performance differences 2.4S stock engine vs 2.4S w. 2.2S pistons vs. 2.7RS

[swisscheese]

Is there anyone able to tell the performance differences between a 2.4S stock (fresh) engine vs a 2.4S engine with high-compression 2.2S pistons vs. a stock (fresh) 2.7RS engine? The high-compression type supposedly would add a better top-end performance and the 2.7RS a better torque performance vs. the stock 2.4S ?

Any measured hp / dynoed output ? Driving experiences? Any info welcome!

I have no plans in club racing, etc. just sporty road use.

[911MRP]

There is much more than 0-60 mph of course but previously posted this set of period datapoints which shows the stock motor 2.7 73 Carrera RS was strong performer on this benchmark for its time even vs more expensive Ferrari Daytona and the later 911 Turbo. Also gives figures for other 911 models. Most from same source.

http://www.early911sregistry.org/for...ration+figures

More generally below are impressions from one of the first road-test of a first 500 series gives Jenks impressions in comparison to other Porsches he'd driven back the day. The car wasn't even run in by time of this test in first week of calendar 73



These road-test views and figures are over four or five decades old of course but I have had many interesting cars and access to numerous others when working in automotive engineering -- some faster but only keeper is the 2.7 Carrera RS which I find is a classic that suits me. At one time it was used pretty much used as my everyday car including regular grocery trips to the supermarket and for the daily school run around suburban London as well as for hobby on classic events and track days. I always found the stock original 2.7 MFI spec reliable and worked well in that range of uses.

Last month a friend who has only recently bought two 73 Carrera RS told me over a beer that he is using them much on the wonderful north Yorkshire roads -- far more than his various other 911 models in his collection.

Had access to most 911 variants over the years courtesy of a friend's Porsche specialty business and enjoyed most but I'm biased. Depends what characteristics you like of course and what you intend to do with it.

Hope this helps

[swisscheese]

yes, thanks. Nice info on stock 2.4S vs. the 2.7RS. Of particular interest would be the difference between the 2.4S high-compression (2.2S pistons) vs the 2.7RS.
Car is to be used for sporty road-use only. No track / racing!

[gruen911]

I have driven both the 2.4S with 2.2 Higher compression P&C's, and a 2.7RS. The difference is low end torque from the extra displacement of the 2.7 engine. It's very noticeable from a standing start, and only slightly noticeable above 5k rev's. Remember, these cars use the same cams, same induction and same everything else. So the high rev'ing character is in both engines. From a seat of the pants point of view, I must say that I like the feel of the higher compression 2.4 more. Higher compression engines seem more jumpy... IMHO

yes, thanks. Nice info on stock 2.4S vs. the 2.7RS. Of particular interest would be the difference between the 2.4S high-compression (2.2S pistons) vs the 2.7RS.
Car is to be used for sporty road-use only. No track / racing!

[Chuck Miller]

Ok,

Driving a 2.4S w/2.2S pistons is like getting the best of both worlds... You're getting all the benefits of a 2.4S (longer legs and torque) with the snap of a 2.2S... It's a great combo...

With all things equal, what you're not getting is the almost 25% more torque of the 300 more cc's of the 2.7... which really makes a difference in all-round drivability...

You may never get to the difference between the h/c 2.4S and the stock RS for 'sporty road work'...
But if you do get there... the RS will be working a lot less...

Again, I would go a stock 2.4S rebuild... or the 2.2 h/c 2.4S... You'll be happy, and won't have to cut your case...

my .02

cm

[RSTarga]

for regular road use, additional torque is always a benefit

[a911s]

I have driven all three, plus the 2.2L S and 2.5L short stroke. The MFI in all three makes sure that the supercharged intake noise and fuel delivery rush is present in the power delivery for all.

The 2.4L S stock motor has more torque than a 2.2L S but without as much of the higher rpm rush. The 2.2 higher compression P&C's, when used in the 2.4S, provide more of the 2.2L S excitement, compared with the stock 2.4L S, but I would not call it night and day - more like a response improvement. The 2.5L short stroke motor speeds everything up even more. When you go to the 2.7RS motor the changes are more significant. There is considerably more torque down low, and on the good builds you still have 90% of the high rpm rush. It's probably the most drivable motor of this group, as you do not need to shift as much. It's hard for me to pick a favorite, but I would rank the stock 2.4S as the least exciting.

[62S-R-S]

A statement from an engineering guru (Bittenbinder) who once built and modified Porsche motors, and RS in particular, once remarked that..


"A properly tuned 2.7 will beat the pants off of anything, anywhere, anytime."

[swisscheese]

Thanks for the advice Chuck. The all-round drivability would fit my need best, but, as you stated, the case-cutting might be an issue; When I bought the car in 1996, I wanted to make it the proto 2.7 RS, without the thicker fenders. That's why I bought the 2.7RS P/C's already then. But, since then, the world has changed (...) and pre-74 911's have gotten a different, almost sacred, "protected" status. Hence my hesitation of doing non-reversible modifs (although 2.7RS is a Porsche-original..). But I've bought the car for me, not for business/selling/money. Might be an option to start with the 2.2S pistons and drive around and (if desired) make the step to the 2.7RS P/C's late...

Thanks Randy, nice to read from you! We drove around in your blue one, during the 2001 Las Vegas 10th year anniversary celebration . Wasn't that the 2.7RS?

[a911s]

Thanks Randy, nice to read from you! We drove around in your blue one, during the 2001 Las Vegas 10th year anniversary celebration . Wasn't that the 2.7RS?

Yes, one of the good ones...