The 2nd option is the best option but like you said it will cost alot more money and bit alot more work!

That's why it is cheaper and easier to do the first option plus it still works regardless.

But if money was no object i would do the second all day long bro!

 

Yes , you are right , playing with rods Length and crankshaft effect the performance/ TQ very well !
But it costs more !!

If anybody may answer ,

Option 1 , running big bore pistons 4.1L
Option 2 , running diffrent rods Length and diffrent
Crankshaft to reach 4.1L !!

both setups share all the same parts , turbo etc etc.. !

Which one better ?
How much HP will be diffrence ?
Which one remain daily drive ?

 

Again i would say option 2 will be better in all areas apart from your pocket.

Technically i have no experience with these kits so i cannot answer how much hp difference etc etc but i would assume a good gain throughout the revs and much more drivability.

Where Emre when you need him

 

The big expense on option 2 is the crank mod. The rods it should be even cheaper than sleeves and pistons.

So how much can you gain from just crank and how much with just rods?

What will you do to obtain the 4.6cc?

 

I'm sure 4.6 ltr will require alot of machining and the crank, rods, pistons and liner combination.

You are probably doing the same as 4.1ltr but achieving the extra 0.4ltr from the longer rods and a different crank.

I am sure someone will confirm this though as it would be nice to know.

 

Emre, thanks for all the great info you are sharing. It seems that 4.1 liter and 3.8 liter share the same wall 2mm wall thickness. Would the machining weaken the case/water jackets for the 4.1 liter liners?

 

What transmission upgrades?

 

I do not believe it is possible to obtain 4.6L with the current Porsche deck height and timing chain. At one time Koro made larger cases which could derive 5.0L, however to my knowledge they were not designed for turbo duty.

If anyone is interested in the formula to determine a motor's displacement, here it is. Post #2881.

https://www.6speedonline.com/forums/...ml#post2239168

 

Don't get your motor to out of square (Bore/Stroke). Option #1 without doing the math appears to be to much out of square. Torque will be the difference you notice with stroke increase. #3 This will be more a function of your turbo choice and tune.

Point of caution, with a 80.4 mm stroke an nice rod length to keep ideal piston/rod ratio's would be about 131 mm. To get to just under 130 mm's is very expensive. To get above this number requires heightening the deck height which requires a very special timing chain. Out of this world cost wise.

Again without doing the math ..... 80.4 stroke and 102 mm pistons would be very nice and a lot easier on your pocket book.

 

^^ good advice.