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Discussion Starter · #1 · (Edited)
Hi!

Since the installation of an A/A intercooler to my supercharged setups (both the MP62 and the TVS R1320), I had some issues with respect to idle and throttle opening rate vs. A/F ratios. To be honest, I had throttle opening rate vs. A/F ratios issues when I also had no intercooler at my setup to the point that I had completely disabled the INJ acceleration map at the eManage Ultimate. However, with my current setup, this problem is more severe. At first I thought that these problems were related to the fact that I had piggyback ECUs but behavior is still the same now that I have an Apexi PFC.

My current setup is as follows:

Air intake -> MAF -> Throttle body -> Supercharger -> Intercooler -> Intake manifold.

I think that this setup is problematic and should be as follows:

Air intake -> Throttle body -> Supercharger -> Intercooler -> MAF -> Intake manifold.

I think that this is the case for 2 reasons. First, the ECU is provided with the correct air temperature and second, it reads the actual amount of air that enters the engine. I believe that under boost, the MAF sensor reads the same at both setups but under vacuum, this does not stand. The reason for that is the existence of the bypass valve which, according to Magnuson, "when vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system".

From what I understand, when the bypass valve is open, part of the air mass does not actually find its way to the intake manifold and this is why I am having rich conditions and abnormal MAF voltages when opening the throttle lightly.

The problem with that is that my intercooler pipings have 2.25" ID which means that if I place the MAF in there, it is going to max out real soon. Do you think than an STI MAF could handle the airflow through such a small pipe? Any opinions or solutions would be gladly appreciated...
 

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Discussion Starter · #4 ·
Thanks Ronin. I 've done something similar for temperature; I installed a 2nd-hand MAF at discharge and get my temps from there. By the way, where is your MAF at your setup? Do you have the bypass valve of the MP62 installed or have you removed it?
 

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I think that this setup is problematic and should be as follows:

Air intake -> Throttle body -> Supercharger -> Intercooler -> MAF -> Intake manifold.

Air intake -> Supercharger -> Intercooler -> MAF -> Throttle body -> Intake manifold.

This setup, and a 3" pipe and you will be fine. You will have to retune obviously, but thats how virtually 100% of all the turbo cars are set up.
 

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Discussion Starter · #9 ·
Wouldn't a 3" pipe after the intercooler be an overkill for my setup? Could I be having any sort of "lugginess" because of the slower air velocity when compared to my current 2.25" pipe? I am currently blowing about 670cfm from supercharger to intercooler when at redline...
 

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don't mean to threadjack, but this thread will help me out with my setup as well....

You need the bypass, my MAF is 3" in front of the throttle body in a 3" straight pipe..
hey frank do you have the fins like the oem setup right before the MAF?


This setup, and a 3" pipe and you will be fine. You will have to retune obviously, but thats how virtually 100% of all the turbo cars are set up.
if you look at the blitz supercharger setup, it has the MAF in the intake right behind the air filter, so which setup would be better?
 

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A guy from ccuk installed an M45 (roots) on his 1zz and tried the above mentioned positions. Out of his experience he concluded that the best option is:
Air intake -> MAF -> Throttle body -> Supercharger -> Intercooler -> Intake manifold.
 

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Discussion Starter · #13 ·
So what are the benefits of this positioning against placing the MAF before the intake manifold? I am having MAF spiking problems at sudden throttle changes, hence this discussion...
 

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I wonder why this doesn't happen on a turbo setup when the blow off valve opens and closes?
 

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Your bypass in it's normal state is closed, When you start the car a vacuum is created opening the bypass. What this does is creates a path for the pressurized air coming out of the rotors to go back into an area before the rotors. So the air has already been measured once and it will take up the space and be drawn back into the rotors in a circuit until it is used.
No matter what The air that goes through the bypass is going to be used and eventually end up in the intake manifold as you asked before. It just keeps getting recirculated to after the throttle body and before the rotors.

The big thing is that under vacuum the car is going to pull in exactly how much it needs, so all the air flushing through the bypass is just to prevent boost by creating an area where there is no resistance to flow.
 

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Discussion Starter · #17 ·
So the air has already been measured once and it will take up the space and be drawn back into the rotors in a circuit until it is used. No matter what The air that goes through the bypass is going to be used and eventually end up in the intake manifold as you asked before.
I think that the above really explains why the MAF is spiking at throttle opening. The air is getting sucked in but is NOT used instantly. The MAF reads it all at once and "instructs" the ECU to inject a volume of gas that does not correspond to the air that reaches the intake manifold at that time instance. This why I think that the appropriate setup is the MAF just before the intake manifold.
 
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