Author Topic: High RPM Driving (Read 17276 times)

zak · « **on:** September 09, 2015, 21:05:18 »

I had a great labor Day weekend driving my 67 250 SL ,4 spd all 3 days on hilly country roads around my north NJ home.
But even with aggressive driving and down shifting I seldom reach engine revs over 4000 rpm. I am usually around 3000-3500 rpms.
At 65 mph on the highway ( where I seldom take the car) I think the tach reads about 4000 rpms
I see the red line on the tach is at 6400 rpms but I have never even come close.
Do any of you guys do extended driving in the high rpm ranges, say 4500- 5000? I have always read that the 113's could sustain high speed/high rev driving for extended periods but am afraid to try it. Plus the noise...
thanks

jz

Paul & Dolly · « **Reply #1 on:** September 09, 2015, 21:21:02 »

Hi Zac,

These cars are very low geared, and mechanically noisy at high speed compared to modern cars.
This chart may help, but it assumes standard size tyres.

Paul

Raymond · « **Reply #2 on:** September 09, 2015, 23:20:50 »

In 2009, before I added the 5th gear, I drove to the PUB. In 4th gear, the engine could run all day between 4 and 4500 RPM. I'm enroute to PUB again and spent most of 9 hours today in 5th at about 3200 RPM.

Cees Klumper · « **Reply #3 on:** September 10, 2015, 06:31:03 »

We have a story in the earliest days of the forum where Albert de la Torre drove his Pagoda for a couple of hours at 190-200 KM/H continuously (so that would be around 120 MPH, must have been in Germany). I have pulled up to close to the redline many times myself for short sprints and once drove a long distance on the German autobahns to Frankfurt at around 90 MPH with my old 4.08 differential.
The engine is designed for higher rpm's but the drivers these days are not so ;-)

simonarn · « **Reply #4 on:** September 10, 2015, 09:12:41 »

feeling smug here with my 5 speed, I regularly get it up in the 180/190 kph range, and love the noise, roof up or down

simonarn · « **Reply #5 on:** September 10, 2015, 09:22:55 »

forgive me the splits but im not ripping the dash apart just for that

thelews · « **Reply #6 on:** September 10, 2015, 11:58:22 »

Previous owner of my 150K mile 250 SL, 4 speed drove the car from San Jose, CA to Nevada, 375 miles, in 4 hours. You do the math. I regularly take mine up to 5500 rpm in 2nd and 3rd gear when entering the freeway. These cars like to rev and run better for it. It's how they were designed. They are not current era cars that run at 2K rpm at 80 mph and aren't meant to be converted to that kind of ratio or driven at poopy rpms...that is, unless you want a carboned up, dirty oil, gummy engine.

BTW, I also have a 1970 Porsche 911 that balks at anything under 3K rpm and sings happier tunes the higher you go, all the way to 7K+

gimp · « **Reply #7 on:** September 10, 2015, 13:22:14 »

I took this photo on the way to Williamsburg.

Bonnyboy · « **Reply #8 on:** September 10, 2015, 13:47:36 »

After my Dad bought "my" car he would drive on the fairly deserted highways in Northern BC. He said that the car really liked to run around 170kph for extended periods and would do more in a pinch. Unfortunately for him his driving record got to the point where he was about to loose his license due to his "need for speed" so he put the pagoda away and purchased a Nissan Micra with 3 cylinders that could barely do 120 kph.

The day he bought the Micra he dropped the Merc off at the body shop for a small footwell repair and that was when they discovered it was rusted out in the rockers, floors etc. It sat for 25 years and didn't get on the road again until I rescued it a few years back.

I don't have the roads for high sustained speeds and haven't taken her over 150 kph but do take her up to 140 quite regularly for short intervals.

