Cast iron bores? and why then are b20 weak

[Dxs]

Just wondering, if the typical honda engine has cast iron bores? or some other kind of bore? is it possible for them to rust if left exposed


if so, what makes the b20 weak. is it that these cast iron bores are thinned to make the 2L capacity? hence Barton sleeves etc are used, because these are a thicker iron bore?

[ZeForce]

B20b 84mm sleeve
http://a825.ac-images.myspacecdn.com/images01/34/l_4f822a6c5a74d2477e421d420467a700.jpg

B18/B16 81mm sleeve
http://www.c-speedracing.com/howto/nabuild/pics/dsc00017j.jpg

[Dxs]

thanks for the pics
so the b20 is a 1 piece setup?

[Limbo]

you've lost me on the pictures can you please explain for the dumb one?

[Dxs]

see how the cylinder walls for around a couple of mm is a different colour to block colour


i guess they are cast iron
where as the rest of the block is some alloy


b20's are bored out.. so those cast iron sleeves i guess are thin, well especially where they now touch each other.. see how there is a line between them (vague though).

here is a nice article though
http://dwolsten.tripod.com/articles/jan96a.html


anyone else have interesting info?

[ZeForce]

see how the cylinder walls for around a couple of mm is a different colour to block colour


i guess they are cast iron
where as the rest of the block is some alloy


b20's are bored out.. so those cast iron sleeves i guess are thin, well especially where they now touch each other.. see how there is a line between them (vague though).

here is a nice article though
http://dwolsten.tripod.com/articles/jan96a.html


anyone else have interesting info?

Good article :thumbsup:

The pic below shows where the B20b sleeve tends to crack, from what I understand this was from a boosted B20VTEC
http://www.tiora.net/~jay/pix/race-car/motor-build/before-sleeves/DSC00041.JPG

[DLO01]

Yeh, B20, wall from cylinder to cylinder looks thin.

[trism]

it is

it has weak cylinder walls

hence why so many companies sell block guards for them ;)

[thepope1986]

that last picture looks like that cylinder has been suffering pistion slap

[mocchi]

so the problem is because its thin? not because of temperature difference between cylinders that cause crack?


it is

it has weak cylinder walls

hence why so many companies sell block guards for them ;)

[TODA AU]

I'm pointing the finger at torsion & torsional vibration as the culprit.

Things that can be utilised to minimise or negate it's effect are:
5 Point main girdle,
Fluidampr or ATI damper,
Reducing the mass of the rotating assembly to increase harmonic frequency
Balanced rotating assembly
& finally, use of quality aftermarket sleeves.

[TODA AU]

hence why so many companies sell block guards for them ;)

IMO block guards for a stock block are just marketing hype...
Someone made one 1st, it sold well & then everyone coppied the idea.
Not to make anyone's engine better,
But to pump something out quickly & easily to make a dollar.

Bit like the Teflon intake manifold gaskets...
More smoke & mirrors

[mocchi]

IMO block guards for a stock block are just marketing hype...
Someone made one 1st, it sold well & then everyone coppied the idea.
Not to make anyone's engine better,
But to pump something out quickly & easily to make a dollar.

Bit like the Teflon intake manifold gaskets...
More smoke & mirrors

posting would work better?

[TODA AU]

posting would work better?

No, not really.

[JohnL]

Just wondering, if the typical honda engine has cast iron bores? or some other kind of bore? is it possible for them to rust if left exposed

If it's cast iron then it can rust.


if so, what makes the b20 weak. is it that these cast iron bores are thinned to make the 2L capacity? hence Barton sleeves etc are used, because these are a thicker iron bore?

My bet is that it's unequal heat distribution around the cylinders. Ideally we want the water jacket to fully wrap around each cylinder to ensure that the cylinder has an equal temp at all points around the circumference (keeps the bore perfectly round at differing temps and reduces expansion / contraction stresses).

