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So I have had the Skunk2 Intake Manifold since it first came out. Immediately after installing it I could feel substantial amount of vibration through the throttle pedal at high RPM. This is on a dedicated road car so it sees a lot of sustained high revs.
The first race weekend the throttle cable popped out of the throttle cable bracket. Had to get towed off track. So I ziptied the throttle cable to the bracket and manifold. A few track days later the throttle cable broke in half. Had to get towed off track. So I redrilled new holes in the throttle cable and put it back on. Eventually the bracket broke again resulting in another tow off track and more missed races so I welded up a new one from scratch that was unbreakable.
The new monster bracket lasted a year until a race this past weekend and the actual throttle ripped apart. Not the screws on the butterfly but the metal that guides the cable onto the throttle ripped off.
In my opinion the lack of an intake manifold brace on the skunk2 manifold is a design flaw.
Now I need to decide whether to try and modify the skunk2 to accept a brace or pull it off and go to a squaretop.
Pics of the most recent damage. Note where the cable attaches to the throttle some of the metal that would normally guide it is gone:
If I were already invested in the S2 IM, I would likely stay the path and mod it while being severely aggravated. I am also quite pleased with the performance of my squaretop that’s obviously well documented across the MT world but planning on the Skunk2 TB swap (and bigger IC) before spring rolls around due to my fears you noted around the butterfly.
The brace would do nothing with his failure. The manifold brace keeps the intake runners from cracking. His failure was due to improper cable tension so when he crams his heavy foot on the go pedal it torques the **** out of the bracket and wears on the throttle guide to the point where it broke.
^ I concur, seems like the pedal travel goes further than there is slack and travel in the throttle cable resulting in torque on the throttle body shaft and terminal fatigue. How would one check tension pressure when fully depressed? I suppose have someone hold the throttle 100% open and push the pedal down and check for slack at the end as you approach full travel..
I absolutely agree. I have no experience operating at those leves but I know it's a much larger amount of stress on a lot of different systems... I just doubt the stock IM brace really helps prevent any failures. Certainly not throttle cable.
But I've been wrong before, especially if my wife is around...
I absolutely agree. I have no experience operating at those leves but I know it's a much larger amount of stress on a lot of different systems... I just doubt the stock IM brace really helps prevent any failures. Certainly not throttle cable.
But I've been wrong before, especially if my wife is around...
(And I am kinda AssUMe-ing here too)
There is a group of miata owners and drivers out there that believe the IM brace is absolutely critical. There is a ton of overlap with spec miata drivers. I have not had a brace on any of my cars since I do the first oil change. I have never had issues. I have also not personally met anyone who has had a failure due to no brace. Every once and a while I meet someone who has heard of someone, from one of their friends that has had a failure. So I don't know if it is a real issue or not, but I then to thing no. Even if it is a problem I agree there is zero reasons it would have anything to do with the throttle cable having problems, shot of manifold barely hanging onto the head.
What throttle cable was the OP using? NA or NB? I know there is a difference and it is recommended to upgrade to the NB cable when you do a NB motor swap. It could be that Skunk2 IM is setup for one cable over another.
I just reinstalled my IM brace recently.
I am hanging a chunk of metal the size of a wrecked VW on the exhaust side - two turbos and all associated bulk... I have braced the cantilevered mass as best as I can, but I was getting strange harmonics at certain rpms before I carefully tuned the said braces by fiddling with preload on them.
The decision to reinstall the IM brace was motivated by eliminating all possible culprits for such harmonics, because the IM is another chunk of metal that is cantilevered off the side.
My engine is running smooth at the moment.
Last edited by Godless Commie; 03-03-2020 at 05:06 AM.
Reason: spelink
I have the same vibration in my pedal above 5k rpm. I assumed that it was from the Skunk 2 sitting lower on the engine than the stock intake. My cable is adjusted properly (with a little slack) When I first experienced the vibration it was pretty worrisome because the Skunk 2 was part of a new engine install and I worried that the vibration was an engine problem and not an intake manifold/cable problem. Since then, I've taken care to isolate the throttle cable from the car except at the bracket on the Skunk and where it passes thru the firewall. Silicone rubber hoses and zip ties keep it from laying on the manifold or engine. the vibration is reduced but not eliminated. The bolts in the throttle body actually vibrated out of my manifold and 2 of them were lost. I had to limp home with a major vacuum leak. The new bolts have been Loctited in place ( I should have done that the first time).
the other issue with the Skunk is the throttle plate (butterfly) not returning to idle. I added an additional spring which has worked really well. Others have drilled alternative holes in the throttle plate bracket to add more tension to the coiled spring.
