Actual boost not meeting requested boost... Airbox restriction? Logs Inside.

[erykv1]

Hey guys,

I finally got rid of my open element hot air intake in lieu of a stock airbox -> 85mm MAF -> cts turbo rs4 elbow setup, which solved a ton of MAF issues / codes.

During the initial log on stock timing maps / safe boost PID... this was the fueling result:



After a revised tune and another log (might not be long enough, ran out of room), it seems like there is a larger discrepancy between the requested and actual:



Could the stock airbox be a point of restriction causing the requested boost to not be met? I pressure tested the car and there were not any leaks on the initial log. I don't think there was any heat soak either as this was not back to back pulls. Do I need to drill holes in the airbox to allow less pressure drop? WGDC seems to be OK as well.

If anyone is interested in taking a peek here are the logs:
Initial: https://drive.google.com/open?id=0B6...DVLNzQwWWcwd2s
Revised: https://drive.google.com/open?id=0B6...mh3VFdieW51UE0

Thanks!

[millerchris85]

The airbox is not likely to be the issue. As far as I understand it flows plenty for K04 cars.


Sent from my iPhone using Tapatalk

[rguil]

What is your waistgate duty cycle at? have you determined what boost pressure you can get with the n75 unplugged or just the signal lines attached to your wastegates directly?
have you determined that your k04s waistgates open at a proper psi and that they do not get blown open at higher levels? happened to my k24s...
You could also bypass your n249 and route your bypass valves directly to a vacuum source. At one point one of those lines from the n249 was kinked on my car causing my diverter valves to constantly stay oepn, boost requested didnt meet boost actual just like yours.
What kind of g/s do you see on your maf at WOT?

Checked for boost leaks i assume?
With boost requested not meeting boost actual by so much, i am suprised your b5 dosent go into limp mode.
Also, 28 psi is a lot to request for out of k04s. They turn into hair dryers at that psi, why dont you try something more conservative like 22psi?

[erykv1]

wastegates have both been set to 12psi cracking pressures as per SRM's reccomendations for their early k24 rs6 hybrids.
signal lines directly attached to wastegates will make what seems like 12-13 psi.

WGDC intiial log:


WGDC revised log:

[chris120391]

Airbox was a huge restriction in my k24 set up. Was having the similar issues until I removed the airbox and ran a cone filter. I also did have a separate wastegate issue until it was tightened... A lot. I'd start with seeing if it makes a difference with a different intake setup. If no difference then get to the wastegates.


Sent from my iPhone using Audizine mobile app

[vavJETTAw36]

Eric, I'd try unsnapping the stock airbox and separate it a bit to see what would happen. I was under the impression that cutting holes (darintake) was the normal for stage 3 and above cars.

I know flyboy has done the test on this. Check out that post on his website.

Sent from my iPhone using Tapatalk

[erykv1]

Airbox was a huge restriction in my k24 set up. Was having the similar issues until I removed the airbox and ran a cone filter. I also did have a separate wastegate issue until it was tightened... A lot. I'd start with seeing if it makes a difference with a different intake setup. If no difference then get to the wastegates.


Sent from my iPhone using Audizine mobile app

I just got rid of an intake to fix my MAF issues, I would hate to have to go back lol.

Eric, I'd try unsnapping the stock airbox and separate it a bit to see what would happen. I was under the impression that cutting holes (darintake) was the normal for stage 3 and above cars.

I know flyboy has done the test on this. Check out that post on his website.

Sent from my iPhone using Tapatalk

Yeah I saw flyboys pressure drop test but I'm not sure how it translates into the whole requested vs actual boost side of things

I didnt modify the airbox when I dropped it in because I was skeptical if it was even going to fix my issue, but now that it has... I guess drilling a few holes into it wouldnt hurt, lol.

[chris120391]

Looking closer at your logs I honestly think it's going to be a wastegate issue similar to mine. I know 2 other people that had the same turbos that did what i did to my wastegates and it fixed their issues. You'll just have to fine tune the wastegate tension once you have it boosting properly. Although stock air box will still be somewhat of a restriction, based on my experiences.

How was the old intake throwing off your maf? As long as you have at least 6inches before the maf you should be fine.

Sent from my iPhone using Audizine mobile app

[vavJETTAw36]

Shouldn't hurt anything. You could always fill the holes with the pieces you are cutting out if you need to (if you cut them well).

Well the relationship is simple. The turbo is merely a feedback loop: engine builds exhaust pressure, exhaust pressure builds charge pressure. Repeat. If the box is choking the engine, it's unable to feed the engine to feed the exhaust pressure to charge the engine.


Sent from my iPhone using Tapatalk

[erykv1]

Looking closer at your logs I honestly think it's going to be a wastegate issue similar to mine. I know 2 other people that had the same turbos that did what i did to my wastegates and it fixed their issues. You'll just have to fine tune the wastegate tension once you have it boosting properly. Although stock air box will still be somewhat of a restriction, based on my experiences.

How was the old intake throwing off your maf? As long as you have at least 6inches before the maf you should be fine.

