HAS ANYONE GOT A SPARE 996 ENGINE
Discussion
MINE JUSTS DISAPPEARED IN A CLOUD OF SMOKE ON THE A331. EVEN THOSE NICE MEN IN BLUE STOPPED AS THEY THOUGHT I WAS GOING UP IN FLAMES.IT LOOKED SO SEVERE MOST PROBABLY THE DREADED CYCLINDER LINER HAS DROPPED SO I'M AFTER ANOTHER ENGINE.
FIRST ONE WENT AT ABOUT 102,000 THEN SECOND SECOND HAND ENGINE OF ABOUT 60K MILEAGE LASTED 5000 MILES THIS WILL BE THE THIRD. LUCKILY THE FIRST ONE WAS REPLACED BY THE PREVIOUS OWNER.
SO IF ANY KNOWS OF A 996 3.4 BEING BROKEN PLEASE GET IN TOUCH.
TEL 07801014843
CHEERS
GRAEME
FIRST ONE WENT AT ABOUT 102,000 THEN SECOND SECOND HAND ENGINE OF ABOUT 60K MILEAGE LASTED 5000 MILES THIS WILL BE THE THIRD. LUCKILY THE FIRST ONE WAS REPLACED BY THE PREVIOUS OWNER.
SO IF ANY KNOWS OF A 996 3.4 BEING BROKEN PLEASE GET IN TOUCH.
TEL 07801014843
CHEERS
GRAEME
I'm with Woogie on this... Before I bought my car I thought "oooh... That's quite cheap, if I supercharge it I could have a performance bargain"... Then I found out about all the engine troubles and I am slightly nervous about going the performance exhaust route, let alone a supercharger!
Get it rebuilt by Hartech or Autofarm with the Silsleeve liners, have a capacity increase to 3.7 and have low compression pistons installed. Your motor will then be bullet proof and probably be able to run more boost, giving you at least +50bhp and will probably make you fall in love with it all over again...
Thing is, that could cost you around £10k I would guess?!
Otherwise, sell the supercharger and put it back to standard, on a standard engine. I just get the impression there isn't much of a market for 2nd hand 996 superchargers? I think £5k should get you a recon engine at Autofarm... Check their website!
Get it rebuilt by Hartech or Autofarm with the Silsleeve liners, have a capacity increase to 3.7 and have low compression pistons installed. Your motor will then be bullet proof and probably be able to run more boost, giving you at least +50bhp and will probably make you fall in love with it all over again...
Thing is, that could cost you around £10k I would guess?!
Otherwise, sell the supercharger and put it back to standard, on a standard engine. I just get the impression there isn't much of a market for 2nd hand 996 superchargers? I think £5k should get you a recon engine at Autofarm... Check their website!
woogie said:
skidpan said:
I've lost faith in the car and so I'm looking to sell on as soon as its working, perhaps I shouldn't of fitted the supercharger.
Supercharger ? I am not an expert but with the amount of problems this engine is renowned for is it a good idea to supercharge it?The supercharging problem is two fold.
(1) If you supercharge or turbocharge an engine you raise the true compression ratio (remember the compression ratio quoted is only the theoretical ratio if the cylinder filling was 100%). The performance of an engine varies mainly with the true compression ratio at any one moment and anything that increases it within useable limits will increase performance. Camshafts, induction, exhausts, etc can also increase true compression ratio in the power band they were intended to operate in and therefore increase output but rarely by more than 100%, while any induction charging system easily exceeds 100% in the operating range.
So fitting a supercharger usually increases charge efficiency and true compression ratio at lower revs while fitting a turbocharger usually increases it at higher revs. Both need changes to the theoretical (or static) compression ratio to operate safely (lower static compression) and changes to the ignition timing, cam timing and fuelling.
Also pistons are made oval and tapered so that when they are at running temperature - they expand and fit into the bore more closely. The more relative power an engine produces the more taper and ovality you need to put on the pistons (as they will run hotter and get bigger at the top). This makes the top of the piston smaller than a lower power piston would be in the same engine. Although the 996 pistons are if anything over tapered - and although the bores have probably gone oval to increase the clearances, the extra cylinder pressure will increase blow by if the pistons do not expand and could seize.
