Auto Opening Trunk

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#1
OK, so many of you have probably seen i1Tesla's Auto opening trunk and frunk mods here. So I take no credit for this idea.

However, minutes after he posted it, the struts and the springs sold out ACROSS THE ENTIRE INTERNET!!! OK, so maybe I'm exaggerating, but there was briefly a seller on Amazon trying to rip people off by charging $160 for the pair of struts (should be $20). So you need a new, shorter strut (Strongarm 4129), and a 40MM long compression spring (and optionally washers). So I set about the task of tracking down usable parts for the job because I really would like the trunk to open when I tell the Tesla to open it.

Anyway, I was able to track down the struts from RockAuto, shipped to my house for about $30. Sadly, RockAuto only has 1 left in stock, and you need 2 to complete this job. Someone on Youtube ordered the alternative part (Boxi Struts) and we will know (hopefully soon) if the struts are as interchangeable as the specs indicate.

So, as for the springs, i1Tesla used 25mm OD (outer diameter) x 40mm long RED compression springs, with washers because the ID (inner diameter) was much bigger than the strut rod it would click down on the cylinder (probably not good since the cylinder has compressed gas in it that we don't want to risk letting out). Just as an FYI, the Strongarm strut rod is 8mm diameter. The 25mm OD spring has an ID of around 12mm. I ordered the 25mm OD x 40mm RED springs from the manufacturer (they were immediately sold out on Amazon), but it seems as though they are shipping from Hong Kong, so who knows how long they will take to get here (I still have gotten no confirmation from the vendor that they received my order, although Paypal sent them the money).

One thing to note about these die springs is that the color is representative of their spring load (I learned some new things while researching this). The loading grade of die springs in various colors (from lightest load to heaviest load) is: YELLOW, BLUE, RED, GREEN, BROWN

So BLUE should have a bit less force than RED, but might be enough to get the trunk open enough to auto-pop. I certainly didn't want a heavier load spring, as it would be more force and would probably make it uncomfortably hard to close the trunk all the way. So, I started looking at what BLUE load springs were available.

So, I found a few options on Amazon that were in stock and thought I'd try some out. I got a 22mm OD x 35 mm long BLUE spring, and tried to add additional washers to account for the 5mm shorter length, but they did not appear to work. Although I only had one (all that were in stock), so I'll have to see when my 22mm OS x 40mm long BLUE spring comes in to know for sure.

I also have ordered an extra long 25mm OD x 80mm long BLUE spring and used a hack saw to cut it into 2 40mm long springs. Added some stainless steel washers to account for the cut ends, as well as the extra space caused by the too large ID on the 25mm springs. That, paired with the Strongarm struts worked perfectly. Trunk pops open enough that the struts will then take over and open it the rest of the way.

Just for an FYI, I also have some other springs being delivered, because I still feel like an ideal spring for this would be two 20mm OD x 40mm long BLUE springs (or one 20mm OD x 80 mm long spring cut in half). This would be a nice tight fit around the strut, and might negate the need for one or both washers. I'm not sure if the load is decreased by the smaller 20mm OD springs, so maybe the smaller BLUE springs won't cut it, and I might have to bump up to 20mm OD x 40mm long RED springs.

So, I know there are a lot of links to different products, so I will summarize what items worked, which are untested, and which didn't work:

Currently Testing:
Strongarm 4129 struts, 20mm x 40mm RED springs, 2 stainless steel washers on each strut. This seems to work, and I really like the smaller 20mm springs, as they fit nicely on the strut shafts. We'll see if they can consistently pop the trunk enough to open it.

Verified working combinations:
Strongarm 4129 struts, 25mm x 80mm BLUE spring cut in half, 2 stainless steel washers on each strut. Note: I have some paint rubbing off of the blue springs, which means the 25mm OD springs must be rubbing agains the car when it is closed, going to look for smaller OD spring.
Strongarm 4129 struts, 25mm x 40mm RED springs, 2 stainless steel washers on each strut. This works every time, but opens with more initial force than I care for.

Unverified combinations that should work:
Boxi BX54667 struts, 25mm x 80mm BLUE spring cut in half, 2 stainless steel washers on each strut.

Verified not working combinations:
Strongarm 4129 struts, 22mm x 35mm BLUE spring, 2 stainless steel washers on strut. (only one side had spring, so this is not really a good test. More to come when I get 22mm OD x 40mm spring tomorrow)
Strongarm 4129 struts, 22mm x 35mm BLUE spring on one side, 22mm OD x 40mm BLUE spring on the other, 2 stainless steel washers on 40mm spring side, 6 on the 35mm side to account for the 5mm difference. This simply did not work consistently, and was too hard to close for my liking.
Strongarm 4129 struts, 20mm x 80mm BLUE spring cut in half, 1 stainless steel washers on each strut to cover the hacksaw cut end. Not enough spring power to get the trunk to pop.
 
