sully91rs

Out of the hype going about, I did some reading on variable valve timing. I have no experience with it, driving or working on.
Variable valve timing seems to be the way to have the ultimate street/strip machine - an engine that can rev AND make power to 7 grand, but idle comfortably at sub-1000 rpm. Should I be investing time and money into the pushrod v8s, or should I be waiting for GM to get on the VVT train and push out VVT v8s (or is there already such a monster)???

84z28350

sure why not if ya got a small fortune to sink into a new design motor that may end up being a real piece of junk in the end!

87CIZ

iTrader: (8)

the ls2 can already make power easily to 6800 rpms according to ls2.com and ls1tech.com

sully91rs

I've also read VVT is just an "emissions masker." It lets smaller engines make big cam power, while still having emissions manners at low rpms.

84z, why do u say it may end up being a piece of junk in the end?

84z28350

All i meant was the design may be prone to failures...

The motors might only last 50k then nuke, or it could go a million miles.

sully91rs

I hear ya. I was looking at diagrams of VVT systems, they look insanely complex. No more 'simple' cam swaps with that stuff.

FullSendRacing

Pretty amazing what Chevy has accomplished. They stuck to their guns and keep pumping out pushrod motors. As far as I'm concerned the LS2 is one of the best mass-produced engines ever designed. ~25mpg on the highway, 400hp through emissions equipment, and a small lightweight package with relatively simple moving parts.

For comparison, BMW has incredibly complex heads - the engines weigh more due to the size of the heads to incorporate the OHCs and VVT (not to mention their new variable valve lift technology).

Even the Porsche 911 gets similar gas mileage to the 'vette, but makes less power.

Let's not even talk about the LS7. Keep up the good work Chevy! And please offer me an LS7 powered Camaro in the next few years!

joe350

They just need to figure out a way to open valves electronically. Then computer controlled VVT will be easy and you will get rid of the parasitic loss caused by the valve train. Its certainly not easy, but will increase performance immensely when someone creates it.

FullSendRacing

As it stands, Formula 1 cars use compressed air to close the valves. That was the technology that got them past the 13000RPM mark. The air (nitrogen usually) is trapped in a cylinder above the valve and is compressed as the valve opens. Due to the inevitable leaking, they keep a high pressure reserve tank to maintain pressure. They still use overhead cams to open the valves though.

DENN_SHAH

iTrader: (1)

VVT does work, it has its advantages, it also has its disadvantages.
there are more parts to fail. not changing your oil when its due is a thing of the past with VVT, it doesn't like dirty oil & can get stuck & set a code. using a heavier or lighter oil than reccomended doesn't fly with it either, that can also cause a fault code to be set & cause you to fail your emissions test.


joe350, the electronically controlled valve setup is being developed, they have working models of it now. you won't find it on a car with just a 12 volt electrical system, there just isn't enough current to run the solenoids with 12 volts. it may be on some of the cars with the split 12/42 volts systems, but it
will probably be on a higher voltage system, say like the 12/72 volt system, but it depends on how testing goes.

sometimes its scary to know what some of the things they are wanting to do in the future, things like no brake pads or shoes, brake lines being replaced by a small wire, electric power steering controlled by a joystick.
i can see it getting to the point of you having to go through a
pre-drive check list just to go to the corner store.

91CamaroRS305

iTrader: (2)

I thought they had electronic VVT in certain hybrid cars?? They have the power to do so with the huge batteries. I know I read somewhere that they already have them in some cars.

There was also a guy who built a 6 stroke engine, more power, tons better MPG and other stuff, but there were a TON of bugs to work out.....so as concept engines go, if you have the money and know-how anything is possible.

DENN_SHAH

iTrader: (1)

the VVT works with the 12 volt systems, they use oil pressure to control the timing. VVT has been in use for some time now.

were i replied to joe350, i was talking about where the valves are electronically controlled, i.e. no cam shaft.

sully91rs

Electronically controled valves, there is the sweetness. No more cam or valvetrain shopping. Want more lift, program it in. Maybe use a more powerful solenoid. Want to change timing throughout the entire rpm range, program it.
I get shivers thinking about it.