So when an engine is tuned by turbocharging or supercharging - if it still runs OK on many of the original parts and control systems - it is just luck that it wasn't built to closer tolerances - and enables you to still get away with it more by luck than design but it always brings it nearer to some design limits.
A mild supercharger can improve torque at low revs and probably get away without too many other changes and so is an easier option than a turbocharger (and needs less intercooling). However, the big ends on a 996 (in common with all modern engines that seem to be being fitted with progressively relatively narrower shells) are a known weak spot - not too bad but one of the first things that will need replacing in an otherwise good high mileage engine. We are told this is to reduce friction and improve ecconomy although it is also a neat way to control eventual life expectancy.
For me this factor alone would make supercharging with this engine a risk (as the extra power/torque developed cross refers to extra load on the shells and as they are supported by oil pressure - a wider shell provides more support for longer) and so I would expect a reduced lifespan unless the supercharger worked only at low pressures and revs - in which case it is a lot of money for little reward.
The 996 has big end shells that could be 20% wider and still fit inside the original con rod and the crankshaft and so the big ends are one of the weak spots in these engines that could have been improved upon (the mains could also be 10% wider).
The shells we are having manufactured to enable us to regrind the crankshafts are being made to accomodate the extra widths available (to eventually improve yet another aspect of the standard engine during a rebuild) and we have already prepared a lower compression engine to fit them to and to induction charge.
This winter we intend to fit the engine into a track car as a mobile test laboratory in which to test extreme engine conditions. This will enable us to remove this weak spot from our engine and find out what is the next weak spot to address as soon as possible to prepare a solution - hopefully - before it hits higher mileage standard engines (and hopefully we can have a bit of fun in the process).
Baz
(1) If you supercharge or turbocharge an engine you raise the true compression ratio (remember the compression ratio quoted is only the theoretical ratio if the cylinder filling was 100%). The performance of an engine varies mainly with the true compression ratio at any one moment and anything that increases it within useable limits will increase performance. Camshafts, induction, exhausts, etc can also increase true compression ratio in the power band they were intended to operate in and therefore increase output but rarely by more than 100%, while any induction charging system easily exceeds 100% in the operating range.
So fitting a supercharger usually increases charge efficiency and true compression ratio at lower revs while fitting a turbocharger usually increases it at higher revs. Both need changes to the theoretical (or static) compression ratio to operate safely (lower static compression) and changes to the ignition timing, cam timing and fuelling.
Also pistons are made oval and tapered so that when they are at running temperature - they expand and fit into the bore more closely. The more relative power an engine produces the more taper and ovality you need to put on the pistons (as they will run hotter and get bigger at the top). This makes the top of the piston smaller than a lower power piston would be in the same engine. Although the 996 pistons are if anything over tapered - and although the bores have probably gone oval to increase the clearances, the extra cylinder pressure will increase blow by if the pistons do not expand and could seize.
So when an engine is tuned by turbocharging or supercharging - if it still runs OK on many of the original parts and control systems - it is just luck that it wasn't built to closer tolerances - and enables you to still get away with it more by luck than design but it always brings it nearer to some design limits.
A mild supercharger can improve torque at low revs and probably get away without too many other changes and so is an easier option than a turbocharger (and needs less intercooling). However, the big ends on a 996 (in common with all modern engines that seem to be being fitted with progressively relatively narrower shells) are a known weak spot - not too bad but one of the first things that will need replacing in an otherwise good high mileage engine. We are told this is to reduce friction and improve ecconomy although it is also a neat way to control eventual life expectancy.
For me this factor alone would make supercharging with this engine a risk (as the extra power/torque developed cross refers to extra load on the shells and as they are supported by oil pressure - a wider shell provides more support for longer) and so I would expect a reduced lifespan unless the supercharger worked only at low pressures and revs - in which case it is a lot of money for little reward.
The 996 has big end shells that could be 20% wider and still fit inside the original con rod and the crankshaft and so the big ends are one of the weak spots in these engines that could have been improved upon (the mains could also be 10% wider).
The shells we are having manufactured to enable us to regrind the crankshafts are being made to accomodate the extra widths available (to eventually improve yet another aspect of the standard engine during a rebuild) and we have already prepared a lower compression engine to fit them to and to induction charge.
