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Old 01-20-2008, 03:32 PM   #41
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My question is, does anyone have hard evidence/facts to back up that there is a benefit from doing this. Theory aside, I have yet to see proof this helps anything on a boosted engine. I talked to Corky Bell about it a while back, and he says way back when, he did a bunch of actual bench testing on the fuel rail for the Miata, and found that making it dual feed didn't do anything at all, hence why he doesn't market a product like this. This seems more like a fashion trend as "everyone is doing it", but have no evidence to prove its real benefits.
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Old 01-20-2008, 03:37 PM   #42
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^ exactly what I have been thinking. I am not an expert in fuel systems. But I dont understand the purpose of this mod if its a pressurized rail, it shouldnt matter that fuel flows from both ends or not. Especially if the fuel return is right where the second inlet would be.
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Old 01-20-2008, 03:51 PM   #43
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^True... but it's $3 and about 20 minutes to do it... so if there is a benefit, even miniscule... it's good to follow the masses.

If there isn't a benefit, you're out nothing.
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Old 01-20-2008, 03:54 PM   #44
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Quote:
Originally Posted by samnavy View Post
^True... but it's $3 and about 20 minutes to do it... so if there is a benefit, even miniscule... it's good to follow the masses.

If there isn't a benefit, you're out nothing.
You ever heard of the term "reinventing the wheel"?

The only time I would imagine a dual feed would be most beneficial is when you are running so much fuel out of your injectors that you cant maintain adequate fuel pressure.

edit: shoulda made this thread a poll.

edit 2: I am just a student in all of this. My goal is to question everything until I have a complete understanding of it. Conversely I also dont like doing extra things I don't need until i know there is a definitive benefit in it.
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Old 01-20-2008, 04:05 PM   #45
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yeah, i already have the fitting installed and i am getting ready to apply the jb weld. I will probably just put the two spacers that i have on the outsides and maybe put some washers in place of the missing spacer.
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Old 01-20-2008, 04:37 PM   #46
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Originally Posted by wes65 View Post
yeah, i already have the fitting installed and i am getting ready to apply the jb weld. I will probably just put the two spacers that i have on the outsides and maybe put some washers in place of the missing spacer.


As said above, $3, 20minutes = why not...
Im a newby, theory makes common sense to me, costs nothing, could be seen as added insurance if nothing else, and a chance to do simple diy project..if nothing else, look at what fm sells theirs for and feel good that u did it with $3!
Anyway, sounds like u did fine except for the spacer, and u have ur solution.. Make sure u replace the lines as they were and dont mix them up.. Im a nerd, so i put a piece of tape on 1 line and another on the corresponding hardline just in case, but really not needed if ur not a burnout like me

ps-dont forget jb weld takes like 24hrs to cure i think, read the back of the tube
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Old 01-20-2008, 05:03 PM   #47
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Originally Posted by tvalenziano View Post


As said above, $3, 20minutes = why not...
Im a newby, theory makes common sense to me, costs nothing, could be seen as added insurance if nothing else, and a chance to do simple diy project..if nothing else, look at what fm sells theirs for and feel good that u did it with $3!
Yea, newbies just eat this stuff up and do it. Except it doesnt make sense. Price isnt the issue.
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Old 01-20-2008, 06:34 PM   #48
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well, newbies (me included) may eat this up but hell, i had nothing better to do today and like he said, FM sells a dual feed fuel rail so im sure that it doesnt hurt anything.
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Old 01-20-2008, 06:49 PM   #49
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Quote:
Originally Posted by Saml01 View Post
You ever heard of the term "reinventing the wheel"?

The only time I would imagine a dual feed would be most beneficial is when you are running so much fuel out of your injectors that you cant maintain adequate fuel pressure.

edit: shoulda made this thread a poll.

edit 2: I am just a student in all of this. My goal is to question everything until I have a complete understanding of it. Conversely I also dont like doing extra things I don't need until i know there is a definitive benefit in it.
Dollars to doughnuts, I'd bet the dual feed rail does indeed help keep pressure high in the rail under heavy load. I've read of people reporting that a DF rail is good for an appx 5% reduction of IJDC on cars over 200 whp.
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Old 01-20-2008, 07:11 PM   #50
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Originally Posted by Saml01 View Post
Yea, newbies just eat this stuff up and do it. Except it doesnt make sense. Price isnt the issue.
Price isnt the only factor, just a bonus...and as a newby u tend to listen to those that have been there and are giving the advice...

