Increasing displacement of 3.2 liter motors and cold and weather prevent meeting up

TypeS

TypeS

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Now that I've grown accustomed to the awesome handling of my 2000 BoxsterS; and given the advent of winter here in NM, I'd like to get some feedback about increasing the displacement of my existing engine. I am a very experienced motor rebuilder, and have all winter to complete a rebuild on a motor that has given me no problems over the previous 4500 miles since my purchase. However, I've not succeeded in finding a diagram of the engine, and my experience with Porsches goes back to pre water cooled days, and did not include anything more than a few clutch installations and tune ups (other than 914 4 cylinders - glorified VWs).

My reasons for wanting to increase displacement are simple - more low end torque, and increased power when coming out of turns. Do any of you have any experience with increasing the displacement by swapping out pistons and cylinders? What are the horsepower/torque gains versus any drawbacks. The motor in question based on no discernable degradation of the motor oil would seem to be in perfect shape, and given that it's due for it's 60,000 mile service; I thought I'd weigh performing that maintenace versus upgrading the motor through a rebuild. Unfortunately I've not come across any reliable source of information on this.

Any feedback would be welcome. On another note the winter storm and a nagging cold prevented my driving out for tomorrow's rally, but this summer I'll definitely head out to the coast for a get together.
 
I've seen 1 bored out Boxster. It was supercharged as well.

Sorry that's all I know,but it let's you know it can be done.

*Just curious,does increasing displacement shorten the lifespan of the engine?
 
just find a 3.4L out of a 996 and plug it in....I know it might not be as much fun as building a motor, but it sure would be quicker and a whole lot more straight forward....never easy when you are trying to blaze a new trail:eek:
And watch what you say about 914s ("glorified VWs" as you term them). I would be happy to spank your Boxster ("glorified Audi";)) at any AX.
 
No offense 914 are awesome

Sorry if I offended about the 914 quip. I merely alluded to the motor and vehicle being made by VW as opposed to the 914-6 being made by Porsche - and the far less complex reality of working on the 4 cylinder version (ie: having to remove the exhaust system on the 6 to adjust the valves vs. simply popping off two spring clips). I love both cars, and especially enjoyed the immediacy of the the 4 banger, which matched the 6 in everything but acceleration.

To answer the question about greater bore equating to less fuel economy - if both vehicles are driven at the same speeds the economy would be nearly the same. Running the larger displacement motor faster would mean it would use more fuel to push the vehicle to higher speeds in the same amount of time; however, at highway cruise larger displacement translates to fewer revs per mph with the result that slightly better mileage is possible. My 986 gets on average about 25 mpg if I limit my race car driving to the twisties that naturally occur in the hill country near my home. If I run the 1.5 mile stretch of high speed hilly corners in front of my house 5 times within a single fill up at something like 95mph average speed; my mileage drops to 22 mpg.

The car is awesome, and it's taken me a month and a half to get used to cornering above 100 mph, so now I'm wanting more. Given my experience with building motors, I'd prefer to do it myself, and also save the money - imagining the parts would probably be less than 2500.00 while used 996 motors seem to be several times more expensive.

In any event, I'm still looking for a good cross section diagram of the motor, so if anyone can point me to a web page, I'd be greatly appreciative.

Jack
 
There is not a huge amount of information available. The best is to get yourself a copy of "PET" which is the Porsche parts catalog which has decent explosions of everything in the car including the engine. Google for it, and if you can't find it, PM me. You can also get it on CD from your dealer which covers all models.

I have only run across 2 places that bore-out M96 engines and should be good resources for your research. They are:
http://www.motormeister.com/suz/911_engines/911_engines_5.htm and
http://www.autofarm.co.uk/engines/water_cooled/capacity
AutoFarm has some very useful information about addressing the weaknesses of the M96 engine such as retrofitting the intermediate shaft. From what I've been reading, due to the cylinder bore spacing, 4.0L is approaching the practical limit.

I would love for someone to set up shop and start being able to do these motors. As it is, if you go with any bigger 911 motors, there are all sorts of miscellaneous "conversion costs" and gotchas such as DME dependencies with instrument clusters, HVAC, and more. Good luck, and keep us posted. BTW, mine is a Y2K S as well. Glad you are enjoying it!
 
TypeS said:
Sorry if I offended about the 914 quip. I merely alluded to the motor and vehicle being made by VW as opposed to the 914-6 being made by Porsche - and the far less complex reality of working on the 4 cylinder version (ie: having to remove the exhaust system on the 6 to adjust the valves vs. simply popping off two spring clips). I love both cars, and especially enjoyed the immediacy of the the 4 banger, which matched the 6 in everything but acceleration.

To answer the question about greater bore equating to less fuel economy - if both vehicles are driven at the same speeds the economy would be nearly the same. Running the larger displacement motor faster would mean it would use more fuel to push the vehicle to higher speeds in the same amount of time; however, at highway cruise larger displacement translates to fewer revs per mph with the result that slightly better mileage is possible. My 986 gets on average about 25 mpg if I limit my race car driving to the twisties that naturally occur in the hill country near my home. If I run the 1.5 mile stretch of high speed hilly corners in front of my house 5 times within a single fill up at something like 95mph average speed; my mileage drops to 22 mpg.

The car is awesome, and it's taken me a month and a half to get used to cornering above 100 mph, so now I'm wanting more. Given my experience with building motors, I'd prefer to do it myself, and also save the money - imagining the parts would probably be less than 2500.00 while used 996 motors seem to be several times more expensive.

In any event, I'm still looking for a good cross section diagram of the motor, so if anyone can point me to a web page, I'd be greatly appreciative.

Jack
Click to expand...
actually all the chassis for 914s were all made by the same manufacturer for Porsche.
Only differences were the motors...and some of the running gear, like small differences in spring rates, 5 lug vs 4 lug wheels, and some very slight differences in the interior, steering column and ignition switch placement. 914-6s had a lot of VW content as well when it came to small parts.
The 2.0L 4 cylinder Type4 motor in a 914 is totally different than VW bus engines etc. lots of parts interchange but cam, ECU, injectors, plenums, intake runners and most importantly the heads are totally different...:eek:
 

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Thanks for the info!

Thanks for the information and web pages. I finally got a sense of the possible based on looking at http://www.autofarm.co.uk/engines/water_cooled/capacity. I really appreciate both of your responses to this thread. I think my next step is to check in with my local machine shop. They've bored several motors for me in the past, and although I doubt they do this on Porsches, they should be able to refer me to someone stateside who does. Then......
 
I would be vary concerned about Motormiester.
they have a very bad reputation with rebuilding 911 motors...
run very away very fast from them.:(

there has been very little done with boring out Boxster motors since the swap to a larger 911 motor is relatively straight forward.
when someone wants more power they find a shop that swaps in a bigger factory motor.
 
Thanks for the tip

I had emailed Motormeister 5 weeks ago, and as no one ever got back to me, i'd already decided against using them. Now that I've finally seen a picture of the case halves of the 3.2 liter motor, I'm confident my mechanic friends can lead me to a reliable machine shop which does this type of work; or if indeed it's inadvisable to verify this. I used to wrench for one of the top Porsche shops in the East in the seventies, and several of the mechanics there have gone to professional race teams, so i'm confident their advice will be sound.

So far it appears that the 3.2 and 3.4 L's have virtually identical castings except for the cylinder liners, so my next step is to verify if the 3.4 and/or 3.6 liners have the same depth. But not to worry, I'm a great believer in "if it ain't broke don't fix it." So unless I can verify that this upgrade is both sound from a reliable source, and affordable I'll leave well enough alone.

Thanks again for your input.

Jack
 
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