Mounted AFM AFTER turbo. Here's what I noticed
#1
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Mounted AFM AFTER turbo. Here's what I noticed
Well, I mounted my AFM right at the TB....
Before, I always had a little low end roughness when touching the throttle.. just a little misfiring, etc, but nothing bad.
Anyways, I figured it was probably from having the turbo and IC and all that im between the throttle plates and the AFM. I figured that it was going lean for a split second because the vacuum from the throttle plates opening took too long to reach the AFM.... Well, I was right!
MAN does it run smoothly now. No misfiring, perfectly smooth, instant throttle response! I LOVE it!
It also should theoretically give you a *little* bit more power, since the AFM represents less of a restriction after the turbo, but you HAVE to have an S-AFC or something, because it willl read leaner under boost. It also allows you to get rid of the TID all together, and open that airflow up a bit. I did it more of a drivability/smoothness mod, rather than pure power.
Anyways, bottom line- great mod, greatly impoved my response and drivability...I'd really recommend it if you have a big FMIC and such, just NEED to be able to compensate for the leaner reading and tune it under boost. There are a lot of big power 7's in Japan that have done this..... it's NOT a huge power gain (though I'm sure it is measurable) but it gets rid of clutter and really makes things smoother!
Before, I always had a little low end roughness when touching the throttle.. just a little misfiring, etc, but nothing bad.
Anyways, I figured it was probably from having the turbo and IC and all that im between the throttle plates and the AFM. I figured that it was going lean for a split second because the vacuum from the throttle plates opening took too long to reach the AFM.... Well, I was right!
MAN does it run smoothly now. No misfiring, perfectly smooth, instant throttle response! I LOVE it!
It also should theoretically give you a *little* bit more power, since the AFM represents less of a restriction after the turbo, but you HAVE to have an S-AFC or something, because it willl read leaner under boost. It also allows you to get rid of the TID all together, and open that airflow up a bit. I did it more of a drivability/smoothness mod, rather than pure power.
Anyways, bottom line- great mod, greatly impoved my response and drivability...I'd really recommend it if you have a big FMIC and such, just NEED to be able to compensate for the leaner reading and tune it under boost. There are a lot of big power 7's in Japan that have done this..... it's NOT a huge power gain (though I'm sure it is measurable) but it gets rid of clutter and really makes things smoother!
Last edited by Bambam7; 05-08-03 at 03:44 PM.
#3
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That's great. With an Safc you could tune out the air/fuel change that it would make and have less dead space between it and the plates.
Now if only there was a way to put the FMIC before the turbo . . .
Now if only there was a way to put the FMIC before the turbo . . .
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Did you relocate your air intake temp. sensor? If you didnt that may be what is causing the car to run lean. The air going into the engine after the turbo is much hotter than the air coming from before the turbo.
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All you guys with flapper door AFM ('87 & 88 TII),
you cannot do this . The AFM *has* to go before the turbo. Why I know? I've done it when I installed my IC and had to re- do the piping. For one, the flapper door type AFM has to be level either ribbed side down or up but not angled in any way. Gravity will have an effect on the door. Another is the black cap will blow off or your boost will leak if you make a hole in it. You all see the Japan guys do this but they're all '89'91 AFMs. I'm not sure how much pressure it can handle though. The '87,88 sure cannot handle more than 7 or so psi.
you cannot do this . The AFM *has* to go before the turbo. Why I know? I've done it when I installed my IC and had to re- do the piping. For one, the flapper door type AFM has to be level either ribbed side down or up but not angled in any way. Gravity will have an effect on the door. Another is the black cap will blow off or your boost will leak if you make a hole in it. You all see the Japan guys do this but they're all '89'91 AFMs. I'm not sure how much pressure it can handle though. The '87,88 sure cannot handle more than 7 or so psi.
#7
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Originally posted by 600HP CLUB
seems interesting but since i have microtech i don't really care, but i know how it feels like without a TID/AFM though, boost sounds alot louder and hits earlier.
seems interesting but since i have microtech i don't really care, but i know how it feels like without a TID/AFM though, boost sounds alot louder and hits earlier.
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#9
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Re: Mounted AFM AFTER turbo. Here's what I noticed
Originally posted by Bambam7
It also should theoretically give you a *little* bit more power, since the AFM represents less of a restriction after the turbo...
It also should theoretically give you a *little* bit more power, since the AFM represents less of a restriction after the turbo...
