kob345

First I just want to say this forum has helped me learn a ton about FDs, lots of good information here and a lot of good people willing to help.

Okay, so after much searching on these forums, AEM forums, Google, and just about everywhere else I could think of I can not find any info on this problem I am having with the boost controller.

I have had the gauge set up for a little while now without the solenoid installed and decided this weekend I was going to put it in. So I got it all set up according to info in various threads in the forum. Mostly:
https://www.rx7club.com/showthread.p...+boost+install

So my problem is, after having installed the solenoid today, I took it out for a spin, got it to 4th gear at about 40 mph, slowly started accelerating watching the boost gauge.

My pressure went up to about 7psi then climbed really quickly to over 13... so I let off the gas and pulled over. I check the settings on the controller and notice the A setting is really high, 67%.

So I reduce it all the way down to 10, the lowest setting. I also take the B setting and the Scramble setting all the way down too just to be safe, and set the spring pressure to 1. I give it another run and same thing happens.

I'm starting to think the solenoid is bad but wouldn't that make the boost not go over factory settings? or that the gauge is broken, but it read boost pressure just fine before, had a good 10-8-10 pattern, also, it shows the right/same vacuum right now.
Any help would be greatly appreciated, thanks.

Supernaut

iTrader: (83)

O man don't use scrambled boost please. Not a good thing for rotarys my friend.

Erix7rew

iTrader: (7)

Hi' set the spring setting to 7psi and set your ''A'' boost setting to 40% and test it. You should be at 8-9 psi at 40%. after that raise your boost by increment of 5% until you get your 10psi.

The stock wastegate open at 7psi, this is your spring setting.

If i remember, mine is set to 55% to get 10psi

Good luck

arghx

iTrader: (3)

Are you sure you hooked it up right? Which ports did you use? If you are hooking it up to the wastegate actuator only (precontrol solenoid still installed) You should use this diagram:



and cap the other port on the wastegate actuator. Port 3 is the middle port. It is the equivalent of an "NO" (normally open) port on a Greddy/Apex'i/HKS/Denso solenoid. Port 2 is your "COM" (common?) port, and Port 1 is your "NC" (normally closed) port.

In your current configuration, if you physically unplug the solenoid (but leave the gauge hooked up) what happens to the boost? It should run at spring pressure if everything is hooked up correctly.

kob345

Ive got the solenoid hooked up like "version 2" in this diagram:

https://www.rx7club.com/attachment.p...7&d=1189113324

Except I'm only using the one T at the wastegate/PCA, seeing as the "existing source" has two nipples for the same thing.

I will try unhooking the solenoid today after work.

And note that even though the Tru Boost is at the lowest settings, it is reading boost up to 16 psi. Definitely not good for the engine.

Also, there are no mods on the car besides an Apexi intake, its a 94 with a pretty much stock engine to my knowledge.

Erix7rew

iTrader: (7)

Likea i say it is normal that your boost raise a lot with your spring setting set a 1 psi. Set it at 7 psi and test!

HardHitter

iTrader: (4)

I have the TruBoost and make sure that your vacuum hoses are not crimped. For example, coming off of my wastegate, the hose didn't have enough slack and it created a crimp in the hose which led to a major boost spike (20psi) when I was only tuned for 15-16psi. Simple fix and check that could happen when installing.

arghx

iTrader: (3)

The thing you have to realize is that diagram is for a stepper-type EBC like the old Greddy Profec B and the HKS EVC. The diagram is not for a 3 port solenoid. If you used the wrong ports on the solenoid, you will have the same symptoms you are encountering.

dakman

so i was thinking of getting the true boost but i wasn't sure if was compatible with the rx7's sequential turbos and if it is then do you just use the diagram you have posted?

Thanks

kob345

Okay so I took the Rx7 out for a spin after checking the vacuum hoses for crimps, got it into 4th at about 40mph and starting accelerating, watching the boost as soon as it climbed over 12psi and stopped.

Then I increased the spring pressure to 5 psi, tried it again with the same results, then upped it to 7 psi as suggested and gave it another run, same thing happened.

