Well we do not need cam gears - remember cam gears just adjust centerline/overlap. This is what our VVT system does, and its continuously adjustable if you or your tuner knows what hes doing. I'd love to hear what all the forced induction tuners do as well as the canned tunes from vector and pcmforless. There is a lot of exploration to do with the VVT in my opininion before cams are necessary, and cam gears should never be necessary.
A custom grind for more lift is really the only beneficial way to go.
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2008 BRAZEN GXP - 5M Loaded
2006 SLY 2.4 Comfort and Power - TRADED 28-Aug-2008
sure as hell saves your bacon when you can spool a big turbo low.. more overlap bypasses more charge across the motor and gets you outta low rpm surge. I love it.
i know google is the best at answering these questions but i'm trying to understand overlap.
i understand that overlap is where the cam has both the exhaust valve and intake valve partially open at the same time... so this is for all four cylinders which allows air to flow through from the intake while the exhaust valve is still open? soo this allows more air to flow (exhaust + some of the newly introduced intake air) thus spinning the compressor that much more?
yes overlap is when both valves are slightly open..
What I had to do to the GXP to get rid of surge @24psi&3400rpm was increase the overlap. This captures a less cyl pressure but allows more mass flow across the engine, temporarily raising the Brake Specific Air Consumption (BSAC).
Simply put I take a beating on efficiency temporarily in the rpm range but never feel it from the added boost. As soon as 3800rpm shows up, the possibility of surge is gone. I swing the cam timing back in to capture the cyl pressure and my (now crankin') turbocharger is in max efficiency, right in line with the torque peak..
so no cams are avalable?? So if I do the whole built head with dual valve springs and titanium retainers and the steel valves I can use the stock cam shafts
no need to build it with the stock cams, because the car won't breathe at higher revs.
If you want to use stock cams, I'd suggest going with lighter valvetrain components, and REDUCING the spring rate to capture back lost horse, if you want to stick with stock cams that is.
No matter what you plan on doing, staying NA, or turboing later, I'd rip the head off, and do a lot of headwork. That will ALWAYS pay off, and you won't see your power dropping off as it currently does right now.
no doubt i just wish they would come up with some high lift cams so that high revs could happen without a drop off in power
High lift cams would mean more airflow at any given rpm correct? You could achieve the same thing with a set of oversized valves and head work. There are ways around the areas in which we are lacking aftermarket.
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2008 BRAZEN GXP - 5M Loaded
2006 SLY 2.4 Comfort and Power - TRADED 28-Aug-2008
oh I was talking about making more power on tap and at 6500rpm
Have you checked the Cobalt forums? Those guys have been tweaking the 2.4 long before we started.
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High lift cams would mean more airflow at any given rpm correct? You could achieve the same thing with a set of oversized valves and head work. There are ways around the areas in which we are lacking aftermarket.
Anything that increases flow can lead to a lazy bottom end. More flow is good at high rpm, but at low rpm the velocity of the inlet air charge often suffers, and therefore response. This means a bog or slow response. Then you get a lightswitch beast. A dog at low rpm, a screamer at high rpm.
This is an excessive example but it points out the dance that good designers balance in their products. Don't think maxing flow is the way to go.
Anything that increases flow can lead to a lazy bottom end. More flow is good at high rpm, but at low rpm the velocity of the inlet air charge often suffers, and therefore response. This means a bog or slow response. Then you get a lightswitch beast. A dog at low rpm, a screamer at high rpm.
This is an excessive example but it points out the dance that good designers balance in their products. Don't think maxing flow is the way to go.
isn't that what VVT is for ? don't get me wrong - i don't know squat about modern tech -- but the same with variable vein turbos... optimize for low end and then open up for higher rpms?
isn't that what VVT is for ? don't get me wrong - i don't know squat about modern tech -- but the same with variable vein turbos... optimize for low end and then open up for higher rpms?
If you hog out the cylinder head, go for large valves, or go for a big high lift cam, low rpm response will still suffer. There is no getting around physics. It's all about balance. VVT definitely helps, as long as people who design the mods know what they are doing.
I sure there are some significant improvements that can be made, but the work needs to be done by the professionals.
