samakijoe

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Most say that it's a good idea to run the engine at WOT for a
short time once in a while. I put mine (AT) in 2nd gear and run at 7+K for
a short time. (about every 2 trips)
The question here is what is a consensus as to how long and often to run at 7+K? .
Any thoughts???....
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Loki

iTrader: (1)

Rpm isn't the goal, high chamber pressure that comes from full throttle is. You just get into high rpms as a side effect. If you had a manual and had valves that open past 7600 you would want to exercise them, but with an AT, there's no real reason to go to redline.

I do mine in 2nd or 3rd at highway speeds so you sustain high pressure longer without bouncing off the rev limiter. Onramps, that sort of thing . Track time helps

samakijoe

I'm sorry Loki but your response doesn't make any sense. The issue here is the engine. Not the transmission.
I'm well aware that the majority of the young folks here think an AT RX8 does not have any credibility within the speed jockies set here.
That's just nonsense. The fact that my left foot can go to sleep while driving doesn't make any difference to
what the engine is suffering from what I'm asking it to do. I use the paddles to run through the gears quite often. Much like the sequential manual transmission
in use in a lot of state of the art big time race cars. Yes my paddles are a lot slower but these guys using these sequential equipped race cars
can also let their left leg all a sleep. So get over it, OK???
Why do you think I am not able to put my car into 2nd gear when I going on to an "on ramp" and I can leave it there for as long as the guys
who have to make use of their left foot. Oh, you know what, my left foot is still asleep...............
I have been driving stick shift cars for over 60 years, mostly Alfa Romeos.
I went this rout (AT) because of the increase patterns of traffic in the city. Not because of my age or skill level.
I Still have a 1974 Alfa Romeo spider in the garage that gets exercised often.
So I'm still looking for some information on carbon removal in a rotary.........................
Anyone?...............................

Loki

iTrader: (1)

I'm not sure what you're responding to, but nothing in my response had anything to do with your age or skill level. Read again?

samakijoe

Loki: My age or skill level is "just there". It has very little to do with the work the engine does or your response to my
initial question. I was questioning your injection of the use of a stick transmission as the only
viable/correct equipped car to answer the inquire.
There is no difference to the engine if the mechanism between his crank and the rear end (MT or AT) or how it is
controlled by the use of a clutch or not (yes the ratios may be different, but who cares.).
Getting back to my original inquiry, How long and at what RPM should we run the engine (with either a MT or an AT)
to effectively try (and I do say "try" here ) to remove the carbon on the combustion chambers in the engine.
The question seems simple enough (or not) and I know there will be a wide variation in the answers/ideas......................
But that's OK

DocWalt

As Loki said, it has nothing to do with the RPM, it's about the load and getting it hot. Just floor it and let it rip through the gears. Better if you can do it up a hill and put more load on it.

As Loki said, the MT cars have extra intake valves that should be exercised by revving it high (under load) and the AT does not, so you don't need to go rev it to the moon, just floor it and put load on it.

kevink0000

Read Loki's post to yourself, out loud. He was trying to help you, as he often does to newcomers with limited knowledge. You seemed disconnected from his meaning with extra stuff that you added.

Your question, though, has not been brought up or answered well here in the past. 6000 rpm is a sweet spot rpm for any 2 rotor Mazda, for many reasons. You can run all day at that rpm, assuming your stock cooling system is adequate, and your ambient temps are low enough. Low throttle and high rpm is good for cleaning, as much as full throttle to redline, maybe more so. Same goes for piston engines, but even more these cars. BMW glovebox manuals used to tell the owner to do this periodically.

samakijoe

Kevin: I did read the post a couple times out loud the only thing new I was able to get out of this exercise was that
that wife asked me why I was talking to myself. And all your is doing was scaring the dogs. .
I said no, I was trying to make a guy on the RX8 site happy.........

Getting back to my initial query. Here are a few that come to mind as I type..
The original question:
"The question here is what is a consensus as to how long and often to run at 7+K?"
I was expecting a few answers like::
1. From Ottumwa Io. "I take mine to 8K for 5 min. then we (my 8 and me) go home as happy as two peas in a pea-pod. Goooolly Geee...........
2. From Newark NJ. "My brother in law never had a real job for 40 years and he said 'Hey, don't worry about'. But he's an Italian "Don" so I do what he tells me".
3. From Palm Beach. Fl. "Every few days I toss the keys to my 17 years old step son. The next morning I know I am carbon free just like those tree huggers keep praying for.

That's not what I was really asking for. You probably get the idea..No need to read out loud, unless no one is listening and you want to make someone happy.

NB. For extra credit, Who was the favorite son of Ottumwa Iowa.???


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Loki

iTrader: (1)

I'm not sure what to say here. I wrote a very different post from what you read, so I'll just repeat that rpm doesn't matter, it isn't the goal. The goal is full throttle application for as long as you can safely. Good day!

ZenVirZan

Depends on your engine.

