GoKart Mozart

I had my (new to me) GT4 for a few weeks now and slowly but surely the mod bug will set in soon. Not that that the car needs a lot, but it is in my nature to always find things to improve and makes the whole thing more fun. This car serves mainly as "recreational vehicle" and for HPDE's, about every other month (or ~6/year). My plan was to go to the track the way it is at least for the first time, but I'm pretty sure I will want/need to do some things to get more negative camber soon there after. That seems to be the consensus from what I read, although I am not 100% sure which parts are a must to achieve it, or I should say, it seems there are a few ways to achieve it, but I have not found one clear winner, or the go to approach. For the record, I like to keep things simple and usually prefer the path of least resistant.

As far as the engine and power goes. It feels like there is a bit of a flat spot in the power band. I suppose some of it is because of the tall gearing and I would not mind addressing that. The problem in my view with changing the gearing is a) too pricey, and b) it either only addresses gears 3,4,5 (Sharkwerks) or that it lowers all gears i (final ratio change), but 6th is already pretty low IMO. To me the ideal solution would be to change the lower gears 1-4 only, but apparently it is too costly to do so.
With that mod kind of ruled out for now, I am eyeing a tune, with intake plenum, TB and high flow air filters. Wondering which one to get though? is there a clear winner in this department? Are there warranty concerns? Is it worth the $3-4k it costs? I know headers also help a lot, but I would not want to make the car so loud that it wouldn't pass sound at Laguna Seca anymore. Anyone here have some experience with tuned GT4 at Laguna Seca?

911therapy

Congrats on the GT4!

IMO, the intake plenum is a waste of money (and time). I'd suggest reaching out to Jamie at Dundon. He has tons of experience with the GT4 platform. If I recall correctly, his testing showed the plenum to provide little-to-no improvement in power.

I have done the following to my GT4 (and I am very pleased so far): Dundon headers (I doubt they would pass sound at Laguna, but I bet Jamie has a solution for you); Cobb/Dundon Tune; Lightweight wheel and clutch kit; swift springs, camber plates, 19 inch wheels. The only mod I am planning now are the intake runners. At that point, I will have probably squeezed all of the power out of the GT4 that I can.

I'll then start looking at cutting weight somehow. And maybe some suspension upgrades. I would like to shorten the final drive ratio, but I just dont want to have to drop the transmission and ship it off......

GoKart Mozart

Thanks for the input. I was thinking the plenum was worth more, good to know. I know the headers are probably key, but the Laguna Sound thing is a real issue. The car is probably close to the limit in stock form already.

Have you done the lightweight battery? That is a must I think. Easiest way to shed 25 lbs and usually the first thing I do on my track toys.

911therapy

Yeah, the leguna low decibel threshold would be tough to deal with......thankfully most of our tracks in the south have little to no sounds restrictions....

I havent gone the lithium battery route just yet....I want to find a way to some more weight out of the mid and rear of the car at the same time. I used the lithium batteries (Voltphreaks VP6) in my GT3's, but I was always taking weight out of the rear at the same time by removing the side mufflers........

Five12Free

GoKart Mozart

Luckily my home track is really Thunderhill, but I do like to go to Laguna Seca a couple of times a year and it would be a shame to ruin that experience with a car that is too loud.

Your right, ideally you want to take the weight off evenly, but from my experience it still more beneficial to remove the weight, even if it is a bit more off of one end. I just came from a e46 M3 where I had done a lot of weight reductions, and on that car most of them were in the rear of course. I never noticed an ill effects from it not being perfectly 50/50 anymore. In other words, weight savings>50/50 balance....within reason of course.

That sounds promising. Glad to hear that.

What is a lifetime muffler?

ajw45

FWIW, I ran DMS race headers and the DMS (quiet) lifetime muffler at Tremblant, PSE off, and just squeaked by sound. They are a 92db track and I hit a peak of 92.5db (once, on on day) so if Laguna is similar you can have both the power gains of race headers and still come in under the noise limit. All tracks measure a little differently but even if Laguna is another 1-2 db quieter than Tremblant, DMS makes a set of turndowns for their lifetime muffler which can be bolted on and off easily and should get you another couple db of sound reduction.

I would do headers, I would do exhaust, you lose weight and gain hp with both, I would skip the IPD.

Bill Lehman

The last thing a track day GT4 needs is more power. The first thing I added was a track alignment and a roll bar and harnesses. This was followed with track brake pads plus wheels and tires. All of this is well documented in this forum.

911therapy

I assumed, based on the OP's post, that he planned the basics (pads, fluid, track alignment) and he was simply asking about additional power after the basic track prep. I agree that roll bar and harnesses are extremely important for safety (I have the BBi half cage and schroth harnesses). But, not everyone that tracks occasionally wants to install half cage and harnesses....

Alan C.

No Hans no harness. And almost nobody worries about fire.

GoKart Mozart

That is solid info. Thanks. Yes, Laguna has both 92 and 90db days and the turndows (or turnaway from the sound booth do help, as many cars run them there). So that would be a good route for me to go then. I still wonder what the lifetime muffler is? Is that the name of it, Lifetime?

Yes, precisely. All that for mentioned stuff are a given, and where I will start of course. Also, I don't necessarily just want more power for the track, but because the middle of the power band feels like it has more potential and because no one ever said, I don't want a little more power.......OK, maybe the guy in the GT2 RS would.

The half cage would be a wise thing to do, especially on 2 seater where it really doesn't impact space all that much. It is not necessarily something I wanted to do for just a few track days per year, but probably will do. I'm just thinking ahead for what is possible as far as the power and tune is concerned.

ajw45

It's a heavy duty steel replacement GT3 center exhaust with a lifetime warranty!

https://www.dundonmotorsports.com/porsche/gt3-lifetime-center-muffler?carid=40

I haven't seen a lot of reports of 991 exhausts failing so not sure how much of a problem this is on a GT4 but the exhaust is built like a tank. Only down side is weight since it's a little heavier than the stock steel GT3 center..

GoKart Mozart

Thanks for the clarification. I just read the details in the link and it all makes sense now. In theory I don't want the car to be quieter than it is stock, but in conjunction with headers (to gain more power), and presumably makes the car louder, it would be a good way to get around it, although that adds a lot of cost to doing it, ~$4k for just the muffler, wow!

ajw45

Yeah.... so it might not be the most budget friendly way to go. With the Dundon race headers and stock exhaust (PSE off) I was a little louder, passed some days at Tremblant if the humidity and temps were just right, other days could hit 93.5db. A good alternative would be to keep the stock PSE and swap in an X-pipe so you can switch between regular normal tips and turn downs. Soul makes some turn downs with clamp on tips and I bet they could make a set of turndowns too....

http://soulpp.com/product/porsche-bo...ipe-with-tips/

iammacey

As others have said, adding the Dundon Headers makes a world of difference. Add Cobb with Dundon tune and it is brilliant. Definitely much louder above 4k RPMs, but absolutely epic note. And to me, it's way more awake in the mid range. If you get to Georgia, let me know. You can certainly check mine out.

And keep an eye on the marketplace. I purchased the headers from one member and the Cobb from another. Did the install myself. And Jamie, with Dundon, can sell you the two gaskets you need.