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There seem to be some misconceptions regarding the GT3's engine, and exactly how similar to the regular Carrera, Cayman and Boxster motors it is. Some have repeated a quote suggesting just four parts of the regular 9A1 are retained. In fact they are far more similar, but there are a number of key difference that set the GT3's engine apart.
Below is an image showing the modular 9A1 family. It was designed to be flexible, accommodating displacements between 2.7L and at least 3.8L and power outputs between 250 and at least 560 hp in turbo form. This is generally accomplished by changing the components that most effect airflow and displacement, highlighted below, while leaving the other parts constant.
In the GT3's case, however, these changes were taken one step further, as will be clear in the following images. I put these together from the PET, Carrera S left, GT3 right. I've highlighted with red dots the parts that are identical- in some areas of the engine you can see that majority of parts are retained. Three areas were heavily revised, however.
First, major internal components were replaced to accommodate higher revs.
Second, the head and intake were completely revised to allow for higher flow.
Finally the complete oiling system and some of the cooling system was revised for increased durability- they don't even look similar.
Outside of these areas as few parts were changed as possible. Some of the shared components surprised: piston rings, flywheel, generator, most pulleys, most ancillaries, etc are shared with the Carrera S or even the base Boxster. The important parts, however, like the heads and oiling system, have little in common with other 9A1s.
It will be interesting to examine these areas on the upcoming GT3RS and GT4 to see what parts are shared with this architecture. Rumor has it that the GT3RS will begin with a different architecture that is not 9A1. If true many of these parts might look quite different. However Porsche obviously went to great lengths to develop this oiling system and head, and one would expect at least an evolution of it to re-appear.
The other hand the head and internals don't appear needed for the GT4 power levels, though I'd argue the true dry sump probably is at cornering Gs we should expect.
Thank you, Pete. That took a lot of work to put together.
Clearly AP was exaggerating when he said that the two engines only shared 4 parts. Maybe he doesn't consider ancillaries, pulleys and the like as part of the actual engine. Regardless, his assertion does come across as an overstatement, although it's reassuring to see that almost all major components are different.
Thank you, Pete. That took a lot of work to put together.
Clearly AP was exaggerating when he said that the two engines only shared 4 parts.
I took some time, but it's useful I think for community education. And now you can see why I laughed! Wasn't laughing at you, certainly.
It is interesting to see the differences, and it must be difficult to communicate in words all the work that was done. Much of the important stuff is different... but how different is different?
My interest in posting both this stuff and the suspension differences for the GT3 I illustrated earlier is largely focused on the GT4, even if I wasn't in the market. We know the effort Porsche has expended on their GT cars in the past. We also know how little effort was expended outside the GT group on a few more cynical efforts (Cayman R).
If it wasn't for the GT cars I'd have little interest in modern Porsches. Thus I admit that I have an agenda: I hope we all keep the GT guys honest, because if they start making "Cayman Rs" I lose interest. I suspect I'm not the only one. Thus when the GT4 comes out, step one will be to look at the suspension parts, step two will be to look at the oiling system. They say it's a real GT car. I hope so...
I appreciate that a lot of work went in to this analysis; thank you! In the end, though, isn't it the driving experience that separates the GT3 from the Carrera (and nearly all other cars)? Do you really care how Porsche did it, but only that they surely did do it, and very well?
01-19-2015, 06:37 PM
991 GT3 vs Carrera S Engines- differences
Thank you.
Regardless, his assertion does come across as an overstatement, although it's reassuring to see that almost all major components are different.
