Quote:
Originally Posted by serialk11r
Oh, just saw this project for the first time. Not quite what I would expect on these forums haha, but great nonetheless.
Sorry if this was made clear somewhere else, why are you bothering with the exhaust VTC? Most of the gains to be had come from the intake camshaft. AFAIK you can have the cam base circle ground down a tiny bit to add duration and then cut lift to get a more-Atkinson cam, which should get you the equivalent of 10% taller gearing for a very low price.
I'm eagerly anticipating your lean burn tuning, it will be fun to see how lean the K24 can run. Stable combustion at 19:1 would be really good already, if the rumor that a K20 can run that lean is true. The ease of getting parts for and tuning Honda motors makes me envious.
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So the K24A which I have, has VTEC (two different cam profiles) on both the intake and the exhaust valves. Not all K series motors have VTEC on both - in most it's just intake. I understand Honda did away with the exhaust valve VTEC on most later motors as it wasn't worth the added cost/complexity. However, VTC != VTEC. The intake cam can be phased forward 25 degrees in the stock configuration, and 50 degrees with the phaser I replaced it with. The reason the motor doesn't come with a 50 degree phaser to begin with is that there's a possibility of the valves hitting the pistons in some scenarios, which is why I put a pin in to limit advance to 40 degrees.
Frankly I would have preferred the later K24Z motor which lacks exhaust VTEC and has an integrated header, but this one was
significantly cheaper and is generally considered more desirable by those just looking to make power.
Looks like tuning is going to be... complex. There's RPM, load, AFR, ignition timing, and intake cam phasing, and these must be tuned for both the high and low VTEC cam profiles whose cutover point are then chosen based on where the power curves intersect. I'm not even going to think about grinding cams at this point, though an atkinson profile at low RPM does sound pretty desirable.
