The recent discussion concerning resetting the ECU got me wondering.
A week or two ago, after reading the afore-mentioned posting, I added a can of Seamist, filled up with high-test, and did the reset. I then ran Emily down the highway at high RPMs (not getting out of 4th gear) for a couple of miles. Performing, in effect, an "Italian tune-up".
I've known about this for a long time (since the mid '70s, when I got my first street bike), and never gave it much thought.
So, my question is this; What, exactly, is the benefit or advantage to running the engine at high RPMs for an extended period of time?
I've got a couple of thoughts in the back of my mind, but wanted to hear from people with, maybe, more experience or wisdom than I.
Oh yeah, Emily is an '02 MCS, with less than 39,000 miles, bone stock, and well maintained.
Thanks,
Hegira

 

Running it at high RPMS is intended to burn off all the carbon deposit and build up. It's a popular thing that most RX8 owners do; they are recommended to redline their cars atleast once a day.

 

Where does this carbon deposit and build-up, build up?
Wouldn't the fact that modern ignition systems, with timing and ignition advance, as well as computer-controlled fuel injection, prevent (or at least diminish) this from happening?
I'm not trying to be a smart-***, I'm just trying to understand if there is, in fact, a benefit to wailing the snot out of my car.
Not that I have any objection to doing this.
I am, on occasion, dumb as a box of hammers....
Thanks for your patience,
Hegira

 

http://www.rx8club.com/showthread.php?p=2323505

good read. i think it should answer your questions.

 

RX8s are a different beast all together than our cars, but I'm not ready to get into pros and cons of Dr. Wankel's design today.

With fuel injected cars they're possibly more prone to carbon buildup than older pre-fuel injected cars. The fuel injected is very finely atomized and somewhat cool, when it contacts the hot intake valve carbon can buildup. The idea is that higher RPMS can create a situation where this carbon breaks down. I'd never heard you should run on the highway in fourth gear, but traditionally have been told a decent run at highway speeds once the car's warmed up would be sufficient. In the olden days people would take the cars out to "Blow the carbon out" but this was more to do with buildups of tarnish in the carburetor. For emissions and fuel economy reasons modern engines run much hotter so the situation I mentioned earlier is much more likely.

 

An "Italian" tune-up is not just running at high rpm's, it is running the car to redline (or close to it) thru the gears and then slowing down and doing it again. By doing this you are placing the engine under load which is what helps with the "blowing" out of the engine. What it does is gets the car up to a temp and rev range that effectively burns off the deposits from not running the car hard. The worst thing you can do to an engine is run it easily all the time.

 

I don't know if carbon buildup is more or less of a problem on newer cars, but with the older cars, the buildup on the piston face, valve faces and combustion chamber walls could get quite thick. The problem was that the carbon deposits provided "hot spots" that could continue to glow red-hot even after the combustion cycle was complete, and could prematurely ignite the air/fuel mixture in the next cycle.

Also, the buildup of carbon increased the static compression ratio by decreasing the volume of the combustion chamber, so you could get knocking/pre-ignition problems from that as well.

Fortunately, the carbon buildup is fairly soft, so it's easy to break it loose either with the "Italian tuneup" procedure described above, or by spraying atomized water into the intake while running the engine.

 

Why?

 

By being easy on an engine all of the time, the cylinder walls will develop a wear ridge lower than an engine that sees high RPMs often. When an engine is ran hard, the pistons and thus the rings, reach higher in the cylinder due to the pistons being thrown (for lack of a better word) harder towards the cylinder head. Also count expansion due to higher heat etc etc. The bad part about this is, once the car builds that wear ridge and is then ran to high RPMs, the top ring on each cylinder could hit the wear ridge and break the ring or the ring land (the piece of the piston that separates the ring grooves) and gouge/scratch the cylinder wall or break off and beat the hell out of the valves, the top of the piston etc etc.

Of course, this happens gradually but it does happen. I had it happen to me on an otherwise very nice Lincoln Mark VII that I used to have.

 

So you're saying that the higher the RPMs, the higher in the cylinder the pistons travel?
I would think the con-rod bearings would put a definite limit on that.

 

I'm not an expert on the subject but speaking from a materials/manufacturing point of view, it seems possible. In order for the con-rods to rotate around the crank, there is some play in the bearings. Now this play might be a tenth (0.0001") or so but it has to be there in order to rotate. Then add in the additional heat caused by running at high rpm's, and the thermal expansion of the connecting rod. We're not talking much but it seems reasonable.

Back to carbon buildup... The MCS is known to run pig rich at higher rpm's. It should produce less carbon when just cruising around, right. So is the high rpm thing just to get the high flow and high accelerations to 'fling' deposits off the valves and such?

 

Yes on both accounts.

You need to run the car "hard" fairly regularly as this will ensure that the engine can get to temp and be able to burn off the residues in the chamber and from the oil.

The engines I have seen in the worst condition have always come from elderly owners cars that only get driven around town and very rarely ever get anything close to wot acceleration.

 

Yes, that is what I'm saying. The connecting rod bearings aren't the only ones that come into play. The crankshaft main bearings and the wrist pin bearings also come into play. Have you have ever disassembled a high mileage engine? Most require that the upper cylinder be honed before the piston will come out due to the wear ridge.

