Does cone filter size affect flow characteristics?

[erykv1]

Heyyoh B5S4 Gurus,

For those running non-oem intake box setups, have you guys noticed a difference in fuel trim readings based on a filter size change? I've been chasing maxed out MAF readings after 7k miles of my rebuild / reseal of my vehicle. I've exhausted every option aside from replacing the intake tract which has remained the same. I have my doubts that an intake tract can be causing these issues, but I haven't ruled that one out. There is no flow straightener in place, but I feel like the MAF is located a decent amount away from the end of the tube.

Since my knowledge on fluid flow is quite limited I hope there are some of you guys here that are experienced and can chime in. Will the larger filter size induce more turbulent flow in the intake tract? the MAF sensor location itself has physically not changed between the two setups.

I had limited knowledge before I started the tear down, so I cannot comment on how the fuel trims were before the work was done. I can however confirm that the current base file flashed to the ECU is scaled (MLHFM tables) appropriately for the MAF on the car.



Any input / personal experience with this? Should I source an OEM intake setup and plop a 85mm MAF housing in place? Would like to not keep blindly tossing $ at things if possible.

[NOTORIOUS VR]

Short answer. Yes it can.

MAF's are very sensitive to intake changes. So more or less flow, or more likely issues with airflow created by filters, obstructions, change of locations, etc, etc.

[erykv1]

Short answer. Yes it can.

MAF's are very sensitive to intake changes. So more or less flow, or more likely issues with airflow created by filters, obstructions, change of locations, etc, etc.

I wish the tune was the same as the previous setup so I could know for sure. I guess I can put the old air filter on it and see what happens. Thanks for your input!

[wbrunner23]

Consider adding a flow straightener - I ordered mine from SaxonPC



http://www.saxonpc.com/100mm-cells-for-100.html

[erykv1]

Consider adding a flow straightener - I ordered mine from SaxonPC



http://www.saxonpc.com/100mm-cells-for-100.html

Thanks for the link!

Do you have any better photos of how it attaches to existing piping?

[redline380]

I've never understood why hot air intakes are so popular

[erykv1]

I've never understood why hot air intakes are so popular

me neither. car came with no factory airbox, just trying to make do with what I got -.-

[redline380]

me neither. car came with no factory airbox, just trying to make do with what I got -.-

That is highly unfortunate. I'd keep an eye out for a used box. Actually, it just so happens the stock airbox is on limited quantity sale right now on ECS for $267. Definitely a thought. https://www.ecstuning.com/Audi-B5_S4--2.7T/ES2662108/

With that said, the general consensus is that a 6 inch straight section after the filter and before the MAF will clear things up, so yours appears to be OK. But that straightener listed above certainly won't hurt anything.

[Audi9]

I've watched them change trims on other platforms. Couldn't tell you about this one unfortunately but VR said it can so I'd go with that.

If you wanted to verify it try turning the filter/tube and then log it. I've seen just having the filter at a certain angle screw with trims as well

[NOTORIOUS VR]

I've watched them change trims on other platforms. Couldn't tell you about this one unfortunately but VR said it can so I'd go with that.

If you wanted to verify it try turning the filter/tube and then log it. I've seen just having the filter at a certain angle screw with trims as well

The issue isn't so much as the air flow/volume change, but rather how the air flow is acting in the pipe... different filters, different pipe lengths, etc will change the airs direction especially at low speeds/idle that air will be bouncing around...

There are maps in the ECU to correct for this situation.. but if you change something in front of (and to a point even after) the MAF all bets are off.

[dannyn424]

whats your maf size and boost at in psi?

[wbrunner23]

I just wedged it inbetween the maf housing and the 4" aluminum tubing to the air filter.

I also built a fiberglass heatshield and sealed it to the hood.

[erykv1]

I've watched them change trims on other platforms. Couldn't tell you about this one unfortunately but VR said it can so I'd go with that.

