Spoke to Mazda Engineer.....
 

Ok, I spoke to a Mazda engineer today about several things and learned alot of interesting things... I'll do my best to get everything in, so be ready for a slightly long post.

1) Oil- I was told never to use synthetic in a Renesis. Why?

Synthetic oil is TOO slippery. Friction in the Renesis has already been significantly reduced over the old engine. The slicker oil apparently reduces compression, and will cause the burning of more oil. The recommendation was to stick with conventional 5w-20 oil. Do not use anything thicker, or thinner if they made it.

2a) Mileage- Why is mileage so low, and so variable between cars?

The intake system on the Renesis is extremely complex. When able to cruise at a steady speed, the instake system remain in one state. During city driving the rpm varies so much that there is never really a consistent flow of fuel or air.

2b) Then why have such a complex system?

The design of the system was needed to develop to high horsepower from small displacement, as well as the unusual design of the rotary engine. There are apparently so many variables that need to be taken into account when the engine revs from 1000rpm to 9000rpm. During the rise in revs, I am told, that over 50 different actions take place...not just what is laid out in the S-DAIS diagram. For example, at 3750rpm when the extra fuel injectors come online, the air/fuel map changes independent of the extra injectors, at the same time the ECU is also adjusting for air temp, air volume, engine temp, and throttle position. If you try to baby your car, and shift at 4000rpm that spray from the additional injectors was wasted, and most likely is recirculated to the next combustion cycle, which the ECU does not account for. It does not actively measure, and is not able to measure this fuel from the previous cycle. If it had, it might change the cycle of the primary fuel injector to reduce new fuel being sprayed, but it doesn't. This one reason why fuel economy during city driving is significantly lower....but there's more.

The type of fuel additives has an adverse effect on mileage. Mainly, ethanol, or any of the "nol's". The addition of ethanol or other oxygenates is required by the Clean Air Act, however, it really doesn't work. The Act is outdated. It made a difference when the countries fleet used carburetors, now with fuel injection it is far cleaner already. The oxygenates have an adverse effect on fuel mileage, and price. The use of oxygenates cools the burn during combustion in an attempt to keep exhaust tempratures down, this alone causes a few additional problems...for many engines, and especially the rotary. First, the oil temperatures remain lower which would seem like a good idea, however too low is not good. The oil is thinner at lower temps, and like synthetic oil causes reduced compression. Therefore, unburned gas escapes the chamber and is mixed into the oil reducing its life, and causing the build up of acids in the oil....not good. second, specifically to the rotary, the fuel map which happens to be too rich (i'll get to that) is already cooling the burn by adding too much fuel, add oxygenates and the problem worsens. More fuel is wasted, and your oil is destroyed so much faster.

3) Why is the air/fuel mixture so rich?

The RX-8's fuel map is very rich almost everywhere in the rev range, some places it is lower, but even then it's too rich. Some of you may notice the soot on your exhaust tips. Mazda made the fuel map rich to reduce exhaust temps to meet EPA2 standards. The EPA commonly tests the engines in perfect conditions, 72 degrees, dry air, etc. They do not do drive it and fill it up testing to determine the EPA fuel mileage rating. As a result, a Honda might be accessed a lower mileage rating than it actually will get, and the RX-8 receives a rating higher than it will get....so let's leave the EPA ratings for the RX-8 out of it. There was a big problem when the first shipments of RX-8's reached the ports in the US. They did not meet EPA2, so they all had to be reflashed quickly to be allowed onto US soil. This was a very costly issue, and time was a factor. The reflash richened the mixture up significantly, and hence early buyers lost the claimed 250 hp. Mazda has sense begun to try to creat new flashes to step the air fuel mixture to a better level to acheive better performance. It will happen. I have confirmed with the engineer, and the tech at my dealership that there have been 2 flashes since the M flash. The words from the memo from Mazda say "We are trying to get the horsepower back to those that do not reside in green states." California owners have a completely different setup in terms of the program, as would any other state that has smog regulations. "The power will be back for most owners." was stated. Mine is schedule for reflash on Monday, I will post the results and and the revision nomencalture.

4) How can they make a Mazdaspeed version with more power if they can't stick
to the 250 hp claim for the 04 model year?

The new RX-8's, possibly 05, and MS version will be employing some different components. The "throttle body" is modified, and other intake and ECU changes are being made. They will not do a mass recall of 04 models to replace TB's or other parts, but they will get a ECU flash that will get the power back.

5) My stock air filter is cotton, why is the replacement paper?

The first answer was cost, but the second was to reduce airflow. Reduced airflow will tune back the full map based on volume. If there is less air flowing in, less fuel must be used....and apparently it works. I will be installing the new paper filter this weekend. Will post results.