So I decided to turn it off and was going to do one more run. However, when I tried to do so by holding down on the left button for 2 seconds, and toggling through the modes, I got the error message "ERs".

Looking in the manual:
ErS- If the boost solenoid is shorted or disconnected.

I'm pretty sure its hooked up properly, the instructions say that the polarities do not matter, so I just connected one to the same place I connected the positive on the gauge, and grounded the other.

Is this the way you others have done it? I this the wrong way? If so, advice is always appreciated.

Can someone who has this boost controller, or any with a solenoid, post how you connected it? with pics if possible.

What I did to hook it up was as I said, "version 2" of the diagram with the stepper motor:
I took one hose from the turbo and put it on the solenoid, capping the other nipple.
I then connected the "in" ports on the wastegate actuator and the precontrol actuator via a tee and hooked up the remaining end of the tee to the solenoid.
Then, I disconnected and plugged both "out" ports for the actuators.

That's all I did, did I miss something?

I'm to call AEM now and see what they have to say.

arghx

iTrader: (3)

Boost controllers are all the same. Ok, not literally, but they are very close. There is nothing unique about the AEM Tru Boost. It is one of the simplest electronic boost controllers available. It works just fine with sequential turbos.

As far as the diagram I posted, on a car with sequential turbos you can have a T splitting the pressure coming out of port #2 on the solenoid. The T goes to the precontrol and wastegate.


This hose should be connected to port #3.

The "remaining end of the tee" as you call it should be connected to port #2. You must NOT make the mistake of connecting either hose to port #1. That would cause your wastegate not to open.

arghx

iTrader: (3)

here is a quick and crude MS Paint diagram



Make sure you do not hook up anything to port #1, the port on the right that is depicted as having a muffler screwed into it.

Erix7rew

iTrader: (7)

^ also check the port number on the solenoid because there not at the same place in the diagram

kob345

So the problem wasn't the hoses, but I'm glad of the drawing, reassured me quite a bit.

I called AEM, and explained the problem to them. They told me it was most likely an electrical problem and asked me how I had hooked everything up.

I told them I had connected the solenoid to the power and ground and explained to them that I had 2 separate wire bundles... They told me there was only supposed to be one that split into a 5 wire and a 2 wire cord.

After much confusion on my part, the tech finally drove into my skull the proper set up, I'm not going to lie, electrical issues are not my forte. Anyways, the problem was I had not connected the solenoid to the gauge, essentially I had locked it in the open position, or whatever it is when its energized.

So after I got everything together like it was supposed to be, I double checked the the hose configuration and compared it to the picture that was so graciously drawn for me, thanks again.

I jumped in the car set the gauge to "A", got it into 3rd and stepped on it, the boost did not go over 8-9! So now its working all I need to do is adjust it.

Once again thank you to all who replied.

stompz

iTrader: (4)

This is an old thread that I'm reviving because I'm currently playing with my AEM Tru Boost and figured it is still a relevant topic.

This is NOT CORRECT. The waste gate spring pressure may be 7 psi but setting it as the SPr (waste gate crack pressure) is not right. If you do this, you will get boost oscillations. See AEM Tru Boost video 3 for some more explanation: http://www.youtube.com/watch?v=sWmIhKJmtbU

The reason for this is all in the definition. Waste gate Crack Pressure. CRACK, not spring pressure. I haven't tested this with my Mityvac yet, but I can guess that at ~4psi the waste gate begins to open. Arghx, if you read this, do you know for sure when it begins to open?

The proper setting, according to AEM is ~3 psi less then the waste gate spring pressure. That would be 4 psi for the SPr setting. I haven't fine tuned it to spool as fast as possible, but I do know that somewhere between 3.5 and 5 SPr pressure will be the sweet spot for twins.

When I set my Tru Boost to SPr 4 and a duty cycle of 50, I was holding 8-9 psi steady with no boost spike. When I set the SPr 3 and duty cycle of 50 the spool up time was ssslllloooooowww. SPr 5 and duty cycle 50 I had overboost by about 2 psi. So, with ROUGH settings, SPr 4 and a duty cycle of 50 or 55 should be close to stock 10-8-10 pattern.