If you wanted to verify it try turning the filter/tube and then log it. I've seen just having the filter at a certain angle screw with trims as well

The issue isn't so much as the air flow/volume change, but rather how the air flow is acting in the pipe... different filters, different pipe lengths, etc will change the airs direction especially at low speeds/idle that air will be bouncing around...

There are maps in the ECU to correct for this situation.. but if you change something in front of (and to a point even after) the MAF all bets are off.

Whats weird is, at idle, the MAF readings are fine... but once I start building boost it goes crazy. MAF voltage is maxed out at 17-18 psi... symptoms of a much smaller intake tract / MAF diameter, yet everything is correct in the file. Its like chasing a ghost.

whats your maf size and boost at in psi?

89mm, cant accurately tell you boost as I've been babying this for months until I can solve this issue.

I just wedged it inbetween the maf housing and the 4" aluminum tubing to the air filter.

I also built a fiberglass heatshield and sealed it to the hood.

Thanks for the input I'll definitely keep it in mind!

[NOTORIOUS VR]

Whats weird is, at idle, the MAF readings are fine... but once I start building boost it goes crazy. MAF voltage is maxed out at 17-18 psi... symptoms of a much smaller intake tract / MAF diameter, yet everything is correct in the file. Its like chasing a ghost.

No intake leaks?

Post a set of full logs with ME7Logger

[erykv1]

no intake leaks. pressure tested a million times, replaced all the green check valves to rule out any internal leaks, checked with new dv's. new n75, new n249. wastegate lines checked out, cracking pressure checked out. you name it, i've checked it...
everything aside from replacing the intake tract.

here is a log: https://drive.google.com/open?id=0B6...kFEdzB4QnM4SlE

[NOTORIOUS VR]

no intake leaks. pressure tested a million times, replaced all the green check valves to rule out any internal leaks, checked with new dv's. new n75, new n249. wastegate lines checked out, cracking pressure checked out. you name it, i've checked it...
everything aside from replacing the intake tract.

here is a log: https://drive.google.com/open?id=0B6...kFEdzB4QnM4SlE

You have a boost leak. It's the only reasonable explanation, not sure how you are pressure testing, but whatever you're doing isn't working. It's either that or your MAF sensor is bad.

1. You're in limp mode - WGDC is fixed @ 10% because you're not meeting requested
2. You boost builds, then drops, holds than creeps to 18 psi by redline. Your MAF is obviously seeing the air being pulled in and accounting for it which will prove the boost leak in point 3.
3. You're running stupid rich - all signs point to a major boost leak, your MAF is metering for the air being consumed by the turbos but your motor isn't getting any of this air. You're running rich EVERYWHERE especially under boost.

[erykv1]

You have a boost leak. It's the only reasonable explanation, not sure how you are pressure testing, but whatever you're doing isn't working. It's either that or your MAF sensor is bad.

1. You're in limp mode - WGDC is fixed @ 10% because you're not meeting requested
2. You boost builds, then drops, holds than creeps to 18 psi by redline. Your MAF is obviously seeing the air being pulled in and accounting for it which will prove the boost leak in point 3.
3. You're running stupid rich - all signs point to a major boost leak, your MAF is metering for the air being consumed by the turbos but your motor isn't getting any of this air. You're running rich EVERYWHERE especially under boost.

I know everything points to a boost leak. I also know its near impossible to diagnose a car over the internet, but I am 99% sure there is no boost leak.

With the MAF unplugged the car fuel trims go back into spec and drives much better. I've purchased 4 OEM mafs to try to track this issue down and it doesnt change anything. I've been driving for the past 5k miles with the MAF unplugged and the car is not running rich as when it is plugged in.




This is the leak tester I've built and using. Has a shutoff valve and built in pressure gauge / regulator. Pancake valve is removed and the inlet is capped on the Y pipe when testing. As well as the oil cap loosened / removed to prevent crankcase pressure buildup.

