This is still all bs. It is just very easy to believe it when someone is very well spoken and has a "title". Exhaust port location has absolutely noting to do with frictional losses. Because of this we had to ADD 4 seals to the engine. The weight of the rotors are not so much lighter that the frictional losses are different and the seals are so small and few in relation to our piston counterparts that a little better coating on them doesn't do anything noticable. They'd better be more slippery since we have more seals that add friction. A lighter engine revs faster but not because of less friction. These are gains due to lowered inertia.

Oils get THINNER with heat. You need to do some homework on how oils behave. Here's a good site. All you ever wanted to know.

http://www.vtr.org/maintain/oil-overview.html

An intake system that provides too much air for the fuel system is actually known as a poorly tuned car with an improper sized fuel pump. Restricting the intake does not help make more low end power unless the part that is doing the restricting is an acoustically tuned length intake pipe feeding a resonant chamber which helps push more air in a a set rpm. This can be affected by intake pipe diameter or length but is not affected by the air filter and it's ability to flow air. Put a cork in the intake pipe and try to start the car. You should have wonderful low end by these standards.

Either you didn't understand what this engineer was talking about or he didn't understand what he was talking about but it is definitely one of those.

 

anyone else really hate the epa? lol

 

I have trouble believing this is the case...gas + oil doesnt seem plausible - at least not in the context of mixing the two w/o regard. I understand some oil is lost, as it is used in the chambers, but that should be burned away via combustion. Anyone able to enlighten me?

 

Ok folks, we can disagree without attacking. This is a dialog, so let's keep it that way please.

 

This makes for a very interesting read.

What role does this Ford engineer play in the scheme of things? Is he on the actual RX-8 product team, or is he pulling out company memos that pass his way?

 

let me make 2 points before i go back to the original post and dissect it.

1. lets not shoot the messenger here folks. he asked very good questions to a person he understood to be able to provide competent answers. its entirely possible that he misunderstood/misremembers the answers or that the answers provided are incorrect. Maolin dont get bent out of shape when others or myself point out the incorrect parts of what you posted. I thank you for trying when you had the chance.

2. The statement above is incorrect becasue the oil that gets pumped into the rotor housings to lube the seals/chambers does NOT and CANNOT go back to the sump. its is burned or goes out the exhaust. there is no way for it to go back to the sump.

ill get to some other points in a few.

 

I think you're right about the long night. You ARE wrong about multigrade oil - it gets thinner when heated. Viscosity scales are not constant, they are temperature based. A Viscosity of 20 measured at a temperature of 15C is NOT the same as a viscosity of 20 measured at 100C. I am a mechanical engineer, and I could pull out a university lab test conducted by me over 25 years ago measuring viscosity vs. temperature. I can absolutely state that oil gets thinner when it's heated. I can also absolutely state that you've never done ANY sort of experiment to test viscosity vs. temperature if you believe it gets thicker.

Here is your homework assignment for tonight - place 0.5 quart of your favourite 5W20 motor oil in the freezer and let it cool to freezer temperature. Then place an identical 0.5 quart of 5W20 (in a container, of course) in a pan of boiling water and let it get hot. Now take both 0.5 quarts of 5W20 and pour them into different containers. OBSERVE that the hot oil flows much more easily and is much thinner than the cold oil. This proves that oil viscosity gets thinner when it is hot. You will be proving to yourself that you were wrong about your statement above.


There is no such thing as too little friction in an engine. You do know that Mazda specifies 5W30 for the Renesis in every market outside of North America, right? 5W20 isn't some magical number - parent Ford insists on the use of 5W20 in NA only to reduce internal friction by small fractions, to in turn improve fuel economy by small fractions, to improve their overall CAFE rating.

You're confused. EPA2 standards refer to tailpipe emissions, and have absolutely nothing to do with EPA fuel mileage ratings. Further, with respect to EPA2 standards and tailpipe emissions, the original PCM tuning DID easily meet EPA2. However, with the original PCM tuning the catalytic converter lifespan would NOT meet the extended life requirement that was a part of EPA2. This has absolutely nothing to do with tailpipe emissions or EPA mileage testing - in fact, the revised PCM map likely has higher tailpipe emissions (still well within EPA2 requirements), a sacrifice to get the cat. converter life extended to meet the requirement.

