CjsfastSS

In all honesty I'm kinda lazy when it comes to reading, so normally what I'll do is take the most recent topic, read like the last 2 pages and hopefully hit the nail on the head. :D

Overport

Greddy SP2 Exhaust....looking for it:D

RIC SHAW

with all these mods going on you will need an adjustable piggyback ecu that is easy to use and tune fuel and ignition. and for turbo if needed. yes???
we have one here in Australia at Ric Shaw Performance. it has been diccussed before .

nf9648

Correct me if Im wrong ut isnt the Renesis engine internally balanced? If so then it is like my ZX2 motor also, and a lightened pulley shouldnt affect it as much as say, a lightweight pulley on a 5.0l with a 28 or 50 oz. damper on it.

canzoomer

In stock now!
Shipping from Canada or Huntington Beach, California.

Japan8

Is that right? Where can you find weights for the various rims on the market? Enkei and Team 5 Zigen didn't have any weights on their sites... The same goes for the brake rotor as well...

Pk14

We've had a discussion of the impact of unsprung weight versus weight removed from other areas of the vehicle and the consensus is that the most benefit will be noticed in the handling side versus outright acceleration.

Wheel weights are not all that easy to figure out from most web advertising. There are a couple of sites that offer weights for specific wheels in a given size, however, the quickest way to figure it out is to pick the wheel you are interested in and contact the reseller or manufacturer directly. The stock wheel (18 x 8) is 21 lbs.

Take a look at Stoptech and Brembo. (Stoptech just came out with a front 2-piece rotor as part of their upgrade kit, ~$2000), and I believe they were advertising ~9lbs less at each wheel.

Pk

Japan8

Ouch... dem rotors are expensive!

Changing the weight of the vehicle period is mostly good for handling only... unless you can drop the car down to like 2500 ~ 2700 lbs... correct?

Well either way it won't hurt to grab a set of aftermarket rims...

Pk14

So long as they weigh the same or less than stock and are sufficiently strong to handle life's daily challenges like potholes! Unfortunately, adding unsprung weight with "less expensive" aftermarket rims can adversely impact the handling feel the car provides when stock. Some of those rocks easily are 30 lbs a piece!

Landon_Starr

whoa whoa whoa. 10 times? Unsprung weight does have a much higher impact than sprung weight, but this is quite the exaggeration. Here's an enlightening calculation:

"
Okay,

I recaculated. The kinetic energy of a non-rotational mass experiencing translational movement is:

Kt = 1/2 *mv^2,

where m is mass in Kg and v is velocity in m/s. For a rotating mass experiencing translational movement, the kinetic energy is:

Krt = 1/2 * mv^2 + 1/2 * Iw^2

where I is the moment of inertia and w is the angular velocity in radians per second. For a 18 inch (.4572 meter) wheel that has all of its mass on the outer rim (worstcase), it has an I of:

I = mr^2 = .0523m

and has a angualar velocity of:

w = 2pi * v / (2pi * r) = 3.03v

where r here is the radius of the 26" wide tire. Substituting back in to the earlier equation we have:

Krt = 1/2 * mv^2 + 1/2 *.0523m * (3.03v)^2 = .7398 mv^2

so Krt = .7398/.5 Kt = 1.480 Kt

Or, stated differently the energy needed to accelerate every 1 lb of wheel weight of an 18 inch wheel is equal to 1.48 lbs of payload weight in the car. I don't know where the "4 times" number comes from.

-Mr. Wigggles
"

Landon_Starr

1.48 times. Not 4 times. Definitely not 10 times.


If you cut 80 lbs. of unsprung weight, it's like cutting 120, not 800. Big difference.

Honestly, if it was really that big of a difference, 80 lbs of unsprung weight would drop like 3 secs. off your quarter mile. I'd be ALL about limiting unsprung weight....WHO WOULD NEED ENGINE MODIFICATIONS?

You'd probably see a LOT more innovation/R&D in the area of lightweight wheels, too, if this were the case.

--Landon

shaunv74

My question is what are the performance advantages of each? If a light flywheel or pulley improves your throttle response does that mean you're going to see your straight line acceleration improve?

I would like to know where the best place is to start if I want to improve the low end torque and overall acceleration.

If I bolt on an indy car intake scoop and tuba sized exhaust is it going to drive my gasmileage into single digits too? I read some of the threads on the ECU programming and the results looked promising but the packaging still seemed immature. Are there any good sites that are doing long term tests on the performance and engine life? What would be the best place to start if my goals are more low end and improved acceleration?

rotarygod

Absolutely!!! A flywheel is a very noticable improvement. While technically a light flywheel does nothing to add horsepower it does give you more usable horsepower. In other words while the engine isn't making more power, it is getting more to the wheels. You will definitely notice it.