The car is throwing a code for P1557 which immediately throws the car into limp (I guess I should have mentioned this). Heres an earlier thread that better outlines what I've tried to no avail if you're interested in looking into it: http://www.audizine.com/forum/showth...lock-032-p1557

I appreciate your help.

[NOTORIOUS VR]

Very odd...

Did you change the MAP sensor? Do you have a boost gauge? Does it correspond with what the ECU is seeing in terms of boost?

[erykv1]

Very odd...

Did you change the MAP sensor? Do you have a boost gauge? Does it correspond with what the ECU is seeing in terms of boost?

Yes, I'm running a 3 bar map as requested by the tuner. The boost gauge does correlate to the logs.

The only other thing I can think of is to test the resistance that go from the ecu side of the harness to the MAF plug to see if they're good. Never been stumped for so long by any car I've owned. I've also had a few Audi / Mercedes tech's look it over and they have no clue. I even went as far as to getting another ecu to see if it would fix it lol.

[redline380]

Is your MAF size properly scaled to the tune on the car? That is a plausible explanation.

[erykv1]

Is your MAF size properly scaled to the tune on the car? That is a plausible explanation.

When it comes to the tune itself, I have verified (and some other members have also looked at):

-Appropriate MAF scaling per housing diameter
-Correct KRKTE / TVUB values for the injectors
-MLOF is set to zero as per Hitachi MAF
-Correct definitions file was used

The only concern I have is that ps_w is over pvdk_w which indicates an overscaled MAF (possibly?)

Unless theres something grossly simple I'm overlooking, I've been stumped by this for the last 6k miles lol.

[redline380]

-Appropriate MAF scaling per housing diameter
-Correct KRKTE / TVUB values for the injectors
-MLOF is set to zero as per Hitachi MAF
-Correct definitions file was used

The only concern I have is that ps_w is over pvdk_w which indicates an overscaled MAF (possibly?)

This is all Greek to me since I am a hardware guy, not a software guy. Others can help you out with that but I would verify the tune you are running and check with tuner about appropriate MAF sensor to use, as well as housing diameter

[phila_dot]

You have a boost leak. It's the only reasonable explanation, not sure how you are pressure testing, but whatever you're doing isn't working. It's either that or your MAF sensor is bad.

1. You're in limp mode - WGDC is fixed @ 10% because you're not meeting requested
2. You boost builds, then drops, holds than creeps to 18 psi by redline. Your MAF is obviously seeing the air being pulled in and accounting for it which will prove the boost leak in point 3.
3. You're running stupid rich - all signs point to a major boost leak, your MAF is metering for the air being consumed by the turbos but your motor isn't getting any of this air. You're running rich EVERYWHERE especially under boost.

This leak would have to be massive.

When it comes to the tune itself, I have verified (and some other members have also looked at):

-Appropriate MAF scaling per housing diameter
-Correct KRKTE / TVUB values for the injectors
-MLOF is set to zero as per Hitachi MAF
-Correct definitions file was used

The only concern I have is that ps_w is over pvdk_w which indicates an overscaled MAF (possibly?)

Unless theres something grossly simple I'm overlooking, I've been stumped by this for the last 6k miles lol.

ps_w exceeds pvdk_w at 10% wgdc?

Any reason you can't swap stock intake/MAF and injectors in and see how it reacts on stock software?

[phila_dot]

I bet they screwed up the 5120

[erykv1]

This leak would have to be massive.



ps_w exceeds pvdk_w at 10% wgdc?

Any reason you can't swap stock intake/MAF and injectors in and see how it reacts on stock software?

Aside from the fact that I would have to source those, theres no reason why I cant. The car just never came with the stock airbox setup :(

I bet they screwed up the 5120

Any way to check on this? Or some brief instructions?

[NOTORIOUS VR]

It looks like that could be a Daz base tune - going by the req. AFR curve.

That said, did you buy the car like this (tune/fueling/map)?

[erykv1]

I bet they screwed up the 5120

It looks like that could be a Daz base tune - going by the req. AFR curve.