However, this means that extra space is required around each cylinder, and this results in a physically longer engine which is problematic in an engine bay of finite width (i.e. longer and heavier engine that is more difficult to package into the engine bay). To keep the engine 'short', designers often 'siamese' the cylinders, i.e. each cylinder butts up against the next cylinder with no water jacket between them (engineering is the 'art of compromise'...).

Heat must then conduct from the areas directly between the bores along a longer path to the water jacket, and as a result the area between the bores tends to be hotter than the areas directly adjacent to the water jacket.

Note on the larger bore engine that the cast iron liners are not separated by aluminium, whereas on the smaller bore motor they are (and this aluminium is contiguous with the aluminium of the block casting). Aluminium has a much better heat conductivity than does cast iron, so the aluminium between the bores (on the smaller bore engine) provides a superior heat path for heat to escape from the metal that is directly between the bores, and on the larger engine the heat path is inferior because it is cast iron. This is compounded by the bigger bore engine also having less thickness of metal between the cylinders, further limiting the effectiveness of the heat pathway to the water jacket.

As a result the smaller CC engine will have a more consistant temp around the circumference of each cylinder (it still won't be fully consistant around the cylinders because the WJ is non existant between the cylinders), but the larger CC engine will run significantly hotter between the bores and cooler nearer the water jacket, and there will also be a more abrupt difference in liner temp near where the aluminium begins, right where that crack is...

[peejayy]

thanks for the info guys, been quite a great technical read so far.

Does anyone have pics of engines that do have a water-jacket arond each cylinder? Does Honda produce any of these engines???

[JohnL]

Does anyone have pics of engines that do have a water-jacket arond each cylinder? Does Honda produce any of these engines???

I can't direct you to any pic of this specifically, but engines intended for north / south installations are likely to have less constraint on engine length and thus more likely than east / west engines to have non siamesed cylinders.

If the block is a closed deck design then you won't see much difference except that cylinders will be more widely spaced. If an open deck then you'll see that each sleeve stands alone with a space between each cylinder that is a continuation of the water jacket. Other differences might be that the sleeves might be 'wet' sleeves where the cast iron is directly exposed to the water jacket, rather than 'dry' sleeves where the cast iron is surrounded by aluminium (as with the engines pictured in this thread).

If you have the choice when designing an engine then you'd go for non siamesed cylinders every time. Not only is this going to be a more reliable design, the cylinders will remain rounder as they heat up which will mean more even ring tension and better ring seal. The differences may not be great, but the siamesed design is definitely a compromise.

With the two engines in the photos, if I were intending to substantially supercharge then for reliability reasons I'd pick the smaller bore engine unless there were other compelling reasons not to.

[nd55]

> Does anyone have pics of engines that do have a water-jacket arond
> each cylinder?
> Does Honda produce any of these engines???

The B20 is the exception in the Honda lineup AFAIK. All other Honda engines have individual cylinder bore liners.

Chevrolet 400 cu. in. small blocks used the same technique. It's called a siamesed bore.
I believe they had the same issues in hi-perf. applications.

> it has weak cylinder walls
and
> b20's are bored out.. so those cast iron sleeves i guess are thin

I'd wage that the bore liner is the same thickness as other Honda engines, and the problem is more in modified output applications which generate lots more heat.

It's ALWAYS the material between the two bores that cracks.
This points to a problem with poor cooling between the bores, rather than strength, to me.
Said another way, the thickest/strongest part of the liner cracks, or at least the metal right next to it.

> To keep the engine 'short', designers often 'siamese' the cylinders

nah, Honda got lazy and wanted to use the B16/B18 production line to produce a 2.0litre engine, hence the shoe horning of bigger bores in the same bore spacing of a b16.

> I'm pointing the finger at torsion & torsional vibration as the culprit.

If I didn't know Toda's background I'd normally discount this.
Very interesting.

Nick.

[Benson]

If you got the money then sleeve it.

Stock Bore is perfect for most application, unless you are going all out, then thats a different story

[JohnL]

nah, Honda got lazy and wanted to use the B16/B18 production line to produce a 2.0litre engine, hence the shoe horning of bigger bores in the same bore spacing of a b16. Nick.