Sent from my iPhone using Audizine mobile app

What exactly did you do to your wastegates? Set a different cracking pressure? My old intake must have been getting turbulent flow somehow in the tract as it was throwing my MAF readings all over the place. Replaced the unit with my current setup and all the symptoms went away.

Shouldn't hurt anything. You could always fill the holes with the pieces you are cutting out if you need to (if you cut them well).

Well the relationship is simple. The turbo is merely a feedback loop: engine builds exhaust pressure, exhaust pressure builds charge pressure. Repeat. If the box is choking the engine, it's unable to feed the engine to feed the exhaust pressure to charge the engine.

Sent from my iPhone using Tapatalk

Makes sense... I may drill a buncha tiny holes instead of a few big ones... I'll see what the tuner thinks about the logs first.

[chris120391]

Yeah basically, a lot of preload on the wastegate fixed it. I know I know it shouldn't be done that way but that is the ONLY thing that fixed it.

My intake is a cone filter to a 8 inch pvc pipe coupled to the maf then elbow. Works fine for me.


Sent from my iPhone using Audizine mobile app

[CJ_]

What exactly did you do to your wastegates? Set a different cracking pressure? My old intake must have been getting turbulent flow somehow in the tract as it was throwing my MAF readings all over the place. Replaced the unit with my current setup and all the symptoms went away.

Turbulent MAF readings like this by chance?

[MacDaddy]

From what i understand requested will always be higher than actual because of the intercoolers, by about 2psi

[erykv1]

Yeah basically, a lot of preload on the wastegate fixed it. I know I know it shouldn't be done that way but that is the ONLY thing that fixed it.

My intake is a cone filter to a 8 inch pvc pipe coupled to the maf then elbow. Works fine for me.


Sent from my iPhone using Audizine mobile app

I'll check into both of those. I'll probably start with the airbox since its easier to get to. Thanks for your input.

Turbulent MAF readings like this by chance?

Worse than that. The MAF was maxed out at 14-15 psi, cutting out a lot of tunable range. Fuel trims were also crazy.

[FlyboyS4]

Makes sense... I may drill a buncha tiny holes instead of a few big ones...

The larger holes are better than lots of small ones.

[erykv1]

The larger holes are better than lots of small ones.

I'm more concerned with getting the filter wet if I hit a large puddle or something... perhaps I could mold a flap or something along those lines to make an offset wall.

[christianb5s4]

I don't understand how some people have issues with the stock RS4 airbox being restrictive when many 600whp+ B5 S4s have been running that airbox with no issues or finding it as an impediment at that power level for a long time. I mean, the Hannover S4 is still running the stock RS4 airbox (albeit lightly modified) for crying out loud.

[FlyboyS4]

I don't understand how some people have issues with the stock RS4 airbox being restrictive when many 600whp+ B5 S4s have been running that airbox with no issues or finding it as an impediment at that power level for a long time. I mean, the Hannover S4 is still running the stock RS4 airbox (albeit lightly modified) for crying out loud.

OP has an S4 airbox, I've not seen the RS4 airbox being mentioned.

[CJ_]

Just looked at your logs, Is your wideband logging correctly? 10.75 seems rich, right? And how come you have no ignition retard?

[christianb5s4]

OP has an S4 airbox, I've not seen the RS4 airbox being mentioned.

Ah, good point. If it's an S4 box, it could very well be a restriction issue.

[erykv1]

OP has an S4 airbox, I've not seen the RS4 airbox being mentioned.

This is correct. Currently on the stock S4 airbox. Didn't want to spend the $ on the RS4 if I wasnt 100% sure my fueling issue would be fixed.

Just looked at your logs, Is your wideband logging correctly? 10.75 seems rich, right? And how come you have no ignition retard?

Yes, I am only on my first revision. It gets rich under WOT, is this it not the norm for our vehicles? During regular driving it maintained 14.5-14.9 which I believe is where it should be.

[Wagonholic]

Ah, good point. If it's an S4 box, it could very well be a restriction issue.

Doesn't the darintake mod essentially convert the S4 airbox into the RS4 airbox? Or make it close enough lol?

[slowSfaux]

Doesn't the darintake mod essentially convert the S4 airbox into the RS4 airbox? Or make it close enough lol?

Yep, and pulling fenders converts them to rs4 as well.

[y3ti]

Doesn't the darintake mod essentially convert the S4 airbox into the RS4 airbox? Or make it close enough lol?

Darintake mod allows more air before the filter, but that's not the problem. The restriction is the housing exit going into the MAF housing. Essentially bottlenecking the rest of the intake.

The RS4 housing has a larger exit going into the MAF housing, along with the larger MAF housing.

[erykv1]

Doesn't the darintake mod essentially convert the S4 airbox into the RS4 airbox? Or make it close enough lol?

Darintake mod allows more air before the filter, but that's not the problem. The restriction is the housing exit going into the MAF housing. Essentially bottlenecking the rest of the intake.

The RS4 housing has a larger exit going into the MAF housing, along with the larger MAF housing.

The rs4 housing (maf connection side) I believe is 93mm whereas the stock airbox is 78mm.

Approx 18% larger. However I believe the main purpose of the hole drilling originated from the accordion hose collapsing on some stage 3 cars due to the higher volume of air the engine pulls.

