under pressure

[firebird77clone]

I've been thinking of compression ratio, fuel ratio, and infinitely variable valve timing.

As I understand it, there is an ideal fuel ratio, which the O2 sensor gives feedback to maintain.

I saw a show a little while back where s guy is developing hydraulic valve actuators, electronically controlled, which not only give infinite valve timing, but allow the lift profile to be infinitely modified. This also allows complete removal of the camshaft and its parasitic power load.

Static compression refers to the volume ratio of cylinder with piston down, vs. Piston up. About 8:1 is stock, mainly for emissions requirements, anything over 9:1 and you have issues with detonation, but the power increases.

Now to tie it together

Isn't the end result of compression ratio pressure? Seems to me, the piston diameter and stroke are irrelevant, the resultant pressure is decided by the compression ratio. BUT, if you don't allow the cylinder to achieve a full charge, the end pressure will be less. Hence with infinite valve timing, couldn't you control the cylinder pressure, allowing the engine to mimic a low compression engine, and of course let the computer adjust fuel and timing.

[pat mccarthy]

do not for get rod length plays in the mix . no you can not hold the valve off seat to make a 17to1 engine run like a 8to1 .over lap or holding valves off seat longer any way you cut it the valve needs to seat to help cool it you would have to add another valve for only bleed down . i can not see this working very good. to much over lap or valve timing of valves fuel /air and ex mix will start back up and to revert . a chamber injected/ with a mix cocktail water and ?/ and threw timing span release would be a better way to go instead of a heavy bleed down for CR with valve to piston timing some setups start with a base of lets say 8to1 they move cams to gain power cam timing so the dynamic CR changes only cam or cams are moved on some by oil psi can do not forget the PV of valves will change to

[Dave Severson]

Kind of what the VVT (variable valve timing) system does. Company in Texas was working with a solenoid operated valve system many years ago, must not of worked out for them never heard more about it (this was in like 1977). Truly amazing to me what the computer in a car can do with the timing and fuel flow now on the EFI engines! I know in bracket racing with EFI and a good tuner on the laptop the cars can become so consistent it's almost scary!!!! I see why the Pro teams have a man on the computer in the trailer full time at events!!!!

[jerry clayton]

Education is expensive. Keep that in mind, and you'll never be terribly upset when a project goes awry.

[pat mccarthy]

they use it or did in indy cart??? many engine now have a varable timing of cams the. cart i think did a way with most of the valve train. friend has a echo tec in a boat had to check cam timing as to were the cams were with out of phase or moved with out the help of the computer did away with all that ran a stock dist drove it off the end of the cam

[firebird77clone]

Pat, thanks so much for your feedback.

It seems like we aren't looking at it from the same perspective.

With mechanical valve timing, you cannot change the lift or duration.

With electronically controlled hydraulic actuator, throw out the rule book. Notch the pistons, and you can leave them open 360*, if you like.

What I am thinking, is you close the valve well before tdc, you reduce the amount of air drawn in. Now your 350 running 11: 1 static compression is developing cylinder pressure no greater than a stock 8:1 compression motor.

The valve overlap is modified, your 11:1 motor is running smooth and docile, you can even pump low octane so save $$ on your daily commute. Then tank up with av gas, drive to the track, flip a switch, and the beast rumbles and crackles ready to make asphalt scream for mercy.

[pat mccarthy]

Pat, thanks so much for your feedback.

It seems like we aren't looking at it from the same perspective.

With mechanical valve timing, you cannot change the lift or duration.

With electronically controlled hydraulic actuator, throw out the rule book. Notch the pistons, and you can leave them open 360*, if you like.

What I am thinking, is you close the valve well before tdc, you reduce the amount of air drawn in. Now your 350 running 11: 1 static compression is developing cylinder pressure no greater than a stock 8:1 compression motor.

