"...are we off topic or what? "
NOPE thats the idea discuss engines more.
i'm getting sick of people asking basic "whats best for me" so i thought i'd get this going for people to actually talk about them and what they like as opposed to having to try and tailor your answer for someone buying an engine.
that way if someone does ask anyone can post this and then let them think again before asking a question that has SOO many answers and SOO much info.
Totally agree, I like to see this sort of discussion that makes people think about how and why stuff works, but it seems all anyone wants now is to be spoon fed what parts they should buy and then told how much power it will make. It seems like so little thought goes in to so many of the parts people buy for Hondas, and it's sad because if you do a little research there is so much you can learn about our cars.
Makes me think that a b20 with a stroke of 89mm round a track at 8k+ Rpm is not goint to last that long
.
True true, although really the dimensions are not that different to the B18C, you have 89mm to 87.2mm, and a 137mm rod to the B18s 137.9mm.
Compared to that piston speed I mentioned earlier of 22.61ms, the B20 is at 23.08ms at 8000rpm, so nowhere the difference between the B16 and the B18. Certainly not going to stand up to the kind of prolonged high RPM abuse that the B16 will do, but then with the extra torque you shouldn't really be needing to rev that high anyway.
(slightly off topic but relevant)
But then the clio 2L 16v F4R flagship engine that seems to take some fair beatings in rallying and track events from what i have heard, which rev to around 8k. And they have a stroke of 93mm
. Which is alot more than a B20 at 89mm and even further from the b16b at 77.4mm.
Soo hopefully i should be safe.
Stroke only tells you so much, the length of the rod does have a reasonable effect on engine performance (jury is out on how much exactly), if that 93mm stroke had a long enough rod then it could easy rev that high and remain reliable as you keep the rod angle down and so the piston side thrust is reduced.
The length of the rod not only affects reliability, but also the engine breathing at various engine speeds. A long stroke, short rod (low R/S ratio) motor pulls the piston away from top dead centre quicker than than a short stroke long rod (high R/S) motor. At low RPM, this works to pull a higher vacuum in the early part of the intake stroke, and so increases volumetric efficiency (and so torque) at low speeds. This also works against the high R/S engine in that it does not breath very well at low RPM, making it feel gutless.
Speed the engine up and it starts to change hands, the low R/S ratio doesn't give enough time to effectively fill the cylinders as the piston moves away too quickly, where the high RS engine is giveing the charge more time to completely fill the cylinders, so you get increased torque at higher RPM.
This same effect happens on the power stroke, with the piston moving away from TDC quicker in the low RS engine, it gives less time to fully release the combustion energy into the piston, and in extreme cases it can almost reach the point of outrunning the flame front resulting in less torque, at this point the engine has well and truely run out of breath. In comparison the high RS ratio is able to hold a high pressure for more of the stoke and as a result it can hold power much further up the revs. Since power is torque multiplied by revs, we can see how the little B16B is able to produce such high power with so little torque.
I have heard many people state that while the B18C feels like the more powerful engine all round (and it is), it just doesn't seem to rev as well as the B16B. Considering the engines are pretty much identical in all other aspects, I imagine these breathing characteristics as a result of the bottom end geometry are largely the cause of the difference. The B18C with its 1.54 RS is breathing more efficiently at lower RPM and the B16B at 1.84RS is breathing more efficiently at higher RPM.
I am not all that familiar with the K and F series engines, but the same principals apply.
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