blackscorpio

I am planning the build for my fourth FD and was wondering if the PFC provideed adequate boost control, or if I would need an aftermarket boost controller.

I am planning to upgrade to a supra fuel pump, and 1680 secondaries with the stock primaries. Keeping the stock twins in seq setup (for now). Full exhaust from turbo back along with an intake. Thinking a FMIC vs a SMIC. Motor will be stock.

Dudemaaanownsanrx7

iTrader: (23)

If you search for Arghx posts on the matter you will find lots of good information. He's studied the pfc boost control quite a bit and has shown it's quite effective in controlling boost once you know what you're doing.. I'm sure he'll chime in here as well.

arghx

iTrader: (3)

1. Yes it can control boost pretty well, but it's easier to tune precisely if you have a Datalogit (something you really should have anyway) because you can actually log exactly what the solenoid is doing. A guy with sequential twins, who goes by Sandro on here, has been using inexpensive upgraded precontrol/wastegate solenoids. These are basically the same as the solenoids used in external EBC's.

2. There wasn't a lot of accurate instructions out there for how it really works, so a lot of people have struggled with it in the past. There are also limitations to the stock solenoids, but again those can be upgraded.

3. I'll admit it's not as adjustable as the most expensive external EBC's out there. I'm not going to go into that too much at this point because it'll get pretty technical.

4. The PFC boost control is integrated into everything else in your car. You can set boost levels on the Commander and it uses the same MAP sensor that's used for the basic fuel and spark control. You can log the solenoid duty cycle, something you can't do on any external EBC. PFC boost control also eliminates a lot of redundant wires and plumbing you would've had. That is one of the main reasons why I use it, because I got tired of my interior looking like a science experiment.

5. If your wastegate is undersized for your setup, you are going to have boost control problems no matter what.

jimes

sorry to hijack post but im trying to find out if i could use any other solenoid with my pfc other than the apexi one? dare i say it i have an impreza but you guys have better tech on the pfc!

Dudemaaanownsanrx7

iTrader: (23)

Yes check out the mac 3 way valves, they can be found between $16-$25 and are the same ones that AEM and haltech use and charge $100+

35A-AAA-DDBA-1BA and 35A-AAA-DDEA-1BA are 2 part numbers that will work

arghx

iTrader: (3)

any solenoid which operates around 30 hz will work. and every boost control solenoid I've seen is in that range. you just have to know how to do the wiring and plumbing. Is your setup internal or externally wastegated?

you could use the Perrin solenoid if you wanted to, the Prodrive, The Haltech/AEM/MAC solenoid, an OEM 2 port from Subaru or Mazda, whatever. see https://www.rx7club.com/3rd-generation-specific-1993-2002-16/alternative-replacement-boost-control-solenoid-531676/ and https://www.rx7club.com/3rd-generation-specific-1993-2002-16/testing-mac-vs-oe-solenoid-valves-other-boost-control-strategies-874031/

basically the electrical connectors used by Apex'i are here:

http://www.bmotorsports.com/shop/pro...oducts_id/1674 solenoid side

http://www.bmotorsports.com/shop/pro...oducts_id/1673 harness side

and here's the MAC solenoid, same that is used in Haltech and AEM applications: http://www.frightprops.com/frightpro...noids.asp#3WAY

neit_jnf

iTrader: (17)

I do believe it controls boost really well. I'm using a pressure regulator set at 10psi prior to the pressure chamber that I read in here was a good idea so the stock solenoids are not overwhelmed when running higher than stock boost.

Here are some boost logs, pfc settings 1.3/100 pri and 1.3/80 sec:

Max primary boost 104 kg/cm2:


transition 68 kg/cm2:


Max boost after transition 116 kg/cm2:

jimes

thanks arghx. ive got std 3 port solenoid which im sure i could use but im not sure the early map sensor that i have goes to 1.1/1.2 bar which is all im after. Also if i turn boost control on it etc menu do i not have to have something plugged into side of pfc?not sure if that would be the map or solenoid when you have the apexi kit?

jimes

what i cant work out is why the stock solenoid cant be set to a target boost pressure? how would the pfc control boost if you didnt have the kit?

Dudemaaanownsanrx7

iTrader: (23)

What I don't understand is why the second map sensor is used in the "boost control kits" it seems like whatever map sensor is being used would work fine since the PFC uses this to base its maps and everything on. Unless the kit is only for MAF cars? I havn't really looking into the RX7 kit much, I've read about it a few times but since it never applied to me I never gave it much thought or studied it too indepthly.

arghx

iTrader: (3)

jimes,

do you have a Datalogit? Can you post up

1) some kind of map from your PFC.
2) a log of you driving around, with only "Advance" being logged in the monitor window?

