Hello

I just received a GT4 RS , I m used to the 991.2 GT3 RS with manthey racing agressive track alignment and track modifications and usually I like track specific competition or stiff suspension but as I feel that the GT4 RS is a little too stiff and bouncy on the street as many report

I m looking to some reviews of the latest DSC module specific to the GT4 RS on street and track but also on how it compares with aftermarket coilovers

Of course the Manthey KW coilovers are really interesting but they are actually based on KW competition model so they are really expensive and not sure that they will be more compliant out of the box with their recommended spring rates and I did not read any user review

MCS 2WR could be interesting , not sure if they are a little cheaper when purchased from MCS and if the Dundon version have any specific settings

Then there are the KW V4 but also no reviews of them on a GT4 RS

I would really like the OHLINS TTX or other but I think that with most of the other brands you can t fit the OEM lift


Also on some older 991 topic some customer had some kind of electric noise interference when fitting the DSC module is that something solved actually ?

Thanks

 

Welcome to the discussion, there are a number of existing threads discussing these options already

GT4 RS track setup
GT4 RS driving impressions.

The TLDR is that… moving to a proper motorsport coilover offers the best solution for a track car.
I’m quoting rates in N/mm
OEM spring rates are 100F/140R

Manthey KW (4-way) is the most expensive but it is now a Porsche part so you keep warranty. FAL Support.
-Rate 120F/140R

MCS/Dundon (2-way and 3-way options) popular on RL, more cost effective than the Manthey option. FAL Support.
-Custom rates not yet disclosed.

KW V4 Based upon Competition (3-way) offered by SilverRocket and SSR in various guises is essentially the GT4RS CS system. FAL support.
-Silver rocket rate 100F/120R and they have another option.
-SSR custom rate - not yet disclosed.

Ohlins TTX - does not support FAL.
-Custom rates not yet disclosed.

Some have started to experiment with DSC and also changing just front spring rate to bring the F/R bias closer together for a more connected feel. Early stages.

 

TDT

Thanks a lot for your detailed reply

Of course I read most of the other discussions but I wanted to get some replies specific to the GT4 RS and eventually to compare the DSC with coilovers and your reply is already interesting

In Europe the KW 3 way is about half the price of the Manthey Racing KW 4 way but I m wondering if there is that much difference between the 2 systems
The Manthey Racing KW for older cars like the 991.1 GT3 or GT4 were based on the KW 3 way as well and on the latest cars as 991.2 GT3 RS and GT4 RS they based their coilovers on the KW V5 4 Way that are fore sure even better and quality and more adjustable but really expensive

On the street the main thing I do not like its the stiffness feel of the initial travel as if the low speed compression was too stiff together with a slightly too stiff spring rate and with a too soft rebound damping that keeps the car making short but constand up and down oscillations

Maybe as you say also the front to rear ratio makes this and it seems that most aftermarket coilovers tend to reduce the front to rear spring stiffness to 20Nm

 

Yes I’m quite familiar with the MR kits, I had it on my 718 GT4 full kit and also on my 981 GT4. As you say they have now moved to v5 (4-way) for the current GT cars 992 and GT4RS.

I’ve been out in GT4 RS with the new (4-way) kit on road and track. Its obviously very nice jump on control from the OEM setup. Much harder to say if you really get much more performance or feel than I had i my 718 GT4 with the 3-way kit. So it depends on how much warranty is worth to you as to what you do. MR or Silver Rocket / SSR offerings.

I had the same impressions of GT4RS OEM setup as you and I reported them way back… probably one of the first people to discuss some of what felt like lack of control on the 4RS, as I had the baseline of the MR kit on my 718 GT4, and I said at the time - the 1st thing I would do to a 4RS would probably be to get better chassis kit. Once you've had the best its; hard to go backwards.

October 2022:
https://rennlist.com/forums/718-gts-...l#post18409597

Not many people paid much attention to, or understood, what I was talking about at the time but since then everybody has become an expert on chassis setup and bump and rebound! -

I do think that some of the OEM behaviour can be managed with setup… ride height is crucial here - and then using the stiffer PASM mode works to bring back the control if your roads are decent enough.

My impressions of 4RS with MR damper on-road experience on UK b-roads back in April this year

I've personally narrowed down options to either the MR kit or the SSR kit for 4RS - but that's because I'm based in Europe. I've experimented with DSC on this platform before and I don't like the unnatural behaviour at the extremes of the G-tables and how it can be somewhat disconnected, with each of the corners sometimes doing its own thing. Not great. I won't waste time with it again.

I'm going to be visiting SSR in the near future to get some final detail on their kit before making final call.

 

Interesting review of the MR kit on UK b-roads that are usually described to be not the smoothest

I m also located in Europe and to put things in perspective in many other brand cars I used many different coilovers ( Proflex , Ohlins , Intrax , Nitron , Penske , AST , etc ) and I m used to European twisty mountain roads , Nurburgring , and a lot of track driving , etc...

