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Old 08-25-2006, 12:36 PM   #21
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hell i'll pick up a hose barb and a drill bit and tap today and do a write up this weekend
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Old 08-25-2006, 12:52 PM   #22
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hell i'll pick up a hose barb and a drill bit and tap today and do a write up this weekend
- if you could that would rock
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Old 08-25-2006, 01:37 PM   #23
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hell i'll pick up a hose barb and a drill bit and tap today and do a write up this weekend

Thank's that will be great.
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Old 08-25-2006, 02:06 PM   #24
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Here's a writeup:

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Originally Posted by Sirnixalot View Post
1. i'll pick up a hose barb...
2. drill ...
3.tap


I think the most important thing is to be sure there are no metal chips stuck inside the fuel rail after drilling/tapping. Another hard part is making sure the drilled hole is centered and the tap is going straight into the fuel rail. Depending how your particular Barb fitting is machined, you may have to tap pretty far into the fuel rail, and if you don't start the tap as parallell to the fuel rail as possible, you may dig pretty deep into one of the fuel rail walls. As with all pipe threads, tap a little then try screwing your fitting in to test the fit, then tap some more if needed. You don't want to tap too far or else you'll be screwed (haha). Still kinda minor but something to pay attention to...
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Old 08-25-2006, 02:34 PM   #25
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i understand what youre saying and thanks for the tips, not the first time ive drilled and screwed a hole :gay:
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Old 08-25-2006, 06:03 PM   #26
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Now that is interesting. I also a thread where the poster claimed that he was able to lower #4 egt 30 deg.

Seems like this mod is important and necessary.


Quote:
Originally Posted by brgracer View Post
This post made me do a lot more reading up on dual feed fuel rails and learned two interesting things from some old threads about people who did some actual dyno testing.

#1 dual feed stock rail (~$10) was just about as good as vishnu/FM/****'s for most applications on the dyno. Granted, the more radical the setup, the higher end stuff started to make some gains over the stock mod.

#2 More than just for safety, most people on the dyno were able to advance their timing a few degrees b/c of the dual feed rail and hence make more power. Interesting....
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Old 08-25-2006, 06:20 PM   #27
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30 deg isn't much (I don't think). 300 deg is huge.
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Old 08-25-2006, 11:21 PM   #28
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I agree it doesn't sound like much, but the data I saw was something like before mod cyls 1-3 were within just a couple of degs from each other, and cyl 4 was 30 degs hotter. After the mod, all cyls were within a couple of degs from each other. Maybe there isn't any short term gain, but I would think that over tens of thousands of miles, it would be important.

I wish I could find this data again...

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30 deg isn't much (I don't think). 300 deg is huge.
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Old 08-26-2006, 10:21 AM   #29
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Quote:
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I agree it doesn't sound like much, but the data I saw was something like before mod cyls 1-3 were within just a couple of degs from each other, and cyl 4 was 30 degs hotter. After the mod, all cyls were within a couple of degs from each other. Maybe there isn't any short term gain, but I would think that over tens of thousands of miles, it would be important.

I wish I could find this data again...
OH ok I see now
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Old 08-26-2006, 01:37 PM   #30
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Quote:
Originally Posted by Sirnixalot View Post
hell i'll pick up a hose barb and a drill bit and tap today and do a write up this weekend
Awesome... I've started bookmarking some of the threads I find useful information in for future use... if you do a writeup on you rail, I would be most grateful.
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Old 08-26-2006, 03:39 PM   #31
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Quote:
Originally Posted by Ben View Post
I wish I could find this data again...
Don't know if this is what you were looking for, but these two threads have some pretty good data info:

http://forum.miata.net/vb/showthread.php?t=15109

http://forum.miata.net/vb/showthread.php?t=9411
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Old 08-26-2006, 06:27 PM   #32
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i think the idea is that you can possibly run a little more timing a little less fuel since the cylinders are more balanced and the #4 cylinder isn't being pushed over the edge of safety while the others are fine.

here's mine with a brass barb on one end and fuel pressure gauge on the other. Not installed yet but will go in with my supra injectors

Last edited by Mach929; 08-04-2007 at 09:21 PM.
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Old 08-27-2006, 02:57 AM   #33
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sorry guys i wasnt able to get the stuff i needed to do this.

Preparing for what may be Hurricane Ernesto down here.
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Old 08-27-2006, 10:43 AM   #34
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Can we draw a conclusion here that most knocking in a boosted engine on a stock fuel rail is coming from the #4 because it's running slightly leaner due to less fuel pressure. Can you measure knock per cylinder?

Earlier Ben said he found a 30* temp delta in that cylinder. Based on my knowledge of combustion chamber temps at ignition, that wouldn't seem to be a big difference. Somebody said the temp difference is more than likely caused by the coolant around that cylinder being hotter than the others.

The real test would be to measure pressure individually at each injector at various boost levels and rpm and following the decrease in press from 1-4 along the rail... but I don't think any of us has the instruments to accomplish that.

You would also have to have a baseline from a stock engine.
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Old 08-27-2006, 10:55 AM   #35
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Quote:
Originally Posted by samnavy View Post
Can we draw a conclusion here that most knocking in a boosted engine on a stock fuel rail is coming from the #4 because it's running slightly leaner due to less fuel pressure. Can you measure knock per cylinder?

Earlier Ben said he found a 30* temp delta in that cylinder. Based on my knowledge of combustion chamber temps at ignition, that wouldn't seem to be a big difference. Somebody said the temp difference is more than likely caused by the coolant around that cylinder being hotter than the others.

The real test would be to measure pressure individually at each injector at various boost levels and rpm and following the decrease in press from 1-4 along the rail... but I don't think any of us has the instruments to accomplish that.

You would also have to have a baseline from a stock engine.
Like you said, no one here has the setup to really measure all the variables, but I think that you are probably right that cylinder #4 runs hotter b/c the poor coolant circulation flow rather than b/c the fuel flow. That being said, the dual feed mod is much easier than the coolant reroute mod.

Anyone have the funds, time, and motivation to run individual cylinder egts and experiment?
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Old 10-09-2006, 04:25 AM   #36
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I know this is an old thread, but I just went through a few threads on the same topic on miata.net and a few people with experience noted that the fuel distribution on a fairly stock mx5 has very litte to do with cylinder #4 problems. And like bgracer said, it seems like poor coolant flow is to blame far more than fuel delivery. On the other hand, it is a worthwhile mod because it is highly unlikely to cause a negative effect if you are careful with the fittings, and likely will net a slight improvement which increases as fuel demand increases.

With that said, any miata running 200whp or more would be best doing a coolant reroute than a fuel rail mod, but both could be better. To give an analogy, you couldnt have prevented the WTC from falling by opening a starbucks next door, but if you did, at least the people running could get some coffee to give them a boost to get the ##$% out of there quicker.

(hope that dosnt offend anyone, it was the first thing i thought of)
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Old 10-09-2006, 09:47 AM   #37
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I argee you are going to have much better results from doing a coolant rereoute, than by the duel feed. But like a lot of others are saying, every little bit helps, might as well not risk going lean at #4 and even the flow out a bit. Which is the main reason I did it, plus it took a whopping 30mins.
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