Boxob Posted December 10, 2015 Report Share Posted December 10, 2015 33 minutes ago, Buzzfox said: This might be a stupid question but why would a step in the bore develop because of constant rev speed? The piston travel can't vary with engine speed so how does the wear pattern vary? Actually piston travel within the bore does vary with speed or more accurately with revs. The con rods connecting the piston to the crank "stretch" albeit microscopically. Consequently at a constant rev the piston reaches its maximum travel at the same point in the bore which leads to a step in the side of the bore. Vary the revs and the piston maxs its travel at different points so no step. That's the theory then again I could be writing b*ll*x! Link to comment Share on other sites More sharing options...
Araf Posted December 10, 2015 Report Share Posted December 10, 2015 12 hours ago, Buzzfox said: This might be a stupid question but why would a step in the bore develop because of constant rev speed? The piston travel can't vary with engine speed so how does the wear pattern vary? Good question, and yes, the piston travel does vary. It's a minute amount, but every change of direction either stretches or compressed components depending on the force acting on them. Not by a lot, but at high engine speeds, the pistons (and more importantly the piston rings) travel further than at low engine speeds. In order to stop the step developing, one solution that manufacturers tried was a hard bore coating (Nikasil, ceramic or chrome) and soft piston rings, but bore platings can come off, resulting in a wrecked engine. Most have reverted to cast liners and hardened rings. Link to comment Share on other sites More sharing options...
Lurker Posted December 13, 2015 Report Share Posted December 13, 2015 I was told 1000km run in from my dealer. I'm now at around 700 miles and until around 600 miles I used 4.5k as my rev limit and tried to change gear a bit more often for much of my motorway driving. In traffic I understand actually this is ok for running in compared to motorway as you are changing revs/gear. A run down the A303 to Devon and back also seemed like perfect running in driving! The main thing I'm told is to not push it when the car is cold - that trumps all running in tips/procedure. Common sense really. I just wait till the oil is past the cold market before going above 3k RPM. I'll dig up an excellent post on running in later... I had 2 or 3 accidental moments on down shifts past 4.5k, but again, I think common sense says it's fine so long as it's not the norm in terms of the way you broke in the engine during the run in period... I will not be nannying my engine for 3000km, that's for sure. The car is tucked up for the winter now as I'm going away, but I'll be going past 4.5k now sometimes, if not thrashing it of course when I get back in it in January. Link to comment Share on other sites More sharing options...
Lurker Posted December 13, 2015 Report Share Posted December 13, 2015 This is what I read. http://rennlist.com/forums/991/706897-the-official-porsche-engine-break-in-running-in-instructions-3.html And the key info: "- For the first couple of hundred miles drive the car gently; no high revs and don't let the engine labour. The main thing here is bedding in tyres and brakes.- Up to around 500 miles, vary engine load and speed. Use perhaps 2/3rd of the rev range (when warm of course). No full throttle.- Between 500 and 1,000 miles start to use more of the revs, and larger (occasional full) throttle openings. (I tend to up my rev limit 1,000 rpm per 100 miles.)- Beyond 1,000 miles drive the car as you wish.He confirmed that most GT engines develop their full potential around 10,000 miles - most 3.8 RS engines were over 460hp (10 up on OEM figures) at this mileage. I've pretty much used AP's technique for years now - most notably on a 996 GT3 Gen 2 that has now done 60,000 miles, half on track. The engine uses no oil, and still develops 430 hp (it has a Manthey map and exhaust). " Link to comment Share on other sites More sharing options...
Buzzfox Posted December 14, 2015 Report Share Posted December 14, 2015 15 hours ago, Lurker said: This is what I read. http://rennlist.com/forums/991/706897-the-official-porsche-engine-break-in-running-in-instructions-3.html Interesting reading but the last post on that thread has puzzled me. It reads "There's a negative consequence to early oil changes (after the initial flush to take out assembly residues) and there's a lot of energy going into rings and valve gear". What is the negative consequence of an early oil change? I ask as I've got an oil change booked for the end of the month which will, according to the service schedule, be about 18500 miles early!! Link to comment Share on other sites More sharing options...
