vader1

Don't be too sure about that. The 911 Turbo S makes peak torque (487 ft-lb) at 1950 rpms. The newer turbo systems have done an amazing job at getting rid of lag.
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You are mis-equating lag with power delivery. Lag is the time it takes the turbo to spool when you put your foot down, it has nothing to do with peak torque.
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My limited experience with 4cyl turboed cars that have "right now" kind of power delivery are smaller turbos that are great around town and at normal freeway speeds but run out of breath at the top end compared to the NA engines they replace. You are thinking "Wow, this thing really moves" the first few times you drive it, but when you really spend some time in it you notice a couple shortcomings on the rare occassions when you really want some speed on the freeway to make a stupid move to get around some jackhole. But at speeds under 50 mph, the 4 cylinder in my Bimmer 328 feels pretty similar to the 6. Audi's and VW's small displacement turbos are like this too.

If I had to put money on Porsches plans, I would say they introduce the 4cyl during a mid-cycle refresh on the base car with similar power to the current base six but with more torque. They unlock a small increment of power on the S and GTS but keep the same flat six.

They won't go full turbo four for some time on the Cayman/Boxster. I would also venture a guess that the next 911 models that eventually go turbo get a much bigger HP increase to put some more performance space between the top of the line and the entry level. Its Porsche after all, and they love money like Scrooge McDuck.

JonBoy

Remember, they keep costs low by utilizing the same engine architecture across their model ranges. Thus, if they implement the 4-cylinder turbo, they possibly raise costs on their 6-cylinder engine (lower volume = higher cost). Thus, they can't get too crazy with the 4-cylinder implementation or they'll impact their margins. That means they'll have to raise prices or else suffer the hit internally.

Alternatively, it's very possible that they hold sell prices stable across the board and somehow the 4-cylinder costs less than the 6-cylinder (less machining, smaller block, simpler assembly in general, etc, etc) and thus, those lower costs offset the slightly higher costs due to the lower production volume of the 6-cylinder.

vader1

Well, BMW uses sort of a "modular engine" design especially, if I understand correctly, their upcoming series of engines. The four is basically the six with two cylinder lopped off. They can use valves and pistons and connecting rods and all sort of stuff across several engines. Don't know if that saves engineering on cranks and blocks too. You end up with different turbos, and starters, and alternators based on the engine size, but lots of parts are duplicated.

If Porsche's next engines are a 3.8 liter six and a 2.53 liter four, it would tell me they are doing something similar. I don't know how much it saves you, but it has to be something.

waltk88

Didn't Walter Rohrl accidentally leak some info on the upcoming turbo 911 models? IIRC, he said 350hp for base Carrera and 430hp for Carrera S.

mosesbotbol

Hard to 2nd guess Porsche's motives seeing how successful they've been (outside of the IMS/RMS fiasco) the last 10-15 years.

WolfpackS2k

Honestly, I'm a bit disappointed to see Porsche downsizing the engine piston count instead of pursuing another avenue to the road of improved fuel efficiency. As much as I hate hybrids I think Porsche adapting a KERS type system to their cars would be a better, more driver-enthusiast themed upgrade. Then again maybe they looked at that configuration and couldn't keep the weight down.

As much as I hate the thought of 4 cylinder turbos in a Porsche I'd probably still prefer it over a straight 6 w/KERS but an extra 150-200lb weight penalty.

Marioshi

Yeah, especially when you consider GM's dedication to keeping the small block alive. IMO Porsche is taking the easy way out...

Do they get to average their fuel economy with VW for CAFE standards? I would presume they do...