3.69 rear end

Bicbiker · « **Reply #9 on:** September 13, 2015, 21:03:14 »

Zak -
Keep in mind that all 230/250/280 engines achieve max torque at 4,500 rpm and max power at 5,500 rpm. The car becomes decidedly "alive" (sort of) while spooling up through 3,200 --> 5,000 rpm, so don't deprive yourself of the full experience.
Sustained high rpm driving: I recently drove I-80 & I-84 for 2 1/2 days (solo) at constant 3,500 - 4,500 rpm, arriving home after 2,200 miles. Down side? - my hearing arrived about a week later.
Assuming sound mechanicals and appropriate fluids, you can keep your foot in it.

zak · « **Reply #10 on:** September 14, 2015, 21:53:20 »

Thanks gentlemen for the interesting comments. Next weekend I will try booting up in the 5000 rpm range on some hi way driving. I have to admit I have been afraid to try it and have babied the car for the last 25 years!
I virtually never stay in 2nd gear for long. Let alone drive in 2nd at 4500 rpms. I get to 3rd quickly and cruise in that 3500 rpm range
Paul the chart is interesting. I will have to test to see if mine matches those numbers. With my 4.08 rear I think I am doing more then 3600 rpms at 70 mph. More like 4000 in 4th, but I will confirm. The chart should be accurate I 'm sure.
You guys sure have done some long distance hi way driving! Impressive.
I also have a 107, a 1983 280 SL automatic that I usually take on longer trips. It's handling is sedan-like at low speeds but it eats up hi way miles very quietly even though it's M110 engine is a high revver too.
But nothing puts a smile on my face like driving my 113!
JZ

jameshoward · « **Reply #11 on:** September 15, 2015, 11:52:08 »

Zak,

I'd agree on the chart. It doesn't look correct. Having changed from a 4,08 to a 3,46 the car is at higher RPM at 70 MPH than shown on the chat with the 4,08 line I'm almost certain.

JH

Raymond · « **Reply #12 on:** September 15, 2015, 15:56:32 »

Before I replaced the 4-speed with a 5'er, I did GPS tests. At 4000 RPM, I was making 72 MPH. With the .76 5th gear, at 3,000, I am making 76 mph. I just drove from PUB to Jacksonville The engine climbed the mountains and cruised the Interstates as happy as a meadow lark. It was meant to be driven. If your engine is healthy, with clean oil, keep an eye on the temperature gage and GO!

rjfurlan · « **Reply #13 on:** September 16, 2015, 00:22:50 »

To calculate or make a graph use

RPM = ( MPH x Gear ratio x 336.1 ) / tire diameter

I used
Gear ratio 4.08
Tire diameter 25.9
to get

55 -> 2911
65 -> 3442
70 -> 3707
76 -> 4024

My rpms seem higher and I think 25.9 might be to large.

Benz Dr. · « **Reply #14 on:** September 16, 2015, 03:20:06 »

My car has a ZF 5 speed with a 3.92 axle. I calculate my final drive ratio to be around 3.34. On my drive home through Detroit, I hit 4,000 RPM couple of times on 696. Using the RPM formula, I might have been going close to 90 MPH although it didn't seem that fast. All I know is that it's probably the craziest highway I've ever driven on. Very twisting, 4 lanes, rather blind curves if you'e in the outside lane, sudden stops without warning,

and very fast, very aggressive drivers. I saw a guy cut in less than two feet in front of another driver at 80+ MPH because he was driving in the fast outside lane. There were at least 40 car lengths in front of him for him to pull into but he did it anyway even though the guy in front of me was never in front of him or in his way. He was behind me for a mile or so ( I was blocked in ) and thankfully spared me the same treatment. He was driving a late model BMW.

mdsalemi · « **Reply #15 on:** September 20, 2015, 13:48:31 »

Quote from: Benz Dr. on September 16, 2015, 03:20:06

...on 696....All I know is that it's probably the craziest highway I've ever driven on. Very twisting, 4 lanes, rather blind curves if you'e in the outside lane, sudden stops without warning, and very fast, very aggressive drivers.

Dan, there's a reason why many years ago, I-696 was dubbed "the Autobahn" by one of the car magazines. It is a fast highway, and if you can't do 70 MPH when conditions permit you should stay off of it--note to those with flashers on, towing motor homes, boats, handicap plates in the right lane doing 45, etc. It isn't uncommon to see much faster traffic either. Last week while doing my standard 78MPH, a trio of motorcycles passed me at well over 100MPH. May God be with them.

