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Who has put these AA biral cylinders in their bus and how did it work out? Lower CHT's? Oil is cooler?

Bleyseng wrote:Who has put these AA biral cylinders in their bus and how did it work out? Lower CHT's? Oil is cooler?

Blaah.
Colin
(a solution not only in search of a problem, but problems aplenty. When Mahle/Porsche did it, their machining and casting was up to the challenge under keeping the iron undistorted. The minute attempts were made for bigger bore, apparently the distortion would work the aluminum off the iron.
As mentioned TO YOU right HERE some time ago, we NEED the damn cylinder barrels to HEAT UP ahead of the pistons under load or you get SCUFFING which is what the 94mm engines TSB was about)

ok, I understand but in real world useage of AA birals, how do they work out? I am not going to pop for a set of nickies unless I install that set of 103mm ones I have on the shelf. Hmm, how would Ljet like that I wonder? 103x71 is 2.4L almost so it should work, no? I should just build it and see.

I have a set of AA's 85.5 in a non bus application. They are in my baja which see's some pretty hard use at times and i'm happy with these, but I had a set of 87's and after MUCH tinkering, found out the barrel heights were different. Trust nothing,check everything.

Bleyseng wrote:Who has put these AA biral cylinders in their bus and how did it work out? Lower CHT's? Oil is cooler?

So far 7500+ miles and counting. No problems so far. Using 96mm AA birals. oil consumption so far is very minimal...1/8th every 1200 or so maybe not even that.

72Hardtop wrote:

Bleyseng wrote:Who has put these AA biral cylinders in their bus and how did it work out? Lower CHT's? Oil is cooler?

So far 7500+ miles and counting. No problems so far. Using 96mm AA birals. oil consumption so far is very minimal...1/8th every 1200 or so maybe not even that.

What did they . . . ahem, cost?
Colin

https://aapistons.com/collections/porsc ... linder-set

They were all less than .5 grams within one another and ring end gaps were within spec.

In the AA picture the pistons are the shorter skirt type which I had trouble with (94mm Flat tops). My looks like direct copy of 914 2.0L pistons AA set seems to work a lot better without piston slap when cold. Hopefully, they won't wearout due to "piston rock" either.

I don't notice any noise with these and I believe they are taller than the older generation sets.

19,XXX miles and counting....no issues. Oil consumption is very low. Trip (summer 2014) from Seattle - Carlsbad, Ca. and back 2925 miles consumed under 2/3qt total was still settling in after top end rebuild.

Good to hear, thanks. The link posted above is dead now, do you think you could find an updated version for the readership?

Robbie

in theory they would run cooler. I do know that when we used to bore motorcycle cylinders that were biral they flexed like heck and it took all day to bore one because the honing pressure had to be so low to avoid honing the cylinder out of round. The only thing I see that could be an issue besides that is if a separation occurs the temperatures will be higher than stock cast iron. I think the general industry uses a thermal coating to drop temps more than choosing biral cylinders.

asiab3 wrote: ↑

Sun Jun 18, 2017 8:38 am

Good to hear, thanks. The link posted above is dead now, do you think you could find an updated version for the readership?

Robbie

Updated.

sgkent wrote: ↑

Sun Jun 18, 2017 10:07 am

in theory they would run cooler. I do know that when we used to bore motorcycle cylinders that were biral they flexed like heck and it took all day to bore one because the honing pressure had to be so low to avoid honing the cylinder out of round. The only thing I see that could be an issue besides that is if a separation occurs the temperatures will be higher than stock cast iron. I think the general industry uses a thermal coating to drop temps more than choosing biral cylinders.

One lesson from awhile back was not to use stacked ring/fins to create the biral cylinders. My understanding from talking to a few engineers that knew about them was today's method involves coatings as well as metallurgy changes between the cylinders & outer aluminum fins (1 piece entirely) and increasing the interference fit with cryo methods to increase bonding.

Update:

Approaching 35,XXX miles (US) and all is well. Oil usage is very minimal at roughly ~1/4qt per 1200 miles