Snapped another throttle body - SR20DET - PICS

[s14unimog]

So here we go again, I broke another throttle body on my SR. The first time this happened, the #4 ate the screw, I lifted my head gasket and kicked a rocker in the head. After I switched to the "new" one I decided to weld the backs of the screws encase this happened again. Well luckily that move saved my motor and I just broke the axle again. Basically all components that are related are as follows.

Freddy Intake Manifold
OEM throttle body assembly
S14 SR cable pulley
240SX throttle cable
custom base bracket.

Here is a picture of that:




Here is the carnage from the first episode. Now consider I'm not your typical "throw shit together" enthusiast. I like my car to work well and I plan for that in my build. I can't say it wasn't over pulling the stop the first time, b/c I honestly don't remember, but I will say I assure you that I set it up with good intention and adjusted everything appropriately; I thought.



Found this in the #4 cylinder with a magnetic wand




On the second throttle body I can assure you that there was ABSOLUTELY no chance I could have over pull the throttle body. I was very meticulous on the second install and was sure i had it adjusted well. Not to mention I also welded the screws to the center axle to be damn sure they couldn't dislodge. Like I said, that luckily saved the motor this time. The break was in the same place as last time and it doesn't look as though the welding had weakened the axle any. Here are a couple shots of that.





I'm not sure what I aim to gain from this thread. Maybe it will be useful in the future to someone or maybe someone on here has dealt with this before and can provide some incite. Currently I'm sourcing another OEM throttle body and plan to weld the screws as before and install as I had it. I'll then set up an indicator and see if I can't measure some amount of deflection. It wouldn't be difficult to weld on a "spine" or some additional material but I just wouldn't have thought it would be necessary. I'm also planning to review the base bracket and see if that isn't part of the culprit.

Any thoughts? Experiences?

For reference, the car is tracked as a drift car and makes just over 400 to the wheels.

[florante rea]

lmk i got a set of s14sr throttle body if needed.

[STEEZxIT]

you can use a G20 TB but you'd have to rearrange the TB cable guide...Thats what i used for mine when the butterfly decide to snap while my wife was stuck on L.A. traffic...lol

Atleast its newer thats all, Could run your $60 at the junkyard.. or FREE.. with this cold weather were having, go to your local yard with a big ass snow jacket.. HAHAHAHHA ;]

[slider2828]

Awww fuck I would be PISSED if that happened to me.... Could it be temperature related like the cold and heat accelerating metal fatigue?

The other time it happened, was it around the same time of year. cause its FREEZING in Georgia ATL.... sheesh

[PoorMans180SX]

Seems like you don't have a stop to your throttle cable/pedal, causing you to put a lot of stress on the throttle shaft when you are smashing that pedal to the floor, haha.

Fab up a stop for the throttle pulley. Problem solved.

[s14unimog]

Originally Posted by PoorMans180SX

Seems like you don't have a stop to your throttle cable/pedal, causing you to put a lot of stress on the throttle shaft when you are smashing that pedal to the floor, haha. Fab up a stop for the throttle pulley. Problem solved.

^ Problem not solved... There is one casted as part of the OEM throttle body, you can see it in the picture. What I'm going to check once reinstalled is the stop below the skinny pedal and how it relates to the stop on the throttle body. I am quite sure however that its not the problem. I wonder if its just because of the S14 pulley, since it sits further out on the shaft? Isn't the S14 SR throttle body a little different?

Originally Posted by florante rea

lmk i got a set of s14sr throttle body if needed.

Care to share any pictures for a reference. I might also be interested in it too.

Originally Posted by slider2828

Awww fuck I would be PISSED if that happened to me.... Could it be temperature related like the cold and heat accelerating metal fatigue? The other time it happened, was it around the same time of year. cause its FREEZING in Georgia ATL.... sheesh

Yeah and it happened in the middle of a 4th gear pull on the highway; sorta reminded of those Supra videos you see when the motor grenades. Similar times but I can't put my finger on exactly when it happened. The marking on the valve plate seems to suggest it wasn't just the other day. That axle has got to see the full spectrum of cold-heat regardless of outside temperatures.

[jspaeth]

Originally Posted by PoorMans180SX

Seems like you don't have a stop to your throttle cable/pedal, causing you to put a lot of stress on the throttle shaft when you are smashing that pedal to the floor, haha.

Fab up a stop for the throttle pulley. Problem solved.

It HAS to be this, right?

I just installed a new KA throttle cable on an SR throttle body, S14, and I KNOW I set it up properly....


When the throttle is fully open (verified by a second person), the pedal is NOT touching the pedal stop.

I guess the SR throttle is smaller than the KA one, and thus requires less pedal throw to fully rotate 90*.

I plan to install a piece of 2x4 or something on top of the pedal stop so that the pedal JUST hits the stopper as it opens all the way.

[Def]

Make your TB bracket out of something with some give. Use like 0.063" thick aluminum instead of the 1/8-3/16" stuff you're using now. This will give some flex there to reduce stress on the throttle shaft.

[SoSideways]

I believe switching over to the Q45 throttle body has alleviated a lot of high HP guys' problems with this same scenario.

