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OEM Sidefeed to Topfeed TGV Conversion (05/06 to 07+ Conversion)


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This thread is an offshoot of a conversation started in the What did you do to your 4th gen. Legacy today? Vol - 10 thread, where a few members asked about upgrading from the '05/'06 side feed to '07+ top feed TGV's. We can use this thread to collect information about how to perform this conversion and I will reserve the post below for the completed walkthrough.

Background

Due to the EPA stepping up enforcement against tampering of emissions control equipment in cars, the aftermarket industry as a whole has been moving towards tuning solutions that retain these environmental protections. This started with COBB dropping support for emissions related functions in Accesstuner, which then trickled down to tuners that use their software. Tumbler Generator Valves (TGV's) fall within this area as they are designed to decrease emissions upon engine startup.

Previously, people wanting to boost performance of their engines performed TGV deletes in order to remove obstructions. While performing these deletes, people also often converted to top feed injectors which provide better performance at idle and elsewhere. Furthermore, there is a wider selection of top feed injectors along with better prices in the aftermarket. These top-feed/TGV delete conversions are no longer available in the aftermarket and fewer and fewer tuners are willing to tune cars with them installed (EFI Logics and Rallispec are among those tuners); this explains the new renewed interest in OEM top-feed TGV conversions nearly 17 years after this model year's release.

Conversion Information

The main differences between the plugs for side-feed and top-feed TGV's are outlined by iWire here: Plug Spotlight - TGV Plugs. The newer plug integrates the motor power with the sensor, combining the 2- and 3- pin plugs into a 5-pin plug.

Comparing 2005 Legacy and 2008 STi diagnostic information for DTC P2004 (Intake Manifold Runner Control Circuit Low) and P2016 (Intake Manifold Runner Position Sensor / Switch Circuit Low), the motors require the same amount of power and the ECM is looking for input signals above 4.5 V from the sensors. They vary (0.1 V and 0.2 V, respectively) in what they are looking for with the scan tool, but I think this might be inconsequential.

That's it for now.

2005_legacy_sensor.jpg

2008_sti_sensor.jpg

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I saw these advertised recently and thought they would have been a good way to go on my build.  If I ever get into a situation where I need to put TGVs back in I'll probably get these.  Of course, the stock top feed TGVs are easy to find and cost a lot less...

https://subimods.com/products/iag-silver-v3-top-feed-tgv-housings-with-butterfly-pass-thru-2006-2014-wrx-2007-2021-sti-2007-2012-lgt-2009-2013-fxt?

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Following this topic.

In no hurry to convert to top feeds but they are cheaper to service and replace at this point, so if I can find a set of OEM top feed rails (I believe a friend has a set on his parts engine he does not need....) then I'd dive down the low dollar conversion to OE parts.

I'm going to need a proper tune rather than the OTS I'm using now, so might as well do all the mods at once before starting down that road.

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The main issue I see for converting the wiring will be that most folks will want a plug and play solution rather than hacking up their engine wiring harness. Looking at the 2005 and 2008 wiring diagrams, the pinouts at the E2 connector (large connector over the turbo) are completely different for the TGV hardware. Fortunately the wire color code scheme was maintained between model years. We'd likely want to make a harness adapter that plugged into the sensor and actuator connectors and merged them into the single 5-pin connector for the topfeed style TGV assemblies. My engine wiring harness is all custom for the STI swap, so this would be a great piece of the project for someone else to pick up. Edit: It certainly seems like the folks at iWire would be able to do this given the information they have here: https://iwireusa.com/blogs/iwire-university/plug-spotlight-tgv-plugs?_pos=1&_sid=ca3167f46&_ss=r

 

The pinouts, for reference:

 

2005:

TGV Angle Sensor LH -> E2

Pin #1 -> #20 (shared 5V power supply)

Pin #2 -> #19 (shared sensor ground)

Pin #3 -> #11

TGV LH (Actuator) -> E2

Pin #1 -> #33

Pin #2 -> #22

 

TGV Angle Sensor RH -> E2

Pin #1 -> #20 (shared 5V power supply)

Pin #2 -> #19 (shared sensor ground)

Pin #3 -> #10

TGV RH (Actuator) -> E2

Pin #1 -> #32

Pin #2 -> #21
 

 

2008 (The sensor & actuator combined into single unit with 5-pin output, I'm displaying with a similar format to above for clarity):

TGV Angle Sensor LH -> E2

Pin #1 -> #27

Pin #2 -> #6 (shared sensor ground)

Pin #3 -> #28 (shared 5V power supply)

TGV LH (Actuator) -> E2

Pin #4 -> #30

Pin #5 -> #29

 

