Mounting Twin Afm In Ic Pipe...

[GeeTR]

Hi All,

Iv heard that mounting the AFM in the pipe as per >> "Light's" http://maataa0b.jeeran.com/DSC04126.JPG

can be done, and works, there are just considerations like increased blow by on the hot wire etc, I got thinking though…

I’d read Paul’s PFC site mentioning you can feed the signal from one O2 sensor into both inputs on the ECU.

- So I was thinking, could I either fit two AFM’s in the IC piping, or run one, and feed the signal to BOTH inputs on the ECU?

- Assuming that would work, im left with either trying to fit two AFMs in the piping, or running one 60mm (thinks) Nismo AFM.

- There was an thread on here about cutting the hotwire out of a AFM and placing it in a larger pipe. I would think for the same amount of air, the unit would give a lower reading as its now moving a lot slower.

Q: What do ppl think about mounting the guts of a Z32 (or a Nismo replacement, like me) into the 80mm pipe before the plenum, feed it to both AFM inputs on a PFC, then jimmy the AFM corrections with Datalogit.

Any thoughts? 

- M

[paulr33]

yeah just run a single z32 and run its signal wire to both afm inputs on the powerfc/car loom. ie afm1 goes to afm1 and afm2

the powerfc just does an average across both afms to work out load anyway.

you wont need datalogit for it at all, just wire it up and away u go, select z32 and your done. i wouldnt bother with custom hack up afm style pipe changing stuff, just go straight to z32

[GeeTR]

Thanks Paul... but that'd mean selling my in box Nismo's - bugger

[paulr33]

well you can try and use one nismo then

just hope its enough resolution for you

[GeeTR]

Nismo rate the pair at 775ps, which is about 30kw+ over, the top-end rating of the single im planning to run.. which i might leave explored till rebuild.

[T04GTR]

they wont like the oily air.

[GeeTR]

they wont like the oily air.

Hey T04GTR,

Sorry, forgot to mention im not running stock airbox or stock blow-by recirc to the rear turbo. My car came off the boat with HKS shroom pods and im running a catch can with stock PCV, but yah, I figured that would be one of the legitimate issues for people in the other boat.

I found some threads last night on RX7forums, Calaisturbo.com and NS.com.nz (note .NZ) all successful, all fixing varying rough running issues. The main points ppl seem to bring up, is intake temp and mass.

Some people saying the AFM weren’t designed to take the varying temperature out of the turbo and through the IC. I would have thought that the stock the air box would see a fairly wide range of temps, winter conditions, and idling in summer.

Mass - would the AFM measure the now pressurized air running through it? Im not sure. My thinking gets me as far as, momentum and latent heat holding capacity. The compressed air, is denser and so should still remove the correct corresponding amount of heat from the hot wire.. me thinks

Please all, flame away, I need thoughts from all angles

- M

[Adriano]

Stocky Mc stock has this fittes to his car, maybe pm him and see if he has had any probs. Remember you will need an afm that will have a lot of high end resolution, as you now have one instead of two afm's, i would go for a Q45. This will allow atmospheric bov's to not affect running as long as the afm is after it in the piping. running boost through it shouldn't make any difference in theory, as the AFM measures the MASS of the air, regardless of temp or pressure, just as loks as there aren't any mechanical issues with doing it such as i melting. I would place it as close to the throttle, after any bov on a straight run of pipe, with at least one bend between it and the throttle. Also make sure you leave the mesh in the AFM, as i would imagine the biggest problem could be associated with turbulence in the pipework causing erratic readings.

[GTR-Ben]

Seems to work fine having it after the intercooler. Oil, heat whatever.. not hurting it.

I made a post about this a while ago.. no one was much help.

I used a single R32 AFM in a 4" pipe which is basically double the area of a 3" pipe. It seemed to work well and the data to the PFC seemed as if there was 2 x 3" R32 AFMS. I decided to go with the normal setup in the end because I didn't know if it was going to be 100%, however since then I have had friends do similar and it works fine.

As for using a single Z32 and sending both signals to the PFC.. I can't see this working. The air will be moving twice as fast throught a single 3" pipe so the reading will be way off. Thats the reason I used a 4" pipe.. to make it even.

However.. I have seen a GTR making over 800HP. I looked harder at this car and found an AFM probe Stuck in the side of the 3" intercooler pipe after the intercooler. This car had a chipped stock AFM.

[GeeTR]

Cheers Adriano, will look around

Good idea GTR-Ben, with the 4" pipe and i know what you mean about the 100% I trying to ascertain a success rate before i mess with it.

As for the signal from both AFM's showing air flow for the entire motor, i was going to tweak the tables with Datalogit, to half each signal.

800HP niiice though what do you mean by a "chipped AFM" ? You mean they used a different PCB inside the AFM body? Would be cool to know how well that car ran. Results under WOT i think should be ok, the test is likely to be cruising, partial throttle, rapid throttle movement, overrun etc.

appreciated

-M

[GTR-Ben]

Sorry I meant "chipped ECU"

Hmm so putting in a single stock AFM and halfing the data on the Power FC, does that work? Seems that would be a good way to do it..