[TheRealSy90]

Sure there is a stop there, but when you hit the stop the cable is still pulling on the pulley and putting stress on the shaft.

[s14unimog]

Originally Posted by Def

Make your TB bracket out of something with some give. Use like 0.063" thick aluminum instead of the 1/8-3/16" stuff you're using now. This will give some flex there to reduce stress on the throttle shaft.

I hear what you're saying but think about the stock setup; its pretty rigid. Don't you think its just probably the extended placement of the S14 pulley?

Originally Posted by SoSideways

I believe switching over to the Q45 throttle body has alleviated a lot of high HP guys' problems with this same scenario.

Do you have a picture of one. Are there any noticeable differences to the shaft or is it just a larger bore?

Originally Posted by TheRealSy90

Sure there is a stop there, but when you hit the stop the cable is still pulling on the pulley and putting stress on the shaft.

Na, I'm pretty sure it wasn't over pulling the stop but ya know its hard to tell now. I'll have to verify that on the next install. I wonder what the difference is between the skinny pedals' sweep and the length of pull exposed at the end of the pedal. I mean surely there is a difference given its a 240sx cable an SR throttle body, and an S14 Sr pulley.

[Def]

Originally Posted by s14unimog

I hear what you're saying but think about the stock setup; its pretty rigid. Don't you think its just probably the extended placement of the S14 pulley?

I imagine that doesn't help the situation.

I have a FReddy manifold with the stock S13 pulley still on there. I just built a bracket out of some bent 1/16" 2024 aluminum angle. It noticeably flexes before the pedal stop hits, but I've never had a problem because it basically acts as a limiter on how much force can ever be applied to the throttle body.

[codyace]

Originally Posted by Def

I imagine that doesn't help the situation.

I have a FReddy manifold with the stock S13 pulley still on there. I just built a bracket out of some bent 1/16" 2024 aluminum angle. It noticeably flexes before the pedal stop hits, but I've never had a problem because it basically acts as a limiter on how much force can ever be applied to the throttle body.

By no means am I doubting your reasoning, but I've had mine made out of 1/8" angle iron now forever, and haven't had an issue.


Ultimatly, I don't think there is a true 'reason' to this happening. I'm sure some of the smarter guys here could form up some reason in relation to pull and the force involved and that stuff (above my head!) but it's still a relative mystery.

With that said, I am going with a Tomei TB (got it super cheap) this winter to ward off any potential problem. Maybe I read to far into stuff, maybe(gasp) at times I follow forum superstition, but It's just a sake of mind issue.

[Sileighty_85]

Originally Posted by TheRealSy90

Sure there is a stop there, but when you hit the stop the cable is still pulling on the pulley and putting stress on the shaft.

I dont think that would snap the shaft, since what your pulling on has the stopper, (unless its pulling at an angle) Now if his Throttle plate is getting hung up or binding before the Throttle pully hits the stopper then yeah I could see the shaft snapping

[mct3351]

Your throttle pulley is on wrong. Placing the cable out that far is likely putting excessive bending forces in the axle when its resting on the stop.

I'd consider flipping it or making a pedal stop.

[superJoy]

Originally Posted by mct3351

Your throttle pulley is on wrong. Placing the cable out that far is likely putting excessive bending forces in the axle when its resting on the stop.

I'd consider flipping it or making a pedal stop.

WHAT HE SAID.

You have that pulley on backwards dude. I don't have an SR but on all the Nissan engine's I've dealt with, that pulley goes on the other way so the cable is closer to the TB itself. It's sticking out quite a bit farther than it should.

You're prob putting the shaft in bending whenever it hits the stop, and you're moving that lever arm out by installing the pulley wrong, which causes the shaft to fail since it wasn't design for that amount of stress.

I don't think the cable bracket yall talkin bout makes that big of a difference.

[s14unimog]

Originally Posted by superJoy

WHAT HE SAID.
You have that pulley on backwards dude. I don't have an SR but on all the Nissan engine's I've dealt with, that pulley goes on the other way so the cable is closer to the TB itself. It's sticking out quite a bit farther than it should.
You're prob putting the shaft in bending whenever it hits the stop, and you're moving that lever arm out by installing the pulley wrong, which causes the shaft to fail since it wasn't design for that amount of stress.
I don't think the cable bracket yall talkin bout makes that big of a difference.

Are you two both blind...? You can't flip it over. If you do that there isn't a place for the cable to guide. There is only one single way to install it...

[NYS13SLIDER]

ok so i just installed my new intake manifold and put the s14 throttle cable pulley as recommended by enjuku> should i be worried about the same issue?

[lok]

"Insanity is doing the same thing over and over again but expecting different results."

I am guessing you have already tried moving the mounting point for the throttle cable?

[SoSideways]

I believe Steve Shadows on here went to a Q45 TB and all his problems went away.

The Q45 TB does indeed have a larger bore, but I think the axle shaft is also a lot thicker.

IIRC he had a thread on this forum (if not, then it was probably on Fresh Alloy) explaining what was going on and the results, with pictures of course.

