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Old 02-03-2010, 11:19 AM   #61
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Originally Posted by JasonC SBB View Post
I find it believable that finer atomization is better, but I want to question it.
Seeing that there are so many papers on WI, there might be something that actually tests it..
BTW I also asked that same friend of mine if he knew of any good papers on WI, perhaps published in SAE or the like. He said there is not much there since for the most part the OEM Engineers have not been playing with it, and neither has the racing community. Plus in racing if someone finds a performance advantage they are usually motivated NOT to publish it for obvious reasons. That is why a lot of the WI information is from the WW-II era piston engine performance development like the article that Joe linked to. I suspect that the information was closely guarded during the war, but was released once everyone switched over to jet engines and it did not matter much anymore anyway.
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Old 02-03-2010, 11:24 AM   #62
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So I had my R&D gas engine Engineer buddy take a look at the manifold and he does not see any obvious problems with the gutting that would cause a flow imbalance between cylinders.
Is his name Mr. Flow Bench?

I have a gutted manifold as well but I decided not to put it on because of what I said. I don't want stupid **** to happen to my motor because of stupid ****.
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Old 02-03-2010, 11:41 AM   #63
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Even when I had a single, much larger nozzle on a much longer run of tubing, it was clear that the mist at the nozzle was still pulsing strongly in response to the pump cycling on and off.
Have you tested this at the typical injector pulsing frequencies of 4000-6000 RM (30~50 Hz)?
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Old 02-03-2010, 12:41 PM   #64
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WI was used in F1 during the turbo days. Granted the didn't even turn it on until like 30PSI, but they were running like 60+PSI.
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Old 02-03-2010, 01:27 PM   #65
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Originally Posted by faeflora View Post
Is his name Mr. Flow Bench?

I have a gutted manifold as well but I decided not to put it on because of what I said. I don't want stupid **** to happen to my motor because of stupid ****.
I would listen to this post before trusting sound engineering judgement...
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Old 02-03-2010, 01:32 PM   #66
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Is his name Mr. Flow Bench?
No I think that is your name? Seriously, what is the basis for the assumption that the manifold is going to be a problem? I'll wager that my guy knows more about manifold design than most of us here. So his assessment that it is OK carries more weight than the assessment that it is not OK, at least until someone comes up with something better than changing the stock configuration = doom and gloom.

So, in the mean time, let's keep the manifold aspect of this out of the discussion unless it relates to the WI.
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Old 02-03-2010, 01:34 PM   #67
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Have you tested this at the typical injector pulsing frequencies of 4000-6000 RM (30~50 Hz)?
Not yet. Have you?
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Old 02-03-2010, 02:05 PM   #68
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Good news on the manifold. I'd just go for it, despite the naysayers.
agreed, thanks

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I forget what you're using for knock protection...consider trying Jeff's new device?
The Adaptronic has built-in knock sensing and retard. Just wire in the knock sensor. However the tuning aspect of it is nothing beyond threshold versus RPM. I think Jeff's filter circuit could be helpful at the least. I also had a knocksense with the MS that seemed to work well.

EDIT: OK nevermind, found the thread assuming you mean this one:
https://www.miataturbo.net/forum/t41877/
Yep I already did something like that a while back using a cheap radio shack amplifier.
https://www.miataturbo.net/forum/t22322/
I can either listen in on its speaker, or I send the output to one of my stereo inputs, where I can apply 16 band equalization. Boosting the upper midrange frequencies seems to make it easier to hear knock. In fact, I installed two knock sensors on the motor. One for the Adaptronic, and one for the electronic det can. That way the input impedances do not interfere with each other.

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On the one-way(check) valve switch...you've got the right idea, I've just yet to find one in 12V. Tried Grainger and McMaster...need to look around more. If we find one I think I'm going to order 20 of them as they could be applied to ANY setup. You'd just need 4, and a lot of wiring, for yours.
Agreed. I like the idea so I will let you know if I find them anywhere, though I would have looked at the same places you did for starters. Maybe Omega though their pricing tends to be high.

