IIRC, scorp965 also had this happen to his.
If I weren't removing my VVIS for boost, I would put some tack welds on those screws.
Dave
If I weren't removing my VVIS for boost, I would put some tack welds on those screws.
Dave
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SCREWED! The Tale of my "Rebuild" (long winded, sorry slow day at work)
- Thread starter LDominicano
- Start date
Grabbed my intake (1991 with 30-something-k miles) from the attic and cracked it open. I figured if I were to ever put it back on I'd want to crack it open anyway to make sure these were OK and no debris had fallen inside during storage. So, here are pics of what things should look like (nothing loose here).
First observation is that the end of the screw is hollow to make the walls weak enough to easily distort out when the edge of the screw is punched. It does look like each screw is hit with two small round punches (one on each wall across from each other). One theory on the failed units would be that too much of the material distorts toward the middle of the screw (maybe punch occurred too close to the outside of the wall) instead of out, so not effective at keeping the screw from backing out. Maybe because of not enough material protruding past the rod, maybe because not hit with sufficient force, maybe because alignment of punches is off, maybe there was a batch of butterflies thicker than the others (I'll take a caliper to mine if people want to compare thicknesses). See the first and third pictures
One thing to note that may be helpful for people wanting to investigate via scope is that the crease at the end of the screw is always perfectly perpendicular to the rod the butterfly is attached to. So, if you see one that is not perpendicular, it has moved. See the second and third picture.
First observation is that the end of the screw is hollow to make the walls weak enough to easily distort out when the edge of the screw is punched. It does look like each screw is hit with two small round punches (one on each wall across from each other). One theory on the failed units would be that too much of the material distorts toward the middle of the screw (maybe punch occurred too close to the outside of the wall) instead of out, so not effective at keeping the screw from backing out. Maybe because of not enough material protruding past the rod, maybe because not hit with sufficient force, maybe because alignment of punches is off, maybe there was a batch of butterflies thicker than the others (I'll take a caliper to mine if people want to compare thicknesses). See the first and third pictures
One thing to note that may be helpful for people wanting to investigate via scope is that the crease at the end of the screw is always perfectly perpendicular to the rod the butterfly is attached to. So, if you see one that is not perpendicular, it has moved. See the second and third picture.
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wow...... talk about feeling uneasy. I have a 96 with a moderate amount of miles. Should I yank it right away?
Other thing that strikes me is how failure from this seems to be a perfect storm of events. Most of the time if a screw comes out I bet it just falls into the plenum (where it would harmlessly remain unless car/engine is flipped over). The only way to get into the engine is for the butterflies to be closed (off/partial throttle?) and turning or breaking hard to get the screw off of the butterfly before it opens again...and then it has to rattle/roll around into one of the intake ports without first rattle/rolling safely into the plenum. My pictures don't show it, but the butterflies are at about a 30-degree angle when closed (along with surrounds they slope toward middle) so things would roll away from intake ports. So if we're seeing a few engine failures from this, I bet there are A LOT of screws out there in the process of backing out or already laying in the plenum.
Edited to add pictures of the top-side of the VVIS to illustrate (pics posted by others are of bottom)...
Edited to add pictures of the top-side of the VVIS to illustrate (pics posted by others are of bottom)...
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What year was his car?
Latzke - great pics. interesting to see that the factory did put some semi-permanent measures in place to prevent the screws from coming lose. Those stamped ends look like a PITA to remove. Perhaps there were some that weren't stamped properly thru the production line.
I'm glad I took mine off. Such a small problem can create a catastrophic failure.
Tack welding them with a tig is not a bad idea either. Personally, i'd just take them off. If I wanted to do it on the cheap I'd remove just the butterflies.
I'm glad I took mine off. Such a small problem can create a catastrophic failure.
Tack welding them with a tig is not a bad idea either. Personally, i'd just take them off. If I wanted to do it on the cheap I'd remove just the butterflies.
He's boosted so he can free up 1, maybe 2 hp
Peace of Mind
over
Power
This chart is for NA vehicle if im not mistaken, from what ive read, iirc forced injected application benefit on all scenarios with them removed.
Im got this graph in the back of my head now cause im NA for the time being and i can help but to wonder if the mid range is going to be noticably sucky without the butterflies in there.
Ive already removed them all but am still getting the motor back together...
sigh :frown: ...x
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FYI for those opting to remove it, buying the delete kit from SOS to delete the entire VVIS plate is technically less expensive than buying the 2 gaskets. You will have to plug the vacuum line (I'm assuming the plug is part of the kit).
