Last half of 1/4 mile with M120 sucks - PeachParts Mercedes-Benz Forum

Roncallo · #1 07-10-2010, 10:59 PM

Does anyone have any time slips for a stock SL600 in the 1/4 mile. Preferably 1996 + with 722.6 trans.

I will be bringing my car to the track again and I am concerned about the last 1/8 mile of last years time slip.

60' 2.154
330' 5.927
660' 8.993
1000' 11.631
1320' 13.855

660 @ 89.160 MPH
1320 @ 101.810

The first 1/8 mile was with the open diff and crappy tires I had last year with one wheel spinning most the way. I should have that under control for this year. But I am concerned about the lack of performance in the last 1/8 mile where I don't believe any wheel spin was occurring.

The last 1/8 mile I should be running all in 3rd gear only with engine operating near peak torque (421 ft-Lb @3800 RPM) at the end of the 1/8 and finishing the 1/4 near peak HP (389HP @5200 RPM).

It seams to me I may not be getting the full potential out of this engine in the last 1/8 mile.

Also is there something I can do with cam timing as far as maybe disconnecting the actuators or powering them 100% of the time is a better 1/4 mile performance solution.

I do expect to pick up maybe 1/2 second once I get wheel spin under control, but the last 1/8 mile I haven't figured out what to do about yet. I would like to see a time slip from another SL600 that I can compare to. I'm also about 500 Lb lighter than an SL600 but have the same power train and gearing.

400Eric · #2 07-11-2010, 03:34 AM

In the (old?) video I saw of one of your runs two things jumped out at me: 1)It seemed like the car was shifting way too soon. You want to rev to about 6,000 before you shift so that the engine is right at it's torque peak when it hits the next gear. 2)It seemed way too quiet. I know it's a Benz but go ahead and free up that exhaust a little!

I wouldn't mess with the cam timing actuators.

Glad to see some folks hitting the strip!
Regards, Eric

JayRash · #3 07-11-2010, 05:59 AM

Ron,
do not touch the cams, disconnecting them or leaving them connected will not affect the top end power since they r de energized once your past 5000 RPM and dis connecting them will just have them de energized all the time thus u lose low end torque.

Check if ur air intake is sucking in hot air, i know ur engine bay is tight. also for sure free up the exhaust system, and i would assume that the stock sl600 exhaust is way too restrictive for the 6.0

Roncallo · #4 07-11-2010, 07:03 AM

Quote:

Originally Posted by 400Eric

In the (old?) video I saw of one of your runs two things jumped out at me: 1)It seemed like the car was shifting way too soon. You want to rev to about 6,000 before you shift so that the engine is right at it's torque peak when it hits the next gear. 2)It seemed way too quiet. I know it's a Benz but go ahead and free up that exhaust a little!

I wouldn't mess with the cam timing actuators.

Glad to see some folks hitting the strip!
Regards, Eric

Yes the videos you speak of are the runs I was talking about. See the link. In those videos the car is essentially a stock SL600 with a little less weight. Its shifting in automatic mode like a stock SL600 and has the stock SL600 exhaust with cats less the center resonator. My point is I believe the stock SL600 with its center resonator in place and its higher weight should do better than this in the last 1/8th mile. I would like to find some time slips of a stock SL600 to prove that.

I have taken car of the exhaust, see the link, at least as much as I care to without making the car sound like the ricer next to me in the second video. I now have a quick change straight through muffler and resonator. I can put the stock SL600 muffler on it as it was run at the track in the videos or I can put the new one on which in place the next time I run the 1/4 mile.

http://www.peachparts.com/shopforum/video-forum/255618-m120-powered-107-track.html#post2234568

Exhaust,Quiet high flow?

Roncallo · #5 07-11-2010, 07:25 AM

Quote:

Originally Posted by JayRash

Ron,
do not touch the cams, disconnecting them or leaving them connected will not affect the top end power since they r de energized once your past 5000 RPM and dis connecting them will just have them de energized all the time thus u lose low end torque.

Check if ur air intake is sucking in hot air, i know ur engine bay is tight. also for sure free up the exhaust system, and i would assume that the stock sl600 exhaust is way too restrictive for the 6.0

My air intakes sucking in hot air is my #1 concern at the moment. This is where I have a big difference between the 129 installation and my 107 installation. The stock 129 uses tiny air filters installed in large plenums, sucking cold air through a small, restrictive but well formed cold air duct. My 107 installation uses large air filters located in a hot engine bay, but they are located behind where the cold air would enter into the engine compartment at any speed (or so I assume).

