All,

Want to describe my experiences with low compliance engine stabilizer bushes in the hopes that others will contribute their experiences.

The engine stabilizers are those two rubber bushed links, one on the top of the engine on the passenger side and one on the bottom of the engine in the rear middle position. These stabilizers consist of a bushed small end that connects to the engine and a bushed large end that bolts to the chassis. Why bother? The MINI engine moves quite a bit when on the dyno. I was thinking anything that will stabilize the engine/trans-axle unit will minimize torque steer. Torque steer has become a real problem with my modified engine. How do you tell when you've stabilized things enough? Check out the handling. Also, there is a direct relationship between reduced compliance and increased vibration. I know from decades of automotive experience that the limit on compliance is ride quality. Low compliance bushes can cause intolerable vibration at the limit. So, I reduced compliance in my MINI engine stabilizer bushes until I couldn't stand it any longer, and the CD player quit working and then backed off. (true)

Here are the bush compliance combinations and my observations:

1) Stock rubber bushed stabilizers - good ride, no vibration, and definite torque steer.

2) Power flex poly bushes - a purple small bush for the engine side and a large yellow "insert" that clamps into the casting indentations of the large chassis side bush. The purple bushes exhibit less deflection than the stock rubber bushes when levering the bushes from side to side. No difference in vibration and handling from stock.

3) Rubber large end bushes and solid Delrin small end bushes - only a slight amount of vibration at low RPM's and a definite reduction in torque steer. A good way to go.

4) Delrin large end bushes and Power Flex poly small end bushes - Definitely more vibration at low RPM's and not sure if the torque steer is reduced or not. Promising and needs more testing.

5) Solid Delrin bushes on both stabilizers on both ends - Gads ! Maybe just the thing for Joe Racer, but not for me. The car shook and vibrated and made a loud low frequency rumbling noise as the engine reved up and down going thru the gears. The CD player kept stopping and starting. Horrible and intolerable. Not for the street driver, in my opinion.

At this point I'm going with the Power Flex poly small end bushes and the solid Delrin large end bushes. Not the cushey stock ride, increased vibration, but not bad. Hope that the torque steer will reach the vanishing point. Any observations from others?

Regards,
John Petrich in Seattle

 

hey, me again.

I have had the full powerflex setup for a year now. I don't experience torque steer, which I would define as a tendency for the direction of the car to move left and/or right from straight influenced by hard acceleration. (distinguished from a tendency for the car to straighten out under hard acceleration exiting a corner).

My car is putting out 190 wheelhp and has a Quaife limited slip, coilovers, spherical upper strut bearings (no compliance) and Pflex front control arm bushings and steering rack bushing; I am waiting the time to put in the rear trailing arm bushings and maybe the 8 control arm bushings, also Pflex.

The first Pflex units I installed were the upper and lower engine mounts, yellow and purple. Previously, I had been drag racing at Englishtown, hp at the time in the 150 range. no L/R wiggle down the straght before the bushings, but more wheel slip on takeoff than I liked. The bushings seemed to improve things. I did get an annoying vibration at idle, disappearing at >850rpm.
Then I installed the transmission Pflex bushing, which stabilizes the driver side end of the engine unit. the vibration picked up. At the time, my car also had a the 15% pulley and lightened flywheel, contributing to the noise/vibration propagation. I tracked the car a few times and it felt great. Autocross was improved (I even let another driver try out my car for a comparison) still no evidence orf torque steer.

I was fed up with the vibration however, and about to start pulling bushings when circumstances caused a flywheel change, back to stock. much improved noise and tolerable vibration; I'll probably leave things alone. The front end of the car seems rock solid with very precise steering. I am waiting for the next track date to wring it out more completely, but so far, there is no comparison to an un-stiff-bushed car.

I am about to increase hp again with a head mod, looking for >200 at the wheels.

 

Jim,

You may be correct and I may have to quit talking about "torque steer". My experience is limited to street driving and those occasions where I think I am experiencing "torque steer" are not consistently reproducible. Maybe I am detecting minor changes in steering that come from the combination of road irregularities and minor chassis compliance. A couple of friends with experience racing VW Rabbits all remark at the perceived lack of torque steer when they drive my MINI. Maybe I am on a fools quest; looking to find and eliminate something that really isn't there.

We both have been making chassis/engine changes and those experiments may be confounding our observations. You have the LSD and lighter clutch and other changes.

I have also re-worked the drivers side motor mount. I installed the Power Flex yellow bush inserts into the drivers side rubber motor mount. To stiffen the assembly I machined two aluminum shims to fit between the chassis side mounting bracket and the sides of the Power Flex bush assembly: to really clamp the whole motor mount tightly together. The theory is to increase the stiffness of the motor mount assembly with the Power Flex inserts and push the lateral stability of the entire assembly to the limit. Again, the idea is to reduce torque induced movement of the engine trans-axel assembly. Did pick up some vibration just from that modification. Been driving with this motor mount for about 1 year.

Have also experimented with the M-7 fabricated tubular steel front "A" arms and Delrin/bronze "compliance bush". No ride problems and a whole lot of front end stability. Drove my daughter's stock Y2002 MCS back to back and noticed a slight "drifty" quality to the steering on curves and at freeway speeds with her car that are not present on my "Delrin MCS".

I think that I have gone as far as I can at stabilizing the front end by reducing bush compliance. What ever residual steering instability that I detect is probably not typical torque steer. Not sure if I experiencing anything real.

Good luck with your engine development. Like to hear what you have up your sleeve.

Regards,
John Petrich in Seattle

 

The experimentation continues, at least with Delrin (courtesy of Peter at M7)...

John, never mind the PM I sent earlier, I used a vice

I will share my driving impressions later. Since I find it easier to post pictures on MINI2, here is a link:

http://www.mini2.com/forum/showthread.php?t=57353