sandwedge

I'd like to know too but not because I'm concerned but just out of curiosity. I think the lack of reliable info for 9A1 rebuilds is due to the fact that they are rare. The one discussed in this thread is the first one I've ever heard or read about. Read somewhere that Porsche basically over engineered the 9A1 engine after the IMS fiascos with the previous engines.

rmstar

Thanks to Jake, Charles & Baz for in depth engine info and maintenance/procedure to minimize the engine problem in the future. And especially Bronz who unfortunately has to pay for this, sorry mate. Anyway, for Bronz's new cylinder bore, Jake will be using Nikasil plating method because it's the only proven, cost effective way for the used engine bore coated with silicon carbine. Porsche use Alusil bore which process from an aluminum silicon carbine block, for some (or all?) of 991.1 (can't find info in 991.2 or 992) which also expose silicon carbine on the surface. Both methods should more or less will give the bore same protection assuming no fault during plating/manufacture process. Let's leave Nikasil vs Alusil for another debate. Now back to how reliable for 9A1 rebuilds question? I assume there are only 2 significant variables introduce into the rebuild. It's all come down to how good new piston and the Nikasil coating bore from LN engineer can withstand. I would think the new Nikasil bore coating and new piston are the weakest link, not from Jake's Flat6 Innovation group workmanship as I found many good thing about this group. I also do not to imply LN engineer group is not up to their standard, merely question the Nikasil method since it's a trade secret that everyone keep for themselves, hence not easy to make an educated guess. How about other replacement parts? DF injectors? etc, need to be replaced? OEM parts are the only choice and it is NOT a variable in this rebuild equation. The question should be "How reliable the new 3rd party piston and new Nikasil bore combo will last?" Time will tell as the sample size for 9A1 rebuild is still too small for meaningful statistics. Last but not least is human variable, not easy to quantify ;-) Good luck Bronz.

Prairiedawg

Just curious, what manufacture year were those 5 engines? Were they all '09 model years, early production?

bazhart

Nikasil plated directly on the block is not "the only way". There are 3 ways to Nikasil an alloy cylinder block that we are aware of.

(1) Direct plating onto the original Alusil bore. (we have no experience of this and have heard mixed feedback - mostly good with an occasional adhesion problem reported).
(2) Machining out the old bore to fit a thin dry alloy liner with Nikasil plating. Should be a good solution for M96/7 engines as long as it is combined with a closed deck top - otherwise 2 tubes fitted inside each other are usually less stiff than one tube of the same overall dimensions leading to the possibility of movement of the liner.
(3) Completely machining out the whole original bore and fitting a thick, wet Nikasil plated liner that also fits into a precision machined recess to close the top of the deck and stabilise the bore (we also add a bottom ring to close the deck top and bottom with our oversized engine conversions for M96/7 engines (see Hartech web site)). The Gen 2 9A1 does not need a lower ring because a wet liner fits top, middle and bottom anyway. Several thousand of our Aeorpace alloy Nikasil plated and ribbed closed deck wet liners have been fitted by us to M96/7 engines for more than 12 years with no problems.

The Gen 2 9A1 is a much more challenging job but we have done it by sticking to our original proven solution of a thick wet liner (also all ribbed externally to improve heat transfer).

I will try and attach photos (showing how we include the original spray jets).

We cannot claim anything about how successful this 9A1 repair will be until we cover more miles but it is the same as we have already fitted to thousands of engines, almost the same as the liners in the M96/7 GT3 and Turbos and which we have fitted to 9 different engines types successfully - so fingers crossed should be OK.

There are several ways to rebuild a 9A1 engine with failed bores.

You can replace the blocks with new, sleeve the block by one of the above methods and/or change the capacity at the same time.

The cost of increasing the capacity to 4.0 depends on if the donor engine is a 3.6 or 3.8 and if it is damaged or not.

We have not completed enough rebuilds to price up every variable (and it always depends upon the condition we find inside) but re-sleeving just 2 scored bores and doing the whole job with the whole car might be around £10K, whereas making a 4.0 from the most expensive solution may cost up to £15K.

Just repairing crankcases may be around £4K.

We will have more firm prices as we do more repairs.

