Blowin' out the carbon

I have an '85 Carrera, and a guy who rebuilt a 356 a number of years ago offered some advice: at least once a week, get the engine up to 5000 rpm to blow the carbon out. I don't do much highway driving, and the carbon buildup problem really hasn't affected the car's performance (yet). I generally shift around 3500 rpm & occasionally generate 4200 rpm.
Has carbon buildup been a problem for any of you on this board (those who don't take their car to the track)? I'm starting to wonder if those complaining about idle problems don't actually have carbon buildup. Some engines, I understand, are more susceptible than others.
Regards,
jlex.

geez; i must be some kind of hotfoot or something. even if i'm not accelerating hard in my '85, i'll still shift at about 4000 rpm, cause it just 'feels' like a good shift point. for me, i would have to really concentrate in order to hold my shifts to 3000-3500 rpm!!! am i in the minority??? 5000 rpm even seems like a tease to me if you're accelerating hard in these cars! someone educate me on this!

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Adam Nitti
www.adamnitti.com
'85 Carrera
'74 3.0 CS

I'm with you, Adam.
Its a rare trip indeed that I DON'T come close to redline in my 911.
Now, I'm not talking about cruising at redline, but how can you drive a 911 and resist a few bursts through the gears?
I know I can't!

I'm with you guys, can't pass up a peice of open road without putting my foot into it.

With the turbo I have to cruise around town at 3000rpm below that it will hardly get out of its own way.

A wrench told me Porsche reccomends taking the turbo up to 5000rpm in first gear once a week, they say it blows the moisture out of the wastegate---you don't have to tell me twice, it's also a great excuss to the wife when she tells me to slow down...

I usually shift at about 5500, except on freeway onramps where it is usually more like 6500 I seldom let my revs get below 3000.

I take it near redline every time I drive it. I doubt there's much carbon in there

A Porsche mechanic I know tells me that a routine part of his tune up procedure is to take the customer's car for a ride to blow out any carbon. Occasionally, it's all the car needs if the customer is a low revver. The customer is happy the car runs properly again and the mechanic tells them to stick their foot in it regularly -- they were built to be driven aggressively, folks.

The 'early_s' cars are different in that they have a higher redline, etc. I cruise my SC around 2500 to 3000 rpm. I'll go as low as 1500 in VERY brief circumstances and it operates smoothly there.

I'm certain that I never drive this car without at least touching 5000 rpm. Never. When I pull onto the freeway, I am commonly cruising along with traffic before I shift from third to fourth.

So I guess the point is (FWIW) that I use the whole range, and I feel very strongly that having a little acceleration fun at times (daily actually) does not hurt this engine even the slightest little bit.

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'83 SC

But officer, I was just blowin' out the carbon!

Now I have an excuse to tell my mom!

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Jeff
1976 911S

I don't think the carbon is as much a problem as it used to before they started putting detergent in the gas. Especially on an 85 Carrera which, correct me if I'm wrong (and I'm sure you guys will),doesn't run as rich as the earlier 911s. Still It can't hurt to open'r up and I must say, I'm with these guys, my E-cams don't even come alive until I hit 4500RPM's. And the sound...Well you know. Bobby 72'911TE

just a bit of speculation on my part, but would a move to a hotter plug theoretically avoid more 'carbon buildup' on a car that is being driven as conservatively as jlex's car? or is the o2 sensor/dme combo gonna render this speculation obsolete by running things so lean at all times anyways?

just wondering...

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Adam Nitti
www.adamnitti.com
'85 Carrera
'74 3.0 CS

My guess is that the fuel mixture is fine and that carbon buildup is unlikely. I doubt that anything is being hurt. Hard acceleration at low rpms can result in pinging, but this too is likkely to have been engineered out of the system.

Respectfully, I think jlex may just be missing some opportunities for grins. Here's some food for thought: If internal engine parts touched each other during operation at all, they would die quickly. We're talking fifty, count 'em, fifty revolutions per second at 3,000 rpm. Further, engines are perhaps in the most danger when idling, since oil p[ressure is lowest then. Engines can be damaged by idle settings that are too low. At higher rpms, oil pressure is so high it ensures protection. the danger with high rpms is valves floating and rods coming apart, and those clever Germans have built these engines better than that.

My $0.02. There's really nothing at all wrong with your driving methods, jlex.



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'83 SC

jlex - -
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I drove my 83 SC in a similar fashion for about 6 years - it was a garage queen. However, after a year's worth of Drivers Ed, I now experience far more pleasure driving. I typically shift at 4k but on occasion, will go to 5k+ on the street. Of course, on the track, I am running up to and at redline for much of the circuit, e.g., approx 125 mph in 4th gear = 6300 rpm at the end of the straight.
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In the stock SC, there is a strong "on cam" rush that starts at about 3,900 rpm and runs up to to about 5500 to 6000. These engines are designed and "like" to be driven at these higher revs.
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The next time you are merging on to the Interstate, hold the car in 2nd and 3rd gears until you reach cruising speed. Your car should do 75/80 mph comfortably in 3rd gear. Try it, you might like it - and for sure, your car will!
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Chuck

[This message has been edited by patalive (edited 08-26-2000).]

