High RPMs necessary to ensure engine longevity?
03-02-2004, 08:49 PM
#51
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Originally posted by rxphink
Proof is easy if you have ever taken apart a rotary engine that has been driven at low RPM for most of it's life. You will find telltale chatter marks from the seals on the rotor housings.
And as for piston rings, what would you say their purpose is then? Piston rings are there to keep combustion in the combustion chamber and to scrape oil away as the piston moves.
What oil lubrication do piston rings have on the combustion chamber side?
You claim I'm plainly wrong but offer no explination why.
Proof is easy if you have ever taken apart a rotary engine that has been driven at low RPM for most of it's life. You will find telltale chatter marks from the seals on the rotor housings.
And as for piston rings, what would you say their purpose is then? Piston rings are there to keep combustion in the combustion chamber and to scrape oil away as the piston moves.
What oil lubrication do piston rings have on the combustion chamber side?
You claim I'm plainly wrong but offer no explination why.
ring seals seal the combustion chamber, protecting the sump. the higher the pressure in the combustion chamber, the tighter they seal (just like any other gas seal, and analogous to the apex and side oil seals in the wankel). the rings also do scrape off a lot of oil, but slide on a film of it which is consumed during the combustion phase, and replaced during the exhaution phase. they are very well lubricated, on both "sides".
03-02-2004, 08:54 PM
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...ah, i left my computer in the middle of the post for a few hours...
he says "one side", indicating the sump side. there is no lubrication on the sump side, the oil is obviously needed only between the ring and the block, to seal the combustion chamber. i dont' know where you are all geting this "both sides" bullshit.
he says "one side", indicating the sump side. there is no lubrication on the sump side, the oil is obviously needed only between the ring and the block, to seal the combustion chamber. i dont' know where you are all geting this "both sides" bullshit.
03-02-2004, 09:03 PM
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The only evidence I can offer that high reving isn't that big of a deal are the many housings that I have seen with well over 100K miles and are still within spec and can and have been used again.
Wear will take place, but you can pretty much safely assume that it won't matter in the lifetime of your car as long as you do regular maintenance.
Wear will take place, but you can pretty much safely assume that it won't matter in the lifetime of your car as long as you do regular maintenance.
Originally posted by Rotarian_SC
Right now I have only heard evidence that too much high revving causes engine wear, but doing it occasionally is good cause it cleans out anything that might be forming in there. I have also heard evidence that lugging is not good. What evidence is there that a lot of high revving is good, if only revving it high occasionally (8500 three times a week?) will clean the plugs and all the deposits out.
Right now I have only heard evidence that too much high revving causes engine wear, but doing it occasionally is good cause it cleans out anything that might be forming in there. I have also heard evidence that lugging is not good. What evidence is there that a lot of high revving is good, if only revving it high occasionally (8500 three times a week?) will clean the plugs and all the deposits out.
03-02-2004, 09:06 PM
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But don't you have to look at more than the housing. How about the stationary gear, which is mainly what helps determine the redline of a rotary (besides ignition timing). Revving it high causes wear and that is how it sets the redline, so it seems that if you revved high a lot and redlined it a bit the stationary gear would go.
03-02-2004, 10:25 PM
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I've never seen a stationary gear out of spec, and you should always replace the bearings when rebuilding the motor.
For a staionary gear to be out of spec I would expect the engine to have been run without oil or have become unbalanced in some way. If either of these things happen you've got a lot more problems than hte gear. Plus the gear is only a few hundred $, and cheaper still if you join Mazdacomp(Mazdaspeed USA).
The rotors and housings are the most expensive part of a rebuild and hopefully they will never have to be replaced.
For a staionary gear to be out of spec I would expect the engine to have been run without oil or have become unbalanced in some way. If either of these things happen you've got a lot more problems than hte gear. Plus the gear is only a few hundred $, and cheaper still if you join Mazdacomp(Mazdaspeed USA).