TGV Angle Sensor RH -> E2

Pin #1 -> #16

Pin #2 -> #6 (shared sensor ground)

Pin #3 -> #28 (shared 5V power supply)

TGV RH (Actuator) -> E2

Pin #4 -> #19

Pin #5 -> #8
 

2005 LGT TGV Pinout.pdf 2008 LGT TGV Pinout.pdf

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51 minutes ago, Underdog said:

The main issue I see for converting the wiring will be that most folks will want a plug and play solution rather than hacking up their engine wiring harness. Looking at the 2005 and 2008 wiring diagrams, the pinouts at the E2 connector (large connector over the turbo) are completely different for the TGV hardware. Fortunately the wire color code scheme was maintained between model years. We'd likely want to make a harness adapter that plugged into the sensor and actuator connectors and merged them into the single 5-pin connector for the topfeed style TGV assemblies. My engine wiring harness is all custom for the STI swap, so this would be a great piece of the project for someone else to pick up.

Paging @k00laid83 @MaasaiWarrior

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In on this thread, although I’m not nearly as educated as you folks. I do have all the parts that I pulled from my 08 specb already in boxes if I can help with pics and/or loaner parts though.

I’d eventually want everything back to convert once my motor goes, which hopefully won’t be in the next year or so.

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Here's the response I got back from iWire, which states that this swap will not work due to the switched polarity:

Quote

 

Hi Enlight,

Happy New Year to you too! Unfortunately, this will not work because the polarity of the TGV sensor and motors are backward from what the ECU expects, and simply flipping the pins around doesn't work. You would need a 3-pin/2-pin combination top feed TGV housing like one from an 02-05 WRX.
 
Thanks,
B
Level 3 Tech

 

 
So people who are interested should start calling up your junkyards. A quick eBay search turned up few options. I hasten to add, I think it might only be '02-'03 WRX's that have what we are looking for, further limiting our options. I could not find top feed WRX TGV's after '03 - perhaps someone can correct me.
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I wonder if the hardware (minus motors and sensors, per iwire) from a top feed LGT might work, with those parts with the correct polarity swapped over?

Probably too much $$$, and I didn't look at prices, if they're even available. But it might still come in less than an aftermarket kit?

Edit:

Idle speed control motors - $160/side (14120AA060 / 14120AA050 ) Some ambiguity here about what fits what model and year.

~$90 each for TGV/TPS sensors, with the correct polarity.... Seems like they're the same parts, from a quick search...

So.... find one from an old Rex?!

I figure at almost $500 USD for a retrofit, the $1000CAD ($700 USD?) ID 1050x kit looks pretty good for brand new and under warranty… (nope. Iag looks better)

Too bad about the polarity not working out.

Edited by KZJonny
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How timely for me.  I used the holiday break to start picking back up with my 2005 OBXT build, which had bogged down for a number of reasons, among them the recently increased difficulty of working with pro tuners if certain elements like the TGV were missing from the car.  My original plan of converting to top-feed TGV delete was out the window.  I looked into what it would take to use the later-model top-feed TGV (I got one from an STI) with the 5-pin connector and encountered all the info above once I started looking at the vacation photos and doing the comparison.  I even ordered the connectors from iWire and started work on a possible solution, but didn't complete it and so didn't have anything to post.  But the direction in which I was going to attempt the adaptation of the 5-pin system to the 2005 ECU was to use an op-amp to do the signal inversion.  By inversion, understand, is that one system wants to see +5V when the actuator has extended, and the other wants to see 0V, as I recall.  I have no idea what processing is done on the signal once it is received by the ECU; presumably it does some sort of comparison and eventually decides it's seeing a failure if it expects one value and sees another, but whether my idea would pass muster with the ECU is yet unknown.  It will be a while before I can test it on my build, but I thought I'd toss it out here in case anyone might benefit, either from the do-ability or otherwise.

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That's disappointing about the polarity. So it seems like there are a few different paths at this point:

2-pin/3-pin top feed TGVs from the 02-05(?) WRX - I found part numbers 14011AB363 and 14011AB373 for these. Not sure how they will bolt up to B25 heads or the LGT intake manifold, but assuming they play nicely it's likely a ~$600 solution for both sides, plug and play.

Manipulating the I/O with the 5-pin top feed TGVs like @subisubisu mentioned. Any EE's here who could help out with this? It seems like a small circuit enclosure in-line with the adapter harness could be a good solution.

A mechanical solution to directly couple the 2-pin servo and 3-pin sensors, allowing the ECU to see normal operation. Ideally we could reuse the majority of the mechanism but I'd need to take one apart to see if it's feasible.