That is to say that I m usually really enjoying racing suspensions , but at the same time I never felt it was necessary to upgrade to MR coilovers on my 991.2 GT3 RS as even if the controlled damping of some MR kit would be a noticeable upgrade I found them good enough for everything

The GT4 RS have part of the same character good things and things that could be improved as the 991.2 GT3 RS suspension but somehow there is a subtle but noticeable difference that makes me really want a superior hydraulic feel and damping on the street but without being any stiffer...

To complicate things I still have my GT3 RS that is already a little modified for track use with proper semi slick tyres , aggressive manthey spec geometry , PFC steel brake kit , etc etc and I m still not sure if I want to make all the usual track modifications to the GT4 RS or for the moment keep it

a little more standard and for street use while I still have the GT3 RS

The DSC unit is interesting for its price and easely fitted and could be somehow enough for the street but I appreciate your opinion because many times things that work well in a more normal use and closer to US speed limits can easely get out of their intended working range if for example used on an unlimited section of the autobahn or on a closed rally style backroad with a fast driver

I m sure that the MR 4 way kit is the best in everything and as you say it keeps the porsche warranty it can be used with the OEM lift and MR are the most qualified to have all their knowledge and also eventual Porsche official technical informations to offer the best settings
but is of course really expensive and I m also curious about the way that the MCS suspension works or if with the 3 way KW you could get close enough

Do you think that there is a lot of difference from a standard KW 3 way kit to the SSR version ?

 

Get a proper allignment sorted from a reputable suspension specialist as a first step.
Ride height is adjustable and affects the "bouncy" feel some complain of.

 

First off I think this thread has the makings for a great one. Back to the subject matter I found with mine having a good alignment which involves lowering the 4RS especially at the rear reduces the rear end bounce. I also feel it is further reduced by driving in PASM Sport mode which is the way I now drive mine even on bumpy roads..
However the above is only a cheap half way house fix and in no way approaches the superb control and damping finesse of a 4RS fitted with high end motorsport dampers such as MR 4 ways. You pays yer money and take yer choice.

 

I won't make my usually comments as they are well known.

However it STILLS baffles and disappoints me that Porsche's GT department with all their testing that they do, gave the GT4 & 4RS such poor damping on anything other than smooth surfaces. All they had to do was use a better quality damper with better internals and tune it better. It would not add that much more cost.

And those that defend Porsche ARE part of the problem !!!

OP, good luck in your endeavor. If you decide on MCS, MCS is a great product and with great support and while I only have the 2-ways, the 3-ways should be even more beneficial on the street.

 

Of course you are right that a good alignment especially if done towards each one intended use is the first step

I intentionally left the geometry and other suspension improvements and modifications out of my initial question to get some more specific replies about the different coilover kits and damping solutions but of course we can also discuss about that

It s possible that by changing a little the rake somhow reduces the resonation between the front and rear springs ( not sure if that make sense technically )

I agree that the damping could be better however I somehow understand why they made it this way if you take into account different things

If you look at the 991.1 GT3 RS vs 991.2 GT3 RS they decided to use on the 991.2 much stiffer springs even if the 991.1 was already well suspended

In that case the Porsche engineers wanted to make the car lap time faster and they succeded but still had to use the OEM dampers ( adjusted for the stiffer springs ) and choosed to make a compromise and focus on better lap times even if in other situations

the car would be more bouncy and less confortable

It s also logic that the OEM suspension is intended to work at it s best when in sport mode as it s the mode that is supposed to be used when on track

The normal softer mode then can only make the damping and especially the rebound softer but the mechanical spring rate it s still the same and fitting stiff springs with noth enough rebound will lead to the bouncy uncontrolled initial feel we know


Back to the GT4 RS I guess they wanted to use the same logic as they found out that stiffer springs together with other things will make the car faster in lap time and maybe they also tought that in a car meant to be used fast as the GT4 RS the stiffer front springs would reduce the chance of
bottoming out and put unwanted load on the strut tower ?

But as the Cayman base is different than the GT3 in many things because it s smaller size different motor position and different wheel sizes and width of the car it would make the relative lack of damping control of the oem shocks more noticeable

With motorsport high end suspension it s normal to expect a better and more refined damping control of course and other cars would not have used so stiff springs with oem dampers to start with maybe

It s possible that the DSC module makes an excellent work in smoothening the settings to a certain point but as TDT mentioned it s also possible that at a certain limit on certain surfaces then the OEM settings make more sense ( or not )

I never used a DSC so I can not really comment but as good as It can be it still have to deal with the oem spring rates and oem dampers it s adjustable and it s for sure an excellent product but not sure how it would be rated for example by Porsche factory drivers at full pace on the Nurburgring compared to the OEM settings

TDT I read on your other thread that you briefly used some KW clubsport on your GT4 and you posted a picture of them near to the MR inverted competition KW
at the time you felt a noticeable difference between those ?

