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Thread: Shock Tower Brace doesn't clear a VF48???

  1. #1
    rori's Avatar
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    Shock Tower Brace doesn't clear a VF48???

    Has anybody else bolted a VF series turbo in their 818? I have a VF48 from an STI. The shock tower brace is resting on the waste gate arm before I can bolt it to the chassis. I'm surprised the clearance is that tight and that there is that big of a difference from the TD04. Surprised I haven't seen it mentioned before. I'm wondering if there is going to be an updated brace once the STI is officially supported.


  2. #2
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    I'll preface this with I haven't built mine yet.

    Does the engine use the stock motor mounts?

    There are several motor mounts for the Impreza that will drop the engine a bit. IE if the WRX motormounts are in there, the solid MSI mount will drop you the few mm you need.

  3. #3
    Senior Member Goldwing's Avatar
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    Hmm, I was seriously considering the vf48. The motor mounts are standard, yes. That could be an option. I'm not able to check my frame, you might be able to shift the engine left a bit, dropping the right (turbo) side and raising the left. Check the orientation of the slots in the engine mount cradle of the frame. Just brainstorming.

    Doesn't look like you need much, but you'll want room for engine movement.
    Rich

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  4. #4
    rori's Avatar
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    I'm using the SPT mounts, same dimensions as stock. Motor is mounted level with even spacing on the mounts. I can just clearance that bar if needed, but if FFR is planning an STI compatable bar then that would be nice to have. I'm curious if they have ran into the same thing as they prepare to accomidate STI donors.

  5. #5
    Senior Member Xusia's Avatar
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    I am running a VF39 and have no clearance issues. I don't know how similar in size a VF39 is to a VF48.

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    The hot side on the vf48 is larger than the bf39 and the reference angle of hot side to cold side is slightly different. Cusco, beatrush, MSI, pretty much any solid or sudo solid engine mount should drop you enough to allow for clearance on the WG ARM. Judging from the pics at least. Changing the frame is a much larger undertaking.

    Would be great. But since they haven't made the changes to allow for the STI hubs, I wouldn't hold my breath on frame changes for late model STI turbos.

  7. #7
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    wallace18's Avatar
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    You could do an easy mod to the shock tower brace so it works. Just add plates and clearance the area around the turbo. You can paint or repowder coat.

  8. #8
    Mechie3's Avatar
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    The factory heatshiels and most aftermarket heatshields don't fit either. A little more space would have been good.
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  9. #9
    Senior Member metros's Avatar
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    ^^^Turbo blanket?

  10. #10
    rori's Avatar
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    Went ahead and notched it. It didn't require much.


  11. #11
    Mechie3's Avatar
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    Quote Originally Posted by metros View Post
    ^^^Turbo blanket?
    It's certainly an option, but given than a majority of people will be using a turbo (most likely) and it's a factory setup, you'd hope there would have been a provision to use free (donor) parts or commonly available aftermarket parts (that many donors also might have) rather than needing to buy another part.
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  12. #12
    rori's Avatar
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    I had a COBB heat shield sitting here that came off of one of my donors. I was excited to use it, I guess not though. Off to ebay it goes.

    I mistakenly thought the VF48 came from an 07 STI, but I forgot that the 07 STI was the one year only VF43. The VF48 is from the 08+ STI so I guess it won't ever be officially supported.

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    The stock engine and tranny mounts are pretty much jello anyway. And dropping the engine further only help CG.

    Notching that bar looks to work. But lowering the engine would allow for greater clearance all around.

    Unless doing so would create other issues. Would dropping the engine and tranny cause other clearance issues. The turbo I'm planning on is even larger than that vf48 and I'm trying to plan ahead.

  14. #14
    Senior Member Xusia's Avatar
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    Using the stock engine mounts and oil pan, the bottom of the pan sits approximately flush with the bottom of the framing underneath, perhaps protruding downward a bit. You won't be able to drop the engine much before the oil pan is the lowest thing on the car. I think that might be a bad idea. Modifying the shock tower brace seems both easier and safer.

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    Or a really good excuse to get a dry sump.

    The shock tower is load bearing. Hacking it up doesn't sound too safe either.

    Might be off to plan D). Custom rotated up-pipe.

