Hey everyone Compcams has a fairly new camshaft design out know (have had for a few months apparently) that is suppose to be revolutionary. I live in Northeast, Arkasas about an hour from Comp and my good friend who works there told me about them. Basically they are mad from a SOLID ROLLER profile, and are actually more aggressive than alot of Solid Rollers out there.
I copied this from comps website, everyone take a look
http://www.compcams.com/Information/...shaftFlyer.pdf
I believe these cams feature Wider Lobe seperation for decreased overlap, and making a better combustion chamber process.

Well thats all I can remember about these new cams for now.
heres an example of one of there cams
230/236 @.050, .576" intake/.570" exhaust on 113

All of these XFI (Xtreme Fuel injection) cams have more intake than exhaust lift from what I have been told and seen.

Any commets, has anyone tried one of these out yet

 

I read this board everyday and haven't seen any actual results yet. Hopefully they'll perform better than Comp's EX 3300 series of lobes.

 

Yep I have used these lobes... you have to know where and what to use them for.

Yep wide LSA means lower overlap but that doesn't make a better combustion process.

If you notice they list that 07-467-8 cam only up to 6000rpm where you could do more with that much duration if it was done another way.

Bret

 

Those cams have some extreme ramp rates. If you look at the 218/224 the lift is .570"/.568" which is considerably more than youd find in a comparable 33xx series XE grinds that are so common.

 

Well from what I have seen Some of the XFI cams that have a 235-240duartion start making HP and TQ low in the powerband Say 2500-6000. I thought it was usually the lower the Duration the more torque it provided in the lower RPM and the longer the Duration it moved the power more up in to the RPM and hurt low end Torque. The XFI is saying other wise

Myth or not, I have always heard pure duration makes power???????

The reason I am liking the XFI stuff is b/c I plan on running a Accel Superram (modified by LPE for the LT1) and I only plan on reving to say 6,000 give or take a few hundred RPM for a 396. I have 195 LT4 AFR's with a 2.05 intake valve (should flow in the upper 290's at .600) If I could run a good deal of duartion and my low end still be as power as using a small duartion cam, that would be key.
These arejust MY PERSON thoughts on how this camshaft could be used, Any input

 

Duration and lift aren't always the determing factors or ramp aggressiveness.

Cams aren't a triangle consisting of opening, closing and max lift. There are a lot of other specs that mean something there.

bret

 

Brett how do you know when you have too much lift????
From what I have seen more lift always seems to equal more power, I have looked in the Advanced Tech ( I read that forum Frequently )and good not really find anything.

 

Sure there be exceptions and/or other aspects, but by and large, apppes to apples, to get from point A to point B, I agree, it will require a given amount of, as Brad put it, 'ramp rate'. For a street driven engine, there is but a limited number of choices available, in respect to complementary parts, to control a given ramp rate, unlike a pure race engine.

 

There's a number of aspects to this. One of the basic things to consider are flow numbers. Beyond a certain amount of lift, which varies with the valve size among other variables, there is no gain from additional lift per se. However, for a given advertised duration, more lift is also usually associated with greater duration at the middle of the lift curve. Hence more "area under the (lift) curve" and the potential for more power. Increasing lift up to the point where the flow peaks is good as well as getting there faster, all provided the valve can be controlled. An "ideal" valve lift curve might be "square", nearly instantaneously opening the valve to the point of max flow and then instantly closing it at the desired points, but there is no way to achieve this with cams, springs, rockers, etc. The limitation of very steep lobes is controlling the valve and other reciprocating valvetrain parts. This is reflected in the problem with getting the XE and similar lobes to rev. If the rest of the parts aren't right, they will not perform up to potential.

Rich

 

Random thoughts:

Maybe not. The air or mixture has inertia so it takes a while to get it moving. It accelerates to it's max port velocity and as the valve starts to close, the mixture doesn't decelerate as fast so it crams itself into the cylinder until the valve gets close to being shut, especially if we have the correct intake port length for best inertia tuning.

A "square wave" opening should cause a large spike in (low) pressure which might try to overspeed the mixture or at least cause turbulance or very high velocity. With Mom Nature forcing us to have a gradual opening of the valve, I picture the velocity profile of the charge shaped something like the opening portion of the valve lift curve, but lagging behind it and skewed.

