Why hasn't VTEC been adapted to pushrod engines?
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Why hasn't VTEC been adapted to pushrod engines? VTEC provides two lobes for each valve. One is a mike toast lobe that would be home in a Cadillac, say a 200/204. The other is lobe that would be at home on a race track, say a 252/256. Electronics transition change based on engine speed and throttle position. Other factors, such as MAP or MAF could be used.
The mechanism is an oil pressure powered pin that that enables a more aggressive rocker arm on a different lobe. These or OHC motors.
However, I can envision a lifter with two rollers where the roller against the more aggressive lobe was pinned by oil pressure.
Imagine passing emissions with a car that made peak power near 7k with a camshaft in the 250s!!!
The mechanism is an oil pressure powered pin that that enables a more aggressive rocker arm on a different lobe. These or OHC motors.
However, I can envision a lifter with two rollers where the roller against the more aggressive lobe was pinned by oil pressure.
Imagine passing emissions with a car that made peak power near 7k with a camshaft in the 250s!!!
6600 rpm clutch dump of death Administrator
Joined: Dec 2001
Posts: 4,983
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From: Texas
Originally Posted by DavidNJ
VTEC provides two lobes for each valve. One is a mike toast lobe that would be home in a Cadillac, say a 200/204. The other is lobe that would be at home on a race track, say a 252/256. Electronics transition change based on engine speed and throttle position. Other factors, such as MAP or MAF could be used.
The mechanism is an oil pressure powered pin that that enables a more aggressive rocker arm on a different lobe. These or OHC motors.
However, I can envision a lifter with two rollers where the roller against the more aggressive lobe was pinned by oil pressure.
Imagine passing emissions with a car that made peak power near 7k with a camshaft in the 250s!!!
The mechanism is an oil pressure powered pin that that enables a more aggressive rocker arm on a different lobe. These or OHC motors.
However, I can envision a lifter with two rollers where the roller against the more aggressive lobe was pinned by oil pressure.
Imagine passing emissions with a car that made peak power near 7k with a camshaft in the 250s!!!
Actually they have already adapted Variable Valve Timing for pushrod engines. The new Impala uses VVT on both its V6 engines, and they are both OHV. Its just not as beneficial on a V8, being that they have such broad HP and TQ curves to begin with. So it would help, but probably not enough to justify the added cost and complication of adding VVT.
And for the record, VTEC is a Honda brand name for VVT, it stands for Variable Valve Timing and Electronic Lift Control
And for the record, VTEC is a Honda brand name for VVT, it stands for Variable Valve Timing and Electronic Lift Control
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Joined: Jun 2002
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From: Upstate NY
Originally Posted by DavidNJ
VTEC provides two lobes for each valve. One is a mike toast lobe that would be home in a Cadillac, say a 200/204. The other is lobe that would be at home on a race track, say a 252/256. Electronics transition change based on engine speed and throttle position. Other factors, such as MAP or MAF could be used.
The mechanism is an oil pressure powered pin that that enables a more aggressive rocker arm on a different lobe. These or OHC motors.
However, I can envision a lifter with two rollers where the roller against the more aggressive lobe was pinned by oil pressure.
Imagine passing emissions with a car that made peak power near 7k with a camshaft in the 250s!!!
The mechanism is an oil pressure powered pin that that enables a more aggressive rocker arm on a different lobe. These or OHC motors.
However, I can envision a lifter with two rollers where the roller against the more aggressive lobe was pinned by oil pressure.
Imagine passing emissions with a car that made peak power near 7k with a camshaft in the 250s!!!
Originally Posted by Old SStroker
Shoot, we came up with that idea back in high school when SBC was still a 283. It didn't work too well then. Maybe the new rubber technology would help.
Where are you from old timer. I see upstate NY, ever go out cruising? Car shows? A bunch of us hit quite a few of the shows during the summer...one more can't hurt.
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From: Blackwood, NJ
Yea, I've heard of experimenting with solenoids. The biggest problem was getting them to last more than like 500 - 1000 miles with the heat from the engine. I'm sure in time they'll have a reliable setup like that, since heat seems to be the biggest limitation.
Originally Posted by Domestic Demon
Actually they have already adapted Variable Valve Timing for pushrod engines. The new Impala uses VVT on both its V6 engines, and they are both OHV. Its just not as beneficial on a V8, being that they have such broad HP and TQ curves to begin with. So it would help, but probably not enough to justify the added cost and complication of adding VVT.
And for the record, VTEC is a Honda brand name for VVT, it stands for Variable Valve Timing and Electronic Lift Control
And for the record, VTEC is a Honda brand name for VVT, it stands for Variable Valve Timing and Electronic Lift Control
TECH Resident
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From: Chicago, IL
It's probably because the Hondas have to make up for lack of cubes. One cam profile gives it more low end to get it going and the other takes over on the high end. V8's don't need any help to get going. If you switch to a big cam and lose low end torque, get some 4.10s. 
