Airflow meter in 'cooler piping

[gts_koop]

Just wondering if anyone has done it on an rb20, or even an rb25?

Seems to be quite popular on the rb30et's with the r31/vl guys, and i can see the appeal as it gives a very small tract form turbo to filter (pod usually), and most claim that it reduces the inlet pressure drop in front of the turbo.

Plus u get a huge flutter on the rb30's, with fmic and no BOV, so would this be the same with a rb20/25 with fmic + blocked off BOV??

Please, no theories, just those that have done it, or seen it done....cheers

[jaik]

Ive had a mate who had a Rb25 with Greddy Plenum, HKS T400 turbo, ARC100mm cooler and had the AFM on the intercooler outlet side of the motor (not pre turbo). Ran fine!

JK

[R31Nismoid]

The main reason people do it is to stop, or try to alieve the stalling problem associated with more boost and no plumback or atmo BOV etc.

Its an easy fix as a lot of west vic workshops really have NFI at times ive noticed.

Remembering a AFM works on unpressurised air.. putting it in the I/C tract will subject it to boost etc etc.

I have seen some AFM's play up after a while.

At the same time some dont. So luck of the draw i guess on that one

[browny]

I can't really see that it would make much difference either way. If everything is running fine as it is I don't see much (if any) return for the effort of moving it.

Don't the VL's also have a more restrictive vane type AFM as opposed to the large hotwire unit on the Skylines?

Packaging is another reason I've heard people give for doing this too.

[V-Spec]

the only reason people would do it is if they want noises

if its done right either way should be fine

[netrati]

Yes I've also seen the AFM on the outlet side of the intercooler. This was on an sr20det and it's been running fine for 4 years.

[gts_koop]

So......has anyone actually done it on an rb20/25...besides ur mate jaik?

[Gav]

Remembering a AFM works on unpressurised air.. putting it in the I/C tract will subject it to boost etc etc.

Actually, one of the benefits of the hot wire MAF sensor that's in the majority of factory cars these days is that it self compensates for differing air charge densities caused by variations in moisture, temperature and altitude. The principle of operation relates directly to the cooling effect of the air passing a heated wire of known thermal and electrical resistance. The cooling effect is a function of both air density and flow rate.

In theory I can see no reason why a MAF sensor shouldn't also compensate for any artificial compression of the charge air (i.e. ram pods, super chargers and turbo chargers) as well.

I would assume that the reason most manufacturors don't place these after the turbo charger is that they are very suceptible oil fouling and there is more likely to be oil in the charge air after the (oil lubricated) turbo.

Edit: I know the thread starter didn't want theories, but just my 2c worth

[paulr33]

why you would want flutter i have no idea...

why dont u just take the intake piping off the car and hit the compressor wheel a few times with a hammer then put the piping back on and drive around its doing the same damage as the flutter

[R31Nismoid]

Actually, one of the benefits of the hot wire MAF sensor that's in the majority of factory cars these days is that it self compensates for differing air charge densities caused by variations in moisture, temperature and altitude. The principle of operation relates directly to the cooling effect of the air passing a heated wire of known thermal and electrical resistance.  The cooling effect is a function of both air density and flow rate.

In theory I can see no reason why a MAF sensor shouldn't also compensate for any artificial compression of the charge air (i.e. ram pods, super chargers and turbo chargers) as well.  

I would assume that the reason most manufacturors don't place these after the turbo charger is that they are very suceptible oil fouling and there is more likely to be oil in the charge air after the (oil lubricated) turbo.

Edit:  I know the thread starter didn't want theories, but just my 2c worth

hopefully SK sees this... very long ago he posted something further into all this which i cant seem to find :|

[Thunderbolt]

why you would want flutter i have no idea...  

why dont u just take the intake piping off the car and hit the compressor wheel a few times with a hammer then put the piping back on and drive around its doing the same damage as the flutter

Actually that's not quite true. I am getting huge flutter now and the mods which could be contributing to it are:

1) Stainless steel intake pipe

2) large k&n filter (but will be replacing soon with smaller Apexi item).

3) Plumback / Atmo BOV.

I have not relocated the AFM, running a z32 in the stock position. However right now, my flutter would do many VLs proud. My bov is functioning as it should too. I guess the air that is being plummed back is hitting the turbo from the intake side, causing the noise.

ps. I do not want as much flutter as I have, mainly because I have kept the car reasonably stock looking, but if it's dosen't sound stock then what's the point.

[gts_koop]

Not really concerned with the flutter too much, but was wondering if the rlocation of the AFM to the cooler pipe giving a short tract from turbo to filter would 'contribute' to a louder/more high pitch flutter, like on the rb30's...... and, in-turn, if it's a worthwhile mod.

All ur replys have been great, but im still waiting 4 first hand experience :Pimp2:

[Sydneykid]

Not really concerned with the flutter too much, but was wondering if the rlocation of the AFM to the cooler pipe giving a short tract from turbo to filter would 'contribute' to a louder/more high pitch flutter, like on the rb30's...... and, in-turn, if it's a worthwhile mod.  

All ur replys have been great, but im still waiting 4 first hand experience  :Pimp2:

I would like to reply, but I don't understand the question. It sounds like you want to stick the POD straight onto the turbo. But why would anyone want to do that when it is going to loose significant horsepower sucking all of that stinking hot air out of the radiator? I must have it wrong, surely?

The reason why the AFM is placed post intercooler is to remove the problem with reversion when running a big turbo/turbos. This causes idle problems, especially if there are big cams in there as well. HKS make a voltage smoother (EIDS) that fixes this problem if you don't want to relocate the AFM.

[ghostflame]

my cars been modified and havent had the computer put in . Im running a t04 turbo right now and with the afm in its origianl position i suffered from stalling etc. so i placed my afm just before my plenum only place i could put it wth my piping setup, this was before reading this thread its been like this for about a month and a half now, ive had no more stalling problems car runs fine but its only a short cut until i get the computer in, its not worth the hassle of doing.. but yes u get loud flutter,i dont get the deep noise but a high pitch pewww peww louder than the vl's but yeah. other than that its not worth the effort. also my turbo hasnt suffered even though yes they do tend to get shaft play i havent had that effect yet, and im running 12 psi atm.

[R31Nismoid]

put a recirc/plumb-back BOV on and you wont have stalling

[mambastu]

I have a 'blow through' AFM on my RB25DETT, works fine

[gts_koop]

ghostflame, have u got an rb20, or 25???

Ur reply is pretty much what i was after, thanks 4 ur 'first hand' answer.....

i can understand people throwing around there 2 cents worth of theories and thoughts, but is good to hear a dirct answer to my q :uh-huh:

[Godzilla32]

I have a 'blow through' AFM on my RB25DETT, works fine

????

[GTR-Ben]

????

If you want to fit Twin turbo's and keep the RB20/25 ECU and wiring etc.. most people use a blow through AFM setup.

Otherwise you would need a single AFM and pipe splitting to two turbos.. wouldn't flow much.

[mambastu]

????

Yeah, RB25DETT does cause confusion sometimes

The Z32 MAF is at inner wing height on the left hand side of the picture above.