 

 

While this may benefit the car, I believe the main benefit is to the driver... causing this -->

 

In just about every car manual it tells you that you should take your car higher than 4000rpm once a week to break up deposit.

 

learn something new each day....

 

i cant agree more with the general consensus of this thread. I work on cars and sometimes we get the occasional old lady in that really all she needs is someone to beat the crap out of it for a bit. Minis seem to develop carbon buildup on top of the valves far faster than most vehicles so id say avoid short trips as much as possible and dont be afraid to "give-er-hell" every now and again.

 

many people think the term "Italian Tuneup" is derogatory and denotes a "cheap" way of making the car run better without benefit of the traditional tuneup.

It actually comes from the fact that part of the tune-up/maintanance at an Italian Ferrari dealership included a high speed and high rpm run on the test track (or on the local highways) after the car went through the maintanance and before the final approval for realease to the owner. In many areas, this was an accepted practice for the local constabulary to see as "normal".

This was done because many Ferrari owners just drove them for the looks and prestige and not as they were designed--high performance vehicles.

Carbon would build up in the valves from the slow, low rpm driving and the cars were put through their paces as part of the mechanic's procedure. The idea was to get the car up to max operating temp and the parts to heat and work til the carbon burned out of the whole system. Without this, the cars tended to run rough and poorly. Other associated dealerships such as Fiat, Maerati, etc adopted the same process.

 

This is I believe my second post, though I have been "lurking" for a while. I own an '06 MCS that I bought on 31 December with 10,500 on her. This whole thought process on engine break-in and wear is very interesting. Some cars still have a drive it at this RPM for so many hours but vary the RPM's then at this none for so many hours but not over this. I own an airplane and have helped "break in" several engines.
Here's how it works with airplanes:
After installation run it briefly to leak check it, cowl it up and taxi directly to a usuable runway and take off. Climb to an altitude that would allow you to return to the airport without power and run wide open throttle for an hour! The only real prohibition is to keep the cylinder head temp's under 400 degrees (F). Within about 4 hours the rings will have seated, you do an oil change with analysis, cut open the filter and look for anything with a part number and rock on. I call it "flying it like you'd use a rented mule". Flown this way rings seat quickly and the engine will be good for many hours of service free flying. I don't know enough to understand the difference except to say that very smart guys about a/c engines have told me that a/c engines work harder than cars... Still I am curious about the difference in care.

I believe that car engines are designed to run a tad rich because it is less dangerous than running a tad lean. In my plane I run lean of peak on every flight but I have instrumentation that tell me the CHT and EGT of each cylinder. My plugs are always brownish gray, same with the exhaust. Just thought the comparison was interesting. Thanks to all of you who contribute to NAM, I have learned a lot and alr eady used much of the DIY info.

 

You guys have no idea how funny it is when I open my e-mail at work/school and everyone around me see's "Viagra...revisited".

 

For the most part I see nothing wrong with this break-in period although obviously aircraft are exposed to some different operating conditions than cars and it's really hard to find a place that lets you run a car at redline for a solid hour and still keep the engine cool. I do not think aircraft engines work harder than car engines though and this is part of the reson why it's safer to run an aircraft engine slightly lean while car engines need to be rich. There's no such thing as stop and go flying, while cars will see all sorts of different RPM and power demands in a typical drive, even on the highway. For the most part, once an aircraft's at altitude the engine runs at a set RPM, and just enough thrust is needed to keep going at a steady altitude and fairly steady airspeed, unless you're working with a stunt plane, I could see those seeing similar issues as with cars, on top of running upside down.

 

First let me say that this isn't by way of argument. Just interesting stuff. My A&P (airplane mechanic) and I had a similiar discussion regarding the differences when we were doing my annual inspection last December.

Regarding how hard the ac engine works, I go to full throttle on take off and reduce power when it is time to descend for landing (anywhere between 10 minutes and 6 hours). During that time the engine stays at max rpm. So think of matting the accelerator on your Mini and leaving it there until the gas runs out. The guy that made the 'working harder' statement has run engines on a test stand for thousands of hours, maybe he's wrong, doesn't really matter. And just for reference I run a lot lean. 50-60 degrees lean of peak. The engine likes it that way. Cylinder head temps stay low and valves and plugs stay clean! Someday maybe I'll understand all this stuff better!

 

But what RPM's are you running in the plane?

What size engine and what is it's layout?

 

It is an IO-550-N develops 310 hp @ 2700 rpm, which is the take rpm and never moves until I descend for landing. It is moving 3600 lbs with a 3 bladed prop. The engine looks like a larger version of a 60's VW, Porsche or Corvair engine, horizontally opposed 6 cylinder, fuel injected. I suspect there may be an argument that 2700 rpm is "loafing" and that may be valid, again I am claiming no expertise just anecdotal knowledge. Consider that on a typical flight the engine will start out at about sea level and will experience on average about 8-10K feet above sea level (thinner air) and as high as 17K feet above sea level. That said I don't know exactly how that factors in to engine wear and tear.

Regards,

Hondo