The rotors and housings are the most expensive part of a rebuild and hopefully they will never have to be replaced.
03-02-2004, 10:41 PM
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If the stationary gear got out of spec though cause "you made it a point to redline it each trip" then wouldn't that also cause other damage to the engine if the gears wouldn't mesh right, like destroying the seals/leaving chatter marks? Well it is good that there you have never seen a stationary gear out, that means that it is promising that mazda tends more towards the ignition timing to set the redline. I heard that was part of what set the redline in the 8. The rotor was spinning so fast that no more power could be made without advanced ignition timing.
03-02-2004, 10:45 PM
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Well the rotor meshes with the stationary gear and remember it only moves @ 1/3 the speed of the eccentric shaft. The shaft has a bearing between it and the gear so wear there shouldn't be a problem either.
03-02-2004, 11:54 PM
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Pretty much every time I drive the car, I red-line every shift. 5300 miles so far.
I'll keep you guys updated on repairs.
OBTW, 12.2 mpg is best I've gotten so far,
I'll keep you guys updated on repairs.
OBTW, 12.2 mpg is best I've gotten so far,
03-03-2004, 05:48 AM
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Originally posted by Maniac
.... I will cruise at 35 MPH in 6th if I have no throttle needs...
.... I will cruise at 35 MPH in 6th if I have no throttle needs...
Wow, that's only 1750 RPM ....... and no lugging? Can you or anyone else please describe to me what lugging a rotary feels/sounds like?
What is the RPM below which lugging would start occuring (while cruising at constant speed, not accelerating)?
Thanks,
rx8cited
Last edited by rx8cited; 03-03-2004 at 11:44 AM.
03-03-2004, 11:41 AM
#62
Originally posted by rx8cited
MazdaManiac,
Wow, that's only 1750 RPM ....... and no lugging? Can you or anyone else please describe to me what lugging a rotary feels/sounds like? What the RPM below which lugging would start occuring (while cruising at constant speed, not accelerating)?
Thanks,
rx8cited
MazdaManiac,
Wow, that's only 1750 RPM ....... and no lugging? Can you or anyone else please describe to me what lugging a rotary feels/sounds like? What the RPM below which lugging would start occuring (while cruising at constant speed, not accelerating)?
Thanks,
rx8cited
I'm talking about gliding down Rockville Pike in mild traffic that is moving at the limit.
The second I need to move, I go back to 4th or 3rd.
03-05-2004, 03:21 PM
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IMHO we should listen to the engine to get our hints:
1) When it's cold, it sounds rattly, so don't stress it
2) Once warm it has this wonderfully linear torque curve ... It feels like the pressures on the engine are linear from 3500 revs to 9500 revs. I for one think that's fine and using the whole rev range doesn't feel or sound like the car is complaining.
3) The car doesn't sound smooth sub 3000 revs, so I'm sure it's complaining.
4) There are bits of the car (secondary and tertiary ports I think they are called) that only come into action at higher revs. If they are not exercised then I am sure they won't work properly when you need them.
Just a few thoughts.
1) When it's cold, it sounds rattly, so don't stress it
2) Once warm it has this wonderfully linear torque curve ... It feels like the pressures on the engine are linear from 3500 revs to 9500 revs. I for one think that's fine and using the whole rev range doesn't feel or sound like the car is complaining.
3) The car doesn't sound smooth sub 3000 revs, so I'm sure it's complaining.
4) There are bits of the car (secondary and tertiary ports I think they are called) that only come into action at higher revs. If they are not exercised then I am sure they won't work properly when you need them.
Just a few thoughts.
03-07-2004, 09:34 AM
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I feel my car feels smooth even at 2500 rpm.
The mileage thread that I started in the Discussion forum might be able to determine this. If it's lugging, wouldn't gas mileage go down? We can determine the "point of diminishing returns" in the manner that I suggest in my mileage thread.
