New Product To Remove Afm?

[armbrusb]

Hi,

I had an idea and I assume that there is either a problem with it or it is already a product - if it is who makes it.

Many believe that the stalling / backfiring that Skylines put on show is the result of non-plumbback BOVs and that the real cause is the use of AFMs on Skylines. My understanding is that computers using MAP sensors remove this issue - however this can seem expensive to some people. My idea is a MAP sensor that plugs into the plenum (as MAP sensors do) with the wiring plugging in to the the AFM plug. The unit will be calibrate so that the sensed pressure is converted into the same 0-5 volts that the computer gets from the MAF.

Put simply, this unit is a MAP sensor that the car thinks is a AFM - removing the need for a AFM and removing the stalling, backfiring problems associated with non-plumback BOVs.

Any thoughts?

[Beer Baron]

i only have one problem with this idea.

i have had a GTI-R with afm and trust BOV (vented to atmosphere) with smooth idle, no stalling ever. both with a stock ecu, a mines chipped ecu and a stock ecu with daughter board and custom chip

i also have a GTR with twin blitz BOVs, both to atmosphere. I've run it with stock ECU and Power FC and both time it idle smoothly, never stalled. no problems at all.

[armbrusb]

Which bring us back to the

THIS LOW RPM ENGINE STALLING SAGA POSSIBLY SORTED thread.

http://www.skylinesaustralia.com/forums/in...view=getnewpost

I have found that when I plumb by BOV back everything is ok. When I go atmo it seems to turn pear-shaped.

I don't mean to be rude -- I gues this thread would be more for believers that the AFM is the issue (I guess anyone whi has bough a HKS EIDS! : ) )

[Sydneykid]

Hi,

I had an idea and I assume that there is either a problem with it or it is already a product - if it is who makes it.

Many believe that the stalling / backfiring that Skylines put on show is the result of non-plumbback BOVs and that the real cause is the use of AFMs on Skylines. My understanding is that computers using MAP sensors remove this issue - however this can seem expensive to some people. My idea is a MAP sensor that plugs into the plenum (as MAP sensors do) with the wiring plugging in to the the AFM plug. The unit will be calibrate so that the sensed pressure is converted into the same 0-5 volts that the computer gets from the MAF.

Put simply, this unit is a MAP sensor that the car thinks is a AFM - removing the need for a AFM and removing the stalling, backfiring problems associated with non-plumback BOVs.

Any thoughts?

HKS have been making such a device for many years, it’s called a Vane Pressure Converter (VPC). From its name you can tell that it’s been around since vanes were used in AFM‘s, before hot wires became common.

MAP sensors measure changes in pressure which is useful up until the boost controller holds the boost stable. From then on you have no pressure changes for the MAP sensor to see. So they are useless from that point onwards. So you have one dimensional mapping at WOT, ie; only the rpm changes tell the ECU what point on the MAP to use.

This is obviously not the case with an AFM, they report changes in airflow to the ECU for as long as their resolution allows. Consequently at WOT you have 2 references to map against, rpm and engine load. That gives a superior result.

MAP sensors also have a host of problems with the pressure pulses from multiple throttle bodies, hence are very tricky to tune on GTR’s.

Be careful that you are not removing one small problem and creating 2 other large problems in its place.

cheers .

[armbrusb]

I knew that I wouldn't have been the first to think of this! I don't know much about MAP sensore - just what I learnt from threads / articles about stalling and AFMs.

SK - I guess that since the HKS unit is so old it wouldn't be applicable for an RB20?

Also, how much of the AFM's resolution is committed to being on boost - I guess the question would be - when vacuum / boost is zero what is the output voltage of the AFM (I realise that it would be 0 if the car is not on).

[Beer Baron]

Which bring us back to the

THIS LOW RPM ENGINE STALLING SAGA POSSIBLY SORTED thread.

http://www.skylinesaustralia.com/forums/in...view=getnewpost

I have found that when I plumb by BOV back everything is ok. When I go atmo it seems to turn pear-shaped.

I don't mean to be rude -- I gues this thread would be more for believers that the AFM is the issue (I guess anyone whi has bough a HKS EIDS! : ) )

not denying that you have a problem with your car you cant fix, but i can tell you in my own experience i have not had a problem running atmo venting BOV in a couple of nissans. perhaps you need to look a bit more into your cars problems because i know many people running atmo venting bovs on various skylines without any bother at all. perhaps venting the bov to atmosphere on your car is just highlighting another problem (another air leak in your inlet tract perhaps) which isnt noticable when it's plumbed back.

[MerlinTheHapyPig]

Also, how much of the AFM's resolution is committed to being on boost

some aftermarket ecu's use a map sensor instead of the afm, however as sk mentioned once you are on full boost the ecu only has one reference (engine rpm)

the fuel and timing tables in nissan ECU's are a 3dimentional graph showing...

