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Yes I have Fabspeed 200 cell Xpipe, BMC filter, resonator bypassed in stock airbox. Coupled with PSE it sounds mean above 4000. Beyond coilovers and camber plates the rest of my mods are mostly for weight reduction.
Very nice! Will think more after I rebuild the engine successfully.
Some of you may wonder why I chose to tackle this job as opposed to giving it to the machine shop. I have a few reasons but the major ones are:
- I wanted to go through it and see what is involved and how tricky it is.
- If you inspect the JE piston and the stock rods and hold them in your hands, you will realize there are not many places to trim weight without jeopardizing integrity.
So my goal was to juggle the parts and see without grinding, how close I can get. All the parts have natural weight variations (a fraction of a gram) due to manufacturing. Every single gram counts.
The whole process is VERY tricky because you need to be able to separate the rotational weight and the reciprocating weight. You need to be able to measure the little end or big end of the rod accurately that is repeatable also. Also when you add more weight to the big end, the little end will weigh less.
I use the following metrics to judge how balance everything is:
- Little end weight (part of the reciprocating weight)
- Big end weight (rotational weight)
- Total rod weight with bearing shells and ARP bolts installed
- Total piston weight with rings, pins, etc. installed
- Reciprocating weight = little end + total piston weight
- Piston + rod overall weight
So the goal is to match the pistons to different pins, rings, ARP bolts, bearing shells, circlips to minimize the variation of the above metrics between bores.
It involved heurestic and some Matlab code for fine tuning. At the end here's what I got and I'm pretty happy:
- Little end within 0.4g
- Big end within 0.3g
- Total rod within 0.6g
- Total piston (with rings, pins, etc installed) within 0.6g
- Reciprocating weight (LE + piston) within 0.4g
- Rod + piston within 0.2g
Clean rods with genuine bearings and ARP bolts installed for balancing.
I'm looking to buy a 911 and, taken roughly, it seems that there is a choice between the air-cooled and the water-cooled versions of the engine. From a sanity-check point of view, spending $15 or $20K on a water-cooled engine because they seem to have a high failure rate has the unfortunate potential of taking the fun out of owning a sports car. I find an inordinate number ads showing 911s with engine problems.
I'm now thinking that the air-cooled 911s might be a better choice. I love all 911s, but setting reserves for a potential repair cost equal to another car is something I'd rather avoid. The next step is to look at the earlier 911s and learn what heartaches exist there.
This thread has been an entirely entertaining, educational, helpful and getting all the "inside" information from Ahsai's posts, plus the fact he is undertaking this project and sharing every thing, until now - CARL. Please move your post and start your own thread so we can rail at your idiot comments there. Thanks.
I'm looking to buy a 911 and, taken roughly, it seems that there is a choice between the air-cooled and the water-cooled versions of the engine. From a sanity-check point of view, spending $15 or $20K on a water-cooled engine because they seem to have a high failure rate has the unfortunate potential of taking the fun out of owning a sports car. I find an inordinate number ads showing 911s with engine problems.
I'm now thinking that the air-cooled 911s might be a better choice. I love all 911s, but setting reserves for a potential repair cost equal to another car is something I'd rather avoid. The next step is to look at the earlier 911s and learn what heartaches exist there.
Sincerely,
Carl
via Dragon Dictate
Carl,
Purchase the style 911 you like, but the air cooled isn't going to save you a dime. Ten years ago you could buy a very very nice 1986 911 for the low $20k range. Today that same car is $40k minimum. The cost of the air cooled car will be $20K more at least, than a 996. I see air cooled 911s with well over 100k miles asking high 30's to low 40's. And they don't seem to indicate a recent engine rebuild, which, if you're looking at a car with 140k miles (pre 1990), it's going to need one so add another $8,000 to the price.
If you are a IMSB worrier, avoid it. Buy a turbo. I personally LOVE all the IMSB insanity, it allowed me to purchase a 2002 Porsche 911 at a VERY reasonable price.
I agree that it has been educational and Asahi's efforts are admirable. I am only observing, as someone new to the Porsche intricacies, that the costs are higher than I would have otherwise imagined. I still love the 911.
I'm not worried about costs, just surprised. Agreed, one will pay for the 911 in form or another. I didn't realize that Porsche engine overhauls costs as much as some small aircraft engines to rebuild. If the IMS is the only shortcoming to the engine and there's a fix for it, then a repurchase inspection seems prudent and then have it retrofitted straight away.
I'm looking to buy a 911 and, taken roughly, it seems that there is a choice between the air-cooled and the water-cooled versions of the engine. From a sanity-check point of view, spending $15 or $20K on a water-cooled engine because they seem to have a high failure rate has the unfortunate potential of taking the fun out of owning a sports car. I find an inordinate number ads showing 911s with engine problems.
I'm now thinking that the air-cooled 911s might be a better choice. I love all 911s, but setting reserves for a potential repair cost equal to another car is something I'd rather avoid. The next step is to look at the earlier 911s and learn what heartaches exist there.
Sincerely,
Carl
via Dragon Dictate
The air cooled engines have problems too, ask me how I know. Researching both, Id take a 996 over an air cooled engine. Porsches cost now or later...do the research and get a decent PPI and you should be fine.
Ahsai, I'm just impressed that you know about and use Matlab!!
And, to the Other Carl, have you priced a new specialty crate engine from GM? They're only about $2-3k less than an M96, and that's close enough for me. The IMS bearing issues are a very small percentage of the overall 996 fleet. Remember also that you only hear about problems, never successes.
Read the IMS bearing sticky at the top to see how many enthusiasts have had zero problems.
Back to your regular program I've added photos showing where Porsche milled off material to balance the rods. Also photos of the JE piston which is very lean (light weight for its size so it's quite optimized and have no excess material to trim off).
Where the factory milled the big end to get it balanced
Factory trimmed another area on the big end
Side view, not a whole lot of material in that area.
Side view, not a whole lot of material in that area.
Little end. No trimming from factory
Not a whole lot of material if one needs to trim
Lean and mean precision JE pistons. The pistons are within 1.3g of each other.
Another angle. The only "safe" place to trim off weight
Another angle.
Side view. Not a whole lot of material can be removed.
An aluminum bar simulating how much to trim off 0.2g. It started with a right angle edge before trimming. Imagine removing that much from the piston in the background, granted the piston uses higher density aluminum but still
06-06-2016, 04:55 PM
I've added photos showing where Porsche milled off material to balance the rods. Also photos of the JE piston which is very lean (light weight for its size so it's quite optimized and have no excess material to trim off).
