ok since not one of my four 7's are on the road and no time to fix them, i was forced to buy another one. Its a S4 n/a rebiuld with 15,000 or so miles on her, and it has a streetport. My question is about the redline. Im not too familiar with ports, so I havent taken her past the original redline. Is it safe to go over the 7000 redline, and if so what rpm can I take her to?

 

I think on any rotary you can push it past the redline, a lot.

 

Depending on how big the streetport actually is will determine at what rpm you'll make peak horsepower.

^Just cause an engine revs high doesn't mean it's making power.

 

im not sure where it will peak, just afraid to take it higher without some experienced answers, but i know at 7000 its still making power, its just a daily driver for now till I get one of my other ones finished, so I dont really want to go dyno it and spend money where its not needed to be spent. Just curious on if I can go to 8 or mabe 9 grand rpms.

 

You probably can't rev up to there simply for having the rev limiter.... You could do it but higher revs will shorten the engine life some.

 

stock bearings arent reallyt designed to be reving above 8000, the rev limit wont alow it anyway, one way would be to dyno it to close to 8000 and see when the power actually peeks.

 

since it's streetported your powerband is extended...it should reach up to 9500...

 

There's no reason to rev the engine so high.
The engine does not make that much more power beyond stock redline.
Unless you're going to get rid of the rev limiter in the stock ECU, you can't go up that high anyways.

Is this why you have all these dead cars???


-Ted

 

Word!

Any high revs will decrease the engines life. No matter which. IMHO RX-7's can handle it better.

Also 9500 RPM? Just because you can spin it that high doesn't mean you're making good power up there. Just making alot of noise

 

The type of intake and exhaust setup can make a huge difference on where the peak power is. My sidedraft intake makes more power at higher rpms than the factory intake but the engine porting is the same. Actually the current intake/exhaust combination makes more power across the entire rev range.

 

On my streetported '87, it makes good power until about 7500 RMP. Just drive it and see. If it feels like you arent pulling as hard at high rmps, then theres no reason to take it there.

 

I know there is no need to go that high, just asked to solve my curiosity, I usually just stay between 5 and 6 anyway. Thanks for all the input.
Good question Ted, but no thats not why I have all the dead cars. Two I actually bought as project cars, 79GS which does run, just needs some carb work and interior, 88 vert which did run till I started taking her apart for a 3rotor swap, which never got around to finishing yet, finance issuses. Then my baby, 90gxl lasted me a long time till she finally blew a seal at 179,560 miles on her, in the middle of a total restoration on her now, should be done by spring. And then there is an 88GXL which was my daily driver, has blown coolant seals, she runs but dont want to do any more damage to her, so she sits for now. So there is my fleet of project cars, two run, two dont, just none of them are road worthy at the moment. Now you all know how trully insane I am, I will not part with any of them, and when I have another garage built, I intend to get more, I want one of every year built. Would also like to have each of the earlier RX models, I tell myself good luck on that one.

Its tough to find time, I love these cars and one day will find the time to finish all

 

Lay off, Ted. Give me one reason why you had to throw in this condescending little jab.

Honestly, just one reason why you had to throw that in there.

He asked if it was safe to go above the redline on a ported engine because he knows that porting an engine shifts the torque curve and thereby raises the shift point.
He nowhere stated that he took his car above redline, and, if anything, implied that he did NOT take his car over the factory redline.

 

Sean he ONLY posts negative comments. Just laugh at him like the rest of us do.

79seven: Porting obviously changes the potential powerband but as MPM said, intake manifold and exhaust design can play a big role on it as well. The thing you need to know is that just because and engine can physically make power up real high does not necessarily mean it was physically built to rev that high. On the other hand sometimes it won't make as much power to justify going that high. I used to rev my old '88 n/a engine up to 8000 rpm all the time and that engine never failed. In fact I even rebuilt it after I installed a turbo engine in that car. Even the bearings were still good. Just to deal with any cheapshot over that statement, I've never blown up an engine. My '91 engine has seen 9000 rpms on several occasions. The thing is that I'm not always driving with the revs that high. If it were a race car that was always stuck up there under full load, I'm sure problems would arise much faster but on the street you usually only hit that high for a second and then shift unless you are trying to see how ultimately fast your car can go. Up at those rpms for sustained periods brings about other potential issues, most notably with cooling. Don't be scared about hitting the rev limiter. It'll be fine. That's why it is there. Of course you aren't as fast if you shift after it has hit the limiter so shift between 7000-7500 or so. It'll be fine. You'll probably end up killing clutches and transmissions first.

 

The reason why he post's negative posts is because usually he's right.

As in this post, you're asking if it's ok to go above stock red line, his smart elic remark was 'is that why you have so many dead cars?' which in ted to english translation is...NO it's no safe to take it above the stock red line because you're not going to make power up there unless you're severly modded.

- Tech

 

There we go! Just because Ted has answers doesn't mean he is a dick.

 

When you get an education in engineering, you'll realise that Ted doesn't have the answers after all.

 

Screw that, so what, you can read a book and stay in class and listen a teacher blaber on...doesn't proove anything.

Fact of the matter, I work with people who are A+ certified and have CS degrees and all that other BS and guess who they're always asking about computers...ME that stupid kid who dropped out of high school and doesn't even have a GED yet...go figure.

 

Wow, does that mean you have one???

So when I get my engineering degree, does that mean you *have* to listen to me?
For some odd reason, I don't think you would.

For some reason, there has been an exceptionally high number of these threads started about redline and going beyond that - full moon?