Full throttle: good
Actuating all intake valving: good
High rpm: not so good (for the sake of maintenance)

If you have a 4 port engine, it does not have an APV or VDI (to my knowledge), so all actuations are done by 3500 RPM, so full throttle to 4 or 5000 RPM will do fine for both carbon and actuator reasons.
If you have a 6 port engine, the VDI actuates the highest at 7600 RPM, so rev it to 8000 occasionally for runner actuation. Otherwise full throttle to 6500rpm for carbon reasons.
Do not cruise near rev limit.

How often? For maintenance, as long as it's up to temp--once a drive is probably fine. I personally redline it whenever I feel like it and it's up to temp--no point owning it and paying for it if you're not going to enjoy it

10KRPM

Your post makes we wonder if I'm doing the right thing myself. So far so good, my 8 is running great/starting great.

Generally once a day I find a place where I can put my foot to the floor in 2nd, run it to 7500 plus rpm, into third, foot to the floor again, lay off and shift to higher gears after. So it amounts to maybe a 6-8 second full throttle pull. Reading your post, sounds like you feel that a better method is when driving steady to drop gears to get to 6000 rpm and run steady there at a modest throttle level.

Or maybe do some of both? Since the full throttle pulls are fun anyway, not exactly a chore to do them.

peloponisios

I wouldn't run a tired motor to redline.

AustinSaunders

Can I ask a question about it?


peloponisios

I am not affiliated with the business that posted the above on fb. I just agree with their statement. They articulate it better than I can and with documentation to support it.

10KRPM

I appreciate you sharing that info, always interested in different takes on this stuff. Curious what others think of their take on the WOT pulls. As I said I usually rev to 7500 plus, so I guess I occasionally hit or exceed 8000 but that's not the goal. I'm not sure I'm going to stop the practice based on this info but will back it down a bit to more like 6500-7000.

I got a chuckle out of the comment "is a absolute Chinese whisper internet forum mythology".

TeamRX8

iTrader: (25)

I posted up about the RX8 e-shaft having that issue not too long ago

which honestly using an OE shaft on even a prior 13B is one of the most overlooked issues in general on RX7Club etc. imo when upping the power output/boost.

but most rotary people are too cheap to drop $3k on a billet 4340 aftermarket shaft even though the OE one is flopping around all over the place. My opinion is that more turbo rotary engines blow up as a result of it than people realize. Not that revelant other than the posted link comments above.

but in general, over-revving a Renesis occurs @ ~8,500 rpm. Which even I spun them up to 10,000 racing. It’s going to kill the seals for sure resulting from excessive exhaust temp, and as all the best dyno graphs on here prove, peak hp is usually around 8,200 - 8,300 rpm and falls off fast after that.

When you’re racing/competing though, over-revving can make more sense than upshifting and having to downshift right after. It’s going to take it’s toll on engine life though. Been there, done it.
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kevink0000

I disagree with the FB post guy. You can't make a rule based on mileage in my view. He makes copper showing like its a definite bad thing. A bit larger clearance is not an issue, I put used bearings in a rebuild on purpose, not to save money.

My current engine has a 250k mile shaft and main bearings and front iron, and unknown mileage used rotors and bearings. UOA shows very little bearing metal, mostly noise. Almost no metal in pan at oil change time either. I rev to 8500, but not more. 20w-50 helps here in my opinion. Rebuild has almost 65k on it now, all used parts except seals. The shaft does flex in these engines, though, and the "balance" of the factory parts is a big factor. Agree though that high rpm is not good for longevity, like all engines.

But, I think many of these engines ruined bearings from belt overtightening. It may surprise some, but this engine design is especially susceptible to this problem. Have not seen any skilled rebuilders bring this up, maybe I missed it somewhere.

TeamRX8

iTrader: (25)

I agree with all that. I wasn’t clear enough on my e-shaft comments. For NA it’s not that big of a deal with a reasonable rpm limit and more so if the rotating assembly is properly balanced for competition use, but not so once power output is increased substantially i.e. forced induction. A lighter weight e-shaft is not all that beneficial imo, or rotors either. The rotor only orbits at 1/3 the eshaft rpm, and the e-shaft throws are very short compared to a crankshaft. So the inertial differences are much smaller compared to a piston engine. Several pounds aren’t worth the difference imo compared to the benefit. The concern with increased power is that there’s no center bearing between the two rotors to help stabilize the e-shaft from the fluctuating power pulses. An OE e-shaft under those conditions is bending and flexing around more than people realize. Even the billet e-shaft suppliers use a curved contact surface rather than squarely flat surface on the main bearing journals to account for it.
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BluSpectre

Going up a hill versus being on level ground doesn't change the maximum load of the engine. It will still be run at 100% load either way, it just takes more time to get all the way up to speed going up a hill versus the level ground. Although, by accelerating slower and shifting less, there will be 100% load for longer in theory.

BluSpectre

As the chromium wears off the bearings, yes you do start to see increased wear patterns but it isn't out of spec. If the engine is out of spec, it should be rebuilt or it is running on borrowed time no matter how you look at it, whether you redline it or not! It really doesn't matter. Besides, you won't even know anything like that is out of spec until something fails catastrophically anyways x3

Loki

iTrader: (1)

Or until you do a Used Oil Analysis ..