I'm not sure what removing the entire plate vs just removing the butterflies will do on the dyno.
I'm not sure what removing the entire plate vs just removing the butterflies will do on the dyno.
I've asked this here: http://nsxprime.com/forum/showthread.php?t=154928
but really should address it here. By removing the entire VVIS assm, can a plenum spacer in place pick up some lost torque on an NA car?
but really should address it here. By removing the entire VVIS assm, can a plenum spacer in place pick up some lost torque on an NA car?
I think everyone needs to take a deep breath. With 10,000 cars or so in the US, only a handful have experienced VVIS screws loosening. Perhaps inspection can be part of a major service but having everyone tearing into the top end of their motors poses another set of risks.
I'd like to see what Chris, Nabil, Nigel, Larry B and other trained experts have to say on this matter.
I'd like to see what Chris, Nabil, Nigel, Larry B and other trained experts have to say on this matter.
- Joined
- 31 December 2010
- Messages
- 309
No need to rip apart the intake. A generic 18" or longer borescope will work fine for inspection, no special mirrors or attachments are needed. I have a cheap fiber optic one, however I'm going to order an even cheaper $20 USB one off ebay to see if that will be just as good.
Attached are photos, I know they are horrible but with a little patience you can see both sides of the plates clearly. In all it took me 20 minutes to inspect all 6 plates. My screws seem to be fine, but my borescope didn't have enough resolution to see how pronounced the swage was.
I took a couple photos from my cell phone, so it's not good quality at all, but you get the idea.
Left is a distant shot, right image is seriously "up close and personal" to the screw.
Attached are photos, I know they are horrible but with a little patience you can see both sides of the plates clearly. In all it took me 20 minutes to inspect all 6 plates. My screws seem to be fine, but my borescope didn't have enough resolution to see how pronounced the swage was.
I took a couple photos from my cell phone, so it's not good quality at all, but you get the idea.
Left is a distant shot, right image is seriously "up close and personal" to the screw.
Attachments
That is great! I take it you left the throttle body in place?
- Joined
- 31 December 2010
- Messages
- 309
Yep, I just propped open the throttle plate. The 20 minutes included removing the stock airbox. It's a straight shot from the throttle plate to the VVIS plates. In fact if you have a mirror, powerful flashlight, and good pair of eyes you can see the plates and screws if they aren't covered in carbon/oil already.
Years ago, my car made a strange rattling noise from the engine compartment when the engine was slowing down after blipping the throttle. If I remember correctly, it sounded kind of like lost motion assemblies going bad. My mechanic looked over the engine and said it was something the VVIS system. He said it was an easy fix and after the car came back from the shop, the rattle was gone. I never asked exactly what he did but after reading this thread I have a suspicion.
If you look at the chart just above your post, the red line shows the effect of removing the VVIS valves and horizontal sheet around the valves from the intake manifold, leaving just the outer walls of the VVIS system in place. In effect, that is the same thing as removing the entire VVIS system and installing a spacer like STMPO’s in the plenum.
If you look at the chart just above your post, the red line shows the effect of removing the VVIS valves and horizontal sheet around the valves from the intake manifold, leaving just the outer walls of the VVIS system in place. In effect, that is the same thing as removing the entire VVIS system and installing a spacer like STMPO’s in the plenum.
Guys, guys I went to the garage and checked the tire pressure on my tires... one was low, so I took it to a tire place and they said there was a nail in it... in a couple of days it would have gone flat.
You all should go out to the garage right away and remove all the tires from your cars and have them checked for nails otherwise one might go flat when you're driving fast and cause a serious accident in which several people could be killed.
Just sayin'
You all should go out to the garage right away and remove all the tires from your cars and have them checked for nails otherwise one might go flat when you're driving fast and cause a serious accident in which several people could be killed.
Just sayin'
Cody from Lovefab ingested a screw also on his 95.
I guess this is something for us to put on the to do list, like changing the harmonic balancer, at least once for peace of mind. It sure beats having a loose screw in your head. :wink:
Just called my local harbour freight, they have the digital inspection
Camera in stock. I'm convinced a $90 dollar camera is good insurance on a $5k motor...
Any Nsx owners in the DMV want to check their motors PM me..I should have it by tonight.
And if the resolution is no Bueno..thank god for receipts!
Camera in stock. I'm convinced a $90 dollar camera is good insurance on a $5k motor...
Any Nsx owners in the DMV want to check their motors PM me..I should have it by tonight.
And if the resolution is no Bueno..thank god for receipts!
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