Hi-Po camshafts

[The General]

I’ve been looking at the dyno plots for the new SOS stroker kits and they’ve got me thinking about camshafts, VTEC and how the NSX engine flows at high RPM. All the stroker dynos show a sharp drop-off in torque starting at about 6000rpm (http://www.nsxprime.com/forums/showthread.php?t=85793.) A number of posters seem to have noticed this, and a few quick calculations show that if the torque curve could be maintained all the way up to 8000 rpm, the power would easily exceed 400hp at the crank.
Headers, head work, ITB’s and high flow exhausts can all help to open up this top end a bit, but what is really needed up there is a more aggressive cam setup. In theory VTEC should provide this for us, but let’s look more closely. Stock cam VTEC lobes are only 230/10.3mm (duration/lift) on the intake and 225/9.0mm on the exhaust. This is really not all that aggressive when compared to other high performance NA motors. SOS sells a cam designed for high performance NA motors that improves upon this at 271/10.7mm and 258/9.9mm. However, even this is not that aggressive. Heck I know people who run 290 duration cams on bmw m50 straight 6’s. That is a non-VTEC motor too (i.e. the motor runs 290 duration from idle on up). It seems like one could run really wild VTEC lobes and not sacrifice idle or drivability.
TODA advertises a cam that runs 295/12.5 VTEC lobes!!! This would seem to be the ultimate ticket for opening up the top end on the NSX engine, but nobody seems to have them. I realize they would probably require custom pistons to address the valve/piston clearance issue, but if one were doing a 3.6 or 3.8 liter motor, this would already be on the agenda anyway. Is anyone on the site running these cams or even seen them in person? Anyone have any thoughts on modifying the NSX valve train in general? Thanks and sorry for the long/rambling post.

 

[Swift]

Highly interested in any responses too on this...or video!:biggrin:

 

[satx]

ttt for a great post.

 

[David]

As I have pointed out before, the heads flow very well with a decent valve job, so the restrictions are clearly the stock intake mani and the cams.

The limiting factor on the cams is valve-to-valve clearance. I had several discussions with Bisi Ezerioha and one with Web Cam about custom cams and I don't think you are going to get much more aggressive than the bigger size cam SoS sells. You might get a bit more duration at moderate lift, but they are close to the limit on total lift.

Toda advertises more lift on their "spec c" cams, but I know several people who have measured them and say it is considerably exaggerated.

My .02

 

[NSX 3.0]

I’ve been looking at the dyno plots for the new SOS stroker kits and they’ve got me thinking about camshafts, VTEC and how the NSX engine flows at high RPM. All the stroker dynos show a sharp drop-off in torque starting at about 6000rpm (http://www.nsxprime.com/forums/showthread.php?t=85793.) A number of posters seem to have noticed this, and a few quick calculations show that if the torque curve could be maintained all the way up to 8000 rpm, the power would easily exceed 400hp at the crank.
Headers, head work, ITB’s and high flow exhausts can all help to open up this top end a bit, but what is really needed up there is a more aggressive cam setup. In theory VTEC should provide this for us, but let’s look more closely. Stock cam VTEC lobes are only 230/10.3mm (duration/lift) on the intake and 225/9.0mm on the exhaust. This is really not all that aggressive when compared to other high performance NA motors. SOS sells a cam designed for high performance NA motors that improves upon this at 271/10.7mm and 258/9.9mm. However, even this is not that aggressive. Heck I know people who run 290 duration cams on bmw m50 straight 6’s. That is a non-VTEC motor too (i.e. the motor runs 290 duration from idle on up). It seems like one could run really wild VTEC lobes and not sacrifice idle or drivability.
TODA advertises a cam that runs 295/12.5 VTEC lobes!!! This would seem to be the ultimate ticket for opening up the top end on the NSX engine, but nobody seems to have them. I realize they would probably require custom pistons to address the valve/piston clearance issue, but if one were doing a 3.6 or 3.8 liter motor, this would already be on the agenda anyway. Is anyone on the site running these cams or even seen them in person? Anyone have any thoughts on modifying the NSX valve train in general? Thanks and sorry for the long/rambling post.

