Peter M Posted 29March, 2020 Author Report Share Posted 29March, 2020 Mike, I think the torque characteristics are more greatly influenced by the "tune" than any likely bore and stoke combination for the same capacity engine. If you want bulk low and mid range torque I think you should be aiming larger capacity and/or turbocharging with a modern tech turbo tuned specifically for street use. The whole "big stroke = big low down grunt" is so clouded in exceptions and other details that there is much more to the story. The first consideration is that the cylinder pressure produced by the expanding gases reaches its peak shortly after combustion begins, when the volume above the piston is still relatively small and the lever arm created by the piston, rod and crank pin is an acute angle of less than 90 degrees. Peak cylinder pressure occurs at approximately 20 degrees ATDC, and drops dramatically by the time that the rod has its maximum leverage against the crank arm. Consequently the mechanical torque advantage of a long stroke is significantly diminished by the reduced force that’s pushing against the piston when the leverage of a long crankshaft stroke is greatest. Efficiency in converting fuel and air into torque is the result of many factors, including airflow, combustion and parasitic losses such as friction and windage. Comparing two engines with the same displacement, a long-stroke/small-bore combination is simply less efficient than a short-stroke/big-bore combination in the first place on several counts: If you compare cylinder head airflow on a small-bore test fixture and on a large-bore fixture, the bigger bore will almost invariably improve airflow due to less valve shrouding and the potential for larger valves. A short crankshaft stroke reduces parasitic losses as ring drag is the major source of internal friction. With a shorter stroke, the pistons don’t travel as far with every revolution and windage is reduced as the crankshaft assembly cuts through a smaller arc. I think there are much more cost-effective ways to tailor an engines torque curve than to use a long stroke crank and small bore. The intake manifold, cylinder head inlet runner volume and camshaft timing all have a much more significant impact on the torque curve than stroke and are much easier and cheaper to change. However if someone was to give me a 76.4mm GT3 crank with matching conrods and pistons, I would be over the moon and would take take it in a heartbeat but would be trying to maximise my engine capacity for my ideal street motor any way I could, larger bore or larger stroke, within my budget, as my first priority, rather than focusing on bore to stroke ratios! (I admit I'd be trying to maximise my conrod length in this conversion though!) . tomo 1 Quote Link to comment Share on other sites More sharing options...
tomo Posted 29March, 2020 Report Share Posted 29March, 2020 A Disscussion on stroke versus bore http://performancedevelopments.com/gt3-engine-displacement/ Mike D'Silva and Peter M 2 Quote Link to comment Share on other sites More sharing options...
Mike D'Silva Posted 20April, 2020 Report Share Posted 20April, 2020 I think what Neil is saying is roughly what I was suggesting.. If you feel you want a track only engine, go with the big bore but don’t forget about the intake and head flow along with camshaft configuration. If you are a street driver who sometimes tracks the car, go with the stroke. Most drivers are not at a pro level and heavy on the brakes which drops the engine speed through and out of the corners. You need the low end torque to get the car accelerating back up to speed. So, to sum up, what’s the best configuration? Our dyno testing has shown that the 4.0L long stroke long rod engine is better suited for most street and track use over the big bore engine. If you can afford to, do both. But remember as bore goes up so does weight and weight plays a huge part in an engines life and RPM potential. Well designed and well made parts are essential and there lies a lot of the differences available to customers of these engines. Remember, these engines have an inherent low engine RPM harmonic. Performance Developments designed the GT3.1 balancer to counter this and will soon release the balancer for the GT3.2 engine. Whatever is done to your engine, engine safety must still be number one priority and the builders underlying consideration. tomo 1 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 20April, 2020 Author Report Share Posted 20April, 2020 9 hours ago, Mike D'Silva said: If you can afford to, do both. Actually Mike, he is saying what I'm saying, go larger capacity by any practical (and affordable) means! 😉 Quote Link to comment Share on other sites More sharing options...
tomo Posted 20April, 2020 Report Share Posted 20April, 2020 Only if you can juggle reciprocal mass with stroke to maintain a safe engine. Quote Link to comment Share on other sites More sharing options...
