2008 speed3 Low Boost (6-9 psi all gears)

[aeonpsych]

So I had another thread mainly focused on why the car was stalling at idle when the A/C would shut off. I fixed that due to a faulty and poorly secured intake filter with an airbox delete. I linked into the low boost issue thinking it could be relevant to the stalling, like maybe something mechanically or electrically was the cause of both issues, since that was not the case, I still need to figure out what the issue is with low boost...


Short backstory/information: I was able to get up to 12 psi earlier this year, but it has degraded down to 6-9 in all gears, recently). Only relevant mods to the motor that I know of are intake air box delete, 2nd cat delete with straight pipe from the 1st cat back. I've pulled entire sri, and intercooler off at least 3 times to check for damage or leaks in the lines. Checked the vac box under the intake as well. Cleaned MAF at least 4 times with maf cleaner, and spark plugs were brand new ngkix11 gapped to 25 7,000 miles ago, during the whole time of which I have had low boost issues.


I had the ebcs vac to wg disconnected to test the wg. I was able to get up to 15 ish psi (5+ gear) before boost cut, and a spike of 20psi. I am only able to get around 10-12 in 1st-4th gear before getting cut. This led me to believe the ebcs was bad, so I replaced it just the other day.. I checked the SRI piping throughout and all vac lines connected to it while I had it off replacing the ebcs, and even the small lines going to the ebcs are not clogged. I don't think there is an issue with the vac lines to the ebcs either, as they are indeed operating the wg by function of the ebcs. Just apparently operating the wg too much, too soon, too often. Without the vac from bcs to wg, I get boost cut in 1-3 gear at around 10 psi. 4 gear is around 12 psi, 5 and 6, I can creep up to 15 if I ease into it with the throttle. If I drive around with the line disconnected, the car drives good in all gears, watching the psi, and shifting before it cuts, if I want to do "pulls". I'm not planning on doing this, though, as I mainly just drive around like a grandma. The 27 avg mpg city with A/C on I've been getting is too good to give up atm lol.

I've done 2 datalogs with torque pro in 3rd gear. the first one is a street pull, the second is highway on ramp pull. Maybe someone can help, that understands the logs for this car. The logs are with the new EBCS installed, and both vac lines properly routed to/from it.

If one of the threads needs to be deleted or closed, I can do so. Just kindly let me know.

[MSMS3]

What exactly do you mean by "airbox delete"? That's a strange term on this forum. Many of us remove the stock airbox and replace it with either a cold air intake system or a short ram intake. From your post you have some sort of SRI. Please describe in detail what it is. Is it from a particular company, or separate components from different sources. What is the tube diameter? Are you using the stock MAF housing and stock MAF, or something else?

Changes in intake on this car can cause quite a few problems unless you replicate the air mass flow across the MAF sensor to be the same as the ECU is expecting. Otherwise, your MAF is sending the wrong signal to the ECU and that affects fueling, AFR, timing, everything.

Are you on stock tune? If you are running an aftermarket tune, you need to do a MAF calibration to scale the MAF so that it sends a signal to the ECU that is consistent with your tune. Changes in intake tube diameter from stock, changes in the size or shape of the MAF housing, itself, and the presence or absence of an air straighter insert in the MAF housing just ahead of the MAF if you have an aftermarket intake can all make a huge difference in how you run.

But, only generating 6-9 psi points to a second problem. You may be running on spring pressure only with no increase in boost from your ECU commanding higher boost. That could be due to many things. One might be that you routed the houses from the turbo to the EBCS and EBCS back to your pre-turbo intake.

Another could be a huge boost leak somewhere.

I think you are chasing multiple problems.

Let's begin with sorting out what type of intake you are actually running and whether it is compatible with whatever tune you have.

As the the logs, it looks like your waste gate is damn near maxing out, almost at 90% at only 7 psi of boost or less. That stands out. The ECU wants to build more boost. It is telling the wastegate to let that happen, but boost is not rising. You say you've verified there are no leaks on the intake side all the way to the throttle body. Did you do a full boost leak test? If so and there are no problems on the compressor side, I wonder if either the turbo is failing or if you have a downstream restriction in the exhaust, such as a clogged primary cat. I know you have a race pipe behind that.

[aeonpsych]

air box delete is referring to the stock box covering the filter. The rest of the intake is OEM stock. The oem housing that holds the maf and filter is still intact.

I have ran with the ebcs vac to wg line disconnected and peaked at 20 psi in 4th gear, before boost cut. I can ease the throttle and hold about 12-14 in 1-3 gear like this before getting cut, so don't think it is a boost leak related issue. I do not believe the turbo is failing either, as it hits boost good and hard with the ebcs vac to wg disconnected, up until boost cut. Also checked for spinning and shaft play while intake was off replacing the ebcs the other day.

I have not done a leak down or boost leak test. Planning on piecing one together as soon as I have time.

