Cast Iron vs. Biral

[F1BADUDE]

Besides cooling benefits and mass reductions, what, if any, are additional benefits of Biral over cast iron cylinders?
I'm building mild race and would like to know the benefits and disadvantages. Normal logic would follow cast iron would be more reliable but does it offset if there is more heat retention?
If it is not a huge difference on my build, I will just buy cast iron to save a few bucks.

Thanks,

[YTNUKLR]

Biral has no other benefits other than cooling I don't think, especially if you don't bore them out and weaken the "sleeve". Biral are just iron sleeves with aluminum fins, iron are just iron sleeves w/ iron fins. By the way I have a REALLY good set of iron 2.0 cyls if you're interested. You should be able to build an engine with about 170 hp on iron cylinders, more with bigger coolers.

[Eagledriver]

Don't know for sure but I would guess that the Biral would cool better due to the better conducting of heat that aluminum has. I'm sure either one would work but the iron cylinders might run hotter and so be less desirable for a race engine. Also our race cars tend to be even more tail heavy than a street car and so need to keep the back end as light as possible.

-Andy

[cnavarro]

From a manufacturer's standpoint, birals are a nightmare. For a street engine that isn't going to be driven hard, on average, they will increase reliability and reduce maintainence. On an engine that will be pushed hard (or if you even happen to break a belt) and overheated in the slightest bit, the weakness of the biral shines through. Heatsoak causes the aluminum to expand to the point where the transfer of heat off the steel liner is reduced, causing cylinder temperatures to rise even more. This happens till the cylinder either breaks, washboards, or goes out of round. That is why I never casted a biral, like Porsche's. A better idea, as done by some, is to press in a liner with an interference fit, say .0065" on diameter, but care has to be taken to ensure that the integrity of the aluminum portion is maintained. If not, they suffer the same failure mode of the twice cast biral. My alternative to this is to manufacture billet nikasil replacement cylinders for the smaller displacements where such a product was never offered by the manufacturer. Although slow movers, it's nice to know that there's always another option.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[wolfrennen]

Can someone post more details on why an engine builder would choose an all-cast iron cylinder for a street performance motor? My car's previous owner enlarged his 3.2-L Carrera motor to a 3.4-L, and the engine builder used cast iron cylinders with J&E dome pistons (9.5:1 compression). I spoke with the builder, and he mentioned dissimilar metals have different expansions when very hot; in his experience many aluminum cylinder motors would lose compression during high-stress use? I don't know anything about 911 motors. I just bought this car ('88 Carrera) last November with 11809 miles on the enlarged motor (the tub has 65K miles). The motor seems to run fine. It pulls strong, and I don't see the oil temps get hotter than 220F during high-stress use on the track (the car has a front-mounted oil cooler). When the motor sits a long time, it smokes a bit when started, but clears up when it's warmed up. It drips a little oil when it sits a long time. I use the car mainly for DE and short cruises down twisty roads.

[Flieger]

Aluminum cylinders are better even by his logic because they expand at the same rate as the case and pistons. You can also have the pistons tighter in the bore when cold and have better efficiency that way. You also pick up power and efficiency due to the Ni-SiC coating. LN Engineering's Nickies are the best for use with JE pistons. Aluminum is also lighter than cast iron. That is why the 911T used to have cast iron cylinders and the higher up models used MAHLE Aluminum, Nickasil coated cylinders.

[Flieger]

The 3.2 came with MAHLE, all Aluminum, Ni-SiC coated cylinders, not Biral, BTW.

[jeff eelkema]

I'll be building a high performance 2.0 MFi engine (66x81)for my 69E at some stage in the future and will save the complete, running, numbers matching original engine. So I have a clean sheet and already have a race prepped mag case and some ported 69S heads with matching throttles and stacks.

I'm assuming that the 69E would have used Birals originally but can someone confirm. I'm thinking of running around 10:1 cr, probably JE but not clear on cylinder options. Above was a comment about not boring birals and someone else mentioned interference fit a new sleeve. Given I need to buy core birals and rework either bore or re-sleeve, what other options do I have apart from Nickies, which look great but like all good things, aren't cheap?

