Flat6 Innovations

You can see for yourself in the class, I have a carrier as a "visual aid".

Ahsai

Ok, I'll wait and hit you with tons of questions in the class

Flat6 Innovations

Thats what the class is for....

Sneaky Pete

Ashai you really have a gift/passion for this! But I'd love to know where Martin went. A lot of technical data was being offered up and he is MIA.

From your local arrogant American.

Ahsai

Thanks Pete. I'm glad Jake and Martin took the fight somewhere else and called a truce on 9/11.

I measured the cylinders on this 100k engine with a bore gauge zeroed at 3.7795" (0.00005" resolution and 0.0003" accuracy) and here's what I found (@80F ambient). Of course this is what Jake has been telling us. I measured 3 positions at 0.5", 2.5" and 3.5" from top of the cylinder on two planes (thrust and non-thrust) so a total of 36 measurements on 6 cylinders.

The worst oval occurs at the top of the cylinder (not surprising). On the thrust side it's stretched outward but on the non-thrust side (90 degree from the thrust side), it's "squeezed" inwards.

Also, compared to the top, the cylinder tapers narrower when you go from top to bottom on the thrust plane. However, on the non-thrust plane, the cylinder tapers WIDER when you go from top to bottom (hence negative taper on the non-thrust plane).

Also, cyl #2 and #5 are the worst, similar to what Jake posted before.

Ovality (thou +/- 0.6 thou), Taper 1 (thrust plane), Taper 2 (non-thrust plane)
Cyl1 4.15, 1.65, -1.95
Cyl2 7.45, 3.15, -3.35
Cyl3 5.80, 2.30, -2.25
Cyl4 4.55, 1.70, -1.55
Cyl5 7.70, 2.80, -2.95
Cyl6 3.85, 1.55, -1.40

Flat6 Innovations

Glad to see that you recorded this and individually quantified my findings. No one listens when I say it.

That's an excellent bit of data, and your image is revealing. Mind if I add this to my class?

Now you see why all parent material is removed at the water jacket side of the block when using Nickies. The parent cylinder material is not stable.

Yes, truce for me today. I decided to actually take a day off to work on my Testarossa 😎

Ahsai

Thanks Jake and you're more than welcome to use it anywhere you like.

I definitely see why the parent material is removed at the water jacket side as it gets deformed by the pistons. Just wondering why the LN Nickies don't use a stabilizing ring to mimic a close-deck design to add more strength to the top of the cylinders?

It's funny "work on Testarossa" = day off. I can see how much passion you have. Enjoy your day!

Schnell Gelb

Ahsai,
Thanks for posting the ovality and taper. Only those of us who have attempted a meticulous rebuild will understand the value of the data you offered.
When I made theses same measurements I was unable to find any M96 comparative numbers. One of the 'sources' I enjoyed was jafromobile on Youtube and this one:
http://biosystems.okstate.edu/home/f...inderTaper.htm
Just researching the best tools to perform accurate measurements was a project!
I am very familiar with such tools but found it difficult with the M96. The critical test was to attempt to replicate the same measurements 3 consecutive times and get exactly the same readings.
For those who are thinking "what is the problem ?" -remember we are talking of a replicated accuracy required of +/-,1/10th or 1 thou.
Since I was not confident my own measurements were accurate,nor did I know what the limits of servicability were I never published the results because they could have been misleading.
You have made a huge contribution to diy M96 rebuilds because to incur all the expense,time and anxiety but produce a poor rebuild is sad.
Once the limits for ovality and taper are published here, it will make a "Nickies decision" much easier.
Thank you for publishing your data.

Flat6 Innovations

Simply adding this sealing area at the top of the cylinders reduces cooling capability, due to the design of the cylinder head. Retaining the open deck is the best form of cooling the hottest portion of the cylinder.

The Nickies billet extrusion is so strong that this is also not necessary.

Remember, I love to flank the industry, and pull rabbits out of my hat... So you never know what we've already done.

Schnell Gelb

Ovality (thou +/- 0.6 thou), Taper 1 (thrust plane), Taper 2 (non-thrust plane)
Cyl1 4.15, 1.65, -1.95
Cyl2 7.45, 3.15, -3.35
Cyl3 5.80, 2.30, -2.25
Cyl4 4.55, 1.70, -1.55
Cyl5 7.70, 2.80, -2.95
Cyl6 3.85, 1.55, -1.40
Ahsai's numbers are a great start but unless you know the wear limits this is just data not information ?
The conventional wisdom for other engines may be useless ?
To get the discussion started I would guess (what a stupid word to use in this context!) that the ovality limit should be 4 thou at 100Kmiles.
Taper should be less than 2 thou.
I am well aware that some modern engines have a taper limit of much less than 1 thou ! And that high tension rings may be a palliative but I can't find reliable info on this. And how would you 'match' ring gap to the ovality/taper you find -even if it is within the unknown limits?

Ahsai

Thanks, Schnell.

Yes, the tools are tricky to use at first but after some practice they are quite easy and I took multiple measurements at around the same spots (of course you can never be on the exact same spot unless you mark it but then you're adding thickness albeit maybe negligible) and I'm amazed how reproducible they are.

I'm pretty confident about the bore gauge readings since it only measures the length difference but if someone tries to derive the absolute dimensions from my data, they have to realize that the absolute values will only be as good as the micrometer I used (0.0001" resolution), which in turn is calibrated using the 2" measuring rod that comes with the kit. I don't know how accurate that measuring rod is. If we need absolute dimensions, I think the best is to get a quality measuring rod (e.g., Starrett) to calibrate the micrometer but those are not cheap.

The tools I used.

Ahsai

Thanks, Jake. That makes sense. The ring will be surrounding the cylinder at the top in place of coolant so that would prevent the coolant from circulating that part of the cylinder and the head to remove heat effectively.

Ahsai

I have the 2005 Cayenne piston/cylinder spec and tolerance. They don't spec limits for ovality and taper. They only spec the cylinder diameter wear limit: 3 thou compared to the original bore size (which they published) measured at 6 positions along the cylinder similar to what I did.

I don't even know the exact bore size of M96 so I just used 96mm as a base. It won't affect my ovality/taper measurements anyway. I would think the diameter at the lower part of the cylinder where the webbing is heaviest and where the rings don't touch will be close to the stock diameter.

Charles Navarro

Would you mind sharing with me the wear data for the Cayenne? Was it for the V8 or the VR6? I've never seen any limits published anywhere. I've always gone with the limits from the aircooled cylinders of max .002" ovality and taper in the cylinders. Unless a block is new or very low mileage, they always are out of spec - most are a minimum of .005" ovaled - the worst we found had .015" ovality.

That is why we instruct shops that are doing repairs not to re-ring the pistons if they aren't re-doing the bores. They are better re-using the original rings per position since they have already worn to match the bores. New rings will never seat otherwise.

alpine003

After hearing you say that, it seems like common sense but something a lot of people probably don't think about.