Jump to content
SAU Community

Recommended Posts

Hello guys. I just have what I believe is a simple question. I have seen guys place a afm in a 4 inch pipe and mess up the whole tune on a pfc. I've seen a few threads around here about the topic.

If I was to place it in the exact sized pipe as the plastic pipe it made in. It should provide the same results right??. I'm just trying somthing on one of my old cars.

In reality if you must know I'm chasing some way eliminating reverberation on a big turbo set up. Over the years I have learnt vent back in at the right angle and some sharp bends work well and place the afm as far away as possible.

I have also learnt the journal bearing turbos are more forgiven for this attributes.

I have made a home made pipe to help this out, remember just an experimental try here. I have made the pipe off the turbo 4"inch hits a 90 and a sharp 45 down at another 90 then split into 2 3inch pipes into 2 filters that fits perfect under the lights and behind the front right side of the crash bar. I ran out of room for the afms but I have cut them just exposing the sensor parts only.

I'm thing of just placing them both in each 3 inch pipe making them act just like the greedy Y/ split pipe just way further down.

Please look at the afm. And I would appreciate and feed back as to how it will work. Or any opinions that would help in this situation. I'm placing this in the same 3 inch pipe. Just aluminum.

 

 

 

20170801_173425.jpg

Link to comment
https://www.sau.com.au/forums/topic/471480-big-turbo-afm-rb26-reverberation/
Share on other sites

They might function in the same manner as long as you have the exact same pipe diameter and placement in terms of airflow over the sensor.

If you are having issues with reverb / air disturbance back to the sensor I might suggest that a flow corrector (something like a laminar flow insert) after the AFM's would help combat the issue. These are often used in lab / industrial equipment and look like either a grid of plastic or a bundle of straws in the pipe that that straightens out the flow and makes disturbances harder to achieve but comes at the cost of a small amount of flow restriction.

The other (recommended) option would be ditching the AFM's and going for a MAP based modern ECU - its a more expensive but opens the door to doing a lot more with the car in the future and removes all of the intake mess from the AFM's. The PFC was a great solution for milder mods back in the heyday of these cars but quickly falls flat trying to cope when you are pushing more serious mods. A huge variety of these can be had surprisingly cheap particularly second hand if you are willing to hunt through eBay / SAU. There are hundreds of threads on here talking about the different ECU options available and the pro/cons of them.

  • Like 2

That's is such a simple idea. How the hell didn't I think of that. I'm all for the ecu. I just testing a old setup I've never got around to finish up. Thanks for your suggestion. This is why I read and ask questions. I will try both methods.

I installed an "air straightener" before the AFM last week. The engine reacts much better/quicker when I blip the throttle but it didn't solved the reverb problem. Reducing the intake pipe from 80mm to 63m with a reducer right at the exit of the AFM solved the problem. No more stalling if I let off the engine from 4000+rpm to idle.

Still the crispness of the engine gained with the piece of honeycomb makes it worthwhile.

Relocating the straightener to after the AFM's (as far as practical) as this should make it harder for disturbances downstream to reach back to the sensor - from the sound of it the increased velocity of the air at the reducer has solved the problem for you though. 

A flow straightener between the turbo and AFM won't stop air from actually flowing backwards, it will just make sure it flows backwards straight.  Which is not likely to help.

The rule is this.....if you change pretty much anything about how the AFMs are installed, then they will "change" their calibration.  By that I mean that the signal they give for a certain mass flow of air will change a bit because the velocity profile through the tube will differ.  If the profile differs, then you might have more or less total air flow through the tube for the same measured velocity at the centreline location of the sensor bead.  The factory ECU was tuned to work with the response of those AFMs as installed in the same plastic pipework, hooked up to the same airbox inlet, etc etc, blah blah.  Putting a pod filter on will change that.  Changing the pipe between the AFM and the turbo will change that.  The changes might be slight or they could be large enough to require cleaning the tune up.