[paulr33]

you shouldnt need to half the airflow data tables

the pfc simply takes both afm signals

averages them out (discuiossn on datalogit forum seem to suggest this) and then does;

LOAD = CORRECTION * (16384 * Airflow lookup(MAFSV) / RPM)

uses to work out load placement on the load axis

[Adriano]

I would have thought you would have to reduce it , as the afm would be flowing twice the air

[paulr33]

i believe it does an average of both afm voltages and then uses this in the load axis calculation

[stolen_s15]

Just wondering why you would do this in the first place? Is is to stop air air 'bouncing' between turbo and AFM telling the ECU to fuel when the throttle is closed?

[GeeTR]

Just wondering why you would do this in the first place? Is is to stop air air 'bouncing' between turbo and AFM telling the ECU to fuel when the throttle is closed?

Hey there,

First started thinking of it, as a way to save me a few $100 in mounting twin AFM's. Its either one of those Trust "suction pipes" that’s the typical shiny cast "Y" to mount the AFMs on a single turbo, or having someone fabricate one, which at labor rates, would be a small fortune.

Moving the AFM would mean just one large pipe off turbo > air box > done, no more headaches.

Tis also a way for the "Dose - Dose" lads to get their kicks without flaming on gearshifts.

"Air bouncing" - i wasn't directly worried about this, as others have run the same setup, same gear without issues... as far as im aware- but yes, it would obviously stop that too.

PaulR33 - something will need to be done with the AFM tables no? as the ONE AFM, will have the entire engines air requirement flowing through it, then fed into both AFM inputs on the ECU; would show way too much combined voltage no? Average away, its still going to show double.

Cheers All

- M

[paulr33]

normally it looks like this;

AFM1: 3.21v

AFM2: 3.11v

what you do is get AFM1 and run that to your airflow meter, then run that signal wire to AFM2 input on the ECU as well so you get;

AFM1: 3.10v

AFM2: 3.10v

so they will both read exactly the same. if you check the SAFC2 they also support duplexing and halving of airflow meters, that is run twins on a single afm ECU or a single on twin AFM ecu, you get a choice of average, add, or single outut signals, ie

twin z32s to a single AFM input, ie: twin z32 on a GTST PowerFC

single q45 to twin AFM input, ie: twin q45 on a GTR PowerFC

can either bridge the wires, or use the SAFC to manipulate the AFM signals if you are worried and want to be sure its 100% ok, but the wire method is essentially the same thing, it will average them both as AFM1 and AFM2

at least this is how ive understood and gary has explained it

[GeeTR]

Paulr33 - Thanks a lot man, but damm I'm confused now =) Need to grab a coffee

1) Stock Setup (will use your voltages)

This is my understanding from what your saying

AFM1: 3.21

AFM2: 3.11

= Average would be 3.16v ? <- This would be used in your PFC LOAD calc.

2) Single Z32 bridged

lets pretend Z32 same as Stocker AFM airflow vs voltage voltage.

AFM1: 6.42

AFM2: 6.22

= Average would be 6.32v

- I don't understand where your 3.10 comes from, it inst the average of 3.21 and 3.11

- Even if you average the Z32 output, its STILL double the normal air flow

I'm sure Iv missed something basic, thanks for your patience.

- M

[paulr33]

thats ok, the SAFC lets you choose average, add or single value for ouput when using a twin AFM Setup on a single AFM Car

that is if you had two small crappy afms then you may want to add the votages together, not sure where u would use this type of setup, but it supports it, it also supports average (ie: rb26 style)

twin afms on a single AFM car

IN: 2

OUT: 1

MODE: ADD

so in the ADD method on the SAFC

afm1 3.10v

afm2 3.11v

goes to

AFMX 6.22v

or in the AVG mode

afm1 3.10v

afm2 3.11v

AFMX 3.105v

and AFMX runs to the ECU input for airflow meter 1 (as its a single AFM car only)

by default on an RB26 if you were to use the SAFC to allow maniupluation of AFMS you would have

IN: 1

OUT: 2

MOde: AVG

AFM1: 3.10v

AFM1X output will be 3.105v and you run this to AFM1 input on the ecu

AFM2X output will be 3.105v and you run this to AFM2 input on the ECU

now

that is the same as running the same signal wire from a physical AFM1 only unit to AFM1 and AFM2 input on the ECU

[Adriano]

Correct me if im wrong, but if a gtr at 3000rpm has 2 afm's at say 2.5v each, then putting one in the ic pipe will run about 3.5v, as it has all the air running through one 80mm hole instead of two. If you then bridge the wiring, it will think that both afm's are running 3.5v, hence doubling the fueling. If you ran a bigger afm(q45) at 3000 rpm it should only see about 3v, and then bridge it. Then trim the values, or adjust the injector % until it is about right and then tune from there.