6) Why the creamy residue on the dipstick?

There are couple of reasons. First, mazda acknowledges that it is a problem, and is working on a fix. That said, the first reason for the problem is the rich mixture which reduces oil temps (oil coolers are not helping), with the lower oil temps the unburned fuel in the oil separates and produces moisture. This moisture "vents" to the dipstick tube which does not get hot enough. They considered making the dipstick tube shorter, but it would make access even worse than it is already. They won't do it. So, the hope to kill several birds with one stone by fixing the fuel map. Running leaner in terms of fuel will bring up horsepower and torque, increase combustion temps, reduce unburned fuel and increase oil life. Allowing the oil coolers to do what they were initially meant to do.

There is much more to say, but if you have specific questions, I can try to anser them in this thread or via private message. Sorry for the long post, but the info was too good not to share.

Interesting info thanks for sharing . :cool:

cheers
michael

The synthetic oil part is pure bs. That's not the reason that they have recommended not to use it. The Renesis does not have less frictional loss than the older engines. I'd love to see some proof of that. The bearings are essentially the same, there are still only 2 of them, and the Renesis has actualy added a total of 4 more seals over the older rotaries which also contribute a smal amount towards friction. If there is any less frictional loss, it is only due to the thinner oil and not any internal design differences.

Most of the rest as far as how the intake and ecu works is common knowledge here.

Where'd you meet this guy? Say it wasn't at a dealership.

Hmm...very very interesting--I know the product run is long for the RX8 so I anticipate these things to come to fruition.

Not true........Oil is thicker at lower temps.......viscosity decreases as temperature increases......it's an inverse relationship :eek:

So changing the air filter to a more restrictive one will increase my mpg's? Will it decrease the power in turn or is it thought to reduce the air just enough to cause the injectors to pump the right amount of fuel so there isn't any left over to cool the exhaust gases? Also, I am assuming that all this info works for the manual transmission. What about the automatics? Will Mazda reflash these cars to obtain their orginal power as well? Or are we SOL as far as that goes?

Even still--if they retune our autos to 210HP we may or may not feel the added 13HP. Either way its a plus--and I'd assume that the autos will be reflashed as well--the power is gone towards ecu tuning.

So there are more significant changes to the 05'. When do they actually start the modifications? All 05' or starting from certain date? This concerns me since I am about the buy an 05'.

Define "slippery".

Based on the answers to the first two questions - that Mazda "engineer" certainly was NOT a mechanical engineer. I agree with Rotarygod, both answers are BS. Thus, I'd not believe anything he said after that. Sorry you wasted your time. Actually, I'm sorry HE wasted your time!

Regards,
Gordon

This implies oil gets mixed with gas, then introduced back into the oil supply. Doesn't make a lot of sense...anyone else read into this as such?

Raise the flag.............it's starting to smell...........

Maolin34-great post. Thanks for all the good info. Just got my paper air filter yesterday, will install after x-mas.

Whoo, boy. :rolleyes:

You should have stepped away from the keyboard after you tried to convince us that the DSC/TCS system is tied to the TPMS.

Let me get this straight, a worse flowing air filter will help you get better gas mileage? Which part off all of that sounds wrong? I'm not going to choke myself while I'm running a marathon because it will help me conserve my breath and go farther. That makes no sense. Less air and less fuel is less power. It takes a certain amount of power to hold a certain speed.

Holy crap, Mazda please hire me! I'm a genious by comparison to this "engineer".

This just in, don't use KY jelly for all your "lubrication" needs. It is too slippery and the last thing you would want to combat frictional losses is lubrication that is too good. Molasses may be a better choice since the current generation of humans is inherently more slippery than our elders.

Good one rg :)

Where do I begin....going to be a long night.

I'll start with the easy one... Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil. You will hear them referred to as multi-viscosity, all-season and all-weather oils.

For the RX-8, which calls for 5W-20....5 weight when cold, and 20 weight when hot. If motor oils thinned when hot, they would not cling to moving parts, especially those moving at high rpm. Motor oil gets thicker when it's heated.

[QUOTE=Maolin34]
2a) Mileage- Why is mileage so low, and so variable between cars?

The intake system on the Renesis is extremely complex. When able to cruise at a steady speed, the instake system remain in one state. During city driving the rpm varies so much that there is never really a consistent flow of fuel or air.

2b) Then why have such a complex system?

