Tuning

[JamesL]

The Petrolicious article posted in the Genny about the 230 got me thinking...

Many owners of many types of car will tune them, tweak them and tinker with them to get more power: carbs get bigger jets, pistons get a bit bigger (easy on a 911 engine!), cam profiles shift and so on all the way up to forced induction etc.

There seems to be little discussion of such activities on here, so, hypothetically, what could be done should someone want more juice for their squeeze? I am perfectly happy with my drive but...

[Benz Dr.]

I've done just about everything I can on my engine using vintage parts as well as some suspension tricks. This is on a 230SL with 250SE engine installed

early 230 SL header pipes
visco fan clutch
250 S oil cooler
late 280 SL oil pan with windage tray
300 SE dual point distributor
BMW distributor cap
low impedance spark plug wires
decked block .020''  about 175 - 180 PSI compression
280 SL fuel tank
early 230 SL cam shaft
cam shaft offset key advanced to 12 degrees BTDC opening
balanced crank assembly
280 SL clutch and pressure plate
ZF 5 speed trans
LSD rear axle
cox racing bushings
22 mm font sway bar
ported and polished cylinder head
280 SL seats
power steering added
synthetic lubes though entire car
offset shifter rod ( moved towards passenger for better knee clearance while shifting into first gear )

I get 10 - 11 km per liter ( about 23 MPG ) at road speeds with this set up.



 

[GGR]

Hi Dan,

how did you select the early 230SL camshaft? Assuming by how the 230 engine worked with it? Or by comparing opening times and lift values? I am asking because in my experience, displacement influences the character of an engine relative to a given camshaft profile. So a 280 SL camshaft, even if mild on a 280, may do a better job on your 250 than the "hot" 230 one.   

[rgafitanu@gmail.com]

Dan,
I would like to understand. You have a 12 degree offset camshaft key. Does this mean that your valves open 12 degrees sooner? Are you compensating for chain stretch, match the early 230 camshaft or it is better performance combined with ignition advance increase? I am asking because this would be a relatively easy improvement.

[TheEngineer]

Be very careful when you install offset cam shaft key! You must time inlet valve #1 because if it opens too soon it will hit the piston! There is only 0.9 mm clearance between the valve and the piston when everything is working as it should. That is 0.036 inches for you Yanks. The procedure is explained in the BBB. Don't screw it up!

[Benz Dr.]

I set my valve timing to 12 degrees BTDC which is as much as you can safely go. Then I used a 230SL cam shaft because it's close to a euro 280SL cam timing and it's what I had available at the time. The offset key I used was only 3 or 4 degrees. ( I can't remember now ) and I used a degree wheel along with a dial gauge to bring it up to my desired value. And yes, I certainly did check for minimum valve clearance of of .9 mm.
Advancing your cam shaft has no effect on IP timing nor does it affect ignition timing. I wanted my intake valve to open sooner and it was the easy way to do it. Offset keys come in several options but I believe that 9 degrees is the highest you can get which is half a cam shaft tooth. This gets kind of complicated, but if you were to advance your cam one tooth (18 degrees ) and if you then used a 9 degree offset key set back 9 degrees, you would in effect, end up where you started if you used the same key to advance your cam from the same starting position. I guess this is why 9 degrees is the largest key you can buy.

[TheEngineer]

I am glad you asked: Three ways to soup-up your car:
Ram more air into the cylinders
Make the ignition timing more accurate and make a hotter spark
Reduce the weight of the vehicle
You can bypass the intake manifold heating by routing the hot water hose differently. The heating is designed for cold weather use to prevent icing. Your car is a long way away from flying in the clouds and icing-up is probably not an issue. Cold air is denser than hot air and therefore you get more air down the intake. You can install a camshaft that opens the valves more and longer. If you look at the workshop manual it reads that the 09 camshaft opens the valves sooner and closes them later. It has a base circle radius of 15.8 mm vs the 08 cam with 17mm, the cam height is about the same and that results in a higher valve lift. You get more air into the cylinders. Polishing the airways is always good. Verify that the manifold-to-block gasket does not stick out into the air path. That creates resistance to the air flow. Use solid copper wire for the ignition wires and 1 kilo ohm spark plug connectors. That reduces the resistance and gives you a hotter spark. Of course you can always hang a modern engine in there with electronic camshaft timed ignition. The newer V-6 engines are lighter and shorter. Frank Rickert at Mechatronik does that in Germany.
Reduce the weight of the car: The 230SL was really a hot car - it was kept light. No A/C:  that saves 150 lbs. No Power Steering, save 60 lbs. Remove the passenger seat and replace the driver’s seat with a light weight one. Remove the spare wheel, jack and tools. Relocate the battery into the trunk for improved handling. Take your change out of the ashtray. Leave your overweight girlfriend at home. 
That being said, these cars perform very nicely when they work as they should. We have no Autobahn where there is no speed limit. In fact, many stretches of it have speed limits now and where there is none, the average traffic moves at about 80 MPH. When you come at 120 or faster it becomes dangerous. And a Pagoda will do 120

[Bonnyboy]

And don't forget the lighter alloy wheels at all 4 corners.