The reasons are basically the same as with a piston engine on why it is not recommended to rev the engine past it's posted redline.
It doesn't take an engineering degree to understand that.
It take a mechanically-inclined brain to comprehend that; the engineering degree doesn't hurt.

The rotary engine internals (i.e. rotors) are floating on oil journal bearings.
As long as oil (pressure) is adequate enough, the rotors are happy spinning in their positions.
What happens when you start to push the rev's up (past redline)?
This protective oil film in the oil journal becomes unstable.
What happens when the rotor (bearing) contacts the eccentric shaft lobe?
It "burns" the rotor (bearing).
Burning rotor bearings is BAD.
The rotor bearing is made up of proprietary stuff, but it's most likely a lead / indium (i.e. Clevite) coating with an underlying copper layer.
When you start to expose the underlying copper layer, this is BAD - visual inspects of rotor bearings that show significant copper exposed usually mean replace the bearing.

Now, if you're lucky, you just kill the bearing(s).
What happens when you go PAST that?
The rotors start to "slap" the rotor housings - i.e. rotor slap (from overreving).
This imparts nasty scrape marks on the small, vertical lobe on the rotor housing, and it hammers the apex seal points on the rotor tips.
This is an EXTREME case of what happens when the rotor contacts the rotor housing...


So what do you do to prevent all of that?
With the bearings, go with deeper grooved bearings and bump up the oil pressure.
Rotor contact can be minimized by clearancing the rotors for high RPM use.
Lightening the rotors will also help, as it cuts down on the inertial weight of the rotors spinning so fast.

Now, how do you fuel such a beast?
Carbs are still a popular option, but that takes money.
A "set" of calibrated carbs for such an application is not cheap, unless you happen to get lucky or come across an eBay special.
The other option is to go stand-alone EMS.
Now, if you have the capability of tuning a stand-alone EMS for this application, I would assume you would've known everything I mention in this article in the first place.

So, after that $10,000 motor has been build, what else do you need to take care of?
First of all, porting wouldn't hurt.
With the engine spinning so fast, you need to maximize air getting in and air getting out.
Enlarging the intake and exhaust ports will surely help.
Radical intake porting (i.e. bridge) will really shine at higher RPM's.
The (stock) exhaust ports already have very aggressive timing, but it doesn't hurt to go further.
But all if for naught if the exhaust is "restrictive"...
"Restrictive" is a relatively term, and it comes down to how-much-exhaust-noise-can-your-ears-handle-before-they-bleed!
The more open the better.
Choking the engine down with a restrictive exhaust, just made all that hard work above a waste.
Ever heard a fat BP or PP engine run down the track?
It's downright hideous.
Is it streetable?
Only if you don't get caught by the cops, or your neighbors don't shoot you first.

So what does this all come down to?
Those that do know how to do this, don't ask how-to in the first place.
Don't even think this kind of set-up is anything remotely street-legal - you'll break just about ever noise pollution law in the civilized world.
If you're going to choke down the noise with an assortment of mufflers, it's a waste of time building such a high revving motor in the first place.
If you're trying to do this with the stock engine with the stock ECU, you're more likely going to hurt the motor.

I'd like to know what college-level engineering course would teach all of that?
AFAUIK, I don't know of any U.S. college that teaches all of that in their engineering courses.
That's hands-on and research; time is something I guarantee I have an advantage in.


-Ted

 

Sure do. You don't. It's obvious.

No, it means when you actually take some courses in fluid dynamics, you'll realise that most of what you've stated in the past is completely wrong. I won't need to listen to you, you'll just be agreeing with me instead of arguing bullshit you know nothing about.

But, heck, if you actually did any experimentation for yourself, you could learn most of the applicable laws from fluids that applies to the rotary without doing any book studies. But no, instead, you spew out misinterpreted information from a Corky Bell book as though it is the bible on all that exists in the combustion engine world.

There's something to be said about the nescient....

 

That's why you're such a well-respected engine builder, right?

You think this is something that took huge time time and research ? Seems like something that was taught in high school mechanics if you ask me... I knew everything you stated from reading a haynes manual when I was 14.

This is all ironic, since you have stated that you have no experience when it comes to racing. This is case-proven when you state that showing the copper lining on a bearing is BAD... race clearancing always involves visual copper present on bearings.

Ever set up an external oil pump? What about a dry sump? Ever even attempted to modify the stock oiling system to reduce the ridiculous pressure drop across the oil cooler?
Didn't think so.

So, Ted, tell me again about that time advantage you have...

 

Ah, thus the condescending attitude...
of course, book smarts over street smarts...



Seriously, I dunno where this came from...
I don't remember any (recent) beefs with you, so I dunno how I'm supposed to defend myself.
I dunno what I did to **** you off so much, but I apologize in advance for whatever I've done to step on your toes.


-Ted

 

Nope, never claimed to be...
I'm SURE you will find people that will support that also.

Ah, more condescending remarks...

Or course, it bites me in the *** whenever there are absolutes.
Of couse I never pointed this out - if you are able to, reading my **** is a waste of time in the first place.

Nope, no external oil pump.
Nope, no dry sump either.
Modify stock oiling system?
"Port" the oil pump cavity? Did that already.
Bypassed the front cover? Did that already.
Why mess with the stock oil cooler when it's obviously not good enough for big power - I'm sure you know this already.


Right now?
I got none.
Not enough to tinker with stuff just to produce answer that will satisfy you - I put money on that.
It seems that this has turned into badgering, so don't waste your breath.
I believe in the ignore system available here - I don't believe you will present anything useful to me, so have fun with your degree...


-Ted

 

<edited for personal attack>

 

common guys- take it outside

And scathcart- you know better than flaming like that last post I just edited. Leave the personal **** out of it.