Effects of Engine Torque Brace
 

I am reposting a racing relevent part of my review of the under $100 engine torque brace I wrote in the 3rd gen specific section because I have no way to empirically test the physics and really want to know if I am just imagining this effect (wishful thinking).

Since I installed the Engine Torque Brace I have noticed something new and startling. There is a phenomenon called torque steer in FWD vehicles that is not around in RWDs. That said and remembering that I have a car that has excellent stock suspension and nearly new stock motor mounts, I have noticed that when accelerating past the apex of a tight righthander, there is a clearly tight line held by the steering that is completely independent of the amount of throttle applied. Prior to the installation of the torque brace I always felt that the front right dipped into the curve more as more acceleration was applied. I assumed that was the result of the engine torque being applied to the lower right side of the frame causing the forces to be downward and inward. Since the addition of the ETB this phenomenon is not apparent. Whether this torque phenomenon really existed or if it was just a fantasy, I can't say. What I can say is that since the ETB I stopped the hallucinations and the car seems much more solid in those tight acceleration righthanders.


If it is true, I think I am going to get a little more understeer and I will not have to worry about future changes in the inward accelerative steering geometry due to normal wear on the parts.

The installation of the ETB was the only change made and this phenomenon only occurred after the install.


Can anyone confirm or poo-poo this idea as it relates to ETB installations.

The only noticable difference when I installed mine was that the car became easier to shift quickly. The gates on my racing transmission are alrays right where I expect them to be, because by drivline doesn't rotate when I get on or off the gas.

My car does appear to be mildly more responsive under hard acceleration, as if the power is reaching the ground quicker, but this could be all in my mind.

Torque steer is actualy caused by the drive shafts being different lengths between the diff and the hub. A rear wheel drive car can still have this problem if (for some strange reason) the differential is not in the center of the car.
Modern Subarus for example do not have torque steer because even the FWD models have equal length drive shafts.
But depending on how soft the FD chassis is, I do not doubt the changes in handling made by an engine brace.

I wonder if the phenomenon you're experiencing (if it is from the torque brace) would be experienced on a torque brace using a shock such as the FEED unit...Just a thought.

buttlips...

Wow, interesting.. That's my numero uno issue right now with the RX-7, shifting properly, I miss a gear about once a session.. Good thing my class allows braces, I'll give that a shot.

PaulC

Paul,

I tried solid engine mounts (I run in EP) to solve the shifting problem, but they vibrated my car apart.....literally. I had to do a bolt check after every session.

I put the stock rubber mounts back in, added the brace, and it worked just as well, but no fillings fell out of my teeth when I raced. :D

Chuck

even with new engien mounts (rubber) I find throttle transition on RX7s sloppy, with torque brace, it is very solid like solid mounts, except solid mounts will make your teeth fall out liek buttlips said

My Subaru has enough torque steer to just about rip the steering wheel out of my hands, if I don't have a tight grip.

ETBs kinds and types
 

I am sold on the engine torque brace, but am not sure which one to buy. I like the CrispyRx7 (Chris Regan) designed brace that the Rx7 Store sells for $180 ($185 whatever).

Which brace did you men end up buying?

FWIW, I too was going to buy the solid urethane mounts from Rotorsports Racing, but did not want to deal with the increase in NVB, so I stayed with the latest version of the stock rubber mounts from Mazdaspeed Motorsports Development ($150 each)

Yet I'm having trouble making clean heel-toe downshifts without a little gear grinding from the gearbox (particularly 3rd to 2nd)

I'm hoping the ETB will solve this issue?

BTW, do any of the ETBs interefere with the ABS box at all from fore/aft movement?

Re: Effects of Engine Torque Brace
 

I'm confused.

The right-front corner of the car should dip more when turning into a LEFT-HANDER, not a right-hander?

During a tight right hander, under moderate power, your RF should lift a little, while the LR should be squatting, putting the power down through the LR tire?

FWIW, I've been told, that I actually lift a RF tire through Putnam Park's tight 9/10 combo (you'll find out yourself March 22 2003 :) )

Are you saying the RF-dip has decreased with the addition of the ETB?

Clarify for me please :)

Re: Re: Effects of Engine Torque Brace
 

Manny

Assuming that the correct jargon for a righthander ( and I am not sure that it is correct racing jargon but I think it is) is a curve going toward the passenger side of the car, then my description stands. "Pre-torque brace" I felt the right hand side dip into a tight righthander when under moderate to high acceleration.

My explanation for this is that, under power, the engine rotation goes down and to the right (from a driver's perspective) essentially increasing the weight (downforce) on the right front corner. The action also pulls up on the driver's side frame (left) essentially lifting the left front tire. These actions are minimized by the addition of an engine torque brace. See this recent thread for a video of the engine action

https://www.rx7club.com/forum/showth...t=torque+brace

I have the custom made (non-adjustable) torque brace made and installed by David Garfinkle in Murfreesboro TN. It is as fine an addition as can be had for under $100. I do want to say that Crispy's unit sold by the RX7 store is an excellent choice and requires no fabrication. I personally prefer David's because of the fact it spreads out the stress across a larger surface area on the fender.

Hope this helps

Jeff

After looking at the Putnam Park Track layout I now understand the forces you are describing and those I am describing are, in fact, different forces and both occur.

The force I am describing (engine torque) is as above and actually would tend to make the front end dip into the track more on moderate to hard acceleration causing the driver to experience a steering effect from the front right tire.

I think the force you are describing is the pure force pushing the car (all 4 wheels) outward from the center point of the turn. That force will cause the right side of the car to lift as the left side crouch and dip as the left side tires roll over farther onto their sidewalls.

Putting these forces together I beleive that I was feeling a difference as I entered the apex and applied moderate to high acceleration. It was this dipping which forced the right side back down onto the pavement and decreased the amount of understeer felt up to the point at which heavy acceleration began.

With the torque brace installed, there is no additional downforce imparted to the right side during the turn thereby minimizing the change in steering feel and hence reduces the need for steering or acceleration correction. I believe the addition of the torque brace will make the turns under acceleration different than previously experienced but will also make the driving through them much more predictable.

Ok. I don't feel those forces with my car, and I have never had an ETB installed ?

I did order an ETB from Rx7 Store today. I'm looking for more solid shifts, particularly downshift from 3 to 2 at Putnam Park's Turn 7 (ridiculously slow and tight 2nd gear 85-degree right hander)...

My new motor mounts helped a little, but I still get some gear grind and must shift with caution lest I grind the gears!

Anyone having experience with the RB or any other, torque brace for the FB? thaNKS

I wonder why Mazda didn't put a brace on from the factory. I can't see that it would transfer much vibration to the driver and the cost would be almost nothing. Soft mounts and a brace wins out over stiff mounts and no brace in my book.

yeah, my assumption is the feed unit would create a lot less vibration than a non-shock unit.

the only effect I have seen from an install a friend did was that it seemed to shaked the crap out of the car when he had his A/C was turned on. Anybody else experience this?

AC?!

haha, i was thinking the same thing. this is the race car section right?

hey, did you ever get all those motor parts to smokey?
Roan