Question: SL65 Renntech/Kleeman Mods

Subscribe
Dec 3, 2005 | 06:23 PM
  #1  
Hello everyone. This is my first-ever post.

I am seriously considering some mods on my Firemist Red SL65.

After speaking with George at RennTech and Brandon at Kleeman USA, here are my observations, along with a question.

First of all, both men were helpful, but Brandon seemed MUCH more willing to explain details and answer questions than George. Brandon also seemed much less threatened by my asking about both companies. George at RennTech seemed offended that I would even consider Kleeman products. He acted like I was an idiot for even asking the question.

Transmission: Brandon at Kleeman said he couldn't imagine what possible computer/electronic modifications RennTech might be making to the tranny. I don't understand the nature of the RennTech tranny mods, but I guess they do modify something in the tranny computer/software.

ECU/Engine: RennTech wanted to emphasize Kleeman's lack of experience in ECU mods, while Kleeman told me that there wasn't much to it, and that basically all ECU mods are more or less the same. Kleeman said that while max HP/Torque output isn't dramatically changed, the low-rpm output increase is substantial (in the +120 hp range at some rpms).

RennTech also suggested an air box, which I don't understand very well. Any opinions about the impact of the air box? I would appreciate any help here.

Hook-up: RennTech recommended some type of "link" hardware. George explained it to me, but I can't remember exactly what it was, other that it is supposed to stiffen up the rear-end substantially under heavy torque. Does anybody have any experience/opinions about these? Cost was about $1500 for parts only.

Kleeman recommended changing the Limited Slip Differential (LSD) to a true 50/50 split. I guess stock is 70/30. They said that with 50/50, ESP will engage less frequently because there will be substantial difference in wheel spin (which engages ESP) less often. They said this would help traction/wheel spin significantly. Cost was about $2300, plus an estimated $1000 in labor.

Both recommended going with lighter wheels (& slightly wider tires...Brandon at Kleeman told me that if I went with a 12" wheel an 305 tires I would probably have to have some wheel-well lip work done as well. At 11" wheel/295 tire there is apparently no problem. He also said that Michelin PS2s or GoodYear F1 tires would increase hook up/decrease wheel spin vs. stock.

Kleeman also suggested a lowering kit/module to lower the car about 22mm. Apparently this lowers the center of gravity and increases handling significantly. I am interested in any opinions/feedback on this also. I don't exactly recall, but I believe cost was around $2000.

I don't know if RennTech offers a lowering kit or not...I forgot to ask. If they do, does anyone have any preferences?

So...here's what I'm leaning towards--please give my any feedback/opions/advice you may have:

-RennTech ECU/Tranny chip
-MAYBE RennTech air box (should I do this or not????)
-RennTech suspension "link" kit
-Kleeman lowering module
-Kleeman LSD modification

I am hesitating on wheels because A) I like the look of the stock wheels, and B) Given A, I don't know if I want to drop another $10-12k on wheels/tires.

So what do you all think? Which way would you recommend I go? Am I missing anything obvious here? Am I wasting my time/money on any of the above?

I REALLY appreciate any help you can offer. I am very impressed with everyone's willingness to help each other out on this forum. There seems to be a culture of abundance mentality in this section of the forum.

Thanks again.

PS FYI, I am in Utah...4000+ foot elevation. Does this make any difference?
Reply 0
Dec 3, 2005 | 06:51 PM
  #2  
Quote: Hello everyone. This is my first-ever post.

I am seriously considering some mods on my Firemist Red SL65.
Make sure you post pictures of your car sometime soon!
After speaking with George at RennTech and Brandon at Kleeman USA, here are my observations, along with a question.

First of all, both men were helpful, but Brandon seemed MUCH more willing to explain details and answer questions than George. Brandon also seemed much less threatened by my asking about both companies. George at RennTech seemed offended that I would even consider Kleeman products. He acted like I was an idiot for even asking the question.

Transmission: Brandon at Kleeman said he couldn't imagine what possible computer/electronic modifications RennTech might be making to the tranny. I don't understand the nature of the RennTech tranny mods, but I guess they do modify something in the tranny computer/software.

