Welcome to the North American Subaru Impreza Owners Club Friday July 25, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Engine Management & Tuning

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 10-03-2012, 12:08 PM   #26
Black94Snake
Scooby Specialist
 
Member#: 274499
Join Date: Feb 2011
Chapter/Region: NESIC
Location: RI
Vehicle:
2007 CGM VF'd WRX
12.70 @ 108.4mph

Default

Quote:
Originally Posted by OC_Nooby
I've seen this before on a maxima that was turbo'd. Try playing around with the MAF angle (rotate the tube).
It's sometimes refered to as "clocking the MAF". Very common in the 5.0 mustang community. Especially when dramatically changing the shape and structure of the intake tract. You have a sharp bend before the MAF, which can skew readings.
* Registered users of the site do not see these ads.
Black94Snake is offline   Reply With Quote
Old 10-03-2012, 08:13 PM   #27
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

I got the maf rotation worked out



plus did lots of testing
Bad Noodle is offline   Reply With Quote
Old 10-04-2012, 11:23 PM   #28
NSFW
Scooby Guru
 
Member#: 140444
Join Date: Feb 2007
Chapter/Region: NWIC
Location: Near Seattle, WA
Vehicle:
05 Stage Free LGT
ATP 3076, 6MT, AVO FMIC

Default

Quote:
Originally Posted by Special J View Post
If this was electrical, you should see some kind of change on the MAFv. Instead, you've got a solid MAFv, a small change on the MAF, and a big change on the correction. I'm inclined to think mechanical, like turbulence or resonance, and possibly the tune reacting too soon, too much, or both. Just my .02.
MAFv does change, you just have to look very closely to see it, because the MAF scaling is extremely sensitive at low voltages. There's a blip around the 400 mark on the x axis that stands out if you look closely. If that trace was rescaled by a factor of 10 I bet we'd see it a lot more clearly.

And I'm betting that this is electrical.

It that would also explain a problem that I had a long time ago. I was running an in-the-fender CAI that I had assembled from 3" silicone tubing, elbows, joiners, etc, and a 6" long aluminum MAF housing that had a tab that I bolted to to chassis deep in the fender well. It worked great for months...

And then one day my idle totally sucked. I was like I had a vacuum leak, but I couldn't find one. To troubleshoot, I hung the air filter and the MAF housing off of the turbo inlet like a hot-ram intake, and that worked fine. Then I tried adding the various elbows and straight bits in different combinations to find the one that was leaking, and I got a totally reasonable idle every time. Satisfied that all of the parts were OK, I bolted the MAF housing to the chassis deep in the fender-well, and re-assembled the parts in the CAI configuration, and the idle sucked again. I went back to short-ram, got a good idle, re-assembled the CAI with the filter sticking up in the air, got a good idle. Re-assembled the CAI with the filter in the fender well and the MAF housing bolted to the chassis, and I it idled like I had a leak again.

The significance of the stuff in italics never occurred to me at the time, and if it was not for this thread, I probably never would have figured it out. At the time, I couldn't figure it out, which really pissed me off. I ordered a KSTech intake and ran my parts in short-ram configuration until it arrived.

So yeah. If you want to run MAF I think you need to either insulate the MAF housing from everything around it, or ground it. I lean toward insulating it, because I have no idea whether there will be side-effects from grounding it. Subaru didn't plan for that, so there might be current flowing between the housing and the chassis. (In fact, there has to be some, else grounding wouldn't matter.) You might eventually cook something sensitive inside the ECU.

Have you tried measuring the voltage between your MAF housing and your chassis? I'm pretty sure you'll find that it's non-zero.
NSFW is offline   Reply With Quote
Old 10-05-2012, 04:57 PM   #29
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

I just got a brand new Denso MAF and tested it:



Looks like this is supposed to happen... so it's not a bad maf. It's that the maf is metal and pin #4 gets grounded through the pipe to the chasis.

NSFW is right, need to isolate the maf. I'll try layering some liquid electrical tape between the maf and the pipe and put some plastic washer on the screws that hold it
Bad Noodle is offline   Reply With Quote
Old 10-05-2012, 09:20 PM   #30
SeeeeeYa
NASIOC Supporter
 
Member#: 129681
Join Date: Oct 2006
Chapter/Region: MAIC
Location: WV
Vehicle:
2015 WRX Ltd CVT
GBP

Default

Quote:
Originally Posted by Bad Noodle View Post
I just got a brand new Denso MAF and tested it:



Looks like this is supposed to happen... so it's not a bad maf. It's that the maf is metal and pin #4 gets grounded through the pipe to the chasis.

