just curious. Ls/VTEC vs. B18C

[97 Ex/SiR]

now that i think about it.. Ls/VTEC vs. B18C, whats the better choice for performance.. why? i assumed it was pretty much the same engine when you were through with it (the ls/vtec).
-Dane

[97 Ex/SiR]

nobody knows!!?? what is this, whats going on here??

[dubcac]

A stock B18C will be better than a "stock" LSVTEC. Unless you spend the time and money to correctly build the LSVTEC, it won't be as reliable as a B18C.

[97 Ex/SiR]

i see. that makes sence, thank you sir.

[imported_Vash The Stampede]

b20 is gonna give you .2 liters more displacement as well,

[imported_camelian]

MORE TORQUE =D

problem for me is: more TQ + 185 tires + light car = peel out
i find it really easy to peel out in 2nd =P. just gotta find the "sweet spot"

[mikebreezy]

the LS motor has a 1.54 rod to stroke ratio, meaning the length of the stroke, divided by the length of the connecting rod vs the b18c's 1.58. the higher the number the better. indy cars are around 2:1, a b16 has a 1.74 r/s ratio which is why they rev to 8000 rpm like its a walk in the park. b16's are hondas highest r/s ratio that im aware of. next best thing is a b17.

think of this. if a motor has a long stroke then the crankshaft rod journal has to be far from the centerline of the crankshaft,, basically the crank is big,, the large end of the rod travels in a larger circle. moving slower and slanting over farther in the cylinder bore. if the stroke was short, the rod would follow a small circle and slant to a much lesser degree in relation to horizontal.. how to say it... the rod is vertical at top and bottom dead center.. but begins to move toward horizontal at 3 o'clock and 9 o'clock or 90 and 270 degrees.
so if the rod were to lay more horizontal that vertical and then have the crankshaft trying to drive it up the bore, wouldnt that put a lot of stress on the length of the rod beam and on the piston being shoved sideways into the cylinder sleeve? ofcoarse it would. this is why LS motors should not have vtec heads on them.

the LS has the longest stroke of any B motor,, the b20 is the same. the ls makes more HP but the b20 should stand to make more torque due to larger displacement. at any rate, neither were intended to have vtec heads on them by honda, no matter how good it works. if youve never been in a dohc vtec, b16 especially, they dont make power until they are in the 5200-8100 rpm range with stock cams. the LS and B20 motors werent meant to see much time over 6800-7000. they wre designed to pull heavier vehicles with their low end torque which comes from that very same thing that limits rpm.... a larger crankshaft circumference, or stroke basically.

when you see pros running ls and b20/vtecs, especially with big boost, they have ductile iron sleeved blocks, shotpeened and knife edged cranks, expensive aftermarket rods and pistons etc. a stock LS motor wont stand up to all the abuse for long.


a gsr will because the rods have a higher chromium content and a better rod to stroke ratio. also the head to get is the gsr over b16 and type R because it is a pentproof design, meaning it has two square indents on the sides of the combustion chamber that squish unburnt fuel away from the cylinder walls and help prevent detonation.

[imported_comutek]

wow, a lot of wrong info in this post.

[dubcac]

The rod/stroke ratio of an LS/B20 vs a GSR/ITR is not much different. I agree, the proper way to run an LS or B20 with a VTEC head is with a proper engine build. However, they can be spun to 8000 rpm with simply ARP rod bolts. The weak links in the bottom ends are not the rods, nor the r/s ratio, it's the rod bolts. They tend to stretch under high rpm stresses. I've seen LSVTEC's with shotpeened LS rods and ARP bolts spin to 9500 rpm regularly, and are still fine with use of a crankshaft girdle.

[imported_oyy0]

Originally posted by comutek@Dec 2 2003, 07:58 PM
wow, a lot of wrong info in this post.