MrDude_1

iTrader: (4)

exactly.

hence the need for the cam to expand for that extra edge.... its not a variable valve timing system.. its not a variable lift system.. its mearly the effects of heat on the cam...

thats not breaking the rules.

Ballistic Jello

So they get away with it by saying it's the natural reaction of the material, so it's unavoidable, or something?

Wnts2Go10O

iTrader: (12)

the hondas that are actually quick don tuse the vyec

I <3 80057

iTrader: (1)

You read my mind, I was just about to say "Rhoads lifters". I asked my dad about this a while ago, why lift control isn't incorporated into pushrods and the concept seems pretty simple. I have an old LT1 cam that I plan on experimenting with this summer. Those Rhoads lifters have been around for a long time and are pretty darn cool. Solenoids are out of the question until heat issues are neutralized through further R&D, but the big three (sans DCC) are barely keeping their head above water and cannot even keep all of their plants open, let alone have much of an R&D branch. I mean, they brought back DOD with GM and MDS with DCC. Funny how GM got right AFTER DCC got it, the first time. Anyone remember the Cadillac 4-6-8? I don't, I wasn't born yet, but my father says it was a joke. Know what else is a joke? Putting the DOD technology in the new Camaro, . There is still compression with valves opening and closing on 4 cylinders, I don't like this and neither would a customer in the demographic to buy the new Camaro. Hell, my SS gets over 30mpg on the highway. 75mph @ 1750rpm, gotta love that!

Blake

Phoenix 5.7

iTrader: (7)

they tested the Rhoades lifters in a LS1 in i believe it was hot rod. they put some bigass cam and tested with stock lifters and the rhoades. think they gained a bit down low and lost a few up top. said dirvability down low was way better

BigPlanTransAm

do they even make those for our cars? i see a list at the bottom of the page for what cars it fits but it only goes up to '89s.

LTSpeed

Ahh, the old flexible carbide concept!! That's the same stuff they want to coat the space shuttle with...

HSV-GTS-300

I sometimes wonder if a system would work where the complete camshaft can be floated horizontally with oil pressure. The lobes instead of being ground parallel to the axis of the cam could be wider than normal and have a slight "ramp" angle along their longitudinal axis. This could achieve variable valve lift but not duration I guess.
Of course the lifters would have to be non-rotational and have the same ramp angle built into them as well.
It's probably been tried before.

andereck

Well along these lines if you're looking low speed velocity and strong upper rpm performance then Offenhauser created a "Dual Port" intake manifold that has a small volume runner that is fed by the primary throttle blades of a 4 barrel. The larger volume section of the runner is fed by the secondaries. I belive the primary volume was approx 1/3 the volume of the secondary. This was great for a spreadbore carburetor and the manifolds have excellent all around performance. This was late 60's/early 70's and you can still purchase them today. The manifold requires more complex casting tecniques and obviously didn't catch on to the performance crowd, like most of the Offenhauser line. Its all marketing. Offenhuasuer/Edelbrock can be compared to Linux/Microsoft. The smaller market company has had some great ideas but just weren't presented to the masses properly. Maybe the volume used by the divider wall put off the performance crowd.
Not for the LS1, but it is an example of a dual mode breathing system for a pushrod V-8.

Old SStroker

You are looking at a 3-dimensional lobe surface rather than just a flat face or tapered (solid flat lifter) one. Imagine a .500 or so spherical lifter foot, probably ceramic or DLC coated. Now generate one end of the intake lobe at one duration, lift and ICL, and generate the other end at another duration, lift and ICL and blend the different profiles across the lobe. It would be analogus to blended bifocal glasses. Do the same for the exhaust lobe. You might also DLC coat the cam. With both coated the mu is miniscule.

Now move the cam axially as you said as well as advance/retard as we do now on some engines, including pushrod engines.

I think it could be made to work, but at considerable expense. The lobe grinding would be tricky to say the least, but I'll bet an Okuma CNC cam grinder could be congfigured to do it. Would it be worth it? Perhaps. It would make an interesting study.

I've thought about this before but I don't know if it has been done.

swearitsstock

its kinda funny you brought this up...
In the toyota community, our 97+ model 2JZ motors came with VVTI... and any who plans on making over 500rwhp gets rid of it...

