RENNtech will most likely have some kind of Black Friday discount (usually 15%) on their tune, so I am looking to take this opportunity to reliably bump up some power figure on my 2020 C63 S Coupe.
They recommended Intermediate ECU tune for my car as I live in California with crappy 91 octane fuel.

On their website, Intermediate tune gives gains of +48 HP and +80 LB-FT Torque.
However, this gain is based on non S car, so I assume that actual gain on my S car would be much less.
So I am looking to get some input from C63 S owners who put RENNtech Intermediate tune (not regular stage 1 tune).

 

I looked into Rentech tunes too, but I’m worried about voiding the warranty. Does that not concern you?

 

I had my car for little bit over 2 years now, so I am pretty confident that engine in my car is reliable.
Still, I want my car to run without issue after the tune. That's why this mild, everyday drive-able tune from RENNtech seems like the best choice to increase HP/TQ on it.
I would be totally hesitant to put a tune from other companies that focus on extracting every bit of power from this engine.

 

RENNtech just started their black friday sale (15% off).
Price on this tune is now $2091 instead of $2460.
I will probably just go ahead and purchase this.

 

I've come close to purchasing the regular stage 1 tune but haven't (I've spoke to Renntech a few times with questions) -- let us know your thoughts after you install.

 

I just placed the order @ discounted price.
However, minimum shipping fee for the slowest shipping method (UPS ground) for the device is $50 to California... I guess they had to add MB tax to the UPS shipping too haha.
At least, they do not charge actual California tax on this device.

 

Definitely post an update after you load the tune and get to feel it out. I'm also considering their tune, along with a few others.

 

I just ordered their full tune. I'll update how it goes as well. Definitely one of the convenient aspects is being able to revert to stock in a few mins without a laptop.

 

Any RennTech performance updates to share?

 

Mine should arrive today if not tomorrow. I will post some impression once I get some drive time with the tune.

 

I just got Intermediate Renntech tune yesterday.
Here is the quick impression.

Installation:
This was super simple and quick. Just connect the handheld tuner device to the OBD port and wait for the red light on the device to turn green. It took less than 2 minutes to fully tune the car.

Driving impression:
I have following performance mod already installed on my car prior to the tune.

• BMC high flow air filter
• UPD intake spacer
• Red Star downpipe with GESI 300 Cell cats
• Michelin P4S (265/35/19 Front & 305/30/20 Rear)

I can feel significant power increase over the stock tune even though the tune I got is only intermediate level tune (optimized for California gas).
With stock tune, car’s power would die quickly during the acceleration around 4.5k rpm.
With Renntech tune, car pulls significantly harder and keeps pulling hard until the redline.
Michelin P4S probably would be the most important upgrade you should get together with the Renntech tune because I don’t think stock PSS tires would be able to handle this increased power that well.

I also prefer tune that is not the most powerful, but one that is as smooth as the factory tune.
When I had BMW F80 M3 with Bootmod3, I always ended up using either factory M4 GTS or M4 CS tune even though I had 2 different custom tunes purchased.
While custom tunes make car pull harder, it usually cannot match factory drivability.
I am happy to report that my car with Renntech tune feels as smooth as factory tune but with more power.

Overall, I am very impressed with the tune. It feels like power is getting better the more I drive the car!

 

Hmmmmm - I was hoping more for "HOLY **** THIS TUNE IS INSANE BECAUSE...."

I wonder if your previous mods impacted the 4.5k issue you describe above, my car (stock) has no such problem, it routinely puts big grins on passenger faces

 

Maybe I should have written that part better. What I was trying to say is that with the stock tune, push back to the seat feeling that you get during acceleration flattens out as RPM needle passes around 4.5-5k RPM like most cars with small factory turbo do.

 

*****A decent tune can certainly help our cars for sure. Unless you are running race gas or have other supporting modifications like methanol, downpipes, etc.. , the capitalized "TUNE IS INSANE!!!" for folks already used to their cars already fast performance is probably not going to happen. Passengers used to more pedestrian cars are generally impressed by riding in a nice C63s or other such car, tuned or not. It's a fast car from the factory.

Renntech is a great company that makes really nice products, but they are selling tunes for the mass market and thus have to err on the side of safety to mitigate the chances of someone with a poorly maintained car or a car with problems in general doesn't just break outright. I've seen several owners of cars of various brands including ours try and make a car that is not running well better by buying a tune or whatever, versus first making sure their car is running well. They have X money to spend, and it isn't as glamorous I guess to maximize what they already have versus just bolting on an aircleaner or buying a tune, etc..

Plenty of people are ecstatic with their new tune of course, when they buy it and install it, but few people do before and after Dragy or dyno numbers to assess if the tune did what it was supposed to do. They assume it does what it purports to do because it cost $2k or whatever but they don't test to verify. Having actually tested several cars on a dyno I can state with some conviction that most people's butt dyno sucks, mine included, and I do most of my own work on the cars and have access to a dyno, etc..