That said, did you buy the car like this (tune/fueling/map)?

You are correct on the Daz base tune. But I never got a chance to get revisions unfortunately as I spent months chasing a boost leak I don't have... Been in touch with Blake but due to this weird trim issue I've never gotten a chance to finalize on it. Just been dailying/babying the car with the MAF unplugged.

I did not buy the car like this. I purchased the car and had to do a ton of work. Was half ass stage 3'd when I got it.

[NOTORIOUS VR]

You are correct on the Daz base tune. But I never got a chance to get revisions unfortunately as I spent months chasing a boost leak I don't have... Been in touch with Blake but due to this weird trim issue I've never gotten a chance to finalize on it. Just been dailying/babying the car with the MAF unplugged.

I did not buy the car like this. I purchased the car and had to do a ton of work. Was half ass stage 3'd when I got it.

Interesting... I'm not sure DAZ's file would have issues with 5120 mod (in English that means the mod that allows us to use larger MAP sensors).

But there is certainly a big issue somewhere. I find it odd that you're seeing almost 4.7V on the MAF at barely 5600 RPM and 18 psi boost on what I'm guessing are PJK04 turbos? Just doesn't add up.

Any chance you can borrow a true 85mm MAF housing to test with?

[erykv1]

Interesting... I'm not sure DAZ's file would have issues with 5120 mod (in English that means the mod that allows us to use larger MAP sensors).

But there is certainly a big issue somewhere. I find it odd that you're seeing almost 4.7V on the MAF at barely 5600 RPM and 18 psi boost on what I'm guessing are PJK04 turbos? Just doesn't add up.

Any chance you can borrow a true 85mm MAF housing to test with?

Daz was no stranger to the srm k24 rs6s which is what I'm running. I can try an epl housing from my buddy but those housings taper to 78mm I believe.

Sent from my LGLS990 using Tapatalk

[NOTORIOUS VR]

Daz was no stranger to the srm k24 rs6s which is what I'm running. I can try an epl housing from my buddy but those housings taper to 78mm I believe.

Sent from my LGLS990 using Tapatalk

I agree he wasn't, but something is flat out wrong here and I still believe it's hardware and not software at this point.

I wouldn't use a housing like that... it would have to be a straight 85mm housing (like 034, etc) to match the SRM 85mm...

Just as a comparison, here is a log from a car I tuned on 85mm Hitachi, SRM K24 @ 23-24 ps (conservative spool).

notice that the MAF volts are only slightly higher than your car at 5600 (0.15V maybe) but you're running ~18psi there instead. Volt's are volts... it's not scaled so I still maintain something else is going on here. It looks like the turbos are drawing in the air, it's just not making it to your intake manifold.

[erykv1]

The intake currently on the car looks like this... something solomotorsports put together using an 034 hitachi bung (before they started making their own). There is a weld bead before the sensor but I'm not sure it can be inducing enough turbulence to cause my issues.



At first look, it seems like theres sufficient distance before the sensor, but I guess the only way I can be sure is to switch out the entire intake tract and see.

The car will hold 15psi during pressure test for a good 10-15 seconds before slowly bleeding down... I've checked literally every connection with a spray bottle and the only thing I found was a tiny tear in an injector o-ring which I have replaced. The last thing I did was replace the intake manifold gaskets and the o-rings on the spider hose quick connects for good measure... but the symptoms never went away.

I'm at a point where I feel like dropping it off at a shop but theres not really one I trust where I live lol.

[dannyn424]

check your tbb clamp the tbb may be lifting up at a higher boost level.... try ptesting to 20 psi....

[erykv1]

check your tbb clamp the tbb may be lifting up at a higher boost level.... try ptesting to 20 psi....

I have an APR bi-pipe, but I can try high pressures for the pressure test.

[Corradovolksb]

My vote is hardware as well. You said your tune is set up for 88mm Maf but your using an 85mm Maf? Or did I miss read that? I'm running an 85mm Maf at 26psi on k24s and my voltage at redline is around what yours is.

