Stock BPV - How typical is it for leaking?

[phantom6294]

the thing that concerns me is that the WG DC isn't even making the attempt to get your boost up to where it needs to be. i'll try to dig up one of my logs with the stock map, but this looks a lot like your WG isn't even attempting to open as much as it should.

Wouldn't the waste gate need to close in order to increase boost? Closing the waste gate forces more air over/through the exhaust turbine (and hence spin faster and hence more boost) versus being diverted out the waste gate, no? Thus, a 0% WG DC means the waste gate is fully open (default position) and 100% WG DC means the waste gate is fully closed.

If you look at his log, the WG DC spikes up initially, closing the waste gate and helping to build boost, but as is common on stock cars, it creates too much (though in this specific case, the boost hits only about 15PSIg) and as such, the WG DC drops significantly and thus opens the waste gate to ensure the boost doesn't head to the moon. Then, the WG DC increases slightly to ensure the boost is maintained. As the RPM increases, and exhaust flow increase, less WG DC is needed (and thus the waste gate doesn't need to be as closed) to maintain the same boost level and the WG DC works it way down.

 

[Sacrilicious]

it's the other way around, actually. WG DC 100% = exhaust gases 100% dumped into the turbo. the higher duty cycle, the more boost is generated. that initial spike you see is what the ECU uses to kick start the spooling on the turbo.

here's a log of a v103 beta map that i took:

 

[MS3 GT]

i found out my boost is leaking when reaching higher mphs.. so that mean eighter my vacuum is leaking or clamps isnt tight enough..??

 

[phantom6294]

it's the other way around, actually. WG DC 100% = exhaust gases 100% dumped into the turbo. the higher duty cycle, the more boost is generated. that initial spike you see is what the ECU uses to kick start the spooling on the turbo.

Um... that's what I said. The waste gate has to be closed to send the exhaust gases to the exhaust turbine.... 100% WG DC = waste gate fully closed. You originally said you found it odd the OP's waste gate wasn't opening as much as it should. An open waste gate means low(er) boost.

 

[Sacrilicious]

Um... that's what I said. The waste gate has to be closed to send the exhaust gases to the exhaust turbine.... 100% WG DC = waste gate fully closed. You originally said you found it odd the OP's waste gate wasn't opening as much as it should. An open waste gate means low(er) boost.

whoops...i keep forgetting it's reversed when referring to WG position and that "open" means it's dumping to exhaust. regardless, the WG DC should be higher at the upper rpms than his graph is showing. now, my car is obviously boosting more than stock in that map (16-18 psi), but the fact that his WG DC just falls flat on its face makes me wonder what is up.

 

[Sacrilicious]

i found out my boost is leaking when reaching higher mphs.. so that mean eighter my vacuum is leaking or clamps isnt tight enough..??

how high is "higher mphs"? the reason i ask is that it just doesn't quite make sense. are you trying to say that you think you're leaking at high boost and high rpm? how do you know you're leaking? do you have low boost? can we see a log or get a detailed description of what happens?

 

[phantom6294]

whoops...i keep forgetting it's reversed when referring to WG position and that "open" means it's dumping to exhaust. regardless, the WG DC should be higher at the upper rpms than his graph is showing. now, my car is obviously boosting more than stock in that map (16-18 psi), but the fact that his WG DC just falls flat on its face makes me wonder what is up.

Okay... I started questioning myself... lol

Well, my stock car does the same thing in this cold weather; boost definitely isn't getting/holding 15-16 PSI. I've tightened three of the four clamps post turbo (I can't quite get to the last one just before the throttle body) to no avail. I had a Forge BPV on for a while in case it was the stock BPV was leaking to no avail. It seems the colder it is, the less boost my car wants to make. I just continue to wonder if the ECU is lowering its boost target for extremely cold temps to reduce cylinder pressures???

I may head out later to run some errands and will do some boost logs to compare with the OP. Ambient temps are about 30F right now.

 

[Sacrilicious]

Okay... I started questioning myself... lol

Well, my stock car does the same thing in this cold weather; boost definitely isn't getting/holding 15-16 PSI. I've tightened three of the four clamps post turbo (I can't quite get to the last one just before the throttle body) to no avail. I had a Forge BPV on for a while in case it was the stock BPV was leaking to no avail. It seems the colder it is, the less boost my car wants to make. I just continue to wonder if the ECU is lowering its boost target for extremely cold temps to reduce cylinder pressures???

I may head out later to run some errands and will do some boost logs to compare with the OP. Ambient temps are about 30F right now.

lol...ya, don't mind me...i just had my head going in too many directions at the time and just didn't stop to word things right. how much boost are you making these days? i drove a whole winter last year with just a cobb sri, and i was making roughly the same boost throughout the winter...MAYBE 1psi short of the stock boost? what you say makes sense, though. i'm pretty damn sure the cooling efficiency of our IC system is a lot better with the ice cold air out. better cooling efficiency = bigger pressure drop across the IC core, which would account for lower boost levels. our car is load tuned, so it would not necessarily hyperventilate if our achieved boost level was 1-2 psi less than normal.

