marinb

I've had my eye on getting some headers like Vektor or Kline. They both look really pretty, and having equal length runners and a nice merge collector ~seem~ like the right thing to do.

But if that was the case, why does Porsche keep using Log style headers on their turbo cars?

The upcoming 992 uses newly revised cast iron manifolds, but they are still just Logs (plus a bunch of heat shielding):
https://motoiq.com/la-auto-show-2018...-view-porsche/
https://motoiq.com/la-auto-show-2018...iew-porsche/2/

The 991.2 GT2RS, the king of modern turbo Porsches (where you'd think it was a priority, no expenses spared, to get ever ounce of power out of that engine), also just use a Log:
http://www.fi-exhaust.com/images/pro...-gt2-rs-04.jpg

So it gets me thinking, is Log really that bad if Porsche keeps using it? They've had many many opportunities iterate on the design (they've been making turbo 911's since the mid 70s), but are still using a Log header. Maybe the things that matter most are really just heat retention and shortest path to the turbos? (And not equal length runners and nice merges, that are so important for NA cars).

Psorcery

"To improve exhaust flow, the stamped-steel manifolds in the 991.2 have been replaced by cast-iron headers. These are said to weigh no more, but flow better, than their double-walled predecessors."

From Car and Driver


"It’s an improvement on the 991.2 design which had the flows crashing into each other, but there’s still a lot of room from improvement:

From your link which states it's a log manifold.

marinb

I took that as mostly opinion from motoiq, since they tend to like to mod cars, and not too long ago added Vektor headers to a 991.2 car (i.e. the link you provided).

marinb

There is data that shows gains with Vektor and Kline. But how do these gains look when everything is heat soaked from a day at the track? Are the gains still there, or are they minimal, or maybe even less?

spdracerut

GT2RS is still a street car built with street car compromises and to a price point. You have to look at true motorsports engines. Just a few examples below.

Toyota WRC engine:


Audi DTM engine:


Chevy Indycar engine:


Audi R10 Le Mans:


Honda F1

Psorcery

You can also look right at home at the 3.8 NA engines along with the GT3 variants.

marinb

Thanks! That's a good data point.

Clearly Porsche has the capability to do this, but choose not to on the GT2RS. 🤷*♂️

spdracerut

Well, every car has a hp target determined by the product planning team. With turbo cars, it's easy just to turn up the boost a little higher to make up for inefficiency in the hard parts.

stout

It's always a question of Weissach R&D might/know-how, design goals, development budget, per-piece costing, and testing budget. The first one is a biggie, and not to be ignored, imo. I'll never forget an aftermarket exhaust shop that ridiculed the design of the factory 986 2.5 headers, for their pathetic looking runners and odd, "wine-glass"-like ports at the cylinder heads. Of course, the 986 2.5 was done on an extreme budget. They were working on beautiful—and I do mean beautiful—stainless steel equal-length headers with race-proven collectors, etc. But I never saw them again. A year or more later, a dyno operator was sharing funny stories and mentioned a set of beautiful stainless 986 headers that lost a ton of power compared to the stock headers on his dyno—at which point the shop that made the headers collected its stuff and left quietly and quickly. The timing was right.

Is it possible to beat Porsche at its own game? Everything on the car is a set of compromises, and a $12,000 crankshaft, $10,000 exhaust system, or $15,000 set of forged allow wheels may offer a more appealing set of compromises for some of us. I've modified some of the cars I've owned, finding good results in some cases (mostly suspension). With that said, instances of the aftermarket beating Porsche are, in my experience, few and far between in the real world. Especially once you add legality and longevity into the equation. What was that old saying? "Years ahead in engineering, miles ahead on the road." Someone mentioned heat sink; that's down the right path in terms of thinking. Perhaps headers are better, but those logs may have some advantages of their own...

VektorPerformance

If you want to cut to the chase, I recommend reaching out to some of our customers and ask their feedback. Some have posted and done install/reviews here in RL.

I can only speak to our product, but if you install it and don't detect am obvious noticeable difference in sound and performance, then we haven't done our job. The design intents of OEM and strictly performance optimized design are just different in some instances, and this is one. Some factory manifold from Porsche are VERY well designed and thought out, but the 991.2 is not one of them. Without sitting down with the engineers responsible for the OEM design one can only speculate the litany of reasons for using a log style design.