[NOTORIOUS VR]

I feel like the OP's post is (reading) deceiving as well... Can you confirm if your car was working fine or not before the filter change?

You say you did the fueling, but then you say you have limited knowledge about anything before the tear down? Did you upgrade your tune/fueling, etc before the tear down? Did you do the tear down/rebuild due to these issues?

Did you have these issues before the tune/fueling? What tune/fueling was on it before? I can see that the top pic is using a completely different MAP sensor, so I will assume the tune was different.

As for the MAF tube, I was assuming it was an SRM unit, but it's not as you say. Maybe the placement of the MAF bung is too close to the bend after the MAF causing issues. Really I don't think that is a great placement for the sensor.

You could try adding a 3-4 inches of straight pipe right after the MAF sensor to see if that helps (if you con't mind cutting up your intake/MAF pipe).

[erykv1]

This leak would have to be massive.



ps_w exceeds pvdk_w at 10% wgdc?

Any reason you can't swap stock intake/MAF and injectors in and see how it reacts on stock software?

I bet they screwed up the 5120

I feel like the OP's post is (reading) deceiving as well... Can you confirm if your car was working fine or not before the filter change?

You say you did the fueling, but then you say you have limited knowledge about anything before the tear down? Did you upgrade your tune/fueling, etc before the tear down? Did you do the tear down/rebuild due to these issues?

Did you have these issues before the tune/fueling? What tune/fueling was on it before? I can see that the top pic is using a completely different MAP sensor, so I will assume the tune was different.

As for the MAF tube, I was assuming it was an SRM unit, but it's not as you say. Maybe the placement of the MAF bung is too close to the bend after the MAF causing issues. Really I don't think that is a great placement for the sensor.

You could try adding a 3-4 inches of straight pipe right after the MAF sensor to see if that helps (if you con't mind cutting up your intake/MAF pipe).

Let me try to make things a little more clear without typing out a book, my apologies for making it confusing.

In short, the fueling...
Before: 044 fuel pump, bosch green giants, hitachi MAF, solo tune
Currently: 044 fuel pump, 630cc ev14's, hitachi MAF, 3 bar map, daz base tune

For more specifics:

Before	After
-Built level 10 auto -SRM K24 RS6 turbos -SRM bi-pipes -SRM 3-2.5" dp's -Hacked up RS4 inlets -Solo "custom" intake with a smaller filter -SOLO/J-fonz tune -Green giant injectors -Bosch 044 fuel pump -034 DVs	-6 speed swapped the car with a rebuilt 01E with AA parts -Retained the same turbos -APR bi-pipe -3" DP's -SRM inlets -Solo "custom" intake with a larger filter -Daz Base Tune -EV14 630cc Injectors -Bosch 044 fuel pump -Kept the same DV's

I'll admit I jumped head into this platform without knowing much. The car honestly ran like shit when I got it but I never knew what a "proper" stage 3 car should have felt like, and had ton of things that were hacked together. All of this was my fault for not doing enough research before purchasing.

I have since replaced / repaired / overhauled a ton of things to try to do this car justice. I know the car was not throwing any codes when I had it, but the hardware / tune left much to be desired.

[redline380]

So you swapped tunes and not MAF's? Does Daz use the same MAF's as JFonz?

[erykv1]

So you swapped tunes and not MAF's? Does Daz use the same MAF's as JFonz?

Yes, I had to change tunes due to the changes in hardware.
Both tunes use a hitachi MAF, I know it is currently scaled correctly. Cant comment on how it was before as I mentioned before.

[redline380]

Well than the only logical conclusion is that the diameter is not correct.

[NOTORIOUS VR]

Yes, I had to change tunes due to the changes in hardware.
Both tunes use a hitachi MAF, I know it is currently scaled correctly. Cant comment on how it was before as I mentioned before.

Sorry, but how do you know it's scaled correctly? Just because they are both Hitachi tunes, doesn't mean much.