Hitting 5.5k often.....

[porschegeorg]

There was a 9k RPM limit on my RX8. I don't know about piston engines, but rotary engines really do need to be taken to the limit every once in a while. Not the most torque, but the smoothest power I've ever driven.

I still like my Box better.

[larryshomework]

I hope there's no problem with it - I've been pushing it towards red-line on every drive.

I frequently drive (in twisties) with the car around the 4K mark so I've got power when I need it.

If this is bad, I don't want to be good

I ALWAYS redline 1st 2nd and 3rd aBout every Day

[Adam]

Originally Posted by Brucelee

However, don't convince yourselfs that it is "good" for the engine. Your engine is not a muscle, it doesn't get stronger from use.

It is a constantly dying piece of machinery that dies a slow death, one RPM at a time.
Enjoy!

I totally agree with you Richard, I don't think anybody in this thread said it is "good" for the engine to be reved high or driven hard. However, it's a sports car and unfortunately some people never enjoy the car the way it was intended. An extreme example; I talked to this one guy the other day that has a 2001 C5 low mileage vette and he told me he has never driven it over 35 mph and he is afraid of driving it on the highway for fear of rock chips. He won't take it to car shows either because he afraid it might get scratched It's a C5 for crying aloud...they made 250,000 of them! Who are you babying it for? The guy was 65 years old and I'm thinking this guy seriously needs to get a life....he probably doesn't have a lot of good driving years left. Why waste them?

[dmcutter]

"I ALWAYS redline 1st 2nd and 3rd aBout every Day"

Good lord. I passed someone the other morning on a back road and saw about 85 by the time I got past them. I know I was in 3rd but honestly didn't look at the tach. I do know I didn't bounce it off the rev limiter. What's top speed at redline in 3rd?
My ZX10R will do 100 in 1st at redline...I don't get to bounce it off the limiter too frequently

[Brucelee]

Originally Posted by Adam

I totally agree with you Richard, I don't think anybody in this thread said it is "good" for the engine to be reved high or driven hard. However, it's a sports car and unfortunately some people never enjoy the car the way it was intended. An extreme example; I talked to this one guy the other day that has a 2001 C5 low mileage vette and he told me he has never driven it over 35 mph and he is afraid of driving it on the highway for fear of rock chips. He won't take it to car shows either because he afraid it might get scratched It's a C5 for crying aloud...they made 250,000 of them! Who are you babying it for? The guy was 65 years old and I'm thinking this guy seriously needs to get a life....he probably doesn't have a lot of good driving years left. Why waste them?

Absolutely! I am NOT suggesting that we drive our sports cars like little old ladies. I am simply saying that in the spirit of honesty, we don't go down that road of "hey, I have to drive it hard because it is good for the car!"

As a machine, it is clear to me that when I hammer my Boxster, I am NOT doing it any good.

Good stuff!

[RandallNeighbour]

Originally Posted by Adam

These engines weren't designed with Sunday drives to church in mind just in case anybody was wondering.

Uh oh. I drive the piss out of my car every Sunday morning on the way to church. I near-redline it every time I drive it, Sundays included!

Basically, I feel the need to have something to confess when I get to church, but I'm not really repentant so I don't think it really counts.

Richard, I did read just today in Panorama's tech section where someone said it is good to near-redline a Porsche engine once in a while to blow out all the carbon buildup that might have accumulated from putzing around in the city and not running the engine hard.

So my question is, where is the carbon building up anyway? The heads?

[MNBoxster]

Originally Posted by RandallNeighbour

Uh oh. I drive the piss out of my car every Sunday morning on the way to church. I near-redline it every time I drive it, Sundays included!

Basically, I feel the need to have something to confess when I get to church, but I'm not really repentant so I don't think it really counts.

Richard, I did read just today in Panorama's tech section where someone said it is good to near-redline a Porsche engine once in a while to blow out all the carbon buildup that might have accumulated from putzing around in the city and not running the engine hard.

So my question is, where is the carbon building up anyway? The heads?

Hi,

Randall, Carbon will build up on the Piston Domes, the Combustion Chamber (underside of Head and Uppermost part of Cylinder - above Piston Height at TDC) and on the Valve Seats and Valve Face. It can also migrate into the Valve Guides in extreme cases.

Although some Carbon is inevitable, most of it occurs from unburnt Fuel on deceleration. No Fuel Metering System (EFI or Carburettor) is instantaneous. If you're cruising at mid-to-upper RPMs, the Fuel Metering System is supplying more Fuel to the Cylinder. But, when you lift off the throttle such as when decelerating and shifting, more fuel is still being introduced for a short time before the system can adjust, usually only for a couple cycles, but still more than can combust completely, so some of the by-product of this incomplete combustion is molecular Carbon (as opposed to CO or CO²) which condenses on the surfaces mentioned above.

