Cyclman

So, my current plan of action is to save up for a GT4. I live and drive on track in Colorado, at 6000 feet altitude. If I got a 2.5 GTS turbo instead, added a tune, eventually coil overs, AP brakes, GT4 bumper, GT4 wing, would I be better off vs a GT4. I don’t care about resale, plan to drive this for 15 years at the track, I don’t care about sound, have a Boxster 981 with a Soul exhaust, which I am keeping to enjoy mountain road top down cruising. I do want to stay street legal, not ready to trailer. I will add cage / belts, lcas, etc. to either for safety, durability. With a tune, and an appx. 15% power loss at 6k feet, theoretically the turbo should fly by a GT4. It might even keep up, at my altitude, with a DeMans engined car, or at least not be too far behind. Anything performance / track related I am missing, need to know? Are there significant performance issues I am missing? Other recommendations? Track days are just HPDEs, this is for fun only, no racing.

Cyclman

@mr.t0fu Your thoughts?

ldamelio

Racing and DE forum will get you the most answers on this query. Forced induction always has better performance than NA at altitude but the bigger question is - does it matter for HPDE?

For recreational DE the driver is a lot more important than the car. I see lots of relatively stock regular 987s, 981s and 718s driving by GT4s. For that matter, I've outdriven McLarens in my 718 CS but also have been outdriven by Miatas. It's the driver, not the car for most of us.

The GT4 is a helluva car but really only has an inherent couple of seconds advantage on a stock 2.5 S or GTS at most sea level tracks. From the factory, GT4 is 15 seconds faster than a stock 718 S on the Nurburgring which is 5 - 6x the length of most US tracks. Tires are probably half of this so figure 1 - 2 s on most 2 - 3 mile tracks on equal tires.

A tuned 2.5 GTS with coilovers and 200TW tires will certainly be a few seconds faster than a GT4 at altitude. Do those few seconds matter if you're not racing? Not IMO but you may feel differently.

Now that I'm done with the soapbox, some data:

You lose 3% hp for every 1000 feet elevation so you're at 340 hp in a 718 GT4 at 6k feet - more than a base 718, less than a 2.5 S or GTS. A GT4 is already at a low end torque disadvantage to a 2.5 S or GTS - both of these achieve max torque at < 2k rpm. So, at 6k feet, the tuned 2.5GTS (presumably well over 400 hp at this point with even more low end torque) should dance away from the GT4, especially exiting corners on coilovers and equivalent tires.

The other question to ask (and I don't have answers) is how much the bodywork and downforce matter at that altitude. The GT4 is not a super high downforce car. Other than the cosmetics, you may not gain anything in lap time from the wing and front bumper - and you can't do the diffuser in the rear because of the center exhaust on the T4.

Here's a good site talking about forced induction and altitude:

https://www.garrettmotion.com/news/n...%20sea%20level.

manifold danger

It feels like this is a no-brainer. If you're even considering a 2.5 GTS, it's the far better buy.

Why buy into the GT4, which is seen as this unicorn product that we'll never see the likes of again and the market reflects that- when you can get a car that's arguably just as capable and suits every bit of your use case for probably half the cost?

If you're not actively turned off by the fact it's a 4 cylinder, the 718 GTS 2.5 is probably the best performance car bang for the buck in today's market. Coming from someone who's had both a 2.5 and a 4.0 718 GTS.

OldJedi

OP, if you are considering a GT4 front bumper kit, I believe that @IL_Pete has a bumper for sale that was not on his car for very long. He also tracks a lot and might have some helpful information for you about coil overs. Good Luck with your decision.

Joe250

Subtract 3% of power for every 1,000 feet above sea level.

718 GT4
0ft elevation = 414hp
6,000ft elevation = 364hp

414hp is fun but so is 364. If you plan on tuning it, you'll likely get far more power our of the turbo engine. However, you might run into cooling issues during the hottest months. Read thru Suncoast's 2.5L Cayman build thread. They spent a lot of time dealing with their cooling issue.

ANGST

The 2.5 GTS motor does not apparently have the cooling issue that the 2.5S motor that Suncoast's car has . I have never has an issue with mine .

ldamelio

It does. Less common than with the S, but I have spoken at the track with a couple of 2.5 GTS owners who have had the problem and it's reported on forums. It's track, weather, driving style dependent and probably also year dependent (2018 cars). I'm glad yours is OK but that's an N of 1.

Edit for OP: the cooling issue is easily and definitively solved these days. If you buy a 2.5 S or GTS, I would pre-emptively fix - costs next to nothing and simple - see Suncoast thread (skip to to the end).

Cyclman

Wow, lots of great thinking, just what I was looking for. I’m a little surprised that there’s this much support for the GTS. If the aero is unnecessary, that would be a big savings. Looking forward to additional thoughtful comments, greatly appreciate everyone’s time for the comments thus far. I will be buying one of these two cars, as I want to have a hardtop in addition to my convertible, that I can put a cage and belts into safely. It is just what is going to be better for my specific situation. One other benefit is that I can start with a car, and the cages and belts, LCA’s, then upgrade brakes and suspension down the road, allowing the money to trickle rather than one big bite. This track habit is not cheap, every bit of stretching the cash out would be nice.

docwyte

The NA engined cars here take a huge hit in power. However, the FI cars get heat soaked, especially at altitude and with our high ambient temps. I’ve run my 996 Turbo at HPR for awhile now, reliability wise it’s been rock solid, no issues there. It does feel more powerful at the beginning of the track sessions vs the end though.

End of the day you should buy whichever car you desire the most. That’s all that really matters.

Airbag997

It's closer to 3% per 1k ft for a NA motor.

Joe250

Yes 3%. My apologies for the mistake.

LehmanZ06

Don’t be silly. If you want to Track GT4 !
The traction control is not fully able to be shut off in the GTS.

GT4 for the win obviously for track, suspension etc.

Do you want to drag race ? Then PDK GTS

TRACK = GT4
Done

Joe250

In the 718 GTS traction control, which Porsche calls PSM, can be set to the default fully active mode, a less restrictive Sport mode, and completely shut off. Some people have been unable to figure out the complicated process of holding a button down for 2 seconds. We refer to them as "journalists".

ldamelio

Not nearly that simple. A set of coilovers, toe links and control arms erases the suspension differences. OP is asking about altitude where there are advantages to forced induction. I love the GT4 but he asked a specific question. From the factory at sea level, no one questions that the GT4 is a better track car but that's not the topic of the thread.