I'm about to do a sort of base PFC map so I was just doing some engine health related testing. Yesterday I hooked up a boost gauge for the first time, and when I found out it was spiking (I think..) to 14 psi, I just about had a heart attack.

It is a jdm car and therefor no precat. However, Im quite sure it has a mid pipe cat delete. I know this is enough to cause the spike but this is where it gets a little complicated.

I posted on a local forum and one person said he thinks a previou owner may have put in "higher boost pills". This is where I realized I REALLY need to better understand the boost system. From what I understand, these pills act as restrictors that make a 7 psi wastegate hold boost up to 10 psi? So if that's true, a "higher boost pill" would be more restrictive? I know the system is way more complex than that but I'm just trying to dum it down so I can more or less see what happening.

He said this 14 psi might not AS bad with ported wastegates but I really don't know if any of that has been done.

So question, no matter what, the stock ecu can't keep up with 14psi. The car is parked until I get things sorted but to what extent can the apex seals take this beating until they eventually go? Are mine pretty toast or is it an either "they're okay" or "it's blown up" type deal?

I plan on finding a stock midpipe to put on and see what happens

That's issue 1.

Issue 2:
Sometimes when I boost, generally heavier boost but not necessarily full boost, and more so in first and second gear than others, I'll let off the gas to change gears, hear the blow off (aftermarket bov, stock otherwise minus mentioned mp and catback) but then when you get back on the throttle, it's much louder and sluggish and won't really build boost. Then with another upshift it's back to normal.

To me this sounds like a wastegate is getting stuck open but I don't know for sure so thought I'd just post.

Last thing is the idle.
First off it's a jdm so it shouldn't have the quick warmup bypass in the tb.. But on a cold start, it goes to about 2.3k for a bit, then after about 15 secs or so drops to maybe 1.2 - 1.3 k. should it not be at app 800?
Then to complicate things more, once it's warm, the idle will sometimes go up and down from 1.2 k to 1.5k. Sometimes it's not bad at all but there's the time where it's pretty bouncy.
It holds a vaccuum at idle of around, 13-14psi I think. Should have taken a better note.

That's it or now. All pointers are appreciated

 

Yes, a simple solution is to install a [non-clogged] cat. You may have bad check valves causing the inconsistent boost pattern. As for the idle--what mods do you have on the car again? Any time you post a question you need to begin by very clearly listing the exact modifications the engine has at this current moment.

 

The stock wastegate isn't able to regulate boost pressure beyond a certain point, so pills or no pills with an open exhaust you're going to get spike and boost creep. You either need a ported wastegate, tuning to compensate, or something to restrict the exhaust.

With regards to the seals, there can be other detonation related damage not specific to the apex seals, but generally with stock seals they either hold or they don't. They can crack, but it's almost always a catastrophic failure in a detonation situation.

 

okay sorry,
The mods i am aware of, (at least engine related) are the BOV, which imo shouldn't matter. It's just attached to a hose that would normally just vent into the atmosphere from the airbox. It's a shotty job but the previous owner said he just had it for the sound.

Then according to the ad, "Greddy catback with midpipe cat delete." However, I'm quite sure that after finding a fujitsubo pamphlet in the car, and looking up pictures, it's a giken or a legalis r catback. As for the midpipe, i will have to have a look underneath the car but I guess I shouldn't have called bs on that part just cause he didn't know what kind of catback was on it.

then it has the jdm down pipe which as i'm sure you're aware of has no cat. As far as i'm aware, that is everything modded in the engine.

And i am not going to lie, I don't know alot about the boost system yet but i will definitely read in to the check valves and get back to you on that.



With regards to the bolded section, what i'm getting from this is that the pills are more than likely unchanged. Just out of curiosity though, is it easy to check or would they be piled under everything near the turbos? Just wondering if making the trip to the car is worth it or not seeing as how it will be more or less torn up in a few weeks anyways.

And as for the rest, i guess the rotary gods are looking over me
Time to play it safe

 

You need to read up more on how a basic internal wastegate and electronic boost control system works. Read this article: http://www.perrinperformance.com/pages/show/113

The FD uses an internal gate with a 2-port bleeder solenoid and a restricter pill. It is just like the one described in the article except for a minor variation in the plumbing on the actuator.

 

The JDM TB's do have the cold advance system. I deleted mine. I would keep this on yours as you're in Canada. You can supposedly start the car in gear with the clutch depressed to bypass the cold start.

If your idle is bouncy, I would recommend checking out the service manual and test your TPS to see if it's in range. Also do a search for dashpot and make sure this is working properly, I removed mine with no ill effects, but it can mess with the idle if not adjusted properly.

I had all the same symptoms you have, once I deleted the cold start, and dashpot, then adjusted the idle screws (both) and adjusted the TPS it runs sooooo smoothe at constant 800 rpm.

 

Another option on the boost issue (temporary) would be to change out the vacuum lines that hold the restrictor pills. Use regular vacuum lines and it will drop your boost to 7 psi, which will be much safer even if you still have boost creep, but shouldn't.

Another thing that will cure a big part of your issues is getting a power fc. I just got one installed and it cured 95% of my idle/drivability issues. I also blocked off everything except thermowax and coolant line to tb and the ISC.

 

okay, read the article, made sense. I understand more or less whats happening. I still have some FD boost specific stuff to read through but before I look too far in, would getting very little boost cause the engine to make the louder raspier noise?

in canada yes, lol, but unless the weather is good enough to roll with the windows down, the fd hides in the garage.

after looking at a few threads about dashpot and tps, I'm pretty sure this will fix the idle. one person had pretty much my exact symptoms. Just not 100% sure what the dashpot is. I know its rubber. I`ll post pics tonight to verify if what i'm thinking is right

Thanks for the boost option, but I don't feel entirely comfortable modifying my vacuum lines other than replacing them. I don't fully understand how the boost system works yet so until then, mazda spec will have to do. I haven't driven the car since i found out about the spike but if I needed/wanted to, it's not that hard just to be light on the foot.
Wait...


nm.



and I am getting a PFC shortly. Should be shipping by now but I just wanted to make sure it was running in tip top shape before modding. But good to know some of the pressure is off for fixing the idle.


Thanks for the replies, guys