DJMC Posted December 14, 2015 Report Share Posted December 14, 2015 On 9 December 2015 23:56:50, Buzzfox said: This might be a stupid question but why would a step in the bore develop because of constant rev speed? The piston travel can't vary with engine speed so how does the wear pattern vary? Go here: http://papers.sae.org/2000-01-1788/ Then click "Preview Technical Paper" to the right. There's just enough info to see that RPM and cylinder pressure have an effect on piston ring contact with the bore. This in turn would account for differences in wear rate depending on the "sliding distance" of the rings (bottom left of P.2 titled "Cylinder Bore Wear Distribution"), which is dependant on RPM. I'm guessing that, with higher RPMs, the ring does actually travel further up the bore by a minute distance. Therefore, if you used low revs constantly the ring would always travel to the same point (as you say) creating a step. Increasing the revs only much later would mean the top ring has to "jump" over this step, or crash into it. Link to comment Share on other sites More sharing options...
Buzzfox Posted December 14, 2015 Report Share Posted December 14, 2015 On 10/12/2015 12:22:30, Araf said: Good question, and yes, the piston travel does vary. It's a minute amount, but every change of direction either stretches or compressed components depending on the force acting on them. Not by a lot, but at high engine speeds, the pistons (and more importantly the piston rings) travel further than at low engine speeds. In order to stop the step developing, one solution that manufacturers tried was a hard bore coating (Nikasil, ceramic or chrome) and soft piston rings, but bore platings can come off, resulting in a wrecked engine. Most have reverted to cast liners and hardened rings. Thanks to everyone who answered this one for me, makes sense. Learning, learning, all the time learning!! Link to comment Share on other sites More sharing options...
JohnSyn Posted December 14, 2015 Author Report Share Posted December 14, 2015 Interesting how much different advice there is on what should be a relatively simple issue! I've booked mine in for an oil change over the Christmas break and will do little mileage between now and then so will be at circa 1200 miles. After this I intend to gradually open it up and get to max revs at 2000 miles. I've decided to do what I think is right and just get on with it. Hopefully this will mean its fine by the time spring comes! Link to comment Share on other sites More sharing options...
Lurker Posted December 14, 2015 Report Share Posted December 14, 2015 2 hours ago, Buzzfox said: Interesting reading but the last post on that thread has puzzled me. It reads "There's a negative consequence to early oil changes (after the initial flush to take out assembly residues) and there's a lot of energy going into rings and valve gear". What is the negative consequence of an early oil change? I ask as I've got an oil change booked for the end of the month which will, according to the service schedule, be about 18500 miles early!! I wondered exactly the same thing. Link to comment Share on other sites More sharing options...
Araf Posted December 14, 2015 Report Share Posted December 14, 2015 It used to be that a poorer quality oil was used for the first fill, or a cutting agent was added to the oil, to help with the bedding in process. This would be dropped from the car after 1000 miles, and the engine filled with the correct spec for the rest of the engine's life. It could even be that just the residue from the bench test has been calculated as sufficient if allowed to circulate for the first 20k to do the same job. By changing the oil, you're halting that process. Link to comment Share on other sites More sharing options...
Buzzfox Posted December 14, 2015 Report Share Posted December 14, 2015 46 minutes ago, Araf said: It used to be that a poorer quality oil was used for the first fill, or a cutting agent was added to the oil, to help with the bedding in process. This would be dropped from the car after 1000 miles, and the engine filled with the correct spec for the rest of the engine's life. It could even be that just the residue from the bench test has been calculated as sufficient if allowed to circulate for the first 20k to do the same job. By changing the oil, you're halting that process. This really isn't helping my Porsche paranoia!! Link to comment Share on other sites More sharing options...
Araf Posted December 14, 2015 Report Share Posted December 14, 2015 With the time you've been around them, it should have quelled. It's a car with a petrol engine. The technology is 100 years old, and if the worst happens, you can bolt a couple of bits of timber to the front of the car and harness a horse to it. Cars are thrashed from cold, and from day 1. They usually loosen up quicker, produce more power, and wear out quicker - but they still work fine until that day. If you baby it and it stays tight, then it may take 20k or 30k to loosen up, but will last longer (and will probably be a few hp shy of one that has been abused). You won't break it, and you're talking about losing out on 1 or 2% of the potential. Link to comment Share on other sites More sharing options...
topradio Posted December 14, 2015 Report Share Posted December 14, 2015 When I used to have a real job I inherited a Cavalier with 150K on the clock from a salesman who had thrashed it from day one. It was possibly the most loose car I had ever driven but it did go like stink. Anyway one day the head gasket went while driving on the M25 and the temp gauge hit the end stop so I rang the company to ask if it had breakdown cover. They said they didn't think so and I was to 'sort it out'. So thinking that I needed to put the car out of it misery I drove it another 50 miles to my destination and booked it in with the nearest Vauxhall dealer for what I thought would be a funeral service. I got a call the next day from the dealer to say they had changed the head gasket and thermostat and it was ready! I swear that after that it went even faster than it had before I tried to kill it. Link to comment Share on other sites More sharing options...
