gio64

iTrader: (1)

Hi everyone.
I am going to explain the situation, then move on to the questions.

Background:
I installed an AEM EBC last fall, but never got around tuning it, as the weather got worse.
Reason for installation was that with a couple of mods I had found myself boosting past 10 at about 11 (give or take) and I wanted to go back to stock boost to avoid any problem.
At the time of installation, I looked at the three different ways of routing the vacuum hoses to control boost (Version 1: EBC controls primary only, stock solenoid is capped; version 2 EBC controls both, both stock solenoids are capped; version 3 -"sweet"- variation of version 2).
At the time, I didn't really see any difference between routing the version 2 way or routing the "version sweet" way, so I opted to go with "version sweet" as it is in my opinion simpler (link to the three diagrams: https://www.rx7club.com/showthread.p...=version+sweet there was another thread, but I cannot find it at this time).

Today

After studying and trying to understand how to tune the EBC, I went out for a ride.
I have learned that the AEM should be setup as follows: first increase duty cycle until you get desired boost (in my case, I want to stay at 10); then go to the spring setting, increase psi 1 by 1, when you hit a spike, go back to the previous setting.
I did this, but while I reached 9.x, I noticed that the secondary doesn't come online. What has happened a couple of times, is that the boost dropped and came back up intermittently 2 or 3 times at about 6k, after which I let off.

Here are the questions

1) I have installed both my AEM Tru Boost EBC and the mechanical gauge on the same line that comes in the car, "Teed" right before both gauges -sitting side by side).
There is about 1.5 to 2 PSI of pressure difference between what the mechanical and the digital gauges read. What is up with that? The mechanical gauge reads more vacuum and more boost than the digital. What should I do and which one should I use as reference?

2) After reading some more today, my guess is that the reason why the secondary doesn't come on line is because of my routing the "version sweet" way. I really have nothing else to guess in regards to that. If anybody can shed some light in that direction, I would be really grateful. My intention is to go back and re-route as version 2, but if anybody has any insight on this entire matter, I'd like to hear about it.

Thanks in advance boys, and please give me a hand here, I am in a bit of a bind.
Giovanni

PS The car runs otherwise well, there are no problems of any sort.

scotty305

iTrader: (2)

The 'version sweet' routing makes no sense to me, I can't see how this would allow the boost control solenoid to have any effect on the precontrol actuator since it is not directly routed to it. The fact that the drawing is titled 'version sweet' makes me question that person's understanding of physics and mechanics.


It sounds like quite a few people have used the Version 2 routing and had good results, that is what I would try unless you have a very thorough understanding of how those actuators work and how the vacuum lines are interacting with them.

gio64

iTrader: (1)

Thank you for the input.
You see, (and this is not to argue about it, it is rather to explain what sense I make out of it), when I look at version 2 and version sweet, I don't see difference.
Here's why: in version 2 you have a vacuum/pressure line going into the stepper motor (the line is made up by coupling both the lines "out" used by the stock system). As well, there is one line coming out of the stepper motor in version 2 that is split into 2 going to both the wastegate and the precontrol (or whatever the second one is called, forgive my ignorance). This means that if the line(s) into the stepper motor see pressure, this pressure is sent to both the wastegate and the precontrol, with the stepper motor in the way regulating the flow.

In version sweet, you have one line coming into the stepper motor, one out to the wastegate, which is then routed to the PCA. If you look at V 2 and V sweet, the pressure entering either the wastegate control and/or the PCA are each other dependent.

I may say something stupid here, but for the wastegate to see x amount of pressure in V 2, there has to be the same amount of pressure in the PCA. If they are operated by a diaphragm, the pressures on the 2 diaphragms depend on each other, indifferently in V 2 and V sweet. I look at them like if they were 2 balloons connected to the same pressure line. Wastegate balloon inflation amount will be related to the PCA balloon inflation amount. Whether you send a line to wastegate balloon and then out to the PCA balloon or you split a line and send the splits into each of the balloons, the amount of inflation shouldn't be different.

I will admit that this is partially theoretical, as the pressure/vacuum in the lines is variable and not constant. So, there might be a difference in the speed at which one routing makes the system react in relation to the other.
But there shouldn't be any reason for the secondary not to come online.

Now, I might have said a bunch of nonsense, but my purpose here is to
a) fix the problem and
b) learn more so,
If any of the "local" gurus can chime in and explain the flaw in my reasoning, I would really appreciate it, as it resolves my problem and I learn something out of it.
Giovanni