[Zba]

With the proliferation of 3D printing someone should mock up a larger outlet for the airbox that can be plasti-welded in. Get rid of the adapter on billet MAFs too.

Of course only if there is horse powers to be found

[FlyboyS4]

Darintake mod allows more air before the filter, but that's not the problem.

How did you reach this conclusion?

[y3ti]

How did you reach this conclusion?

Your flow tests.

They show that the RS4 housing and MAF flow more. Since the S4 and RS4 housings both use a panel filter, I assume we can rule the filter out of the equation.

What's left in the housing after the filter?

The MAF opening.

[Tjtalan]

Is the boost verified low on the gauge? What map sensor are you running, could you be maxing out the stock one.


Edit... I was told by Daz, RIP, the stock one was only good to 22psi.

[FlyboyS4]

Your flow tests.

They show that the RS4 housing and MAF flow more. Since the S4 and RS4 housings both use a panel filter, I assume we can rule the filter out of the equation.

What's left in the housing after the filter?

The MAF opening.

I don't know where you are looking, but when I flow tested a stock airbox with EPL MAF, versus the RS4 MAF and RS4 airbox the stock airbox/EPL MAF combination flowed greater.

But I was referring to your statement that the problem addressed by the Darintake is not the real problem.

[erykv1]

Is the boost verified low on the gauge? What map sensor are you running, could you be maxing out the stock one.


Edit... I was told by Daz, RIP, the stock one was only good to 22psi.

I'm running a 3 bar map sensor, tuned on the a 5120 file.

[y3ti]

I don't know where you are looking, but when I flow tested a stock airbox with EPL MAF, versus the RS4 MAF and RS4 airbox the stock airbox/EPL MAF combination flowed greater.

But I was referring to your statement that the problem addressed by the Darintake is not the real problem.

Well, you left out this part.

"The most likely reason for the EPL MAF having the greatest air flow is presence of the screen on the RS4 MAF causing restriction that the EPL MAF does not have." -Flyboy

By problem, I meant the problem the S4 housing has when trying to compare it to an RS4 housing .

My answer to him is basically an S4 housing can't be made into an RS4 housing by simply doing the darintake mod. The RS4 housing flows more because of the larger MAF opening. Do you not agree?

[rguil]

ignore your air box OP, its fine
Here is a post i made in regards to the crappy wastegate design that k24s have. Most notably post 24
http://www.audizine.com/forum/showth...t-properly-set

seems a lot of people including myself had to tension the shit out of our waistgates to get the turbos to function properly. Perhaps it is your problem too

[erykv1]

ignore your air box OP, its fine
Here is a post i made in regards to the crappy wastegate design that k24s have. Most notably post 24
http://www.audizine.com/forum/showth...t-properly-set

seems a lot of people including myself had to tension the shit out of our waistgates to get the turbos to function properly. Perhaps it is your problem too

was there a certain cracking pressure you set yours to? I just set both of mine to 12 psi on monday as recommended by SRM. I have their early versions of the k24s.

[Corradovolksb]

I set my k24's to 15psi cracking pressure and with the n75 unplugged I max out at 16psi on my logs and gauge. I don't have any issue hitting 26-28psi but I do have the new style turbos if it matters.

[erykv1]

isnt the general rule of thumb to preload wastegates to about 1/2 of what the max boost pressure should be? if thats the case I may be off 1-2 psi.

[Corradovolksb]

Yah that could be on some turbos. On k03s they are set to 5psi and they can spike 20-21 so I guess it depends on the turbo.

[FlyboyS4]

Well, you left out this part.

"The most likely reason for the EPL MAF having the greatest air flow is presence of the screen on the RS4 MAF causing restriction that the EPL MAF does not have." -Flyboy

So remove the flow straightener from the RS4 MAF?

By problem, I meant the problem the S4 housing has when trying to compare it to an RS4 housing .

My answer to him is basically an S4 housing can't be made into an RS4 housing by simply doing the darintake mod. The RS4 housing flows more because of the larger MAF opening. Do you not agree?

Yes, I agree with you on this point.

It's worth adding that the ID of the entry of the RS4 MAF housing is 83mm and the EPL MAF is 79mm, so you gain 5% in cross section.

Another thing, the total area of the stock y-pipe outlets is almost 13% less area than the S4 airbox outlet, that would elevate the y-pipe to being the greater system bottleneck versus the airbox.

[V1nny]

With the proliferation of 3D printing someone should mock up a larger outlet for the airbox that can be plasti-welded in. Get rid of the adapter on billet MAFs too.

Of course only if there is horse powers to be found

No need for such complicated solution. Simply trim plastic latches on the outside of the outlet, remove o-ring on the inside, and clamp 3.75" hose adapter to the MAF housing.

[y3ti]

So remove the flow straightener from the RS4 MAF?

...that would elevate the y-pipe to being the greater system bottleneck versus the airbox.

Yes, you suggested in your flow test conclusion that removing the flow straightener from the RS4 MAF might increase the flow over the EPL MAF.

As far as the y-pipe bottleneck goes, that's actually something I wasn't aware of. I'll have to look into your work on that.