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Pitch stop rod upgrade not pointless, but it is noisy!


Gripless
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Ok so since the crank is inline with the gearbox the boxer engine rolls not pitches under load. It's not like an East West mounted engine like the evolution.

It also sits in the near the center of a triangle of engine and gearbox mounts so can't be under almost any load ever.

To make it worse if its almost solid mounted then since the engine rolls the pitch rod will be twisted and untwisted constantly stressing the bracket and transferring noise.

Plus any small frontal impact will drive the rod into the firewall and gearbox. I've seen the rod snap even under minor impact and the same way the engine mounts shear so the impact isn't transferred to the occupant space.

 

Other than it seems like a great support when you remove the engine and leave the gearbox hanging. Why upgrade it?

Edited by Gripless
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Yup, a tiny rod it be but its there to help

when launching hard the momentum causes the gearbox end to try and push downwards - the gearbox mounts help stop this

at the front of the engine it does the opposite at the same time, the front tries to lift, the engine mounts help stop this

the pitch stop rod just helps that little bit extra with both movements by transferring some of that force to the firewall

 

I've never upgraded one, and have never seen one thats worn out. however i am upgrading gearbox mounts (did the engine mounts already)

If I saw an aftermarket one for a dece price id probably buy it just so I have the peace of mind of 3 strong points while im fanging around the track :)

 

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I can't work out how it gets loaded up unless the engine and gearbox mounts are stuffed.

the flex in the rubber mounting points or that rod mean that another mount has to flex a long way before it gets any load.

 

id love to see Subarus official data on how it works and what the F*** it's really for.

 

tempted to remove it and place something there to measure the load or deflection.

I don't get wheel hop on launch, just 4 spinning wheels.

 

After seeing a couple of cars with light impact damage I'd guess it'd do a lot more damage if the rod was solid. 

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Front axle torque lifts the gearbox and engine.

 

Edit - front axle torque tries to rotate the engine and gearbox assembly backwards, engine up and gearbox down. Yes pesky prop shafts and whatnot also get in the way, but the torque reaction is there.

Edited by boostin
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Just sounds like the Internet is basing this on the marketing blurb for aftermarket braces.

You guys maybe be correct, I just can't yet see how the replacement does more good than harm.

 

The fact we have four wheel drive makes lift seem suspicious. On a front wheel drive that could be the case. But since the rear wheels are also pushing the car forward the amount of lift is minimized to the drivetrain and grip difference. Ok so the driveshaft and diff hangers are pretty floppy so there is slower response in power to the rear wheels.

 

Sounds like it is almost based on the suspension squatting at the rear due to wheel rotation.

 

Then there is that the wheels are directly attached to the suspension which will take that load more or less based on the castor and the springs extension would take less to move than lifting the engine from the car. Which is why cars squat on launch.

 

I see Perrin updated the rod at some point due to causing firewall damage. Starting to show up after a few years installed that the spot welds are coming loose (I guess from the engine rotation).

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No real valuable input to add other than that the fact the old rod ones bending means there must be a decent amount of force applied if even for just an instant. Which could be seen as good or bad depending on whether you want as little loss as possible without worrying about shock load damage to other components or not 

 

Most seem to think on/off throttle engine/transmission movement/jerk is considerably reduced but i’m sure alot of the time it’s just in people’s heads.

 

It’s just another piece of the mounting puzzle and if upgrading the other engine/transmission mounts this ones a no brainer for what one costs. 

 

Of all people on here i’d say Gotasuby and Boostin are the experts and if they say that happens i’d take their word at it

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21 minutes ago, Joker said:

nothing to add here other than the Majority of Subaru's are built on a FWD platform with a rear diff 'tacked' on, in essence & if it does nothing then might as well bin it then :P

 

Not saying you are wrong... but what are you basing that on?

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The FWD bit?

 

@Loren

 

they are / I read it on the internet somewhere :P perhaps like many legends or myths there's a glimmer of truth to it & the tale gets embellished every time it's retold

 

keen to get thoughts on Chassis experts on that one for comparisons vs other AWD platfoms etc

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On my old and dearly departed 2.5 N/A legacy I found I was hearing a clunk when accelerating hard and the letting off the gas.

Had a look under the bonnet and found the pitchstop link was stuffed.

It was the plastic dog bone type link and the rubber bushes were gone, so replaced it with the metal rod type with good bushes and it fixed it right up.

Turns out there was a bit of movement of the engine (the other engine and gearbox mounts probably were on the soft side which wouldn't of helped).

Not sure if you need an upgraded on apart from it looks good, I would just get a new replacement one if you are worried about movement

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Look it must do something or it wouldn't be there. If you have a front mount then chances are you'd get and aftermarket one to look pretty. But from what I can find the aftermarket ones just cause more issues with rotational loading on the upper mount, and a heap of noise. Plus the risk of fatigued alloy in the gearbox and not allowing the engine to move correctly in a crash.

