Jump to content

Photo

1.6 Throttle Body Butterfly Valve

- - - - -

  • Please log in to reply
6 replies to this topic

#1
Justin Casey

Justin Casey

    Member

  • Members
  • PipPipPip
  • 45 posts
  • Location:San Jose, CA
  • Region:Northern California
  • Car Year:2001
  • Car Number:85
Just had mine break at Thunderhill today. Luckily the two screws are both still in the shaft itself and not somewhere within the engine.

I am curious to see how many others have had this issue. Please comment if you had this issue and/or have any insight on how to further prevent this from happening again.

I have heard a few people putting epoxy on the shaft but I don't quite think that'd be legal...

TIA

- Justin

2018 NASA NorCal Regional Champion

2018 SCCA Runoffs - 4th Place

2018 NASA Championships - 5th Place

2017 NASA Western States Championships - 4th place
2017 NASA Northern California Region - 2nd place
2016 NASA Western States Championships - 2nd place
2016 NASA NorCal Regiaon Champion

Series Champ - Won a points based series in a Spec Miata We have a Winnah! - Won their 1st race... Congratulations! Bona fide - A bonafide Spec Miata driver

#2
chris haldeman

chris haldeman

    Veteran Member

  • Members
  • PipPipPipPipPip
  • 928 posts
  • Location:Mckinney
  • Region:texas
  • Car Year:1999
  • Car Number:73
Increase throttle cable slack and or install a pedal stop between the floor and pedal allowing only full throttle. What happens is the blades open all the way long before the pedal stops moving and you basically rip the shaft
  • Alberto and Jim Drago like this
X-factorracing.com
3 podium finishes
2 2013 NASA nats
1 2013 Scca runoffs
Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver BFG Supertour Winner - Circuit of the Americas Winner - Majors Winner - Make it Rain - Made Paypal donation of $100+ We have a Winnah! - Won their 1st race... Congratulations!

#3
Justin Casey

Justin Casey

    Member

  • Members
  • PipPipPip
  • 45 posts
  • Location:San Jose, CA
  • Region:Northern California
  • Car Year:2001
  • Car Number:85

Increase throttle cable slack and or install a pedal stop between the floor and pedal allowing only full throttle. What happens is the blades open all the way long before the pedal stops moving and you basically rip the shaft

 

I'll definitely incorporate that when installing the new throttle body assembly.

 

Thanks.


2018 NASA NorCal Regional Champion

2018 SCCA Runoffs - 4th Place

2018 NASA Championships - 5th Place

2017 NASA Western States Championships - 4th place
2017 NASA Northern California Region - 2nd place
2016 NASA Western States Championships - 2nd place
2016 NASA NorCal Regiaon Champion

Series Champ - Won a points based series in a Spec Miata We have a Winnah! - Won their 1st race... Congratulations! Bona fide - A bonafide Spec Miata driver

#4
Bench Racer

Bench Racer

    Different strokes for different folks : )

  • Members
  • PipPipPipPipPip
  • 5,508 posts
  • Location:Wauwatosa, WI
  • Region:Milwaukee
  • Car Year:1990
  • Car Number:14

Here's a bit more info and not pissing on anything Chris stated. Chris is spot on with the floor pedal stop. 

 

Don't cheat and remove the aluminum arm that supports the intake manifold to the engine and don't remove the steel bracket that supports the backside of the intake manifold square surface the throttle body mounts to. Also remember the gasket between the throttle body and intake manifold is not specified within the rules, think thicker vibration absorbent gasket material.  

 

For a production car one may be more creative towards eliminating the vibration at the throttle body because the rules are less restrictive. When these same engines/throttle body/butterfly and shaft are used in the production class cars with engine rpm's of 8,000 plus a bit it is believed the engine harmonics breaks the shafts. They use two process to get around the issue. Weld the shaft/butterfly which is illegal by rule, weld or braze the screws to shaft is rule legal and there are units where the butterfly is secured to a special shaft (EDM'ed slot in shaft) with epoxy which is legal. I've viewed both shaft welded and shaft epoxy unites brake. 


Broken record - You are starting to sound like a broken record. Donor - Made PayPal donation Bona fide - A bonafide Spec Miata driver

#5
cam

cam

    Member

  • Members
  • PipPipPip
  • 69 posts
  • Location:Texas
  • Region:SOW
  • Car Year:1990
  • Car Number:14

Adding another data point, I've had multiple throttle shafts snap over the years in my 1.6.  While a more relaxed throttle cable helps, that is just part of the problem.  Bench is on the right path, the harmonics really play havoc with the throttle shaft.  IMHO, keeping the manifold brace helps.  But I would be VERY wary of using the thick intake gasket.  It is my empirical evidence that the thick isolated style of gasket caused more problems than it solves.  In my case on my now STL 1.6, studs sheared off and caused a lean condition when the manifold created a leak.

 

When I get my car running again, I'll epoxy the shaft to retain the bolts.


  • Todd Green likes this
Bona fide - A bonafide Spec Miata driver

#6
obxer

obxer

    Junior Member

  • Members
  • Pip
  • 9 posts
  • Location:Nags Head, NC

A bit late to reply, but our experience was a bit different regarding this problem. I run a 1.6 in ITA with a megasquirt. So I redline a good bit higher than stock. We broke 3 or 4 butterfly shafts in quick succession with one breaking only about 30 minutes after changing it. After the first break we thought maybe we were over-torquing the shaft at WOT by not having the pedal stop adjusted correctly. So we adjusted the pedal stop so the butterfly was just barely to the WOT stop when we stood on the pedal. After this we quickly broke another. The looser we made the cable at WOT the faster they broke. We finally wised up and figured the less the cable was tensioned at WOT the more the butterfly could vibrate/flutter. So after the 3rd or fourth one broke really quickly we adjusted so the cable was tight at WOT - putting a little tension on the shaft at WOT. Since then, we haven't had one break in well over a year.



#7
Steve Scheifler

Steve Scheifler

    Veteran Member

  • Members
  • PipPipPipPipPip
  • 2,816 posts

Interesting, thanks!
Instigator - Made a topic or post that inspired other Broken record - You are starting to sound like a broken record.




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users