Opinions - B18CR Bottom End with Alaniz head

[fatboyz39]

Stick to a single manifold.

[ewendc2r]

Stick to a single manifold.

ROFL -- I can't win. Figured this way I could pick up some more mid-range without cracking the block. Given stock cams run out of puff at about 8200-8400rpm I also thought that the normal restriction from ITB's at top end would be a non-issue?

Well -- At least there is another thread that may help someone else in the future lol.

Appreciate all your inputs --- Very much apprecaited.

[Chr1s]

I don't know what your aim for this build is, or what you will be using it for. I havn't taken the time to go back through posts to see what its about either, but going by the "crazy" comment you said earlier I assume you want a mental B series.

Internal combustion motors unfortunately are not as simple as they may seem. You need to have a very sound understanding of fluid/thermodynamics to even get anywhere before looking at the material and form of the components. What i'm saying is, what good is it knowing to run forged internals when you can't get the motor to flow the right way?

I already can see this leading to a kind of "headcase" of a build when I see that you want to use off the shelf parts. I don't like to look through a catalogue and pick parts out.

Since you asked about intakes, I beleive the intake should be designed around the camshaft, if you take some time and look at how the intake operates, beleive it or not, it's more than 4 pipes welded to a bigger tube; you will see that the camshaft has a great effect on the intake. So yes, if you want to get the most out of this motor, toda ITB's are NOT going to cut it, you will need a custom setup.

The way custom manifolds are made to spec is by some fairly complicated mathematics. It's very stringent on sizing, shape, velocities and flow to name a few. Helmholtz resonant frequency is a name you will learn to recognise. Not just in combustion engines, but also in audio speaker boxes for example!

To break it down nice and easy, the intake works on pressure waves, if it's easier for you to understand, picture it in a plumbing sense, since we use water to compare flow of air as a general rule of thumb at atmospheric pressures. The water comes down the runner, valve shuts, hits the back of the valve and a "wave" travels back up the intake runner and then hits the back of the plenum, this wave occurs again and guess what? travels back down the runner. Now this occurs many many many many times a second and at different rpm's as the RPM increase, so its not a linear function that we generalise on, but! We learnt in physics back in school that when two waves of the same phase occur at the same time, they join to create a superposition of the two. This generally increases the amplitude of the wave but keeps the frequency the same, so if you're tuning for x frequency @ x rpm, by tuning the timing when the valve will open with the fresh air charge and resonant frequency inside the current chamber you can create a ram air effect which is another name for "supercharging" the air into the cylinder. This is how intakes are made, now to get the optimum superpositioning of the one frequency charge you need a runner length that is impossible for the rpm range we deal with. We half the length of the runners and inturn we half the strength of the "superpositioning effect", we divide by 3, and we divide the strength by 3 and so forth. This is why the B18C2 has a dual runner setup, one for peak torque at high RPM and one for peak torque at low RPM.

All in all, I would go for a properly designed ITB setup with a plenum which is tapered to maintain velocity in the plenum for the further cylinder and of course, a proper high pressure zone cold air feed.

It's very very complicated, I will try and explain better later tonight, I'm just in a rush typing this so if any errors are in there, you know why .

Hope it helps you understand a little better!