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#2
OK, so I wanted to test something, and it appears that the BLUE springs may not be enough to pop it open after sitting for a while in cold weather. It's in the mid 30's (F) here and I went to open the trunk after a couple of hours sitting and it didn't auto open. After closing and immediately trying again, it worked. So the spring load may need to be RED after all. I will update the latest results here.
 

MelindaV

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#3
so, just as a cautionary piece of advice...
I normally begin pre-heating my car when getting ready to leave my office. Recently, I did this and put my phone in my pocket (with the Tesla app still on the screen). I got sidetracked before leaving and pulled my phone back out to check the cabin temp and noticed it showed my trunk open and car unlocked. tried to tap the lock button, but because the trunk was unlatched, it would not re-lock. So when putting my phone in my coat pocket, I apparently inadvertently opened the trunk.

Went downstairs and the trunk indeed was not latched. If the struts were to pop the trunk up, it would have been obvious to anyone within a block that there was an unattended car wide open (for any cold homeless guy to curl up in, being it was now 70F).
 

SoFlaModel3

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#4
I’m on the fence with this one. I did the frunk, but the trunk... it’s abnormally hard to close and this will make it worse. I really want auto close more than anything.
 

Skione65

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#5
so, just as a cautionary piece of advice...
I normally begin pre-heating my car when getting ready to leave my office. Recently, I did this and put my phone in my pocket (with the Tesla app still on the screen). I got sidetracked before leaving and pulled my phone back out to check the cabin temp and noticed it showed my trunk open and car unlocked. tried to tap the lock button, but because the trunk was unlatched, it would not re-lock. So when putting my phone in my coat pocket, I apparently inadvertently opened the trunk.

Went downstairs and the trunk indeed was not latched. If the struts were to pop the trunk up, it would have been obvious to anyone within a block that there was an unattended car wide open (for any cold homeless guy to curl up in, being it was now 70F).
@MelindaV,

This has always been my worry with the app on the screen and putting my phone in my pocket.....fear of inadvertently pushing a button and opening something...so I close the screen before I put it in my pocket.....it’s an inner pants dialing thing akin to butt dialing....I use my front pocket though...so as not to crack my screen sitting on it.
The other thing I do is NEVER close my door without looking at the darn window to make sure it’s pre-dropped for the frameless so I DONT scratch my darn bright work!
So far that hasn’t bit me yet....knock on wood.

Ski
 

MelindaV

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#6
It is weird that it happened to me, because you do have to confirm to open the trunk (but don’t have to confirm the unlock option), so really not sure how I could be so lucky to both tap the trunk button and the confirmation button unknowingly, but know when I turned on the heat, it was locked and the trunk closed.
 
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#7
@MelindaV I agree that should be considered, but I had an auto opening trunk for years in my old car (if you held down the keyfob) and never had it open accidentally. Obviously the ability to pop it remotely from app adds to the equation here. Also, on the flip side, if you accidentally pop it and don't know, and a torrential downpours strike, you may end up with a flooded trunk. So maybe it's good to have visual indication that the trunk is popped :)


@SoFlaModel3, I agree with the concern. My Model 3 trunk is not too bad to close, but it was certainly why I was trying to find the lightest springs possible to make this mod work. It is certainly good to mention that you perform a mod like this at your own discretion, and you should know there may be a reason Tesla didn't add this to the Model 3 themselves. It could be because of @MelindaV's concern, or yours, or both. I just know that being able to tell Siri to pop my trunk on the way to the car and have it be fully open when I get there is useful when I have my hands full of shopping bags.
Also, as an update to my slightly too weak spring concern, I was only able to get a 50% success rate today on getting it to pop automatically. I feel like I'm fractions of a lb of force away from having the right setup.

Agree that Autoclose would be awesome, but there will be no way to make that work without crazy hacks and other mechanisms (Raspberry Pi with cell radio, controlling pnumatic system?!?).

Also @SoFlaModel3 , wanted to thank you for the video showing the custom wrap on the console. I did the Kenriko wrap, but had a few spots that weren't perfect and I was considering a redo, but after watching the video and seeing how heat could be used to revive the vinyl, I was able to use a torch the same way as your installer to smooth out a couple of wrinkles at the edge and get the edges around the cup holder to stay tucked for good.
 
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#8
any update on the "untested combinations"? i want to add this to my trunk, but need to know what parts to order.

