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Series I Tech Garage The place to discuss anything technical about the RX-8 that doesn't fit into any of the categories below.

oil

Old Sep 24, 2008 | 05:14 PM
  #51  
mike01's Avatar
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From: SE Michigan
Originally Posted by Brettus
soif you have a warranty claim are you going to blurt out that you used an oil they didn't recommend ?
Absolutely not, but if they ask to see receipts for oil changes and they look up the UPC codes on the receipts to verify the correct oil was used they could theoretically tell. Maybe I'm just over-thinking the whole issue and being paranoid due to bad experiences with the dealer in the past.
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Old Sep 24, 2008 | 05:37 PM
  #52  
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From: Planet Earth
Originally Posted by mike01
Absolutely not, but if they ask to see receipts for oil changes and they look up the UPC codes on the receipts to verify the correct oil was used they could theoretically tell. Maybe I'm just over-thinking the whole issue and being paranoid due to bad experiences with the dealer in the past.
Unless they can proof the cause of failure was the oil weight itself. (which is impossible)
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Old Sep 25, 2008 | 09:56 AM
  #53  
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From: Eastern Ontario
Originally Posted by Huey52
Actually, there's no thermal energy imparted by the microwave (RF) energy itself, but rather by the excitation of the water atoms/molecules themselves, but I see where you're [trying to] go here.

I've been discussing the relatively low thermal mass of our rotary engine, compared to a similarly HP-rated piston engine, and its effect on fuel efficiency. Volumetric vs. thermodynamic efficiency. A different can of worms.
Fair enough - correction: For similar RF energy inputs into two bodies, similar levels of thermal energy will be induced in both, and the smaller of the two will get hotter.

Our engines are less efficient than the piston variety because rotaries have a larger surface to volume ratio in the combustion chamber. The burn in a rotary quenches over a relatively larger area as it reaches the wall. To get a given amount of energy at the flywheel, you need to burn a given amount of gas. To burn the same amount of gas in both engines, you need to introduce more in a rotary because less of it is burned.

For the same amount of gas burned, you get similar amounts of heat lost to the engine mass. Since the rotary has a lower mass, it tends to get hotter. I assume we have oil coolers for that reason.

This is how I see it. It would be interesting to hear your reasoning as to why the lower 'thermal mass' of a rotary causes it to run cooler.
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Old Sep 25, 2008 | 10:14 AM
  #54  
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Sorry, don't have the time to render an epistle on internal combustion engine thermodynamic (vs. volumetric) efficiency, but again there is plenty of substantiating data out there. The unfortunate truth is that despite the wonders of high power output for its mass, our rotaries get poorer gas mileage. But I gladly (well, kinda gladly) pay that concession for all the fun handling the RX-8 provides.

Originally Posted by Delmeister
Fair enough - correction: For similar RF energy inputs into two bodies, similar levels of thermal energy will be induced in both, and the smaller of the two will get hotter.

Our engines are less efficient than the piston variety because rotaries have a larger surface to volume ratio in the combustion chamber. The burn in a rotary quenches over a relatively larger area as it reaches the wall. To get a given amount of energy at the flywheel, you need to burn a given amount of gas. To burn the same amount of gas in both engines, you need to introduce more in a rotary because less of it is burned.

For the same amount of gas burned, you get similar amounts of heat lost to the engine mass. Since the rotary has a lower mass, it tends to get hotter. I assume we have oil coolers for that reason.

This is how I see it. It would be interesting to hear your reasoning as to why the lower 'thermal mass' of a rotary causes it to run cooler.
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Old Oct 8, 2008 | 09:33 AM
  #55  
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From: Vermilion Ohio
what are your guys thoughts on using a heavier weight like 10W40 or 20W50 as the pervious rotaries have used? i've used the mfr's specified 20W50 all summer long for 10 years in my RX-7's without a problem.does the renesis have THAT much tighter internal tolerances requiring a thinner oil or are they wanting to use 5W20 for fuel mileage and cold start aiding?
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Old Oct 8, 2008 | 10:01 AM
  #56  
Riken's Avatar
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From: Rocky Mount NC
5w30 ftw
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