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I had a similar issue this fall when I had a compression check done on my track car as it was potentially showing signs of getting tired and in need of a new short block, (the shop I took it to totally phoned in my comp check, gave me low readings and so I took it to Cobb Surgeline for a new motor.  They did their own compression check and the motor is FINE.  But that's a whole 'nother story).

Anyway, new motor was going to mean a new tune which meant my Top Feed IAG TGV deletes were going to have to get tossed.  Since the newly released IAG TGV's had not been released yet, I looked at OEM options to gut.  The '06-'08 Forester XT TGV's are 3 pin Top Feed and will drop right in.  I pulled the butterflys out and did a light porting job to smooth out and remove material that the butterfly rests on when its closed.  Kept the rod and chose not to remove the partition wall as it wasn't really necessary at my power levels.  For those not wanting to pay for the new EPA compliant IAG TGV's this is a good low(er) cost option.

...and in the end I didn't even need to get them, now they are just sitting in a box :( 

Edited by shralp
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8 minutes ago, Enlight said:

@shralp Were you able to confirm that the '06-'08 FXT TGV's have the polarity that the LGT ECU is looking for?

Good point. Did not confirm that real world as they never went in so can't say with 100% assurance so thats probably worth pursuing to make sure.  

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1 hour ago, Underdog said:

@shralpIf you feel like parting with them I’d be happy to buy them off you and compare them with a Legacy set I am getting from seanyb505. Assuming Enlight or someone else hasn’t already offered, of course. 

Hadn't thought about that but yup, they are not doing me any good right now and if I do end up being forced into TGV down the line for the track car I'll most likely go with the IAG offering anyway.  Surgeline told me it was going to be a pretty tight fit with the new turbo that I was going to put in, (that was supposed to go along with the winter re-power that never happened).  The IAG's have a slimmed down footprint to allow for bigger turbos so I'll end up going that route if I have to.  Feel free to ping me a PM and we can chat on it if you're interested in them 

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I looked up the TGV I/O info in the manual and confirmed that the sensor polarity is flipped between the 05-06 and 07-09 setups.

05-06: 3.8-4.9V (Closed), 0.2-0.9V (Open)

07-09: 0.4-1.2V (Closed), 2.8-4.6V (Open)

The good news is that it looks like the actuators operate simply by toggling 12V and ground between the terminals to open/cose.

In the DTC detection criteria I don't see anything that implies the ECU monitors the characteristic of the TGVs opening or closing, only that they report fully open or fully closed within a certain amount of time (2-3 seconds). Because of this, I think the best solution would be a small circuit board in an in-line or remotely mounted enclosure, that plugs into the engine wiring harness connectors. With that circuit developed, it seems trivial to both an 05-06 version and a 07-09 version, using a jumper on the PCB and different plugs for the 2/3-pin and 5-pin styles.

At this point I need help from someone with circuit/PCB design experience to move the idea further.

Alternatively I found these APS servo plates on NASIOC and have thought about trying to recreate them, but this path is far less ideal than the electrical solution as it will be more costly, more prone to failure, and require the original sensors/actuators and end-user assembly.

DrjKsMC.jpg

mWxmwrj.jpg

 

2005 LGT TGV Sensor Info.pdf 2008 LGT TGV Sensor Info.pdf

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Just a thought....  EcuTeK.  Why has no one turned to EcuTeK as a tuning solution?  UK based, so they dont give a damn about US regulations.  You can still use the old hardware and disable all those CEL's if you tune with EcuTeK. 

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You know Mike... that's a good question. EcuTek hasn't been on my radar for quite some time. Not planning to have my car through another tuning iteration, but something to keep in mind for sure. Of course open source tuning is still a thing as well. 

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I looked at Haltech, probably because i've seen so many Mighty Car Mods videos.  They have plug and play solutions for some Subarus with harness adapters and maps for their ECUs, but not for our Gen 4 Legacy.  I'll have to look at Ecutek.  If I can't use the current harness, though, I think I'd be better off with open-source tuning of our stock ECU.  I wouldn't mind the engine wiring so much, but the dash and the rest of the car, jeez louise.

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EcuTeK is software based like Cobb or OS.  No hardware or wiring changes. You purchase a USB dongle that is the "key" to the software.  A cable to connect via the OBD2 port is provided with the dongle.  OEM ECM and the ECM is NOT locked. No self tuning, pro only.  You can not tune the car, but you can log the car so remote tuning is also an option. 

 

In all reality, OS is an old reverse engineer of original EcuTeK software. 

Edited by m sprank
More info.
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