MT Accumulator Delete Mod (ADM) and BS Thread

There can certainly be a negative fluid pressure through a restriction. I am not talking about gases, but the fluid is throttled through the orifices just like any other throttle, with associated losses. If a fluid can have a positive pressure, it can certainly exert a negative pressure. A simple search is there to do.


You assumed that a stainless steel disk will deflect under a minimum of fluid pressure, but do not believe that a low durometer seal can be compressed on the engagement stroke?

As a final note, the plain steel backing plate that attaches to the MT is larger and would be under a greater stress if the main disk was deflected on the disengagement stroke, which would be a very likely source for a leak.


I might buy into some sort of disk deflection if this was the boosted brake system. The clutch is a lightly loaded system with the only pressure applied by relatively weak springs in the clutch.


You are welcome to try, but I would put money on the proposed double disk solution not changing the feel of the OEM accumulator setup.

 

The double disk solution is identical to Firn's machined brass disk but instead of one thicker brass disk there are two disks (one being the original disk) that are equal thickness combined to the brass disk. You accept that Firn's solution works so why won't this?

 

+1 that this is a must do mod. I installed my hacked accumulator today in less than an hour. Night and day difference. Cleaner shifts, no bucking, and a big ol smile on my face.

Thanks for this one, TW.

 

Because it works. Clearance is made for fluid to flow, not be restricted, and not leak. That's all that the ADM needs to do.

 

Great to hear!

Was it a DIY dremel job or someone machined it for you?

 

Dick butt hack?

 

Well . . . That would work even better. All the flow.

 

I had someone machine it for me. Drilled down and out just a smidge more than the diameter of the holes.

I KNEW I was forgetting something important...

 

Very cool!

 

Thanks!



Anybody drive an FJ? Might work for them too

 

You're welcome!

Very few 2nd Gens stop in here. I don't recall seeing any FJ folks.

 

Double disk vs modified disk vs Dremel vs hardline

All else being equal (results).... I would take the route that involves the least amount of pressures. Which rules out the double disk.

Just a thought.

 

Deflection of the disk was my first thoughts as well but after opening the accumulator and seeing how thick and strong the original disk is I think that is unlikely. .

What I believe is happening is the space between the disk and the center port is just the right distance to use flow itself to create a restriction.
Ever put your hand over the drain of a bathtub when it's draining a full bath? When you JUST get your hand to the right spot there is a sudden and dramatic increase in the force pulling your hand down. There is an interaction between the flow, the port size, and the space between your hand. I think the factory accumulator operates much the same way. Basically a self limiting flow restriction. At certain flow volumes the flow itself restricts more flow, but by changing the space and angle of the fluid entering the port you break the "hydro-lock" (for lack of a better term) that restricts the flow.

IDK, that's my theory anyways.

 

Spent a few hours tonight trying to improve my process.

 

Looking great!

Nice work.

 

This accumulator operation is an interesting debate. Typically an accumulator in a hydraulic system is there to reduce pressure spikes by absorbing them and/or reducing pressure drops by storing fluid under pressure.

An accumulator is not typically a device used to limit flow of fluid.

That doesn't mean that it can not be dual purpose in this application.

From the pictures I have seen I am curious exactly how this device works in the system... and how it's removal effects the system.... I guess I should get under my truck and remove mine at some point and figure that out

 

I view it as a "fixed orifice". Based on the idea that the disc does not flex, or only flexes minimally. The distance between the disc and base restricts the amount of fluid flow. The end goal being to regulate flow. So, no mater how fast you press down or let up on the pedal, it would always takes the about the same amount of time to fully release or engage the clutch plate.
It always seemed an eternity to me, before I bypassed the device.

Maybe to help drivers new to manual transmissions, or those who have returned after years of autos, to prevent stalling?

 

Supposedly it prevents wear on a clutch. The problem is you basically lose the feel of the clutch so in my mind you're going to end up prematurely wearing it anyway. And the fact that it's not a consistent feel every time you clutch in and out drove me up the wall. Finding this thread was probably the single best mod I did to my truck

 

If this is the case, then it's funny it's called an accumulator... also funny that it is as big as it is... if it just controls fluid flow that could have been done with a small fitting and a specific orifice size.

 

That is because they didn't want to restrict disengagement, only the engagement stroke. The large surface area of the disk allows it to be pulled inward with lower (negative) relative pressure.

Image search other clutch accumulators, and they are similar or larger as well as being quite a bit more expensive.