This winter we intend to fit the engine into a track car as a mobile test laboratory in which to test extreme engine conditions. This will enable us to remove this weak spot from our engine and find out what is the next weak spot to address as soon as possible to prepare a solution - hopefully - before it hits higher mileage standard engines (and hopefully we can have a bit of fun in the process).
Baz
Thanks Fesuvious - I should have added as well that of course the cylinder walls on the 996 are thinner than the less powerful Boxster variants and so the added thrust and pressure from the bigger pistons (or a supercharger or turbocharger) would increase the forces that make then distort and go oval and crack. Our re-rounding system and support rings prevent this reoccuring but can only be done with the engine stripped (and a new liner can fix a cracked one).
We have engines and parts in stock but rather than fix a price to them we need to rebuild the damaged engine to maintain stock (or price the repair accordingly).
So regardless of the fault we use a spreadsheet system to work out the cost of fixing the damaged engine first. If it just has a broken chain, worn out intermediate shaft bearing or other minor problems - the rebuild cost will be less (911 - around £3900 + Vat with support rings and all the other modifications, improvements etc - exchange for customer replacement). Having worked out the cost - since all our engines are rebuilt to the same standard - another prebuilt engine can be used to save time but the cost relates to the damaged engine and the cost of repairing it. To make this really clear it means that if another rebuilt engine or bottom end is used the cost would be different if it was fitted to a car that originally had mild engine damage compared to one that had severe engine damage.
If the crankshaft is damaged beyond repair it adds around £2500 to the price (if a new crankshaft is needed) although we do offer good used parts as an option at about 50% retail new prices (this will change and be less when we can offer reground crankshafts with different shells). We have found signs of crankshaft failure before the crankshaft was damaged and saved the customer a lot of money but it does depend on early diagnosis and trusting the advice given. I have noticed that a lot of people who have recently bought a car then experience a crankshaft failure within a few days, weeks or miles and can only conclude that some cars that are suspected are about to fail - then quickly find their way into a car showroom (often without the knowledge of the business who could be equally conned by the original owner) and waranties rarely cover any or much of the repair cost.
It is possible therefore that a rebuilt engine can cost almost as much as a new one or considerably less - depending on the amount of and nature of the original damage. If we do the whole job from starting the diagnosis to finishing with a repaired running car - the usual cost is around £4000 to £5000 (but can be a lot less or a bit more depending upon the original fault and damage).
We also offer replacement blocks (without heads) for garages and competant home mechanics to rebuild and replace for around £2200 + Vat (911 with no cylinder damage) to £2600 + Vat (if a liner is needed)(£1700 for a Boxster).
Always we need the old engine or block and can only finalise the price when we assess the damage. We can price it up from a list but must check out the accuracy before final invoicing. Engines are therefore always on an exchange basis (Boxsters cost less as the bores do not distort like the 911's).
So far we have never been unable to rebuild every engine we have received although we have seen one elsehwere that would be cheaper to replace with a new one (or good used parts) and it is always a possibility if the damage is severe.
Most engines - upon inspection - are far less damaged than we were led to believe and relatively easy to handle and inexpensive to repair. Two engines actually had nothing wrong inside (the fault was external and could have been repaired with removal for a few hundred pounds). Four engines could have been repaired by removing the heads or replacing the intermediate shaft bearing while the engine was still in the car.
Unfortuately - by the time we get the car the engines have often been stripped elsewhere and as we can only rebuild with new gaskets, seals etc and insist on new shells and modifications - end up costing far more than they should have done and could have done if we had been able to diagnose the problem before someone else made the wrong decisions and took things further than was neccessary. The crankshafts journals only have a hardness depth of 0.001" or 0.025mm (unlike older models in which they could be 50 or 60 times deeper) so once the failing bearing has broken through the hard skin - failure is fast and quickly finishes the crankshaft, shell and con-rod off.
The most difficult to diagnose is a ticking or knocking which experience has shown us can sometimes be the intermediate shaft bearing (early signs), a big end or main bearing shell or something to do with a chain or guide.
Usually if we can hear this from under the car we can tell if it is central or at the heads.
