Hi everyone,

I have a spike on the secondary @ 17 PSI!!
My pattern is 11 - 8 - spike very fast @ 17 - back to 11

I'm really concerned about my apex and thus cannot enjoy full throttle accel.

My major mods are:

- HKS RS Intake
- 3" DP
- rx7store HF cat 3"
- XS-Power 3" catback
- Efini Y-Pipe
- PFS SMIC
- HKS elbow
- JDM Knightsport 4beat ECU supposed to support these mods (fuel cut eliminated)

Now, I wonder what would be the best solution to eliminate this spike and recover normal boost pattern.

I thought of restrictor plates, but what's the point having a 3" exhaust line then. I could still put the stock muffler back, but this baby is way much heavier than my catback...

I've seen people porting their waste gate, but that's to eliminate creeping issues, which I don't have.

Then I thought of an electronic BC, such as the GReddy Profec B2. But before to invest $350, I'd like to make sure it will do what I'm expecting from it.

Thanks in advance for your advices.

 

You really need some kind of boost controller.

For $100 you can install two boost controllers like these:
http://www.boostcontroller.com/index...26category%3D4

Or you can make your own.

Dave

 

So according to you no need to use another solenoid than the stock?

 

You remove the two vacuum lines running from the compressor nipple to the wastegate and precontrol actuators. Install a manual boost controller with vacuum lines in their place.

Next remove the lines on the other nipple of the actuators. Cap off these nipples on the actuators. Use a rubber cap material that can handle high heat (EPDM or Silicone) or else you'll be shortly having more boost control problems. Finally you can remove the rest of the vacuum hoses running to the stock wastegate and precontrol solenoids. https://www.rx7club.com/3rd-gen-archives-73/my-boost-control-setup-perfect-10-8-10-pattern-178136/ (note in the linked thread that Damian eventually got better results with the actuators capped like I described).

Take care to begin with the boost controllers wide open and slowly turn them down. The precontrol is used to adjust boost below 4500, the wastegate is used to adjust boost above 4500.

Dave

 

All right I'll try that.

Dave, thanks for the help!

 

Just bought 2 Hallman MBC, found them less than $85 for the complete RX package on ebay!

I hope this will fix the problem.

 

Let me be sure I understand the set-up correctly:
- I replace the restrictor pills lines with normal hose and put there 2 MBCs
- I remove the remaining hoses that go from the actuators to the solenoids and cap the nipples
- no need to cap the solenoids I guess?

The 2 solenoids we're talking about are the ones showed in the picture right?
(thanks for the pic Ernesto13B)
They are accessible by removing the pressure chamber right?

The 2 lines I get rid off are the pink and green ones coming from the actuators to the solenoids in this diagram, correct?

Sorry for the repeating but I need to be sure.

Thanks guys.

 

just a quick confirmation guys?

 

a) correct
b) and c) When I installed my MBC's, I just put solid (no hole) pills in the lines from the actuators to the solenoids - this blocked both off with one simple addition.

Here is a link to MBC threads I am familiar with: https://www.rx7club.com/showpost.php...6&postcount=10

 

Thanks Dave, so that's what I understood, good.
Either you cap off or you let the lines in place but stucked/stuffed with a plain pill or something. Easy way if you cannot find caps, which is currently what I'm struggling at right now!

Thanks guys. As soon as I receive the parts and install them I'll post here the results.

 

Caping the other nipples of the actuators and the solenoids: why?
Will this not fool the ECU and fuel injection parameter, the ECU not seeing the boost level?

 

The ECU senses the boost level by the MAP sensor that's on the firewall. The solenoids are a VERY simple output - the ECU gives them a fixed duty cycle at certain RPM's, and they do their thing. There's no feedback, other than the ECU can tell if they're electrically plugged in or not.

Personally, I'd put in the boost controller, remove the stock solenoids, and cap up the vacuum lines that went to the solenoids. Clean, neat, and works just fine.

Dale

 

All right crystal clear now, knowing that the only feedback the solenoids give to the ECU is that they are electrically plugged in or not.

Thanks Dale

 

Ok today I installed my MBC, just one thing I didn't do because lack of time was removing the lines to the solenoids. So basically just replaced the pill lines by the MBC.

Went for a test drive then with MBC fully open:

Terrible: boost is going up like hell, I hit fuel cut around 4000rpm @ 1.2kg/cm² of pressure. Looks like creeping, never experienced that before.

I thought that just replacing the pill line with the BC fully open would mean great drop of pressure!! Not at all.

Can someone explain me what's going on? Is it just because I let the solenoids lines on??

 

Is your boost controller wide open? If it is closed you will boost until your engine blows.

 

Of course it is. I'll check tomorrow if air is passing in it though, seems really weird to me.

Could the solenoid being still plugged in be the cause??

 

I'm not sure what sort of MBC you have but some ball-and-spring MBCs are orientation-dependent: if you put them in backwards then they will not open.

 

I caped the vents to the solenoids and everything works just fine now. That was it...

 

OK, so now I have solid boost control EXCEPT for the spike...

I still have a spike and can't go back to the 10-8-10 pattern, I have 10-12-10 instead.

I need to fine tune may be but anyway: any ideay on how to get rid of this f...... spike?

 

Turn down the precontrol.

 

Hmmmm...

Doesn't it work the opposite way? If you turn down the primary boost level, the spike should increase due to more exhaust routed to the secondary, pre-spooling it more, causing a larger spike.

Dave

 

I guess empiric testing will tell us, hopefully.

I'll try different solutions in the safe zone and will post here.

Thanks guys.

 

I found the best settings were 11 psi on primary (precontrol) and 10 psi on wastegate. That gave me (approximately) an 11-11-10 pattern.

Dave

 

Thank you Dave you're right. "Turn it down" wasn't the most descriptive answer - really the trick is to focus on the precontrol adjustment. To lower the spike you need to raise the boost seen at the primary turbo.

Rob Robinette wrote quite a bit about it:
http://www.rx7.org/Robinette/boost_controller.htm

 

You're welcome. Actually, I figured you knew what you meant, but Oliv might not.

Dave