ECU/Engine: RennTech wanted to emphasize Kleeman's lack of experience in ECU mods, while Kleeman told me that there wasn't much to it, and that basically all ECU mods are more or less the same. Kleeman said that while max HP/Torque output isn't dramatically changed, the low-rpm output increase is substantial (in the +120 hp range at some rpms).
Most ECU mods are fairly the same, and if it is something different, RENNtech shouldn't be saying that their modification is better because of Kleemanns lack of experience, they should be telling you details on why their mod is better than Kleemanns. Since they didn't, well you can make your own opinion from that.
RennTech also suggested an air box, which I don't understand very well. Any opinions about the impact of the air box? I would appreciate any help here.
An air box will help with helping the engine breathe, also it makes the engine bay look quite swell.
Hook-up: RennTech recommended some type of "link" hardware. George explained it to me, but I can't remember exactly what it was, other that it is supposed to stiffen up the rear-end substantially under heavy torque. Does anybody have any experience/opinions about these? Cost was about $1500 for parts only.
I personally have no idea what they are talking about, but I'm very curious so if you can get more information on that, I'd love to know!
Kleeman recommended changing the Limited Slip Differential (LSD) to a true 50/50 split. I guess stock is 70/30. They said that with 50/50, ESP will engage less frequently because there will be substantial difference in wheel spin (which engages ESP) less often. They said this would help traction/wheel spin significantly. Cost was about $2300, plus an estimated $1000 in labor.
To be deathly honest, I think the Kleemann LSD uses Spyder gearing, which will eat itself up after a few (30k?) miles. Our family keeps the cars until they die, so an LSD for us would be a no-no if that's true.
Both recommended going with lighter wheels (& slightly wider tires...Brandon at Kleeman told me that if I went with a 12" wheel an 305 tires I would probably have to have some wheel-well lip work done as well. At 11" wheel/295 tire there is apparently no problem. He also said that Michelin PS2s or GoodYear F1 tires would increase hook up/decrease wheel spin vs. stock.
Lighter wheels will always help with any kind of racing.
Kleeman also suggested a lowering kit/module to lower the car about 22mm. Apparently this lowers the center of gravity and increases handling significantly. I am interested in any opinions/feedback on this also. I don't exactly recall, but I believe cost was around $2000.

I don't know if RennTech offers a lowering kit or not...I forgot to ask. If they do, does anyone have any preferences?
I don't see a RENNtech lowering kit on their website, so unless they've added it recently, I don't think they have one.
So...here's what I'm leaning towards--please give my any feedback/opions/advice you may have:

-RennTech ECU/Tranny chip -- Do it, treynor has it if I remember right, and he loves it!
-MAYBE RennTech air box (should I do this or not????) -- while you're at the mods, why not? I think it would add to the total overall feeling of being 'complete'
-RennTech suspension "link" kit -- I need more information on this before I'd do it. Sorry.
-Kleeman lowering module -- Oh yeah. One of the things that really bites my butt whenever I look at my dads car is that it hasn't been lowered.
-Kleeman LSD modification -- No, if the above is true about the Spyder gearing.

I am hesitating on wheels because A) I like the look of the stock wheels, and B) Given A, I don't know if I want to drop another $10-12k on wheels/tires.
Getting new rims and tires won't make that big of a difference at the drag strip, unless your current tires are ****ty. The biggest difference would be you getting some lightweight rims that are small in diameter and some drag radials so you would have instant hookup.
So what do you all think? Which way would you recommend I go? Am I missing anything obvious here? Am I wasting my time/money on any of the above?
Anytime you pour money into a depreciating asset like cars, you're wasting money. The question is, will you have fun doing it!!!
I REALLY appreciate any help you can offer. I am very impressed with everyone's willingness to help each other out on this forum. There seems to be a culture of abundance mentality in this section of the forum.

Thanks again.

PS FYI, I am in Utah...4000+ foot elevation. Does this make any difference?
Utah is high up, but I don't think turbos have a problem as much as superchargers due to altitude because they 'spool' up.
However, all forced induction do lose some power as the density of air lessens.

You can get RENNtech products from neal@euroteckmotorsports.com and Kleemann products from sales@evosport.com
Mention that you saw their references on MBWorld!
Reply 0
Dec 3, 2005 | 07:52 PM
  #3  
I'll make the following observations:

I have a '05 Silver Arrow SL65 with the RENNtech ECU & Tranny computer mods, and the c/f airbox. The ECU + tranny update added a *huge* amount of midrange power (+100 ft/lbs) and a modest amount of top-end (+30 RWHP). The airbox added another +30 RWHP from 3200RPM on up, and is definitely worth it.

Since you're at altitude, you will see somewhat less peak HP and peak TQ because of reduced air density, and your turbos will spool at slightly higher RPMs. In some ways this is an advantage -- since traction and driveline stress is of course a function of uncorrected TQ, you're less likely to have major traction issues or need tranny strengthening.

So - my recommendations: skip the tranny or LSD or rear-end mods, get the RENNtech ECU & airbox, and enjoy! If you end up drag racing, get a pair of 18" AMG wheels w/275 BFG g-force drag radials from Tire Rack (that's what all the quick SL65s are running).