There are several problems with excessive Carbon build-up. It effectively reduces the volume of the Combustion Chamber which can lead to detonation from the resulting higher Compression Ratio. It acts as an insulator on the Valve Face and underside of the Head. This reduces the Heat Transfer from the Combustion Chamber and Valve, In the case of the Valve, it can get hot enough to warp and no longer seal properly or literally burn.

Remember, the only cooling the Valve gets is when it's in contact with the Head and can transfer it's Heat to the Head to be carried away by the Coolant (Valve in Closed position).

Also, Carbon buildup on the Valve Seat can interfere with the Valve Seal leading to lower compression as the Valve is now partially open on the Compression Stroke. This can have a cascading effect because it causes more incomplete combustion and greater condensation of Carbon (remember Carbon comprises 80% of Gasoline). Additionally, for the Exhaust Valve, if it remains partially open, it allows combusted gasses to escape rather than pushing down the Piston robbing Power.

It also insulates the Head preventing efficient Heat transfer from the Cylinder, leading to Head warpage.

Carbon on the Piston Domes can lead to improper Flamefronts, detonation, warping of the Piston, and premature wear of the Wrist Pin and Small End Bearings.

Some degree of Carbon is useful and is actually expected to provide some additional lubrication and sealing. A properly tuned engine will maintain this correct amount.

But, having said all this, there is some fallacy to the practice of running the engine at high revs to burn this Carbon. Carbon is an element and thus cannot be burned or further broken down.

Running for long durations at high RPMs can break the mechanical bond some of this Carbon has with the engine internals, and then literally blow it out of the engine and into the exhaust system as particulate matter.

But, the key here is sustained periods of high RPMs, not running up to Redline between shifts. You can actually create more condensed Carbon with this practice as you lift to swap gears and the engine decelerates resulting in a negative sum gain. And, if you think about it, you're actually running a compromised engine at high RPMs and actually contributing to any damaging side effects such as increased Carbonizing and detonation.

But, in modern ECU controlled EFI engines, with today's much more highly refined gasoline, Carbon buildup is much reduced compared to earlier designs and engines simply do not Carbon-Up as much from low or intermittent RPMs such as idling and Stop & Go driving. The main issue with these conditions is not condensation of Carbon, but the low operating efficiency of the Oil and Coolant Pumps, which are RPM dependent.

The best way to remove builtup Carbon in an engine is with the use of some solvent (engine additive) which will chemically loosen the Carbon so it can be removed from the system either as a particulate, or by being dissolved and combusted into a Carbon-bearing Gas (CO, CO²)...

Happy Motoring!... Jim'99

Originally Posted by dmcutter

"I ALWAYS redline 1st 2nd and 3rd aBout every Day"

Good lord. I passed someone the other morning on a back road and saw about 85 by the time I got past them. I know I was in 3rd but honestly didn't look at the tach. I do know I didn't bounce it off the rev limiter. What's top speed at redline in 3rd?
My ZX10R will do 100 in 1st at redline...I don't get to bounce it off the limiter too frequently

In 3rd i get up to about 90mph

[7th gear]

Originally Posted by MNBoxster

The best way to remove builtup Carbon in an engine is with the use of some solvent (engine additive) which will chemically loosen the Carbon so it can be removed from the system either as a particulate, or by being dissolved and combusted into a Carbon-bearing Gas (CO, CO²)...

i most appreciate your input. keep it coming.

somebody do an advanced search here on this post:
Keep her above 4000rpm and she'll thank you for it every day.
posted by deliriousga

the 1st post changed my driving as i 1st drove @ 3.5k on average. now i drive mine @ about 4 - 5k down the hwy.

further.... let me ask how much truth does the type of gas i put into my car help to break down or clean my engine parts have? i put 91 in my 986 and i read chevron has techroline . shell has vpower . union 76 ... etc. they show pictures of a dirty part w/o their gas. then they show a clean or cleaner part after 2 tanks of their gas. how much truth to all their advertising about cleaning my engine parts will clean out the carbon build up?? i believe that most of that is ad hype but how much is kinda my question.

[edevlin]

Quote:


""I ALWAYS redline 1st 2nd and 3rd aBout every Day"

Good lord. I passed someone the other morning on a back road and saw about 85 by the time I got past them. I know I was in 3rd but honestly didn't look at the tach. I do know I didn't bounce it off the rev limiter. What's top speed at redline in 3rd? "

I dont get up there that often and when I do I am usually busy watching the road when I am redlining in the higher gears. I normally like to shift at 6.5K, before redline for a couple of reasons. First, dyno says that 6.5K is peak hp for my engine, but more importantly because I understand that these are mechanical devices that wear out, and I want this car to last.

