fine tuning a 230 sl

[merrill]

finall got the 230 back on the road and took it for a spin this morning.

I went 144 km about 84 miles and consumed 6 gallons of fuel.
(filled up before and after )
this comes out to about 14.4 mpg.  most of the drive was at 100 kmh or about 60 mph on the hwy so most of the drive was at speed.

timing is at 28 deg at 3000 rpm.

I noticed that there was pinging during accelleration which quieted down once I got up to speed.
did the richness test and the rpms go up about 75 rpm.

I am wondering if the linkage is causing the car to run rich thus causing the pinging. I have everything set per the linkage tour.

thoughts?

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Benz Dr.]

That's close to 22 liters to travel that distance. My car will do that in about 15 liters but it has a 5 speed so it will use less.
You might want to check your cold start valve. I picked up nearly 4 miles per gallon once just by fixing a leaking valve.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[merrill]

dan,
hans rebuild my cold start selenoid valve, I sure hope it is not leaking.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Benz Dr.]

Take the small screw out under the solenoid ( 7mm head ) and turn the ignition on to start the fuel pump. Ideal is nothing coming out of the hole but you can have up to 3 drops per min without it affecting the idle mixture very much. Any more than that and you will start to have rich running problems. I've seen them simply start to leak for no reason even if they were working fine the day before.
There's only two places where excess fuel can enter the engine. Through the injection system or the CSV. My bet is the valve but you should check the injectors next if you have everything else working OK. Ignition problems will also affect fuel consuption so you definately want to start there first and make sure you have good wires ( no carbon core junk ) and everything else in top form.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[ja17]

Hello Merrill,

If your car is pinging  you are wasting fuel. You should be using high octane fuel. Also check your compression to make sure it is not too high.  Sounds like you have a ignition timing issue rather than a rich running situation.

Joe Alexander
Blacklick, Ohio

[merrill]

Joe,
timing is set per the manual, I could try to retard it a little.
It is already retarded at 28 btdc deg at 3000 rpm,  manual states it should be 30 deg btdc

I am using 93 octane fuel,
I will check the cold start selenoid this weekend.

motor is new, just about 550km on it.



Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[Shvegel]

Hi,
You might also try Sunoco 94 octane if you have it in your area. I have my engine tuned to the 94 octane fuel and it pings on 93. Also be carefull of 93 octane fuel if you are buying from stations along the highway. More than once

I have had to retard my timing due to cheap fuel bring sold as 93 octane.

[enochbell]

Matt,

The pinging is probably related to timing, at least that is my experience 99% of the time.  Well, if you have serious carbon buildup on piston crowns and head that can also do it, but it would have to be pretty bad (and the engine may also run on after shutting it off, if this is the case).  I would suggest making sure the dwell is spot-on, once that is perfect then go to timing.  Depending on the history your engine has (timing chain condition, offset keys, sprocket wear, functioning of the advance mechanism, patency of vacuum line, and the like) the best timing may not actually be "by the book" with your timing light.  Pinging is bad bad bad for the engine, you should correct asap.  I would try setting the distributor by "feel" and "sound" and you may acheieve better results than trying to hit the RPM/timing marks exactly.

Just my 2 cents,
Best,
g

'64 230sl, fully sorted out...ooops, spoke too soon

[Benz Dr.]

If your engine runs OK on 94 but pings on 93 you have way too much timming advance. I'd turn it back at least a few degrees. My engine has around 175 - 180 PSI ( more than 9.5 ) and it will run fine on 91 but runs better on 94. I can feel the difference but there is no pinging. Even if you can't hear it you can still be doing damage.
These engines were originally set for 98 so you have to turn the timing back a little bit. Every engine is different - some never seem to run right.....

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[merrill]

Dan,
pulled the 7 mm bolt from the cold start selenoid, disconnected the wires to the selenoid and then turned the ignition on.

not a drop of fuel came out.  guess the css is not leaking.

I will try to retard the ignition to see if than changes the pinging

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

so, pulled the inj pump today to verify it was timed correctly and yep it was dead on.

while I had the fuel rail off I decided to do the valved, wow, most were loose, tightened them up a little.  the car seems to idle very smoothly now.

I am going to revisit the linkage tour now to make sure my linkages are correct.

more to follow

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

so,

thursday torqued the head (600 km) on rebuilt motor - warm
friday adjusted the valves - dead cold
saturday hooked up the gunson gastester.  

first reading co% at 8
backed off inj pump -3 turns,  re read down to 6.9
backed off inj pump -3 turns   re read down to 5.9
backed off inj pump -3 turns   re read down to 4.5

I will re check tomorrow and see if I really am at 4.5

One question I had was hans had a .5mm washer on the barometric pressure tuna can.  We added a 1.4 for a total of 1.9 mm.

I am wondering if I should have just removed the .5 mm washer rather than back off the inj pump -9 clicks?

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[hands_aus]

quote:Originally posted by merrill

so,

thursday torqued the head (600 km) on rebuilt motor - warm
friday adjusted the valves - dead cold
saturday hooked up the gunson gastester.  

first reading co% at 8
backed off inj pump -3 turns,  re read down to 6.9
backed off inj pump -3 turns   re read down to 5.9
backed off inj pump -3 turns   re read down to 4.5

I will re check tomorrow and see if I really am at 4.5

One question I had was hans had a .5mm washer on the barometric pressure tuna can.  We added a 1.4 for a total of 1.9 mm.

I am wondering if I should have just removed the .5 mm washer rather than back off the inj pump -9 clicks?

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

The acceptable CO% range is 3.5-4.5
Maybe a further 1-2 clicks will bring it down closer to the bottom end of the range.

It would be interesting to know how the car goes when you go to the hills/mountains given the barometric compensator is no longer set up as per factory.

I would do the linkage rod test just to see how accurate the Gunson tester is.
Don't forget you can look at the colour of the plugs and the exhaust.

Have you noticed the responsiveness of the car change as you do the Inj pump adjustments?

I ask because I find if my car is adjusted either too lean OR too rich it runs very poorly. Correctly adjusted and it goes great.

Bob Smith (Brisbane,Australia)
RHD,1967 early 250 SL, auto

[merrill]

so,

took the car for a short drive today, got it warmed up.

got home tested the exhaust.

the outer pipe was at about 4.4 - 4.5 % co
the inner pipe was at about 4.2 - 4.3 % co

did a richness test and the idle barely increased and the motor tried to die.


the motor still pings a little,  i am using 93 octane timing is 27 deg at 3000 rpm.

new rebuilt motor, 600 km on it, just torqued the head, adjusted valves. new points, plugs, coil, ballast, condenser.
checked cold start valve  no leaks, cold start thermostat works.

I am using ngk BP6Es.  I am wondering if I should go back to WR9DC's?

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230

[merrill]

oops, I think I found out why I was hearing pinging when accelerating.

I had non resistor ngk bpe6's gapped to 35 - 36 which is for resistors

re gapped the plugs to 31 - 32 and the car really starts better now.

I guess I will take it for a test drive next to see how it runs.
I will probably have to re check the exhaust

by the way the plugs were really really clean.

Matt
Austin Tx
66 230 sl - "white"
78 300 D - Blue
98 C230