If it is central we offer to remove the gearbox and flywheel and check if it is the bearing (as this is relatively cheap to replace/improve and we don't then need to remove or strip the engine). If the bearing is OK we have to go on to strip the whole thing but then don't charge for the extra work stripping down to the bearing - so customers can only win if it was that and should have nothing to complain about if it was not. Despite this one customer who had all this explained still fell out with us because it didn't turn out to be the bearing (that we were not going to charge for anyway if it wasn't that - just trying to save him money by looking there first).
Smoking can be caused simply by an exterior oil seperator - or a faulty air mass sensor or oxygen sensor but can also be a cracked liner etc - so again early diagnosis is beneficial to avoid unneccessary costs.
Oil and coolant mixed in the coolant (not the sump) can be a cracked cylinder head - again not needing an engine strip or removal.
Being able to hear the engine running with the fault is a great help since other faults in the management system or wiring etc could have caused a mechanical engine failure which otherwise would still be present after rebuilding the engine and running it again and the right diagnosis and cost estimate is easiest to do then before stripping the whole thing down.
In all this the experience we have of repairing and fixing lots of engines in similar circumstances is the best way to find the right diagnosis and the most cost effective repair.
I imagine we have probably seen and repaired many more engines of all sizes (from 2.5 to 3.6 litre) and/or offer more repair options (with in house machining facilites to replace liners etc) than most and so are probably the most likely to both get the diagnosis right and then offer the best repair options, but you cannot please everyone all of the time and even with all this available, customers faced with unexpectedly high repair costs that render their car totally unecconomic to own and repair - often want someone to blame and seek the cheapest solutions and can still make the job really hard to handle at times even when you are offering the best workmanship and options available and trying your best to help them.
Baz
We have engines and parts in stock but rather than fix a price to them we need to rebuild the damaged engine to maintain stock (or price the repair accordingly).
So regardless of the fault we use a spreadsheet system to work out the cost of fixing the damaged engine first. If it just has a broken chain, worn out intermediate shaft bearing or other minor problems - the rebuild cost will be less (911 - around £3900 + Vat with support rings and all the other modifications, improvements etc - exchange for customer replacement). Having worked out the cost - since all our engines are rebuilt to the same standard - another prebuilt engine can be used to save time but the cost relates to the damaged engine and the cost of repairing it. To make this really clear it means that if another rebuilt engine or bottom end is used the cost would be different if it was fitted to a car that originally had mild engine damage compared to one that had severe engine damage.
If the crankshaft is damaged beyond repair it adds around £2500 to the price (if a new crankshaft is needed) although we do offer good used parts as an option at about 50% retail new prices (this will change and be less when we can offer reground crankshafts with different shells). We have found signs of crankshaft failure before the crankshaft was damaged and saved the customer a lot of money but it does depend on early diagnosis and trusting the advice given. I have noticed that a lot of people who have recently bought a car then experience a crankshaft failure within a few days, weeks or miles and can only conclude that some cars that are suspected are about to fail - then quickly find their way into a car showroom (often without the knowledge of the business who could be equally conned by the original owner) and waranties rarely cover any or much of the repair cost.
It is possible therefore that a rebuilt engine can cost almost as much as a new one or considerably less - depending on the amount of and nature of the original damage. If we do the whole job from starting the diagnosis to finishing with a repaired running car - the usual cost is around £4000 to £5000 (but can be a lot less or a bit more depending upon the original fault and damage).
We also offer replacement blocks (without heads) for garages and competant home mechanics to rebuild and replace for around £2200 + Vat (911 with no cylinder damage) to £2600 + Vat (if a liner is needed)(£1700 for a Boxster).
Always we need the old engine or block and can only finalise the price when we assess the damage. We can price it up from a list but must check out the accuracy before final invoicing. Engines are therefore always on an exchange basis (Boxsters cost less as the bores do not distort like the 911's).
So far we have never been unable to rebuild every engine we have received although we have seen one elsehwere that would be cheaper to replace with a new one (or good used parts) and it is always a possibility if the damage is severe.
Most engines - upon inspection - are far less damaged than we were led to believe and relatively easy to handle and inexpensive to repair. Two engines actually had nothing wrong inside (the fault was external and could have been repaired with removal for a few hundred pounds). Four engines could have been repaired by removing the heads or replacing the intermediate shaft bearing while the engine was still in the car.