If you look at the actual mapping, it is pretty darn straight. There are a couple of twisty bits but they are hardly twisty by modern highway standards. It runs pretty much E-W. You took the wrong way in some misguided thought to avoid going all the way on I75 for some fear of Detroit city. I drive these roads all the time, and can't understand why you went on 696. You went out of your way; you added about 20 miles to your trip.

As far as aggressive and fast drivers--you are correct. See paragraph 1. But as for safety, it actually is not bad--way better than many other highways. In fact, the deadliest highway in Michigan is I94, and that ranks like #70 in the nation.

You have the benefit of living in a relatively quiet rural area--thus these normal highway situations appear very strange to you. Want an unsafe highway? Drive the 401 to Toronto, mostly with no barriers to prevent traffic from wandering from one direction to another! Now that's scary.

Paul & Dolly · « **Reply #16 on:** September 20, 2015, 22:49:04 »

Hi all,

With regard to suggestions that the graph from my earlier post may be incorrect,

we took these rather blurry pics today,

3000rpm gave 56mph, and 3500rpm gave 67mph,

My speedo has shown to be accurate wrt sat nav,
so these figures would seem to be in accordance with the graph.

My car is fitted with Standard Michelin MXV-P 185HR14 tyres and the diff is unchanged from original.

Keep well

Paul

Benz Dr. · « **Reply #17 on:** September 21, 2015, 18:46:32 »

Quote from: mdsalemi on September 20, 2015, 13:48:31

Dan, there's a reason why many years ago, I-696 was dubbed "the Autobahn" by one of the car magazines. It is a fast highway, and if you can't do 70 MPH when conditions permit you should stay off of it--note to those with flashers on, towing motor homes, boats, handicap plates in the right lane doing 45, etc. It isn't uncommon to see much faster traffic either. Last week while doing my standard 78MPH, a trio of motorcycles passed me at well over 100MPH. May God be with them.

If you look at the actual mapping, it is pretty darn straight. There are a couple of twisty bits but they are hardly twisty by modern highway standards. It runs pretty much E-W. You took the wrong way in some misguided thought to avoid going all the way on I75 for some fear of Detroit city. I drive these roads all the time, and can't understand why you went on 696. You went out of your way; you added about 20 miles to your trip.

As far as aggressive and fast drivers--you are correct. See paragraph 1. But as for safety, it actually is not bad--way better than many other highways. In fact, the deadliest highway in Michigan is I94, and that ranks like #70 in the nation.

You have the benefit of living in a relatively quiet rural area--thus these normal highway situations appear very strange to you. Want an unsafe highway? Drive the 401 to Toronto, mostly with no barriers to prevent traffic from wandering from one direction to another! Now that's scary.

I had three other cars following me that had no idea where they were going so getting separated in Detroit wasn't an option. 401 has a divider from London to well past the east side of Toronto so it's much safer now. West of London to Windsor is still open to crossing the median but it's not as busy so it's not too bad.

I'm not afraid of 696 other than it is a very fast piece of highway, in a tunnel, with up and down rises, and it does have enough curves that allow you zero line of sight down the road to keep you on your toes. To be honest, I rarely see anyone cut someone off at less than 1 meter going 140 - 150 KPH! Call it what you like but that guy was an A hole.

Tomnistuff · « **Reply #18 on:** September 21, 2015, 19:10:03 »

When I'm finished with my restoration, I'll not be reluctant to rev the engine high, once the rebuilt engine is broken in just a little. Babying an engine for 25 years, however, then reving it much higher than normal can break the upper rings, followed by the cylinders and/or pistons.

Remember that tendancy for the cylinders to wear where the rings run. At low speeds, they don't stretch the rods much, nor do they thin out the bearing oil film much, so the clearance between the top ring and the top of the bore is greater than at high rpms. I once broke a ring on a Chevy truck as a teenager. The truck had been babied by my father for years, then at 16, I overrevved it. When we took it apart, a top ring was broken because I drove the piston up against the ridge at the top of the bore. That's why they make ridge reamers for rebuilding old engines. I was lucky. I broke only one ring, although the other ridges had marks on their lower edges.

