Bore scoring on refurbished engine

[AlexH997]

All
How many of you have had your motors suffer from bore scoring again after they've been repaired under warranty?

Does Porsche actually fix the problem or do they plaster over it.

[AlexH997]

I sent my car in cos a thought it was suing a lot of oil and pipes were dirty but they said it was ok. The advisor said it would be repaired by their technicians on site.

Luckily mine is ok but all this talk of scoring makes me wonder even if they didn't repair would they fix the cause

[AlexH997]

hartech said:

I have not seen any evidence of technical changes to a new or Porsche rebuilt engine to eliminate bore scoring - nor any changes to reduce the likelyhood.

We believe the problem is caused by the Lokasil material being particularly aggresive as it wears, the temperature between the piston and the bore too high on occasions (reducing the oil film strength and allowing too much piston face to bore pressure), the type of coating on the pistons (being too soft to resist the interference of sharp or mislodged Lokasil particles), the coolant temperature being too high and the coolant flow resulting in the top of bank 2 pistons (the thrust face) running hotter (which is the side that fails) than the bottom of bank 1 (also the thrust face) which lasts much longer.

When we rebuild engines we do offer to modify some areas that we believe contribute to the problem.

We replace liners with Nikasil plated ones (or re-round and support open deck Lokasil bores to reduce blow bye and reduce piston face temperatures). We can fit a lower temperature thermostat and we increase the coolant flow through the block to lower cylinder temperatures.

We also have an on going serious and expensive research and development programme that has been testing various cylinder bore materials, different pistons and different piston coatings. This is very time consuming as it is neccessary to cover many thousands of miles between each strip, inspection and rebuild. Results one day will be revealed when the programme has been completed.

However - despite a lot of costs, frustrations and set backs - we are getting very close to finding the answers we need to decide on the best or least expensive way forward for the next decade of rebuilding these flawed engines.

We say least expensive because replacing all the cylinders with alloy Nikasil plated cylinders (as used in Gt3's, turbos and even the older air cooled cylinders) is a permanent solution but obviously expensive and we have been trying to find a less expensive way to produce as reliable results.

Porsche didn't seem to provide anything to sort the problem out except to eventually abandon the Lokasil cylinder material and return to Alusil in Gen 2 engines (as used in the 944's and 968's etc). Boxsters up to 3.2 and 3.4 996 engines do not suffer the problem (despite also running in Lokasil) and bank one is much less vulnerable and this gives hope that there is a less expensive answer to be found.

But this leaves thousands of cars vulnerable to expensive rebuilds or replacements which we are still trying to find a less expensive permanent solution for than our reliable Nikasil replacements.


Baz

You've identified a fix but do you know what the actual problem is Is it caused by particular driving style?

My sister is looking at buying a 997.1 cab and there is one for sale which has had the engine refurbed by Porsche 1500 miles ago due to bore scoring.

She's only concerned with the colour but I'm wondering how long will the engine last before the same thing occurs, she's a crap driver anyway but is there anything she can do driving wise to stop it from happening. The car she's looking at is 2005 with 48k miles. Would it be another 8yrs and 48k miles before it happens again?

[AlexH997]

So if you're hammering the car away from standstill when the engine is warm will cause scored cylinders?

i just read about a cayman owner who had scored cylinders and owned his car from new. Never ragged or tracked it, sounded like general daily driving and he suffered with scored cylinders. Must be more to it.

doing some further searching tonight suggests cars getting from 6yrs old are all suffering in some way.

[AlexH997]

Magic919 said:

Tips suffer at least as much as manuals, if not worse. Carrera S Tip would be an ideal candidate for scoring, as would a 2006 Cayman S.

You've made a statement but can you explain why you think that? What's so specific about a Carrera S Tip?

[AlexH997]

hartech said:

Bore scoring is known historically to occur mostly at low revs and high torque. The problem started when the variable valve-lift systems increased low speed torque – so there is a clue (although other changes were made at about the same time to coolant flow balance and piston coatings). Tiptronics set of usually in 2nd and this requires more torque to get the same acceleration than a manual in 1st – so if you are going to get away quickly in a tip it would be better to flick it into 1st.

Not sure I understand. Every time i pull away from a stand still or a junction I never accelerate hard I probably use less than 3k rpm. You mentioned bore scoring occurs at low revs and high torque. With the car being in 2nd gear creating the higher torque and me acclerating slow using low revs does that mean my driving style is likely to increase the chance of my engine suffering for bore scoring? should i be dropping the car into 1st every time i drive away and accelerate up to 4k or have i got the wrong end of the stick!!!?

I do appreciate the effort youve made to cover what appears to be a technical topic but I can't sign up from your plan until my warranty runs out. my Car is a Cab does the plan cover broken hoods?

[AlexH997]

Trev450 said:

Yes we southerners have been trying to persuade Baz to open another shop closer to us for some time now but no joy yet.

there is a porsche garage in dorset which does a similar maintenance plan can't remember its name.