NSFW is right, need to isolate the maf. I'll try layering some liquid electrical tape between the maf and the pipe and put some plastic washer on the screws that hold it
What I used was mica insulators used for transistors. Mine are .0025" thick, I used four... one on each side of the MAF's metal plate at each of the two mounting holes. This insulates the MAF sensor from my AEM CAI metal pipe.

While that alone changed things, even more change occured when I put a ground between the AEM CAI tube and the fender... capturing the heat shield in the process, which heretofore was also "floating" due to insulating paint.

SeeeeeYa is offline   Reply With Quote
Old 10-08-2012, 04:31 PM   #31
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

Lined the bottom of the maf housing with electrical tape and used nylon screws to hold the maf in:



no continuity from pin 4 to pipe.

so did some maf tuning with zeroed MRP table:



next gonna try to do the MRP table and see if that cleans things up
Bad Noodle is offline   Reply With Quote
Old 10-09-2012, 02:51 AM   #32
NSFW
Scooby Guru
 
Member#: 140444
Join Date: Feb 2007
Chapter/Region: NWIC
Location: Near Seattle, WA
Vehicle:
05 Stage Free LGT
ATP 3076, 6MT, AVO FMIC

Default

I have my doubts about the longevity of those nylon screws when you get into boost...
NSFW is offline   Reply With Quote
Old 10-09-2012, 06:40 AM   #33
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

Quote:
Originally Posted by NSFW View Post
I have my doubts about the longevity of those nylon screws when you get into boost...
As do I. I did order some McMaster ones that might fit a bit better, but will see. at 20 psi, they need to hold 10 lbs each. Looking at plastic properties of nylon (PA) it seems to have a high yield strength, so it looks like it would be ok.

I really can't think of a better way to isolate the maf. The only other thing I can think of is to bore out the screw holes on the maf enough to insert a plastic spacer between the maf and the screw. I don't like to the sound of that either

Last edited by Bad Noodle; 10-09-2012 at 07:31 AM.
Bad Noodle is offline   Reply With Quote
Old 10-10-2012, 06:38 PM   #34
bzbuzz
Scooby Specialist
 
Member#: 116052
Join Date: May 2006
Chapter/Region: MWSOC
Location: IL 수바루!
Vehicle:
2011 STI ( Sold )
WRB

Default

interesting..TTT
bzbuzz is offline   Reply With Quote
Old 10-10-2012, 10:25 PM   #35
NSFW
Scooby Guru
 
Member#: 140444
Join Date: Feb 2007
Chapter/Region: NWIC
Location: Near Seattle, WA
Vehicle:
05 Stage Free LGT
ATP 3076, 6MT, AVO FMIC

Default

Funny coincidence... a somewhat related thread just popped up at IWSTI:

http://www.iwsti.com/forums/2-5-lite...ry-solved.html
NSFW is offline   Reply With Quote
Old 10-11-2012, 11:47 AM   #36
djuhnk
Scooby Newbie
 
Member#: 331392
Join Date: Sep 2012
Vehicle:
2002 WRX
Black

Default

ive been having a stumbling problem at idle too. ive been trying all kinds of things, timing changes, maf scaling, injector scaling and latency. nothing seems to work, and the correction values are all over the place. my maf g/s fluctuates from around 4 to 5.5.. another coincidence- i just changed my intake setup to an aluminum maf body... maybe i need to insulate it too.
djuhnk is offline   Reply With Quote
Old 10-16-2012, 07:02 AM   #37
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

Update: Installed new MAF using mcmaster nylon screws and lining the bottom with electrical tape. It looks tunable, at least there are a lot less random stumbles / huge corrections. I used to get +25 and -25 for the same rpm and mrp, but it looks like that's gone too. I'm in the +-15 correction area and they're in separate MRP cells so they can be tuned out... looking hopeful here but don't want to get too optimistic until its done and verified.
Bad Noodle is offline   Reply With Quote
Old 10-16-2012, 07:36 AM   #38
SeeeeeYa
NASIOC Supporter
 
Member#: 129681
Join Date: Oct 2006
Chapter/Region: MAIC
Location: WV
Vehicle:
2015 WRX Ltd CVT
GBP

Default

Quote:
Originally Posted by Bad Noodle View Post
Update: Installed new MAF using mcmaster nylon screws and lining the bottom with electrical tape. It looks tunable, at least there are a lot less random stumbles / huge corrections. I used to get +25 and -25 for the same rpm and mrp, but it looks like that's gone too. I'm in the +-15 correction area and they're in separate MRP cells so they can be tuned out... looking hopeful here but don't want to get too optimistic until its done and verified.
Did you also leave the ground on the MAF tube?

