Skunk2 Pro throttle body issues

[david_syd_au]

Just a heads up to all those using or considering using a Skunk2 Pro throttle body on their MX-5

I put a new Skunk2 TB (part # 309-10-0200) in my NB8A race car about 2 years ago, not for performance but because I considered it a good idea to replace the standard TB due to their reputation of falling apart and causing engine damage when used for motor sport with regularly high engine RPMs.

During the 2nd MX-5 Cup race at Wakefield Park a few weeks ago, the throttle cable pulley on my Skunk2 TB became detached from the TB, allowing the throttle return spring and a bush to escape. I later managed to recover the bush but not the return spring. The mostly likely cause was that the nut holding on the pulley worked it's way loose, despite being locktited from the factory.

There were 2 consequences of this failure:
1. With the main return spring gone, and the throttle at maximum at that point, it seems the secondary return spring in the TB was not able to close the butterfly, and the engine was stuck at WOT. Fortunately I was able to shut down the engine and get off the track with no further issues. Damn I hate DNFs!
2. I have contacted Skunk in the USA to obtain a replacement spring. They said that they would try to find a returned TB to disassemble to provide a spring, and after a few follow-ups advised that no suitable TB was available for parts, and so they could not supply the spring.

So, my 3 thoughts are:
1. If you use a Skunk2 Pro TB on your MX-5, add checking of the throttle pulley nut to your periodic maintenance,
2. Consider adding a 3rd external return spring to ensure the TB will close at WOT in case the main spring is broken or lost, and
3. if you are thinking of buying a Skunk2 Pro TB, parts may not be available, so you should factor that into your decision.

For now, I plan to visit a wreckers and try to find a suitable replacement spring. If that doesn't work, does anyone know of any other manufacturers who make MX-5 s TBs which are more reliable for motor sport use than either the stock TB or Skunk2 Pro TB?

[Lokiel]

It's a common recommendation to Loctite everything on the Skunk2s - search MT.net and you'll find several threads dedicated to the Skunk2.

TSE and 949racing have been talking about making a decent TB for a while now but don't hold your breath.

It sucks that they can't even be bothered sending you a replacement spring (that's what I read between the lines) but it doesn't surprise me given their reputation.

- I too have a Skunk2 and have taken precautions.

[16bit]

949 are claiming a 2017 solution.

i have hard of 70mm ls throttle bodies being used but can't guarantee that.

also this, not sure if it fits up stock though. doesn't look like its stock fitment.

http://www.bellengineering.net/product_ ... cts_id=540

[sailaholic]

I belive jenvy make a throttle body that is more reliable but they only seem to sell them in a set of 4 labeled as an "ITB KIT" or something?

Magpie can probably comment better.


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[madjak]

I used to run a skunk2 honda TB and it useless. Not only did I have issues with the TPS drive plate coming loose from the shaft, but also the throttle plate itself being loose in the bore so my idle would vary. Also the throttle return spring was never quite strong enough.

To be clear this is the 70mm Honda not the Mx5 one but I think most of the issues apply across the entire range. S2's QA and design skills are lacking big time!

I have since switched to a S90 70mm throttle body and it is awesome. S90 make some really nice gear and it would be well worth making an adapter plate to fit them to our stock manifolds.

[greenMachine]

I believe there is a Ford TB that the yanks use, maybe search on Mnet or MTnet ... iirc the discussions were FI related.

I have had two TB failures, both broken shafts. As a result I have made a ghetto fix to my new TB (stock), involving an angle grinder to remove the twisting that breaks them so I hopefully will not have any more TB problems.

[Magpie]

Magpie can probably comment better.

Happy to http://www.jenvey.co.uk/products2/large-single-throttle-body/single-body-70mm-sfg70-0

[zossy1]

I believe there is a Ford TB that the yanks use, maybe search on Mnet or MTnet ... iirc the discussions were FI related.

I have had two TB failures, both broken shafts. As a result I have made a ghetto fix to my new TB (stock), involving an angle grinder to remove the twisting that breaks them so I hopefully will not have any more TB problems.

It is the 70mm Ford Mustang TB - can be made to fit with some modification to the manifold.

That's a lot of TB for an aspirated MX5 but Rick's seems to work ok!

[StillIC]

Years ago I read an article in a UK magazine 'Cars and Car Conversions' about a 'modified hatch' race car. It was a 1.6 Peugeot 205 (no, not the 1.9) that was extensively modified, but was forced to use the standard intake manifold. It made 170hp at the flywheel. The owners had put a lot of work into the TB, which could be modified under the rules, to ensure that there was no restriction to flow into the manifold, affecting horsepower. The article said "it was surprisingly big" without stating a number. So I got out my calipers to try to estimate the size of the TB based on the scale/size of other items in the photo and estimated it to be 70mm.

[madjak]

That's a lot of TB for an aspirated MX5 but Rick's seems to work ok!

Yeah 70mm is big. A lot of the N/A drag Hondas run a 90mm... but they only need on and off!

S90 do make a 58mm throttle body for a Honda Fit. Someone (not me) needs to buy one and fit it up to a MX5. I think it would be perfect.

[greenMachine]

I have decided I am just over busted TBs . Found another yesterday, that makes at least three, the screw is gone, hopefully without trace.

A Skunk appears to be the solution, although MT.net suggests there are cheapo Skunk copies on the market I might let others pioneer them. Where do people get their Skunks - locally? I see GWR and 949 carry them, amongst others ...

[Nevyn72]

Why not get the 'kit'?

https://miataroadster.com/skunk2-ultra- ... 70037.aspx
+
http://miataroadster.com/skunk2-proseri ... 42473.aspx
+
https://miataroadster.com/miataroadster ... 07722.aspx

[Magpie]

Magpie can probably comment better.

No comment, I would listen to Madjak on this issue

[Lokiel]

Keep tabs on the following threads:
https://www.miataturbo.net/engine-performance-56/china-64mm-tb-knock-off-94579/
https://www.miataturbo.net/engine-performance-56/new-miata-junk-2-intake-94571/

The Chinese knock-off TB appears to be the same as the genuine Skunk2 TB and is much cheaper.
Both TBs need some minor tweaks before installation.

The Skunk2 intake manifold looks like a great alternative to the Flat-Top manifold (MT.net members may be doing comparisons on these in future).

[NitroDann]

I once tried to tune a car with a knockoff skunk throttle body and outside of generally poor finishing and a throttle plate that didn't fit or seal properly the idle air control valve passages were just completely wrong and required extensive modification to get the car to be able to idle properly.

Dann