john weires

I for one have no interest in a car from Porsche that uses a turbo 4 cylinder motor. I have driven the 718 and just can't take it seriously because of it's exhaust note. Perhaps this is my loss much like not dating the girl with the great personality because she is rather plain in the looks department. To 718 owners who are ok with the sound, their reward is clearly more punch than the 981 Boxster/Cayman NA motors had.

From what I can glean from everyone's comments, Porsche is left with limited choices if the Spyder and GT4 are to remain NA.

If the Spyder and GT4 models are to be offered as NA variants long term, perhaps Porsche can justify the cost of an all new engine design going forward.
Figuring out the feasibility of this is above my pay grade though although I tend to think this to be the least likely path for the next generation.

Ideally I would like to see a de-tuned 9000 rpm 4.0L GT3 engine with around 450 hsp, but too high of cost or performance too close for comfort with the GT3 makes this seems less likely.

Re-using a slightly higher horsepower version of the 3.8L from the 981 Spyder and GT4 would be only a small incremental improvement in power, unless they could use the Power Kit which was available as an option on 991.1 911's. As I recall it put out 430 hsp, a nice bump over the 385 hsp of the 981 models.

Does anybody here know if space or other issues would prevent the Power Kit idea on a 3.8L engine from being a possibility?

Petevb

Yes there are space issues- the taller intake manifold doesn't fit. In fact the standard Carrera intake manifold doesn't fit, which is why the GT4 got the Boxster's and lost 15 hp.

john weires

Bummer............

DrJay

Uhm, the power kit engine fits just fine in a GT4... Manifold and all.

I am seriously considering this: http://www.teambgb.com/category-s/132.htm

That and some shorter gearing and I think I will be in vehicular heaven.

Petevb

If you spend 6 hours of labor making irreversible modifications to either the manifolds or the chassis then sure it fits. Anything fits given enough time and effort. But from the factory no, see above.

DrJay

Seriously, call BGB up.

DrJay

Also, if these guys can do it, then Porsche could do it for the next GT4 pretty easily.

Petevb

Seriously, from the BGB website: "REQUIRES ADDITIONAL 6 HOUR LABOR FOR X51 MANIFOLD INSTALL IN 981 ENGINE BAY"
https://www.teambgb.com/Engine-Conversion-s/115.htm

Some of the kits also space the engine down, cutting ground clearance (which is a compromise Porsche wouldn't make). There are plenty of DIYs on planet-9 and others. Sure they could make it fit, but repeating what I said above: the current parts do not.

A friend of mine did a DIY install 3.8 into 987 and went through the various options. It's not a huge deal, but as build the parts are not designed to work together (perhaps intentionally?).

DrJay

SO you agree it fits just fine then?

Petevb

Asked and answered:
https://rennlist.com/forums/987-981-...l#post14217973

DrJay

Their page here says it is fully reversible.

http://www.teambgb.com/category-s/132.htm

I am sure BGB knows what they are doing considering their racing record with Porsches in Endurance racing.

Petevb

Spacers and/ or irreversible manifold modifications. BGB does know what they're doing. John's around here someplace, he can come over and straighten us out.

This isn't about what Porsche could build. Any power figure up past 500 hp and Porsche will nail it no problem. But Porsche has designs, tooling and certifications for a specific set of parts that constitute the X51 package. Those parts do not fit without modification, and Porsche would need to change those parts.

spyderphile

So, assuming NA for next gen GT4 and Spyder, what are the engine options, Pete? A detuned 4.0 at 8K? How expensive would that get? Knowing what you know, would Porsche gift us such a treat?

zorgg

I might be wrong, but to me the only chance to see the 4.0 engine in a GT4 would be to have it in a very limited - and expensive ! - RS version.

For the 'normal' GT4 and Spyder, it would be impossible for Porsche, from a marketing point of view, to offer models that are as performant as the 991.2 GTS, in addition with a 4.0 NA engine, at a price that will be, say, 30,000 $ lower... (when looking at the pricing of the previous GT4 & Spyder versions, plus the current pricing of the 718 model range, it'll be difficult for Porsche to sell these 2 models at a -base- price higher than 100,000 $).
If Porsche stays with the 'old' 3.8 NA engine, then it's different... but, as I said previously, I don't know if this is possible from an industrial point of view (no 3.8 in the current 991 range, emission issues...).

Petevb

I have no inside info or good answers, but some conjecture and thinking out loud:

The obvious move would be a revised 9A1 3.8 with a bespoke intake designed to limit torque while making ~420 hp. Mated to a manual that would keep the car slower than a Carrera S straight line (and therefore cheaper), keep diehards happy, maintain a GT identity and keep proper separation from both the GT3 above and the Cayman GTS below.

There are reasons to think we might see more than this. First, the next GT4 and Spyder are likely to be even more special (and successful) with the switch to forced induction across the lineup. This suggests Porsche can plan for 5k+ cars, which is enough to justify a unique engine version (build numbers in the X51 range). Unfortunately those numbers will also put pressure on corporate fuel economy averages, and that in turn will argue for a new engine derivative.

Both the 9A2 and new GT3 engine have paid great attention to friction reduction through variable rate oil pumps, etc. This naturally improves fuel economy, making it awfully tempting to refresh with these new technologies. The 9A2 base would be cheaper parts, the GT3 would be better- unfortunately probably too good. On the other hand the engine is modular, spreading development costs across multiple platforms and giving the GT4 clubsport a race ready oiling system is attractive...

If GT and normally aspirated volumes are to remain small a smaller displacement GT3 derived mill gets more likely because there would be fewer bespoke components, and development and tooling costs would dominate. I'd probably use the 97mm bore of the previous 3.4 liter along with a modified head, bottom end, etc of the GT3. High revs, comfortable up to 425 hp, not a ton of torque so no need for the overly tall gearing to keep it slower than the Carrera down low. Most of the tooling and parts already exist at least in casting blank form, and costs could be kept in check by limiting revs to <8500. Detuning a 4.0 without decreasing displacement probably isn't an option- too torquey and contrived.

If GT cars are allowed to ride the wave of their sales success and increase in volume then the development of a normally aspirated derivative of the 9A2 would be justified. As with all 9Ax these are modular in displacement up to 4.0L, but there's little reason not to go with 3.8 again at that point.

That last option seems to make the most sense, but I'm curious how much resource AP will be given- they previously could only develop one engine at a time. Now however they not only have a second successful model to develop, they also can't use as many hand me downs from Weissach. Perhaps time to expand the group further?