91CamaroRS305

iTrader: (2)

i get those shivers thinking about how much that would cost!!

Coach Hawk

Back in the day, someone actually made a VVT conversion for the SBC. It wasn't a true VVT, it only advanced and retared the cam timing. It worked ok, but wasn't overly reliable. It was an add on unit that replaced the timing cover and cam sprocket. If I can remember the name of teh company, I'll post it.

Homer

iTrader: (1)

i read in Hot Rod a few years ago, a guy had developed a setup for variable valve lift. It was a shaft mount rockerarm system. The shaft would move and change the rocker ratio. Could change ratios from 1.7 down to 1.5 (or maybe less). Claimed same horsepower and more mileage and more torque. Setup Costs about $1000. Or, you could use fast bleed lifters and get similar results for about $150.

Does anybody recall which issue that was? I seem to have lost mine. I think it was around 1999 or 2000

sofakingdom

iTrader: (1)

I think you just answered your own question.

You're right though; you just go on ahead and wait. The rest of us will enjoy what already exists for you.

Meanwhile, that variable rocker system really only varies the valve lift; not the duration. Which is of course the important thing, in terms of RPM ranges. IMO it's a whole bunch of nothing and drivel, looking for people with extra money to be separated from.

DLV555

iTrader: (1)

That's all VVT is, it just advances and retards the cam. The actual cam profiles don't change, with the exception of newer model that have variable lift, but even still the durations and LSA remain the same.
I am mostly familiar with the Porsche VarioCam system that claims constantly variable cam timing (VarioCam Plus also had variable lift), but in the end it is on or off. It is either advanced all the way to a certain point or retarded back to normal. From what I've heard that is what other VVT systems are like.

I believe it is BMW that is developing camless engines, maybe others as well. It sound pretty interesting, but I don't know if I would want to trust my valves to an electronically controlled set of solenoids. I guess that's just the old school in me.

my3rdgen

The GM "VFS" Solenoid is an attempt to eliminate the egr valve. At least that is what I am told where I work by our engineers. We make the VFS solenoid on one of our lines for GM.

MrDude_1

i realize this was an old thread but....

the L92 and L76 both have VVT....... and they're production GM pushrod V8s... and they're wonderfully simple.

Homer

iTrader: (1)

Does anybody have that old Hot Rod that from about 2000 that describes the variable valve lift system for sbc's? which issue was it?

ws6gta89

GM is planning on building a motor with daul in block cams that should be fun

MrDude_1

no. they're not.

sully91rs

Was that a no, you're kidding me thats awesome, or a no they are not, that guy is full of crap?

89RsPower!

I'm gonna say its a no hes fulla crap.. think about it.. how the hell would it work? Would it be an intake cam and an exhaust cam? what would be the purpose? Or is he talking about 2 different cam profiles.. and how the hell would that work on a pushrod engine?

ploegi

Well, the 4.3 has a cam, and balance shaft.... Could just substitute another cam for the balance shaft, and have an intake, and exhaust cam.

VVT on dual cam engines can also vary the overlap.

Darkshot

iTrader: (4)

Easy. The cam has a 3 dimensional profile. Each lobe is small on one side, and gradually grows to be pretty lumpy on the other side. In other words each lobe is not uniform along its length. As RPM goes up, a device pushes the cam inward so the more lumpy parts of the lobe are pushing the rods up and down. As RPM goes back down, the cam returns to its original position for a nice smooth idle. The valve timing is CONTINUOUSLY changing, and is OPTIMAL for each RPM. This is nothing new, Ferrari, among others, has been doing this in production cars for years. Of course this is optimal on OHC and DOHC V8s, but it is possible with a traditional single cam pushrod design. It would require a full re-design of the SBC, but very possible and not new technology.