OZ930 Posted 20April, 2020 Report Share Posted 20April, 2020 1 hour ago, Peter M said: Actually Mike, he is saying what I'm saying, go larger capacity by any practical (and affordable) means! 😉 So what you are saying is: “There’s no substitute for cubic inches” Peter M 1 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 21April, 2020 Author Report Share Posted 21April, 2020 7 hours ago, tomo said: Only if you can juggle reciprocal mass with stroke to maintain a safe engine. With a Mezger, the oil pump location effectively limits the maximum stoke that can be run due to limited clearance. The location of the head studs effectively limits the maximum size of the bore. So really there are only a few "affordable" options to increase the capacity of these engines. I should say "nearly affordable" options as anytime you think of doing work on these engines it's mega bucks for every extra HP. Unless you go turbo of course, then it's just big bucks! tomo 1 Quote Link to comment Share on other sites More sharing options...
Mike D'Silva Posted 21April, 2020 Report Share Posted 21April, 2020 Absolutely, if the budget is there, increase stroke and bore. If only limited budget, consider the main use of the car, before choosing only 1 method. On our next engine, we are looking to decrease rod angle as well as increase stroke... longer rods, and custom pistons. tomo and Peter M 2 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 21April, 2020 Author Report Share Posted 21April, 2020 Windscreen Trim Replacement I'll just park this here for later. I want to replace my rear window trim one day. http://forums.pelicanparts.com/porsche-911-technical-forum/837568-easy-windshield-trim-install-2.html Quote Link to comment Share on other sites More sharing options...
Peter M Posted 2May, 2020 Author Report Share Posted 2May, 2020 How have I managed to overlook the coolest 3.2 ever? I still remember as a wide eyed 21 year old reading the Road and Track comparison where a small hotrod shop in a place I couldn't pronounce absolutely blitzed it. Still a great read today, 33 years later: https://www.roadandtrack.com/car-culture/a29347/the-worlds-fastest-cars-1987/ 9r 1 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 2May, 2020 Author Report Share Posted 2May, 2020 Actually this may even be cooler: History buffs will know the first cars had 3.2's and how Rene possibly buggered up winning the 1985 Paris Dakar by not crimping over a fractured cam chain tensioner oil line. He though tape would fix the leak....... More great photos here: https://rmsothebys.com/en/auctions/po18/the-porsche-70th-anniversary-auction/lots/r0016-1985-porsche-959-paris-dakar/696785 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 2May, 2020 Author Report Share Posted 2May, 2020 Air Conditioning I had the AC regassed at the end of last year but by March it was evident that it was losing pressure and I likely needed to replace a few of the original hoses. I was also interested in improving the airflow in the cabin and spent some time understanding how the ducting worked on the later 3.2's and replacing seals in the fresh air system to make sure I wasn't having the hot external air mixing with the refrigerated air. I also tested the airflow directly from the evaporator box and found that impressive but even though the route is reasonably direct in the later 3.2's, I couldn't work out why it should be so much less forceful by the time it got to the driver's side vent. At the same time I was chasing a refrigerant leak in my XJ6 and at over 200 bucks a regas, I though this was expensive and somewhat environmentally insensitive. I had noticed the cost of a vacuum pump and gauge set on eBay was about the same cost as a professional 134a regas. After a bit of a hunt around for Hychill suppliers, I decided to set myself up as a DIY air conditioning mechanic. The XJ, like every old car I've had required a full AC rebuild, including an 6 hour dash out evaporator replacement. That wasn't too bad as my 993 as it took 10 hours to do the same thing, but from the frunk side! Evacuating the system after replacing a hose end fitting that didn't give the clearance to the chassis that I wanted. Vacuuming the system before recharging with Hychill Minus 30. I've only replaced a few AC items on the red car so far - receiver/dryer, front condensor, evaporator and blower motor - but I foresee at least upgrading all the old non-barrier hose as my next job. As an example of my peerless timing I now have the AC working well in both cars. It's just that the temp expected here today is 12 degrees with an overnight low of -2! Quote Link to comment Share on other sites More sharing options...
jakroo Posted 2May, 2020 Report Share Posted 2May, 2020 On 17/02/2020 at 19:31, Peter M said: Missus said to me yesterday: "You know those cars that wake you up in the middle of the night because they are so loud that you just wish the driver would crash and die so you can go back to sleep? Your red car is that loud." GULP!😨 I know I've already done this but I just wanted to quote this again cos it's so funny. TwoHeadsTas and Peter M 2 Quote Link to comment Share on other sites More sharing options...
