Thread: Williams Helical Camshaft for SR type engines.

You are still not explaining why this could not be applied to a VVL setup. Is it simply that there is not enough space for 16 mechanisms, that is, 1 for each cam lobe?

By the way, I do hold an engineering degree. Also, most engineering degrees do not involve flow dynamics.

My studies of mechanical engineering involved flow dynamics and such

It can not be done to a VE camshaft. The system patented can only run on a single lobe height lift. Swtiching to the WHC patents would mean going back to a single lift cam.

Small gains could be had on a DE motor, but not on a VE motor. Like i have said, duration is great for high RPM and getting flow dynamics happening and chamber speeds up, but without lift - from a performance horsepower view - its near waste of time.

Right, and mechanical engineering is one of over 20 different kinds of engineering degrees, most of which do not include flow dynamics. You STILL have not said WHY these mechanisms could not be adapted to all 16 lobes of a VVL system.

Will...

Forget the idea of having a WHC on the VE head. It cannot be done. I've said above why, but you need to think outside the box.

1) There is not enough room horizontally in the head between the cylinders to accept variable duration lobes.
2) Even if the progression rate could be made tight enough, you then have the issue of the second lobe with the biger lift ( and sufficient room to provide a variable width [duration] lobe and THEN have the mean of acutating it. Keep in mind the High cam on the VVL camshaft is between both the low lobes. Changing this configuration would mean change the rocker design, changing the hydraulic locking design and replacing the rocket pivot tube with a tube having suitable oil feeds.

3) Even if we theorise its somehow possible to have both HIGH and low lobes operating in WHC style. Ignoring rocker orientation and design and just looking at the cam itself. You would have to have an inner and outer tube consisting both of WHC .You would then have to run two different base circles. To compensate for the difference in base circles youwould need to change rocker height and length, and even then your rocker ratio would be thrown way out of effective means.

I cannot see how its possible to work on a VE head retaining dual lift heights. Hope I've made it clear enough why i beleive it wont work on a VE engine with dual lift heights for you. If your an engineer, you should have figured this out already before i typed this, and im assuming youve looked at a VVL head right?

Like i have said above, this can be made to work for a DE head NO PROBLEMS. For someone who wants great torque and effiency down low not a problem - would work fantastic!

Thanks, I appreciate the thorough explanation. I have never internally examined or owned a VE head. I assumed from the beginning that is was mostly a matter of space, and had also not considered the requirement of gears between each lobe which creates the inherent interference with lobe switchover.

That's not exactly true. For those of us interested in performance, you could easily have a very high lift (and ramp up angle) and just control idle and low rpm power production with very short durations. Not sure if you'd have an issue with valve float though at the very short duration periods.

This was discussed in the previous thread as well.

Welcome to the forum Sheepdog. I can't speak for everyone, but there are quite a few people I think with N/A and turbo SR20DE engines out there that might be interested and have the money to put down for a drop-in cam that gives them lift similar to a Jim Wolf Technologies C2 or C3 cam (very aggressive race cams) but with variable max lift duration to keep idle speeds low and under control, and power production healthy at the low and mid rpm range. They might be unable to afford the money, time or effort into converting to a SR20VE engine or head (classic two-stage variable lift and duration) but could swap in cams and stiffer springs no problem (depending on price).

I don't want to get your hopes up though, we're also a traditionally frugal crowd. We like to see documented power gains (economy appeals to a much smaller portion of our base) and assurances that equipment will last many tens of thousands of miles with trouble-free operation. You'd have to determine at what durations and rpm valve float might become an issue on stock springs and certain aftermarket springs. You'd also have to determine what duration causes valve/piston collision and maintain a margin of safety there since our engines are of the interference type. Keep in mind our engines run to 7,500 rpm from the factory, and many of us like to go even higher than that.

It's a tall order for sure.

I think the design is an awesome idea, I would definitely love to see some R&D put into the SR20 for something like this. Thanks for taking the time to notice our community and reach out to us Sheepdog, I hope we are able to work closely with you guys on something like this. Cams are definitely one of the next big things on my list, and I've been reading up on all the options available to us. The hardest thing for me to get over though is the loss of torque and bottom end with a set of big cams. That's why I love the idea of what your HC cams are doing.

Thank you for your reply. What happend innitially was I was living in New Zealand at the time. I have read the whole article and was blown away with what has been documented with these cams.
As there was no contact particulars from the magazine, I have send an email to the editors of that magazine and their reply was that the vendor was merely looking at marketing these cams in conjunction with a major car manufacturer.
At no stage did they try and put me in contact with you guys and they said that I should just keep on looking for a follow up or progress wich never happend.
I would have a spare cyl head for sale very soon and will contact you when it is available
Gerry

Comments on the various points raised so far:

Lack of ability to vary lift - both I and the inventor take a fairly basic view of what cams actually do. We both consider that variable lift in a performance context really has little effect. I think the main reason that both Nissan and Honda (on the VTEC) have a lower lift on the shorter duration lobes is simply due to the fact that having more lift would not help the volumetric efficiency at the lower RPM where these lobes are being used - there being no point in stressing the various valve train components for no gain. If there is a good reason for variable lift perhaps you could enlighten us.
Remember that one of the basic ideas behind the HC is that the lobe lift need not be particularly high - having any amount of duration available basically removes the need for extreme lift.

The statement involving F1 performance and diesels etc:
There is a bit of copywriters' hyperbole here but the statement is also true(ish). The "F1" part is simply that the HC can supply enough duration to essentially match any RPM no matter how high and retain the standard lower duration. The "diesel" part of the statement refers to the possibility of controlling part load by LIVC combined with a very high CR (14:1?, 16:1?) and operating the engine in an Atkinson Cycle fashion. Any problems with detonation can be handled by lowering the compression pressure by LIVC. We have actually done both of these things - but not in the same engine. I am fairly confident that the overall fuel economy would be as good as the typical car-type diesel. Maybe not as good as the best of big truck or turbo diesels - but pretty good.

On the question of converting every VE lobe to a Type 1 or Type 2 (HC):
Theoretically it could be done (especially to the Type 1 lobe). It is a matter of complexity mainly. The main reason we are focussing on the SR engines is that only having four lobes per camshaft greatly simplfies the system. A VE would require twenty-four lobes to be converted - a DE just eight. As written above, we also think that there is little point in having variable lift. We have done cams with two, six and twelve lobes - four should not be too difficult.

Autech - your statement "Many superior models out there" - perhaps you could name a few - there actually are none at all that can match the HC.