The Skunk idles MUCH better than my factory '03 manifold and throttle body. Hard to say if there was an increase in power since the new motor is at 15 psi and the previous one was at 12psi.
Im willing to bet this is a user error and your cable tension was too tight.
It's an interesting theory and I can see the logic. I am also not above occasionally making bonehead mistakes.
I bought another stock throttle and bolted it on. At WOT the cable doesn't look like it would be putting much tension on the part of the throttle that broke. See the attached pic.
Also I shot a video of the slack on the throttle cable. First at the adjustment setting the throttle cable was attached to previously and secondarily at the setting that is required to not max out the throttle. As you can see even on my previous adjustment setting it had a good amount of slack. However at the previous adjustment setting it definitely would have had a lot of tension on the cable at WOT. Perhaps the angle/height the throttle is mounted with the skunk2 changes something in the geometry and more slack is required?
I have the same vibration in my pedal above 5k rpm.
Good to hear I'm not totally crazy. I know when I first assembled mine I was taken back by how much vibration I could feel. It was like my foot was pressing up on a vibrator.
Maybe something in the geometry of the throttle arrangement is different and the tension on the cable is too high resulting in the cable transferring vibration to your foot?
For absolute certainty that user error doesn't cause the issue, set your TPS range by hand (hold the throttle open by hand at the throttle body), then set the cable housing adjustment and pedal adjustments such that WOT at the pedal equals ~98.5% TPS.
If you think the OEM throttle brace does nothing, I'll have a boat anchor of a lower squaretop manifold that will convince you otherwise.
Good to hear I'm not totally crazy. I know when I first assembled mine I was taken back by how much vibration I could feel. It was like my foot was pressing up on a vibrator.
Maybe something in the geometry of the throttle arrangement is different and the tension on the cable is too high resulting in the cable transferring vibration to your foot?
Like I said, I was able to minimize it but it's not gone. It definitively is not from too much tension on the cable. I made mine as slack as possible while still being able to open the throttle completely. My throttle body has a different "round cable guide thingy" than yours. Mine is one piece billet aluminum looking. Maybe because of failures like yours they changed it. Call Skunk and ask if they can send you a newer type? I'm not home so I can't take a pic right now. Let me know if you need a photo of it.
I have the same vibration in my pedal above 5k rpm. I assumed that it was from the Skunk 2 sitting lower on the engine than the stock intake. My cable is adjusted properly (with a little slack) When I first experienced the vibration it was pretty worrisome because the Skunk 2 was part of a new engine install and I worried that the vibration was an engine problem and not an intake manifold/cable problem. Since then, I've taken care to isolate the throttle cable from the car except at the bracket on the Skunk and where it passes thru the firewall. Silicone rubber hoses and zip ties keep it from laying on the manifold or engine. the vibration is reduced but not eliminated. The bolts in the throttle body actually vibrated out of my manifold and 2 of them were lost. I had to limp home with a major vacuum leak. The new bolts have been Loctited in place ( I should have done that the first time).
the other issue with the Skunk is the throttle plate (butterfly) not returning to idle. I added an additional spring which has worked really well. Others have drilled alternative holes in the throttle plate bracket to add more tension to the coiled spring.
The Skunk idles MUCH better than my factory '03 manifold and throttle body. Hard to say if there was an increase in power since the new motor is at 15 psi and the previous one was at 12psi.
Paul
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Has anyone else had the issue of pedal vibration at 5k and above? i presently have the same issue and I have been trying to find a way to fix it too. Did you find a solution to stop the buzzing?
I have also isolated it to my skunk 2 throttle body.
10-28-2019, 06:53 PM
Problems with Skunk2 Intake Manifold
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