Thanks!
 

modelo tres

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#9
I'm not sure if the load is decreased by the smaller 20mm OD springs, so maybe the smaller BLUE springs won't cut it, and I might have to bump up to 20mm OD x 40mm long RED springs.
Outer spring diameter definitely has an effect on the overall spring rate or force per mm.

If you get a smaller outer diameter spring, then you may need to go to the green springs.

See this catalog for examples.

https://www.daytonlamina.com/sites/default/files/doc/DanlyIEM-JIS-Springs.pdf

Do the springs absolutely need to be 40mm in length?

What is the maximum compressed length to allow closure of the trunk? The compressed lengths may vary based on color of the spring since the coils have different thickness.

It looks like the 18mm outer diameter springs may even work since the inner diameter of those springs are 9mm, but you would definitely need to get a green spring for more "power".

I ordered the 18mm x 40mm green springs. Hopefully we'll be able to figure out which one works best.
 
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#11
I installed the recommended 4129 StrongArm + Red 40mm springs + washer combination and have had less than stellar luck. It opened great the first few times, but lately only opens about 6 inches (when the wife is watching) and hangs there. Thinking WD40/White Lithium (on the hinges, not struts) or another set of washers might help, but wondering if anyone else isn't having as much luck with the recommended combination.

Temperature not an issue with the gas struts as it's been 70F for a few days now.
 
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modelo tres

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#12
Try more washers? I ordered the "stronger" green springs. Hopefully it'll be here soon. Already got the struts quickly from RockAuto
 

radlaw

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#13
Ordered the struts, springs & washers. Washers came, all 200 of them. Thought I was ordering 2; turns out it was 2 bags of 100 each. I thought they seemed a little expensive! Moral of the experience: read the damn instructions. I'd give them away but mailing them will cost more than 2 washers. If you'r in San Diego, come by and I'll give you up to 198 washers.
 
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#14
I'm thinking I may have gotten a bad set of struts. They won't even lift the trunk if I manually open it halfway now. Had bought them from RockAuto.

Edit: Saw someone with similar issues on Facebook that bought two sets of struts. The ones made in Turkey do not work—Open 1/4 of the way or worse. The ones made in the USA do work. Have to check the label on the strut to confirm.

Will be returning / ordering new struts.
 
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bobjouy

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#16
I'm thinking I may have gotten a bad set of struts. They won't even lift the trunk if I manually open it halfway now. Had bought them from RockAuto.

Edit: Saw someone with similar issues on Facebook that bought two sets of struts. The ones made in Turkey do not work—Open 1/4 of the way or worse. The ones made in the USA do work. Have to check the label on the strut to confirm.

Will be returning / ordering new struts.
Would you mind taking a picture for us?
I've received 2 struts from RockAuto, but they are not 100% similar. Both are Strongarm 4129, but not the same exact label/length etc.
I wonder if I should order some new ones (car will be there in 3-4 weeks).

Thanks!
 

Djgabriel2004

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#17
"Agree that Autoclose would be awesome, but there will be no way to make that work without crazy hacks and other mechanisms (Raspberry Pi with cell radio, controlling pnumatic system?!?)."

what about a Raspberry pi and 12v linear actuator? Maybe the raspberry P can "catch" the signal sent to the actual trunk lock from the app. and keep the circuit open for a few seconds until it close. or catch the "Stop signal" when the trunk light turn off.
I think the electronics won't be to hard to do, the main thing should be to put a linear actuator in some place to make it works.
 

Craig Bennett

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#18
I tried the Boxi lifts, 20MM OD red springs, no washers. The trunk opens faster and bounces at the top UNLIKE the demo in i1Telsa's video. I'm assuming it's a dampening difference in the lift since the spring is there just to provide sufficient impetus to start the trunk opening.

But I'm not an engineer so that's pure speculation on my part. The Strongarm's are on order but will take a few weeks to arrive.
 

bobjouy

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#19
Would you mind taking a picture for us?
I've received 2 struts from RockAuto, but they are not 100% similar. Both are Strongarm 4129, but not the same exact label/length etc.
I wonder if I should order some new ones (car will be there in 3-4 weeks).

Thanks!
Here are the 2 I have.

One made in USA, one made in Turkey.


Do you guys think I should order one (or 2 ?) new made in USA struts? Or will I be fine with those?

Thanks!
 
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#20
Indeed, my turkey strut looked like the one in your photo.

Do not mismatch the struts as if it opens it will open unevenly, potentially damaging your paint or worse.

Attached is how far my turkey struts open when they start to fail. Before I removed them it might have opened half an inch or less.
 

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