Last edited by ZX-Tex; 02-03-2010 at 02:19 PM.
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Old 02-03-2010, 02:55 PM   #69
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Here is a flow switch from Omega that would work though the price point is too high
Liquid Micro-Flow Switches
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Old 02-03-2010, 03:19 PM   #70
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Originally Posted by JasonC SBB
Have you tested this at the typical injector pulsing frequencies of 4000-6000 RM (30~50 Hz)?
Not yet. Have you?

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Not yet. Have you?
Of course not. If I had, I'd have stated my results instead of asking stupid questions.
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Old 02-03-2010, 03:22 PM   #71
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Re: knock - the miata's main knocks frequency is 13 kHz in my testing. However I recorded knock off-idle. If someone has knock recordings under heavy load I would like to analyze those waveforms.

I posted a 2nd order bandpass filter schematic centered at 13 kHz.

What does Jeff's circuit look like?
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Old 02-03-2010, 03:47 PM   #72
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I think it is just an audio amplifier. I went through that thread quickly however. I think the filter I was remembering is yours.
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Old 02-03-2010, 04:03 PM   #73
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Do they make an electronic check valve? Basically a valve that closes or opens a circuit when it's activated? I would think you could tie this in with the PWM so that anytime the PWM is active, it would make sure the check valves are opening. If they aren't opening, then the nozzle is clogged causing a high back pressure. I would think that would be much simpler and cheaper than a flow meter (assuming it exists).
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Old 02-03-2010, 04:48 PM   #74
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Quote:
Originally Posted by ZX-Tex View Post
I think it is just an audio amplifier. I went through that thread quickly however. I think the filter I was remembering is yours.
Correct. I left filtering out of the mix due to the fact that I'm trying to keep cost low and the price of small batches of custom made PCBs is a bit prohibitive. As an "entry level" knock detection device, an amp works suitably well. Worlds better than not having anything at all, but not as nice as a phormula or a gizzmo.
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Old 02-03-2010, 08:13 PM   #75
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Originally Posted by TrickerZ View Post
Do they make an electronic check valve? Basically a valve that closes or opens a circuit when it's activated? I would think you could tie this in with the PWM so that anytime the PWM is active, it would make sure the check valves are opening. If they aren't opening, then the nozzle is clogged causing a high back pressure. I would think that would be much simpler and cheaper than a flow meter (assuming it exists).
I think what you are describing is the same as what gospeed is suggesting.
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Old 02-03-2010, 08:14 PM   #76
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Originally Posted by Jeff_Ciesielski View Post
Correct. I left filtering out of the mix due to the fact that I'm trying to keep cost low and the price of small batches of custom made PCBs is a bit prohibitive. As an "entry level" knock detection device, an amp works suitably well. Worlds better than not having anything at all, but not as nice as a phormula or a gizzmo.
Agreed. I am happy with my electric det can setup. Reliable, sensitive electronic knock detection is tough, but it is pretty easy to hear it with this setup. It cannot be on all the time of course but for occasional use, like for tuning, it is great.
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Old 02-04-2010, 08:41 AM   #77
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I think what you are describing is the same as what gospeed is suggesting.
Yes, exactly the same, yet still different from the $200 valve you posted. That looks to have enough resolution to serve as a low flow meter, it's really just another flow meter. I guess you could use something with a turbine wheel in it, but they will all be just as expensive.

I'm thinking of a contact-based ball type one-way valve that simply says "hey dummy, there's no flow here" or not. We don't care so much about knowing the actual flow rate, as that's all calculated ahead of time, and dependable as long as there are no busted lines or clogged nozzles.
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Old 02-04-2010, 01:03 PM   #78
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There are things like paddle switches but they are too large, at least the ones I have seen. That device is not quite a paddle wheel flow meter in that it does not measure flow rate. It just uses the movement of the wheel to trip a switch. I agree it is still too expensive though. I threw it out there as more of an 'FYI' than a 'here is something'.

I'll see if I can find something else. There are so many practical minded geniuses where I work that somebody may know of something offhand that would do the job. I get a lot of those "Oh yeah I know just what you need. Go here and get this..." eureka moments courtesy of my colleagues. The mechanical requirements are so simple there has to be something cheap out there somewhere.

For the PWM variable flow usage, I would basically have to set it at the lower flow threshold so that when I am running at 20% DC (or whatever the minimum flow rate for good atomization is) it will let me know if I have an obstruction. It would basically be a necessary but not sufficient indicator of proper flow. Still very useful though.

