Horsepower ? About 2.7 Engine

[Phares]

So, this may seem like a really basic question, but I hate making assumptions and I am still really new to the Porsche world, so here it goes.
The 911, 911S, and Carrerra from 74+ were all 2.7L engines, but produced different horsepower ratings.
My question is how? I.E. what was different between the engines?

Thanks.
Chris

[N882928]

Compression ratio and a hotter cam I think would be the big ones.

[Steve@Rennsport]

Originally Posted by Phares

So, this may seem like a really basic question, but I hate making assumptions and I am still really new to the Porsche world, so here it goes.
The 911, 911S, and Carrerra from 74+ were all 2.7L engines, but produced different horsepower ratings.
My question is how? I.E. what was different between the engines?

Thanks.
Chris

For US engines:

The 2.7 and 2.7S (and Carrera) differed several ways which included compression ratio, head port diameters, CIS airbox & runner diameters, and camshafts.

The Euro Carrera's had the same engine as the '73 RS; that nice 210HP, MFI-equipped version.

[Phares]

Thanks for the answers. I have some homework to do to understand some of the terminology but it seems to make sense. Thanks again. And here I go down the slippery slope...
C.

[Grady Clay]

Chris (Phares),
First, WELCOME to the Forum
You will find a lot of help here.


For the ’74 911 models, there were three USA models and several RoW (Rest of World) models. (Also '74 914 1.8 & 2.0.)
For USA all the models were imported by the Porsche+Audi (P+A) division of Volkswagen of America (VoA).
All these 911s were in coupe and Targa bodies (execpt coupe only RS & RSR):
911 – Least level of ‘standard’ trim but most everything optional. Lowest power 2.7 engine (type 911/92); 150 hp, 8.0:1 Compression Ratio (CR).
911S – ‘Middle’ level of ‘standard features. The highest hp USA legal engine (type 911/93); 175 hp, 8.5:1 CR.
911 Carrera – Highest level of ‘standard’ trim and equipment of the US-legal cars. Notable for the wider rear fenders and standard 7x15 Fuchs wheels in the rear. The 911 Carrera USA has the same engine as the 911S USA (type 911/93).

Both of these engines use Continuous Injection System (CIS), have relatively mild cams (the ‘S’ and Carrera having a bit more ‘aggressive’ cam) and relatively low CR (compared to other 911 engines).
They did not use catalytic converters – they still used the (excellent) exhaust from all prior 911s.

The 2.7 engines (particularly the 911/93 and later emission engines) were notable for running too hot if not equipped with a front oil cooler (a relatively rare option but easy to retrofit).
This caused a failure where the cylinder head studs would ‘pull’ the threads in the magnesium crankcase.
This caused compression leaks between the cylinder and head.
There have been good ‘fixes’ developed for this issue.
The (normal) 911 (911/92) was least susceptible to this problem.

The RoW cars were (are) commonly imported to the USA as “Grey Market” cars.
In theory all were “Federalized” to comply with safety and emissions regulations.

In addition to the 911 and 911S with similar equipment as the USA cars, the
RoW 911 Carrera had the 911/83 2.7 engine used in the ’73 911RS. This had Mechanical Fuel Injection (MFI), the ‘wild’ early “S” cams and produced 210 hp with a 7200 rpm redline.
RoW 911 Carrera RS 3.0 had a three-liter engine (type 911/77) using the same MFI as the 2.7.
This rare engine produced a whopping 203 ft-lbs torque and 230 hp with 9.8:1 CR.
also
RoW 911 Carrera RSR 3.0 race 911 (actually a Carrera RS 3.0 with M491 $6,000 option) with the racing (911/75) engine producing 330+ hp at 8000 rpm.


So….
As you can see, there is the range of engines spanning over a 2:1 range of power.
Your '74 911/92 may not compete with a RSR but it is a very pleasant, reliable and economical 911 engine.
If you don’t have the optional front oil cooler, the systems are available used from salvage 911SC (’78-’83) and Carrera (’84-’89).
There are also great aftermarket systems.
Another ‘engine longevity’ mod is to increase the engine fan ratio from 1.3:1 to 1.86:1.

