The graph shows the air flow in CFM that can flow into a cylinder when the valve is at a certain postion above it's seat. Our low cams have ~ 7.25 mm (.29 inches) of valve lift. The VV or big cam has 11.2 mm of lift (.44 inches). If you look at the chart first posted, you can see that at the lifts being utilized, the head on our cars does quite well. It starts to lose out to the Honda at extreme valve lifts, but the Honda first has to make up for it's deficit at lower lifts before it pulls ahead of the Toyota head. BTW our heads say Yamaha on them, since they helped Toyota with the design. Power/Torque come from exploding air/fuel mixtures in the engine. Injecting more fuel is easy, it's not the limiting factor. Air is the limiting factor. If you can get more air into the combustion chamber, you can then burn more fuel, hence make more TQ/HP.
If the c. head is that good then it seems to be useless to “improve” it by shaping and polishing further on, but bigger valves, 4 throttles instead of only one --- has it been done on that engine, too. ? I know some shapers who are very experienced to improve that Rover- engine most of over here still have in their Elise.
Honda no longer makes that "vaunted" Type R engine (B18C5). It has been replaced (back in 2002 as a matter of fact) with a 2.0 liter engine (K20A) that flows much better and makes 25 more horses on the RSX-type R version in Japan (replaced the previous Type R).
Even the USDM version on the '05 RSX-Type S (used to be K20A2 and is now called K20Z1) now makes 210 crank horses. Unfortunately, as has been reported, Honda did not want to supply their K20 engines to Lotus for the Elise.
The K24A engine (87 mm x 99 mm in standard form, so 2,354 cc.) with aftermarket cylinders (Darton, bored 90 mm diam. ) and some other aftermarket components will produce the best powerplant for the Elise . Wait and see.- until your Toyota engine is finished by--- )
BTW: The K20A head outflows all 2 litre heads except the F20C head, but the F20C head has larger valves. Using the same size [2 x 36 mm] the K20A head flows the same as the F20C, which is better than any 500 cc/ cylinder head.
Well if you guys are into swaps, the 1.8T motored Elises seem to scoot pretty well with their low, mid and high end oompth. Apparently some have about 350-400 HP. It's an iron block lump like most reliable turbo deals.
Of course that engine and the larger K/F Hondas don't rev high anymore...
I would have expected to see some kind of abrupt change in flow as the second cam took over, yet the graph is very smooth, no indication that the valves change lift rather suddenly. Does the flow bench not use the actual cams but somehow manually opens the valves through their range?
>>>I would have expected to see some kind of abrupt change in flow as the second cam took over, yet the graph is very smooth, no indication that the valves change lift rather suddenly. Does the flow bench not use the actual cams but somehow manually opens the valves through their range?<<<
The chart shows exactly what it states. But this might not be what folks want to know or are familiar with... If you mentally look at the graph and look at the air flow at the lifts achieved by our cams (0.29 inches and 0.44 inches) you can find that step for which you were looking.
Essentially the graph shows how much air can flow though the intake ports at various valve lifts. Regardless of which cam is used. A valve lift of zero is when the valve is closed. Our first cam opens the valve a maximum of 0.29 inches. Looking at the graph for the closest corresponding lift we find 0.30 inches at which point about 128 CFM of air can flow. This would be a bit less at the actual 0.29 amount, and remember that to get to the maximum you start from zero so we move through that lift range as the valve is opened and then closed. The cam spends relatively little time right at or near the peak opening range.
On the high intake cam the valve is lifted about 0.44 inches at which point the air flow is about 142 CFM. This is less than the Honda head, but we are still ahead net-net. Since while moving toward this maximum lift we traveled through the lower lifts, which allowed more air to enter the engine than the Honda. This is as far as the head itself goes, there are many other factors which affect things such as these. Also, you can't just look at lift, other things like duration matter on a cam. Some cams open valves faster so you spend relatively more time with the valve more open.
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