I'll update this and take a picture of the MS paint diagram that Arghx has drawn up (and I have implemented) soon. I'd like to find a rock solid number for the settings so other people can reference this.

I don't know if this matters but I'm currently running PFC, AEM UEGO wideband, polished aluminum intakes with K&N filters, 99 spec Y pipe, stock IC and Greddy intake elbow. My engine is street ported with 3" downpipe, no cat and Racing Beat single tip catback.

thewird

iTrader: (8)

A higher SPr would make spoolup quicker, not slower. That is the point of using it, it keeps the gate closed up to that PSi. You want it as high as possible without causing boost spikes on spoolup. The manual instructions are just a dumbed down version for people that don't know what they are doing. 4 PSi before your target boost is a better description for how to tune it and depending on your setup, you may want more or less. For twins, it doesn't really matter though, they spoolup quick anyway.

thewird

Erix7rew

iTrader: (7)

Yeah i was wrong and the crack pressure of stock twin wastegate is 4psi. At 7 psi it is full open. So your Spr setting should be 4psi!

arghx

iTrader: (3)

[QUOTE=stompz;11086638]The reason for this is all in the definition. Waste gate Crack Pressure. CRACK, not spring pressure. I never measured on the FD. I did test the stock turbo on an 89-91 FC though. It was a while back but I recall the valve first lifting off its seat at about 3psi and full open was around 6-7psi on that turbo. That actuator has a controlled leak/vent built into it. I don't recall if the FD's stock wastegate actuator is like that or not.

as thewird implied, these instructions are more of a guideline and as such it presents rules of thumb for general use.

It never hurts to post your experiences for other people to consider. However, the AEM Tru Boost is just a dumb solenoid driver. It doesn't even know it's hooked up to a vehicle and it doesn't care about the specs on your wastegate.

The only thing it can read is 1) pressure through the on-board sensor and 2) time through some kind of on-board counter. The only thing it can put out for purposes of this discussion is an ON/OFF signal to the solenoid.

It doesn't know what rpm you are at, it doesn't know what gear you are in, it doesn't know how much air is entering the engine, it doesn't know if you are knocking or not. It doesn't know your throttle position. It doesn't even know what boost you want. It has no feedback or "intelligence" to it. To be fair, most of external EBC's on the market are like this overall. They may have some crude feedback system but that's it. More complexity costs more money and would only confuse or otherwise turn off owners. And as counter-intuitive as it may sound, you have to "teach" a "self-learning" system so that it learns correctly. Look at how many people don't like or don't take advantage of a controller like an AVC-R with its many features. So the AEM Tru Boost is a dumb boost controller and it's dumb for a reason.

The "Spring" setting just drops the duty cycle down to (or near) whatever you number you set. You could set a 10psi "Spring" setting on a turbo with an 8psi spring, if you were planning on running say 16psi.



So in that conceptual illustration above, you have a "spring" settnig of 4psi and a "duty" setting of 50%. Changing the "spring" setting moves that red line left or right. Changing the "duty" setting moves the right side of the blue line up or down.

That's all it does. That could make you overboost or underboost. The ECU could trigger fuel cut or the engine leak all the boost out. The AEM Tru Boost doesn't really know and doesn't really care.

The mechanical aspects of the system are what determines how the engine responds to that duty cycle curve. That includes the level of intake and exhaust restriction, the charge piping and intercooler, the sequential turbo system actuators, the port timing... Finding values that accomplish your goal for your engine may not necessarily do the same thing for the next guy.

It's just a controlled ON/OFF switch, that's all.

stompz

iTrader: (4)

Just to be clear, I'm not trying to argue whether or not the TruBoost is an intelligent boost controller or not, I was trying to clear up an incorrect setting that could be used by forums users.

Most times, IMO, simple is always better then complicated. The AVC-R is way more robust than the TruBoost but... that's the problem. I'd wager 90% of the end users have no idea how the AVC-R works or how to tweek it. The TruBoost is extremely easy to operate. All it does is cycle the wastegate/pre control actuator (assuming they're Y'd together) at a duty cycle.

