Just don't drop the clutch

 

The diff is fine.
Stiffer rear springs are a good start. A heavier sway bar might help, though chassis braces would probably be a better, more neutral-handling option.
Might consider replacing the swaybar bushings with urethane and heavier heim joints at the ends.

 

How are the 8's stock engine/tranny bushings? Sometimes an injection of urethene in "some" (not all) of the factory mount bushings can help reduce wheel hop. I have no idea how much the renesis flops around under load though =/.

 

Well I put it all back together and now it is fine. Something must have worked its way loose but I am happy that nothing is broke. Thanx for all the input.

Great Jooooorrrbbbbb

 

great job

 

Snoochie booches.

I have played with the ide of filling the OEM motor mounts with high durometer urethane. I have a can sitting around from another project and the OEM mounts are quite soft.
I'd just hate to add too much NVH.

 

Well, we will have to see which route is best to top the map when you spray.
Probably will use an analog input on the E-01 to provide the extra kick on the "boosted" map to pull the timing.
I'll have to read up on this. My mind is swimming with all kinds of unrelated data at the moment....

 

Yeah, that is the right track. The trick is to make your "trigger" voltage exactly 5v.

I can give you a complete circuit diagram. I can make the board for you (no problem), but it will take a week. It will supply the RPM input and the ignition circuit filtering.

 

Im sorry to sound noob but i cant think of what nvh means? Also are you planning(or anyone else) making/up-grading mounts? I would be interested in that if so.

 

NVH = Noise, Vibration and Harshness

Factors that automotive engineers spends lots of time and money to eliminate without loosing road feel.

 

NVH = Noise Vibration Harshness

 

Jeff,

Do you guys only have two primary engine mounts? Us FWD (so sad) 6 owners recently started replacing the #1 engine mount with a cnc machined repalcement with 60 rated urethene bushings. So far the NVH differences isn't noticable except at inital startup (when the PCM programs warmup idling).

Then of course you guys don't have an extremely weak and pathetic wishbone mount.



The wonderful guys over at CP-E did the mount. I'm testing it in my car now, will probably go with an 80 urethene as a final production version.

http://www.cp-e.com

 

Jeff, please help me get this right: I agree with you, but is there a coilover that allows you to adjust spring rate? What about shock stiffness, will it help with wheel hop?

Do you mean the sway bar endlinks in the last part?
Thanks

 

Those are nice looking mounts.

The RX-8 only has two motor mounts. They are fairly close to symmetrical and are mostly hollow - they just have and upward rubber cone upon which the aluminum arms rest.
I am going to fill mine with 80 durometer urethane. It shouldn't effect the NVH values too greatly because while the motor is stationary, it will still be suspended on the OEM rubber cones. It is only in acceleration/decel and cornering that the mounts are distended as it turns about its rotational axis.

The Tein coil overs allow you to adjust the spring preload and height independantly by moving both the upper and lower spring perches independantly.
Shock stiffness will definately help, you are limited in your choices at the moment. The factory shocks are just a notch above useless. The fronts are practically non-shocks right from the factory. That is to improve smoothness over irregular road surfaces - something the North American market craves.

Yes, sway bar endlinks.

 

You cannot change the spring RATE, you can change the preload. The rate is in the spring and can't be changed no matter what you do to it. You can find the rate of a spring by knowing the od, wire size, active coils, oal. You must change those things to change the rate.

The instant pressure can be changed by preloading the spring with the adjusting nuts. This only raises or lowers the car. This will also change the weight on that wheel and jack it into the opposing one.

This is how you balance the car for a given set up and track.

 

The advantage to adjustable upper and lower spring perches is the ability to change the preload without changing the vehicle height.

 

If you had progressive springs, increasing preload would change the initial spring rate as well right?

Is that a common item? It sounds like a relatively cheap but very worthwhile mod. Wasn't someone supposed to come out with stiffer aftermarket mounts?

 

You can get it here:

http://www.mcmaster.com/index.asp

 

thank you thank you thank you!!
(to richard too) I wanted to say 'spring preload' not 'rate', its uuh... my english :D sorry, but still great info! You are rght about the stock shocks, thats why I want to change them asap (dilemma between tein flex or hks:o...)

