B20b vs K20a

**tinkerbell** · 18-07-2005 11:04 AM

hence why the two cost curves intersect once you get to about 150kW...

**Steer^Gimic** · 18-07-2005 11:37 AM

this is quite a useless argument if you think about it. if you genuinely chasing big hp then you are more then prepared to fork out, in which i totally agree with eg5, go k20a.
but bringin me back to my last point, your average joe, shit talker ,OH member who will do nothing but I/H/E in there car stick with B.

and pgclee, stop watching Best Motoring DVD's your talking too much rubbish

**aaronng** · 18-07-2005 01:39 PM

Are you making a high revving engine? To stay at the higher revs for extended duration, a R/S ratio closest to 1.75 will have the least lateral stress on the cylinder walls.

B16a = 1.75
B20b = 1.54
K20a = 1.62

So the k20a will be more reliable at high revs than the B20b, but won't be as free revving as the legendary B16a.

**tinkerbell** · 18-07-2005 01:46 PM

Originally Posted by aaronng

a R/S ratio closest to 1.75 will have the least lateral stress on the cylinder walls.

might need to do some more reading to actually get this staement 100% correct.

ie what about a 1.86:1 r/s ratio?

will that stress the cylinder walls more too? or not?

**Tony** · 18-07-2005 01:50 PM

If you want to go high rev, try 2:1 r/s ratio, someone is doing this in the US, and they are planning to rev the motor to 11,000rpm +, it's a K24 block with K20 crank btw..

**tinkerbell** · 18-07-2005 02:00 PM

talk about a torqueless gutless daily driver?!!!

i doubt it would be a "daily" with that sort of combination though... that is basically F1 car r/s ratios...

**Tony** · 18-07-2005 02:01 PM

The motor was designed for camshaft testing. They want to see if cam will still make power at that rev range.

**aaronng** · 18-07-2005 03:16 PM

Originally Posted by tinkerbell

might need to do some more reading to actually get this staement 100% correct.

ie what about a 1.86:1 r/s ratio?

will that stress the cylinder walls more too? or not?

Ooops, you got me there. The larger the number, the less stress. 1.86 is less stressing than 1.75. My error. But I think the reason why 1.75 is ideal is because as you go to larger R/S ratios, the engines becomes an extremely short stroker (unless you have a very tall engine block to accomodate the long rod), and the engine becomes lazy to rev at lower rpms.

**aaronng** · 18-07-2005 03:18 PM

Originally Posted by tinkerbell

talk about a torqueless gutless daily driver?!!!

i doubt it would be a "daily" with that sort of combination though... that is basically F1 car r/s ratios...

I've read about that one. Was it run at the original 2.4L or 2.2 or 2.0L? I remember they used a K20 head as well. If so, then there would be enough space in the tall block to accomodate a longer rod, while maintaining the stroke length of the K20.