1 Attachment(s)
Was looking at the Castrol Oil Website and came across this T-shirt Attachment 152577
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Cool.
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Originally Posted by SheffieldSteel
(Post 3456196)
There is more than one standard of what should be put into gasoline (some of them refer to it as "petrol"). Also, there are different ways of measuring the octane rating, and different ratings are common in different markets - just as engines designed in different continents tend to have different compression ratios.
So much for generalities. D'you know specifically how the fuel from the Japanese market compares with that in the US? I don't. But to me it seems reasonable that, when considering what goes on inside the combustion chamber of these engines, the formulation of the fuel might have as much effect as that of the oil. Of course I may be quite mistaken about that, in which case I'm happy to be enlightened, though if possible I'd prefer that not to involve gratuitous profanity. |
I know the big favorites for synthetic oils are royal purple and redline, but does anyone else use castrol syntec?
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Originally Posted by SheffieldSteel
(Post 3456196)
D'you know specifically how the fuel from the Japanese market compares with that in the US?
Big cities with air quality issues are apparently shipped the cleanest fuel, according to the article. All this, as specifed by the EPA. Before anybody says that there are standards, yes there are, but if I recall correctly, the cleanliness had to do with several factors, some of it where the oil was distilled. It got enough attention that one of our Senators started making noise. Not sure what came of it, though. So it would appear that not all gas is the same, even within a given region. |
Originally Posted by invasion08
(Post 3456932)
I know the big favorites for synthetic oils are royal purple and redline, but does anyone else use castrol syntec?
Most Syntec stuff are "Fake" Group III ... except for 0w30 ... only real Synthetic stuff from BP are the "Edge" group ... but it still suck ... |
I know castrol syntec is not a true synthetic, i just asked if anyone else was using it.
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Not to go too far OT, but in regards to octane; a member from Puerto Rico explained to me that the main reason to use high octane fuel in a rotary is that it burns more efficiently and thus produces lower heat in the combustion chamber. I haven't found any other members who have confirmed or refuted this, but it seems logical.
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thats not even close to true.
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Originally Posted by jmc23200
(Post 3462922)
If you use 89 after using 93 for a long period of time, you will hear your engine knock, knock, knockin on heavens door
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Originally Posted by Spirograph
(Post 3462731)
Not to go too far OT, but in regards to octane; a member from Puerto Rico explained to me that the main reason to use high octane fuel in a rotary is that it burns more efficiently and thus produces lower heat in the combustion chamber. I haven't found any other members who have confirmed or refuted this, but it seems logical.
Originally Posted by jmc23200
(Post 3462922)
Higher octane = Higher compression allowed before self-ignition occurs. In a nutshell.
If you use 89 after using 93 for a long period of time, you will hear your engine knock, knock, knockin on heavens door |
Originally Posted by JinDesu
(Post 3462989)
Why do we use 91 octane in the RX-8? To reduce the chance of premature detonation with our oddly shaped combustion chamber.
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Originally Posted by mac11
(Post 3462994)
then why did the old n/a rx7's, with the exact same combustion chamber shape, use 87 octane? And why could you get away with using 87 octane in a TII running stock ~6lbs of boost?
Should we use 87 octane just because RX-7s were able to do so? Well, that's up to you, isn't it? |
Originally Posted by JinDesu
(Post 3463000)
I did not say our oddly shaped combustion chamber does prematurely ignite with 87 octane. Can it? Sure!
Originally Posted by JinDesu
(Post 3462989)
Why do we use 91 octane in the RX-8? To reduce the chance of premature detonation with our oddly shaped combustion chamber.
but per, you...
Originally Posted by JinDesu
(Post 3462989)
If your engine was capable of using 89 without knocking beforehand, using 93 and then going to 89 won't change the fundamental characteristics of your engine.
So guess wildly again as to why higher octane fuel may be considered for use in the Renesis. |
Alright - I apologize if I came off as explaining why the RX-8 uses 93 octane incorrectly. I stepped in only to explain the difference between octane levels - energy required to detonate it. By saying "oddly shaped chamber", I mis-spoke.
Here goes my wild guess: Why does my Renesis use 93 octane? Because I've heard that our knock-sensors are useless. Does the RX-7 have better knock sensors? I don't know, I don't have an RX-7. To my knowledge, the improvement of power from using higher octane levels is not the octane itself, but the tune. By fine tuning the fuel combustion process to an exact degree, we get the maximum power from it. Higher octane gas, with their ability to resist premature detonation, is critical to it. That was the only point I originally wanted to make. |
Originally Posted by JinDesu
(Post 3463016)
By fine tuning the fuel combustion process to an exact degree, we get the maximum power from it. Higher octane gas, with their ability to resist premature detonation, is critical to it. That was the only point I originally wanted to make.