Lurker Posted December 14, 2015 Report Share Posted December 14, 2015 1 hour ago, Araf said: With the time you've been around them, it should have quelled. It's a car with a petrol engine. The technology is 100 years old, and if the worst happens, you can bolt a couple of bits of timber to the front of the car and harness a horse to it. Cars are thrashed from cold, and from day 1. They usually loosen up quicker, produce more power, and wear out quicker - but they still work fine until that day. If you baby it and it stays tight, then it may take 20k or 30k to loosen up, but will last longer (and will probably be a few hp shy of one that has been abused). You won't break it, and you're talking about losing out on 1 or 2% of the potential. That's good enough justification for me! I'm increasing from now on and driving it properly! But I couldn't have brought myself to thrash it from day one like I did with my lease BMW! Link to comment Share on other sites More sharing options...
Araf Posted December 14, 2015 Report Share Posted December 14, 2015 Look at the F1 heyday, when manufacturers could run as many engines as they liked in a season. The sign of a successful engine was one that blew right after the finishing line. They were built really loose - what would otherwise be classed as close to knackered, to last 200 or so miles. They could have built them tighter, and make them last a whole season, but that would lose them 50 or so hp - and that was the difference between making an overtake, or losing. Link to comment Share on other sites More sharing options...
JohnSyn Posted December 30, 2015 Author Report Share Posted December 30, 2015 Had the oil and filter changed today and met Araf at the OPC, see other post. The car has now done 1300 miles, I went for a bit of a drive after leaving the OPC. I'm now taking it up to 5k revs. Blimey....it sounds even better! I've decided to take the advice many of you have given and increase the revs to max, 7.5k, over the next few hundred miles. Link to comment Share on other sites More sharing options...
JohnSyn Posted January 5, 2016 Author Report Share Posted January 5, 2016 Long run out yesterday, the car has now done 1500 miles. A bit disappointing as weather forecast said it would be ok but got quite heavy rain whilst out. Still...I got to put the hood up in record time! In Sport Plus the car sounds really good when 'pressing on' on country roads! Link to comment Share on other sites More sharing options...
JohnSyn Posted February 21, 2016 Author Report Share Posted February 21, 2016 Run out to Brooklands breakfast this morning with my local TIPEC group. Had a greatbtimebthere, put another 120 miles on car and opened it up to 6k revs. It sounded great and really was a joy to drive. So looking forward to light nights/ early mornings! Link to comment Share on other sites More sharing options...
Kevin G Posted February 21, 2016 Report Share Posted February 21, 2016 Enjoy John, just enjoy. Kevin Link to comment Share on other sites More sharing options...
JohnSyn Posted February 21, 2016 Author Report Share Posted February 21, 2016 I am Kevin thanks...so much! Link to comment Share on other sites More sharing options...
Guvs Posted February 22, 2016 Report Share Posted February 22, 2016 Hi John just reading through this whole thread and all I can say is "time to enjoy your spyder now" let go and have some fun. Guvs. Link to comment Share on other sites More sharing options...
JohnSyn Posted February 28, 2016 Author Report Share Posted February 28, 2016 The car goes into the OPCs next week to have its hood replaced. Some stitching has come undone under one of the 'flaps' at the back and, for some reason, they are replacing the hood rather than repairing it! Any way, that's not the reason for posting. I'm rather taken by the side decals that the 987 Spyders have and was thinking of getting them fitted. However, when I was much younger, I had what we called then go fast strips fitted to my modified Anglia and Cooper S. I wonder whether they are generational and an old git like me should not indulge. Any views....nice ones though please Link to comment Share on other sites More sharing options...
Gutley Posted February 28, 2016 Report Share Posted February 28, 2016 1. I guess it's actually cheaper for them to swap the entire hood and repair it back at factory than to bring in a specialist to fix it in situ they'd still probably have to remove it anyway to avoid damaging the bodywork 2. Would they work with the giant side pods and the fact the door is inset from the main body line? Got any examples? Link to comment Share on other sites More sharing options...
JohnSyn Posted February 28, 2016 Author Report Share Posted February 28, 2016 Link to comment Share on other sites More sharing options...
JohnSyn Posted February 28, 2016 Author Report Share Posted February 28, 2016 Interestingly Matt Porsche seem to have your question covered! Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.