Well I decided to experiment with this a little bit and I was looking arownd for some more pictures about this topic. But most of the threads the pictures do not show up. Well anyways, I went ahead and bought this hatch shock and installed it. The picture shows were and how I did it. Now I know someone else has done this before but I cant find any specifics on how it was done. So my question is if this is going work and be ok?

Juan

 

Won't the shock just compress?

 

I was wondering the same thing, I mean it will compress to a cartain point I guess, but I thought the idea was to have a Stiff Shock Absorber of some kind to absorb the movement created by the engine?Not sure that is going to do much. have you seen it compress?

Don't they sell these for our cars? I know they sell universal ones?

 

They sell them on racing beat I believe, but I have no clue the real gains of it.

Yep, Racing beat part # 14030

1979-85 RX-7 Engine Torque Brace

The Racing Beat-designed Engine Torque Brace, available for all 1979-92 RX-7s, substantially reduces or eliminates the shuddering experienced by many RX-7 owners when engaging the clutch in either first or reverse rear.

 

That's not going to work very well at all.

The RB part uses 2 heavy durometer bushings and a steel rod and stamped steel mount on the engine which is braced against the left front fender frame to stiffen the top of the engine. The 'clutch shudder' that they're trying to fix with this is caused by the clutch disk slipping and catching rapidly if you let the clutch out too quickly.

Nice showing for innovation, but I doubt it's going to do anything at all. Remember that you're going to need a torque arm for this 'lever' in order to get maximum effect. I.e., mounting it to your eccentric shaft pully will have zero effect.

 

I have the RB brace, and it does as it says. However the original purpose of a torque brace is for piston engines because the way their internals rotate puts alot more vibration and twist into the mounts and frame. Go rev a piston engine and you see the whole thing move. Now go rev a rotary and the thing just makes noise, but doesnt twist or move very much at all. Our rotary's don't vibrate nearly as much, but it is still beneficial and higher output engines will most likely see the greater effects of having one.

You are going to need a fairly stiff shock and it needs to be able to move in both directions, it can't just be fully extended. I can't tell if yours is or not, but just letting you know. Also it needs to be mounted higher up on the engine to where there are no mounts supporting the engine. Where it is now the two front mounts are already absorbing most of the twist.

 

I fail to see the benifit of a torque brace with the stock rubber engine mounts. I used solid engine mounts on my Turbo FB, and it took all the drvetrain flex out. Are you just trying to get the shutter out when taking off?

 

Wrap a rubber band on the chrome shaft up against the body of the shock. Drive around. Inspect where the rubber band is now positioned on the shaft. The distance the rubber band moved is how much your engine moved.

The idea behind a engine brace is to eliminate the movement. The above test will show you, that shock does not have enough power to stop your engine from moving.

-billy

 

Like I said is an experiment and It seams to be working.

 

The very laymans way I look at it is:

Can you compress a hatch strut with your hands : Yes
Can you stop a shuddering engine with your hands: No

Thus the force resisted by the shock is much less than the force exerted by the shuddering engine.

It's not scientific, but I think it gives a good mental picture of why that strut isn't going to have virtually any effect on the engine. The engine will do what it wants to do and make the shock comply with it.

Props for innovation, but I'd find a way to use that strut as a hood strut instead. It would get better use from that.

Jon

 

The shock I bought is a very stiff shock. I could not even move it. When I drove it it fealt better and stiffer and it did not move. It maybee to stiff I think.

 

Iam going to try and move it somewere else and see if theres a difference. Thanks

 

I dont even think I could use the strut for my hood. It so stiff It problebly wont shut.

 

Props for innovation. While it may slightly reduce some of the minor vibrations and soften the larger ones, in the end it won't be terribly effective. It reminds me of the older Civics that had a shock absorber mounted to the firewall, then to the engine to reduce the engine movement that's inherent to transverse mounted fwd drive trains.. Those units were much more substantial than the one you have.

I have an RB torque brace that I haven't installed yet. It will need solid or poly motor motor mounts and stiffer tranny mounts to be truly effective. End result will be any vibrations that are dampened will be transfered to the chassis.

 

I'll give you that. You will have more road vibration through the chassis doing this. I guess it's the "side effect" of this. I will say that after I went with the solid engine mounts, I noticed the car launches harder off the line.

 

It should launch better with stiffer or solid mounts. Softer mounts absorb 'wind up'/energy' during launch which translates into stealing torque when power is initially applied to the drive train. This wind up energy isn't released until the rate of acceleration is less than the stored energy in the bushings/mounts.

Often the stored energy is released when the clutch is pushed in during shifts and ends up being completely wasted and not transfered to the wheels. Once the power is applied in the next higher gear, the process starts all over again.

A good visual example of this effect is watching a high hp car launch at the drag strip and watch the entire body twist, often leaving 3 wheels on the ground but the front driver's side wheel will lift off of the pavement. It takes a huge amount of hp to twist a chassis like that and most all of it's wasted needlessly.

While the twisting does provide a good deal of weight transfer to the right rear wheel, which is usually the power wheel, stiffening the chassis and reducing the twist would put more net torque to the ground.

 

^^^^Thats good info trochoid. Well then I will buy some solid mounts. Who do you recomend? Like I said this shock thing is an experiment and I do feel a difference. I read over the specs on this shock and it said that it holds 150 pound of force I think this is a very stiff shock and it could work better if I place it on a different place. But this is a learning event.
Juan

 

This is the RB inspired brace I fabricated for my car. It made a huge difference to the amount of shudder I get from the brass button clutch.

 

^ Now thats nice work there. I dought I could do the same cause of left hand driver side.

 

I've had my RB brace for 5 years or so, an love it.
I did notice though over time that the body and front fender have moved differently after time and there is paint cracking where the fender bolts up on the engine bay side.
Also noticed over time the vibration and sound that came into the cabin from the brace has either toned down over time or I got use to it.
When first installed you could here it inside the car. Not super loud, but I did notice a change in sound from the normal.

I do like your shock idea, try putting some grease on it and go for a run, and see if you get a streak marks to see how much the shock moves.

pic of my RB Brace

 

^ Thanks. I will do that and see if the shock moves and how much is moving. I also wanted to move it more towards the rear of the engine to see if is better.

 

Check out this one.....

Very solid and looks better.

https://www.rx7club.com/1st-generation-specific-1979-1985-18/how-i-spent-my-day-off-661350/

You need more than just that one bolt in the shock tower.

 

your idea is okay. i know because my brother did the same thing to his car - been runnng it like that for about 5 years now. i was able to detect a difference, without much of the harshness i've read about with real, honest-to-goodness torque braces. it aids in street "launches" (not clutch dumps, just regaular pedestrian standing starts) and since it IS a street car i think it does it's job beautifully. so really it all comes down to what you want from it. if you want to dampen or eliminate (not sure how realistic that will be without causing other potential issues, as Max7 proves), then you will need to get something better than what you've created, and go with something solid. if you just want to make a 20+ year old car feel tighter/younger, then leave it as is.

for my own personal cars, i prefer the solid stuff because vibrations don't bother me at all and i will be buying or making one whenever i finish building this motor and get it installed.

 

Hey Trochoid (and others),

What is your opinion of this type of setup? Is the whole shock absorber idea a waste of time, regardless of how it's done?

What if this setup above was done with a steel bar or tube, instead of a shock absorber?? That should eliminate all movement, but how effective would it be?

 

Here's mine. Car hasn't run yet, so I have no data. Even then, I won't know what it was like without it, so I'm not much help. But I think the general concept is there. The brace is an Ingalls Stiffy.