Last edited by ZX-Tex; 02-04-2010 at 01:25 PM.
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Old 02-04-2010, 01:26 PM   #79
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Originally Posted by ZX-Tex View Post
I think Joe's paper was in regards to water injection? Joe I think you linked to the wrong paper BTW
Yes, I did. I fixed the link, and here it is again: http://ntrs.nasa.gov/archive/nasa/ca...1993093245.pdf


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Originally Posted by JasonC SBB View Post
Note how Joe mentioned that when he turns off the flow, it takes a second for the flow at the nozzle to fade away.

The way to prevent this is to have some short, rigid piping from the HSV to the nozzles.
In a perfect world, I'd think you'd have one HSV per nozzle, with the nozzle screwed directly into the HSV. Failing that, you'd use semi-rigid metallic tubing.

HOWEVER, I'd love to see ZX do a test on his system, while it's still out of the car, where he drives the HSV at various duty cycles at its intended operating frequency, and makes two observations: First, does the volume of water actually emitted match the predicted flow based on the PWM table, and second, is the atomization quality consistent even at low flow rates? If both of these tests return true, then party on. If not, then I'd make the case for re-testing withrigid metallic tubing and compression fittings.


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Assuming Aquamist uses the same polypropylene(polyethylene?poly-something) hose that everyone else uses I doubt it expands outward much at all.
(...)
The reason water continues to come out is because the water in the hose after the valve will drain out from suction and/or gravity, pressure equalizing to atmospheric...
This argument is inconsistent.

I did this test on the bench with everything level, so there's no vacuum or gravity at work. And it wasn't just a few drips- the nozzle was very clearly spraying after the pump was shut off. You nailed it when you guessed "pressure equalizing to atmospheric", however you need to figure out the reason that there was any pressure to equalize. If the tubing was in fact non-expandable, then as soon as the pump shut off there's be no more pressure to equalize. Water is non-compressible, at least, not at the pressures we're working at. The reason there was pressure was that the tubing was expansing slightly and acting as a pressure reservoir. Someday I'll measure it with a micrometer.

Oh, and the tubing is nylon.


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Originally Posted by ZX-Tex View Post
BTW I also asked that same friend of mine if he knew of any good papers on WI, perhaps published in SAE or the like. (...) I suspect that the information was closely guarded during the war, but was released once everyone switched over to jet engines and it did not matter much anymore anyway.
That's very true- this stuff was classified back in the day. There has been some recent work done on the subject (I've got one relatively modern SAE paper on it somewhere) however you're correct in that WI sort of fell out of vogue for some reason.

Like I said, I've got a whole library of this stuff, I've just been too damn lazy to collate it and publish. One of these years...
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Old 02-04-2010, 03:00 PM   #80
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I did this test on the bench with everything level, so there's no vacuum or gravity at work. And it wasn't just a few drips- the nozzle was very clearly spraying after the pump was shut off. You nailed it when you guessed "pressure equalizing to atmospheric", however you need to figure out the reason that there was any pressure to equalize. If the tubing was in fact non-expandable, then as soon as the pump shut off there's be no more pressure to equalize. Water is non-compressible, at least, not at the pressures we're working at. The reason there was pressure was that the tubing was expansing slightly and acting as a pressure reservoir. Someday I'll measure it with a micrometer.
Ok. Assuming everything you stated happens with all setups, all I see is a positive more so that a negative. Assume the pump is running, and the HSV just went into the closed part of its cycle. Since the tube acts as a pressure reservoir the nozzle continues to output a fine mist under near full pressure for the few ms until it is open again for the next cycle. All it is doing is extending the spray to be continuous instead of truly pulsating. The only way to fully stop any pressure reservoir and leaking would be to have not just a hard line but also a check valve right at the valve as well. Even with a hardline eliminating the effect you speak of, without a check valve water will be siphoned off after the pump cuts off. It is not really a big deal for that though. I will agree that you want to maintain max pressure at all times though and minimize any dips.

A true HSV that is like a fuel injector would be able to cycle around 200Hz. Do you think that the pressure drop over the maximum 5ms time period until the next cycle is that significant? My guess is that it is not.
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