Please explain what the wideband O2 sensor is doing with it's active measurement of air/fuel ratio? Wouldn't that be "actively measuring"? Doesn't the PCM actively adjust fuel injection based on O2 active measurements fed back through the programmed fuel maps?

That's enough for now from me. Maolin34, go do the oil experiment to prove to yourself that you wrong. The results are guaranteed.

Regards,
Gordon

 

this has holes that others have pointed. but there is one other point to make. why is 5w20 recommened in the USA but not in other countries? simple answer- CAFE which stands for corporate average fuel economy. this is a US federal standard that each auto maker has to meet a certain product line wide avg mpg. Ford companies as well others have started shifting to thinner oils because they get better fuel economy during the EPA testing than heavier oils. now the answer to why 5w20 and dino oil is recommended and why does every Mazda employee stick to the company line. because whatever oil that is used when the car is undergoing epa testing HAS to be USED AND RECOMMENED FOR USE TO THE CONSUMER. they cant use one oil for testing and then have you use another. its against epa regs. That is the main reason they keep saying dino only. the other reason is that they just do not want to spend the time , money and personnell resources to test the efficacy of synthetic oils. the dino works fine so why bother? its a bottom line bean counter decision.

that's pure nonsense. during city driving you normally stay at lower rpms. if you stay under 3750rpms then you arent opening anymore of the s-dais tracks or injectors. then what you have when open when you start the car.if that is the reason for for alot of people getting 10-11 mpg then that is saying those people never shift out of 2nd gear and its all user error. which we know its not.

true if you go up to 4k and then shift some of those first few squirts of gas may be swept around adding to the rich a/f. but the sensors after will note this a/f and change injector and igniton maps to try to bring it back to stoich in closed loop.

oxygenated fuel does decrease the mpg. but they are use donly during a short period in teh winter in some states. this does not acount for the people who have extremely low mpg all year round. and as i stated before oil that has been in the combustion chamber DOES NOT go back to the sump. nor does any fuel. if either is happening there a more problems with your engine than the mpg. you need a rebuild at least and at most anew engine.
i was going to try to chop this up for clarity but ill do my best. a) no horsepower was lost as a result of the port flash campaign. it was never there. b) the flash at port was done to lower the exhaust gas temps to promote cat longevity. Mazda is nopt the only company to use this method. the coflict comes from different standards between US epa regs and california emissons regs. california rules say the cat must reach operational temp in less than 5 minutes. in order to meet this requirement all car manufacturers started to move the cats closer to the engine to get them heated up faster. then the feds brought a new reg for 2004 and newer cars that says your cat must live to 110k miles and if your cat reaches x degrees it wont so lower the cat temp. the richening at port was done to pass this new req. c)there have been no zero nada flashes designed to increase power. every flash so far has been to deal with flooding issues related to rich a/f and oil metering, while trying to stay within the requirements. there not been 2 flashes since M. the 1st he is thinking of was a change in the nomenclature. this file had a bug which caused a cel. the 2nd he is talking about was the de-bugged file that replaced the 1st. there is no difference in performance between M and these. that is why the updated bulletins say if a car is at M ther eis no need to flash it with this "newer"(differently named) file. there is no memo that says "We are trying to get the horsepower back to those that do not reside in green states." they arent trying and wont because there never was 250hp. now when you go for your reflash on monday find out if he updated his WDS between today and monday. if he did not there is not any flash to be had because his WDS is not on the correct level. there is however a new flash name on a tsb out today. ill have more on that once i get a chance to digest teh tsb.

there was no change to the throttle body, intake or intake manifold for 2005. if any of those parts were changed on future models no flash would help 2004 models because the programmign would include parameters for the new parts that the 2004s wouldnt have.

just plain ludicrous and already answered by others

right and wrong. there is no fuel in the oil as i have stated before. but there is moisture(water) that is condensing out of the oil in the dipstick tube. betting the oil hotter wouldnt help because it woul djust boil the water out faster and with no place to go but up the dipstick its still going to condense there. i cant imagine what their "fix" will be.

