Sort of a porsche turbo history question:

Ive always wondered why the 911 turbo was always made on a less advanced (or, older), motor than the non-turbo 911 of the same period, (e.g. why didnt porsche just turbo charge the motor in the current 911). It seems this is true upto the 993, as the 993tt motor is basically the same as a 993NA (except for single plug difference).

Given the turbo has been a porsche performance icon, i cant figure it out - was porsche just being cheap?

 

Not sure what you mean... the 993tt engine is quite something with an output of 400+ bhp yet docile as can be around town. Ceramic exhaust ports, sodium filled exhaust valves, small-ish twin turbos (was the 993tt the first volume production car with twin turbos?) to reduce lag, large metal substrate twin cats, computer controlled timing/fueling/boost, AWD to make the power "safe" for most users, low maintenance, durable (expect perhaps exhaust valve guides?); the list goes on and on.

Given that Porsche could produce 400+ bhp with single plugs there just wasn't need for twin plugs to extract more power. In its day the 993tt was a supercar and is no slouch 10+ years on. There also comes a point where a car becomes too powerful to be sold to the masses, whether for safety, fuel economy or political correctness reasons. And perhaps there's an element of not putting all the cards on the table in one go; raise the stakes as competitors come closer?

The 965 with its mechanical injection is perhaps a bit more low tech than one might have expected of Porsche in the 90's.

 

The thing is that the M64 engine build up to the 993N/A is bullet proof and NOT cheap.
The 996 and 997 N/A engines are cheap with no real dry sump.

Porsche experimented with turbo charging the 996 N/A engine and realized that it would not work.

That is the reason that Porsche uses the good old engine blocks for 996/997 turbo.

 

Dodge Stealth/Mitsubishi VR4 and I think the Mazda RX7 Turbo had twin blowers before Porsche.

 

No, i meant that for all models before the 993, the turbo motor was based on a less advanced motor than the na car. Examples are 964Turbo (3.3 motor vs. 3.6 in the na), 930 turbo motor of late 1980s (was not the same as a 3.2 carerra), 930 turbo of early 80/late 70 also was not the same as the comparable vintage carerra.

Im not sure if the 3.6 964 turbo was the same motor as a NA 964.
Yes, i know all about the 996/997 turbo motors are dry sump and the NA motors are not.

 

Do you just mean 'why are they built on a smaller capacity block'?

Its a good question why it took aftermarkets like Andial to do a 3.8l Turbo in the 993, and even today, the 997TT is 3.6 based when he C2S/C4S runs a 3.8... curious...

 

not just smaller block capacity, but also, from what i understand (im not as technical as many here), the engines where less advanced in general in many other ways.

 

... and don't forget Toyota Supras and the Porsche 959.

Not sure who the first was to use twin turbos, but Porsche was using them in 1977 to power the 935/77 race car

 

The standard 996/997 Carrera engines are nowhere near as strong as 3.6L engine used in the 996/997 Turbos and GT3's. They are completely different engines.

 

Do a search for the "Andial closing" thread from a few months ago and check out the pics I posted of a customer's #2 and 3 heads from a 3.8 and you will see . . .
sealing area between heads and cyls is already pretty damn thin on a stock 3.6, when you bore out the cyls to 104mm, the sealing area becomes razor thin. Porsche did not want to do this in a factory turbocharged car that needed to be able to last.

The watercooled 996/997 engines use a 1 piece casting for each bank of 3 cylinders vs individual cylinders, even on the split case Turbo/GT2/GT3 engines, so there is a better sealing area, plus of course it is watercooled and the water carries the heat away much more effectively than air cooling fins do.

It does seem strange that the Turbos always seemed a step behind the NA cars technologically, ie how the NA got EFI in '84 and the Turbo was CIS all the way through '94, 4 speed thru '88, etc. But the answer is, don't fix it if it ain't broke. CIS always worked very well on the 930s/965s (until you start heavily modifying em of course) and Turbos always ran milder cams and way lower compression (very CIS friendly!) than the NA cars so I guess there was no real point in spending all the time/money to convert the 930 engine to EFI at the time. My guess is they were waiting till the Bosch Motronic controls were sophisticated/fast enough to control boost effectively along w/ all the emissions stuff, and that came w/ the 993 generation.

---Chris A.

 

Chris,
A quick look at the commercial / development factors that Porsche were facing during the time slot you are describing will tell all !
The 964 Motronic system is certainly fast/powerful enough to run a turbo in
non OBDII mode but that effort would have diverted the efforts needed for the 993tt-OBDII !
Like all businesses there are sometimes compromises that have to be made
in the short term to maximise the future potential .

All the best

Geoff

 

My 1993 RX7 (built April '02) was a twin turbo. Difference is the Rex's turbos are progressive. First one small turbo spools, then later a door opens and the second small turbo adds it's efforts to a common plenum. It's a funky vacuum controlled setup, but the car has great torque down low, which is otherwise unheard of in a rotary. When the second turbo hits around 4-4.5k it goes ballistic. A lot of fine American youth have converted themselves into organ donors in those cars.

A couple folks have noted it above, but boosted motors don't need max displacement to make big power. Sealing area between the block and the head is often more important. The combination of low compression and high boost makes the most possible power.

 

When it absolutely has to work. You use what you KNOW works. The Turbos are halo cars and the last thing any manufacturer would want to see is a halo car with across the board engine problems.

Like the first LS6 Z06 motors needing a ring job before you even took it home. I know.

 

Good point Geoff! Porsche was certainly in dire straits financially in the late '80s/early '90s. Now they are making 100k cars a year. How times change.

---Chris A.

 

Chris,
I was just politely going around the reality that in the late 80s/90s Porsche were going bust . Just enough money to rewarm the 964 and call it a 993 !

You are right about the change . Now Porsche is the most profitable car company by turnover percentage ! Thats life and hiring the right people.

Geoff