Adding Variable Cam Timing?

[Mac Attack]

Adding VTC on the fly like all the new cars would be a nice addition. Has anyone else considered if it was possible to do so?

I was originally exposed to it when considering my own K20A2 swap and reading about that engine design.

There's a lot of power to be gained on such an idea - Mr. Morrison actually set up a system with his adjustable cam gears allowing him to adjust timing during dyno sessions.

Just other ideas I'm considering while sourcing variable vane geometry turbos for my build.

Thanks,

Dave

 

[tof]

There might be some power to be gained but the cost per hp would be more expensive than the cost of gold per pound.

The easiest and cheapest way to do this would be to develop split timing sprockets, where clocking between an inner section and an outer section can be varried. After all, you aren't going to change the timing of the crank. And designing some type of valve train that allows modification in valve timing response without changing the timing of the cam is way hard.

So, first off you would have to engineer and build some type of split timing sprockets along with the hardware necessary to power the clocking changes. It would all be custom machined bits as far as the sprocket assemblies go.

OK, hard part done. You've only dropped between 20 and 100 grand so far if you are lucky. Now you have to throw away the factory ecu and install a stand-alone that supports a valve timing adjustment output.

Next you have to tune the ecu. Figure two or three engine rebuilds in the first few months of experimentation. Unless your hardware or software messes up enough to bump valves into pistons. Then you probably want to just replace the lump.

So you have spent enough to buy a late model low mileage Gillardo to achieve what an SOS ITB setup would net you, or about 1/4 the gain possible from a forced induction system that might run 8-15 grand.

 

[Mac Attack]

So, first off you would have to engineer and build some type of split timing sprockets along with the hardware necessary to power the clocking changes. It would all be custom machined bits as far as the sprocket assemblies go.

I'll have to get adjustable cam sprockets anyways with my build. VTC would just be on the intake side. Other Honda VTC parts could be sourced and possibly adapted since Honda puts them on almost every engine made now.

There might be some power to be gained but the cost per hp would be more expensive than the cost of gold per pound.

http://ojas.net/nsx/mirror/dal#Cam Gears

Now you have to throw away the factory ecu and install a stand-alone that supports a valve timing adjustment output.

Next you have to tune the ecu. Figure two or three engine rebuilds in the first few months of experimentation. Unless your hardware or software messes up enough to bump valves into pistons.

Yup, got an AEM Series 2 EMS coming. Piston to valve clearance will be measured when I do the rebuild, and a VTC system would be adapted to physically limit centerline adjustability to reduce the possibility of this. I'm keeping the stock CR of 10.2:1 so no huge piston domes.

So you have spent enough to buy a late model low mileage Gillardo to achieve what an SOS ITB setup would net you, or about 1/4 the gain possible from a forced induction system that might run 8-15 grand.

Thought I mentioned this will have a turbo :wink:. I'm just trying to make this engine have a lot of flexibility when doing so. It's not like I'm trying to slap a BMW VANOS, Toyota VVTL-i, Nissan, etc VTC setup on there - Honda has a design that may be adaptable.

Dave

 

[whrdnsx]

I'll have to get adjustable cam sprockets anyways with my build. VTC would just be on the intake side. Other Honda VTC parts could be sourced and possibly adapted since Honda puts them on almost every engine made now.





http://ojas.net/nsx/mirror/dal#Cam Gears





Yup, got an AEM Series 2 EMS coming. Piston to valve clearance will be measured when I do the rebuild, and a VTC system would be adapted to physically limit centerline adjustability to reduce the possibility of this. I'm keeping the stock CR of 10.2:1 so no huge piston domes.





Thought I mentioned this will have a turbo :wink:. I'm just trying to make this engine have a lot of flexibility when doing so. It's not like I'm trying to slap a BMW VANOS, Toyota VVTL-i, Nissan, etc VTC setup on there - Honda has a design that may be adaptable.

Dave

Yes, I've been curious as well about a project like this.
I'm sure its possible, I know of someone experimenting with dual variable cam timing with an RB26 GTR engine.

 

[brandonsan]

This company has already tackled this idea on a S 2000

http://www.designcraftfab.com/lates...-press-releases/79-s2000-ivtec-conversion-kit

 

[Mac Attack]

Oh cool - thanks for the link! That was 2 years ago - I'll try and contact them and do some more research.

Added 100HP/130ft-lbs in the mid range on a boosted S2000. Just what I'd want :biggrin:

Dave

 

[tof]

Well, I'm sure learning a lot from this thread. Please note that I raise issues to stimulate conversation, not to kill initiative or enthusiasm for the project.

I can see where adjusting cam timing would be even more beneficial if you are going turbo. And there is no denying there would be benefits to fitting an iVTEC like system to a normally aspirated NSX as well. The engineering just seems daunting to me.

The article you referenced was pretty interesting. And the S2000 iVTEC project is really worth keeping an eye on.

Not sure if everyone following this thread knows how the i in i-VTEC is achieved...i.e how the clocking of the cam sprockets is altered. This link provides a pretty good description: http://asia.vtec.net/article/ivtec/

As you can see, to use this approach to valve phase control you will need the following:

Cam sprockets with helical gear type grooves in the hub.
Sleeves between the cam shaft and the cam sprocket with helical gear type grooves.
Oil driven Mechanism to move the sleeve in and out to adjust cam sprocket phasing.
Control valve solenoid to manage oil pressure for that mechanism.
ECU programming and signal output to adjust oil pressure via the control valve based on engine parameters...load, rpm, etc.

That programming is the secret sauce that will be a real challenge and would require a good bit of dyno time to sort out, I would think. The other stuff is just custom machine work--expensive but doable. Not sure the AEM can generate the type of output signal that would be needed. I don't think there is a linear relationship between load/rpm and optimum cam phasing either although I don't really know. If that’s true then you would need to store a map that would allow you to look up a value for the cam phasing hardware based on input values of load, rpm, and maybe some other dimensions.

Could you use one of the AEM map functions for this? Maybe.

Just some food for thought. Good luck with the project.

 

[Mac Attack]

No problem TOF! In all honesty, I probably won't be able to pursue this until awhile from now.

Donor Honda cam sprockets would have to come from a 6cyl i-VTEC for our adaption as it would be designed for use with our belt (hopefully), and not chains like their 4cyl applications.

Just something that caught my attention and hadn't been discussed here before!

Maybe someone like Danny (lowellhigh - sp?) can do something like this with his 1000HP beast. I think he has dry sump oiling too.

Dave

 

[tof]

Donor Honda cam sprockets would have to come from a 6cyl i-VTEC for our adaption as it would be designed for use with our belt (hopefully), and not chains like their 4cyl applications.

Dave, something else caught my eye in the DAL Motorsports article:

"The adjustable cam gears are expensive for the NSX because three of the gears are different, and one of them acts as a trigger for your ignition pick-up."

One thing I am learning about the NSX...changing anything and achieving positive results is really a challange. Makes me respect the work at SOS even more than I did in my S2000 days.

 

[L_RAO]

What ever happened to DAL?

 

[L_RAO]

Yup, got an AEM Series 2 EMS coming. Piston to valve clearance will be measured when I do the rebuild, and a VTC system would be adapted to physically limit centerline adjustability to reduce the possibility of this. I'm keeping the stock CR of 10.2:1 so no huge piston domes.

Would you be so kind as to measure both piston-to-valve clearance as well as (intake) valve-to-(exhaust) valve clearance if/when you put together your motor, if you haven't done so already?

I am working on 2 separate designs that would allow me to make a big lift cam that keeps the VTEC function, however, I need to know how much clearance there is for both of those considerations.

Thanks!