FMS cam specs......coming soon

[blkfordsedan]

No problem, LOL. For those of us "optically challenged"...

[zoom zoom]

Any chance I could get you to also host the pic on an external server, like tinypic or Photobucket? Ff.com shrinks images to a point I can't read the numbers, and I'm not an old man, I have 20/20 vision.

[blkfordsedan]

well!!?? we want the specs!!

also, as an alternative, i'll run this cam in DynoSim5 and we can compare results.

for the test though, i'd like to know what you're using for head flow numbers so that i can use the same numbers in my program.

Specs were attached to the post......should have been the second picture, which is a scan I did of the spreadsheet. When I get home I'll pull up the air flow file I'm using. It's just a guess, since no one really knows the actual head flow (that I'm aware of).

[FestYboy]

well!!?? we want the specs!!

also, as an alternative, i'll run this cam in DynoSim5 and we can compare results.

for the test though, i'd like to know what you're using for head flow numbers so that i can use the same numbers in my program.

[blkfordsedan]

For those of us who like to play around on Desktop Dyno, you will enjoy playing with this. If you enter in the seat-to-seat timing figures, it will be instantly obvious that such figures are meaningless. The program must assume somewhat of a standard lobe profile (probably based on accepted lifter acceleration and velocity rates of an OHV V8. Since the seat-to-seat values represent such a large duration cam, the power and torque estimates are terrible.
HOWEVER..........enter in the valve events I have listed at .087" valve lift for the ".050" parameters and it's a different story! The torque curve is almost flat from 2000 rpm to well past max HP. Even using the .0325" figures under the .050" parameter gives similar results. You will also notice that advancing the cam 4* not only results in a boost in torque, but in max HP as well.

[blkfordsedan]

Drum roll.....................

Before we dig into this any deeper, there are a couple things we need to place in context.

FIRST: OHC "follower" type cams play by different rules than the traditional OHV V8 design. In the OHV design, you have the lifter that is captured by the lifter bore in the block. The lifter can only travel in one plane, and it's contact point with respect to the centerline of the camshaft never changes. This makes measuring and mapping an OHV camshaft relatively easy. The stylus of the dial indicator can be positioned on the pushrod, or in the pushrod seat of the lifter, and measurements can be derived with a minmum of geometrical error. A .050" lift at the tappet (lifter) equates directly to a .050" lift at the pushrod end of the rocker arm. The rocker arm ratio does not come into play except for measuring maximum valve lift. In the case of the OHC "follower" design, the cam lobe acts directly on the pad of the rocker arm. The lobe ramp makes contact with the follower pad on the leading edge and continues across the face of the pad until exiting at the opposite end. The contact area changes in relation to the rocker arm shaft (pivot point). The result is a variable rocker ratio.....from high to low or low to high....depending on if it's the Intake or Exhaust (which are on different sides of the cam).

This makes it extremely difficult to measure duration at a given value of lobe lift and be able to correlate it directly to the "standard .050" value that we use on OHV V8 engines. You can not get a good reading by setting the dial indicator on the rocker arm, since the motion of the rocker arm pad is in an arc, which introduces geometrical errors as well. Running the dial indicator directly on the cam lobe can be used for determining duration, but there are two problems with this method:

A) The lobe profile geometry does not correlate to that of an OHV lobe.
B) The valve timing events can not be accurate. They change, depending on the angle and position on the cam at which you measure.

Because of this, most measurements were taken on the face of the valve (from the combustion chamber side). To derive the duration and timing events at ".050" lobe lift", I converted it to .087" valve lift, based on a constant rocker arm ratio of 1.75:1 which is the ratio at max valve lift. This is not 100% accurate, but I figure should be pretty darn close. I spoke with Engineers from both Crane & Comp Cams this morning, and they confirmed my theory and method.

I also found that Sealed Power advertises their stock replacement cams as being 205* duration at .050" lobe lift. When I measured the stock cam, I found that I had to be at ~.0325" valve lift to achieve 205*. For reference and comparison, I measured the FMS cam at .0325" valve lift as well. I also took measurements for "seat-to-seat" and .004" valve lifts to represent what is commonly listed as "advertised" duration......which means absolutely nothing. Which brings us to....

SECOND: Duration without any kind of lift specification at which it was taken means nothing. Lazy lobe ramp angles, especially at the transition from the base circle, have a huge effect on "advertised" duration with little effect on actual flow. Comparing the seat-to-seat duration and .050" duration can give you good indication of how aggressive a cam profile is. The point is this...do not judge a cam's performance based on "advertised" duration. For a detailed explanation, you can follow the link I gave earlier in this thread.

[yelo festiva]

neat

Can't wait for spec's. I have one of these to put in yelo when I get a chance. Roger never did email the spec;s to me when I got the cam. I have heard good reports on the increase in power without loss in fuel mileage.

I appreciate all the research you have done on this!

[kellen302]

^Cool, I was just going off what I read in an issue of HOT ROD awhile ago

[blkfordsedan]

Actually, I finished every thing up Friday afternoon. I have a spread sheet with tons of info, but I couldn't attach it to my post. I don't have internet at home (just my Blackberry) so I'll post everything up on Monday. There is some explanation that needs to go along with the results to understand it. I also wanted to play around with Desktop Dyno before I posted as well.
In addition, I want to talk to an Engineer with Crane or Comp about the design of OHC follower style cams. They appear to have some strange things going on in terms of geometry and I want to make sure I have the correct measurements.
I've never looked at the Thumper cams, but it would be the overlap that gives the choppy idle. That can be accomplished by having close lobe centers, even with relatively short duration.

[kellen302]

We need one of them Thumpr Cams.... the roar of 1.3L of angry Korean Fury
Edit* The Thumprs just have bonus Exhaust duration I believe

[DriverOne]

Final results should be up in the next few days. Right now, I'm checking out the factory camshaft for comparison. The final specs on the FMS cam will be slightly different than I posted earlier. I got it figured out now and I can explain why, but it would only put everyone to sleep. I'll save that for the final detailed post (consider this fair warning, LOL).

I eagerly await your findings!

[blkfordsedan]

Final results should be up in the next few days. Right now, I'm checking out the factory camshaft for comparison. The final specs on the FMS cam will be slightly different than I posted earlier. I got it figured out now and I can explain why, but it would only put everyone to sleep. I'll save that for the final detailed post (consider this fair warning, LOL).

[Movin]

It also allows you to look at your motor and know if it is in time or not
without crank or cam marks.

[blkfordsedan]

Very interesting stuff here man, I don't know what any of it means, but its cool to read about!

+1 no idea what he is talking about

Now is a great time to learn! Here's a link to one of the better sites i have found that is devoted to camshaft design & theory. It covers all, from basics to lobe profile design and calculations.

You don't need to understand the really technical stuff, but it helps to understand the basics. Like getnpsi said, there is a reason that you can buy of 100's of different camshafts for an engine (at least popular engines). Each profile has a different effect on the dynamics of the engine and needs to match all other aspects of the engine such as head flow, bore, stroke, rod length, compression, operating range, etc.. Understanding the basics allows you to choose a camshaft that is optimum for your application.

http://tildentechnologies.com/index.html

[getnpsi]

I know what I know for only a few engines by comparing features, watching others waste money and change combos etc. . Now airflow of the entire head dictates if a cam with different values is going to hurt or help across the board. Losing torque is a terrible idea on a b3 less bad with a b6 acceptable with a 1.8 and also with boosting,as you can change sweet spots all over the place. I do have curiousity on the specs if there was custom cam market showing itself.