If I had exh restrictions, I shouldn't be able to hit 18 psi with the vac disconnected, right? It was mentioned in the other post on here that it's possible the electrical signal to the ebcs is bad.

[Fstrnyou]

Even with no signal to the ECBS, you should be able to hit 10-12 psi.

[aeonpsych]

This is the first electrically controlled boost car, I've had, first by gear as well, but that's what I was assuming.

So I do know that without the bcs vac to wg connected, I do get over 10 psi fairly easily.
, but engine stumbles bad around 12 psi 1-3rd, and around 14 4th. 5th I can get to spike to 18 before it cuts back to around 15 and stumbles.


If I slowly keep easing on the throttle while it is stumbling, I will get an overboost cel, and cyl 4 misfire detection. This can occur even before 15 psi.

So I'm wondering then if the stars aligned and I really did get a DOA new bcs. Only other thing I can really think of is that previous owner got a super safe tune to 8 psi all gears and lied to me about it (but why). Then I have to wonder why I was able to hit around 12 earlier this year. I've only had a boost gauge and/or datalog app this year, and have had the car since over a year ago, so really don't know where it was at before.

[Fstrnyou]

Stock wastegate spring pressure is around 10psi. At least that's what my K04 did. It can vary slightly from car to car. The fact is, at WOT, it should never be less than wastegate pressure (assuming you're in an RPM range to allow spool-up). There is no logical way to run lower boost at WOT without doing some wacky things in the tune (ie: throttle control), restricting the intake or exhaust flow, broken turbo, pre-turbo exhaust leak, or having some sort of decent sized boost leak.

[aeonpsych]

hmmmm, ok.

Well, let me just focus on one thing at a time. Why is it that with the bcs vac line to wg disconnected, I seem to get target/more than target boost psi, but with it connected, it's been struggles to build more than 8, any gear?

I honestly can't think of anything, and if I should be hitting wg spring pressure either way (let's say around 10ish), I really don't know why it's struggle bus at 7ish.
Again, just disconnecting that vac line and changing nothing else, it's a night/day difference, and easily hits over 10 psi.

[Thor Hammer]

Do you have an AP? What are your fuel trims? Reason for asking: potential boost leak. The trims being out of range positive or negative can indicate if the leak is pre or post turbo.

Personally I would be focusing on testing for leaks. Then go to the next troubleshooting step from there.

As for why the erratic boost when WG disconnected? Cant help you there. Seems straightforward enough from the explanation @Fstrnyou; gave.

[aeonpsych]

Cruising: Bank 1 LTFT is around -10%, bank 1 STFT usually bounces between -3% and 4%, mainly hovering around 0%.

WOT, the Trims seem to hover around 0% for the most part, and then LTFT snaps back to -9% after letting off the throttle, and then hovers around -10% while cruising. Can see most of this in the logs I posted.


The reason I'm asking about the boost being good with simply disconnecting the bcs is because that seems to rule out leaks, or clogs, or failing turbo. Seems like it's related to the bcs, but apparently all the bcs does is regulate boost above wg spring pressure. That's what the big stumper is for me. Sure, maybe I do have a leak, maybe the exhaust is clogged (my friend thinks it's this, because he thinks he can hear the cat honeycomb rattling around as if it's failed and broken up), but then why no restrictions by just simply disconnecting the bcs vac line? Point here is that if there's a clog, leak, or failed turbo, I shouldn't be seeing this much more boost by just disconnecting this vac line.


As for the AP/tuner, I'm working on that, as well as HPFP internals as the next purchases for this vehicle. I just want to make sure the car isn't actually broken already before I invest more money into mods. Also waiting for my other car to get up and running before I start seriously messing with this.

[MSMS3]

Originally Posted by aeonpsych air box delete is referring to the stock box covering the filter. The rest of the intake is OEM stock. The oem housing that holds the maf and filter is still intact. I have ran with the ebcs vac to wg line disconnected and peaked at 20 psi in 4th gear, before boost cut. I can ease the throttle and hold about 12-14 in 1-3 gear like this before getting cut, so don't think it is a boost leak related issue. I do not believe the turbo is failing either, as it hits boost good and hard with the ebcs vac to wg disconnected, up until boost cut. Also checked for spinning and shaft play while intake was off replacing the ebcs the other day. I have not done a leak down or boost leak test. Planning on piecing one together as soon as I have time. If I had exh restrictions, I shouldn't be able to hit 18 psi with the vac disconnected, right? It was mentioned in the other post on here that it's possible the electrical signal to the ebcs is bad.

Can you install a manual boost gauge, temporarily, at the bpv hose? That would verify your logged boost. The stock MAP sensor stops increasing voltage at 22.5 psi. If you bypassed the EBCS and saw 22 psi on your log, you may have gotten 30! Not safe to run that way without at least a manual controller in place.

Do the pressurized boost leak test. Verify accuracy of your MAP sensor and look for restriction on the exhaust side somewhere.