9r Posted 3May, 2020 Report Share Posted 3May, 2020 16 hours ago, Peter M said: How have I managed to overlook the coolest 3.2 ever? I still remember as a wide eyed 21 year old reading the Road and Track comparison where a small hotrod shop in a place I couldn't pronounce absolutely blitzed it. Still a great read today, 33 years later: https://www.roadandtrack.com/car-culture/a29347/the-worlds-fastest-cars-1987/ Peter that brought back similar memories for me 🙂. My dad gave me a subscription to R&T as a young teenager to encourage me to read more and those top speed articles they did blew my mind (and also gave me a lesson on how the Italian brands tended to exaggerate their car capabilities / horsepower and the Germans under estimated. In saying that there is an early 70’s picture R&T did of the Ferrari Daytona dashboard at an indicated 180mph on a Nevada highway that was impressive. Think I need to go out to the garage now and dig through some boxes as I still have 100’s of those magazines out there somewhere 😬 Peter M 1 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 3May, 2020 Author Report Share Posted 3May, 2020 Scomo said "Go catch up with your friends". Mmmm, after some wondering and bit of a Google search I decided I needed to catch up with Chris and Tash and enjoy their hospitality. The trip started out cold but clear. A quick stretch of the legs at Apsley Falls was appreciated: How can this World Heritage area, with a spectacular slate gorge be so unknown? Pushing on got us to Long Flat eventually where we enjoyed Tash's (takeaway) cooking and had a chat to Chris while he worked on his Triton out the front. I know it's hard to believe but they were both completely oblivious that I had befriended them. I hadn't been down the Oxley Highway since the bushfires and the closures. Happy to report the road is as good as it ever was with only a few less trees. Lot's of bikes as usual and barely any cars and it appears Ginger's Creek roadhouse have decided to open again this weekend after closing about 5 weeks ago for COVID. firstone 1 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 5May, 2020 Author Report Share Posted 5May, 2020 Made in China rockers? These look pretty good and would not be surprised if the one's I bought through Design 911, at twice the price, are actually made in China as well. The truth is we'll never know but frankly as long as the quality is there, who cares about country of origin. https://www.cxracing.com/RRA-P010?search=porsche https://www.cxracing.com/engine-connecting-rods-rockers-crankshaft/RRA-P010-SHAFTx12?sort=p.price&order=ASC Maybe a set of rods for about the same cost of ARP rod bolts? https://www.cxracing.com/ROD-PORSCHE-32-1270x6?search=porsche Quote Link to comment Share on other sites More sharing options...
Mike D'Silva Posted 5May, 2020 Report Share Posted 5May, 2020 Yes, I saw those a couple weeks ago. They make a few parts for porsches.. rocker shafts too.. so cheap. BUT, I don't want to be the guinea pig! I just wonder how well they will hold up before pitting, galling etc.. Quote Link to comment Share on other sites More sharing options...
Peter M Posted 5May, 2020 Author Report Share Posted 5May, 2020 Mike, If the feedback on the the quality of the products is good for the other parts, I can't see how that wouldn't apply to the Porsche parts and give us confidence to give them a go. Also, it's not as though the rods and rockers on an old 911 are particularly stressed compared to other higher Hp per litre engines. Quote Link to comment Share on other sites More sharing options...