Engine RPM vs Theoretical Pulsewidth (TP is calculated based on AFM voltage, RPM and K value)

so depending on what the engine rpm and TP is, is where on the ecu's maps the data is read from, if you are on full boost - the car will be reading the same manifold pressure and can only use rpm as a reference, as opposed to with an afm where it will still read changes in airflow when on full boost.

It's arguable whether this matters or not,

To answer your question, when tuning doing wot runs on my car, when holding say 10psi of boost the TP is more or less the same for that period, with the exception perhaps of very minor fluctuations.

So anyway, in my opinion, if map sensors are good enough for well known aftermarket ecu's to start using to replace afm's (eg. apexi powerfc djetro, hks fcon...), then i don't see a major problem there. I wouldn't say they were better or worse, an advantage is you get to f**k off the afm, which also can cause problems maxing out the voltage (and have to upgrade to z32 or q45 etc.), at the end of the day, why bother if the afm does the job? the cost of a new afm will be far less then the cost of a map sensor & ecu remap.

Edited March 22, 2006 by MerlinTheHapyPig

[PHaT MR30]

Why not just buy a HKS EIDS controller or whatever they are called (newer version of what SydneyKid said.

[armbrusb]

Alot of people say they don't work / help - this could be because they are used out of context (Zoom's artilcle of the unit says that it is used to stop reversion which they describe as air coming forward out of the turbo and cooling the wire in the AFM (when cars have big turbos)? rather than to stop air leaking out through an atmo BOV) or as Beer Baron is suggesting all of the people suffering this problem have wider issues other than atmo BOVs.

Do the EIDS work - they are quite different in concept to the HKS VPC Sydney Kid was talking about?

[paulr33]

the hks eids appears to be a bandaid solution around the stalling problem and nothing more. you are better of fixing the cause of the problem than applying a workaround

[armbrusb]

I guess its a bit of a funny one. The STALLING SAGA thread seems to have divided people into two schools of thought - those who believe the AFM is the culprit and those who don't. I don't know the answer but I am fascinated that so many people have a common problem and no-one knows the answer!

[Beer Baron]

it is used to stop reversion which they describe as air coming forward out of the turbo and cooling the wire in the AFM (when cars have big turbos)? rather than to stop air leaking out through an atmo BOV)

yep, spot on. the EIDS pro and the VPC are 2 different things. i really think if there is a problem with running an atmo BOV on an AFM equipped nissan then something either in it's installation, or adjustment or another problem alltogether is causing the stalling problem. as i've owned and been in a number of otherwise standard skylines, silvias etc with atmo bovs and stock ecus and they ran just nicely. steady idle, no stalling.

[Topaz]

A little off stopic but I didnt want to create another thread for this....

If you have a D-Jetro and still have the standard AFM's, does unplugging the volts supply from them make them permanently open or closed? or is that the wrong 'action' of an unvolted AFM?

[bluefire]

Wow I knew there had to be other people with this idea in mind. I also want to add another reason for this maf-map convertor besides the low rpm stall. s14 SR, RB20 and RB25's do not have a d-jetro version of the powerfc. This means if you go with a top mount turbo with 4" inlet, you have to have a super tacky looking 4"-3" adapter to hook up the maf in front of the turbo. This absolutely kills the look of nice top mounted turbo.

Another Idea I had was to make a maf sensor and flange that can be installed in the ic piping. Essentially making it a blow-thru maf setup rather than a draw-thru. If nissan freakin made the maf sensor removable from the housing like other manufacturers this would be a very realistic idea.

-Bluefire

[CefiroBoy]

Essentially making it a blow-thru maf setup rather than a draw-thru. If nissan freakin made the maf sensor removable from the housing like other manufacturers this would be a very realistic idea.

-Bluefire

Has any one plumbed the AFM as a blow through setup?

Wouldn't be too hard to plumb in just b4 the throtle... Just a thought

[RACESPEC]

Has any one plumbed the AFM as a blow through setup?

Wouldn't be too hard to plumb in just b4 the throtle... Just a thought

A lot of the RB30ET VL guys are doing this, and does not seem to change things

RACESPEC SALES TEAM

[armbrusb]

Hi,

As I understand it the AFM tells the ECU how much air is coming into the car using a wire which is warmer (I guess) as less air comes in and cooler as more air comes in. Before the turbo the air would be at a largely ambient temperature, whilst after the turbo the air would be significantly warmer - would this make a difference to the reading of the AFM?

Thanks.

[Beer Baron]

A little off stopic but I didnt want to create another thread for this....

If you have a D-Jetro and still have the standard AFM's, does unplugging the volts supply from them make them permanently open or closed? or is that the wrong 'action' of an unvolted AFM?

an air flow metre on a GTR is nothing like what you are describing. it's a pipe basically with a hotwire sensor inside. it doesnt open or close, or twist or turn or anything really. it just sits there. air flowing over the sensor cools the sensor which causes a change in the AFMs output voltage.

can i ask why do you want a djetro if you are leaving the AFMs there? just buy a normal PFC.