 

[Trader]

good, so you ltft's (long term fuel trims) should be close to zero if there is no leak. If you do have a leak your ltft's will be positive numbers indicating the ecu is adding fuel to compensate for the unmetered air that is getting somewhere. Check your intercooler hoses and anything that is after the turbo.

LTFT

My LTFT's are usually about the following:

Idle = -1 to -3
Low RPM/low load = -1 to -3
Partial throttle = 0
WOT = 0

WGDC

The WGDC is confusing because a closed wastegate solenoid valve means an open wastegate (if and only if) boost is above the mechanical boost pressure of the wastegate actuator. On my old DSM it was about 10 psig. Dont know what it is on these MS3's?

So the solenoid is just a bleeder type valve that relieves pressure from the wastegate actuator keeping you under boost. So you should build boost to at least the actuator threshold (assume 10psi) then after that the solenoid valve has some meaning.... At that point the higher duty cycles correspond to more bleeding away of pressure from the actuator giving you boost.

Actual pedal position vs. Absolute throttle position sensor

Another thing I noticed is that I am at WOT (actual pedal position at 100%) while the Absolute throttle position sensor is registering 35% to 55%?

I have read that the ECU will adjust the "drive by wire" throttle. But doesn't this seem a bit much??

My thoughts

I am thinking that for some reason the ECU is doing this and it is probably not a leak. Still going to check for leaks though. I have read of some other threads about people getting lower boost when it is cold out. I am not seeing any WOT KR so the ecu is not adjusting due to that.

The problem is that there are not a lot of stock dashhawk logs out there to compare to. Most people seem to start logging after they have started modding. I got the DashHawk first on this car to understand how the ecu is working before I started modding, that way I can understand the effect of each mod.

I have not been able to do any more logs lately because of the snow here, but it is going to get a little warmer here in the next few days. I will do a comparison log to see if anything changes.

If nothing changes I may try resetting the ecu as well.

 

[phantom6294]

LTFT

My LTFT's are usually about the following:

Idle = -1 to -3
Low RPM/low load = -1 to -3
Partial throttle = 0
WOT = 0

Those look great to me. About what I see on my stock MS3 (okay, I do have an AWR 88d rear mount... but that has NOTHING to do with boost).

Actual pedal position vs. Absolute throttle position sensor

Another thing I noticed is that I am at WOT (actual pedal position at 100%) while the Absolute throttle position sensor is registering 35% to 55%?

I have read that the ECU will adjust the "drive by wire" throttle. But doesn't this seem a bit much??

This is normal. The ECU will allow the throttle to be fully or near fully open upon initial boost generation, but after that... it's rarely open much more than halfway. There's a lot of discussion about this.

The problem is that there are not a lot of stock dashhawk logs out there to compare to. Most people seem to start logging after they have started modding. I got the DashHawk first on this car to understand how the ecu is working before I started modding, that way I can understand the effect of each mod.

Ask... and ye shall receive. I went out and did some boosted runs to get some logs. As I said, my car is stock (except the mount). Here are some logs -- I am HAPPY to take screenshots at higher res, but figured I would keep the res down -- hopefully the logs are still legible.

4th Gear:

5th Gear #1:

5th Gear #2:

I realize that the higher gears don't go into higher RPM... but you'll understand I would prefer NOT to post logs showing my RPM and what gear, thereby admitting to insane speeds. I may... I may not have some logs with higher RPM runs and those logs, which may or may not exist, might show the boost continues to go down.

Also, realize that the TPS and WG DC are graphed against the same scale -- so, to get the reading for WG DC, look at the light purple numbers.

So, analysis? The fourth gear run shows an initial spike of ~16 PSIg and then it quickly falls off and by 4k RPM boost is below 13 PSIg. By ~4500 RPM, boost is ~12 PSIg and continue to fall.

First 5th gear run initially spikes to ~17 PSIg then quickly tapers and holds for just a moment at ~15.6 PSIg. After 3200 RPM the boost drops to ~13-14 PSIg range. The second 5th gear run is nearly identical.

Finally, 6th gear run initially looks great... however, notice I start the run at 2500RPM (whereas the rest started at 3000RPM) which is normally more load than I like to put on the engine... but I do this for science. At such a low RPM, the boost is maintained about 15.6 PSIg until about 3300RPM and then its downhill from there.

I would think... that if I had a significant boost leak, and the ECU were targeting a higher boost, the WG DC would be bouncing around and the boost would be bouncing around at the ECU tries to maintain that boost (e.g. 15.6 PSIg)

 

[Sacrilicious]

well, looks like you two are running roughly the same. looks like the car has severely detuned itself for the winter...=d

 

[Trader]

Yea that 4th gear log looks very similar response to my first log in 4th gear.

Both boost and AFR.

I will try some 5th gear logs as well soon.

 

[dread]

Wow no wonder my car always drove like s*** in the winter. As far as you rel. throttle goes the max number is 74. You guys need to get tuned. It looks like the ecu is not allowing the throttle to open which is preventing boost from building.

 

[motomike239]

well after following this thread i can relate to the same problem, i installed my cpe-nano and now my car drives totally different as in its not nearly as responsive as before without the intake, i dont have a DH but it does seem like it doesnt hold boost for crap now