 

A progressive rate spring is very hard to make. Some have tried with tapered wire for coil springs but theQC was a problem, getting it to start the same as another spring to et a matched pair. Others have tried to do it with linkage. It just didn't seem practical.

 

It is usually done by stacking two different rate springs on top of each other.

 

A progressive rate spring has two or more rates within its range of deflection. This is accomplished by varying the pitch or helix angle within the spring. The spring rate increases, becoming stiffer as it is compressed. This happens when the portion of the spring with the finest pitch (coils closest to each other), goes into coil bind. This is called the transistion point. The remaining portion of the spring continues to function, but at a higher or stiffer rate, because there are fewer coils functioning.
________
MARIJUANA BUBBLER

 

this thing you talk of! is it next to the quad angular dispatch? :D

 

Guys, I strongly urge you not to modify your OEM engine mounts unless you are willing to deal with absolutely terrible noise and vibration, or can easily afford to buy new OEM mounts and have them installed. There is a lot that goes into engineering even the conventional rubber mounts used on the RX-8. The mounts are tuned such that PPF is well-isolated from engine vibration. This is achieved by setting the stiffness characteristics mounts such that the natural frequencies of the engine roll and hop modes are well below the firing frequency at idle. Inserting material in the mounts to make them stiffer is a completely uncontrolled process and you have no way of knowing what you'll end up with. It is very likely that your idle noise and vibration will go to $h!t because the stiffer mounts will transmit much of the engine vibration straight to the PPF and then on to the body. This is just my word of warning to you.

Unfortunately, filling the mounts will greatly affect the NVH characteristics of the car. The "hollow" part of the conical mount is just as important as the rubber when it comes to the stiffness characteristics of the mount. Mounts have two purposes: to restrain the motion of the powertrain, and to isolate powertrain vibration. Everything you do to improve the former will degrade the latter. The STATIC stiffness curve of the mount is what controls the neutral position of the powertrain as well as the maximum travel allowed. Filling the mount with the urethane will increase the static stiffness and help restrain the powertrain; however, at the same time it will also greatly increase the DYNAMIC stiffness of the mount. Dynamic stiffness represents the stiffness of the mount in response to inputs of varying frequency, such as powertrain vibration. If you increase dynamic stiffness too drastically, you risk screwing up the modal separation (natural frequencies) that the Mazda engineers worked so hard to achieve.

The pendulum-type mounting system used on the Mazda6 cannot be compared in any way to the RX-8 mounting configuration. The mount you replaced (which I assume is the one shown in the picture) is the roll restrictor that bolts the transmission to the PPF underneath the car. It is NOT the LH (transmission) or RH (engine) mount, and that is probably why you didn't notice a significant degradation in NVH (Also, the original bushing looks damaged--the rubber is torn. If it was like that while installed, it's no wonder you didn't notice a degradation with new roll restrictor!). The roll restrictor simply limits the amount of roll of the powertrain in a FWD vehicle with pendulum mount configuration. Making changes to the LH or RH mounts will have a much greater impact on NVH.

I just want to make everyone aware of the risks. I understand that stiffening of the powertrain mounts is necessary to improve the dynamics of the car, especially with upgrades that yield significantly more torque/power. This is the reason that many aftermarket performance companies sell stiffer mounts. The difference is that these companies have had a chance to test the mount tunings on one or more vehicles. They did not blindly increase stiffness and offer them to consumers. If you don't rely on your RX-8 as a daily driver, or if you have the time, money, and patience to deal with an intolerably noisy and rough car, then you have nothing to worry about.

 

Rx8 buckeye,

Btw the original mount wasn't torn...thats how they designed it =/. But ya I agree with you. I'd also like to point out that though NVH differences may not be completely noticable on a stock suspension car...the second you start stiffening the springs and shocks, the chassis will transmit even more of the vibration from the stiffer mounts.

Of course for some people, this won't bother them one bit . I came from a 1974 grand am pontiac...there isn't a piece of rubber left in that entire NVH system. lol.