  16. #16
    Senior Member RM1SepEx's Avatar
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    Quote Originally Posted by ssssly View Post

    The shock tower is load bearing. Hacking it up doesn't sound too safe either.
    this is an easy fix, add plate steel to the sides of the cut and it will be just fine

    BTW you need to be prepared to modify the design a bit if you are not using approved donor bits, it is not rational to expect FFR to modify their design for "your" mods
    Dan

    818S #17 Picked up 8/1/13 First start 11/1/13 Go Kart 3/28/14

  17. #17
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    Putting plate steel back over the cutout would cause the same clearance issue that the strut tower was cut to fix.

    Installing another stock Subaru turbo isn't really a "mod" that most would expect to cause such a substantial issue.

    I am installing a much larger Borg Warner turbo so I am expecting custom work to be required to do so. But a vf48 is a stock small frame turbo. I was pretty surprised that the shock tower clearance was that tight. That turbo is about 3mm larger than a vf39. Maybe 1cm larger than a td04.

    I think the particular issue with this turbo is the wastegate arm orientation. Others have used vf37s without clearance issues. The vf37 is a larger turbo, but the wg arm is clocked more to the right.

  18. #18
    Senior Member Xusia's Avatar
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    I agree with Dan. Adding rigidity to the shock tower brace is easy, and you can do so without causing any other clearance issues. It seems to me you could weld in a triangular piece of steel right above where you notched the bar. If you are super paranoid, you could weld in 2 pieces (at both edges of the bars).

  19. #19
    Senior Member RM1SepEx's Avatar
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    I repeat ANY parts that are not stock on the specific models may incur EXPECTED modifications to the kit, as provided.

    You can not reasonably expect FFR to have evaluate ALL of the "common modifications" to these power plants or other areas of the cars. This is an excellent example, Rori has defined the problem and simple solution. I would add some plate steel bracing to both sides of the bracket to replace the strength of the brace that has been cut.
    Dan

    818S #17 Picked up 8/1/13 First start 11/1/13 Go Kart 3/28/14

  20. #20
    Senior Member Bob_n_Cincy's Avatar
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    The waste gate pivot pin looks much shorter on the td04 turbo. That is what caused your problem
    tdo4side.jpg
    Bob

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    I'm not sure where you are seeing someplace to weld a steel plate back over that hole.

    The wastegate arm travels 2cm. If you boxed that steel back in with a plate the wastegate arm won't actuate.

    This could also be solved by going to an external wastegate. Removes the actuator arm and installs the wastegate vent 5cm down the up pipe.

    You could triangulate that shock tower off other frame components. But at that point I would be more inclined to leave the strut tower intact, drop the engine and weld in protection for the oil pan.

    Many solutions to the problem.

  22. #22
    Senior Member Xusia's Avatar
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    You didn't mention any names, so I'm unsure if any of your questions were directed at my comments. Just in case they were, I mentioned welding in a triangulating piece of steel ABOVE where you notched the bar. Were I not on a mountain skiing, with limited computer tools, I would show you by diagramming your pic. If what I said doesn't make sense, please let me know.
    Last edited by Xusia; 03-23-2014 at 10:19 AM.

  23. #23
    Senior Member RM1SepEx's Avatar
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    correct, you triangulate with plate, not "box in the cut"
    Dan

    818S #17 Picked up 8/1/13 First start 11/1/13 Go Kart 3/28/14

  24. #24
    rori's Avatar
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    Quote Originally Posted by Xusia View Post
    You didn't mention any names, so I'm unsure if any of your questions were directed at my comments. Just in case they were, I mentioned welding in a triangulating piece of steel ABOVE where you notched the bar. Were I not on a mountain skiing, with limited computer tools, I would show you by diagramming your pic. If what I said doesn't make sense, please let me know.
    I'm not the one arguing with you. I've moved on. I'm fine with the notched bar. I don't think it reduced the rigidity of the bar at all. If someone felt the need they could indeed reinforce the area.

    I think we can close this thread as I realized my mistake. The VF48 won't ever be officially supported. It will be interesting to see a redesigned bar is needed for the VF43

  25. #25
    fasterer and furiouser longislandwrx's Avatar
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    Thanks for posting, another thing I will add to the list of problems I will have shortly.
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  26. #26
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    Sorry, hate to be the dick, but notching that bar has eliminated its structural rigidity by a factor of at least 10-2.

