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Old 12-01-2007, 10:37 AM   #41
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Quote:
Originally Posted by TunerToys View Post
To figure out the internal volume of the rail...

(yes I realize this will not tell you internal diameter exactly, but you can get close, if you roughly know the length of the rail.)

If you have it off the car...

Plug all the holes but one.
Fill it with water.
Dump the water into something graduated.

Using the formula to calculate the volume of a cylinder, put in length of the cylinder, and volume of the water, to solve for diameter of the cylinder.

You should then be pretty close on both volume and diameter of the stock rail.

Craig
um look up i already calculated it. 23.895cc it's actually really easy if you look at the end, no need to cut it. I don't really know of any calculations to do that would tell you exactly if it supports sufficient flow. the only thing i found is flow through a pipe and it measures pressure loss. this rail is roughly equivalent to a .4" diameter round tube aem sells a .5" rail and they say it's good for 1000hp. I did some rough guesses and pressure losses were around .03psi with flow may more than our fuel pumps can flow. So i'm thinking uprgading the fuel rail is worthless. looking at the rail the only logical thing i can see possibly being worthwhile is to enlarge the inlets and outlets.
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Old 12-01-2007, 10:48 AM   #42
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hmm so now we come to the question of fuel delivery to the rail to see if the 5/16 lines are the main restriction, or the rail given that some of us use up fuel at the rate of aproximatley 33 of so cc/sec I wonder if there is insuffecient flow somewhere. Maybe if we steped up to 650's or so at 85 or so %DC 36.8 cc/sec. But loki chad etc are the engineers not me so
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Old 12-01-2007, 11:04 AM   #43
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Quote:
Originally Posted by cjernigan View Post
I don't think the formula for a cylinder comes into play when calculating volume of square tubing though. Good idea with the water.
Dah, keep for getting I'm not dealing with Hondas. Pretty sure that this can be adjusted for volume of a cube/rectangle.

Sorry Mach, was so excited about posting the idea, I didn't see where you had already solved it.

Craig
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Old 12-01-2007, 11:06 AM   #44
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Quote:
Originally Posted by magnamx-5 View Post
hmm so now we come to the question of fuel delivery to the rail to see if the 5/16 lines are the main restriction, or the rail given that some of us use up fuel at the rate of aproximatley 33 of so cc/sec I wonder if there is insuffecient flow somewhere. Maybe if we steped up to 650's or so at 85 or so %DC 36.8 cc/sec. But loki chad etc are the engineers not me so
In addition to flow in general, aren't there some balance problems with the stock single feed rail? I though this was the basic reason for going with a dual feed, if if it is a modified stock rail.

Craig
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Old 12-01-2007, 11:08 AM   #45
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Yes the #4 is past the stock fpr and as a result gets starved for fuel sometimes but the dual feed allows alot more even distribution.
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Old 12-01-2007, 11:17 AM   #46
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Guess we're back to doing our own dualfeeds then.
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Old 12-02-2007, 01:11 PM   #47
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Looks like it might be possible to supply a Billet Rail for $100. You could run it as a single feed, or a dual. I'm heading to the PRI show this week, and then we will discuss it when we return.

ETD is also working on a few other new products for the Miata community.
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Old 12-02-2007, 01:50 PM   #48
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okay heres my take on it and this comes from long years of toil under subaru bonnets with the fuel rails above the hot block and crossing over the block and various water pipes etc etc

its all about the heat in the fuel
the fuel is circulated multiple times from tank - rail - tank and back until its consumed - each time it picks up "heat" from the pump / hot engine components and if you subject fuel to heat you will see that from 40 degree celsius it starts to want to vaporise really really easily, I think the ultimate solution is to protect the fuel from heat and you dont need rails

I think were aftermarket rails come into solving this problem is that when the fuel flows from a small area - ie the std lines to the aftermarket rail - there is a change in volume and/or pressure - there is a law in physicis for this, I just forget its name at the moment and when the fuel enters the rail - it loses the urge (if in temp range) to vaporise - as opposed to the small std fuel rails where it attempts to "vaporise" due to temp and the injector tries to inject a liquid that wants to be a gas - this is where it goes "lean" in my mind - its not about insufficient flow its about a liquid under pressure, where the pressure is preventing it becoming a gas but when it is released by the injector instead of atomising the way we expect it vaporises and bingo it is "lean"

This may not be the best or most eloquent explanation but I cant think of another way to re word it ! so read it a few times and let me know your thoughts on it ?
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Old 12-02-2007, 06:41 PM   #49
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you're wrong
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Old 12-02-2007, 08:47 PM   #50
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I'd say that the heat can only HELP with vaporization, which if anything will improve power.
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Old 12-03-2007, 06:07 PM   #51
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has nothing to due with temps. it's all about volume it can support. of course my theory is if you don't have larger fuel lines, then it's not as critical.
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Old 12-03-2007, 07:43 PM   #52
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You don't want the fuel in the rail to be warm or hot. Cold is going to make the most power. Remember cool cans on carb'd engines?
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Old 12-07-2007, 02:12 AM   #53
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OKay guys, we have picked up a 90-93 complete intake manifold (injectors, fuel rail, etc is still on it. We also have a Vishnu rail for the same model years on the way. We are looking at several different ways of solving the lean condition on the stock fuel rail.

We are looking at three options.

1. A kit for adding the second feed to the opposite end of the stock rail.
2. An extruded rail kit that does not incorporate the regulator
3. A complete billet solution that would incorporate the regulator.

I think we'll be able to do the sub $100 solution for you guys with the extruded solution, but need to know if you guys are willing to use an external regulator with an aftermarket rail? Not needing to incorporate the regulator will cut costs for us, and allow us to hit the price point you guys want. Of course it will complicate the installation for you guys.

If the regulator must be reused, then our production quantity for the billet solution will have to go way up to make the price point. If we have to make a 1000 of these things to get the price point down, it may exceed the cost we are willing to invest in getting thos product done. I'm not too excited about having 1000 of these on the shelf if we are only going to sell a few a month.

We may be able to incorporate the stock regulator into the extrusion, but must look further into this option. It may not be feasable.

Please let me know what you guys think.

Thanks from Craig
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Old 12-07-2007, 09:51 AM   #54
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What external reg are people using? How much is it? Does it justify the additional cost of incorporating the stocker into a billet setup? What are the advantages of the external reg over a stocker?
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Old 12-07-2007, 09:53 AM   #55
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Option 3 would be most cost effective for us, even if the rail costs a little more, as we wouldn't have to purchase an external regulator.
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Old 03-22-2008, 09:36 PM   #56
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Sorry to bring this thread back after three months, but we are happy to announce that option 3 above is now a reality. Check out our post in the vendors classifieds! Tuner Toys High Flow Fuel Rails for 90-93 Miatas! We are doing a special introductory price for you guys, since many of you provided input on how to make this a product you guys would really like.

Craig

Teaser pic...



Thanks Guys!
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