Baz

BruceWarne

rmstar

Solution 3) sound like perfect. However, your 3 methods are still a 3 variation within Nikasil plated technology. After read more about Porsche continue using Alusil method for 991 engine, I would think the most logical way, yet difficult, would be using the same Alusil method due to the fact that the aluminum engine block is already infused with silicon carbine. So, there is another way, Alusil method, to approach this. Please comment on this.
https://www.sunnen.com/NewsDetails.aspx?NewsID=11
Thanks again for very informative info

rw229

The belt tensioner is completely external to the engine, and would (could) affect the water pump and alternator. Unless the engine was over heated due to lack of cooling, which I don't recall that happening in this case, I don't think the belt tensioner comes in to play.

rw229

While we're testing theories, it would be interesting to know from Flat Six, Baz and other rebuilders if they have seen any pattern based on the transmission type in the car. (997.2)

In my experience, the 997.2 PDK will lug the sh*t out of the engine unless you're on it, in sport mode, or keeping the revs up in manual mode.

My understanding is that one of the contributors to LSPI could be hard acceleration from low RPM. The PDK will downshift pretty quick, but I'm wondering if cruising at 35-40 mph in 6th gear (par for PDK in auto, non-sport mode) and then accelerating could contribute to the issue?

sandwedge

They will. It's been said before but the PDK shouldn't be sold without sport chrono. And even with that, some will still stay in normal mode/auto and end up in 6th. gear at 30 mph. I touched on this on another thread tonight. Just seems to be a lot of confusion or lack of proper introduction to the various configurations of the PDK by those who sell PDK cars.

user 72902

Interesting thread and I'll add from a more global perspective. Every manufacturer produces an engine that is better than the previous edition. The M96/97 which I have is a good motor and the A91 is better; that's just how engineers operate. All engines no matter how bullet proof they are have an Achilles' heel. The question "What causes bore scoring?" is a simple one but as others have state above has a complex answer. In general fuels have become less kind (more so in winter blends) to cars. What impact does the driver's habits play into scoring? How do maintenance regimes fit in and so on. Then I think about modern engines today versus engines from 30 years ago. Today engines are half the mass putting out twice the power while reducing emissions, noise, and running more efficiently. In short I think there is just no margin engineered into them so they operate on the edge. In the end I have no need to own Porsches so they are strictly a luxury item and an expense for fun. Unfortunately we will not get a magic answer on how to prevent major damage other than the common sense advice provided. Perform frequent oil changes and let your oil warm up before driving it hard. If we do this it seems the odds are low that we will experience a major problem.

bazhart

Just 2 comments.

(1) Not sure how gearboxes, oils, fuels or injectors can make the bottom of a cylinder bore shrink inwards until it traps the piston on warm up.
(2) Nikasil is not like Alusil or Lokasil both of which require a hard coating on the piston to survive long term.
Alusil can get away with a less hard coating than Lokasil but still needs one because although the silicon particles are smaller and better distributed they still come loose and can impinge on the piston coating. When this happens, because the base matrix is still aluminium the damage usually results in a deep score or leads to lots of deep scores when the parts dig deep into the aluminium surface.

Nikasil forms a complete thin skin strongly bonded to the aluminium and a smooth but oleophilic surface that does not need any piston coating to survive (although a plastic coating can make lifespan even better).

If we receive an engine in which say a valve seat has dropped or a big end failed (often from racing when the owner has not fitted a proper sump that holds oil or an Accusump) the debris usually doesn't even penetrate the Nikasil and frequently can be re-honed and re-used but never has that been the case with Alusil or Lokasil.

Nikasil is the most expensive to apply but by far the best surface (possible exceptions the latest plasma spray techniques for the future).

The very rare cylinder shrinkage problem with 9A1 could have been minimised with more piston ovality (and perhaps it was - we simply don't know yet). The pistons have less ovality than previous models presumably to try and spread the load over a larger piston area because the new coating is not as hard as the old one?

Baz

Brainz

Thanks to Baz and Jake for sharing this knowledge. Great insights.

Chris M.

From a 991.1? You're already rebuilding some of these?

Chaos

Best wishes to Bronz and thank you for the education.

Also bigjule is on the "ignore " list...

edomund

I'm wondering the same thing as Baz, "Not sure how gearboxes, oils, fuels or injectors can make the bottom of a cylinder bore shrink inwards until it traps the piston on warm up". If this failure was caused by LSPI or any detonation event you should see evidence of damage to the piston ie. cracked, melted, pitting etc. I've had detonation cause failure in a turbo RX7 and it blew apart the apex seal and bent the rotor sideways. This seems more along the lines of what Baz has seen and thoroughly detailed in this thread. This could be confirmed with measuring the bores. It would also make sense why Jake's and Baz' rebuilds eliminates the issue going forward as it bores out the shrank area.