Unfortuately - by the time we get the car the engines have often been stripped elsewhere and as we can only rebuild with new gaskets, seals etc and insist on new shells and modifications - end up costing far more than they should have done and could have done if we had been able to diagnose the problem before someone else made the wrong decisions and took things further than was neccessary. The crankshafts journals only have a hardness depth of 0.001" or 0.025mm (unlike older models in which they could be 50 or 60 times deeper) so once the failing bearing has broken through the hard skin - failure is fast and quickly finishes the crankshaft, shell and con-rod off.
The most difficult to diagnose is a ticking or knocking which experience has shown us can sometimes be the intermediate shaft bearing (early signs), a big end or main bearing shell or something to do with a chain or guide.
Usually if we can hear this from under the car we can tell if it is central or at the heads.
If it is central we offer to remove the gearbox and flywheel and check if it is the bearing (as this is relatively cheap to replace/improve and we don't then need to remove or strip the engine). If the bearing is OK we have to go on to strip the whole thing but then don't charge for the extra work stripping down to the bearing - so customers can only win if it was that and should have nothing to complain about if it was not. Despite this one customer who had all this explained still fell out with us because it didn't turn out to be the bearing (that we were not going to charge for anyway if it wasn't that - just trying to save him money by looking there first).
Smoking can be caused simply by an exterior oil seperator - or a faulty air mass sensor or oxygen sensor but can also be a cracked liner etc - so again early diagnosis is beneficial to avoid unneccessary costs.
Oil and coolant mixed in the coolant (not the sump) can be a cracked cylinder head - again not needing an engine strip or removal.
Being able to hear the engine running with the fault is a great help since other faults in the management system or wiring etc could have caused a mechanical engine failure which otherwise would still be present after rebuilding the engine and running it again and the right diagnosis and cost estimate is easiest to do then before stripping the whole thing down.
In all this the experience we have of repairing and fixing lots of engines in similar circumstances is the best way to find the right diagnosis and the most cost effective repair.
I imagine we have probably seen and repaired many more engines of all sizes (from 2.5 to 3.6 litre) and/or offer more repair options (with in house machining facilites to replace liners etc) than most and so are probably the most likely to both get the diagnosis right and then offer the best repair options, but you cannot please everyone all of the time and even with all this available, customers faced with unexpectedly high repair costs that render their car totally unecconomic to own and repair - often want someone to blame and seek the cheapest solutions and can still make the job really hard to handle at times even when you are offering the best workmanship and options available and trying your best to help them.
Baz
hartech said:
It is possible therefore that a rebuilt engine can cost almost as much as a new one or considerably less...
This is astonishingly true... the exchange cost of a brand new Porsche engine from the factory can be lower than you think... forget GT3 engines and stuff like that, but for standard stuff it can be down to 5-6k IIRC.Yes Domster and of course prices vary Worldwide and with exchange rates but the last time I checked - although th e 3.6 had dropped in price - the 3.4 was still expensive in the UK - but having said that nothing would please me more than finding prices falling for engines - as people with these problems need all the help they can get (and IMHO should be getting more from Porsche than they do).
You should also remember however that our prices where an engine is fitted include the strip and rebuild, getting running etc and you have to part exchange a rebuilt engine (even if it is all broken inside) or pay an extra surcharge (recently nearer £2.5 or even 3K I think) so if it was stripped to find the fault it may need to be put together again (all at someones cost) and this must also be added to the cost.
Furthermore the new engine will not have some of the beneficial mods that we do to our rebuilt ones - but don't think I am against fitting one if it is a cheaper or better option - its just that usually it isn't unless there is widespread engine damage in the first place.
Baz
You should also remember however that our prices where an engine is fitted include the strip and rebuild, getting running etc and you have to part exchange a rebuilt engine (even if it is all broken inside) or pay an extra surcharge (recently nearer £2.5 or even 3K I think) so if it was stripped to find the fault it may need to be put together again (all at someones cost) and this must also be added to the cost.
Furthermore the new engine will not have some of the beneficial mods that we do to our rebuilt ones - but don't think I am against fitting one if it is a cheaper or better option - its just that usually it isn't unless there is widespread engine damage in the first place.
Baz
Gassing Station | Porsche General | Top of Page | What's New | My Stuff