run nismo reg and std rail. big injectors

[ISL33P]

NIB is on the money.

bare with me here i have a point (hopefully), what is the most common cylinder/piston to sieze or break/crack or just fail in general on a lot of lightly modified engines ?

i am asking about lightly modified engines/cars, upto 350rwhp, as this is what the majority of people have.

[Sydneykid]

NIB is on the money.

bare with me here i have a point (hopefully), what is the most common cylinder/piston to sieze or break/crack or just fail in general on a lot of lightly modified engines ?

i am asking about lightly modified engines/cars, upto 350rwhp, as this is what the majority of people have.

My guess would be #5

Nothing to do with injectors, I reckon

More likely combustion temperature caused by water flow through the jackets

Maybe the short run from #5 to the turbo on the standard manifold

We flow test Skyline injectors all the time. Using the standard rail, with the pressure reg at one end and feed at the other, there is no difference in the injector flow rates based on their location in the rail. Individual injecotrs may flow slightly different amounts (up to 3% is not uncommon). But when you move the injector, the flow difference travels with it. So it isn't the location in the rail causing the difference, it's the injector itself.

cheers

[ISL33P]

does 6 have the same problem ?

is there any difference in pressure for each injector on the tests you have done ?

is this based on std inj's or different size ones ?

[Denver]

curiosity question..

what happens if you where to reverse the end of the rail the reg lives on..

Im looking to do the entry at the front of the rail, and the reg on the back, eg piston 6, so i can mount the reg up on the firewall, and then plumb it directly into the hardline return pipe..

would it then make no 1 the lean piston?, or would it just get around the lean out issues with no5/6?

anyone got any ideas on this one before i go and do it?

[Senna88]

Good feedback guys, thanks.

My own fuel rail is a combination of the Gibson and Mines. I have used a Nismo bolt on FPR in the standard location at the front. I cut off the standard fuel pipework and fitted a dash fitting into the rear of the rail. It is simply threaded into the rear of the rail where I cut off the standard pipework.

I will post up some pictures shortly.

cheers

PS; on the RB25DET Neo injectors question....when we had the R34GTT I used the Nismo 480 cc injectors. They had no problems with 315 rwkw with a slight upgrade in fuel pressure (couple of pounds). I figured that was plenty for the standard internals.

Hey, any picures of the mod you did? what fitting did you use for the return from the rail?

[zebra]

9 year thread dig, that must be a recent record

[Senna88]

Search function came in handy seems to be the closest thing to what im after, hopefully can get some answers!