So, drastically changing the pipework (like Marcus has done) would likely cause changes requiring retuning.  Fine.  That's within expectation.  Relocating the sensor from its original plastic body to an identical ID alloy pipe, in theory, wouldn't change the velocity response, but every other aspect of the idea will cause changes that will alter its overall response, likely requiring retuning.  The main thing that strikes me here though, is the photo where the sensor is still attached to a piece of the original outer plastic housing.  If the intention is to lay that plastic bit over the outside of the alloy pipe, then the sensor bead won't be in the original centreline position, so I would expect the "new" meter to work a little differently to the original anyway.

tldr; Expect to need to retune.

And if you're going through all that trouble just get a R35 AFM, with an "air straightener tube" and installed it pressure side... you can dose/BOV/SSQV(US' favourite BOV) all day.

I still recommend pissing off the PowerFC.

  • Like 1

I understand once you change the sensor into a different pipe it would be off if it's not centered and so forth. But it's way better then just dropping it in a 4inch pipe where the different is much greater. If dimensionally it sits in the same pipe just aluminium, I can see it being off that much. Much like any air mod I expect to retune it.

Get a R35 AFM. Your car will drive so much nicer.

I've tuned two cars on R35 AFMs vs similar cars on Z32 and tell you the ones with R35 are a little more resilient to a bit of reversion from solid intakes and a bit of dose... I love dose.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Guys since i bought r33 gts25t coupe 1994 automatic a/t(manual swap 350z gearbox)  all i got is problems, always problems. Lets start with that when i turn key into ignition(ON) fuel pump doesnt always works. Sometimes i have to turn key twice Off/on/off/on until it primes. Its new, dw300 - 340lph. My gearbox broke so i did gearbox swap, install different intake manifold, injectors and i take pipes. Car was sitting in garage for more than half a year. I did assembly all not that long ago and when i turn ignition cant hear prime. All of sudden it stopped working. Theres many videos on YouTube how to make relay mod on r33 straight from battery so i did and it doesnt work! 😰 30 - battery positive  87 - positive from fuel pump to relay 85, 86 - one of two wires from original fuel pump wires(light blue, grey) and it didn’t work. so I check on ignition and took original BLUE relays wires from trunk, next to fuses. (I believe it’s IGN+ and ECU pin 18. it didn’t work…  tried connecting (IGN+ from og relay) and (ECU 104 from 1of4 FPCM wires) to my new relay 85/86 and it didn’t work.  I unplug FPCM. Didn’t work. im thinking what’s wrong   fuel pump is working, if I leave IGN+ on 85 and 86 straight to ground it works but it’s just nonstop. Since it getting constant 12v after key in ON. light blue wire gives me 6-8v.  so how this should be connected? What causing ECU not giving — on pin? Or I did sth wrong and that’s why it doesn’t work? I need negative signal on ECU that control fuel pump. What this should be?
    • You can use your VIN to look up the factory part number somewhere like amayama, and then look to order new if necessary. https://www.amayama.com/en/genuine-catalogs/nissan Depending on price you might want to rebuild instead. @GTSBoy I had an interesting insight into US market parts when the Titan rear calipers were sticking. New calipers were dirt cheap, about 20% more than a rebuild kit....they are just considered throw away maintenance items
    • Funny, but really not funny. Thank god (most) f the world has moved on since then
    • Lots of votes for driving onto a plank first; that is the quickest way I've found, 25mm is enough for my case but that will vary by car It also depends where you are going for. On the 32 I can get to the rear diff with my floor jack if I do that end first, and get it up on stands. Then I lift the front from either front tow hook as high as needed, also onto stands. Sometimes I need a small lift on the other tow hook to get it level enough If I do the front first I can't get to the rear diff because of the angle of the car Other options are getting to the front mount of the rear subframe from in front of the wheel (if only lifting one side, or just do both which is a bit of a pain compared to one lift from the diff), or also the gearbox cross member mount on the driver's side if you are  just trying to lift the driver's side. I This is the jack I use; it says 75mm clearance but of course that is only on the lower section so if you have to reach too far in like the diff you still get stuck. https://www.snapon-bluepoint.com.sg/category/Floor-Jacks/product/Floor-Jack,-2-Ton-Low-Profile
    • On the bright side, the weather will turn much nicer for working outside shortly....sounds like you might need to start on a neighbour's garden next
×
×
  • Create New...