FWIW, I've had the RENNtech ECU for over a year now, and >40 dragstrip passes with not a single hiccup. At some point I may have RENNtech install some of their new super-secret tranny mods so I can launch under full boost and get the car into the 11.1s
Reply 0
Dec 3, 2005 | 08:04 PM
  #4  
Ricky,

Not trying to flame....

How old are you? I can't help but notice that you have a comment on everything...... I just saw you have over 21,000 posts.

WOW is that a record here?

Schiz
Reply 0
Dec 3, 2005 | 08:07 PM
  #5  
I'm 17
Yeah I do have the most posts @ mbworld.org except for Ben (Mach430) but that's rigged
Reply 0
Dec 3, 2005 | 09:36 PM
  #6  
Quote: I'll make the following observations:

I have a '05 Silver Arrow SL65 with the RENNtech ECU & Tranny computer mods, and the c/f airbox. The ECU + tranny update added a *huge* amount of midrange power (+100 ft/lbs) and a modest amount of top-end (+30 RWHP). The airbox added another +30 RWHP from 3200RPM on up, and is definitely worth it.

Since you're at altitude, you will see somewhat less peak HP and peak TQ because of reduced air density, and your turbos will spool at slightly higher RPMs. In some ways this is an advantage -- since traction and driveline stress is of course a function of uncorrected TQ, you're less likely to have major traction issues or need tranny strengthening.

So - my recommendations: skip the tranny or LSD or rear-end mods, get the RENNtech ECU & airbox, and enjoy! If you end up drag racing, get a pair of 18" AMG wheels w/275 BFG g-force drag radials from Tire Rack (that's what all the quick SL65s are running).

FWIW, I've had the RENNtech ECU for over a year now, and >40 dragstrip passes with not a single hiccup. At some point I may have RENNtech install some of their new super-secret tranny mods so I can launch under full boost and get the car into the 11.1s
I agree wholeheartedly with everything Treynor said. I have an SL600 that has the RennTech ECU and Tranny module, along with Eisnenmann exhaust. I am a drag racing nut and haven't really found any other street car to be as fast, reliable and consistent as the RennTech V12 Benzes.
Reply 0
Dec 3, 2005 | 09:53 PM
  #7  
I have been debating this stuff for a few weeks as well but have been too lazy to actually do something. What is the big difference in this airbox? Does that mean all the stock carbon fiber engine stuff will be gone? Oliver at speedtuning usa in md. said the same thing about the ecu mod. They do it for 550.00 and say it is the same thing. I have no idea what you see when you hook up to an ecu so I can't tell you if it is pretty straight forward. You would think any tuner could buy the others ecu and do the exact same changes. As far as the tcu, I am not sure what is done with that either. All I can say is that I have seen renntech v12's and Kleeman E55's at my local track and both are seriously quicker than stock. I like the stock wheels as well and would never buy wheels that needed the rear wheelwells modified. Get an extra set of rears with drag radials for the track and call it a day.
Reply 0
Dec 3, 2005 | 10:59 PM
  #8  
Don't like both companys!! I TELL YA! BRABUS ALL THE WAY!

^^ they are the best. Wait for their turbo upgrade hehe 740 horse power !
Reply 0

MB World Stories

The Best of Mercedes & AMG

Explore
story-0

6 Mercedes Models That Did NOT Age Well (But Are Somehow Still Cool)

 Verdad Gallardo
story-1

Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun

 Verdad Gallardo
story-2

Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren

 Verdad Gallardo
story-3

8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine

 Verdad Gallardo
story-4

Flawlessly Restored Mercedes 190E Evo II Heads to Auction

 Verdad Gallardo
story-5

Electric Mercedes C-Class Unveiled: 11 Things You Need to Know

 Verdad Gallardo
story-6

Mercedes EQS Gets A Major Update: Everything You Need to Know

 Verdad Gallardo
story-7

5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve

 Verdad Gallardo
story-8

Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping

 Verdad Gallardo
story-9

10 Most Reliable Mercedes-Benz Models You Can Buy Used

 Verdad Gallardo
Dec 4, 2005 | 12:31 AM
  #9  
Quote: I have been debating this stuff for a few weeks as well but have been too lazy to actually do something. What is the big difference in this airbox? Does that mean all the stock carbon fiber engine stuff will be gone? Oliver at speedtuning usa in md. said the same thing about the ecu mod. They do it for 550.00 and say it is the same thing. I have no idea what you see when you hook up to an ecu so I can't tell you if it is pretty straight forward. You would think any tuner could buy the others ecu and do the exact same changes. As far as the tcu, I am not sure what is done with that either. All I can say is that I have seen renntech v12's and Kleeman E55's at my local track and both are seriously quicker than stock. I like the stock wheels as well and would never buy wheels that needed the rear wheelwells modified. Get an extra set of rears with drag radials for the track and call it a day.
Sorry we missed you on Friday at the track. We had 2 E55's that ran the 1/4 mile in 11.52 and 11.63 and trapping 122/123 mph. Not bad for a 4 door that is over 4000 pounds
Reply 0
Dec 4, 2005 | 01:56 AM
  #10  
Quote: I'll make the following observations:

I have a '05 Silver Arrow SL65 with the RENNtech ECU & Tranny computer mods, and the c/f airbox. The ECU + tranny update added a *huge* amount of midrange power (+100 ft/lbs) and a modest amount of top-end (+30 RWHP). The airbox added another +30 RWHP from 3200RPM on up, and is definitely worth it.