If you have carbon buildup I think you would know. The engine would start pinging a little when on the hot side, and getting on the throttle. And in really bad cases would diesel when you shut it off. To get rid of carbon in really bad cases I would start the engine and shoot carburator cleaner into the intake until dies. Then let the engine sit for a couple of minuits to soak the piston crowns and heads. Then start the engine and watch the smoke show until it smooths out. Another old side of the highway trick is to slowly poor water down the intake while using the throttle to keep the engine from dying (about a pitcher or two usually does it). This softens the carbon and allows it to burn away. Best way to keep carbon at bay and have fun doing it is to get them R's up, porsches love it.

[This message has been edited by leon (edited 08-26-2000).]

Oh my god it's amazing how much power there is in the 4k to 6k powerband! I did exactly what you said to do last night Chuck and it was unbelievable! Too bad the speed limit here is only 50mph but damn that rush from 60 to 80 in about 2 seconds is unbelievable! I am a happy camper! Enjoy your Porsches!

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Jeff
1976 911S

Oh the fun our freind jlex is missing out on by changing up so early!!
That rush of accelaration, power and noise as the engine comes on cam at just under 4K. Like most of you guys I rev my 86 Carrera through the gears just for fun. The noise alone still sends a tingle down my spine and brings a silly smile to my face - every time .
To me this (and the wonderfull handling)is what 911 ownership is all about.
Enjoy!

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Alan Brown
86 Carrera 3.2

ahh, the sound of the S motor with the MSD set at 7,300 rpm limit.

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77911s

Yes, that S-motor sounds like it would be a hoot with the 7300 redline! And Chuck is exactly right...my car could be a three speed. My exhaust (stock, new cat) and new sound pad force me to watch my tach. I kinda wish for a louder exhaust. but I do what Chuck says. Getting on the freeway is one of the few chances to (sort of) ask the car to exercize.

In fact, since first gear is over so quickly (blink of an eye) when the throttle is open, second is really my only fun street gear without risking a ticket. At the top of second, I'm travelling at a highway speed limit. Third goes nearly to 100 mph! What a car!

The car has NO PROBLEM handling its freeway merging duties in third.

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'83 SC

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I am grinning from the responses. It's a difficult question to answer - - why is driving a Porsche so much fun? We all have our reasons but for sure, there is the "grin factor"
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I work at home most days, but at least once a week, I have to go to the "client's" office down in Washington. While I don't look forward to the meetings, etc. I am anxious to make the drive in the SC. I purposely leave the house at 6:30 to minimize traffic involvements - Shooting down the George Washington Parkway, with the sun just coming up, the roaring/burbling SSIs/Monty in my ears, - - pure bliss!
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On the return trip, at the top of the GW parkway dropping down on to our infamous Beltway, there is a sweeping, constant radius corner to the left, followed by a tighter radius corner to the right. Going into the "bend", it's such a kick to have another car that has been pacing me at 60-65 or so - I hold my speed constant effortlessly through the corner - - - - the other car tries . . . . and fails. The snicker factor sets in. Particularly so when the "other" guy is in Explorer, Lexis SUV, Caddy SUV, the Big Chev SUV, or some such similar truck. The grin gets wider!
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Chuck

[This message has been edited by patalive (edited 08-28-2000).]

Questioned my wrench on this issue the first time I had my car serviced. His advice was to change gears in excess of 4000RPM every opportunity and don’t be afraid crank it up to the redline. His justification for this was that for those cars with Webers, city driving means they spend most of the time only using the idle circuit, not good for keeping tune – besides the cars were engineered to go hard. Needless to say I had him repeat this in front of my wife.

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Paul
911T'69

I have evidence to back up the effectiveness of this new service technique.
A few weeks ago I pulled off my throttle bodies for some overhaulling: no carbon. This weekend I pulled off my heat exchangers to fix a few ailments (MFI drive belt and heater hoses etc.) and found no carbon build up on the exhaust valves or ports. All despite the liquid coal we must run here as fuel. This leads me to the inescapable conclusion that nailing your throttle pedal as often as possible yields great rewards.

Lately I have been sharing my love of high pitched noise with those fortunate enough to be overtaken by my 'lil silver bullet; through choosing a gear lower than absolutely necessary during the manoueveure. This makes me grin, and I hope I am helping them enjoy the day by showing them what a real road car should sound like.

Bottom line is I'm just doing what the mechanic told me to. Why argue with logic?

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'72 911 TE

Chuck has it right

So many times I'll have someone trailing me on the street in my blind spot or on my tail as soon as I hit the a onramp thats got a nice turn I rap it out and they are left sucking Porsche fumes in my rear view, I have had a few go off the road almost trying to stay with me.
POrsche seemed to set up these cars for 30-90mph power band thats where they really kick in as opposed to a Corvette thats set up for stoplight races