I have been surprised myself after upgrading various parts on my cars with the latest and greatest and "feeling" like the car is super duper powerful now, to find that the car lost HP and torque, and is now slower because of a bad coilpack, or a purge valve is sticking, or a wastegate diaphragm is torn and leaking, or because the boost and AFR tables were off on the tune and causing massive timing retardation and wastegate boost bleedoff, etc.. At the 500hp level, losing 50hp or gaining 50hp is just not that noticeable in my experience. At the 750hp level, even less so - the car is still stupid fast at 750hp or 700hp.

Most people just want to buy their tune, install it, and be done with it. If your car has seemingly minor running issues before the tune, you'd be surprised at how much a "minor" issue will suck most of that 75-100+ (or whatever is advertised..) hp gain you are purportedly supposed to get with just a tune, just from pulling timing from a leaky injector, or air in the cooling system, a bad plug or coilpack, etc..

If it can be broken, it can be fixed or tuned I always say. Unfortunately, most people may not have the scan tools or data/other tools to verify their butt dyno's exuberance after dropping $2k+ on a tune for their cars, before another $1k for a TCU tune once the original tune didn't quite do what it was supposed to do so of course just buy more performance parts to make up for a cavitation issue in an intercooler that a decent mechanic or tuner seeing the actual car could spot with a few simple tests and some experience with these cars, or any cars..

Pic below of a C63s missing one or two things...Admittedly, pretty big things...

 

Also, main reason why I did not feel the initial “oh **** this tune is insane” is because I have another car that has significantly faster straight line acceleration than C63s (2022 M5 Competition). So no matter what I do to C63s (other than upgrading turbo with supporting mods), it would be pretty hard to make my C63s feel faster than M5.
However, the Renntech tune is feeling even more powerful and smoother now that the initial adaptation is complete. I am just happy that the tune gave extra power to my C63s so that it does not feel so slow anymore compare to M5.

By the way, I just noticed that Renntech increased the price on their tune after the Black Friday sale.
Now, the intermediate tune is over $2800 (used to be around $2500) and regular stage 1 tune is over $3000!
I am glad that I picked it up during the sale for $2100.

 

I've just put on the full Renntech tune. Install was easy. Took 1 minute. Some error messages popped up on the dash regarding the diff lock and ESP etc but that's expected as per the instructions. You switch the car off and on twice and they clear. The quickness in which it was all done had me questioning if anything was done at all. The manual said 2 mins and could take up to 5 mins.

Ive been on 2 drives so far on 93 octane and running Pilot sport cup 2 tires. Honestly I was also expecting obvious butt dyno improvement. But the truth of the matter is that at low speed it's easy to spin the tires with or without the tune, so it's very hard to judge. We have alot of power regardless down at low speed, so any additional won't be felt without the grip.

Flooring it at higher speeds, 70mph and above, I have to say I expected to be pushed deeper into my seat for longer as the car accelerates. But it felt similar. I think it's hard to judge a few milliseconds of improvement on a 500+ hp car. I purposely didn't tell my wife anything has changed, hoping she'd make a comment that would convince me something's different, but apparently "why don't you like truffle pizza?" was occupying the conversation, her mind and butt sensors.

I like to believe Renntech know what they are doing. I went with them in the first place cause I didn't want anything over the top. Some manufacturers push the limits that would eventually fry some internals down the line. I believe as Renntech are Mercedes certified, they would keep everything within limits and reason. Like putting regular poor-man's toppings on pizza, the way it should be, and not over the top fancy "truffles".

 

*****Folks have to be somewhat realistic in terms of what to expect from a tune with normal 91 or 93 octane gas and perhaps stock or near stock everything else, and in my experience they generally have unrealistic expectations of just what certain modifications will do, how it will feel, etc..

The C63s car is already a 500hp car - it is quite fast and if anything blows the tires off at lower speeds already. A tune will only get you so much, same with an air cleaner upgrade (intake..), or downpipes, cat back exhaust, etc... The numbers are somewhat out there if you search as to what to expect with certain upgrades, and I totally get people want the most bang for their buck. I see plenty of car enthusiasts who read about certain improvements (30+HP from an air cleaner, or 10+ from some optimized spark plug with new tech, 5+ Hp from a sticker that says "+5 HP sticker" and figure if they buy all of those bolt on products that the results are cumulative (30+10+5+ whatever) and now they have a 550HP car, or if they get a tune their car now produces +80hp and + 100ft/lbs of torque, etc.. You can read the fine print on most of the products out there and it usually says something along the lines of "with supporting fuel and other modifications.." Most people seem to kinda gloss over that caveat and most consumers probably won't be getting their cars dyno'd to verify what improvements they have gotten, or perhaps taken the car to the track, Dragy numbers, etc..