 

i took to long to post and gord got to some of my answers while i was typing. thats good tho sincei think it will take more than one of us to sort all of this out. thanks gordo.

 

Wow...I'd sure hate to be Maolin34 right now

 

Thanks - glad to know i'm not crazy, and somebody else picked up on that.

 

Nah, Maolin meant to get some discussion going... and he did just that.

 

if the oil went back, then someone might want to explain why my exhaust is always dirty as hell.

 

While some of the best minds in this forum are paying attention, a semi-steal of the thread...

If gasoline cannot get into the oil the way it is described at the top of this thread, how does gasoline get into the oil? The oil in mine has reeked of gasoline since day one and the dealer (the entire crew) insists that they do not smell anything wrong with the oil.



On another note...
MM, this is actually true for some cars, not the 8 though. Some cars with TPMS do not have sensors in each wheel and determine loss of air by reduction in diameter of the tire and consequently rotation at different speed from the other tires. It uses the DSC (or equivalent) to do the calculations. We all know that the TPMS with sensors isn't all that accurate and these others are way worse. They are totally ineffective when all the tires are down the same amount of psi such as what will happen when the ambient temp drops.

 

if the oil gets more viscus, at higher temps, which I do believe it does, then that reduction in friction, would result in less pressure, against the incomming air.

air -----> rotor wall

Now I know that the rotor is actually sucking the air in, as it turns, but less resistance on the rotor turning, would either create a fraction faster cycle time, thus allowing less air in, or the air incoming would flow in faster, and thus not creating any force against the expansion.

Anyway I'm not making any sense at all .. LOL I guess I'm saying that I can see how the air flow would be affected in some way, by the oil viscosity. Less air = richer mix = poor fuel economy.

One thing that makes sense out of all of this is why 87 octane is actually better than 91 or higher. All fuel has additives, but the way that they increase octane in the the fuel is by adding a little something at station. They add something for mid grade and something else for high grade. I assume they are adding oxigenators, and that Mazda is telling customers to use 91, because it meets the EPA, where 87 doesn't. However 87 produces better fuel economy by leaning out the mixture, and more power also.

 

Hrm so if you had a tire, with low or high air, and its diameter was different than it should be, then your TCS, and DCS could be causing serious problems with Fuel economy.

Someone with bad Fuel Economy, try turning off DCS/TCS, see if it makes a difference.

 

I think you missed a piece of info. Reread the bottom of post # 20

"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."

 

BTW, great topic and discussion.

Best thread in weeks.

As someone who is not "mechanically inclined" and knows squat about rotaries, I really enjoy threads such as this one.

 

Where in Sammamish, WA are you Cam? I grew up there, in Timberline.


Anyway...ya...rotaries and stuff. THis isnt a thread hijack...rotaries....

 

You ACTUALLY believe that oil gets MORE viscous at higher temperatures??? did you not read Gord's post???? I would think most people learn that in Grade 7 science!!! Viscosity is a measure of substance's resistance to flow ... more viscous means thicker (think molasses) and less means thinner (think liquid honey).

It's basic chemistry ... increase temperature means more kinetic energy present in the molecules which makes intermolecular forces (be it polar, ionic, etc) have less of an effect, resulting in lower intermolecular cohesion. This translates into a LESS viscous substance. Increase the temperature some more and you get vaporization and so on.

Heck, I got an even easier experiment than Gord ... get some solid honey and melt it ... what happens??? It becomes more solid??? HELL NO ... more runny which means LESS viscous.

I think you meant to say that oil get LESS viscous, right?

On the other hand, RotaryGod, Zoom44, Gord and other rotary gurus ... how did you guys learn so much about about Rotary Engines ... a secret handbook? I know there are a couple of people who did thesis' (i don't know the plural form) on it here.

 

Ok, I read the site you sent me to....and I bring forth this statement directly from the site above...

"Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot."

End Quote.

It is obvious that oils thin when heated, however, the point of multi viscosity oils is to avoid this problem. Which is why they add the polymers to the oil. In the quote above, it reads "Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot."