I also recall some discussion a while ago about JE doing short skirt pistons for larger bore sizes but not the smaller stuff. Any further info on this while I'm thinking of this issue?

[chris_seven]

I must admit to being a fan of Biral Cylinders - mainly due to originality but also cost and I have to say that I have never seen any cylinders where the fins have detached from the cast iron liner but I am sure that this has happened.

The main culprit for this problem is always described as being due to differential expansion and without measurements it is difficult to prove or disprove but an examination of basic material properties would help.

Cylinder liners are generally made from 'cast iron' but this is never very well quantified and needs some better definition.

Liners are normally cast with a chill to conert he grey iron to a hard and wear resistant white iron and this results in some interesting changes.

Typical Grey Iron has a Coefficient of Expansion of about 11 x 10^-6 m/m/degK

White Iron has a value of around 15 x 10^-6 m/m/degK - much greater and closer to a cast aluminium.

A high silicon cast Aluminium such as LM6 would be around 20 x 10^-6 m/m/degK

If we look at a 2.0 litre cylinder it is quite easy to calculate the interface shear stress caused by differences in expansion and they come out at about 25MPa - equivalent to 3500psi. - this assumes bulk temperatures of around 150 degC

I find it difficult to imagine that this on its own would detach the fins from the liner and there are few other stresses operating and causing a problem.

The thermal cycle and differences in heat capacity would not really cause too much trouble as heat up and cool down rates are relatively slow and not in the land of thermal shock.

I think there may be other causes that have more of an influence.

New barrels made in the aftermarket may not be cat in ideal conditions and there may be interface issues but this would be asy to test with some fairly basic equipment.

Old barrels may well degrade with time at temperature.

Iron and Aluminium are not the best combination and in the molten condition will tend to form Laves Phases now more commonly referred to as Intermetallic Compounds.

These phases are Ionic in nature and have a fixed chemical relationship. They are very brittle and crack easily.

As diffusion can take place over long time periods I am reasonably confident that these films will thicken and become continuous and then could crack even at very low stress levels.

If new barrels are correctly manufactured they should be reliable and last as well as the originals

[wolfrennen]

I'm at a loss as to why the engine builder would enlarge a known high-durability 3.2 with iron cylinders. Seems like de-evolution? The only reason would be to cut costs in hot-rodding a 3.2 to 3.4? This iron-cylindered 3.4 motor seems to run strong for now. I just wonder how long this motor will last? Perhaps I shouldn't worry. The last 11809 miles on the enlarged engine accrued over 7 years time (since 2004)--the car averages 1687 miles per year of enthusiastic driving. At that rate the engine will have only 23618 miles, and I'll hopefully have enough money saved by 2018 to re-do this engine RIGHT--if it doesn't fail before then LOL.

Originally Posted by Flieger

The 3.2 came with MAHLE, all Aluminum, Ni-SiC coated cylinders, not Biral, BTW.

[Henry Schmidt]

First, I have never seen or heard of a manufacturer of all cast iron cylinders for a 3.2/3.4 98mm engine.
Motor Meister is notorious for boring the Nikasil cylinders and pressing in cast iron sleeves. Perhaps that's what you have.
As far as 2.0 cylinders go, we offer a custom design 81mm Nikasil cylinder that incorporates 906 full fin cooling and an updated head sealing system that offers better sealing and a more stable platform for a high performance engine. Special 906 cooling tin comes with the piston & cylinder sets.

Because these sets are custom made for each customers any compression ratio is available. You'll also find pricing commensurate to standard street piston and cylinder sets.