These are the results that I've seen across various settings with my TruBoost. I have not settled on a value yet, so I'm not posting these are my final settings. I can tell you this, based on experience on my FD (some numbers eliminated due to redundant results):

Spr = Waste gate crack pressure

SPr | Duty Cycle | Results (relative to the previous test)
3 | 50% | Verryyyy slow spool time, not ideal. PSI held ~8psi
3.7 | 40% | Decent spool up, somewhat slow, minor 1psi spike. PSI held at ~8 psi
4.0 | 40% | Faster spool then before, still a minor 1 psi spike.
5.0 | 40% | Faster spool but a more severe spike, ~2 psi
6.0 | 40% | Fast spool but results in oscillations at max psi
7.0 | 40% | Similar to 6 SPr, still oscillates badly

I set my PFC to graph mode to monitor boost levels as the TruBoost does not easily monitor for a boost spike. You can an alarm setting on the TruBoost for overboost, but I have my alarm set at 15 psi for a severe spike.

As a disclaimer, I'm not an AEM engineer and I'm not a FD tuning expert. I'm just some schmuck posting his results.

My conclusion after the first round of testing is this (for sequential twins). Anything at or higher than 5PSI for waste gate crack pressure will result in a boost spike or oscillations. Settings the SPr pressure setting to something like 3 psi less than your target psi (say SPr = 11 if target boost is 14 psi on stock twins) will result in undesirable results.

My main goal for using the Tru Boost as a boost controller is to limit the amount of boost that I can produce so I can eliminate the possibility of detonations, knocking and peaking my injectors.

Will post more as I finalize my settings. My target psi during these tests were always at or below 10psi. I'll raise them up as I go.

Mrmatt3465

iTrader: (10)

As for wastegate opening and cracking pressures:

I recently tested my actuators using my Mityvac for operation and opening pressures. Per FSM, both actuators should "move smoothly at 10-14psi". As I slowly pumped pressure into my actuators, I noticed they cracked at closer to 8 psi and were full open by about 13 or 14.

Matt

arghx

iTrader: (3)

Another method to try is starting with the duty cycle a lot lower, around 20%, and alternating between increasing the "SPr" and duty cycle settings. I'm not sure why you started with duty cycle that high. It's not surprising that you had oscillations like that. You are using a 3 port solenoid which is a lot more sensitive than the stock 2 port solenoid. You also have a catless exhaust.

You can't say that an "SPr" setting causes spikes with any certainty. You never even tried duty cycles below 40%, and you are using a catless exhaust.

stompz

iTrader: (4)

I can try a lower duty cycle to see if it changes the response of the SPr setting. I started at 40% b/c of a recommendation by another FD owner. This is a learning procedure for me, I'll try a SPr setting of 7 or 8 as Mrmatt3465 has tested with a low duty cycle.

I can confirm MINOR boost spikes with my car and the setups I listed just by being able to watch graph mode on the PFC. I don't have a Datalogic so I can't provide the logs. With a duty cycle of 40-50% I was seeing boost levels around 8-9psi. I'd see a minor spike to 10 or 11psi by seeing the curve on the PFC and recalling the max boost on the TruBoost. The spike is within normal tolerances. I believe.

arghx

iTrader: (3)

Generally speaking with these types of controllers you want to go for a small overshoot of the target for best spool. But if you're really concerned about something going wrong when the weather changes, you will have to tune for slower spool. The more advanced boost controller systems (standalones and stock ECUs) have feedback functions and temperature correction tables.

agent004

iTrader: (13)

I am using my AEM Tru Boost as just a gauge now. Just recently I started noticing that my Tru Boost is reading numbers like 20psi when you bring up max boost. I'm only tunned for 15psi controlled of my 15psi waste gate spring. When I query max boost in the FC Commander is displays 1.03 (bar?) which seems to match what I would expect from my 15psi waste gate spring. Is there a way to calibrate the gauge on the tru boost, since I think it is diverging from the actual value?

tangoshark

iTrader: (18)

This thread should get FAQ'ed