Although it is nice for a street car, and saves on gas, gives anice ride at low rpms, its just too difficult to deal with when your tuning a car to make big power

thats why we offer kits to get rid of the VVTI system

KillerBrink182

Ferrari uses exactly what you described. And like Old SStroker said, it's called a 3D profile.
Now this is with OHC, so there would most likely be some changes to use this in a pushrod engine.

joecar

The most versatile would be PCM controlled bi-directional solenoids operating the valves, pushing them open and pulling them shut.

I don't know the issues, but heat was mentioned, and I imagine that the solenoid must be able to move the valve mass to the open/shut extremes at the max operating frequency without floating;

at 6000 RPM the max operating frequency would be 50 Hz, but now since the valve train is eliminated you could spin faster, so the max freq. could well be 100 Hz;

to move the valve mass at those freq's requires a hefty push-pull solenoid (or 2 opposed solenoids) with sufficient cooling;

I like the idea of being able to tune it from a laptop, but it can be scary.

knowitman

I could see two opposing selenoids being used in which one opens and one closes. This would negate the need for valve springs thus removing one component that lowers the redline. Gone would be the days of buying new cams. If you want to try a new cam just plug your laptop in and change the profile. Heck you could essentially have an infinite number of profiles as the RPMS increase. If the heating issues could be solved it would by far be the most versitle and efficient "valve train". You could even have a performance tune for the track or showing off and a DD tune for gas.

dame

iTrader: (3)

im so glad I have 2 of those right now

DavidNJ

Ok, let me add some details.

Most variable timing mechanisms are variable phasing systems, just advancing or retarding a camshaft with fixed duration, lift, and ramp. With a dual camshaft system (like a DOHC, but not necessarily OHC), the LSA and resulting overlap can be changed. Great stuff for emissions.

BMW can also adjust the rocker ratio dynamically. This adjusts the lift but not the duration.

Honda, and more recently Toyota and Porsche, have separate lobes for high speed operation. To the best of my knowledge, they operate with a hydraulically engaged alternate rocker arm. Although the Honda system didn't originally include variable valve phasing, Honda, Toyota, and Porsche couple alternate lobes with variable phasing in their current designs (not the S2000 though, it just missed it in 1999).

In what I'm proposing, the too lobes would be ground adjacently. They could even be pressed on Ford style. The lifter could be increased in diameter if necessary to say 1" or so. Then, the lifter would incorporate two rollers. The roller over the 'VTEC' lobe would be engaged via hydraulic pressure triggered by a central solenoid. Using a axle-less setup like Schubeck, the assembly could be even simpler.

Again, correctly done, for an LSx engine, you could have a 200/204 120 with .475 lift below say 4.2k, and a 248/256 108 with .650 lift above 4.2k to say a 7k redline.

Just a note. That was a recipe for a Type-R, S2k, new Civic Si engine (which is really a Type-R). They have large ports to handle high engine speed/high power operation (think of an S2k is half of a 480hp 4.4L V8 or 1/3rd of a 720hp 6.6L 12.) More mundane Hondas have a less aggressive VTEC lobe and smaller ports. All the Hondas using different duration and lift on the 2 intake valves in non-VTEC operation, something a 2v couldn't do. Or wouldn't have to do. However, they still get a big does of good high and low speed operation.

Zeus

Same thing they do with their "variable" wings.

"Honestly FIA, we made it as stiff as we could, but it's impossible to make a completely rigid wing".

mypoorLS1

iTrader: (4)

I think the idea here is to use ball valves. That way you don't have the valve creating turbulance. When the ball is open, it's a straight shot. If you used a magnet to controll it. No cam, nothing. Tune it short duration for low RPM's and as long as you want for high RPM's. I think that's how indy cars spin incredible RPM's. but$$$$$$$$$$4

Jon B.

iTrader: (5)

Considering the fact that the FIA rules ALSO dictate the material used in construction. I find that hard to believe.

Jon

silverTA2002

iTrader: (1)

I could see where the huge tq curve would be kinda cool.

But, the reason it hasn't been adapted on v8s is that there are cheaper ways to make efficient power with a large tq curve. (cubic inches).

v8s use displacement to make power. We don't need the expensive "tricks."

Want more power? Supercharge the sucker.


Kinda interesting that the lightweight old 160hp vtec civic got the same HWY mpg as the heavy v8 325+ hp fbody.