Since I see we are getting no where.....the renesis has 10:1 compression. |
Originally Posted by mac11
(Post 3463019)
The tune isn't ragged edge enough to make a difference in detonation. I run 87 octane all day long in the summer.
Since I see we are getting no where.....the renesis has 10:1 compression. |
Originally Posted by JinDesu
(Post 3463026)
Higher compression = lower octane spontaneously igniting :dunno: is that what you're getting at?
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No, but I've always overlooked the simplest things =\
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I have an RX-7 and I run only 87 octane. The car loves it. Why does the Renesis not like lower octane? Simple. Tuning. It's not the compression ratio. 9.7:1 in my car and 10.0:1 in a Renesis is not enough to matter. Back timing off a few degrees and the Renesis could burn it just fine. Incidentally the Renesis runs more advance than my car does. Max advance at full throttle for me is 26 degrees. It's 30 for a Renesis. Max advance under light throttle/cruise for me is about 36 degrees. For a Renesis it's in the 40's. See the correlation?
It really comes down to emissions. Each octane burns at the same speed. A higher resistance to detonation means that timing can be adjusted to burn it longer which means cleaner. Not necessarily noticably more power although a little is probable. Flame front travel takes time. You want it expanding at it's max rate as the engine is passing TDC. However due to flame speed we need to light it earlier than that so that it reaches peak pressure around then. If there is a propensity to detonate we can't ignite it this soon. This means we'll waste a little bit on the back side hence the "little" amount of probable power gain but more importantly it was this small extra amount of time to get more of the fuel and hence emissions burned off. A hp or two doesn't really matter but when it comes to emissions, every gram does. Based on flame speed we can see that for every fuel only so much octane is useful in any certain engine configuration. Above that it doesn't help anymore. It of course is different for boosted or nonboosted cars, different boost levels, etc. |
Originally Posted by rotarygod
(Post 3463276)
I have an RX-7 and I run only 87 octane. The car loves it...
I am not asking to save money on gas. I have always heard that too much octane leads to carbon buildup. Also, if it is true the engine runs cooler with higher octane, my engine runs too cool during the winter (massive condensation in my oil even though I don't drive short trips and I have my oil coolers covered). |
Older n/a rotaries always loved low octane. They were tuned for it. The tag on my gas door states 87 octane or higher. Times have changed and so have emissions regulations. On a turbo rotary I wouldn't be inclined to use 87 octane although you could if stock power levels were kept. Many rotary race teams used to use low octane. Today they use 96 per the rules.
Higher octane shouldn't have any affect on carbon buildup. Technically the reverse would theoretically be true although I doubt it's measureable. Octane also shouldn't affect the heat rejection properties of gasoline. One thing that I'm surprised that no one has tried is a water separator in the oil system. It wouldn't be hard to do. It would just look like another oil filter mounted somewhere else. Although typically used in diesel fuel systems, diesel fuel really is just a light oil so I don't know why it wouldn't work. I'd love to see it at least tried. |
I would probably say no to that.
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Originally Posted by jmc23200
(Post 3463008)
Originally, the RX8 manual said 87 gas was fine. The RX8 uses 93 because some RX8 owners in 04 where experiencing knock. It was easier for Mazda to say use 93 then to explain if you have knocking use higher octane fuel.
I do believe using 93 for long periods of time and then using a low octane ga will cause some knocking. Why do I believe it? It happened to me. After I reset the removed the room fuse and reset the fuel trims, it was able to compensate faster and I did not get the knock. the 04 manual just say premium is recommended.. and performance will be reduced if you dont use it.. :) and correct on you comments about ltft.. my car drives daily on 87. no knock no problems. always has.. has put down some good dyno #s on it also.. but for track events.. 94 and pull the room fuse.. safety! :) beers :beer: |
Originally Posted by rotarygod
(Post 3464489)
One thing that I'm surprised that no one has tried is a water separator in the oil system. It wouldn't be hard to do. It would just look like another oil filter mounted somewhere else. Although typically used in diesel fuel systems, diesel fuel really is just a light oil so I don't know why it wouldn't work. I'd love to see it at least tried.
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