Peter M Posted 7May, 2020 Author Report Share Posted 7May, 2020 Rear Reflectors 3.2's came with 3 different types of reflectors: The black lettered ones for MY '84 & '85 (plus earlier SC's and C3.o's). Sorry I don't have the part number at hand The first clear lettered version for MY '86. Part No. 911.631.432.01 The clear lettered, double reflector squares at each end and wider flanged top edge with simplified top only fixing method for MY '87, '88 & '89. Part No. 911.633.123.02 Stepo and Dreamr 2 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 8May, 2020 Author Report Share Posted 8May, 2020 High Mileage I think 250,000km is a lot, but I found the discussion about this 3.2 with 729,000km interesting: http://forums.pelicanparts.com/porsche-911-technical-forum/1060381-why-do-professionaly-built-porsche-engines-cost-much-they-do.html Quote Link to comment Share on other sites More sharing options...
tomo Posted 8May, 2020 Report Share Posted 8May, 2020 Damn good effort, 291000 on the first motor, he has clocked up 150000 since the build, So in theory he should be good for the next 140000 , Wonder how the body is holding up . Quote Link to comment Share on other sites More sharing options...
Peter M Posted 8May, 2020 Author Report Share Posted 8May, 2020 1 hour ago, tomo said: Damn good effort, 291000 on the first motor....... Wonder how the body is holding up . That's 468,000km! I've never seen a G body with fatigue cracks, unlike 240Z's and early Commodores for example and they never give the impression of flexing much so I guess the body still feels like new! I like Michael Stahl's description of 911's solidarity as though they've been "marinated in Loctite for a week." tomo 1 Quote Link to comment Share on other sites More sharing options...
Peter M Posted 12May, 2020 Author Report Share Posted 12May, 2020 On 14/08/2019 at 18:11, Peter M said: Mike, They were returned out of spec for roundness. They came back the second time absolutely perfect. Interesting threads on Nikasil Cylinders. It's not as foolproof as I thought: http://forums.pelicanparts.com/911-engine-rebuilding-forum/1060471-cylinder-finish-issues.html http://forums.pelicanparts.com/911-engine-rebuilding-forum/912382-millenium-cylinder-fine-grit-honing-right-way-go.html#post10033067 Quote Link to comment Share on other sites More sharing options...
tomo Posted 12May, 2020 Report Share Posted 12May, 2020 49 minutes ago, Peter M said: Interesting thread on Nikasil'ng cylinders. It's not as foolproof as I thought: http://forums.pelicanparts.com/911-engine-rebuilding-forum/1060471-cylinder-finish-issues.html What a PITA that turned out to be . Good to know going forward though . Quote Link to comment Share on other sites More sharing options...
3legs Posted 12May, 2020 Report Share Posted 12May, 2020 On 06/05/2020 at 06:59, Peter M said: Made in China rockers? These look pretty good and would not be surprised if the one's I bought through Design 911, at twice the price, are actually made in China as well. The truth is we'll never know but frankly as long as the quality is there, who cares about country of origin. https://www.cxracing.com/RRA-P010?search=porsche https://www.cxracing.com/engine-connecting-rods-rockers-crankshaft/RRA-P010-SHAFTx12?sort=p.price&order=ASC Maybe a set of rods for about the same cost of ARP rod bolts? https://www.cxracing.com/ROD-PORSCHE-32-1270x6?search=porsche Something you may want to think about buying chinese made steel products. I used to use a Made in England Flexitor suspension block for my motorcycle sidecar and never had an issue with them. Anyway the old one was getting a bit worn because of all the pounding on outback roads so I bought a new one from the same place I bought the old one from 10 years earlier and fitted that. I got as far as 50km's south of Mt Dare station and the sidecar wheel was nearly touching the sidecar body because the shaft had bent. Had to turn around and slowly ride back to Coober Pedy hoping it wouldn't snap. Flew home and got a trailer and drove back the next day to pick it up. Anyway I took the unit off and went back to the place I bought it from and showed him and he gave a new one free of charge but when I asked him why it bent and I never had a problem in the past he just said "made in china" with metal forged in china. Didn't have to say anymore. I knew exactly what he meant and he was almost embarrassed to be selling them. So if I can confirm that any thing made of metal was made in china I will NOT buy it. BTW the new block never went on. I made my own swingarm suspension using a shock not made in china. firstone 1 Quote Link to comment Share on other sites More sharing options...
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