So my 93 RHD FD has a midpipe with a highflow cat and a nur catback. And about 40% of the time i do a 3rd gear pull it will boost cut/fuel cut at 5000+ rpms. Ive stopped doing 3rd gear + pulls for the time being so i don't blow up my car.. I was doing some searching and most people say to get a good EBC to control the boost spikes. I was thinking of getting a greddy Profec e01 (tho its a lil big for my liking) or a Apexi AVC-R.. but im not exactly sure if either will get rid of the overboosting for me. What kind of EBC do you guys recommend me using to control this? Or should i just say screw it and get a regular cat on my midpipe?

 

With those flow mods you'll need a boost controller. It need not be electronic, manual boost controllers perform equally well. Electronics are just more convenient.

Depending on how well your intake/exhaust flow, you might still find the boost creeping when you stay hard on the throttle for more than a couple seconds and/or on colder nights when the air is densest. If that problem arises you will need to port your turbo wastegate. Boost control systems will not be able to stop boost creep. For now anyway I would make the adjustable boost controller your priority.

Dave

 

Greddy Profec B.

And a PFC in the near future.

 

i had the same problem when i had my twins

there is something u can do just to drive normally

it will keep you at 8psi but u will be able to pull in any gear 1 2 3 and its safe wont hurt any thing


there is a nipple on the side of your lower wast gate...just cap it and the other side of the line and if that takes care of your problem u might have bad solenoid

..the other thing run the straight pipe no cat you will love it big big difference ..turbo spool way faster

 

do this mod. it works like a dream. like no ones business. i love it!
https://www.rx7club.com/3rd-gen-archives-73/my-boost-control-setup-perfect-10-8-10-pattern-178136/
and definitely port your wastegate if u still get boost creep.

 

This solution may help but it is not addressing the problem.. DO NOT install a straight midpipe. This is increase the problem you are having.

Like Dave recommended first invest in some sort of boost controller. I have a Profec B SpecII and it works just fine.. Many others on here run the apex and like it too. It is really personal preference when it comes to EBC's.

Second, I would REALLY consider Dave's second piece of advice and invest in a PFC or some other aftermarket ECU. It will help the motor by having it tuned correctly.

Having the wastegate ported is really a good idea. Possibly necessary in your case but even if it is not it will not hurt anything. With a ported wastegate and a properly tuned EBC your turbo's will spool even quicker than stock (which is pretty damn fast).

 

My experience is that boost creep can indeed be the result of intrinsic limitation of the boost control system.

I have PFC, unported WG, and no cat - by the way turbo spool is indeed way faster with no cat as serbRX7 said, big big difference and I love it.

I experience boost creep but concluded that it is PFC-related. The PFC controls boost by cycling the WG actuator bleed solenoids valves.

In the PFC, you set a target boost value and an "initial" solenoid valves duty. Then, supposedly, the control system would work in closed loop to compensate for the difference between actual (measured) and target (which you set) boost values by adjusting the solenoid duty. If the actual boost is higher, the PFC would reduce the bleed solenoid duty - which would cause the WG actuator to open more.

The problem, however, is that the control range of the PFC is quite limited - I found out from logging that it's no more than 15% from the "initial" duty cycle. So, if you set a relatively high "initial" duty cycle, say 75% , and you overboost, then the PFC would only reduce the the duty cycle to, say 60%. At this duty cycle though the WG would only be partially open and you would experience boost creep. I then reduced the "initial" duty cycle to 30% and there was no boost creep at all. The problem though was that with such a low "initial" duty I would only boost to 10 psi.

For further details on PFC boost control operation (which I understand is similar to the stock ECU ) go to this excellent thread by ARGHX
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/why-engine-so-damn-complicated-part-1-sequential-turbos-demystified-841821/page2/

My conclusion is that before rushing and port the WG you should take a hard look at your boost control system operation and make sure that it is capable of of fully opening the WG under overboost conditions. I have no direct experience yet but from what I have been reading the Hallmans and EBCs may be more effective than the PFC on this regard.

- Sandro