 

They offer a group N part which has been homologated which shows the factory and sti ones could be stronger if you can tolerate the NVH (guess as sales blurb says harder rubber).

This also suggested it does get some load even with the matching group N engine and gearbox mounts.

 

The design is for loading almost directly inline with the rod, which may indeed be the front driveshaft like @boostin and @gotasuby said. 

Old one below had bolts directly inline with the center of the rod so must have been directly loaded.

 

Group N part not like the eBay version which is just an STI one.

D1040FE000 ~USD$55

group%20n%20pitch%20stop.jpg

 

STI old one in picture, but the current one is just a bit more squared off at the edges and same length from 2002 upwards.

sidebyside6.jpg

 

 

I'm tempted to get the group N one and see what it does. Not like I won't feel the difference if there is one, as I have every mount and bush replaced so NVH is life.

 

 

 

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6 hours ago, Joker said:

The FWD bit?

 

@Loren

 

they are / I read it on the internet somewhere :P perhaps like many legends or myths there's a glimmer of truth to it & the tale gets embellished every time it's retold

 

keen to get thoughts on Chassis experts on that one for comparisons vs other AWD platfoms etc

The early autos were. Permanent drive to the front and variable to the rear. Manuals and later autos with VTD can vary drive front to rear. Then there's DCCD.....

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Yep, not sure on other subis but from memory the majority of power is distributed to the front wheels in an RS (is it 60%? or 70%?)

Ill get one and do some serious track testing (any excuse to hit the track will do) :P 

 

12 hours ago, Andy_Mac said:

 

Of all people on here i’d say Gotasuby and Boostin are the experts, also Thunda is the trainee junior expert assistant and if they say that happens i’d take their word at it

 

:P:P:P:P

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Added a billet one off ebay for a laugh a while back, couldn't feel any difference. Sure it does something in theory and it looks sort of cool but can't tell on track or road if its there or not, car already has a lot of NVH so might've missed that aspect.

 

Edit: this was the most solid one I could find, way beyond a Grp N and still couldn't tell, drag racing/launching talk sounds logical to me and I haven't done that myself so couldn't comment

Edited by YoungOne
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Pretty sure early to mid 90's Mitsubishi had the FWD bias higher than anyone else and it was only about 60/40.

@THUNDA Guess you're going to have to do a lot of testing or drive in reverse.

 

DCCD are 50/50 to 35/65 and everything inbetween so still rear bias. 

Edited by Gripless
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11 hours ago, boostin said:

The early autos were

 

yeah I'm not talking drive ratios or splits

 

they are an actual FWD chassis / built to be front tuggers geometry's & such : not sure how to prove it or find the 'source'

 

& linking to the 1969 birth of Subaru AWD cars wont help my cause but here it is

 

years apart & chassis designs did change but "i read it somewhere" or saw it in a youtube video Subaru's are a FWD Platform with rear diff's chucked in

 

even AWD Subaru's act and drive like FWD without the skill or aggressiveness needed to make the AWD system usefull etc (which might just be my backwards way of aggreeing with the drive split statement) I dont know I'm right but by jove's I love a good internet discussion :P

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19 hours ago, Gripless said:

Pretty sure early to mid 90's Mitsubishi had the FWD bias higher than anyone else and it was only about 60/40.

@THUNDA Guess you're going to have to do a lot of testing or drive in reverse.

 

DCCD are 50/50 to 35/65 and everything inbetween so still rear bias. 

 

Im not actually going to test the pitch stop rod - I just like to use whatever excuse I need to get some track time in :P

30seconds on googling shows some auto subarus distribute up to 90% F 10% R

Manual gearbox most common is 50/50

There are loads of variations, guessing it was just simpler to put the rod in every model 

But all this talk about pitch stop rods has already made me want to buy one off trademe lol ^_ ^

Turns out they dont have one for my RS so meh

 

https://www.trademe.co.nz/motors/car-parts-accessories/performance/core-engine/auction-1535108351.htm?rsqid=f78f1f1e457e4c809957185088655f2f

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@THUNDA thought you could test the torque split not the rod.

Well don't count autos, they are barely cars :P don't even have DCCD in the sti.

 

yeah thinking the same thing $65 and I will most likely pull the cooler this week dealing with the power cabling.

 

nzkw website is so S*** animated squares on loading pages, too much pretty and poor functionality. Good thing they use trademe or you'd be F***ed finding things.

 

Edited by Gripless
Pretty non functioning website improve sales... Yeah right
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1 hour ago, THUNDA said:

 

Im not actually going to test the pitch stop rod - I just like to use whatever excuse I need to get some track time in :P

30seconds on googling shows some auto subarus distribute up to 90% 

https://www.trademe.co.nz/motors/car-parts-accessories/performance/core-engine/auction-1535108351.htm?rsqid=f78f1f1e457e4c809957185088655f2f

 

Pretty sure that will be identical to yours dude. Just get them to measure it up.

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