fixed.

Again, agreed. What a delightfully well thought out post.

Thanks. I think I should be good, the stockers are about that size, anyway, at ~250ccs, and I have one or two sets of 300-315cc injectors somewhere. I *think* they fit into the miata rail. But I'll let you know if I need them. I want to find something really big to push this to the limits (750cc+), but I have my own 550's though they are a huge pain to get out.


This is a real common mistake I think a lot of people make. I've been in a car with 5-10 x stock power. It's not a trivial thing. We're really not pushing the cars that hard.

Take my 2000. 144 crank hp stock (loses are about 35-40 hp, which is essentially constant), or ~110 at the wheels.
Figure it's not too bad to imagine 250 wheel HP. Add the 40 loss back in and you get 290 crank.

That's really only 2x the power. Yes, it's more. But 2x is a pretty common margin used in engineering. We're likely just on the border of what many parts are designed for anyway. For an ultimate performance or ultimate effeciency vehicle, yes, those limits are much closer to "stock", but for the miata, remember, even a 350 whp car is more like 2.5x.

gtg!

 

Very good point.

I wonder if the mazdaspeed protege uses the same rail, about the same time period.

 

I wonder what the MSM uses.....


Anyway, does anyone have any *high flow* injectors to loan for the test?? Ideally something silly, to lie this to bed. 750cc or more, but anything will do - I don't want to pull my mani just to get to my 550's....

 

STi's usually get up to around 750cc/850cc injectors when doing turbo upgrades, seem to recall WRX/STi is listed as a direct fit

 

I believe what Abe meant to say is "Which one of you bastards is going to send us a set of 750+ injectors for free, so we can run this test and provide the results to all your lazy asses?"

IOW- we're not buying injectors just to do this test.

 

I'd be willing to loan out some 550cc injectors as long as I get them back within a couple weeks. I'm going to send them out to be cleaned on friday so it wouldn't be till next week.

 

I seem to recall FM saying that the MSM fuel rail is a bit larger than a normal NB rail. Here it is in the second post: (http://www.mazda-speed.com/forum2/in...ic,9358.0.html)

So maybe Mazda didn't think the NB rail had all that much headroom.

 

I was thinking there might be a local group of STi owners (e.g. NASIOC or i-club), within which someone might have a set of 750/850cc injectors, that they'd be willing to loan for testing. Hell, they could be selling them, and agree to "free bench flow testing"...

I mean seriously, even the people around here who aren't cheap asses, I didn't actually expect anyone to buy a set, just to do a maximum theoretical test... (Then again, for the number of people spending $200 for a fuel rail that doesn't come with fellatio...)

 

I'm still floundering around trying to figure out two things: real evidence that the stock rail has a problem, and if a replacement is better or worse.

So far, no evidence either way.

In my op, the real issue is how big, and how far away is the reservoir that the injector draws from for each squirt.

In that regard, four separate reservoirs would/might be the answer.

 

Corky,

Until this moment, I thought my respect for you was honest and true, based solely on your technical talent, that it was for that virtue alone. I've been reading 'Maximum Boost', re-reading the formulas in the first part, hoping I'll suddenly develop an understanding of physics and fluid dynamics, exclaiming "oh, that makes sense!" (while sober). Spending long nights drooling over the latest and greatest BEGI designs, always surprised that a business could be operated, with the singular goal of selling products on their qualitative improvements alone.

But now I see the evil underbelly... all this time, you've been waiting for that perfect opportunity, that mass-marketed piece that's going to make you rich...

You've planted the seed, waiting, watching the people on the forum start to build interest, waiting for their desire to hit a fervor pitch, manufacturing a few prototypes for those eager souls suffering from a burning sensation in their pocket...

And then, it will have begun. The BEGI MPFRSS! Yes, the Multi-port fuel reservoir supply system.

Who knew that we'd pull back the curtain, to find you at the helm, a gleam in your eye as a dastardly piece of marketing brilliance pours forth!

Oh, what a frightful day...

-mack

 

well, that was random?

 

Or a fatter rail in the worst case scenario.

 

Corky,the best thing to do is fab up a bigger dual feed fuel rail or purchase one and conduct all the test and come back with your conclusion on what you found.

 

Well, I have a friend (TeamPlur) who has some ~60lb/hr injectors (five, in case one sucks) to lend, but they are for an Audi, so I don't know if they will fit the stock rail. I do think this is reasonable, though I really with I could find some EVO numbskull or ethanol guy with some 1l/min injectors (or 1600's like my buddy put in his RX-7) to answer this one once and for all.

And with the generous offer of a pump and a rail/reg already mentioned in this thread and Adam (na90peewee or I forget?) has another pump (possible stacking experiment).. It looks like I might have enough to get this all together. Now it's just a question of talking the way-too-honest girlfriend from borrowing some graduated cylinders from her lab and buying enough beer to make this all worth my time.

