RoadrunnerGTS

Here's a full aftermarket GT4 kit https://rexsupersport.com/carbon-par...t-pp-material/

OldJedi

Thanks, I found the GT4 body kits along with the GT4 rear spoiler there, but I was trying to determine if anyone on here had ordered from them in the past. I think they are in Malaysia. I wanted to see if anyone had worked with them in the past and could say if they were good or bad and the quality of their parts.

FazedChicken

I also want to make a GT4 touring out of my upcoming GTS 4.0. I like the cleaner more classy look.

Really wish someone made one of these unpainted so you're not paying extra $$$ for no reason. I want it to look as OEM as possible.

Has anyone tried buying all the underbody GT4 plastic pieces and putting them on a GTS? I want the stealth look so I was considering doing all underbody stuff only (including rear diffuser).

IL_Pete

Yes, I have thought of that. I put the TWL Carbon Ducktail Spoiler on the the Albert Blue Cayman GTS 4.0, and that was fine, I experienced that up to speeds of 130 mph+, and didn't notice any change in stability. I also did the Spyder Spoiler on my Boxster 25. I did 49 Track Sessions with that last year and routinely was at speeds of 125 mph+ in the track sessions. I didn't notice any change in stability there either. See here, this pic is the Boxster 25 with the Spyder Wing, raised at speed. Speed on this straight at this point is 120-125 mph, coming into a kink over a curb that is pretty hairy. I didn't take that turn and curb nearly as quickly in the Boxster 25 as I did later in the GT4 and more so now with the Cayman R Race Car, but that has more to do with the suspension, alignment and tires. In this pic I am pretty sure I am into braking coming into the kink/turn.



I was quite pleasantly surprised how much the Spyder Spoiler on the Boxster 25 added to the aggressive of the look of the Boxster 25.




I don't think we are talking about high levels of downforce for the Boxster GTS 4.0, Cayman GTS 4.0, or even the Spyder. The Aero is there to make sure the car doesn't have lift at high speed, at least keeping in neutral.

That said, I think for my "Project GT4 Touring" I am planning to do later this year, as I mentioned I probably will do a Ducktail Spoiler of some sort, paired with a GT4 front fascia of some sort, and maybe also do the GT4/Spyder rear diffuser, and look at the underbody aero as well.

Theoretically that would have a very similar Aero balance to the Spyder, especially if I did the OEM GT4 Front Fascia but with the Spyder Front Lip.

colnagoG60

I think the company "Designed by Jacob" (<sp?) has done some significant aero testing/design. Maybe reach ot to them to see what works regarding aero balance?

RoadrunnerGTS

Agree it is unlikely to make any significant difference <130mph. BMW probably stated you needed both front & rear M-Performance to boost parts sales

Visually I have always found that you need to do both front and back to balance the look visually. For this reason I haven't added a larger spoiler.

One thing that I would like to change is the rear GTS diffuser. Looks cheap and not aggressive enough.

FazedChicken

Looks great! That's kind of what I want to do for my project GT4 touring.

For the pics you posted, what wheels are those and what size? They look great on the car!

IL_Pete

Thanks! I really like the look of them.

They are HRE P101 SC Wheels in Satin Black. Specs - Fronts: 19x9 ET50, Rears: 19 x 10.5 ET44, with 19” Michelin Pilot Sport 4S Tires, 255/35R19 Fronts, 285/35R19 Rears. With the GT4 I had 255 Fronts and 295 Rears, Cup 2's.

I use the Apex Racing Fitment guide for wheel and tire fitment, for 19" wheels that 255/285 is their recommendation ("staff pick") for both the GTS's and GT4/Spyder. I would have tried 265/305 on the GT4, but you need camber plates to do 365's on the front, and I didn't get around to doing that before the end of the track season.

Here is a closer up shot of them, from yesterday after getting cleaned up to go on the Spyder:



Here they are on the GT4:

Digger38

Hello Pete et al,

What are your thoughts about installing the Frog Venom rear spoiler on the CGTS 4.0 without doing anything to the front splitter? It sounds like you would not have a problem doing that and potentially being a little out of balance, correct?

I assume the Frog Venom rear spoiler is similar to the Spyder's rear spoiler. Does the Spyder have a significantly upgraded front splitter/spoiler as compared to the CGTS4.0?

Thanks.

Digger38

See that Spyder front bumper is very similar to GT4 (with slight differences). I guess on paper that front end balances better with the rear spoiler on the Spyder. I would say what I am wanting to do with the FV rear spoiler is very similar to what you did with the Boxter 25. Thanks.

Le Petit Garage

I wouldn’t worry about an imbalance as such, you’re going to only notice it on Track (if at all) and at that point could reset the imbalance with some more front aero / suspension tweaks.

Digger38

Thank You!

OldJedi

I am not sure that the aero works at speeds under 80 mph and most likely does not come into effect until you are tracking the car. I have had it up over 100 a couple of times and have not noticed anything, good (downforce) or bad (upset handling). I am going to Sebring this weekend and will see if I can get some speed on track and see how she handles.

Digger38

Your Beauty has a GT4 front also! This should most definitely provide some balance. I think most are saying, even without anything added to the front, adding the enhanced rear spoiler like you have done probably won't make any difference until you are really getting to some track speeds (if even then). Your thoughts on this? Thanks.

OldJedi

My short answer is NO! Below 80 MPH I don’t believe that you are going to see any difference, good or bad. But … I’m also NOT an Aeronautical Engineer!! Above 160 MPH I do believe that you might feel a difference but I don’t believe that it would be so severe as to throw you off track. I believe that a dedicated track car can certainly benefit from more down force but even race cars that lose splitters and wings while racing don’t go flying off of the track, for the most part. The Cayman GTS and Boxster GTS have essentially the same rear wing however the Cayman has a small front splitter and the Boxster does not very much of a splitter at all. Yet they both have the same top speed. 99% of my driving is on the street where bigger splitters and spoilers are really not going to make much of a driving difference.