brillo

Ok, since Rotarygod (Fred) and I are going to be at Sevenstock, we were trying to jot down good questions to ask the Mazda/Racing Beat/Downing/Other important people folks that may be speaking at the event. I wanted to get some input from the forum on questions other members had I might not have thought of.

We know already they will not comment on future products, so please don't post the following:

1. When is the next RX7 coming out?
2. When will we get the Mazdaspeed 8 ? / Will it have a turbo/super etc...
3. What changes to the RX8 will be made for 2006?

ok, with that out of the way, what questions about current products, designs, engineering, philosophy etc.... do you guys have?

My current list is as follows:

1. Since the RX8 is a NA car, why not run negative split through the entire RPM band rather than idle?
2. Why has it taken so long for direct injecton to come to fruition on the rotary?
3. Why is the current engine still using iron housings?
4. Why not go with a taller 6th gear for better mileage on the manual cars

I'm going to come up with a priority list tomorrow, so please add your questions to the thread.

8is>enuff

In #4, do you mean taller? We're already at ~4k at 80mph.

I'd like to ask them why they grouped the radio/climate control/etc. all together. Aftermarket radio installs are a bitch.

And before someone beats me to it, ask if I can have the phantom 247hp flash. :D

tuj

He means shorter numerically, which results in a taller gearing.

I would ask: what exactly did they change when they reflashed the cars at the port supposedly to make the cat. last 100k miles? Did someone screw up and not test the cat. life? Why not just use a different cat?

How are the people who have cracked the ECU tuning it? How did they manage to crack it? I am well-aware of the efforts in the Subaru / Honda / etc camps at disassembling the code and suspect that this is not how the RX-8 ECU was cracked / modified.

What are the gains seen from porting + proper tuning on a Renesis?

Will we ever see a true Renesis racing in ALMS? Three-rotor Renesis? Four-rotor?

How much gain does the DBW throttle add?

Nubo

What is the story on the Las Vegas engine failures?

Once, and for all, what is Mazda's definitive stance on synthetic oil in the RX-8?

Why is the RX-8 marketing effort so weak?

zoom44

there are only 2 ways currently. The "Racing Beat path" is to go thru a flash in hex and find all the things you want to take control of and make changes. i wrote elsewhere about their progress.

The "Astra Racing path" (and the path of the japanese tuners) is to remove a chip from the board change some jumper and then use a program called carwaves(available for free from the astra racing site) to manipulate the data. They also had a company help them with a check sum problem. this method isnt exactly end user easy.

no one has access to the Mazda way of making flashes except Mazda.

r0tor

iTrader: (1)

The only advantage of DBW throttle is flexibility of leaving the ecu to control the throttle for traction/stability control and in certain limp mode situations.

tuj

I disagree. Progressive throttle opening during acceleration maximizes intake velocity, assuming it was tuned that way. There is an ideal throttle position for every rpm that will maximize acceleration, and that position is not WOT. It also supposedly increases fuel efficiency. Why would the ECU need control of the throttle for either of the applications you describe when it already controls spark and fuel?

rotarygod

tuj is on the right track. In order to do the progressive type of intake that the RX-8 uses, they had to use a DBW. The older rotaries used a 3 plate throttle body setup that kept the primaries and the secondaries completely independent of each other. The dynamic chamber (plenum) of those engines were essentially dual plane where the secondaries collected in one part and the primaries in another. The primaries were fed by only 1 throttle plate while the secondaries were fed by 2. The secondary throttle paltes were mechanically linked to the primary plate and were adjusted to begin opening at 20% throttle. This meant for most cruising speeds only the primaries received air and they did it through a small throttle plate which maintained a smooth and linear throttle response. As the driver pushed the pedal down past 2-%, the secondary plates start to open adding their total area to the breathing capabilities of the engine. The only problem with this technique was that they would all open regardless of rpm if more than 20% throttle was used. This caused a little power decrease in the low end.

