My Intake Pipe Design, Stalling Issue And Lean Popping

[rob82]

If the gauze is still on both sides of the AFM, orientation wont matter shit. Esspecially not at idle.

[Rolls]

If you change all the surrounding pipes especially the angles near the afm it could bend the afm signal giving richer/leaner tune.

[rob82]

If you change all the surrounding pipes especially the angles near the afm it could bend the afm signal giving richer/leaner tune.

The purpose of the gauze is to straighten the flow. The angles before the AFM will have an effect at high flow rates but not at idle or light load. The angles after the AFM will have an effect also but only when the air reverts on closed throttle.

[SargeRX8]

Ill try flip it around when I get the pops on idle. Its got both mesh things intact and it has the flow arrow facing the turbo.

[GTSBoy]

The purpose of the gauze is to straighten the flow. The angles before the AFM will have an effect at high flow rates but not at idle or light load. The angles after the AFM will have an effect also but only when the air reverts on closed throttle.

Not true. The gauze will put up a tiny pressure drop which will re-distribute maldistibuted air a tiny bit better. But in reality the mesh is there to protect the delicate sensing elements from flying rocks and the screwdrivers of hamfisted bush mechanics.

If you wanted to actually straighten the flow you would have to try much much harder than using a little bit of gauze. Trust me, I know this shit backwards.

[Rolls]

Just out of curiosity what do you do GTSBoy?

[Room42]

He is an internet troll. http://www.skylinesaustralia.com/forums/topic/377944-manual-to-auto/

On the subject of air flow meters, the wire mesh is there to create a laminar flow which is basically streamlining the air to get a more precise reading.

[rob82]

Not true. The gauze will put up a tiny pressure drop which will re-distribute maldistibuted air a tiny bit better. But in reality the mesh is there to protect the delicate sensing elements from flying rocks and the screwdrivers of hamfisted bush mechanics.

If you wanted to actually straighten the flow you would have to try much much harder than using a little bit of gauze. Trust me, I know this shit backwards.

I believe the gauze is nissans attempt to straighten the airflow hence the reason it is on both sides of the airflow meter. I think you would be surprised the difference fine mesh makes at low airflow rates. And yes I know what is involved in correctly metering air as I have calibrated at an oem level for Mazda. You would not believe how sensitive rx8 airflow meters are!

[DVS JEZ]

Nice read^^^Room42

[Room42]

Nice read^^^Room42

A bit silly hey Jez?! Oh well there are all types I spose.

[GTSBoy]

Just out of curiosity what do you do GTSBoy?

Chemical/Process/Combustion Engineer. Internal/duct flow aero being a speciality. I do aerodynamic modelling.

I can tell you for certain that unless a perforated grid/mesh type flow straightener puts up a seriously high (like at least 10% of the total pressure) restriction, it will do absolutely nothing to straighten or even out the flow. For the hole size in that mesh, you'd probably need to reduce the number of holes by a factor of 10 to start working as a flow straightener. I'm just guessing at the amount of reduction here - it might easily be higher.

If that mesh was located at the inlet of the AFM and the AFM was located immediately after an elbow, then the flow would crowd the outside of the elbow and there would be a substantial velocity profile across the AFM, with high velocity corresponding the area downstream of the outside of the elbow and low velocity, possibly even turbulent eddies caused by separation of the flow corresponding to the inside of the elbow. The sensing element will measure whatever is going past the mid-line of the AFM, however representative or non-representative that velocity is. But the mesh will be essentially transparent to the velocity profile - it will not cause a change in the bias of the flow by more than a couple of %. And the fact that there is another mesh on the outlet just goes to show that the only reason it is there is to stop mechanical damage to the sensitive stuff inside. Because there is no way that you would install a flow straightening device downstream of your sensing element. It makes no sense at all.

Flow straighteners need to consist of something perforated to put up a significant pressure drop (which is intended to work like a bunch of nozzles which convert the built up static pressure upstream into a bunch of evenly distributed and same-velocity jets), followed by a device to knock out swirl, which is most easily thought of as a bundle of drinking straws. Such a bundle will knock swirl out because any swirling flow that enters the bunch of little flow paths will then be trapped inside each flow path and will have no choice but to come out with no swirl at the other end. Well, no gross swirl across the whole flow, there may be residual swirl in each little chunk coming out of each straw. And if you are really serious, then you might have another perforated restrictor plate downstream of the straw bundle.

For a simple, single element flow straightener to have any effect at all it must have some thickness in the direction of the flow - like the straw bundle above. Compare the wire on the Nissan AFM

http://www.nissansil...10624_thumb.jpg

which has almost no thickness in any dimension, including the direction of flow, against the sort of flow conditioners that actually are intended to do some flow straightening in other AFMs, like this one

http://img261.images...maf01medrw7.jpg

or this one

http://t3.gstatic.co...3nm93Z7N9pq1QxA

(note that the first EVO one is just a small patch and that the second one covers the whole inlet end - but only the inlet end).