Nick, all the engines pictured in this thread have siamesed cylinders. The difference is in the thickness of the solid metal between each bore, and whether or not there is also aluminium between the bores or only cast iron. The term 'siamesed' is a little confusing because it implies two cylinders joined, whereas in reality it can be all of them.

Some 4 cylinder engines have two pairs of siamesed cylinders, e.g. some of the BMC A series engines used in Minis, Sprites, Midgets etc. where the water jacket existed between cylinder 2 and 3, but not betwen 1 and 2 or 3 and 4. When they increased the A series engine capacity up to 1275cc for the Cooper S they changed the bore spacing and thus all four cylinders became 'siamesed' with no WJ between any cylinders.

[jdm_b16a]

The B20 block is weak because of the poor bore/stroke ratio. The cylinder walls need to be stabilised/reinforced under heavy load hence the need for things like Darton sleeves. Standard engines are OK but non-NA applications place too much stress on the bore/stroke ratio causing the walls to crack between cylinders as in the above photo.

Peter

[Benson]

Can you explain why stroke has any affect on the weakness of the block.. Bore yes as its 84mm compare to 81mm from the the B18c and B16a. So its losing 3mm on material already, but stroke????

[mocchi]

he's talking about how long stroke generate more friction between piston and cylinder wall.

[nd55]

> all the engines pictured in this thread have siamesed cylinders.

B18 is siamesed too? Learn something everyday.

> The B20 block is weak because of the poor bore/stroke ratio.

D16 has a 75mm bore, 90mm stroke.

No cylinder liner issues till 400Hp.

I think you mean con rod length to stroke ratio.

Even so, D16's are poor here as well, and still no issues.

D16: 137mm rod length, 90mm stroke.

That's a 1.52 R/s ratio.

B18C1: 137.9mm rods, 87.2mm stroke. 1.58:1 ratio.

B20 137mm rods, 89mm stroke. 1.54 R/s ratio. No worse than the D16.


I assumed the siamesed bore was the problem. But it seems better people (toda) than me are pointing to other issues.
http://ftlracing.com/tech/engine/dynamiccr.html

Nick.

[ZeForce]

> all the engines pictured in this thread have siamesed cylinders.

B18 is siamesed too? Learn something everyday.

> The B20 block is weak because of the poor bore/stroke ratio.

D16 has a 75mm bore, 90mm stroke.

No cylinder liner issues till 400Hp.

I think you mean con rod length to stroke ratio.

Even so, D16's are poor here as well, and still no issues.

D16: 137mm rod length, 90mm stroke.

That's a 1.52 R/s ratio.

B18C1: 137.9mm rods, 87.2mm stroke. 1.58:1 ratio.

B20 137mm rods, 89mm stroke. 1.54 R/s ratio. No worse than the D16.


I assumed the siamesed bore was the problem. But it seems better people (toda) than me are pointing to other issues.
http://ftlracing.com/tech/engine/dynamiccr.html

Nick.

Good point, but the small bore of the D series engine prevents the rod angle from becoming too severe. The larger bore of the B20 with its low rod/stroke ratio means there are larger sidewall forces and likelihood of sleeve cracking at high rpms

[JohnL]

I still think it's:

The lack of WJ between the bores
The thinness of the metal between the bores
That with the larger bore engine the metal between the bores is cast iron only with no 'sandwiched' aluminium (which would improve 'between bore' heat conductivity to the WJ, as there is with the smaller bore engine).


All this means significantly unequal temperatures around each bore, and, because the thinner metal between each bore is a smaller heat sink this area of each bore is also subject to greater temp changes with each induction and combustion cycle (a rapid cycle of cooling / heating / cooling ... ).

This means an increase in thermal stress between the bores (with the larger bore engine). Chronic unequal heating of contiguous metal (especially castings) is a classic recipe for eventual cracking, and the higher the temperatures and temperature fuctuations you have in the cylinders (i.e. the harder you supercharge the engine), the more of a problem it will tend to be.