    The following paper lays out the forces and calculation pretty succinctly https://www.efatigue.com/training/Chapter_7.pdf

    Pay particular note to the graphs of fatigue failure for solid vs notched beams.

    Compounding the problem here, is that by cutting through 2 attached sides you have also removed the ability of the beam to distribute applied force throughout the entire beam. Focusing the force at the sharp angle on the right hand side of the cuts. The force here will have raised by ~3 fold.

    So if the original strength of that beam was say 10,000lbs, its now 100lbs. And if the average imparted force from the suspension on that bar is 1000lbs, it will focus a 3000lb force directly to that sharp angled notch on the right hand side.

    Is this within safe limits to not snap that bar like a twig? I have no idea, I didn't design it. But neither do you. And suggesting it as a solution to turbo fitting issue, without input from the original engineer, is dangerous. Looking at the FFR solid works video, it looks like about 5000lbs of force can be applied to this bar just through frame flex. And suspension forces would be in addition to that. So in order for it to be safe with the notch, the original spec would have had to have been in excess of 60,000 lbs. Otherwise it will bend or crack.

    With a rear mounted engine, if that bar bends or cracks under load, during a turn, it could result in a horrible accident. You might think that its no big deal and good to go, thread closed. But this is a modification that could kill someone.

    It would be great if someone from FFR, maybe the frame engineer, would chime in here to actually answer the question. I emailed them, we'll see what they say.

    I would strongly suggest you coat the area around the cut with a brittle material, like stresskote or similar, so that you can see cracks in the coating if it starts to bend. If your coating ever cracks, at all, it is no longer safe to drive.

  27. #27
    fasterer and furiouser longislandwrx's Avatar
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    I think boxing out your cut and creating a truss out of the side there with square tube would work wonders for strength

    untitled.jpg
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  28. #28
    Senior Member STiPWRD's Avatar
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    Personally, I would modify the exhaust piping to either lower or rotate the turbo. This is more work than just cutting the frame but in the end will look better and more symmetric. Most of the strength could be recovered with boxing the cut frame and adding trusses but I'd rather go the exhaust mod route.

  29. #29
    fasterer and furiouser longislandwrx's Avatar
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    To lower the turbo by shortening the uppipe what looks like at least 3/4" you are most likely going to have issues with the inlet rubbing and the intercooler hose lining up with the turbo

    Doing a custom rotated setup would be a good way to go as there is plenty of room for a custom inlet.

    I'll figure something out. modifying the brace is a quick way to go without resorting to stacks of custom parts.
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  30. #30
    Senior Member metros's Avatar
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    Size comparison of a Blouch 18g (7cm) vs the vf48? Wondering if I'll have to address the same issue.

  31. #31
    Senior Member Goldwing's Avatar
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    Reviving this thread to get a few opinions. So, I installed the VF48 turbo I found a good price on years ago completely forgetting why I was waiting to install it (lack of off the shelf tunes to use while continuing the build and this issue, shock brace clearance.). The mental awareness was completely dumped over the last four years sitting idle. So, now I face this issue, lol. Looks like rori sold his (gathered by search results while digging here), so may not be around to report on final version. I don’t want to just notch the 1” bar for strength and I don’t think the notch allowed for sufficient clearance for engine movement anyway. So, I came up with this detour design. It follows what I’ve seen Reese do to snake around exhaust or other obstacles with their tow hitches, but I’m not an engineer. Two versions, identical except for a plate on the second to further spread the forces out at corners. I’d basically cut 3 sides of the bar where the 3/4” angled piece comes down and sister the two bars together with a weld joint. I’d bend the side near the original weld joint since I can’t get in there to weld that side, then fill the void created by that bend with a matching piece, perhaps from cutting the bend above the waste gate actuator. Finally fill in a piece to join the original bar with the detoured bar. Orange indicates welds. Red shows cuts. Gray the rerouted bar. Yellow the relief plate. I imagine sufficient strength is maintained and this will allow for more movement than a notch. I just used rori’s pic from above, my car was identical where the actuator wound up. The stiffer engine mounts gave me the same concerns on engine movement under load. Would it ever strike the bar? Delicate part.
    88730115-FCAA-45E6-B8EC-3D39018B340E.jpeg88001CBA-39AA-49DA-B644-1AE57F0F2EC8.jpeg
    Rich

    818S in progress. 2007 WRX sedan donor.
    Powered up: 7-8-14, First Start: 7-20-14, Go kart: 8-19-14

  32. #32
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    What if you just cut down the size of the pivot pin and weld the actuator back on? Or external wastegate.