[wolfrennen]

Hi, Henry. According the builder, even the cooling fins are iron? On the track during a hot day the oil temps show 220F during high-rpm use (6800 to 7000 rpms prior to upshifts). This was from last month at Putnam Park with ambient air temps in the mid-90s F. That 220F oil temp reading was withOUT a left-side fan housing block-off plate installed (the heat and A/C are removed). The car has a front-mounted oil cooler, and a 993 Turbo S tail to divert cooling air into the engine compartment at high speed (see my garage pics). I recently had a Pelican Parts block off plate installed, so hopefully I'll see decreased engine temps (210F)?

[safe]

Originally Posted by wolfrennen

Hi, Henry. According the builder, even the cooling fins are iron? On the track during a hot day the oil temps show 220F during high-rpm use (6800 to 7000 rpms prior to upshifts). This was from last month at Putnam Park with ambient air temps in the mid-90s F. That 220F oil temp reading was withOUT a left-side fan housing block-off plate installed (the heat and A/C are removed). The car has a front-mounted oil cooler, and a 993 Turbo S tail to divert cooling air into the engine compartment at high speed (see my garage pics). I recently had a Pelican Parts block off plate installed, so hopefully I'll see decreased engine temps (210F)?

Get under your car and check if the fins are iron or aluminum.

[Flieger]

OK, I remember you- the one without the block-off plate. Cast iron cylinders and no block-off plate sound like something Motor Meister would do. If you have a MM engine, it is a grenade waiting to happen. Who did the work on it?

[wolfrennen]

Hi, Flieger and safe. I spoke with the engine builder (he is not anyone from Motor Meister). His cylinders are custom cast all-iron cylnders--walls and fins. You will not find them anywhere, except on this builder's race engines. He had his reasons for using all-iron cylinders (he's a bit eccentric--I'll admit). I'm in no position to do anything with his 3.4-L creation, since this motor (with just over 40 hours of hard use over the last 7 years since its build) is currently running strong under high heat stress conditions. I'm new to the Porsche 911, and am learning about the different "camps" regarding engine builders. Many of these builders have their own styles and egos, and that you become a "follower" of these different builders depending on your experience with a particular builder's work. I am forced to be in this builder's camp--since I'm running his creation in my '88 Carrera DE car--and it's a pretty fast car. I'll just enjoy it and hope for the best. Thanks everyone!

[Flieger]

I wouldn't want any more weight than necessary overhanging the rear axle. I hope those cast iron cylinders are super thin wall to get close to the weight of Aluminum.

[wolfrennen]

Hi Flieger. Yep. The all-iron cylinders add 5 lbs/cylinder, so 30 lbs total extra engine weight compared with "nickie" Mahles. That's why the car's lightened with all unnecessary accessories removed (no heat, no AC, all plumbing removed). Exhaust is all stainless steel custom headers with no cats. The interior is stripped and replaced with Alcantara cloth. The half roll cage is welded for added rear-end stiffness (see garage pics). The car has a front-mounted oil cooler with no oil thermostat to avoid any oil restrictions from the stock oil thermostat. Although this is a DE car, it's basically a race car with a minimal interior. It's tolerable to drive to/from the track. It really comes ALIVE when driven WOT on a race track--the exhaust note is addicting, as the tone changes to a basso profundo growl with pedal floored. Badass and fast LOL.

Originally Posted by Flieger

I wouldn't want any more weight than necessary overhanging the rear axle. I hope those cast iron cylinders are super thin wall to get close to the weight of Aluminum.

[Flieger]

Sounds a lot like my car. I would want a thermostat, though, to make the engine warm up quicker (I run one even in So Cal).

[Flieger]

You got more interior than me, though.

my 911S - a set on Flickr

Mechanical - a set on Flickr

Funny, I always preferred Mary Anne, but in this case Ginger is more appealing. I have a BMW, too, BTW. 1983 E21 320i.

[wolfrennen]

Yep, my car takes forever to warm up on cool days without an oil thermostat. The builder set up the car for hot lapping I guess LOL.

Originally Posted by Flieger

Sounds a lot like my car. I would want a thermostat, though, to make the engine warm up quicker (I run one even in So Cal).