Your 911/92 is not a good candidate to have its power increased.
It is simply not economical to change all the necessary pieces.


If you ‘feel-the-need-for-more-speed’, the prudent choice is to buy a 2nd engine. The stock 3.0 911SC (180-204 hp) and the 3.2 Carrera (~204-232 hp) are good choices.
Of course the opportunities building a high-performance (streetable) engine are endless.

Once you are practiced, it is reasonable to swap CIS engines during a Saturday morning and be driving again in the afternoon.
The '84-'89 Carrera Digital Motor Electronic (DME) injection is only a bit more of a challenge.

Aah … ‘The Slippery Slop’.
Search through the Forum and find other projects.
Inquire about the technology and the decisions made.

Expanding your Porsche ‘Technical Library’ will also help: My Books arrived


Best,
Grady

[AshEvan]

[Phares]

Wow, thanks Grady. That is a lot on information! I appreciate the "honest" truth about the potential of the 2.7. I actually want to leave it pretty standard. These cars are a dying breed and I feel slightly responsible to keep it alive the way it was built. But nothing says I can't touch the suspension, brakes, and an oil cooler is the next thing on the way.
Chris

[JeremyD]

in all honesty = I have surprised more than my share of SC's and carrera with the measly 2.7 "s" engine the car had in it when I first got it.

That coupled with the 7/31 transmission makes the car pretty quick - just runs out of steam around 110-120

[redstrosekNic]

Originally Posted by JeremyD

in all honesty = I have surprised more than my share of SC's and carrera with the measly 2.7 "s" engine the car had in it when I first got it.

That coupled with the 7/31 transmission makes the car pretty quick - just runs out of steam around 110-120

+1
I really enjoy my 2.7 S engine. I love the punch it has at about 4,500 in second gear cruising in traffic. My car does have fiberglass rear flares, front fenders, and bumpers, so I'm sure the lighter body has something to do with it... Any Porsche flat six tickles my fancy

[larrym]

I've never understood how that 2.7 RS could make 210 hp with only 8.5 CR p&c's

it goes against all the other advice on how to make HP

did it have different heads and maybe more CR?

.

[Flieger]

Displacement. The 911R made 210 hp out of a 2 liter. RSR 2.8 made like 100hp/liter I think. Later 3.3 RSR did at least.

[larrym]

i doubt that displacement is the answer

- a 2.7 with different cams & induction come nowhere near the claimed 210 HP

Originally Posted by Flieger

Displacement. The 911R made 210 hp out of a 2 liter. RSR 2.8 made like 100hp/liter I think. Later 3.3 RSR did at least.

[Jim Sims]

I was under the impression catalytic converters were not installed until the SC's in 1978. My '76 2.7 l 911S (California car) had thermal reactors - different technology (there's a sticker on the door frame noting non-catalyst) and was specified to use leaded fuel. Cheers, Jim

[peon77]

Originally Posted by Jim Sims

I was under the impression catalytic converters were not installed until the SC's in 1978. My '76 2.7 l 911S (California car) had thermal reactors - different technology (there's a sticker on the door frame noting non-catalyst) and was specified to use leaded fuel. Cheers, Jim

Thats correct the reactors were an alternative to catalytic converters. they were for the use of leaded gasoline.

[Eagledriver]

Originally Posted by larrym

i doubt that displacement is the answer

- a 2.7 with different cams & induction come nowhere near the claimed 210 HP

It's not hard to understand. The RS engine spins to 7200 RPM. The CIS car has 187 lb/ft of torque at 4000 RPM and 175 hp at 5800 RPM. The RS engine has 188 lb/ft of torque at 5100 RPM and 210 HP at 6300 RPM. Notice the torque is the same, it's the RPM that makes the power. If you go to an online compression vs HP calculator, you'll see that the effect of higher compression ratio is small.

-Andy

[Flieger]

I thought it was 5500 for peak torque. I don't have my books with me. Is it actually 5100? That seems kind of low.

I meant displacement compared to a 2.2S or 2.4S. 2.2S had higher compression. With 2.4S and 2.7RS and the lower octane of unleaded fuel Porsche decreased the compression ratio. The larger engine was for the racing class homologation and also helped to make up for the lost power.