  33. #33
    Senior Member Goldwing's Avatar
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    That’s not a bad thought. I hesitate with my rather beginner welding abilities, to go after modding the more expensive part, lol.
    Rich

    818S in progress. 2007 WRX sedan donor.
    Powered up: 7-8-14, First Start: 7-20-14, Go kart: 8-19-14

  34. #34
    Senior Member Pearldrummer7's Avatar
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    My VF39 was a really tight fit (guess my aftermarket exhaust parts added up to being slightly higher than normal), and ended up with an external wastegate and removing that arm. I too worried about my welding abilities and the impacts on the strut tower brace.

    I'm not super well versed in dynamics, but my understanding is that the strut tower brace loses a lot of functionality if it ends up not being straight. Not sure how needed it is on such a tight framed car, but if you're gonna have it I'd rather it be straight than angled.
    Frank - Build thread

  35. #35
    Senior Member metros's Avatar
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    Wow its been forever since I've seen you on here. You could always just tack everything in place and have a trusted shop finish weld it. I'm with others in thinking it would be a better idea not to modify that cross bar. Adjusting the up-pipe would be a much cleaner solution.

  36. #36
    Senior Member Pearldrummer7's Avatar
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    Quote Originally Posted by metros View Post
    Wow its been forever since I've seen you on here. You could always just tack everything in place and have a trusted shop finish weld it. I'm with others in thinking it would be a better idea not to modify that cross bar. Adjusting the up-pipe would be a much cleaner solution.
    It's been a few years for me; thanks for noticing. Life got in the way of car work; hopefully I'm back to stay
    Frank - Build thread

  37. #37
    Senior Member Goldwing's Avatar
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    I guess I wasn’t the only one on the sidelines for a while. Welcome back to you too! I still have to chew on this cross bar thing. Working on legal bumpers in the meantime. See what other dilemmas I can get myself into.
    Rich

    818S in progress. 2007 WRX sedan donor.
    Powered up: 7-8-14, First Start: 7-20-14, Go kart: 8-19-14

  38. #38
    Senior Member Goldwing's Avatar
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    Looking at the turbo differences between stock TD04 and the VF48, the VF48 waste gate actuator isn’t just taller, it’s clocked closer to the main exhaust stream. Shortening the post would cause interference with one of the flange bolts. To shorten it, one would need to change the angle the actuator attaches and come up with a bracket for the actuator in its new location. Or, reworking the exhaust and compressor output. Boy, the shock tower bar reroute just seems the simpler solution and makes room for the turbo shield. If tow hitches that snake around exhausts can pull 3,500 lb trailers, I think we can come up with a strong solution. I can beef up the upper bar with a 1” bar for the detoured section for extra stiffness as well with my plan. The 1/8” wall 1” tubing I sourced for the rear bumper fits nicely over a 3/4” bar.
    Last edited by Goldwing; 10-09-2019 at 06:44 PM.
    Rich

    818S in progress. 2007 WRX sedan donor.
    Powered up: 7-8-14, First Start: 7-20-14, Go kart: 8-19-14

  39. #39
    Senior Member Goldwing's Avatar
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    I was planning the rear bumper out today. With plans to tie in at the lower horizontal bar on the tail and the shock tower bar mount, if I run an extra straight bar across between the upper bumper mounting plates, I can easily make up for any lost strength of the shock tower brace due to the detour around the vf48. Checking transmission oil looks like it might get tight, but I can make room for the turbo shield with less worries. Instead of an external waste gate, external shock tower bracing.. I’ll post a pic once I get it mocked up.
    Rich

    818S in progress. 2007 WRX sedan donor.
    Powered up: 7-8-14, First Start: 7-20-14, Go kart: 8-19-14

  40. #40
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    I'm using a VF-48 too. After reading this thread I decided to put reinforcing plates on each side tying the horizontal tube into the top angle tube. See pics. 20191006_072145_resized.jpg20191010_192652_resized.jpg

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