Quote:

I have to agree with this statement 100%
The center to center distance [main journal to crankpin journal] is the 'throw' which is half of the stroke measurement.

When the crankpin journal is offset ground the center of the crankpin is moved outward [or inward as the case may be] by half of the reduction in diameter.

Quote:

L series, whats the fun in that?
A series is small, compact and sexy! The L is opposite, not to mention heavy!.
As for 10X more reliability, maybe 25% stronger but not as durable and reliable
as an A, L series smoke & leak oil faster than most teenagers.

Why not run an L13 with e15e rods, 67.6mm stroke, de-sleeved to 81mm bores for 1187cc and Z18ET head all manifolds there and 350hp possible since Maddat got 400+ on methanold with his turbo l13. When it comes to crazy A series ideas funny you almost take the cake.

Quote D
"Simon maybe for a race motor :) but for the street capacity rules
with shorter rods and normal rpm. Not that I wouldnt mind a turbo
a12 that spins easily to 9500rpm but thats a nasty thing."

I agree that RPM`s should be kept sensible for a road engine. If capacity rules on the street, why would you bother trying to get "1900+cc" from an A series when you could just put a stock L20 in and get more capacity and ten times the reliability?

EDIT, Offset grinding the crank 5mm WILL increase the stroke by 10mm.
If you are talking about reducing the journal size by 5mm to to allow an offset grind without adding material, the ofset grind is only 2.5mm.

Simon

offset grinding the crankpin 5mm will give you 5mm extra.
The crank mains are a different story.

Simon maybe for a race motor :) but for the street capacity rules
with shorter rods and normal rpm. Not that I wouldnt mind a turbo
a12 that spins easily to 9500rpm but thats a nasty thing.

Quote:

Offset grinding the crank by 5mm will actually give you 10mm extra throw/stroke..

If you want performance and a high rod/stroke ratio. Keeping it simple you could use an A12 crank in an A14 block with a longer rod and turbo..

Presto!!

All this talk of rod length and Rod/stroke ratios has to be taken in context with the application.

At higher rpms the pistons can travel away from the combustion before good cylinder pressure can build. This might be a case for a longer rod? or would you use a faster burning fuel? Does the engine have programable ignition timing to allow combustion to start earlier once the engine is past peak torque?
Will this engine then have detonation issues at peak torque?

With forced indution engines, they have much higher AVERAGE cylinder pressure (the peak is not usually much higher) This means that the pressure applied to the crank continues for many more degrees of crank revolution. This senario would surely call for longer rods? But the piston will dwell at TDC for longer! Will this make the engine detonation prone?

To work out what rod length to use i would think you would have to know the cylinder pressure curve on the combustion stroke(most engines produce peak cyl pressure between 10 and 20 degs. after TDC). Then time this with getting the mechanical advantage right with the Rod/Stoke ratio.
This would cost hundreds of hours and many thousands of dollars in development time. Out of the realms of us mortals and best left to Profesional race teams and the OEM`s.
Yes, sure, copy the best. But be sure you know why they have done what they did.

I believe there are many things for us to be more concerned about.

The guy in Kyneton with the masivly stroked 265 C.I. Hemi(now well over 5 Lts) is still about 80 HP short of another mate with a standard stroke 265. Yes its differant and its a good conversation starter (I love it too). But there is a lot more important things to getting peformance than stroke and rod/sroke ratios.

1hp more!!! yes its worth a

Seriously displacement is the goal, as long as the rod stroke ratio is above
1.522 everything should be good, alas a rebuild sooner than later if not using
teflon coated skirts. But re-sleeving is only a few hundred more at worst if
the sleeves dont have much left for honing.

It must be taken into account that with smaller crankpins and rod journal from e15 or
other smaller journals eg, hayabusa 38mm the clearance is possible.

The crank on the other hand will need a fair bit of work if going over 87mm

82mm stroke - 45mm crankpins vs 87mm stroke - 40mm crankpins
The 5mm in stroke is made up with the 5mm smaller crankpins.

81mm Pistons from 4afe with 18mm pin size or Mitsubishi 4G93 DOHC/Turbo pistons 19mm pin.
The 4age 86-87 pistons are almost flat tops and 18mm pin size later ones 20mm pin.

edited:
81mm x 84.5mm = 1714cc (e series rods)
81mm x 85.5mm = 1762cc (hayabusa rods)
83mm x 88mm = 1905cc (welded/offset ground)
81mm x 70mm = 1443cc (A12a rods)
81mm x 77mm = 1587cc (A12a rods)
81.5mm x 77mm = 1607cc (" " ")
This last 2 combos would be preferred over a 1608cc 79mm thin bore a15.
A12 revs with almost the same capacity suitable for U16SS class

Now DD how about you be in charge of the a12a conrod group buy :)

D's goal is not to increase displacement, but rather to achieve rod length nirvana. I reckon you could improve it 85 HP in the A14 to as much as 86 HP.

All this talk of longer rods is all well & good, but the basic dimentions of the A series cylinder block will tend to limit the practical maximum displacement to somewhere close to 1650cc.

The center to center bore spacing of numbers 1 & 2 along with 3 & 4 cylinders means that even with offset bores, 80mm would seem to be a practical maximum bore size, & even that is pushing your luck.

Again, the 82mm stroke crank in the A15 requires a factory modified design of oil pan to clear the rods on one side. It won't take much more before it becomes necessary to start grinding the crankcase walls & the oil pan rails & the workload, along with the cost starts to rise exponentially.

A LOT of work & $$$ for a relatively small gain.
It's actually geting to the point where it may even be a proposition to cast a new block with a few 'improvements' included.

Hell, with a clean sheet of paper a new block could accomodate a 90mm stroke, an 83mm bore, a deck height to rival a multi story building [well, perhaps not that much] & a twin cam head from a current or recent production engine.

With a new block, head, crank & rods it stops being an A series engine doesn't it?

Who'se going to be the first to volunteer to pay for the R&D on that.