And getting Joe in to direct the cinematography, be the butt of various jokes, etc.

I was hoping to do this next weekend (i.e. ~10 days) but I'm not sure what parts we'll have on hand. If you've not yet sent out the injectors, we could flow test them while we're at it, tell you if they are even. :-)

Oh, and Joe (or ?), do you have a fuel pressure gauge? Yes, I own my own leak down tester, engine stand, micrometer set and no fuel pressure gauge.

This may be the most intelligent thing ever said on this board: We don't know, so we're not going to spend $400 on it.

Corky,
I did the quickest of calculations on this, and came up with ~(0.42 cm)^3
I figure the rail is probably wider than that inside, meaning you're really taking a cube smaller than the diameter of the injector port in the rail. And that's for 550's, good to maybe 350 whp?

If I were interested in a more reservoirian rail, I might just use rubber lines, assuming their contractions would keep pressure up during the fuel delivery. I've heard some OEM's do that, having hoses to each injector, and I think it's a pretty good solution as it addresses any real concern of any rail.

I still think the whole thing is a non-issue, the restriction through an injector has to be huge, 1,000x the main rail if not 1,000 times that. So I'll drop in some injectors, flow them for 1 minute (PULSED) and see what I get. I'm much more interested in dynamic response and the dampeners than anything else.

Personally, on my own car, I'm tempted to pull the fuel "damper", T in a second feed into that port, and hope the reflections off the diameter change at the end hurt me less than the extra fuel. Easy mod for my returnless system.
Anyone have any thoughts on that?

 

I'm excited about the test. Make sure and play some dirty rap or whatever during the video...something really stupid.

 

I'd love to see the test with some 1600cc injectors and only 1 feed.

I purchase a Dual Feed for Piece of Mind and Insurance in most cases, but can 100% confirm that I have been able to add more timing in the past due to installing a dual feed over a stock. (Old Vishnu on my 95 Engine)

 

My bet is that they will. And I think 60lb injectors would be very good for the test- that's equivalent to about 630cc, which is definitely at the upper end of the sanity scale for a street-driven Miata. Any bigger and I think we run the risk of out-flowing the pump.

That was my plan. One at a time, put each injector into the #1 position on the rail and run it steady-state for a set time period, then compare. Even if they're not even, that test will give us a correction factor for the final test.

I do not. Best I could do would be to use one of my compressed air gauges- it won't give us ideal resolution, but it should be adequate for looking at trends. Frankly, I was planning to just let the stock fuel pressure regulator do its thing and let that be that. If the per-injector flow changes from the first (single-injector) test to the final test, then we know there was pressure drop.

If the test is about restriction and single-feed vs. dual-feed rails, I still think a steady-state test will be more important.

 

I can offer some evidence that the dual feed rail helps;

I live near sea level, this past winter on colder days, -5 to -10 deg. my miata was knocking a bit near peak power, since this was happening at cold temps, I suspected that it was due to the fuel system being maxed out, and as a result the fuel flow was getting uneven between cylinders. AFRs were in the range of 12.5:1 while this was happening. I changed to a dual feed rail and haven't heard any knock since.

FM2 - 12 psi, Hydra, 550cc RC injectors, 257 whp on FM's Rototest, 256 whp on a local Mustang Dyno.

 

Normally Audi and VW use large O-Ringed injectors similar to ford. You might be able to change O-Rings and make them work for the test, I used to run 950cc Ford Injectors on my Miata and I used small Miata O-Rings and got a good seal. Later I had them spun on a lathe (Cut down the plastic) and then I had the piece of mind that they would not ever leak.

 

Testing four-digit injectors would be soley to eliminate the arguement of "you tested 630's, but I'm running 645's" crap. :-)

I've cut o-rings before out of fuel line, and it works believe it or not.

My roomate was telling me a common thing in the Dodge world was to run two pumps in series. You get a much higher flow at a given pressure, since each pump sees a smaller differential.

A Man. A Plan. A Canal. Panama.

I was hoping to get a gauge in the feed to the rail. Maybe I DO have one, I just have to look. I have a lot of crap. I think Adam might have one, anyway.


What worries me is that I think for the steady state, a small bleed won't be an issue. The pump can likely supply it. But if you're lowing the pressure right in front of the injector, just before it opens, you're going to have lower pressure there. Anyway, with 2 megasquirts, two jim stims, and a breakout board, I'm not worried.

There are plenty of people making unassuming claims that dual feeds help. This is what inspires me to test it.

In closing, I wonder if the things that are showing gains are:
Bigger pump (my guess)
Higher flow rail (next guess)
Dual Feed (doubt it)

I'm getting more excited about this test. Every time I hear it actually helps, I get excited. If someone has an aftermarket rail, I'd love to test it - including a test where we cap off one feed to remove the "dual feed"iness of it.