Camshaft friction

[Shakotan_Aaron]

It would maybe have to be like a on/off sort of thing like the 4ag vvt id think. How is vvti normally activated? normally by a solenoid? if so then it could then be controlled by any modern aftermarket ecu. Maybe buy a 4ag vvt pulley, pull it apart to get the idea of how it works and just copy it? or take the principles from it. These also variable timing thats constantly varying depending on exact load and RPM. This maybe your ultimate goal by the sounds of it.

Then the other question is, is there a market for this and at what price? how universal can you make it and are the gains really there enough for people to warrant forking out the money.

I dont see how you can make a direct bolt on kit without either supplying a new cam gear or machining the original gear.

[andrew_mx83]

most OE systems use oil to move the gear around, difficult if the cam and head wasnt setup like this from factory..... not to say it isnt impossible

[knightrous]

Thank you all for the replies! I really appreciate it.

First of all, the reason why I'm looking into it.

I have for a while wanted to develop a concept for vvt mechanism that can work for any engine, that is to say, a straight bolt on camshaft pulley where all the parts and the mechanism itself is conatined within the gear it self. This of course means that the mechanism would have to be powered by any forces wich can be harnessed inside the gear. In my head it would be a mechanical design able to phase the camshaft to smooth out the torque curve. To be able to use any force for this purpose it must change with the rpm of the engine. This is why I'm looking into this particular aspect. If I can come up with a cheap effective design, my plan is to make it into a business, but that is in the future. I'm currently an economics student so I have no resources or workshop to do any experiments, and that is why I have to rely on you fine people. My plan is to come up with a few possible designs and test them out in AutoCad or something else, and if it can be produced cheaply and people are willing to pay for this modification I would try to invest some money into it. I am a Toyota enthusiast so if this comes true I would first make it for engines like the 4age, 3sge and what not.

I've considered doing something similar. During my research, I found that Toyota had prototypes a system in the 1980's that was external to the head and was controlled by a stepper/servo motor. The article that shows this design is below:

[091980]

Knightrous, I've considered that kind of design, but in my opinion it's to big and complex and this drives costs up. My goal is to make a simple cheap design which retards the timing as rpm is increased.

If there is a merket for it, or not, would depend on how much it costs, don't you think? I have been doing some research using EAPro and typically there is a 3-5 % increase in average torque. The increase is usally bigger the further away you are from the max torque rpm, making the torque curve much flatter. I think it could be a very nice upgrade of the engine especially if one has uppgraded to bigger cams. This system would improve driveability during everyday driving, I think.

[SHEPPO3930]

About the only way u could do it is have the inner and outter parts of the gear able to rotate separately to each other, say 5deg. Then have a spring or rubber block or something that acts as resistance to the rotation. Simply put the more torque required to turn the camshaft, the more retarded it (the cam) would be. Sounds simple enough, but it would be pretty hard to control the cam timing when you're cranking the engine over, or if the engine is trying to idle with big cams, the timing would jump around I'd imagine.

I can't see any other way of doing it without some complex mechanism, and thus make it bulky and not have the ability to fit in the intended location.

That said, if you could power it externally (oil pressure, electric, etc) u may be able to then control it with some other means, eg basic control module. But as said earlier, if the block/head don't have provision from factory, it may start to, again, be bulky and not fit where desired.

I commend you on your idea and hope you make something of it. Good Luck!

Edit: maybe look at something like an A/C compressor pulley. Give it 12v it locks, remove the power and it rotates. Maybe in the locked position it could be in standard cam timing, and unlocked the pulley would shift round to the retarded setting. Just a thought.

[andrew_mx83]

ac clutches only handle a couple of hp, i get mine smoking with about 5-7hp

[Supra967]

You could use a tapered dog type engagement to separate the pully from the cam shaft. Have the dog gears fly out under centrifugal force change relative position of shaft and gear. Would be strong and give you your one way adjustment, might need too much force though?

Can't see a huge market but if you focus on the right engine, and have a bolt on gear that fits inside the standard cover, you could sell a few.

[knightrous]

Knightrous, I've considered that kind of design, but in my opinion it's to big and complex and this drives costs up. My goal is to make a simple cheap design which retards the timing as rpm is increased.