What I want to figure out is what parameters are loggable on your EJ20 (EJ20K ?) and what options you have available in your various settings tabs. I mostly know 2nd and 3rd gen Rx-7, but I have some knowledge of L Jetro and D Jetro 240sx/Sylvia Power FC's. I also know newer Subarus decently, I have tuned a 2005 Legacy/Liberty with the turbo EJ255 motor using Cobb AP.

One thing I do know about the boost control on Rx-7's: on an FD PFC with sequential turbo control turned off and no harness plugged into the side of the PFC, the PFC boost control stops functioning. The solenoid duty is fixed at 95% and the wastegate will not open. That's why if you want to control boost without their kit, you have to keep sequential turbo control ON and change the transition rpm. I have a friend with the AP Engineering PFC for the series 5 Turbo 2nd gen cars and he has sequential turbo control disabled from the factory. I don't think he has a separate MAP sensor plugged into the side port of his PFC either. But I know the AP Engineering PFC has a different base programming in the EPROM, so it may be different.

I wonder if hooking a MAP sensor into the side port is just their way of ensuring that you have bought some of their products? So if nothing's hooked up there, the boost control won't work. If I actually had the car and the PFC in front of me I could figure it out pretty quickly I think.

the 3 and 5 pin harness part numbers are listed on the Apex'i website now

http://www.apexi-usa.com/products/?id=5355

random fact: the IAT sensor listed for the Djetro kits (Nissan etc) is obviously the factory FD IAT sensor. It even has a Mazda part number (N3A11845)

arghx

iTrader: (3)

log Advance PC% and Advance WG%. That will tell you the actual solenoid duties for the precontrol solenoid and the wastegate solenoid as the boost curve changes. The duty is out of 255. So a duty of 127 is about 50% solenoid duty. Also search through the 3rd gen subforum, you can switch the factory 2 port boost control solenoids with inexpensive 3 port solenoids (same as AEM and Haltech solenoid but without the markup).

jimes

thanks arghx, i dont have datalogit as its hard to come by here at the right price(looking though) my mapper is due next week and he brings his datalogit. As far as im aware the pfc for the impreza uses the stock solenoid,mine being a 3 port but i guess it has only one max boost setting. Then when you turn on boost kit(always forget which is on/off in the jap symbols!) you have to plug in the apexi 3 bar map sensor to the 3 pin port on ecu and replace stock solenoid. There must be a way of using the 4 different boost settings but using stock solenoid.....maybe just add a map sensor?

Sandro

iTrader: (1)

+1 on the pressure regulator.

Just a side comment. Actually, the stock solenoids are "exposed" to the pressure in the PC and WG actuators (same as the compressor boost), not in the pressure chamber.

But I read - as you did - that the many other solenoids valves connected to the pressure chamber may get stuck open if the control pressure is above 10 psi. Therefore, a pressure regulator looks like a good thing to have to have for that reason.

Sandro

iTrader: (1)

Yes, it works well, and it can be improved by using 3-way solenoid valves instead of the OE 2-way valves, as arghx initially suggested to me.

I have a similar configuration - stock engine/sequential turbo, upgraded fuel/exhaust - minus the injectors (still stock) and I posted some comparative results here https://www.rx7club.com/showthread.php?t=874031

For a comprehensive understanding of the advantage of using separate controls for PC and WG, you MUST read arghx thread https://www.rx7club.com/3rd-generation-specific-1993-2002-16/why-engine-so-damn-complicated-part-1-sequential-turbos-demystified-841821/.
No aftermarket EBC allow you to keep separate PC and WG controls (unless you buy two of them)

Have fun with your 4th FD and make sure to get a Datalogit for additional fun.

- Sandro

arghx

iTrader: (3)

Since you do not have a D jetro PFC, you will need a separate MAP sensor. Otherwise, how would the PFC know what boost you are at? Using the Apex'i 3 bar sensor would probably be the most accurate, since I don't think there is a way to calibrate a MAP sensor plugged into the side of the PFC.

the 3 pin MAP sensor harness is listed as part # 49C-A002 . The 5 pin MAP sensor harness is listed as # 49C-A002. Both are listed at a reasonable $15 USD suggested price on the Apex'i website. You would want to buy the harness that corresponds to however many pins are on the side of your PFC. I've never seen an EJ20 PFC so I don't know what it looks like.

The MAP sensor you need is the 3 bar that comes with boost control kits and D jetro kits. It's part # 499-X001 , and it's not cheap. This is not the same sensor that is used with the AVC-R. I suppose it would be possible to use a GM or other such sensor, but without being able to calibrate the PFC for it you may not be happy with the results.