Anyway are there any downsides to the mod? Or are u guys just saying it may not be neccessary? When I looked into doing it, i didnt see anyone talking about any issues in doing this....
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Old 01-20-2008, 07:16 PM   #51
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There aren't any downsides unless you are just retarded and screw up drilling and tapping the end, thus spraying fuel all over your hot engine as it bursts into flames. With all the smoke, you can't see and end up driving off a 200 foot cliff, you come crashing down on your mom, everyone dies. The end.
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Old 01-20-2008, 09:28 PM   #52
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Originally Posted by wes65 View Post
well, newbies (me included) may eat this up but hell, i had nothing better to do today and like he said, FM sells a dual feed fuel rail so im sure that it doesnt hurt anything.
FM are a bunch of capitalists, I would take anything they say with a grain of salt until I see facts to back up claims.

Quote:
Originally Posted by tvalenziano View Post
Price isnt the only factor, just a bonus...and as a newby u tend to listen to those that have been there and are giving the advice...

Anyway are there any downsides to the mod? Or are u guys just saying it may not be neccessary? When I looked into doing it, i didnt see anyone talking about any issues in doing this....
You're in the finance business, you know not to listen to anyone when it comes to where to invest your money, you do your own due diligence. Might be a bad example, but you gotta think for yourself and first prove to yourself that you believe in something before blindly following someone else.

Quote:
Originally Posted by Ben View Post
Dollars to doughnuts, I'd bet the dual feed rail does indeed help keep pressure high in the rail under heavy load. I've read of people reporting that a DF rail is good for an appx 5% reduction of IJDC on cars over 200 whp.
Are there logs to prove this? Have people logged before conversion and after?
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Old 01-20-2008, 09:41 PM   #53
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You're putting way to much time into a 5 minute mod Sam.
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Old 01-20-2008, 09:51 PM   #54
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Quote:
Originally Posted by Ben View Post
I ran without those spacers for a while. Just don't tighten the rail bolts down too hard upon re-installation.
I tried doing this and my car hemorrhaged fuel all over my garage when I started it up. Mazda sells the spacers for el cheapo about $7?

I run a dual EGT gauge with sends in the manifold (BEGI type 5) about 1.5" away from turbo inlet, with one at cyl #1, other at cyl #4 side. There is typically a 50-100 degree delta between the two sends. For the record I see 1100-1200F at cruise at 70mph. 1100F at 60mph 1200 or so at 80mph, 1500 and rising on a good WOT 4th-5th gear pull

I am running stock fuel rail with 750cc injectors and 12psi w/ gt3071. I bought a FFS dual feed rail and will eventually set it up and see if the temps match up. If the Hydra could trim by injector i suppose this wouldn't be an issue but oh well.

Last edited by Faeflora; 01-20-2008 at 10:05 PM.
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Old 01-20-2008, 10:07 PM   #55
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100 degree difference between two sides of the manifold. Thats a big difference.
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Old 01-20-2008, 10:08 PM   #56
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You're putting way to much time into a 5 minute mod Sam.
Its principle.
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Old 01-20-2008, 11:30 PM   #57
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Yes bad example about the financing, but I understand what ur saying...But I stated my reasons, my opinions & thats the way I went. No one seems to have any hard evidence either way, and theres no downsides to doing it, coupled with the fact that its being recommended not only by credible vendors who make money, but being recommended by experienced people who arent making a penny, or costing u a penny....

Unless someone can prove its actually bad in some way, then Ill take the word of the vets plus the theory..
Kinda like u guys are the prosecuters, and the mod is crim defense. Again, this is MY opinion, and nothing more...
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Old 01-21-2008, 01:18 AM   #58
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Heres a question. Whats the size of the bore on our fuel rails?
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Old 01-21-2008, 10:07 PM   #59
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If someone is really good with numbers and has time, you can figure out the pressure loss across the fuel rail using this.

http://www.efunda.com/formulae/fluid...e_friction.cfm
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