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'94 SL600; '65 Belvedere I; '65 Coronet; '67 Fairlane; '71 Satellite; '78 Pace Car & more
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Discussion Starter #1
I'm fishing for ideas concerning perfomance modifications of the SL600 with the only current restriction being that the motor is not opened. As you may be aware, perfomance parts are not readily obtainable, short of a major stroker engine package for $20,000+ The goal is to have an overall mix of handling and perfomance. I want the car to run to full potential, not emission bogged potential.
My car is a 1994, and has 87,000 miles with questionable plug wires, 02 sensors; and spark plugs. (I've not replaced these items yet, and some parts look really original) I intentionally looked for a 1994 or 1995 car because the value was less, emissions were pre-OBDII, and I was convinced that the car could be made to run better than all the literature I had read after driving three or four candidates.
I picked my car up in Beverly Hills from a heart surgeon last year -- then immediately drove it 1550 miles home. I was not satisified with the performance of the stock car, it seemed lethargic in responsiveness. I could sense and hear the car loafing -- at least it was not sharp in response. In particular, the transmission and gearing were too efficient. The engine began moving the car right off idle (ie. 600 rpm), so there was no snap when floored, even in first gear. Don't get me wrong, the car ran well, but did not have the right tone or responsiveness from the engine or driveline.
I've done the following to my 1994: 1) Split the airboxes open at the seams and removed the foam deadening material and ground out the reinforcing ribs to gain better added cfm and airflow, then reassembled them; 2) K&N airfilters; 3) eliminated the 1/4 inch honeycomb MAF screens on the intake side and replaced with regular thin screens like on the back of the MAF; 5) Removed the rear muffler and fabricated a stainless race muffler replacement with a three inch diameter outlet; 6) Modified the cats; 7) ECU perfomance chips; 8) New caps and rotors; 9) and a much bigger and wider set of tires and rims off a new CLS series. Best measured performance by G-Timer is: 4.95 0-60; 13.35 1/4 mile; 106mph trap speed. The car will not spin the tires unless power braked.
Future modifications include: plugs, wires, O2 sensors, stall converter (about 2000 rpm), elimination of the middle muffler, first gear enabled starts in drive, stiffer front springs, new front struts and new a-arm bushings. Every modification so far is reversible, and the original parts have been saved, and can be can be reinstalled.
Is there anything else other than possibly altering timing with off-set keys in the rotor assemblies to gain static advance (not sure if this will work with the computer controlled ignition), raising the compression to 11/1 with head milling and some porting; installing a device to quicken throttle response, and installing some type of limited slip parts in the rear differential for traction with the stall converter effectively lowering the gear ratio?
Any suggestions would be appreciated.
-- Thanks - Mike.
 

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The sl is not a pure racecar. The 600 is made for people who want lot's of 'smooth' power & still have a lot of comfort. It is normal for an automatic transmission that it will move the car on idle, this is exactly done to make it smooth, it is meant not to snap when floored.

If U want to make it a racer then U should modify a lot about it, strip it completely down, only use components that a race car needs, remove electronics, replace/remove heavy stuff, add wings, lighter manual transmission and so on...

IMHO this is a bad idea, all the adbove will help but U will never get the real race performance out of it because of aerodynamics and weight.
Sure it'll be fast in straights but it's just too heavy to take fast corners like a real racecar.

Also most people will find it difficult to drive cause of the bumpy behaviour which is very tiresome so it will be very difficult to re-sell it later on. By adding all this modifications u will decrease the car's re-sell value while U have pumped a lot of money into it. Unless U are absolutely sure U are going to keep the car untill it dies I wouldn't do it.

If I had the money i'd buy a porsche to race and a sl for everyday use...

It all depends how for U wanna go, it's do-able but not an easy job.

I'd like to be proven wrong though ;-)

Good luck!
 

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'94 SL600; '65 Belvedere I; '65 Coronet; '67 Fairlane; '71 Satellite; '78 Pace Car & more
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Discussion Starter #3
Jomzo

I appreciate your imput. A 911 Turbo is already in the future. I am not trying to make the SL600 a racer, but there are improvements that can be made. Also, I don't think resale value on my year will ever be that good, and I can convert back to original parts. In my part of the country, the roads are fairly straight so acceleration is king. I will post results as modifications are made.
 

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Im rooting for you Michael. I know you can, and will find ways to make that beauty accelerate like a bat outa hell.

If I come across anything durring my hunt, I'll be sure to post it here for you.

In the meantime, Good Luck
 

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1995 sl 500 red/black w/renntech wheels
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Tech-Tune said:
Im rooting for you Michael. I know you can, and will find ways to make that beauty accelerate like a bat outa hell.

If I come across anything durring my hunt, I'll be sure to post it here for you.

In the meantime, Good Luck
i really would like to see more pis of your car man ,....:D
 

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My next thread is going to be a picture thread.
Just as soon as I'm done doing some custom paint work under the hood. ;)
 
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Do yourself a favor and just get yourself the 911 Turbo now. I drove a genuine SL73, and even after that, I went with the 911 Turbo. If you want true high performance, there is just no place for all of that weight.

Also, you should NOT have removed those honeycombs. Thos honeycombs are aerodynamic devices that smooth out the airflow and form it into a specific pattern so that the MAF can accurately process it. If you end up with a tuning issue or check engine light in the future, I guarantee you that is where it will come from.

Good results otherwise. Take it to the track and see if your Gtech results are accurate.
 