[aeonpsych]

I do have a gauge hooked up to the bpv hose. The numbers I'm going going off of are the numbers I read from this gauge, the torque data logs just back it up, and while monitoring with torque, I do see the same numbers maybe +-1psi difference.

Going to attempt and make my own boost test adapter this weekend. Should have time finally.
I just don't understand how either a boost leak or exhaust restriction is limiting boost to 7ish psi, but hardly limiting, if at all just with the vac line disconnected. Seems counterintuitive, but then again, I have seen stranger things.
Will try and check both of these out this weekend, and also plan to regap/recheck the spark plugs.

Any other suggestions while I would plan to have the car stationary for a bit?

[Solarsurge]

Dumb question, but are you 100% sure you don't have your EBCS hoses connected to the wrong nipples?

[Fstrnyou]

Even hooked up wrong, he still shouldn't underboost.

[aeonpsych]

Well, the tip vac line goes to the ebcs nipple that is farthest from the ebcs connector, and closest to the firewall. The ebcs vac line closest to the connector, going to the top of the wg.

I haven't been able to find a diagram without 3 ports coming up in searches, but from what I've seen, this is the right way to hose the stock ebcs.

My friend still Banks on a clogged primary cat (which seems like a pain to get to so I've been procrastinating checking it, and also I'm not willing to just simply delete it without hpfp internals), but what gets me is if it's so clogged, why then would I actually be able to get higher boost without the ebcs vac connected lol. If it's clogged, I'd feel like it would have symptoms of being clogged all the time. Same goes for boost leaks.

[Fstrnyou]

The tune for the EBCS isn't set up to compensate for clogged cats...if that's the problem. I haven't looked at the datalogs, but it's possible the ECU is working the EBCS as hard as it can within the limits of the tune. Removing the hose from the wastegate is like running 100% EBCS duty cycle...which the stock tune won't allow.

[aeonpsych]

If you are referring to wgdc in the datalog, it's around 85% at 7psi, 75% throttle position and engine load.

If I understand you correctly, then basically the tune either can't go 100%, or is "seeing" the restriction and not able to compensate by increasing wgdc, which means that it is extremely plausible to have an exhaust restriction (like clogged cat) in my case?

I'll see if I can get my friend that does some exhaust work to check it out. If it's the case, I'll probably just have him gut the cat (no emissions needed for me), and if it fixes the problem I'll probably just drive it safely like that and get the hpfp ordered asap.

[MSMS3]

Originally Posted by aeonpsych If you are referring to wgdc in the datalog, it's around 85% at 7psi, 75% throttle position and engine load. If I understand you correctly, then basically the tune either can't go 100%, or is "seeing" the restriction and not able to compensate by increasing wgdc, which means that it is extremely plausible to have an exhaust restriction (like clogged cat) in my case? I'll see if I can get my friend that does some exhaust work to check it out. If it's the case, I'll probably just have him gut the cat (no emissions needed for me), and if it fixes the problem I'll probably just drive it safely like that and get the hpfp ordered asap.

It does sound like you have a restriction in the primary cat. FWIW, I'm running a 3" catless dp and rp into stock CBE. Not only will you need an upgrade to the HPFP internals, but you will likely get very nasty boost spikes if you are on the stock tune. When you gut the cat would be the time for you to get a compatible tune to take advantage of the flow increase while taming the spikes. Also know that gutting the primary and running a racepipe or testpipe (which I appreciate to be the case) will make for a very loud exhaust with a lot of drone in the cabin when passing through the 2,500 rpm range or cruising at that rpm range. I had to weld a straight through reso (see my sig below) into the rp section to tame this headache inducing drone.

[aeonpsych]

Thanks for the advice. Yea, this might be a little ways off still, then, as I won't have enough spending cash for exhaust parts, hpfp, and a tuner in one go...

Had a friend help with brake replace and transmission flush last night. While that was happening, I went through and checked the spark plugs and maf sensor.
Cylinder 1 (closest to the passenger side) was completely black, and the other 3 looked real white. All were still gapped at 25/26. Put some clean ones back in and also re-cleaned the maf sensor.

Did another visual boost leak inspection, but we were not able to do a pressure check or to check out the exhaust like we planned. My friend had some stuff come up... He's the one with most the tools, and lots more knowledge than me on stuff like this... From visual inspection, he's narrowed down his suspect of the problem to a leaky bpv, or clog in the exhaust, or both. We were supposed to meet back upsometime this evening, but doesn't seem like thats the case anymore.

Lastly, after the work last night, went and did some test driving. Seems like I'm now back to were I was before earlier this year.
1st gear - spikes at 10psi, holds around 8
2nd holds around 10
3rd holds around 11
4th spikes at 14 and holds around 12.

Have not tested any other gears yet. Doesn't seem like it's still where it should be, but it is at least better than 7psi all gears.