The valve overlap is modified, your 11:1 motor is running smooth and docile, you can even pump low octane so save $$ on your daily commute. Then tank up with av gas, drive to the track, flip a switch, and the beast rumbles and crackles ready to make asphalt scream for mercy.

nope.. i think your going to bleed down a hi CR engine to gaine??. not going to work like you think. to reduce intake draw by then haning what ever valve you want open or keep shut . you never said carb or fuel injection maybe your ideal would work better as a 2 stroke gas engine with a variable blower boost ? many ways to go. many have been done . from a 8to 1 to 10to1 every thing the same in the engines. gain may not be more 30 hp this maybe it abit generous . that why i said 17to1 cr would have to be better to make worth the work .the cam in the 10to1 is going to add some hp and rpm. there still port flow port size and how the fuel air mix and CFM of with ever you pulling air threw the intake . a rotory valve engine with a variable rotory timing would be nother way no valve in the way . piston can be made and chamber for the best burn . honestly i just realy can not see it you way... as a engine builder i want to keep the intake valve open a fair amont of time . you dening the engine breath and helping some of this is over lap both valve off the seat.nother thing to look at is the pistons start it.s way you say your going to move the cam by moving valve open timing ? by how much ? you need watch that ex valve . a lot of things go on in a engine somethings that many claim to know .i do not. i only know how to machine them and on a good day i know what cam and cr in the real world works build them and make good power. i do not know if it on the web but the engine with just a piston no crank call spilt fire ? piston were on a geneva gear .

[jerry clayton]

You could do some of that type of timing with a rotary valve 2 cycle ( best option probably with diesel or liquid nat gas)


I worked at doing a 2 rotary valve per cylinder with overlapping discs--needed to be 2 cycle because couldn't spare space/weight for 4 cycle 2-1 valve/crank---


electronics are only good at controlling spark timing and electronic fuel injection----the physical power it would take to drive a valve train (x 16 or 32 valves) would require electrical devices(read motors) of not only several hp but upwards of 5000 rpm
and then when you do get the valve lift and velocity to make the hp you want, valve bounce and fly off the lobe after top lift point become virtually uncontrollable.


With the size/weight of todays vehicles and loads/speeds driven(raced) it relly comes down to engine external deminsions that fits between the fenders with the accessories needed(intake/exhaust system,starter,clutch,etc)


and that's if we stay internal combustion----if you want to go with external combustion (steam) or turbine power(jet) it broaches a different area and I also done some of that----------

[firebird77clone]

I don't know if the guy's work is posted on the web, wish I had taken notes when I saw it. He's doing amazing stuff with his electronic control hydraulic lifter actuators.

The fuel economy gains just from eliminating the parasitic power loss from the camshaft is significant. Add to that, he has plans to plumb in an air tank: cut off fuel to cylinders and pump air into tank during braking, then pipe the compressed air back into the engine to get the car moving, and switch back to standard operation when the air tank bleeds down.

I simply don't remember the fuel economy numbers, but they were really impressive, all achieved with standard fuel technology.

The guy said he was going to market them as a drop in retrofit kit, undoubtedly he would target the sbc 350.

Anyway thanks for entertaining the concept. Wish so much I was tinkering with engines for a living, instead of antiquated industrial production machinery.

[rspears]

Like this? Link - Clemson Vehicular Electronics Laboratory: Electronic Valve Timing Control There are others working on it, too.

[pat mccarthy]

I don't know if the guy's work is posted on the web, wish I had taken notes when I saw it. He's doing amazing stuff with his electronic control hydraulic lifter actuators.

The fuel economy gains just from eliminating the parasitic power loss from the camshaft is significant. Add to that, he has plans to plumb in an air tank: cut off fuel to cylinders and pump air into tank during braking, then pipe the compressed air back into the engine to get the car moving, and switch back to standard operation when the air tank bleeds down.

I simply don't remember the fuel economy numbers, but they were really impressive, all achieved with standard fuel technology.

The guy said he was going to market them as a drop in retrofit kit, undoubtedly he would target the sbc 350.

Anyway thanks for entertaining the concept. Wish so much I was tinkering with engines for a living, instead of antiquated industrial production machinery.

well i was in love with the ideal but i can now say hell no you do not want to machine and build engines for a living. not for the weak of heart and need patient a mile long and every now then someone going to test it for you . pay realy sucks. i have some great storys about this line of work and i bet Jerry has more then one to. cam it self not that big of a deal running it or not much parasitic loss not having it .now that hang off the cam getting turn is the oil pump . now if you can loose the oil pump and all upper valve train then it a big deal . said thing is most companys have a hard time making a simple. lifter there some bad stuff out there now that.s bitten more then one ass