The design of the system was needed to develop to high horsepower from small displacement, as well as the unusual design of the rotary engine. There are apparently so many variables that need to be taken into account when the engine revs from 1000rpm to 9000rpm. During the rise in revs, I am told, that over 50 different actions take place...not just what is laid out in the S-DAIS diagram. For example, at 3750rpm when the extra fuel injectors come online, the air/fuel map changes independent of the extra injectors, at the same time the ECU is also adjusting for air temp, air volume, engine temp, and throttle position. If you try to baby your car, and shift at 4000rpm that spray from the additional injectors was wasted, and most likely is recirculated to the next combustion cycle, which the ECU does not account for. It does not actively measure, and is not able to measure this fuel from the previous cycle. If it had, it might change the cycle of the primary fuel injector to reduce new fuel being sprayed, but it doesn't. This one reason why fuel economy during city driving is significantly lower....but there's more.

The type of fuel additives has an adverse effect on mileage. Mainly, ethanol, or any of the "nol's". The addition of ethanol or other oxygenates is required by the Clean Air Act, however, it really doesn't work. The Act is outdated. It made a difference when the countries fleet used carburetors, now with fuel injection it is far cleaner already. The oxygenates have an adverse effect on fuel mileage, and price. The use of oxygenates cools the burn during combustion in an attempt to keep exhaust tempratures down, this alone causes a few additional problems...for many engines, and especially the rotary. First, the oil temperatures remain lower which would seem like a good idea, however too low is not good. The oil is thinner at lower temps, and like synthetic oil causes reduced compression. Therefore, unburned gas escapes the chamber and is mixed into the oil reducing its life, and causing the build up of acids in the oil....not good. second, specifically to the rotary, the fuel map which happens to be too rich (i'll get to that) is already cooling the burn by adding too much fuel, add oxygenates and the problem worsens. More fuel is wasted, and your oil is destroyed so much faster.


If this is true then Mazda then Mazda knowingly released a vehicle with major problems. They must know that these additives are used in much of the US.

The reduction in friction came from a few different things. One, which was the major technological change in the Renesis...was the relocation of the ports to the periphery of the rotor chamber. This allows for a full seal at each point. The seal material has been improved by impregnating with a coating that reduces friction and increases life. The second, was by reducing the weight of the rotors themselves. In this case, the Renesis is designed to maintain a certain level of heat, and handle it far better than it's predecessor that required additional fins, and larger flow capacities for coolant and oil through the chamber walls....barely sufficient to keep it cool. Probably in the case of high oil temps from cooling the turbochargers.

No, I did not meet him at a dealership, I met him at the Ford Product Development Center in Dearborn, MI. My stepfather thought I might enjoy talking with the Mazda team that was there this week, especially given that I have an RX-8 and lots of questions.

What this say's is that unburned fuel is mixed with the oil that makes it's way back to the oil pan. That is correct. It's not good, and as I said it has a detremental effect on oil life.

In the case of the Renesis, the friction losses have been reduced enough in Mazda's mind that the use of synthetic oil is not needed. Furthermore, given the cost of synthetic oils and the measure in which the Renesis burns through it, it would be a Con in terms of new buyers.

When I said "too slippery", the implication based on the context it was used in....

Too much of the oil is able to make it past the seals. The oil then absorbs the unburned fuel and proceeds to "mix it in" with the rest of the oil promoting contamination and poor oil life. That was the explanation.

[QUOTE=Howard]
Initially I would say no. We should remember what is causing the problem in the first place. Not say that Mazda is not responsible...they are. They screwed up. Their failure was not ensuring that powertrain in it's production form did not meet EPA 2 standards. That's it. All of the problems that people are having in regards to mileage, rough running, stalling, flooding, etc. can be attributed by Mazda's forced reflash of all US bound cars within weeks or months. The engine is more than capable of developing the previously claimed 250hp, but not with the current fuel map. With the current fuel map, it meets EPA 2 standards. The use of oxygenated fuels will have an effect on most engines...it is especially hard on the RX8, it's rotary engine, and especially it's over rich fuel map.

I think that the best way is to use a similar situation as an example. One would think that a free flowing exhaust system will always yield more power, but that is not always true. In many instances removing the backpressure that a stock exhaust may create will have an adverse reaction on hp and torque. It is so often that people by high performance exhaust systems without the big picture in mind.

Higher flow is typically needed when you have modified the engine that will use that exhaust system. If you add forced induction, you will definately need to free up the exhaust. Once you find a way to get more air in, you have to get it the hell out....or the performance will be lost. In this situtation, it is a similar issue. The entire system was designed together. The intake, engine, exhaust....and the fuel system that runs it. When the fuel system was forced to change outside of the predesigned configuration or specs, the entire system was affected.

So, the intake system may be supplying too much air for the fuel map. It's just not in the correct range anymore. Hopefully Mazda will fix the PCM flash for us, and we can have our horsepower back.

Until they fix our maps you can buy one of these and fix it yourself :)

cya
Cel