[ronmunroe]

I have an oportunity to get my hands on a b16 a1 head!
any opinions on this for an ls/vtec or am I better off to wait? Do I need the intake/exhaust manifold or will mine suffice!

 

[JDIAZ]

u need a intake/exhaust manifolds and ecu plus a shop that with machine the head to fit on the b18b block it might sound easy but there is alot of work that goes in to it.......do a seach they have some threads on ls/vtec

 

[MichaelDelaney]

get the head, ecu, vtec harness. buy an itr im instead.

 

[Jacksont001]

mike why the itr IM rather than the b16a? I know the plenum is smaller but is that the only reason? sure that might be a significant one.

 

[MichaelDelaney]

b16a im is made for a 1.6L high rod ratio motor that fills it's cylinder differently from a 1.8 L low rod ratio teg. wayyyyyyy tooo small ...it'll choke your ls/vtec big time!

 

[Jacksont001]

good to know, based on the other thread we had Here

 

[MichaelDelaney]

yeah I find that I repeat myself a lot here to be nice. thanks for linking that thread up. it certainly makes my life a lot easier and I wish more experienced members (experienced being the key word here) would do the same and chime in their real world knowledge. I certainly do not want to monopolise the thinking here. I just throw up the ideas from my experience based on some engineering basics.

just remember that the b16a is a different motor with different needs than a teg motor. It's gutless below 6000 rpm and needs flow velocity mods to gain back power below 6000 rpm. So the IM is small to get more flow velocity and is sized for a 1.6L. you don't just willy nilly trade parts. the b16a head is a very good head but it should be ported for the teg's rod ratio...it's port volumes are too small for a 1.8L 1.5-ish r/s engine...even an LS/VTEC engine.

 

[Jacksont001]

hmm, Mike I know you have addressed this before. in all your articles. port sizes are designed flow a certain volume at a certain speed. what speed would this be? the reason I ask is so we can develop a primer based on swept volume vs. rate of fill over time(based on piston speed) + total time valves are open (based on cam profile) so they can get an Idea of the flow requirements from start to finish and the size(quantity/quality/velocity) requirements for each step along the way.

 

[Jacksont001]

Nah screw that let em figure it out themselves

 

[MichaelDelaney]

hmm, Mike I know you have addressed this before. in all your articles. port sizes are designed flow a certain volume at a certain speed. what speed would this be? the reason I ask is so we can develop a primer based on swept volume vs. rate of fill over time(based on piston speed) + total time valves are open (based on cam profile) so they can get an Idea of the flow requirements from start to finish and the size(quantity/quality/velocity) requirements for each step along the way.

the flowbench really dictates the minimum flow capacity requirements only. The cam redline pretty much sets the flow need initially. Then it's more of the porter's experience with different r/s ratios and engines (here's where the science ends and the black art begins) which determines how and where they change the shape of the port...the overall port size can also be tested empirically using pressure manometers and pitot tubes which measure flow speed for 1 stream of the many parallel streams or layers in laminar flow. I believe I covered the equation for redline determinants of cfm and vacuum based flow equations over on the "Gotten Head Lately?" article over at Hondavision.com's Tech Review article section and I also state the Bernoulli equation using the measurements off the pressure manometers and pitot tubes placed in a conduit (head port).

You see many textbooks state that the standard exhaust flow rates should be on average 70% (60-85% range) of the intake flow rate on a flowbench. The problem is flow travels forwards AND BACKWARDS. So reversion flow measurement particularly for valve seat work is very important or as important as forward flow rate. The top cut and bottom angles dictate the reversion capability of a head at low intake valve lifts below 30-33% max lift. once you get into N2O and FI, the exhaust flow rates relative to the intake flow rates go up on the order of exhaust flow should be 110% of intake flow....not 70%. So headporting job and the seat angles are different for FI/N2O vs N/A...and is also cam and displacement dependent. A headporting shop which just asks for your address and VISA cars number at the start only will be doing a generic port job and not making the head fit your needs...that's when you say: No Thank You, I'm shopping elsewhere.

 

[Jacksont001]

slightly veering off, could you reduce reversion flow back into the IM by "stepping" the transition from IM to Intake Port by say 0.5 mm or so all around? I.E the intake ports are slightly larger but the transition is blended, which minimizes the loss of velocity, but still acts as an anti-reversion device.

 

[MichaelDelaney]

yes definitely...placing an increased step at the head port after the IM does have antireversion effects, just like the at the header & exhaust. It shows that portmatching the IM runner port to the head port may not be the best way to go as people originally thought. going from a smaller IM port diameter to a larger head port diameter would be better. This is true as long as the head port size does not get too big when you add the step. Usually people do not port the head intake port larger than the manifold gasket port size anyway.