That being said, I redline (7k) at about 94 mph in thrid, about 126 mph in fourth, no idea about fifth. BTW, I could take it higher than redline because my chip has raised the redline up to 7.3K and softened the rev-limiter. But as I said, I rarely even go to the 7K redline (but spend a fair amount of time at 6.5K). I think in the 17K that I have driven my car, I have only hit the rev limiter once when I downshifted early going into a curve.

Ed

:dance: :dance: :dance:

[Brucelee]

If 6K is good, 8K must be better.

Let us know how that turns out!

[markk]

Maintain it correctly with proper oil, clean filters, and perfect plugs, belts, etc. Put good quality petrol in it. Warm it up nicely (at least 10-15 minutes) untill you floor it. Let it cool down a bit too by driving the last 5 minutes or so before shutting it down nicely as wel (especially for turbo charged cars this is _VERY_ important)

For the rest, rev the hell out of it. It's made for it...

I do it with my BoxsterS, with my Mitsubishi EVO 8 MR RS and my wife's Peugeot 206gti all the time. Same for my former cars (Subaru Impreza and BMW e30 M3). No pain at all. Engines keep running as strong as ever.

And I will certainly do it with the "new to me" MY01 BMW e46 M3 I just ordered and gets delivered in 2 weeks. Woehahaha, a 8200rpm redline :-)


Mark.

[thomschoon]

Originally Posted by Brucelee

However, don't convince yourselfs that it is "good" for the engine. Your engine is not a muscle, it doesn't get stronger from use.

It is a constantly dying piece of machinery that dies a slow death, one RPM at a time.

You are very correct, an engine has only so much life, use it up only as fast as you can afford.

[Brucelee]

"'81 911 SC ROW = The Money Pit"

I rest my case!

[Paul]

Good, I'm glad we will never hear that opinion again!!!

[Brucelee]

Interesting. See the bolded comments on higher RPM impacts on engine internals.







Date: Wed Jun 7 11:55:45 2000
Posted By: David Ellis, Researcher, NASA Lewis Research Center
Area of science: Engineering
ID: 959212290.Eg
--------------------------------------------------------------------------------
Message:


I am assuming you are referring to overall fuel efficiency of the car in your question.

Fuel efficiency is generally referred to as miles per gallon of gasoline burned or MPG. The higher the number, the higher the efficiency of the engine. For a given engine, two main things determine the fuel efficiency: the gear ratio for the transmission and the amount of fuel consumed by the engine.

The transmission ratio is critical to efficiency because the ratio determines how many times the wheels turn per engine cycle. In a low gear, i.e., first gear, the wheels turn less than once per time the drive shaft turns. This produces the high torque needed to get a car moving, but it would be very inefficient at high speeds.

Higher gears have the drive shaft turn fewer times until in either third or fourth gear the drive shaft turns about once per revolution of the wheel. In modern cars equipped with overdrive, the highest gear, normally fourth or fifth gear, will have the wheels turn more than once per revolution of the drive shaft. Very little torque is produced relative to first gear, but the ratio means you get the most forward progress out of each cycle of the engine. This produces the highest efficiency for a given engine speed or revolutions per minute (RPM). Since you have to be going around 35 mph (55 kph) to get a car into overdrive, the first part of the answer is yes, the efficiency of a car engine increases with increasing speed.

However, what happens once you start to increase your speed further? Increasing speed means increasing the RPM of the car engine. As the engine speeds up, the mechanical efficiency of the engine parts tends to decrease due to increased heat, friction, vibration, noise, etc.

The exact speed where the maximum occurs is specific to each engine and can change with time as parts wear. Some increases in efficiency may occur as the speed increases because increased temperature removes the built-in allowances for thermal expansion and allow such items as the piston rings to seal for maximum efficiency. In general, though, the maximum efficiency is realized around the speed at which the car shifts into its highest gear.

[RandallNeighbour]

Jim, thanks for that good long explanation. I always learn a lot from you when you are in education mode

One follow up question. How often or when should I be adding an additive, or will running Chevron with Techron consistently keep the carbon deposits low?

[Adam]

Originally Posted by edevlin

Quote:

I think in the 17K that I have driven my car, I have only hit the rev limiter once when I downshifted early going into a curve.
:dance: :dance: :dance:

The rev limiter is only in affect when accelerating. If you down shifted into a lower gear going into a curve then that's called a mechanical over-rev if it went past redline. Usually the back tires lock up momentarily and you get jerked forward pretty hard soon followed by some expletives...ask me how I know It can potentially kill your engine.

[dmcutter]

My '04 Kawi ZX10 has a slipper clutch, I think maybe it was the first production bike to have one and now about all the liter bikes have them. Whycome spensy sports cars don't have 'em? Granted, one should be able to match engine speed to wheel speed on a downshift, but stuff does happen...