 

I will add two thoughts at this point of the discussion.

1. Spring Rates The OEM springs at 100 and 140, which creates a 40 Nm spring gap between the front and rear, just don't feel quite right. The car does better when the gap is 30 or even 20 as Manthey did with their kit. I had the pleasure of driving my car back to back one hour apart with a 100/140 set up and then a 112/140 set up on consecutive sessions at my track. This was accomplished just by adding some Longacre 70 pound spring rubbers like they do in Nascar. Super easy to do and immensely educational. This was on 255/295 fading Cup 2s with understeer being the issue with badly worn fronts. The first turn out with the stiffer front springs and the car just turned in better and had less understeer. Like a second quicker a lap type amount less of understeer on these old tires on a hot afternoon! The whole car was better balanced and felt as one rather than a front end and rear end trying to work together. I left the spring rubbers in for my drive home and it was the most composed it had been to date, on you guessed it, the stiffer shock setting. No more pogoing of the front off of the stiffer rear and again the car felt as one. I did this because I am planning to add a significant amount of downforce in the near future so I split the difference on Manthey's upgrade of a 120 front and went with the 110 to complement the 140 rear. In hind sight, with all that has come out in 2024, I would have softened the rear to130 and left the front at 100 in order to get the 30 Nm split front to rear. For those who are going to be mostly street, I would seriously consider a 90/120 Nm set up. Ten less in front and twenty less in the rear. Then coilovers of your choice or the DSC Box.

2. DSC Box There is more in the DSC box than meets the eye. TPC puts in a standard upgraded program, (over the counter, OTC), but it is trying to be all things to all people just like OEM Porsche has to be. They have many tables that can do some really cool things, but after adding up all the various setting adjustments for all of the parameters, I think the system is too busy trying to be the perfect thing all the time. I had one on a previous Cayman S. After a few iterations, I simplified most of the settings. I adjusted the shocks to where I wanted them, then softened the core of the G table at 0 and .2 G boxes for going down the road straight more smoothly. That way when at the track the shocks stayed constant in their values during the turns except for allowing the inside wheels to get transiently softer when the opposite side was loaded up close to 1G. That way when you hit rumble strips, the car could absorb the bumps much more efficiently and not upset the attitude of the car. That part worked especially well. The newer boxes for ours cars also have differential setting for both compression and rebound. So we can all add more rebound to the front and especially the rear as needed, and maybe even soften the compression a bit too. I think we need to keep the settings relatively constant, improve the comp/reb ratios, and consider the over springs rates as clicks on our shocks like on the coilovers. I don't have the formula yet, but I can see this working much better than an OTS program, and getting much closer to the after market coilovers. Then you have two different settings that you conceived at the touch of a button. This I am sure would help remedy the comments of some that say the DSC box is a bit wishy washy. If the box is constantly changing it's mind on the settings, of course it would be hard get confidence in the suspension when at full tilt.

 

[QUOTE=Maxi_z;19613289]
With motorsport high end suspension it s normal to expect a better and more refined damping control of course and other cars would not have used so stiff springs with oem dampers to start with mayb

I never used a DSC so I can not really comment but as good as It can be it still have to deal with the oem spring rates and oem dampers it s adjustable and it s for sure an excellent product but not sure how it would be rated for example by Porsche factory drivers at full pace on the Nurburgring compared to the OEM settings

The GT4 RS does have Sachs Motorsports shocks. Maybe not calibrated to many of our likings, but definitely an upgrade from the GT4s equipment.

Bergmister when driving the GT3 RS increased the rebound settings in both the front and rear by more than just a few clicks. So more evidence that the management just likes things a certain way even if it is different than what it's own test driver prefers. Not criticizing Porsche here, just stating the facts. They, I am sure, have their reasons.

 

Deleted

 

[QUOTE=lovetoturn;19613488]Where did you get the info on the GT4 RS using Sachs dampers as opposed to the GT4’s Bilstein ones. Was under the assumption that both used Bilsteins ?
I also believe the crux of the problem with the rear bounce is the 40Nm variation between front and rear spring rates. Increasing the front springs by 10 to 20Nm for cars used mostly on track seems a simple cheap option.. Conversely lowering the rear rates by similar amounts seems to be a good idea for more street use.

 

What’s a good source for replacement rear springs for the gt4rs - like 120nm/mm of the correct dimensions?

 

I read somewhere (or possibly YouTube vid) that the 4RS has Sachs dampers as well. I'm happy with the OEM setup along with DSC after one trackday. Both tracks I frequent, Laguna & Sonoma, have recently been repaved so no issues for me.