Along comes DBW technology. Suddenly mechanical limitations are no longer an issue. We can use only 1 throttle plate now since it isn't directly tied to your foot. The Renesis intake is a more refined version of the original intake concpet from the nonturbo RX-7's from 89-91. This time a valve is placed inline to the secondary plates to keep them closed and individual runners were given to all intake ports. If only the primary ports are open at low speeds, that isn't much intake area. If we open the large 75mm throttle plate even part way, it is easy to see that we would have max total usable airflow through those ports. It would do this at a very narrow range of motion on a throttle plate this large. Fortunately the DBW knows this and only allows it the neccessary range of motion. It decreases the total range of motion per the amount of input from your foot. This keeps throttle response smooth and not overly touchy. Farther up the rpm range, the secondary ports open now, not dependent on throttle position but more appropriately on rpm and the DBW once again continues to compensate total airflow potential with total airflow requirements. As the rpm's rise, the actual range of motion of the throttle plate gets more and more proportionate to the amount you are pushing down on the pedal. This is the perfect setup and maintains a very smooth driving vehicle. Yes traction control also kicks in that way but this is just a bonus. The Renesis intake system could not function nearly as smoothly as it does if it didn't have DBW.

rotarygod

My biggest question that I'd like answered is how does brillo's hair actually look like a brillo pad?

rkostolni

I would also love to know
1. The true reason for the HP drop.
2. Mazda's thoughts on sythetic oil

rotarygod

1. They'll never provide an answer to that. The car meets it's performance goals anyways which makes power numbers on paper irrelevant. It has to have somewhere around 238 to do what it does.
2. Would anything they say really solve anything? If they say not to use it, they do it themselves so it must be good and they are just contradicting themselves. Add to the fact that many others use it with great results and it suddenly doesn't matter what they say. Results are all that matters. Not who says what. If they say it is OK to use, no one will believe them because they keep changing their stance. It's a catch 22 for them.

RotoRocket

iTrader: (1)

Here's mine (some have already been asked, so consider these ones for emphasis):

1) Is synthetic oil appropriate to use?

2) Is any oil with a greater weight than 5W-20 appropriate to use?

3) What can be done to improve the air conditioning systems cooling capacity?

4) What can be done to improve fuel mileage?

5) Is an all-wheel drive version of the RX-8 on the drawing board?

6) Why is the oil dipstick in such an awkward to reach place, especially considering how vital it is to regularly check the oil level?

7) Wouldn't making a spare tire (at least a temporary) be a good idea?

Thanks.

tuj

Its an option when you buy the car. But honestly, I don't know why you'd want one, if only for peace of mind I suppose. The frequency of flats has gone down dramatically with modern tires, and of those flats, most can be fixed with the mobility kit in the car. Sure a sidewall puncture is going to have you sidelined, but its a gamble I'm willing to take. Of course, I had a Miata before this car, where the first thing you ditch is the spare to get some trunk room. I think spares are going to be a thing of the past.

tuj

Maybe Mazda should start doing like Rolls Royce used to and simply list power as 'adequate.'

r0tor

iTrader: (1)

If you control fuel and spark without controlling the throttle the car will go extremely lean, which might be OK short term but not ideal in the long term.

I also disagree on performance benefits.

Most cars using DBW have horrendous throttle reponse, often lagging or falling completely on its face when given sudden jabs of the throttle - like our Mazda 6 for instance which personally drives me completely crazy. You hit the gas and wait a full second until anything happens. Many other cars with DBW have similar problems including Mini's, Subies, GTO's, and a few others I've come across. Its very rare for cars to get any increase of response when switching to a DBW system. Luckily the throttle on the 8 feels much more like a throttle cable.

then you check out why drive-by-wire was invented to begin with in F1 and it all makes sense. They were after traction control, launch control, and the ability to take throttle control away from the driver momentarily to give better driveability and limit the amount of power and how it comes on to match traction comming out of turns. This was never something that was intended to give more power as a throttle can't get more then 100% open.

http://www.grandprix.com/ft/ft00280.html

tuj

Ok, well that just doesn't make any sense. You can indeed provide traction control with only spark and/or fuel control. Retarding the timing, or selectively cutting spark, or going way rich will all cut power.

You've missed the point. The engine can only flow so much air at any given rpm. If you let in too much air, the cylinder/rotor will fill completely, and then reversion will occur and air will start flowing backwards back into the intake manifold. Coupled with the SDIAS, electronically varying the throttle position actually adds power by maximizing the velocity of the air entering the engine with respect to rpm. The DBW does not increase peak power, but it does increase power delivery, particularly at low-mid rpms during full acceleration. My question was as to how much the DBW helps the powerband. Its effect may or may not be great, but that doesn't mean it doesn't exist.

Further, the system controls the throttle based on constant, acceleration, or deceleration strategies. This increases fuel economy, and smooths out throttle response, especially on deceleration. Remember, most conventional throttles have a damper mechanism to prevent jerkiness, as well as a non-linear linkage.

DBW is already on lots of cars that people consider great, including the NSX and the C5. Its all about implementation.

Red Devil

The question about why the dipstick is so hard to get at when it is so imporant is a really good one. When the engine is hot, I find it virtually impossible to check the oil without using gloves to shield my skin from the hot surfaces.