The mileage thread that I started in the Discussion forum might be able to determine this. If it's lugging, wouldn't gas mileage go down? We can determine the "point of diminishing returns" in the manner that I suggest in my mileage thread.
03-09-2004, 10:41 PM
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You all are probably tired of my observations, being piston-based and Italian and all, but I can't resist:
- there's no quicker way to make an Italian perfomance engine ill than to drive it easy. The term 'Italian tune-up' is common in Alfa and Ferrari service circles and generally means 'drive the car HARD like the owner probably doesn't'.
- performance cars are designed to deliver performance. Our 8's are billed as such and should be employed as such -- the engineers presumably designed them that way (coil packs, possibly, aside.) Long-term, I doubt you're doing the car or yoursefl any favors by lugging it around town. Time will tell.
- I cannot fathom how anyone can keep the revs on this engine under 5K during regular driving after warm-up, much less under 4. The operating parameters of the engine are 1K to 9K RPM...'normal' driving should entail regular 5-6K shifts, with 7+ added for enjoyment and preventive maintenance
- My experience thus far (7100 mi.) indicates the car doesn't like to be driven in the 'diesel range' (1k - 3k) if any changes in velocity are involved -- climbing or descending hills, accelerating or decelerating on flat terrain. There's an element of lash in the drivetrain under 2.5K which just doesn't feel right and can't be healthy.
- The relatively low torque coupled with the high-rev HP, just screams 'high-rev engine.' My only other Mazda (and only previous new car) was a 1988 323 GTX, a piston engine, true, but with DOHC 1.6L, 4 valves per cyl and turbo...the car didn't like to be lugged (I called it 'bogged'.) It drove like new at 70K when family changes made it inappropriate. The only problem ever encountered was when I cooked the spark plug wires being a smartass: I installed Bosch Platinum plugs hoping for some gain -- they leaked where the ceramic met the metal and wrecked the long ends on the wires.
With the 'sweet spot' so high on Mazda engines -- both pistoned and rotored -- isn't it obvious they're designed to GO? If RPMs scare you, get a 'Vette...you'll probably get better gas mileage to boot as GM is highly concerned about fleet fuel economy.
- there's no quicker way to make an Italian perfomance engine ill than to drive it easy. The term 'Italian tune-up' is common in Alfa and Ferrari service circles and generally means 'drive the car HARD like the owner probably doesn't'.
- performance cars are designed to deliver performance. Our 8's are billed as such and should be employed as such -- the engineers presumably designed them that way (coil packs, possibly, aside.) Long-term, I doubt you're doing the car or yoursefl any favors by lugging it around town. Time will tell.
- I cannot fathom how anyone can keep the revs on this engine under 5K during regular driving after warm-up, much less under 4. The operating parameters of the engine are 1K to 9K RPM...'normal' driving should entail regular 5-6K shifts, with 7+ added for enjoyment and preventive maintenance
- My experience thus far (7100 mi.) indicates the car doesn't like to be driven in the 'diesel range' (1k - 3k) if any changes in velocity are involved -- climbing or descending hills, accelerating or decelerating on flat terrain. There's an element of lash in the drivetrain under 2.5K which just doesn't feel right and can't be healthy.
- The relatively low torque coupled with the high-rev HP, just screams 'high-rev engine.' My only other Mazda (and only previous new car) was a 1988 323 GTX, a piston engine, true, but with DOHC 1.6L, 4 valves per cyl and turbo...the car didn't like to be lugged (I called it 'bogged'.) It drove like new at 70K when family changes made it inappropriate. The only problem ever encountered was when I cooked the spark plug wires being a smartass: I installed Bosch Platinum plugs hoping for some gain -- they leaked where the ceramic met the metal and wrecked the long ends on the wires.
With the 'sweet spot' so high on Mazda engines -- both pistoned and rotored -- isn't it obvious they're designed to GO? If RPMs scare you, get a 'Vette...you'll probably get better gas mileage to boot as GM is highly concerned about fleet fuel economy.
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