These are made from a honeycomb sort of punched mesh (not a wire mesh) that has a little thickness in the direction of flow. These will do a tiny bit more flow conditioning than the gauze on the Nissan ones. It's actually necessary to do some flow conditioning on these vortex counting meters because they rely on aerodynamics to work, whereas the Nissan ones are just hot wire anemometers which will work in any sort of aerodynamics, as long as they are calibrated for the aerodynamics that they are in.

And that is why Nissan ones are located immediately downstream from a bellmouth drawing from the relatively open volume of the airbox. The hope and intention is that the flow into the AFM will be relatively even just by the nature of the inlet condition. But even then it doesn't matter, because Nissan just go and tune the ECU according to what the AFM reading is in that aerodynamic situation and as long as it is repeatable on the same installation (ie all such cars) then it is fine.

Edited October 1, 2011 by dan_the_man

[Room42]

Also, unlike Room42, whose name I am assured refers to the capacity of his arsehole, I actually know what I am talking about.

Point proven. Internet troll. Anyone can cut and paste from wikipedia and hope to fool people. I have seen a lot of your posts in other peoples threads and you troll them too. That shit in your signature is about me. You've been reported once and now twice. Like I said last time SAU is for fostering goodwill and friendship among members. You are clearly doing the opposite of this. I have paid to be here and have been open and honest in my profile and I sure as hell don't go around abusing people like you do. Its only a matter of time before you get banned.

[GTSBoy]

Room42,

If you can find what I've written anywhere else on the internet, then good luck to you. This shows more than ever that YOU have no idea what you're talking about. I said up front that I know this stuff backwards. What is your professional background? When was the last time you designed equipment that sold for hundreds of thousands of dollars?

Now, if you want to keep going back to the glory days of your imagined argument triumph over me in the manual to auto thread, like you seem to love to, you will note that I first up gave a perfectly valid suggestion, which was not to ruin a manual car, when you could start with an auto car. Then I re-inforced said suggestion, pointing out that one could move from existing manual car to an auto equivalent for little cost. I also mentioned that I thought that autos were unpleasant to drive. Then YOU started the more abusive part of the thread by writing a poorly phrased paragraph of tirade aimed at myself and another anti-auto poster, filled with bolded large font outburst. It was only after that that I called you a wankstain.

If you want to report me, go right ahead. I have never been banned from any forum before (well, except from PF where we all got banned several times a week for a while when it was part of the game), and I tend to think that being banned from a single model forum is hardly going to ruin my life, being populated as they are by wierdos and power nazis as they tend to be.

You sir, are dumb. That's not your fault.

[Rolls]

Even if you are right calling people names isn't going to resolve the conflict.

Interesting points though, I personally have only done the bare minimum of study on fluid dynamics so really am out of my depth here.

Edited October 1, 2011 by Rolls

[lilcrash]

Your intake pipe looks pretty simply made so I can't see how it can affect your idle, I've made allot worse ones in the past. Also while on the afm/metal mesh discussion, I'm pretty sure the z32 mesh does pose as a restriction/air bender as mine was flat when installed and is now very sucked in towards the turbo.

[GTSBoy]

Oh, it puts up a restriction, which is why you can free up some flow when you pull it out, but it's not enough restriction to change the shape of the flow. Because a Z32 meter is the same physical size as, say, an RB20 one like mine but is generally flowing a lot more air, the amount of force exerted on the mesh will of course be higher and probably would deform it. I pulled the outlet end of mine out to reduce restriction, but left the inlet end mesh in on the offchance of something bypassing the air filter and trashing the sense elements. AFMs are expensive enough not to deliberately try to wreck them. I've had three AFMs in my car on the same day on the same dyno - one with no mesh, my current one with both meshes and then again after pulling the outlet mesh, and the mixtures were essentially the same. The AFM calibration is not affected by pulling the meshes out at all.

[Rolls]

If you have a big angle just before the AFM element and then spin the AFM around surely that would change the signal it creates though yes?

[DVS JEZ]

It may change only due to a higher velocity on the inside bend/corner. But as Rob mentioned because its in a straight housing i dont think it would matter as much. Where as if it was a modded element fitted to the piping with out the casing than positioning may be important

[Rolls]

Surely if you had a pod immediately on the end of the AFM initially and then put a 90 degree elbow prior to the AFM then this would change things?

Eg the flow would create a big velocity change on the outside of the elbow causing the amount of air actually passing the element to change?

[Guilt-Toy]

back to the topic.

some more questions.

Which spark plugs are you using?

What gap are the spark plugs?

What coil packs do you have in the car now? which coil packs were in the car when it was tuned? was there any issues with spark when tuning ? was the gaps changed when it was tuned to now?

Who has tuned this car? i know Jez looked at it, but did he do a full tune? I don't know if he does full tunes.

The old intake pipe, was it longer then the new one by any chance?

what fuel pump is inside the car now? what pump was inside the car when it was tuned, was the old pump faulty or running badly when it was tuned? who installed the fuel pump and how good of a job did they do?

Man seriously there are sooo many variables on this cluster f**k of a thread that it is hard to keep up to it to understand the issues you are having, to me it sounds like you have 3 different problems that are not related to each other.

Anyways answer ALL the questions for me, lets see where it goes.

cheers