Author Topic: Fuel rails require tune asap or are fairly safe?  (Read 2285 times)

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Offline iblackwe

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Fuel rails require tune asap or are fairly safe?
« on: April 03, 2016, 12:10:12 pm »
Fuel rails, will my car be drivable afterwards or would I need a tune right away. I get that they will run richer than stock but by how much? And is it a safe break in amount? It's a brand new motor that is going to need some break in. I feel like if it's running richer it will actually be safer than a lean situation.

Also is the stock fuel pressure 39 Psi? (I am taking about the rail pressure taken when the pump is running and the car is off)

To be honest the reason I am upgrading is because I have the intake off and I hate the rats nest of a design the stock system is. For the life of me I don't want to put it back on the car.

I was also told the brand of rail doesn't matter near as the Fuel pressure regulator is the most important piece and cannot be cheapes out on. As the rail is essentially... A hollow tube with ports for the injectors. I was told to go with 6an port size... Is this the recommended size as well?

I tried a search and came up with 6 posts most talking about specific upgrades and not the tune involved, if anyone can give me some sound advice or point me in the right direction that would be much appreciated.

Offline Asstuna

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #1 on: April 03, 2016, 12:17:57 pm »
This is not an experience response, just some musing on my part.

If the pump is the same and the injectors are the same the conduit for fuel supply shouldn't matter. If the tubing is larger or longer it may need to be filled with more fuel. However, if the fuel in and the fuel out don't change why should you need a tune? You just have more volume in the system and it flows a little slower. Consider a lake with a stream coming in at one end and leaving at the other end. It's still the same flow rate.

I may well be wrong and am interested in replies from more learned persons.

Offline Ambystom01

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #2 on: April 03, 2016, 12:51:32 pm »
This is not an experience response, just some musing on my part.

If the pump is the same and the injectors are the same the conduit for fuel supply shouldn't matter. If the tubing is larger or longer it may need to be filled with more fuel. However, if the fuel in and the fuel out don't change why should you need a tune? You just have more volume in the system and it flows a little slower. Consider a lake with a stream coming in at one end and leaving at the other end. It's still the same flow rate.

I may well be wrong and am interested in replies from more learned persons.

I agree. I'm not an expert though, nor learned.
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Offline Barrett

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #3 on: April 04, 2016, 07:09:58 am »
I've been reading a lot of the FAQ's on NASIOC recently and remembered seeing something about fuel rails and tuning.

http://forums.nasioc.com/forums/showthread.php?t=1218460
"Do I need to tune for a fuel rails? Yes, due to the change in fuel rail diameter they will flow more to your injectors than the stock rails."
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Offline iblackwe

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #4 on: April 04, 2016, 07:14:55 am »
Yea I read this article too but am still in question. It would make sense with Tuna's thought that all it does is pool more fuel in the rail but if the fuel pressure remains the same and the injector is only going to draw as much as it did before in my mind.

I could see if the fuel pressure increased that it would cause the injector to draw more because there is more fuel being pushed to the injector. Otherwise I think it should operate at the same conditions.

Thanks for the opinions guys, if anyone else has experience installing fuel rails and what comes of it please let me know

Offline Dazzle

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #5 on: April 04, 2016, 08:05:22 am »
The most important part here is have you changed the fuel pressure?
Are you using the standard fpr or have you fitted an aftermarket unit that is adjustable?

My belief is the limiting factor to how much fuel will flow is still the injector. The only 2 things that will affect how much fuel the injector allows to flow is the duty cycle (how long it opens for) or the fuel pressure 'pushing' the fuel in when it opens!

Yes, new larger fuel rails mean there will be more volume of fuel in the rails waiting to be injected but this will only help in terms of recovery(just a larger lake as in Asstuna's analogy).

At the end of the day, it never hurts to get your engine tuned but I believe you will be okay as is as long as the fpr is the same.

That's my opinion and I have built a fuel injection system for my old Ford that used to run on carbs. I did however get that tuned not long after building it. I did break the engine in on a generic tune though  ;)

Hope that helps?
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Offline iblackwe

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #6 on: April 04, 2016, 12:44:49 pm »
That definitely helps, I am going to get a Tomei fuel pressure regulator that is a 1:1 ratio as is the stock FPR. I am also going to make sure it's set to the stock fuel pressure of which I believe is 39 Psi. Can anyone confirm that?

I think I am going to go ahead with this and I can keep you guys updated on what happens

Offline toytech

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Re: Fuel rails require tune asap or are fairly safe?
« Reply #7 on: June 03, 2016, 10:09:11 pm »
Fuel psi and duty cycle control the amount of fuel , rails wont change a thing , and don't forget there is a computer and some sensors that do all the math/fuel stuff so if you do change something that will make a difference it will compensate (within its limits , tune may still be required , blah blah blah , blow your car up ect)