Big turbo afm. Rb26. Reverberation.

[MJTru]

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.

 

 

 

[baron_von_bootsector]

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.

[MJTru]

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.

[R_34]

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.

[baron_von_bootsector]

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. 

[GTSBoy]

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.

[Dose Pipe Sutututu]

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.

[MJTru]

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.

[Dose Pipe Sutututu]

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.

[GTSBoy]

The R35 type sensors are, by design, more one-directional than the old type ones.  They have a built in shield for reversion.

[TXSquirrel]

No harm to try R35 blade type sensors, used genuine ones are cheap on eBay, about $15 USD.  Just avoid the new but knockoff ones.