When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
FYI the alias Junk2 for the Skunk2 throttle body is correct
FYI the alias Junk2 for the Skunk2 throttle body is correct.
One crowning item in a very expensive Testing & Time Trial race weekend. I was hoping to lower my current Sebring Miata Track Record, as Friday I didn't have to run my 270 hp TT3 tune.
On the 2nd hot lap 2nd session of the day, very quickly hustling through Big Bend shifting into 4th. Lost throttle control, making no power but engine stuck at free surging between 2K & 6K. Big bend with 245 Hoosiers in a quick turbo car & no power steering is a workout as is.
Pulled off track by turn 6 flag stand and got an embarrassing hot tow back to my pit. Thinking I broke a throttle cable? Nope........
NOTE 1: Sebring workers do a "Fantastic Job" quickly hot towing and clearing the track, but still sorry about costing some fellow testing & track rats lap times due to my ill timed yellow flag.
As soon as I lifted the hood it was obvious. The Skunk/Junk 2 throttle body shaft had snapped where it is sharply machined to a reduced diameter. Machining and design best practice would have a radius at transition step. Any truth to the Ebay knockoffs being better built????
Granted this is an 8K revving EFR turbo NB2 with the associated vibration.
Thinking my very very expensive NASA Winterfest weekend was over i discovered the best part of racing. The people.
NOTE 2: Enter endurance racing (winning) and parts supplier, Late to Apex Performance & Design LLC.
Dan and especially his wife were kind enough to grab his personal spare from the garage and drive an hour and a half in the dark early morning fog to get me up and running 1st thing in the morning. It was un-modified so the throttle blade was a sticking mess, but it got me on track.
Just a reminder to always have an already modified spare Skunk throttle body on hand.
That sucks! But glad you were able to get going again, and no major harm caused to you or others.
I do notice you don’t seem to have the intake manifold brace installed. Not sure about the S2s but having the brace installed seems key to keeping the stock throttles in one piece, especially track motors that live in the upper rpm ranges, and/or beyond stock redline. Might help the S2 issues as well.
That said, I don’t know anyone using a genuine Skunk2 unit, since the eBay ones are known to be as bad or better for like 1/4 the price.
I mean no offense and I've got to ask, so be honest with me here:
Did you set the pedal stop in the car to stop pulling on the cable right at 100% TPS? I.E. so that slamming on the pedal results in the pedal doing most of the stopping, not the "stop" on the TB.
Hope that makes sense. I only ask because I don't see that discussed very often, and I do think it's important for longevity of any TB.
Not at all disputing that they are indeed junk, but at least this failure mode is external and didn't take out a motor...
I have used a succession of the S2 tbs, no problems on racecar (8k+ rpm BP), atmo BP, turbo BP (current), this after breaking a succession of stock TB shafts (slow learner ). They were all prepped according to the recipe on here though, for truly the S2 is really the J2, and all were 'genuine' S2s, and I am careful about the pedal stop position. I have never heard of a broken shaft on an S2, AIRI it is not mentioned in the S2 threads.
FWIW I have not run the IM brace either, even on the 8k rpm racecar, and am a skeptic on that theory, but others have different views and apart from access issues it can't hurt.
I don't run the long intake manifold brace, but I do usually try to run the smaller one, that specifically braces the throttle body. You might try adding that.
What was the age of the S2? Sebring+lots of hours...I'm not surprised if it breaks. There's safety wire, zip ties, and torque paint on your throttle body for a reason.
I do notice you don’t seem to have the intake manifold brace installed. Not sure about the S2s but having the brace installed seems key to keeping the stock throttles in one piece, especially track motors that live in the upper rpm ranges, and/or beyond stock redline. Might help the S2 issues as well. That said, I don’t know anyone using a genuine Skunk2 unit, since the eBay ones are known to be as bad or better for like 1/4 the price.
No I do not have the intake brace installed, running a larger filter with adapter and #10 oil cooler lines coming off it. Thinking about ordering 2 of the EBay ones to try out.
Originally Posted by Fireindc
I mean no offense and I've got to ask, so be honest with me here: Did you set the pedal stop in the car to stop pulling on the cable right at 100% TPS? I.E. so that slamming on the pedal results in the pedal doing most of the stopping, not the "stop" on the TB. Hope that makes sense. I only ask because I don't see that discussed very often, and I do think it's important for longevity of any TB. Not at all disputing that they are indeed junk, but at least this failure mode is external and didn't take out a motor...
Makes perfect sense, and yes it was correctly adjusted to take up 100% with just a bit of cable tension at the end of stroke.
Originally Posted by curly
I don't run the long intake manifold brace, but I do usually try to run the smaller one, that specifically braces the throttle body. You might try adding that. What was the age of the S2? Sebring+lots of hours...I'm not surprised if it breaks. There's safety wire, zip ties, and torque paint on your throttle body for a reason.
The top little brace is a very good idea. Thinking of fabricating up a large brace that will clear all the oiling items. The S2 had some time on it, and this is a motor with a lightened crank, Supermiata twin clutch and has some harmonics at 8K even with the ATI damper. Safety wire and torque putty because aircraft mechanic, zip tie because I'm to lazy to re-pin connector.
No I do not have the intake brace installed, running a larger filter with adapter and #10 oil cooler lines coming off it. Thinking about ordering 2 of the EBay ones to try out.
You can notch the brace to fit this configuration. I had to do it for my build. It does make removing the filter a little more difficult, but mine is a race car, so removing the 3 bolts holding the brace in place isn't a big deal to me.
Agreed with the other comments in here about throttle stops and intake manifold bracing. They may not have prevented the failure but it's best practice for sure. I'm at 35,000 miles (not sure on track hours) on my Skunk2, but it's a stock 7,200 rpm NA engine. Not exactly the hardest use case out there. I'd been carrying the stock TB with me to the track and on longer road trips as a spare, but have since stopped. Maybe this is the reminder I need to start doing that again.
When I had an oil cooler installed I notched the brace to clear the filter. All the fore-aft webbing is gone, but it should still provide a good amount of vibration relief just from not being cantilevered out there. For the throttle adjustment, I found that the stock throttle stop that's built into the pedal assembly was too flexible to actually prevent a heavy foot from putting tension on the throttle shaft itself. Even the amount of pressure easily applied with two fingers was enough to bend the stop and take up a lot of the slack I had left on the cable at WOT. I recommend a hard stop in the floorpan as the easiest solution to prevent loading the throttle body with a heavy foot.
Here's a shameless plug for my condensed thread where I did every fix to the Junk2 I could find documented, some of my own ideas, and put it all in one place.
FYI the alias Junk2 for the Skunk2 throttle body is correct
0
). They were all prepped according to the recipe on here though, for truly the S2 is really the J2, and all were 'genuine' S2s, and I am careful about the pedal stop position. I have never heard of a broken shaft on an S2, AIRI it is not mentioned in the S2 threads.