For my next 1/4 mile runs I will be logging intake air temp via passenger with laptop. When I ran the 1/4 mile last time I did notice that the air filters were very hot to the touch by the time I got back to the line up area and got the hood open. Perhaps installing my cold air intakes will become a priority.

JayRash · #6 07-11-2010, 07:44 AM

Ron,
U sure are taking in the hot air feom the rads, try for once taking off the headlights and sticking the air filters out , u will find that performance will pick up especially at top end where every bit of timing advance is needed.

400Eric · #7 07-11-2010, 07:46 AM

Quote:

Originally Posted by Roncallo

Yes the videos you speak of are the runs I was talking about. See the link. In those videos the car is essentially a stock SL600 with a little less weight. Its shifting in automatic mode like a stock SL600 and has the stock SL600 exhaust with cats less the center resonator. My point is I believe the stock SL600 with its center resonator in place and its higher weight should do better than this in the last 1/8th mile. I would like to find some time slips of a stock SL600 to prove that.

I have taken car of the exhaust, see the link, at least as much as I care to without making the car sound like the ricer next to me in the second video. I now have a quick change straight through muffler and resonator. I can put the stock SL600 muffler on it as it was run at the track in the videos or I can put the new one on which in place the next time I run the 1/4 mile.

http://www.peachparts.com/shopforum/showthread.php?p=2234568#post2234568

Exhaust,Quiet high flow?

I doubt that V12 could ever sound like a ricer!

So in automatic mode, was it shifting at 6,000 RPM?

"Perhaps installing my cold air intakes will become a priority."
Yes, that needs to be made a priority.
Regards, Eric

400Eric · #8 07-11-2010, 07:48 AM

Hey Jay, did you see that video of my race with the C36?

JayRash · #9 07-11-2010, 08:27 AM

hey Eric

no i dont recall watchin it sorrry is it in ur thread? Can u relink it?

JayRash · #10 07-11-2010, 08:34 AM

found it Eric thanx
check ur thread

400Eric · #11 07-11-2010, 08:36 AM

Yes, it's in my thread..... has been for a while. Shame on you.

This is a direct link: http://www.youtube.com/watch?v=Sa5h4fq2Jkg
Regards, Eric

Roncallo · #12 07-11-2010, 01:28 PM

I'm fast coming to the conclusion that the speed posted at 1/8 mile is more than likely incorrect. I did about 5 runs that day all showing ~ 89 mph. But the 89 mph does not coincide with any of the other ET numbers by any track calculating software I have tried. It appears that 79 mph makes everything look right. Still cold air intake will be a big help and once I get the car hooked up, I would expect ET's to drop to low 13's and 1/4 mile trap speeds to increase to about 107 mph. 110 would be cool.

60' 2.154
330' 5.927
660' 8.993
1000' 11.631
1320' 13.855

660 @ 89.160 MPH Possible BS ????
1320 @ 101.810

400Eric · #13 07-12-2010, 01:32 AM

My little 4.2 pulled 78.36 MPH on a 9.442 second 1/8th mile run so I'm sure you are going faster than 79 MPH in the 1/8th. In my case, tall 2.24 gears makes for slower E/Ts than the trap speeds would indicate. In your case it may be a product of wheel spin although your 60' times are pretty good for street tires. What is your gear ratio?

Here is a time slip from a year earlier that shows virtually the same numbers: http://i9.photobucket.com/albums/a68/RivCal4Life/IMG_1177-2.jpg
Regards, Eric

Roncallo · #14 07-12-2010, 08:58 PM

Quote:

Originally Posted by 400Eric

My little 4.2 pulled 78.36 MPH on a 9.442 second 1/8th mile run so I'm sure you are going faster than 79 MPH in the 1/8th. In my case, tall 2.24 gears makes for slower E/Ts than the trap speeds would indicate. In your case it may be a product of wheel spin although your 60' times are pretty good for street tires. What is your gear ratio?

Here is a time slip from a year earlier that shows virtually the same numbers: http://i9.photobucket.com/albums/a68/RivCal4Life/IMG_1177-2.jpg
Regards, Eric

I have 2.65 gearing.

I haven't seen a time slip from another 129 SL600 but every car I've seen that has a 90mph 1/8 mile is a 110+ mph 12 second car.

400Eric · #15 07-13-2010, 12:49 AM

That C36 I raced in the video did a 9.222 @ 77.25 in the 1/8th with 2.82 gears.
The taller the gears are, the higher the trap speeds are in relation to the E/Ts.
Regards, Eric