[AlexH997]

hartech said:

We test drove manuals and tiptronics and found that in a manual car most drivers don't accelerate from below 2,500 rpm (they change down earlier) whereas by contrast tiptronic drivers often accelerate reasonably hard without the gearbox kicking down - from lower revs (and the incidence of scoring seems to occur more with tiptronics).

The variable valve lift and timing technology allows quite high torque at these low revs so it is used more for adequate driving speeds.

All previous research into bore scoring (or scuffing as it is often referred to) has been found to occur at low revs with big capacity engines. It seems that as the speed of the piston moving up the cylinder bore increases the contact between the piston and the cylinder changes and causes less problems.

Thanks Baz. I think I understand what you mean. I take it it's not just from a standstill, if you're cruising at 40mph and then accelerate fast, manual drivers will normally drop down a gear (high revs, less torque) whereas tiptronic will accelerate in the current gear (lower revs/under higher torque)

I have a tiptronic with sports chrono. Would driving around with sports chrono on help? my understanding it that it keeps the rev ranges higher and therefore I would assume keep the car in lower gears preventing the low revs/high torque scenerio you mentioned?

hartech said:

Most of our customers on the plan are from down South (where I come from) and find no problem at all in coming up to see us once a year for their annual services or transporting their car in the rare event that it stops running. However if there is a similar scheme near you I think it would be worthwhile going on it - the idea behind it does for the first time put the specialist in a position where he only benefits if he does a great job of servicing and repairing your car and fixes weaknesses before they escalate into bigger problems.
The only way we could operate a South East version of Hartech would be at increased prices (due to the higher cost of industrial space and wage levels there). How much extra would you consider it viable at?

Based on what you've posted and the investment you've made in understanding and identifying solutions for these problems I'd say the monthly cost is reasonable for what you get. You're actually only 3.5hrs away. JMG is probably 2hrs away so not much in it.

[AlexH997]

petop said:

My C4S had IMS failure Feb last year which resulted in OPC Guildford fitting a new engine. Bill which is in the glove compartment still is for £16,000.

You paid £16k or was that covered under warranty. what driving experience did you encounter when the ims failed?

[AlexH997]

hartech said:

sorry about your bill Petop - would have been far less at an independent. It will be interesting to find out how well the new engines perform in time.

baz - that got me thinking. If my ims failed and I sent my car to your place would you replace the failed bearing with the same part or do you fit a stronger bearing that wont fail?

would you fit nikosil liners as part of the rebuild to prevent future bore scoring at additional cost or again replace it with like for like? excuse the tone of the question if it's not as simple as that.

[AlexH997]

hartech said:

We have found that manual cars driven largely on track don't seem to suffer and all 4 of our Porsche Club race cars in our Hartech team are still using original Lokasil cylinders (even though we could have fitted our superior Nikasil plated alloy liners) using Lokasil as part of our research program and have so far been 100% reliable (despite leading the team award and winning the last 2 races). Obviously these do not experience any low revs driving.

Are you the only specialist who rebuild with nikasil plated alloy liners of is it common knowledge to repair them with something other than lokasil?

[AlexH997]

petop said:

Sorry, this was paid for by previous owner. But i got the 2 year warranty on the engine alone from Porsche.

you done well there. Owner must have had deep pockets

[AlexH997]

Budweiser said:

A very interesting and informative thread.

Advice please.. I am a new to me owner of a 204MY C4S 996. 73K one owner with a full OPC service history. The previous owner took the attitude, if OPC says it needs doing, do it so no expense spared. I have all the invoices for the work carried out for the life of the car.

I've just had a minor service carried out at OPC Colchester and a low temp thermostat fitted by Autostrasse, my local indie.

The car drives and sounds fantastic and there are no obvious problems.

Like a lot of owners I am concerned about BS and IMS so believing prevention is better than cure would it make sense to have the bores checked visually and if clear have a new modified IMS bearing fitted? Don't get me wrong I'm as keen as anyone to save money but an investment now may prove prudent in the future? Any thoughts would be appreciated.



If I did decide to change the IMS what is considered the best bearing to use? And what are the likely costs involved?

The car is a manual..

Thanks. Don.

Edited by Budweiser on Friday 24th May 13:09

Don I'm with you on this one seems quite a few owners have the same thoughts. i got opc warranty left to cover me short term but a rebuild and ims update could be on the cards.

hopefully baz can answer some of the questions he seems to be the subject matter expert on all this engine related.

[AlexH997]

So baz i have a 2005 997 is there any point in have an ims bearing upgrade or should i just wait until it's failed and then send it to yours to to have ims bearing and nikasil liners installed as part of a refurb>

[AlexH997]

hartech said:

Sorry guys will reply to all questions next Monday too much on this week good questions though need some time to reply to hope you can be patient regards Baz

Baz any chance you could answer some of the outstanding questions im thinking of having the ims bearing upgraded but would like your views on this before I proceed