Some turbo system questions

[AutoEuphoria]

OK,

After dealing with this:

http://www.mazdas247.com/forum/showthread.php?t=123755510

I changed back to the stock BPV and went on another test run. Same location, same gear (3rd). Seemed to be a little better, but not much. Here is the new datalog:

So...
- Boost is still down to basically nothing before 5000RPM (yes, that is 0.73 psi at 4918 RPM)
- Fuel pressure is still down
- Wastegate seems to be closed while boost is going down...boost leak?
- AFR still seems to be safe

So I am thinking I have a major boost leak somewhere. Would this be safe to assume considering the wastegate is closed (0%) as boost is dropping? Where would a boost leak like this even come from? Also I noticed the boost was jumping all over the place as it was loosing pressure...it would bounce around 10, then around 5.

Another quick question...I just wanted to make sure of a couple of things regarding the stock turbo system vacuum lines.

Question 1:
Is there anything special about any of the lines in the turbo vacuum system (between turbo and WG, WG and BCS, BCS and intake)? Any unique sizes or restrictor pills or anything? I replaced the stock vacuum lines when I had the MBC, and put just regular line in when I took the MBC out.

Question 2:
Is this the correct order for the vacuum lines?
Turbo to bottom of wastegate actuator
Top of wastegate actuator to nipple on boost control solenoid closest to the front of the car
Nipple on boost control solenoid closest to the rear of the car to the intake

Thank you for any help!

 

[Speed3Rookie]

did you just start loosing boost when you replaced the stock vacuum lines?
do a search on manual boost control install and you will find pics of where the stock vacuum lines go.

 

[AutoEuphoria]

I really just started noticing it when I removed the MBC and MAP clamp...it's weird that going back to stock created this kind of issue.

 

[AutoEuphoria]

Would a weak MAP sensor signal cause this?

 

[8.5MS3]

your wastegate duty cycle is 0% - that means its wide open. 99% means its slammed shut trying to build boost. Looks like a boost solenoid problem

 

[AutoEuphoria]

AH, so it's reversed...OK that makes a LOT more sense. Thank you.

 

[8.5MS3]

np but that still doesnt explain the fp issues. do you have the stock ones? ive heard the aftermarket ones have a relatively high failure rate, might want to switch back to stock. 430psi should be at idle only. that could account for the wastegate staying open - protecting the engine

 

[AutoEuphoria]

That would also make sense. That's kind of the issue I was trying to get to...the chicken and egg thing. Does the ECU dump all the boost because of the low fuel pressure, or does it lower the fuel pressure to keep the AFR "normal" when the boost is lowered?

The reason why I would suspect that the fuel pressure is being lowered by the ECU is because it was working fine when the MAP clamp and MBC were installed, and stopped working right after. However, the boost control solenoid was bypassed during that time. So as soon as the BCS was reconnected to the system, it stopped working correctly. Fuel pressures were perfect before then...rarely dropping below 1100-1200.

 

[8.5MS3]

the boost would be dropped at the first sign of low fp, since the pump cant flow enough fuel into the engine at high boost, it will cut the amount of air going into the engine. although it would only cut at higher revs.

There are 2 ways to inject fuel - low pressure longer duty cycle or high pressure shorter duty cycle. there is a limit to the 1st scenario which is the reason boost gets the axe once the pressure drops off at higher revs - not enough time. I would recheck all the solenoid connections. chances are something was put back incorrectly or theyres a faulty ground or short somewhere from the boost controller/map clamp removal - no offense. I took my car out for a test drive and forgot to tighten the worm clamps on my boost tubes once.....talk about shitting your pants lol

also dont forget this engine depends on DI to cool the cylinders at high boost to keep knock and detonation at bay. so, at low fp i would expect the motor to go into limp mode.

 

[AutoEuphoria]

OK, here's a mini-update:

At lunch I disconnected the battery and checked the vacuum lines to and from the solenoid. Everything there looked good. After lunch I connected the battery again and tested it a little. For the first couple of minutes everything seemed to be working perfect again...fuel pump was making between 1100-1600psi while I was on it. However, after a couple of minutes it started doing the same thing again. This gives me some hope that it is not the fuel pump (why would it work perfectly again if it were broken?). After work I am going to check the wires I had to splice into for the MAP clamp to make sure everything there is good. If that checks out then I'll order the BCS and see if that changes anything. If that doesn't work I'll have to get more fuel pump internals and try that. If that doesn't work I'm f'd.

 

[Sport6]

1100 is still pretty low for the fuel pump. Shouldnt dip below 1400, 1500 really.

It seems your car is going into limp mode.

 

[AutoEuphoria]

So the consensus is that it is the fuel pump internals?

 

[8.5MS3]

i would check the wiring first. are you getting any CEL's?

 

[AutoEuphoria]

Nope, I have not had a single CEL during this whole time.

 

[8.5MS3]

weird......i'd have to say the pump then. check the computer for active dtc's anyway. sometimes a code must be thrown several times before the dash lights up. I had a p0234 overboost code but it didnt show up as a CEL. the misfire code is the same as well. it requires 3 events to light up. but they will show up in a scan.

 

[AutoEuphoria]

Will do. I wouldn't doubt if it were the fuel pump. I was unlucky and installed via the walkthrough posted in the How-To section BEFORE the "don't use gas to lube the parts" revelation came about.

 

[opt_ms3]

from my experience, any more than 1/4 throttle and the fuel pressure should not go below about 1500psi regardless if you are building boost or not.

 

[AutoEuphoria]

I am leaning more and more towards the fuel pump. Rechecked all of the electrical wires..all looked good. Fuel pump is clicking much louder than it ever has. Fuel pressure around 350-400 at idle now. Going to order a new set of internals asap...and drive it like a grandpa until then.

 

[matsuda]

Regarding the WG numbers from your graph:

WG is referring to the duty cycle of the electrical signal to the wastegate control solenoid (valve). 0% = closed (minimum boost) and 100% = wide open (maximum boost).

The WG duty cycle will normally be high when the actual boost pressure < target boost pressure (e.g. during spool-up). If it's at or near 0%, the ECU wants to minimize boost pressure (~10 PSI in a stock MS3).

The ECU has no feedback as to the opening of the actual (mechanical) wastegate.

 

[AutoEuphoria]

Thank you for that information

I guess I'm at the point where I need some advice for the best next step forward. Considering my budget is a little tight right now, should I opt to try the BCS first ($60) or just wait a few weeks and do the fuel pump first ($260)

I just wanted to also lay this out, in case it helps anyone who might be able (and willing) to help:

Before:
- MAP clamp installed
- Boost controller installed
- Boost control solenoid taken out of system (front nippled capped, rear nipple still connected to intake)
- Fuel pressures normal
- AFR was rich (especially at full boost, due to MAP clamp)
- Spooled normally (no extra lag)
- Held boost at or around target with little issue

After:
- MAP clamp removed
- Boost controller removed
- Boost control solenoid connected to system (front nipple to top of wastegate, rear nipple to intake)
- Fuel pressure dropping far below it has ever been (spiking to around 1600 then dropping to ~300)
- Boost spikes to 15-16, then drops rapidly to 0-1
- AFR is normal (11ish)
- Spools normally (no extra lag noticed)