I realize our setups are significantly different, however, in the airflow area covered by the LTFT table, to my thinking, there just shouldn't be that kind of corrections if all airflow connections are secure. Even crude approaches should get closer than that.

In my experience with the AEM CAI there is a fairly close corellation between both OEM as well as Cobb's MAF CAL from zero airflow up to the 40-80, or "D", range. This makes sense to me, as at these flow rates the airway shouldn't make much difference. Again, to me, merely plugging in OEM values should get one MUCH closer trims in the lower ranges than +-15%.

In any case, there can be no tuning peace as long as LTFTs are not tied down and stable.
SeeeeeYa is offline   Reply With Quote
Old 10-16-2012, 08:36 AM   #39
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

^ No, I removed the ground from the maf tube as I didn't want to ground the maf in ways it wasn't intended. I'm afraid it might fry something in the ecu and cause a world of diagnostic hurt down the road.

Your corrections in all ranges should be +-5%. That's the common accepted value for a good maf scaling. However, most intakes can not achieve this without additional corrections. This is because the flow pattern past the maf changes with rpm and manifold relative pressure. This is where your MRP correction table comes in. If on flat ground and regular cruise your maf sees 10 g/s and the car is processing 10g/s, once you hit a hill and the manifold vacuum changes for the same rpm, your maf might see 8 g/s and car might be processing 12 g/s leading to a +4 correction. Then in that table you might enter +4 for the rpm and vacuum pressure. So you're making a preemptive correction for the condition then next time you see the same conditions your corrections will be 0 as the +4 g/s needed will come from the MRP table rather then your LTFT. Each intake needs a different scaling for this table as the geometry of the piping varies between intakes.

For my setup, I have this table zeroed out for now. When I tune an intake I first try and get the corrections centered around 0 using the maf scaling, then reduce the corrections using the MRP table. You know something is wrong when you get +-large corrections for the same MRP table cell. That means there is no consistency in the airflow readings for that condition. That means there is a physical problem with your setup, bad sensor, bad signals, or something else.

For my problem, it turned out to be bad signals as well as a bad sensor as far as I can tell so far. The bad signals (maf voltage reading) were coming from the maf sensor using the maf tube as a ground, which grounded intermittently as the engine moved around. Then a bad sensor was causing random large corrections intermittently. Once I ensured the maf has grounded properly and there was no electrical interference, the only thing left that could be causing the problems was bad sensors. So I started swamping out sensors and a new maf seemed to make the difference.

Grounding the maf like you did will take care of the random grounding issue and ensure a clean signal. The only trouble I see with the fix is that the OEM setup was not meant to run like that. Pin 4 on the maf is what gets grounded and the corresponding terminal on the plug does not have a direct route to the chassis ground. It gets grounded through the ecu, which means the ecu is monitoring that pin as a reference signal So if you ground the intake to the chassis directly, you are circumventing this operation without knowing what the end results will be. One thing is certain is that there is voltage running from the ecu, to the intake, then to the chassis ground that is not seen on an oem setup. Since this problem hasn't been investigated before, no one really knows what the consequences of this will be.

Last edited by Bad Noodle; 10-16-2012 at 08:44 AM.
Bad Noodle is offline   Reply With Quote
Old 10-16-2012, 09:27 AM   #40
SeeeeeYa
NASIOC Supporter
 
Member#: 129681
Join Date: Oct 2006
Chapter/Region: MAIC
Location: WV
Vehicle:
2015 WRX Ltd CVT
GBP

Default

Quote:
Originally Posted by Bad Noodle View Post
^ No, I removed the ground from the maf tube as I didn't want to ground the maf in ways it wasn't intended. I'm afraid it might fry something in the ecu and cause a world of diagnostic hurt down the road.