Try giving King a call they sell Toda maybe they can help.

http://www.kingmotorsports.com/category.aspx?cat=5

 

[The General]

I appreciate the responses. So it is sounding like truly wild cams for the NSX may be a myth? Anyone know what the jgtc guys are running (though I am sure it is w/out VTEC)? So piston to valve clearance can be accounted for (with dished out pistons), but if valve to valve clearance is the limiting factor then I guess there really isn't much that can be done.
I just seems like an awful shame to have a system as ingenious as VTEC and then not really be able to take full advantage of it because of the dimensions of the cylinder head design. I mean, one could easily run the kind of cam profiles the SOS cams use for VTEC lobes all the time (i.e. without VTEC). Granted, VTEC still improves the overall torque curve, but the real advantage of VTEC, to me, has always been that it gives you the ability to run wild, race-spec cams up top, and civilized, normal-idle cams below 5800. Anyone know of any companies other than TODA or SOS that make NA cams for the NSX? Anyone actually have the TODA cams?
Now you guys see why I don't post that often, I can't write a sentence without writing two paragraphs:wink: .

 

[David]

Revolution makes/made cams that were used in a lot of the fairly modified NA Japanese street cars. But any of the Japanese cams will cost as much or more than a custom set from Web.

 

[greenberet]

Comptech used to sell camshafts for NSXs and described them as follows:

"Only the V-Tech lobes are redesigned. They are first welded with a hard face overlay and reground increasing valve lift and duration while retaining the stock base circle. This keeps the valve geometry stock for best valve life and a smooth transition from the low lift valve to the V-Tech valve."

When I asked what the specifications of the V-Tec cams were and who did the work for them, they wouldn't say. I bought a set anyhow and assumed Web Cam or Crane Cams carried out the work to Comptech specs.

In case Comptech are not selling the camshafts anymore and you can get a hold of someone in the know, they might be more talkative now. Or maybe Shad at Driving Ambition could help out.

 

[L_RAO]

I thought I'd chime in with my camshaft research up to this point:

Cam Lift (VTEC)
The most lift that can be achieved on a stock cam (regrind) is 0.420" (10.67 mm), due to the small base lobe of the cam - which is still very mild considering there are now 15 mm lift cams out there for the K-series.

Assuming the clearances (piston-to-valve, and valve-to-valve) are there, 12.0-12.5 mm lift (my ideal #) can be accomplished by a couple of methods:

Hardwelding
Pros: Gets the lift and duration we are looking for
Cons: Uncertain long term reliability, expensive ($3800/set)

Having new camshafts made
Pros: If properly produced, should have OEM qualities with respect to durability
Cons: Very expensive initial outlay (I have found one cam manufacturer that would do it, but would require 25 sets be pre-sold - Group Buy anyone?)

There are some other routes I'm "imagineering" right now, like converting to K-series roller rocker arms and having billet roller cams made, but it all takes time, money, and more engineering capacity that I have. But, it's been very enjoyable up to this point and I've got some very good people helping me.

 

[greenberet]

I agree that new pistons with deeper pockets could overcome any valve to piston clearance issues we might have with higher lift camshafts. Deeper pockets would create a less smooth, more fissured combustion chamber but it if allows more lift, it might be worth it.

I think we may have more of an issue with valve-to-valve contact because the intake and exhaust valves have about a 60° included angle between them in an NSX cylinder head. That will limit how many mm both can be open at the same time before they hit each other. Since there is a limit to how fast you can open and close the valves, a limit to the overlap you can run may also limit the duration and lift you can effectively use.

It would be good to get an NSX cylinder head to a camshaft designer to discuss what the wildest cam profiles are that could practically be used given the limited overlap possible if valve to piston contact were a non-issue. With stiffer springs the valves may be able to open and close more quickly and with roller followers, that may not result in increased friction and decreased valvetrain life. That could be interesting.

Regarding the cons of hardwelding, both Web Cams and Megacycle Cams offer new billet camshafts as well as hardwelded camshafts. Web Cams says,

"We believe that our hardwelding process is the best option in extreme racing conditions. We offer billet cams for people that do not want to send in their stock OEM camshaft for welding, and are not demanding as much from their engine."​

“Our nickel based hardfacing alloys … greatly enhance the erosion and abrasion resistance of our hard weld parts. ... The overlay’s natural lubricity and their resistance to gauling coupled with these low RMS finishes mean less wear on both our cams and your mating surfaces. These are the finest camshafts available.”​

Megacycle Cams says,

“Cam lobes are subjected to high surface stress and impact loading—and to severe frictional wear in all applications except those using roller followers. The best material to withstand this combination of loads is a nickel or cobalt based hard surfacing alloy. One of these alloys must be welded to the lobe surface only (as they are not suitable for use in the body of the camshaft). The hardfacing may be applied to a new steel or iron billet at add wear resistance, or it can be applied to a worn stock cam which has been properly prepared, thus providing additional grinding stock for high-lift profiles. … The result is the most durable (and often the most expensive) cam lobe surface available.”​

So that sounds good. I’ve had Comptech’s hardwelded high-lift camshafts in my engine for about 100,000 miles now and the reliability has been perfect.