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Dont listen. 911 Carrera's are slow. Even when they are 1000lbs lighter. LOL
 

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R129 SL300 Turbo,R129 SL600, W109 300SEL 3.5 ,W108 300 SE 3.5, R170 SLK 200K Brabus
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post some pics of the mods you have done please (if taken)
 

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MB SL600, MB 380SE, Suzuki Grand Vitara, 38' Chris-Craft, Volvo V70XC, and my own two feet...
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I had a stock 911 (996), and also a supercharged boxster. Both were slower than my stock SL600. Much slower. Which is why it boggles my mind that the "official" 0-60 figures are so much quicker for the 911, but in the real world it's really a noticeably slower car.

And compared to the nice cushy ride and interior of the Benz, both my Porsches were like driving a go-cart. Wind noise, rattly, very high levels of engine noise in the cabin. Honestly, totally disregard the advice about "if you want a performance car, then get a porsche". Been there, done that, and am far happier with my Benz.

And I wish we had found this thread earlier, because we could've saved the OP tons of money! All he needed was a 1st-gear start module, his problem wasn't lack of adequate power, it was that silly 2nd-gear start that the pre-1995's have. That was his performance problem.
 

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R129 SL300 Turbo,R129 SL600, W109 300SEL 3.5 ,W108 300 SE 3.5, R170 SLK 200K Brabus
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NOTHING. Bone stock. 911 has slips showing his 12.9. I just got a vid of me beating him.

No slips, no times. Midnight drags. Money races.


;) now you are talking!!! hehe
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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You might want to consider a 722.6 5 speed transmission with a PCS stand alone controller. 5 speeds is really nice. Also it sounds like your engine may be having some wiring problems like cams not moving etc.
 

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R129 SL300 Turbo,R129 SL600, W109 300SEL 3.5 ,W108 300 SE 3.5, R170 SLK 200K Brabus
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You might want to consider a 722.6 5 speed transmission with a PCS stand alone controller. 5 speeds is really nice. Also it sounds like your engine may be having some wiring problems like cams not moving etc.
mmm that's interesting! more details please!
 

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1997 SL600 Brilliant Silver Sport with grey/dark metal interior, 234K miles
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Best of luck with the K&Ns on a 600. Plan on replacing your MAFs down the road.

I also concur with the dubiousness of the "hog out the MAF screen" mod, as I think the MAF actually flows better with the directional grid.

Also, those are pretty quick 0-60 times for a 4400lb car (minus driver) on original rims where a stock V12 posted 5.9 sec. Looks like your tuner mods netted you about 200+ HP, bravo.
 

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Best of luck with the K&Ns on a 600. Plan on replacing your MAFs down the road.

I also concur with the dubiousness of the "hog out the MAF screen" mod, as I think the MAF actually flows better with the directional grid.

Also, those are pretty quick 0-60 times for a 4400lb car (minus driver) on original rims where a stock V12 posted 5.9 sec. Looks like your tuner mods netted you about 200+ HP, bravo.
That 5.9 figure published by MB is nowhere near accurate.

Mercedes continued using the same original performance figures for the V12 all the way from 1993 through the end of the production run, even though multiple upgrades were made to the car over the years which greatly improved its performance.

Over the years, the car picked up variable valve timing, a 5-speed electronic transmission that replaced the 4-speed hydro unit that started off in second gear, revised throttle bodies, etc., etc. The transmission change alone is probably good for shaving around a full second off the original 0-60 figure, because the 5-speed starts off in 1st, while you have to hit the kickdown switch and wait a second or two for the 4-speed to downshift into first before you really get going..

In my experience, the real-world performance of the car is closer to <5 seconds, especially when the weather is cold and you don't lose traction.

If you don't believe me, get or borrow a gtech or get dynolicious on an iphone, and time your car. You will be very pleasantly surprised if you're expecting a 6 second run.
 

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1997 SL600 Brilliant Silver Sport with grey/dark metal interior, 234K miles
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I've owned and driven sub 5 sec 0-60 cars (all over 500+HP and much lighter) and my 1997 4400lb 389HP SL600 isn't one of them. The SL is fast but hardly quick.

Never the less, the starter of this thread should be congratulated on his amazing tuner accomplishments.

Who of thought that hogging out the airboxes and MAF grids and not improving the skinny snorkles than snake past either side of the radiator would add up to so much performance improvement.
 

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I've owned and driven sub 5 sec 0-60 cars (all over 500+HP and much lighter) and my 1997 4400lb 389HP SL600 isn't one of them. The SL is fast but hardly quick.

Never the less, the starter of this thread should be congratulated on his amazing tuner accomplishments.

Who of thought that hogging out the airboxes and MAF grids and not improving the skinny snorkles than snake past either side of the radiator would add up to so much performance improvement.
My 996 was a published <5 second car, and the SL600 pulled it from a roll. Go search youtube, there is a video of an R129 SL600 hanging right with an E46 SMG M3, which is a published 4.7 second car. And that car was a 1993 with the 4-speed tranny, the newer ones are much quicker.

We can go back and forth all day on this. Maybe something's wrong with your car?
 

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And you should dyno your car. Something might be wrong. Mine put out 316rwhp on a 103f day with 80%+ relative humidity, and 2 bad o2 sensors. That equates to around 395 at the flywheel, and if you corrected for the terrible atmospheric conditions, then the figure would be well north of 400, probably closer to 410+. The motor is underrated from the factory.

My dyno sheets are floating around the forum somewhere, you're welcome to do a search and look at them yourself. I'm not just pulling this outta nowhere. My own experience with my car is low 5's during most of the year, and much quicker when the temperatures are under about 50f.
 

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The E46 M3 with SMG is a 4.7 second car. So explain this, if you really think the 600 is a 6 second car:


And again, the later model 600's with the updated TB's and the 5 speed tranny are much faster than the 4-speeds.
 
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