Landon_Starr

Well put, Rotarygod.

--Landon

shaunv74

I see. thanks RG. So why does the manufacturer not install a lighter flywheel to begin with if it is more effiecient? What are the downsides? I saw mention of reduced drivability. What is meant by that.

rotarygod

People say that a light flywheel is hard to drive on the street. I personally don't find this true at all but I actually can drive good! Seriously though, the lower inertia of a light flywheel will not only cause the engine to accelerate faster but also decelerate faster. Between shifts the rpms will drop a little lower than they would normally. Off the line is the most noticable since it does require a little more clutch slippage to get the car moving. It isn't much more though and I don't feel it is an inconvenience at all. Both of my RX-7's have had the light aluminum flywheels.

Try this, drive around a parking lot in 1st gear. Don't push the clutch in just accelerate and decelerate at a reasonable pace. There may be times you notice the car try to jerk back and forth a little depending on rpms and speed. This isn't a problem if you give it more gas or slip the clutch. This effect will be worse with a light flywheel. It just requires a little different tactic. My logic is that if it only happens when you go slow, don't go slow!

Landon_Starr

LoL. Like when the patient reported to the doctor "It hurts when I do this" and his response: "Well then don't do that!"

I really dig how you apply technical issues to comprehendible real-life experiences, rotarygod, keep up the good work!!

--Landon

shaunv74

Thanks RG. You have a great way of explaining it. I understand exactly what you mean. I'm still a bit ham footed with the clutch and still getting used to the relative touchiness of the tight friction point and low torque so I was looking for something that would give it a bit more bottom end to make it a bit more forgiving and smoother when starting out in 1st and shifting. I guess I'll just have to get better at driving it. Do you find there is a significant difference in clutch life due to having to slip it more with the lighter flywheel?

shaunv74

I have a dumb guy question...

I've read the 13B has cast iron rotors and sideplates. Why don't they make them out of a hardened steel? I would think that would be lighter and still be able to handle the heat and the loads. If anything I would expect it would be better.

Anyone have any info on that?

RodsterinFL

I'm kinda late jumping in on this thread. I read about halfway through.

My dad, an ole stock car racer, has buzzed around with me in the car and we discussed this car at length. He read the Wankel Rotary book for interest and then came up with a few suggestions.

1) change the rear (differential) gear

2) provide AC air to engine intake

3) consider exhaust mod but try others first

4)find out what they are doing with that Mazdaspeed version on the management system


Those are his suggestions. I am not familiar with differential gearing but he said that modifying the rear end would make a BIG difference - effect top speed and possibly MPG but a BIG difference. He recently took his Miata in for service and drove a Mazdaspeed version and loved it. Apparently it has a different rear end gearing too.

rotarygod

The rear end ratio for the RX-8 is 4.44:1. The manual transmission RX-7's ran 4.10:1 and they were considered high ratios. The bigger the number, the better the acceleration. The smaller the number, the higher the top speed.

rexi

Rotarygod, regarding light flywheels I have noticed that their weight varies between approx 9lbs (ACT) and 15lbs for the MS.
Is the 9lb flywheel too light in your opinion and would it affect drivability too much relative to a heavier 15lb unit such as the MS?

The temtation is to go with the lightest flywheel available for best engine response but unsure of the consequences.

Your informed response would be appreciated

Regards
Rexi

rotarygod

ACT quotes the weight of the flywheel without a counterweight attached. The stock flywheel has the counterweight built in which contributes to it's published weight. Numbers like this are sometimes misleading to help sell more product. I'm not sure if the Mazdaspeed unit has a counterweight figured into that number or not.

I use the 9 lb. flywheel on my daily driven RX-7 with absolutely no problems. I love the way it drives. That weight figure is also without the counterweight.

rexi

Thanks Rotarygod

Rexi

shaunv74

I think the rear end has a high enough ratio. If we went higher to improve acceleration the engine would rev at a higher RPM than it already does at highway cruising speeds correct? This would reduce your gas mileage, potentially reduce moving part life, run hotter, yadah yadah. If we take it lower you might gain some top end if the car is not aerodynamically limited but I think ~155 is fast enough. (My opinion) That and with the low end torque the engine has, the car would not accelerate as fast I imagine. Now if people are thinking about FI I definitely think you are right on with changing out the rear end gear. My 5 spd FD ran at a lower RPM at the same speed as my 6 spd RX8! I've read a few threads about rear Differentials failing on people due to bearing retaining rings. If someone has opened up the rear end I'd like to know if they have an uprgrade for this?

I personally am interested in getting some more bottom end in the motor first.