Turbo cars are somewhat easier to get big number improvements out of than non inducted cars as you can turn up the boost to the limits of the fuel being used, and make other adjustments to the AFR ratios, etc.. to optimize the car with the components on it. Bigger turbos can produce some big gains at higher boost levels without producing excessive power robbing heat that a smaller turbo being spun beyond its volumetric efficiency might be able to do. Typically, the bigger turbos will shine at higher boost levels and can flow some serious air, but fueling needs to be there or you and the wife might end up walking to get your truffle pizza after something (probably expensive) breaks.

Having spent some time working with a variety of platforms over the years, and spent some time optimizing on a dyno, people are often surprised at just how little or how much a "mod" can make on a car. Bottlenecks are a big issue. An example would be a big block Chevy (say a 396 or 427 cu inch motor since I have experience with that platform), with a mild supercharger produces say 800 hp on race gas and in a light enough car on a well prepped track runs a 9.8 quarter mile time at about 144 ish mph trap speed.. For giggles, we make ONE change to test restriction and decide to put the stock air cleaner back on which is in an enclosed metal container and is perfectly fine on a stock motor, which produced about 360hp with the stock exhaust manifolds, pump gas, and no induction (supercharger).. We re-test and our formerly 800hp car is now a 680 hp car... Is it fair to say, if we were selling "optimized" air cleaners that our air cleaners can increase HP up to 120hp??? Totally extreme example of course, but the "supporting mods" thing I think sometimes escapes folks looking to increase the performance of their cars.

There's safer stuff that can be done to improve a cars performance of course, and a good tune is one of them. Just realize that a butt dyno on an already pretty fast car is most likely not gonna pick up improvements that a person can feel. Even heat soak, which can reduce hp by a LOT more than most tunes or typical basic add ons (intakes, exhaust, etc..) will add is often not that noticeable without measurement for most people. One of my first tests on the dyno with my stock at the time C63s was done and it hit 415-425 ish WHP (at the wheel...) which is what was to be expected assuming 15% or so driveline losses, etc.. Car got heat soaked as it was a very hot and humid day and even with the big dyno fans the next pulls never broke 380ish on subsequent tests after the car got hot. 425 hp to 380 whp is quite a bit of net loss (about 52 ish or so flywheel HP), and as an aside *many* popular bolt ons (intakes, DP's, cat back exhausts, etc..) produce a LOT less improvement in the car then the loss we got from just having a normal car heat soaked..

Anyway, a tune is a great option for those that don't want to dig into their cars too much and get some decent improvements in performance. Just don't think getting a tune is going to turn an already fast car into something only more extensive modifications including harder mods like turbos, coupled with exhausts, etc.. will do. It can get expensive in some ways when you push the envelope a bit...

Pic below of an envelope that was pushed a bit too far, Too much blow as they say.. We saved one of the air cleaners and a PCV valve on the motor below.. Bad day at the track!

 

A more quantitative update after a few more days on the tune:
I tested using the OBD Fusion App and a OBD adapter.
The boost does show an increase from previously. I used to get 17psi at wide open throttle, that's now 19psi. So somethings changed there.
I did multiple runs from 100km/h to 200km/h (approx 60 to 125mph) using the same stretch of road i tested on before the tune, and the temperature is cooler now then it was back then. I am aware that other factors such as pressure and humidity come into play being its a different day, but I really hoped the added 2psi (and other tuned parameters) would still show an improvement.
I could not improve my best time pre-tune last week as much as i tried. Nor could i maintain my average time. I was around 0.4 to 0.5 seconds off my usual pace.

 

*****Hmmm. Interesting. Does the app you use record your run data? Is your car pulling timing due to knock or pre-ignition? If the temps are cooler and the car is not heat soaked, it should be faster than pre-upgrade, even with higher humidity, etc.. You might wish to consider dumping a gallon or two of 100 or 104 unleaded and see if the car improves its testing time as an experiment. Record the data if possible and keep an eye on timing advance, boost, as well as engine and transmission temps - see if the numbers have markedly changed. I think you mentioned your car is otherwise completely stock. How many miles on the car, and has the transmission been serviced? A loss of .4 to .5 seconds is quite a bit of time lost, versus pre-upgrade.

Since it is a RennTech module, set it back to stock and re-test and see if the car picks up its lost time - if so, something is wrong with the tune and your car is not liking it for some reason. It isn't necessarily RennTechs fault if there is some type of issue with a faulty sensor, or coilpack, injector, etc.. The car will somewhat try and protect itself if it detects something amiss, particularly AFR or knock related, etc..

A tune on a relatively stock car won't make it into some super car, but there *should* be a measurable performance increase - how much depends on the tune as well as the car, the weather conditions, etc.. Even on the stock turbos, a bump from 17 to 19psi is not a small amount of power, assuming proper fueling and timing are there.

Good luck with it, and hope you figure it out.