[codyace]

Yea it took a few trys, but I got it sorted. Made one for my roomate as well. I'll take better pics and measurements tonight for ya

[NYS13SLIDER]

Out of all of this im thinking the best and cheapest remedy(except the 2x4 behind the pedal) would be to fab up a bracket that locates the throttle cable back inwards in order to utilize the stock throttle pulley again. Am i missing something? Im hoping to finish this small but so important detail on my car today.

[s14unimog]

^ Likely. It might just be that the S14 throttle body pulley just induces too much side loading on the shaft, being that sits that far out. If what Jspaeth says is true, its possible that the pedal will allow for an over rotate scenario and just break the shaft... Either way, what ever I put back in the line of fire, I assure you those screws will be welded. It was too much of a headache to do a head gasket for this; and I lucked out with my damage....

My throttle body should be here any day now... I'll know something more by then.

[hsitko]

Guys, guys, guys. This is so simple its silly. You have the full throttle adjustment for your throttle cable too tight. You are pulling the throttle shaft torsionally when you hit full throttle because you have already opened the throttle 100% before your pedal gets to the floor. You need either 2 people or a brick to get your adjustment correct. One person (or brick) to hold the pedal to the floor and one to adjust the throttle cable to "not guitar string tight".

You want just a little bit of slack in the throttle cable when you are at full throttle. You want to open the throttle all the way just not to the point where you have already achieved full throttle and can still press the pedal further. Your cable mounting bracket might not be positioned correctly. It looks like you are already at the end of your adjustment. You do not need a throttle stop. You just need to adjust your cable properly. I GUARANTEE this is why you have broken 2 of them.

[lok]

you should put some mesh after the throttle body in case it happens again.

[bloodangels13]

red locktight the screws. I wouldnt weld them considering the shaft is probly treated metal that wont take to the heating that welding will cause. double check the stops and give the cable a hair of slack. If your still having the issue something is seriously wrong

[s14unimog]

Originally Posted by lok

you should put some mesh after the throttle body in case it happens again.

Yeah but then I would have to randomly check this "catch" for a dislodged screw and who knows what that would do to the airflow in the manifold.

Originally Posted by bloodangels13

red locktight the screws. I wouldnt weld them considering the shaft is probly treated metal that wont take to the heating that welding will cause. double check the stops and give the cable a hair of slack. If your still having the issue something is seriously wrong

I hear what you're saying, but it doesn't look as though my tack's had anything to do with the failure; the break isn't associated and happened just as the first one did that wasn't welded. I think "seriously wrong" is a bit excessive...The existing assembly, if adjustment isn't necessary, just requires more support. The next ones will once again be tacked, I'm not risking the motor on loc-tite.

[s14unimog]

we shall see. It should get here tomorrow or the next. I'm not adjusting anything until I get it all back together and can figure out what's happening.

I agree with you that this might be the problem but I do recall setting the cable up not to do that. I'll be sure to follow up what happened

[s14unimog]

Okay guys, its obvious what the problem is. After reassembling everything, just as I had it, I noted the pedal stopped, via the stop on the throttle body, about 1/4" off the pedal stop on the floor board; Doh!. Now considering you can't adjust this pedal sweep range, the only clear solution is an extended stop on the floor board (as a few have mentioned). Now my big question....


How many SR's are riding around and using the throttle body stop as the pedal stop? Answer: all of them?

I don't see how it couldn't be the case, unless modified by the engine installer, the 240sx cable and pedal assembly can't be shortened by some adjustment under the dash and considering the diameter of the SR20 pulley, it just pulls too much.

Why has this not come up more?

I'll post some pictures of my findings and fix once I get a stop machined.

[jspaeth]

Originally Posted by s14unimog

Okay guys, its obvious what the problem is. After reassembling everything, just as I had it, I noted the pedal stopped, via the stop on the throttle body, about 1/4" off the pedal stop on the floor board; Doh!. Now considering you can't adjust this pedal sweep range, the only clear solution is an extended stop on the floor board (as a few have mentioned). Now my big question....


How many SR's are riding around and using the throttle body stop as the pedal stop? Answer: all of them?

I don't see how it couldn't be the case, unless modified by the engine installer, the 240sx cable and pedal assembly can't be shortened by some adjustment under the dash and considering the diameter of the SR20 pulley, it just pulls too much.

Why has this not come up more?

I'll post some pictures of my findings and fix once I get a stop machined.

This is 100% definitely true.

The question to me now, however, is why this would ever cause stress on the THROTTLE SHAFT.......it seems to me that once the throttle pulley hits the stopper, any subsequent pressure put on the pedal only results in additional tension in the cable.

It does not seem that additionally pushing on the pedal imparts any additional stress on the shaft........

Nonetheless, I agree with your assessment.

I basically think that the circumfrence of the SR throttle pulley is smaller than that of the KA.....

Hence, less pedal action is required to fully open the throttle.


The interesting question here would be if someone owns a JDM 240sx could measure the distance between the pedal and the floor stopper in their car. My bet is that the stopper on a JDM 240 sits closer to the pedal.