I am trying to get an understanding of how adjustable cams are helpful to a tuner and what they do. Now the point of an A-cam is so you can move LSA correct? And LSA controls overlap, which in turn moves the bower band. Am I on the right track here? The point of moving a power band is to maintain a constant maximum acceleration in relation to your gearing within your transmission, if I understand correctly. Am i getting this correct?
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Originally posted by deevergote -
There ya go, I'm sure you will get a better, more in depth, and faster response here. Good luck!Originally posted by leroy457 View PostOriginally posted by Mishakol129 -
yes you are
advancing or retarding the timing on a adjustable cam gear, changes the powerband of the engine
needed when trying to extract the most out of an aftermarket cam
and it works, thats why most cars bring a vvt system nowadays, moving intake cam timing on the fly helps on low end torque and at high revs
something you cant do w/o this system
HP and TQ work in opposite forces, when top hp is achived TQ is lost and viceversa
Originally posted by deevergote
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www.howstuffworks.com/camshaft
Learn how a camshaft works, and you will have a better understanding of what happens when you change the timing.
just remember... it's the gear that is adjustable, not the camshaft itself. The camshaft is just a stick with bumps on it. The VTEC system used in the H22 is about as close as you can get to an actual adjustable camshaft.
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actually honda didnt come out with an adjustable camshaft until 03 with the k20
toyota was actually one of the first manufacturers that used this technology, followed by mitsubishi and their mivec systems
vtec on the other hand uses a variable cam lobe like the neo vvl on nissans
to open both valves when engaged and one valve and a half when not
this system was adapted to the f20c in the s2000 and it picked up around 30whp and 46ftqt
to the OP what engine are you refering to, talking about Lobe Separation Angle
lobe separation is fixed on a camshaft, the only way you can change it is by changing the camshaft it-selfOriginally posted by deevergote
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When I mentioned LSA I had the f22a1 in mind(my engine) LSA can only be changed by machining the cam/switching the cam?Originally posted by deevergoteComment
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Yes. Think about it... lobe separation angle. You would essentially have to move the lobes of the camshaft to change the LSA. There are no camshafts that have movable lobes (none that I'm aware of, anyway...)
Oscar, the K series doesn't have an adjustable cam... rather, it has an automatically adjusted cam gear. That changes the valve timing, but the cam lobes remain fixed.
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Correct. And actually a cam gear does not change the powerband either.Originally posted by deevergote View Post
The cam gear can be adjusted to achieve better valve timing, which gives performance via higher cylinder pressure. The process is usually referred to as degreeing you cam. On vtec motors, particularly the k series, and ivtec, the gear automatically adjusts, variably, to create higher cylinder pressure, basically by adjusting valve timing in accordance w/rpm.
Your cam profile, lobe center and separation angles as well as lift/duration never change without replacing the cam. The gear does not move the power band.
Changing lift/duration profiles on a cam moves the powerband.
All the gear does is allow for better then oem valve timing-that's it. Consider it a way to fine tune the valve timing. It's generally not needed for an oem cam, the gear was made for perfect valve timing. Using an aftermarket cam changes the lift/duration-in other words, the valve timing.
Fwiw, this isn't suggested for a novice. Degreeing a cam is tricky, and takes practice. On our f22 motors, making a mistake could cost you alot. Really with any high interference engine playing with the cam gears is risky.
Most people have to use a gear though with an aftermarket cam since the lca and lsa have changed, the lift/duration is different too so the oem gear timing mark isn't as accurate as it could be, hence the need for an adjustable hear to find optimal valve timing w/out having to pull the belt tension repeatedly.
Theres a lot more to it then that, but that's the overview.
Ideally you want valves closed at bottom dead center for the piston to be able to compress the absolute most air possible during the stroke.
However, that's near impossible with an aftermarket cam and a stock gear. The stock gear can only be adjusted one tooth at a time.
Adjustable gears can be adjusted to any degree you chooseOriginally posted by wed3kComment
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Adjustable gears also offer very little benefit on a stock engine, with a stock cam. Once serious modifications are made, the adjustable gear can make a big difference. But yes, as toycar said... if you don't know what you're doing, you could cause more harm than good. I've also heard reports from various people (with a bit of experience behind them) that HATE adjustable cam gears, because they have a hard time setting them exactly where they want them. Honestly, I think it's an overkill mod on a street car. Unless you're trying to wring every ounce of power out of a race car, or you have a strong desire to "upgrade" every single part you can... it's really not necessary.
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ive heard of a lot of somewhat high boost on stock block nissans running adjustable cam gears to pick up some valve overlap. almost like cheating to drop compression ratios.
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That makes no sense to me... they're running high boost, but blowing some of that intake charge right out the exhaust valves! Not only are they losing power-making air/fuel mixture, but they're also sending a dense unburned air/fuel charge into the exhaust manifold and turbo, where it is bound to ignite once it gets hot enough.
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well overlap is always minimal because otherwise your looking at bent valves. but even with throwing unburnt fuel/air out the exhaust with overlap, your still filling the cylinder completely so you wouldn't really lose power, just fuel economy.
thats just a bit of what i heard running around the scene here and there.Comment
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overlap is determined by the cam grind, not cam timing.
cam timing is still very tricky to me and i degreed the cam in my vw but it took me a very long time. 112 degree LSA and it idles like stock. (it's a supercharger cam though)
the delta 272 wasnt degreed in and it barely idled.
advancing the cam will make you power but with high octane, i wouldnt go over 4 degrees. look up the dynos and researchComment
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You can adjust valve overlap with adjustable cam gears on a DOHC engine. But yes... the grind determines overlap with a SOHC.
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