Since you're at altitude, you will see somewhat less peak HP and peak TQ because of reduced air density, and your turbos will spool at slightly higher RPMs. In some ways this is an advantage -- since traction and driveline stress is of course a function of uncorrected TQ, you're less likely to have major traction issues or need tranny strengthening.

So - my recommendations: skip the tranny or LSD or rear-end mods, get the RENNtech ECU & airbox, and enjoy! If you end up drag racing, get a pair of 18" AMG wheels w/275 BFG g-force drag radials from Tire Rack (that's what all the quick SL65s are running).

FWIW, I've had the RENNtech ECU for over a year now, and >40 dragstrip passes with not a single hiccup. At some point I may have RENNtech install some of their new super-secret tranny mods so I can launch under full boost and get the car into the 11.1s
Thanks to everyone for the feedback. Ben, I think I'll take your advice and go with the RennTech ECU/Tranny upgrades along with the airbox and leave everything else alone for now. I asked the RennTech guy about you, and he said you really know how to drive. Any driving tips for an amateur, particularly in the area of controlling wheel spin?

By the way, has anyone else ever seen a Firemist Red SL65 before? I bought mine right off the local dealer's showroom floor, but I've never seen another one that color, online or on the streets (we only have about 3 SL65s in all of Utah...)

I'll post pictures one of these days...(that requires effort, which I generally avoid! LOL.)

By the way, I also have a Cayenne Turbo and an Escalade ESV with an XS-500 package (Supercharged--500+ hp, Stoptech brakes, dual exhaust, & lowered 2.5"), as well as a Big Dog Pitbull chopper. Any opinions on any of these vehicles?

Thanks.
Reply 0
Subscribe
Currently Active Users (1)
 
story-0

6 Mercedes Models That Did NOT Age Well (But Are Somehow Still Cool)

Slideshow: Not every Mercedes design becomes timeless, some feel stuck in the era they came from.

By Verdad Gallardo | 2026-05-12 18:09:07


VIEW MORE
story-1

Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun

Slideshow: Yes, Mercedes built manual cars, and some of them are far more interesting than you'd expect.

By Verdad Gallardo | 2026-05-02 12:36:58


VIEW MORE
story-2

Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren

Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.

By Verdad Gallardo | 2026-04-29 11:19:28


VIEW MORE
story-3

8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine

Slideshow: Before curves took over, Mercedes mastered the art of the straight line, and some of those shapes still look right today.

By Verdad Gallardo | 2026-04-25 12:05:49


VIEW MORE
story-4

Flawlessly Restored Mercedes 190E Evo II Heads to Auction

Slideshow: The 190E Evolution II shows how a homologation necessity became a six-figure collector icon.

By Verdad Gallardo | 2026-04-22 17:53:47


VIEW MORE
story-5

Electric Mercedes C-Class Unveiled: 11 Things You Need to Know

Slideshow: Mercedes is turning one of its core nameplates electric, and the details show just how serious this shift is.

By Verdad Gallardo | 2026-04-21 13:58:06


VIEW MORE
story-6

Mercedes EQS Gets A Major Update: Everything You Need to Know

Slideshow: Faster charging, longer range, and a controversial steer-by-wire system define the latest evolution of Mercedes-Benz EQS.

By Verdad Gallardo | 2026-04-15 10:35:34


VIEW MORE
story-7

5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve

Slideshow: These overlooked Mercedes-Benz models never got the spotlight, but they quietly delivered more than most remember.

By Verdad Gallardo | 2026-04-13 19:35:45


VIEW MORE
story-8

Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping

Slideshow: A well-used 1991 Mercedes-Benz 300D with more than one million miles is now looking for a new owner, and it still appears ready for more.

By Verdad Gallardo | 2026-04-10 10:05:15


VIEW MORE
story-9

10 Most Reliable Mercedes-Benz Models You Can Buy Used

Slideshow: From bulletproof sedans to surprisingly tough SUVs, these Mercedes models proved that the three-pointed star can go the distance.

By Verdad Gallardo | 2026-04-08 09:55:49


VIEW MORE