I'm glad to here this mod was successful though. I can see how moving the AFM closer to the engine would allow the ECU to respond quicker to what's actually happening in the engine.
Have you made any adjustments via the S-AFC? How much was required? Where are the pics?
#10
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Originally posted by MrBob 86
Did you relocate your air intake temp. sensor?
Did you relocate your air intake temp. sensor?
#12
Rotors still spinning
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I hate arguing about this mod because it is a fact it does work! Air moving out of the turbo is moving slower than air moving into the turbo. It has to. In order to compress air, you have to slow it down. Although the air is moving slower through the afm now than it was before the turbo there is still the exact same amount of air flowing through it. The restiction does not look as big to the incoming air as it did before. The molecules are more compressed. If you shrink yourself and walk through a door, the door is suddenly bigger and there is more room. What's not to understand? I've endorsed this for years and I'm glad to see someone that did it and realizes that it is great. Ultimate power won't be affected since your turbo still flows the same amount of air but throttle response is much better and spoolup times are improved. How the hell is a dyno going to prove that? FWIW you can use the flapper door afm with no problems provided that you keep it level. I've seen this done many times.
#13
Rotary Freak
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Originally posted by IWNTA20B
All you guys with flapper door AFM ('87 & 88 TII),
you cannot do this . The AFM *has* to go before the turbo. Why I know? I've done it when I installed my IC and had to re- do the piping. For one, the flapper door type AFM has to be level either ribbed side down or up but not angled in any way. Gravity will have an effect on the door. Another is the black cap will blow off or your boost will leak if you make a hole in it. You all see the Japan guys do this but they're all '89'91 AFMs. I'm not sure how much pressure it can handle though. The '87,88 sure cannot handle more than 7 or so psi.
All you guys with flapper door AFM ('87 & 88 TII),
you cannot do this . The AFM *has* to go before the turbo. Why I know? I've done it when I installed my IC and had to re- do the piping. For one, the flapper door type AFM has to be level either ribbed side down or up but not angled in any way. Gravity will have an effect on the door. Another is the black cap will blow off or your boost will leak if you make a hole in it. You all see the Japan guys do this but they're all '89'91 AFMs. I'm not sure how much pressure it can handle though. The '87,88 sure cannot handle more than 7 or so psi.
#14
Rotors still spinning
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You can use the flapper door style as long as it is mounted flat. What IWNTA20B is referring to as a problem is with the plastic cover that goes over the electronics in the afm. It is merely siliconed in. You will be OK as long as you can keep this attached and still sealed. If you want to change to the other afm you will have to swap a couple of wires. Someone did a writeup on the conversion but I don't know where it is.
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Well in some ways bam is right. If you look at the basic equation for noble gases (all found in our air) which is PV=NRT. Pressure and volume are directly proportional. Therefore if you incress the pressure, you also incress the volume. So even though the restriction by the afm is the same, you will be moving "more" air through it in a pressurized form therefore reducing the restriction to every individual molecule of air. So puting the afm after the turbo will reduce the restriction to the air moving through it when you look at it from a molecular level.
#16
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Originally posted by rotarygod
I hate arguing about this mod because it is a fact it does work!
I hate arguing about this mod because it is a fact it does work!
Although the air is moving slower through the afm now than it was before the turbo there is still the exact same amount of air flowing through it. The restiction does not look as big to the incoming air as it did before.
Ultimate power won't be affected since your turbo still flows the same amount of air...
#17
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Originally posted by capsoval
If you look at the basic equation for noble gases (all found in our air) which is PV=NRT. Pressure and volume are directly proportional. Therefore if you incress the pressure, you also incress the volume.
If you look at the basic equation for noble gases (all found in our air) which is PV=NRT. Pressure and volume are directly proportional. Therefore if you incress the pressure, you also incress the volume.
#18
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Hmmm, sounds tempting. Very tempting. I love whipcrack response time from engines.
I've seen this mod go back many years in the Japanese magazines. My question is how does the AFM handle the extra heat? Normally all it sees through it close to ambient air temps. But even with a decent FMIC, the air in it will be a good deal warmer than it used to deal with. Or does that not matter much because the stock location sees a decent amount of underhood temps from being located near the turbo but on the other side of the engine bay it'll be relatively cooler.
So, will the heat mess it up?