Tom Kizer

RobSirg · « **Reply #19 on:** September 22, 2015, 06:19:22 »

I had my cylinder head rebuilt about 3000miles ago including new rings - but not new pistons. It sure drove better ever since then with greater power.

Although it is an Automatic, I cant help treating my car to an "Italian tune up" after it has properly warmed up. (IE: Flat stick). It typically revs to about 6000rpm before changing gears. I often see a puff of smoke through the rear view mirror the first time I plant my foot, but after the second time it blows clean and there is no sooty residue in the exhaust tips either.

She certainly feels better after that - more responsive, etc.

My Alfa definitely loves that treatment and the Benz seems to like it too - hope I am not hurting her? As long as I am not being too aggressive I like to think it is actually better for the car to burn off a bit once warmed up with fresh fuel, etc.

Rob

mdsalemi · « **Reply #20 on:** September 22, 2015, 16:45:50 »

Quote from: Benz Dr. on September 21, 2015, 18:46:32

I had three other cars following me that had no idea where they were going...

...are you kidding me? Do you guys have NO CLUE as to geography or roads? Does nobody carry a GPS or a phone with GPS? Were you the same guys that got lost for 4 hours on the way to Williamsburg? Come on...

Listen--once you cross the border, "I-94S to I-75S" is the ONLY direction you need to Findlay, OH. That's about 165 miles and more than half of the distance to Columbus! Then just add "OH-15S to US-23S" and that gets you to Columbus. Four roads. Someone is really going to get lost here?

I-696 is indeed one of the fastest roads in the USA that you'll ever be on; however there was no reason whatsoever to be on I-696 and I wouldn't go on it on a Friday afternoon westbound...because of the heavy traffic, the a-holes you point out, among other things.

All you have to do is ask the locals for good directions next time...we're happy to help!

Benz Dr. · « **Reply #21 on:** September 22, 2015, 18:23:42 »

Let me restate that: once lost if making a wrong turn.

I have no use for GPS. It's fine in the city if trying to find a certain address. I see people using it to go to the corner store - it's stupid.

There is no way I'm driving through down town Detroit with a 50 year old car. What many readers here don't know is how I94 is constructed. It runs about 15 - 20 feet below the surounding landscape which effectivly places you in a causway of sorts. There are all sorts of places you wouldn't want to break down or have to pull off the road looking for help.

You live in the general area and know the roads, where it's safe, and where it isn't. 20 miles out of the way? Uh, big deal when your driving 80 MPH.

Say what you want about the 401 but at least you won't get axe murdered on the side of the road if you run out of gas. All of Canada doesn't have the same rate as Detroit in one year.

cydways · « **Reply #22 on:** May 09, 2017, 05:52:27 »

mine enjoys 4-4500 for hours. This was coming back from SF to the central coast. 3 hours of it. '66 230sl euro 4spd

Cees Klumper · « **Reply #23 on:** May 09, 2017, 14:52:03 »

Good for you. All vital signs seem good: oil pressure, fuel level and coolant temp. This is the level we typically drive at in Europe, around 120-140 km/hour. You can see how far the rpms are from the redline. Although all the cautions do apply, about the general condition of the engine. But I would not hesitate to drive it for hours at 160 km/hr and waaaay back in 2001 or so, we had tales from one of our Spanish friends (I think it was Albert Chavalera) having ran at around 190 km/h for a number of hours once.

mdsalemi · « **Reply #24 on:** May 09, 2017, 17:01:57 »

Every ride of mine to PUB, six or seven round trips, was about 3-4 hours each way at about 3800-4200 RPM depending on conditions. Noisy as all get out, mostly top down (with ear plugs)...but no complaints from the engine department. Oh, it wanted premium fuel frequently, but that's to be expected.

News:

Author Topic: High RPM Driving (Read 17276 times)

simonarn

simonarn

gimp

rjfurlan