If there is a merket for it, or not, would depend on how much it costs, don't you think? I have been doing some research using EAPro and typically there is a 3-5 % increase in average torque. The increase is usally bigger the further away you are from the max torque rpm, making the torque curve much flatter. I think it could be a very nice upgrade of the engine especially if one has uppgraded to bigger cams. This system would improve driveability during everyday driving, I think.

In my opinion, if your just retarding it based on RPM, your wasting your time. You really need to be able to tune this device to get the most out of it and make the effort worth while. It's why manufacturers went from on/off style VVT to VVTi designs because with more control, you can tune it to suit the power/torque curve and get more benefit.

With my pondering on this system, I was going to use the wedge ramp design as in the Toyota article I posted, but instead of the stepper motor, I was looking into using a hydraulic piston. The piston would be similar to a clutch slave, but dual acting. You would then use a control solenoid to direct engine oil pressure into each side of the piston and adjust the amount of advance/retard as per factory designs. This would only require an oil line tapped into the engine block and a few lines between the control solenoid and then the piston. A simple bracket or two to hold the piston in alignment with the wedge ramp cam gear and it could be bolted to pretty much any motor.

I was designing this as an off shoot project for my 4AGE 16V AW11, but ended up swapping in a 20V Silvertop motor with a factory VVT setup, so it kinda put it on the back burner

[091980]

Yes, of course it would have been better to have a intelligent controlled system, but then again it's cost... I have a pretty good idea of a design that might work even though it's extremely simple. I've been thinking about the kind of design you're talking about as well, but for me some of the fun in it is to make it a simple, stone age device that actually work. The guys at Toyota or any other company makes a much better vvti than I could possibly do. Regarding the retarded timing as i functon of rpm... My plan is that upon installing the gear, one would advance the base timing. If properly calibrated the cam centerline would be the same as factory while revving through the peak torque area and then continue to retard the timing a good ten degrees after that. If the engine uses a single cam gear and has the exhaust cam as a slave, you get dual vvt. retarderd exhaust cam on low rpms and advancing as it goes up. The simulations I've run on this system proves even better, at least for low rpms. But making and testing this is far into the future at the moment. But I'm saving.

One last question though... If it was made to work, and you could get the results I got in EAPro, how much would you be willing to pay for it? =P

[Supra967]

wouldn't leave it too long. Most people are going for vvti engines to start with. With price you'd need to look at the cost of getting a vvti engine to start with. It usually isn't 'a lot' more than a normal engine.

[andrew_mx83]

yup, but for older engines where its not an option there is possibly a market. i *may* have been working on this myself, keen to see what kind of pricing people would expect. being able to add vvt and estimates of around 20hp to the old school "cult" engines has to be a winner.

[Suavemechanic]

can you not get a head and a torque wrench and have a play around, my feeling is once the motor is spinning the torque to overcome the spring pressure will be fairly constant due to inertia... but i still remember " valve bounce " being a fact of life
i guess if you are good at maths there is a formula some where involving spring pressure for (one spring) times the number of active springs , less the number of " return " springs on the backside of the cam.....

[Wiggles]

can you not get a head and a torque wrench and have a play around

What if you had a head with one cam hooked up to an electric motor? The current draw of the motor should show how much load the cam is putting on it. Then just test at various speeds to get an idea of how the load increases with speed.

I'd be really interested in how feasable this sort of device would be. I'd be very surprised if it could be self powered tho, i think an external electric or hydraulic power source would be required.
I'd probably pay the equivilent of a nice set of cams for a simple on/off switch one. or a bit more for a more sophisticated variable setup.

[Sam_Q]

I don't think it's possible to do such a thing with pure mechanics, the forces involved would mean that no amount of centrifical weight that could fit in that space could hold it back.

Also there is way to independantly measure the losses of an engine to the head + water pump + alternator if you have a dyno and do a sneaky trick. I can explain if needed as it's kind of elaborate.

[Billzilla]

I don't think it's possible to do such a thing with pure mechanics, the forces involved would mean that no amount of centrifical weight that could fit in that space could hold it back.

FWIW - not quite the same thing though - there was a kit you could buy in the US for small block V8's that had a centrifugal advance mechanism, the same as was in the old points distributors but a heap bigger/stronger of course, and it'd advance the cam. No doubt it'd need a bit of fiddling to get it right though.