Guest

Electronically controlled valves have been around for a while now, there was a company back in the ~mid-90's that was converting SBF's and doing testing but I am pretty sure they have long since been out of business. From what I remember I am pretty sure they claimed they were able to control lift and duration at a significant RPM (RPM has been an issue with electronic valves from what I know). I never was able to verify any of the claims but I did talk to them once about it.
I used to have a pamphlet/brochure, probably still do but dont know where it is. I might try to find it sometime this weekend just out of curiosity.

fire350tpi

Imagine how simple it would be to diagnose valve problems with Electronicly controlled valves, In the first place the computer would have a perameter so it would set a code, secondly find out each vlave operation by jumpering the soil. Seems easy, But you know gm would over complicate it :P

MrDude_1

thats a no, they are not, that guy is full of crap and he needs to shut the hell up because theres no room for bullsh!t on an all tech site.

fire350tpi:
GM has a history of oversimplifying engine components.. not over complicating them... for an example... look at their current V8s, then look at every other V8 in production by any other company... most have over twice the moving parts.
even GMs VVT is as simple as it can get (mechanically speaking.. inside the PCM is another story.)

ws6gta89

Wow what a mess this has caused,when i said they are planning to build a dual in block cam motor i ment it as they are talking about doing it not that they have done it already.GM recently got patents on a 3 valve staggered pushrod cylinder head which would go great with dual in block cams but for those of you that would like to call BS or tell me to SHUT THE HELL UP feel free to read the february 2007 issue of GM HIGH-TECH PERFORMANCE, page 10 on the top of the page for yourself.MRDUDE i may not know everything or even more than you but i would not waste your time or the time of others on this site with BS or bad advice so next time maybe you should do some research before you tell someone to shut the hell up

Gramps

iTrader: (1)

MrDude_1

research?
back roughly a year ago, that was news.
now, its old BS.
if you want to read about it, go read year old posts on LS1tech.

GMhiT is usually atleast a year behind on their future info.... while you're poking around, you'll also read about the L92 heads they mentioned a few months back.... notice we were talking about them for over a year before they said anything...

stop trying to get info from magazines... they're a really bad source.
----------
btw, for a perspective on my response... imagine going for a year hearing random people keep posting that, after you know its BS.... for a year.. after awhile, you dont really want to hear about it anymore.
im not trying to sound short, but thats how it is.
i guess with a magazine posting up more info, i can expect to read a explosion of more posts from the magazine informed peanut gallery on the subject...

my3rdgen

I remember when magazines were our only source of info. That was before we had electricity and we had to watch TV by candle light.

Gramps

iTrader: (1)

lol back when christ was a cowboy eh?

anybody have any idea on reliability and cost of parts? do they compare to pushrod V8s?

Guest

I dont know that I'd be making statements that an internet website is more credible than a magazine article, at least not in public.

ws6gta89

So let me get this right MRDUDE you said i was full of **** and to shut the hell up because i was wrong yet you just said that you have known about this for a year if that is true then why would you call me a liar?why would you even post a response?it doesnt matter if i find out about something after you did the point was that you said it was false which it wasnt so now lets here what negative comments you have to say now!!!!!!!!!

sully91rs

Okay guys, take it to PMs. I don't want to see this thread get closed.

I can partially agree. If you read some of the profiles of members on this website, a few work for GM, and a lot are around the field everyday, adamantly. So info on this site I give credit, although I can't deny BS flying around on here every now and then.

I'm interested in that too. Anybody order VVT parts yet?

MrDude_1

basic chain of events... (no commentary needed)

GM starts looking for VVT designs

couple designs goto prototyping stages... including that dual cam in block idea.

dual cam idea becomes known outside of GM (along with other things)

dual cam idea is completely dropped. dead. finished.

for the past year, random people, hearing the old news, buring it up as if it was actually going to happen.




thats the total chain of events.
its BS, its not going to happen. peroid. its dead.
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i dont trust websites... but there are specific people i trust.

as for the credibility of magazines.. its people like the ones posting online that write the articles...(myself included)

rx7speed

hey there is some duration change at .050"lift
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you trust your motor not running lean and popping a piston with detonation due to those little selenoids don't you?