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

[Enlight]

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.

[Enlight]

Reserved for walkthrough.

[seanyb505]

Subbed as I'll probably go this route in 2-3 windfalls from now when I upgrade turbo and fueling. 

[TMBLKDG]

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?

[KZJonny]

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.

[Enlight]

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

[BoozeRS05]

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.

[Enlight]

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.

[KZJonny]

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 January 4, 2023 by KZJonny

[subisubisu]

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.

[shralp]

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 January 4, 2023 by shralp

[Enlight]

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

[shralp]

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.  

[shralp]

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 

[Enlight]

Run with it, @Underdog! I am going to go with an '02-'05 WRX solution though as I don't have the expertise or time to continue along your lines. I will, however, report back when I can confirm that my route works.

[m sprank]

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. 

[subisubisu]

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.

[m sprank]

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 January 13, 2023 by m sprank
More info.

[Tehnation]

WTF, efi logics doesn't do tgv deletes anymore? Oh god...... more bullshit to add to my plate. 1st they had me get a catted downpipe, now this., I really hate emissions and tree huggers...   

[gkstar]

Started down this path recently. Thank you to everyone on their research.

Found topfeed TGV from a Saabaru 92-X which is the correct 3&2 pin config, picked up an extra intake manifold and gaskets. Everything appears to line up from TGV and up. What am I missing on connection to heads as the gaskets and phenolic spacers seem to be universal? 

Costs to date

TGVs $75 

top feed fuel lines $100

spacers and gaskets from grimmspeed $108

extra manifold to test which I wish I would have grabbed from @Underdog $120

I have modded 575cc top feed injectors I need to check with a tuner if I can plug and play to get going or will look into 1050s or pick up stock 07+ top feeds

[Tehnation]

wait a minute..... where did this saab tgv idea come from? Are you saying the topfeed tgv from a saab 9-2x is plug and play with a side feed subaru harness???? The saab 9-2x is a turbo ej20 so it makes sense. You have pictures? 

So all these people on this thread are talking about programming, wiring and all this fuckery and your saying you just need a tgv from a saab? 

I just want to make sure I got this right before I go buy used set like right now lol! 

[gkstar]

3 minutes ago, Tehnation said:

wait a minute..... where did this saab tgv idea come from? Are you saying the topfeed tgv from a saab 92-x is plug and play with a side feed subaru harness???? 

Well the 02-05 WRX was on the list of ones that fit and the 92-X Saabaru is y a facelifted 05 WRX so I expanded the search. The WRX ones where hard to find 

Below is a pic of the TGV and the sensors

 

[Tehnation]

The saab tgvs would probably be cheaper cause people wouldn't know better. you got a set for 75 bucks, that says it all right there. A 75 dollar fix is whats up! Going to start looking right now! 

You have any part numbers for the saab tgvs? 

[Tehnation]

Wait a minute..... what are those studs? you have any more pictures with different angles? Our tgvs don't have studs, can we work around that!? 

[Tehnation]

On 1/3/2023 at 9:44 PM, Enlight said:

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

 

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.

I think that might be when the sti came out with the 2.5 liter thats why things get squirrely. 

I'm trying to find a tgv on carpart, but there is no tgv in drop down..... or is there another name its called? I searched for intake manifolds and thats when I saw the same 2002 and 2003 only listings.