Your corrections in all ranges should be +-5%. That's the common accepted value for a good maf scaling. However, most intakes can not achieve this without additional corrections. This is because the flow pattern past the maf changes with rpm and manifold relative pressure. This is where your MRP correction table comes in. If on flat ground and regular cruise your maf sees 10 g/s and the car is processing 10g/s, once you hit a hill and the manifold vacuum changes for the same rpm, your maf might see 8 g/s and car might be processing 12 g/s leading to a +4 correction. Then in that table you might enter +4 for the rpm and vacuum pressure. So you're making a preemptive correction for the condition then next time you see the same conditions your corrections will be 0 as the +4 g/s needed will come from the MRP table rather then your LTFT. Each intake needs a different scaling for this table as the geometry of the piping varies between intakes.

For my setup, I have this table zeroed out for now. When I tune an intake I first try and get the corrections centered around 0 using the maf scaling, then reduce the corrections using the MRP table. You know something is wrong when you get +-large corrections for the same MRP table cell. That means there is no consistency in the airflow readings for that condition. That means there is a physical problem with your setup, bad sensor, bad signals, or something else.

For my problem, it turned out to be bad signals as well as a bad sensor as far as I can tell so far. The bad signals (maf voltage reading) were coming from the maf sensor using the maf tube as a ground, which grounded intermittently as the engine moved around. Then a bad sensor was causing random large corrections intermittently. Once I ensured the maf has grounded properly and there was no electrical interference, the only thing left that could be causing the problems was bad sensors. So I started swamping out sensors and a new maf seemed to make the difference.

Grounding the maf like you did will take care of the random grounding issue and ensure a clean signal. The only trouble I see with the fix is that the OEM setup was not meant to run like that. Pin 4 on the maf is what gets grounded and the corresponding terminal on the plug does not have a direct route to the chassis ground. It gets grounded through the ecu, which means the ecu is monitoring that pin as a reference signal So if you ground the intake to the chassis directly, you are circumventing this operation without knowing what the end results will be. One thing is certain is that there is voltage running from the ecu, to the intake, then to the chassis ground that is not seen on an oem setup. Since this problem hasn't been investigated before, no one really knows what the consequences of this will be.
First, I think I didn't make my info clear with regard to what "grounding" I did. My ground strap from the AEM pipe to chassis grounds ONLY the pipe. The MAF sensor's ground/plate is perfectly insulated from that ground, and still follows 100% of the OEM circuitry.

This means my MAF sensor is, if anything, more free from spurious EMF than OEM now for two reasons. One, the "ground" is free of the big "antenna" of the pipe, and two, the MAF's ground has a high-freq by-pass capacitor now (created by the mica etc) that strips any remaining spurious radiation. A cleaner signal is a better signal in any case.

The end result is a significant change in my LTFT since removing the "normal" connection of the MAF's ground to the intake pipe, and then grounding the pipe to chassis. It is not drastic in terms of numbers, but in the makeup of those numbers. Where I got negative trims I now get positive, for example, not LARGER numbers. But my trims never get as high as 5%, with D always around 1% or closer. My fueling cannot afford 5%.

Just imagine this: ZERO change in circuitry, but a marked and constant change in fuel trims... that has, of course!, improved the driveability of my AEM CAI-equipped STi.

This is where I should admit I wasn't aware of the MRP table you reference. Thank you for your input and explanation. This must explain some things I need to know.

FWIW, and my anecdotal experience may not convince, but there has been a change in how the car drives since my little MAF mod that is hard to voice. The words are smoother and silkier throttle. As I put on a couple hundred miles in the mountains this past weekend I was constantly aware of this, but found putting it into words difficult. I can now, but here isn't the place.

IMO, adding a ground to your MAF tube... given that your MAF sensor is electrically independent from it... can only be good.
SeeeeeYa is offline   Reply With Quote
Old 10-16-2012, 09:43 AM   #41
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

^ ohh ok, I understand what you're doing now. I'll add the ground strap back to the intake tube and see if that reduces my corrections further. If it does, then I know that some corrections were being caused by spurious EMF. That should be an interesting experiment.

Where did you get this mica wafer? It sounds like that would help as well so I'd like to experiment with that too.

I think between our two approaches we should be able to come up with a good solution for these type of intake troubles.
Bad Noodle is offline   Reply With Quote
Old 10-16-2012, 11:09 AM   #42
SeeeeeYa
NASIOC Supporter
 
Member#: 129681
Join Date: Oct 2006
Chapter/Region: MAIC
Location: WV
Vehicle:
2015 WRX Ltd CVT
GBP

Default

Quote:
Originally Posted by Bad Noodle View Post
^ ohh ok, I understand what you're doing now. I'll add the ground strap back to the intake tube and see if that reduces my corrections further. If it does, then I know that some corrections were being caused by spurious EMF. That should be an interesting experiment.