I'm not sure why I'm so concerned. I guess I like to see innovative and experimental minds at work. Soon I'll be going to a rather large hotwire MAF (closely related to a 300ZX but from a certain little RB engine ). All I need to do is get the MAF from a buddy overseas that has an excess of them laying around and use the GReddy e-Manage to do the translating. There are those that say it's impossible. But they haven't seen it done yet. They will, oh yes, they will. Muhahahaha.
I've seen this mod go back many years in the Japanese magazines. My question is how does the AFM handle the extra heat? Normally all it sees through it close to ambient air temps. But even with a decent FMIC, the air in it will be a good deal warmer than it used to deal with. Or does that not matter much because the stock location sees a decent amount of underhood temps from being located near the turbo but on the other side of the engine bay it'll be relatively cooler.
So, will the heat mess it up?
I'm not sure why I'm so concerned. I guess I like to see innovative and experimental minds at work. Soon I'll be going to a rather large hotwire MAF (closely related to a 300ZX but from a certain little RB engine ). All I need to do is get the MAF from a buddy overseas that has an excess of them laying around and use the GReddy e-Manage to do the translating. There are those that say it's impossible. But they haven't seen it done yet. They will, oh yes, they will. Muhahahaha.
#19
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It should handle the extra heat just fine within limits (it looks like it will top out around 65deg C though). The temp sensor in the AFM is used to compute the density of the air, "multiply" by the AFM vane reading and you get mass flow. So the ECU will just think its a really hot day out and the air is thinner (remember the PV=nRT). The temp sensor in the intake elbow is used for timing retard.
Henrik
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Henrik
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#21
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There's no need to. There's an air temp sensor built into the AFM (so that one's OK) and the ECU's main air temp sensor is still located downstream of the new AFM location (intake plenum on NA's, TB entry on Turbos).
#22
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If anyone knows where the thread that talked about converting to an S5 AFM is, or where I can find a write up, I'd love to switch, I was always under the impression it just couldn't be done.
As far as whether low pressure, high volume air (before turbo) gets measured differently then high pressure, low volume air (after turbo) in theory they should be the same. What the flapper door is measuring is how many times it gets hit by a molecule of air each second (or millisecond) (O2 or N2 or whatever), and how hard the molecules hit. The more molecules, and the faster they're going, the further it swings back. Whether all those molecules are squeezed together, moving (relatively) slowly , or spaced out, but moving fast shouldn't matter.
Of course the real world screws up all this theory, but I have no idea how, or what effect it has, seems like it would be small though. I just think measuring the air closer to where it matters makes sense.
As far as whether low pressure, high volume air (before turbo) gets measured differently then high pressure, low volume air (after turbo) in theory they should be the same. What the flapper door is measuring is how many times it gets hit by a molecule of air each second (or millisecond) (O2 or N2 or whatever), and how hard the molecules hit. The more molecules, and the faster they're going, the further it swings back. Whether all those molecules are squeezed together, moving (relatively) slowly , or spaced out, but moving fast shouldn't matter.
Of course the real world screws up all this theory, but I have no idea how, or what effect it has, seems like it would be small though. I just think measuring the air closer to where it matters makes sense.
#23
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Originally posted by MrBob 86
The air temp sensor in the AFM is the one I was talking about. If the ECU gets a air temp reading thats hotter then the air before the turbo actually is, then the amount of air being read by the ECU is going to be less then it actually is. If the ECU thinks less air is going through the engine, then its going to give the engine less fuel, resulting in a lean condition. Remember, the ecu is programmed to assume that the air temp sensor is going to be reading a temp at or close to outside temp.
The air temp sensor in the AFM is the one I was talking about. If the ECU gets a air temp reading thats hotter then the air before the turbo actually is, then the amount of air being read by the ECU is going to be less then it actually is. If the ECU thinks less air is going through the engine, then its going to give the engine less fuel, resulting in a lean condition. Remember, the ecu is programmed to assume that the air temp sensor is going to be reading a temp at or close to outside temp.
Henrik
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#24
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Originally posted by TristanTII
If anyone knows where the thread that talked about converting to an S5 AFM is, or where I can find a write up, I'd love to switch, I was always under the impression it just couldn't be done.
If anyone knows where the thread that talked about converting to an S5 AFM is, or where I can find a write up, I'd love to switch, I was always under the impression it just couldn't be done.
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Originally posted by Jerk_Racer
I was thinking more along the lines of the durability of the unit.
I was thinking more along the lines of the durability of the unit.
Henrik
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