I have a simple question: what does merely increasing the bore size on a motor do? I am getting a B18C (early model) and am thinking about boring/sleeving it to a 2.0L, in preparation for a turbo later. I plan on driving the car with the bore/sleeve job and wonder what kind of horsepower, torque, compression, etc I will be looking at?

 

Well, to get really really technical, merely increasing the bore size will make your car stop running. Now, if you get some pistons that FIT the new bore size, (depending on the dome displacement) you'll come out with a higher displacement and a lower compression ratio. However, the compression ratio is going to vary depending on which pistons you get, so that's really up to you. If you're driving a boosted, sleeved C1 with low-comp pistons and a fair amount of requisite head work, you could be making 400+ whp and somewhere in the neighborhood of 275+ ft/lbs without too much trouble.

 

Is the engine gonna be less stable or anything due to the increased bore?

 

No not really. I see the myth "B20 cyl walls are to thin to do anything with" all I can say to that is cough*bs*cough. A b20 that is boosted, supercharged, done n/a, or ran with a properly setup cr/vtec are no more problematic than a b18, b16, or d16. What has happened is you have had a few people do stuff like cr/vtec, turbo, supercharger, or n/a setups with the b20 and they do not take into account that the rod/stroke ratio is made for low and mid-range tq not high rpm hp.

 

...smartass

 

Well, while they are only a couple mm thinner, I believe they are also taller, which sure doesn't make them any more stable.

 

all engines of the same series have the same bore size right?

 

No. All B-series motors use the 81mm bore, except the B20B/Z, which uses an 84 mm (hence the thinner sleeves). Likewise, the K20 and K24, F20/22 and F23 motors have different bores.

 

also, increasing the bore unshrouds the valves allowing a better flow pattern going into the engine, making some great gains. thats the reason F1 cars have such a big bore and a short stroke. to get the cylinder walls as far away from the valves as possible. and the short stoke helps with the insane redlines as well.