Originally Posted by Domestic Demon
And for the record, VTEC is a Honda brand name for VVT, it stands for Variable Valve Timing and Electronic Lift Control
On The Tree
Joined: Jul 2005
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From: Iowa
Originally Posted by LiquidFire350
isn't VVT the name that Toyota uses, not that who using what name really matters
The rubber lobe idea sounds wicked, I gotta read about that. Did you or your friends ever actually try that, Old SStroker? What did you mean by it didn't work too well?
VVT is used on the new 2.4 eco tec motor , its just a variable adjustable cam gear
im not sure how the V6 works , i havent got to play with 1
and you could split the cam lope in half , and make it 2 seperate 1's , and use a lifter with a doulble roller , and use the oil to press the 2nd roller to the cam lobe
but why ? todays V8's are better than those from the 60's
i never had any success with the rubber cams either , mine got to hot and melted
im not sure how the V6 works , i havent got to play with 1
and you could split the cam lope in half , and make it 2 seperate 1's , and use a lifter with a doulble roller , and use the oil to press the 2nd roller to the cam lobe
but why ? todays V8's are better than those from the 60's
i never had any success with the rubber cams either , mine got to hot and melted
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From: Home
Originally Posted by Old SStroker
The cheap way to get variable lift and duration is the old "rubber lobe camshaft". The faster you spin it the wilder the lobes get due to inertia forces. You could make the lobe almost anything you want by imbedding little tungsten (or Mallory) slugs in the rubber. Shoot, we came up with that idea back in high school when SBC was still a 283. It didn't work too well then. Maybe the new rubber technology would help.
On The Tree
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From: Iowa
Originally Posted by s/c'd cav
i never had any success with the rubber cams either , mine got to hot and melted
It might be worth it to run a couple races and then change it out, at least a couple times for kicks. I'm pretty interested in this.
Originally Posted by Zeus
I'm pretty sure they do this on F1 cars already don't they? I remember reading somewhere how F1 cams were made of a special alloy that expands very precisely when heated, thus creating a "bigger cam" during a race.
Jon
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From: Iowa
Originally Posted by distortion_69
What about variable lifters, like the ones you read about in summit or jegs for smallblocks that pump up when the revs get up. I believe they are called rhoads.
Josh
Josh
For maximum low end torque, engine vacuum and fuel economy, you need a smaller, more efficient cam. But smaller cams rob mid and upper RPM power needed for fast acceleration. For more mid and upper RPM power, you need a larger, more powerful camshaft. But larger cams are murder on low-end torque, engine vacuum, fuel economy and idle quality. With Rhoads Lifters, you get both! Rhoads Lifters work automatically and give you a ''smaller'' cam at lower RPM and a ''larger'' cam at higher RPM for the best of both worlds. How you ask? At idle and lower RPM where lugging power and more torque are needed, Rhoads Lifters ''bleed down'' to make you cam seem smaller by about 10°. This really boosts low-end torque, engine vacuum, fuel economy and idle quality. At higher engine speeds where more cam boosts mid and upper RPM power, the Rhoads Lifters work to restore full lift and duration of your cam for maximum top-end power. As your engine revs higher, Rhoads Lifters bleed less because there is simply less time to bleed at higher engine speeds. Near 3500 RPM, the bleed action has virtually disappeared, shifting back to your full cam and maximum horsepower potential back into action. Here's an example:
Using a hydraulic cam with 280° duration and .450'' valve lift, here's approximately what the valve timing will look like inside the engine at various RPM using Rhoads Lifters vs. stock lifters:
Using a hydraulic cam with 280° duration and .450'' valve lift, here's approximately what the valve timing will look like inside the engine at various RPM using Rhoads Lifters vs. stock lifters:
@ Idle________260°_____.425''____270°______.450''
@ 2000 RPM___265°_____.435''____270°______.450''
@ 3500 RPM___270°_____.450''____270°______.450''
Stock lifters don't vary the valve timing. Rhoads lifters do. Stock lifters can ''pump up'' at higher engine speed, drastically cutting power. But Rhoads Lifters actually help to eliminate pump up, adding as much as 500 more usable RPM on the top-end. You can even hear Rhoads Lifters work! They make a mild ticking sound at idle, which tells you they're working to boost low-end torque, vacuum and fuel economy. When the size of your cam is ''reduced'' for more low-end torque, the valves seat at a slightly faster rate, producing a mild, solid lifter sound. This sound gradually dissapears as your RPM increases, ''restoring'' your cam to its full size for maximum top-end power.
And despite this, which I believe:
Nope. The use of any variable valve timing/ variable valve lift system is prohibited.
Jon
Jon
Honda's exclusive VTECÔ (Variable Value Timing and Lift Electronic Control) technology was first developed for our Formula 1 racing teams and has now been applied to the BF225 and all-new BF150 outboard. Push the throttle and you'll feel the result.
Last edited by Ballistic Jello; May 8, 2006 at 03:43 PM.