As to closing rapidly, that makes more sense; we can cram more mix in with the correct port tuing. Asymmetric lobes tend to do this because quick closing is easier to achieve.

If the valvetrain dynamics would allow it, perhaps opening the intake as aggressively as we do now, then dwelling it at max lift or maybe max flow lift, then virtually slamming it closed would be good. A rapid transition to and from dwell and the associated accelerations (forces) drive the springs crazy. I wonder if pneumatic (Like F1) springs might work with this lobe? I believe there are ways of shaping the force curve of a pneumatic spring, even at 20,000 rpm cycling rates.

 

Yeah, that was exactly the "might" I was thinking of. My post was a gross oversimplification anyway. But I think that with an OHV setup we are far from opening the valve "too fast" at this point.

Rich

 

Arnie you would be suprised as to what lobes have a aggressive ramp rate and which ones don't. I would say that the relationship of the .200 duration to the max lift and .050 duration has more to do with the ramp rate than the relationship of the max lift to the .050 duration. The .050 duration and the advertised duration say a lot about the ramps as well.


You have too much lift when you use the coil bind of the springs to stop loft of the valve like in Pro Stock.... their lift calculated out equals about .990" or so but the actual valve lift at high RPM is about 1.100". They only can do that because of spintron machines where they can watch the valve motions at high RPM.

Basically lift is determined by spring life and by spring specs..... Other than that you get the motor as much lift as it can handle even if the port stops flowing more air at higher lifts and the port goes into "choke"

Max lift is not determined by where the heads stop flowing, it's determined by the airflow demand of the engine...

IMHO you can never have too much lift on anything.

Bret

 

Hey Brett, My buddy at comp told me If I run the XFI cams with my setup that I am shooting for 396, 195 AFR's, etc I will have to change springs out say every 2-3 years just to keep sure that I don't have spring failure. I have 1.7 RR's for my setup as well I now most people say .600 is the max you should go with a street car,but My buddy's LS1 has a .603,.608 lift on a stock headed car and makes 393 RWHP. I would think a 290-300 CFM head at .600 lift would really benfit from a higher lift, I know the valvetrain would have to support it, Mostly the springs though, correct. I also thought of Sar2k's car, he ran a 250 MAX CFM head matched to a big Duration cam with a tad over .600 lift in an auto and made 450 RWHP.

I would like to run a Low duration XFI 228,228 (with ported Superram)with 112 LSA a .610, .610 lift with 1.7's. LIgenfelter loves using low duration cams with high lifts, Just like his 219, 219 with a 112 LSA .560 .560 lift cam with a superram. I suppose the superram likes a single pattern cam setup

 

Hey Bret,
with the emphasis in my quote on "apples to apples' and "limited number of choices available, in respect to complementary parts, to control a given ramp rate", I was attempting to note, it was my impression, the XFI series of lobe to be a more aggressive version of the XE series, having more velocity ground into the lobe. If accurate, I figure it comes down to the practical limit, or IOW, how radical a spring is permissible on the street to control this lobe, if indeed a hydralic is even practical. There comes a time, when you'd be better off using solids, accompanying springs/components, and be done with it.
If not accurate, and the lobe is indeed a radical departure in design, from previous XE series, with increased velocity, but with advancements in acceleration (or whatever), thus permitting a similar spring spec, I am then in error, and stand corrected.
As you may have misunderstood me, you felt a need to qualify the lobe design, as one that is not of a linear ramp. My error, as I did not mean to imply such, with my use of the catch all term, 'ramp rate'. What you posted above, I believe I have seen posted before, possibly on this site.No, but when compared to the XE lobe, are they in this case?

 

The XFI's are designed to work with more rocker ratio AND a lighter mass spring like a beehive. So yes in terms of a total system they will work better at valve control. They are LESS aggressive than the 3300 XE series of lobes and are on par with the 319X series of lobes, which are a higher lift series. They (XFI) have more lift per deg of duration but have a lobe that controls the valve motion much more accurately. The exhaust lobes are less aggressive than the intake lobes in this series also.

That help?

Bret