By this rationale, we know that a 20 weight oil is thinner than a 50 weight oil when cold. When heated the oil thins...which means that 20 weight would thin to be less than 20 weight when heated. 50 weight oil would also thin, but it would not thin enough to be rated at 20 weight, would it? If that were the case, it would defeat the purpose of multi viscosity oils. Correct me if I am wrong, which everyone seems to be trying tonight..(although I don't take it to heart, as most of this information is not from my head or mouth.) 20w-50 is 20 weight oil when cold, but when heated is only as thin as hot 50 weight oil. So, bottom line question....is hot 50 weight oil thinner than hot 20 weight oil? Based on the information from your site, I would think not.

Lastly if motor oil, and we are talking about motor oil, gets thinner at higher temps, then how in the world could 5 weight oil handle the abuse of a high revving rotary? This paragraph from your reference site also helps....

"Viscosity is a measure of the "flowability" of an oil. More specifically, it is the property of an oil to develop and maintain a certain amount of shearing stress dependent on flow, and then to offer continued resistance to flow. Thicker oils generally have a higher viscosity, and thinner oils a lower viscosity. This is the most important property for an engine. An oil with too LOW a viscosity can shear and loose film strength at HIGH TEMPERATURES. An oil with too HIGH a viscosity may not pump to the proper parts at LOW TEMPERATURES and the film may tear at high rpm."

End Quote.

Now, we know that straight SAE 20 is lower viscosity than SAE 50, right?

Am I wrong?

 

First you said that the original PCM tuning DID easily meet EPA2, then proceed to say that it would not meet EPA2 for cat life. Bottom line, it didn't meet EPA2. It had to be changed.

When I stated that EPA does not drive and fill up to get mileage readings, and that they test at 72 degrees, etc...I neglected to add the part about not trusting EPA ratings for mileage because of this. I submitted a post is another thread about the full mileage, and mentioned this there. My fault on this one.

 

No, I said it easily met EPA2 with respect to tailpipe emissions. I said it did not meet EPA2 with respect to catalytic converter durability.

No, hot 20 would obviously be thinner than hot 50. I don't think that's what you really wanted to ask as the bottom line question?

Your original statement was . That's obviously not true, as you concede above. You now seem to claim that for multiviscosity oils, it still is true in some relative sense? Even then - it's not. Hot 50 oil is still much thinner (less viscous) than cold 20, if that is what you were asking here. If you can find straight weight motor oil, you can still do the freezer/boiling experiment to prove it to yourself.

Regards,
Gordon

 

You were originally. Fortunately you read the link I posted and now understand it.

 

I don't need to prove it to myself. We can argue semantics all night. I made reference to the motor oil that is recommended for the RX-8 which is 5w-20, a multi viscosity oil. I don't concede that a multi viscosity oil is thinner when hot. Also stated on the site were the pour points of a variety of oils, and it seems that this is the point that you are trying to push.

I am simply saying exactly what the site said....

"Viscosity is a measure of the "flowability" of an oil. More specifically, it is the property of an oil to develop and maintain a certain amount of shearing stress dependent on flow, and then to offer continued resistance to flow. THICKER oils generally have a higher viscosity, and THINNER oils a lower viscosity."

5w-20 oil has a higher viscosity at high temperatures, than lower temperatures. Just like any multi viscosity oil, like the recommended oil for the RX-8 which is 5w-20. I guess it really comes down to whether or not 5 weight oil is thinner than 20 weight oil when cold. The answer is yes. And when 5 weight oil is hot, it is still thinner than 20 weight. Does 20 weight oil become thinner than 5 weight when hot? You answered that above in reference to 20 and 50 weights.

"No, hot 20 would obviously be THINNER than hot 50."

Therefore, the oil gets thicker. I suppose we should not be using thinner and thicker, we should be using "lower viscosity and higher viscosity"....it just seems as though low viscosity is synonymous with thinner oil, and high viscosity with thicker oil.

I certainly didn't need the site you sent me to to understand the theory behind a multi viscosity oil. The site only re-inforces the same understanding I had of motor oils prior to...if you want to talk about a straight SAE 20,30,40, 50, then it would be thinner(lower viscosity)after heating, as there are no polymers to prevent the thinning of a straight weight oil.