Where did you get this mica wafer? It sounds like that would help as well so I'd like to experiment with that too.

I think between our two approaches we should be able to come up with a good solution for these type of intake troubles.
The mica I used came from my electronic junk box. They fit a power output transistor and had a hole in each end of a rectangular piece of mica. I used two wafers, snipped in half with scissors and trimmed to fit the application. The holes were small and I had to very carefully open them with a hand-held drill bit, leaving them still too small and an interference fit with the screws so they covered the maximum. Should the screws have touched I would have revised holes appropriately and used an insulating tube on the screw, probably small thin shrink tubing. But I was fortunate and it is completly iinsulated as is.

Almost any mica insulator should work, trimmed to fit. I like the mica for its mechanical strength. One on each side of each of the two holes. The only consideration is screw-to-MAF clearance, but that can be taken care of.

At this point I am certain there is a change, and that that change has made an improvement in how my car drives, at the least. I'm also sure that I can now proceed with my tuning using data I trust reflects what's happening, and not a product adulterated by behind-the-scenes garbage.
SeeeeeYa is offline   Reply With Quote
Old 10-16-2012, 02:14 PM   #43
bzbuzz
Scooby Specialist
 
Member#: 116052
Join Date: May 2006
Chapter/Region: MWSOC
Location: IL 수바루!
Vehicle:
2011 STI ( Sold )
WRB

Default

I don't have this problem with my AEM. i checked the conitunity from MAF mounting plate to AEM pipe and no continuity.
bzbuzz is offline   Reply With Quote
Old 10-16-2012, 02:40 PM   #44
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

Quote:
Originally Posted by bzbuzz View Post
I don't have this problem with my AEM. i checked the conitunity from MAF mounting plate to AEM pipe and no continuity.
Is the pipe powder coated? Did you check all the pins? (I think all the mafs are the same but you never know) What type of screws are holding the maf in?
Bad Noodle is offline   Reply With Quote
Old 10-16-2012, 03:21 PM   #45
bzbuzz
Scooby Specialist
 
Member#: 116052
Join Date: May 2006
Chapter/Region: MWSOC
Location: IL 수바루!
Vehicle:
2011 STI ( Sold )
WRB

Default

Quote:
Originally Posted by Bad Noodle View Post
Is the pipe powder coated? Did you check all the pins? (I think all the mafs are the same but you never know) What type of screws are holding the maf in?
yeh it's power coated but i put the probe on unpainted area. screws are metal that came with AEM. hmmm.
bzbuzz is offline   Reply With Quote
Old 10-18-2012, 02:19 PM   #46
SeeeeeYa
NASIOC Supporter
 
Member#: 129681
Join Date: Oct 2006
Chapter/Region: MAIC
Location: WV
Vehicle:
2015 WRX Ltd CVT
GBP

Default

Just wanted to mention, the MAF/IAT sensor on my 11 STi is different from yours... the mounting metal ears are not connected to anything. Different MAF sensors are made differently, apparently.
SeeeeeYa is offline   Reply With Quote
Old 10-18-2012, 08:09 PM   #47
Bad Noodle
Scooby Specialist
 
Member#: 174442
Join Date: Mar 2008
Chapter/Region: Tri-State
Location: NNJ
Vehicle:
2007 SuperWagon
I don't spell well

Default

Quote:
Originally Posted by SeeeeeYa View Post
Just wanted to mention, the MAF/IAT sensor on my 11 STi is different from yours... the mounting metal ears are not connected to anything. Different MAF sensors are made differently, apparently.
Interesting.... that at least explains some of the differences in what we've been seeing.
Bad Noodle is offline   Reply With Quote
Old 10-21-2012, 10:32 PM   #48
junebugfareast
Scooby Newbie
 
Member#: 167468
Join Date: Dec 2007
Chapter/Region: TXIC
Location: H-Town
Vehicle:
2004 STI
White-ish

Default

I've installed the IAT to the charge pipe to help with speed density fueling with the MAF still located in a short ram intake. The idle with that setup was inconsistent at best. After reading this thread, I grounded the two pipes to the intake. After tuning, that returned the Five-O 1400's to manufacturer's latencies. Big improvement in driveability.
junebugfareast is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -4. The time now is 11:31 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.