Lift Curve Comparison

[Indycars]

It seems that the numbers provided by the manufactures are limited in the information that they provide and going by the application description (see note 1 for example) this leaves alot to be desired. Exactly how do they come up with the power range or cruise range see below (3600-4400 cruise RPM) or the converter stall speed needed??? Ask ten manufacture's and get ten different answers. Two cams could have exactly the same duration, lift and timing numbers, but be completely different cams.

Wouldn't the lift curve provide another very good tool for evaluating the different cams. But I don't see the manufactures providing this info....right??? Is it available somewhere??? That would be like showing the world your research data. But that doesn't mean we can't do our own lift curves. I would guess that you already have some data if you would be willing to share.

I would like to see what I can do with Excel plotting these curves and putting some on them on the same graph for heads-up evaluation. If you have some data, say every 5 degress vs. lift that you can provide, then I would like to see what I can do. Everything I find out would be provided here on the forum for everyone to use.

Comments???

Note: Example - Crane 119661 - http://www.cranecams.com/pdf/_catalogs/ ... 54-107.pdf Page 68
1.) Good mid range torque and HP, fair idle, performance
usage, 3600-4400 cruise RPM, good with manifold
nitrous system, 10.0 to 11.5 compression ratio advised.
Good w/Roots supercharger, 15 lbs. maximum boost
w/8.0 maximum compression ratio advised, .900” base
circle for long stroke clearance.

Lift Curve Example:

 

[grumpyvette]

when a manufacturer posts a cams designed cruise or power and rpm range, hes obviously not able to know the application,youll be using it in.
so they generally assume a standard and more common displacement and that youll use parts that will commonly be selected for the application, or they will post some info, stating the cams designed for , lets say 11:1 compression or it will require a 5000rpm stall or other useful info to help you narrow your search, they will generally start with a small block chevy, assume its to be used in a 350-383 displacement, and assume its to be used with a single 4 barrel carb as thats the more common range.
obviously if your building a 427- sbc, or a 302 sbc the displacement and heads and rear gearing etc. needs to be factored into the cam selection process.
in most cases a discussion with the cam manufacturer will help clear things up, but remember some cam manufacturers tend to be focused more on long term engine durability and high rpm valve train stability,rather than looking at MOSTLY at peak power, potential, some concentrate more on maximizing power and pushing the extreme edge of the physical limits on the valve train,stress levels, under the assumption that making a few extra hp, is more important than making the components last longer under the idea that any race engines going to be inspected and refreshed far more frequently.
the more conservative designers figure you need to Finnish a race to win a race and most builders and owners don,t want to constantly be replacing components.
as your engines displacement, compression ratio, port flow rates and other factors, change the objects usually to increase the air/fuel mix volume thats flowing thru the engine and increase the number of power strokes per second, thus its assumed the average rpm range will need to be increased and the low rpm volumetric efficiency is sacrificed, to increase the upper rpm power.
now it should be obvious that a roller cam can be used to provide more lift under the valve lift curve than a flat tappet design, due to simple limitations due to the cam lobe clearance and base circle limitations in most engines,but keep in mind the port design and valve size have a big effect on flow rates
Isky claims that the Comp XE cams violate the 47.5% rule. The 47.5% rule applies to flat tappet cams for SBCs with 1.5 rockers but the concept is still the same for other configurations where the designs are "on the edge" or "over the edge" for lobe intensity. For 1.5 ratio SBCs, the duration at .50 must exceed 47.5% of the total valve lift or your asking valve train problems. For example, take a Comp Cams Magnum 280H, with 230 duration and, 480 lift...230/.480 = 47.9% which exceeds 47.5% therefore would not pose a threat to components. We do not regularly hear about the older, safer HE and Magnum designs rounding off lobes anywhere near as often as the XE cam designs. Unfortunately, some of the Comp Cams XE dual pattern lobes break this 47.5% rule on the intake side so they are likely to be problematic. The design has "steeper" ramps that are too quick for durability and reliability according to other cam manufacturers. They will wipe lobes in a heart beat especially if you have not followed the proper break-in procedure. Other designs are more forgiving during break-in and less likely to fail.

read thru these threads

http://www.idavette.net/hib/camcon.htm

viewtopic.php?f=52&t=2627

viewtopic.php?f=52&t=2782

viewtopic.php?f=52&t=322

viewtopic.php?f=52&t=112

viewtopic.php?f=52&t=480

 

[Indycars]

Grumpy,

I was hoping to get data from users like yourself from when they installed a camshaft and recorded LIFT data every 5 degrees. From that I would use Excel to plot the lift curve and be able to compare different cam families from within the same company and from different companies. I'm interested in looking at how aggressive the cam accelerates the lifter/valve.

At first it would be to see if I can get Excel to do what I want and overlay different lift curves on top of each other for comparison. Once I had the process figured out, then more data would provide more curves.

 

[grumpyvette]

sorry I don,t have that info on cams, because Ive never felt it was worth recording, because you really can,t change it other than by swapping cams but Ill look it up if I can.
one factor I will mention is that each manufacturer tends to look at durability, ramp speeds and max lifter acceleration very differently, one reason I tend to prefer CRANE & CROWER is that they both company's in general realize the engine must finish the race to win and a busted valve train is a HUGE problem,they both realize, and design valve train components and cam lobes with DURABILITY and reliable valve control as top priority,s that are far more important than squeezing every possible potential HP from a cam lobe design at the expense of long term durability

Comp has several lobe families for the LS motors. You can even use some non-LS lobes for this motor. Here's a quick list:

XE - mild lobes but still used mostly on the exhaust side.
XER - More aggressive than the XE lobes and still the most widely used lobes for the LS motors.
XFI - Even more aggressive than the XER lobes, starting to gain popularity. Has separate intake and exhaust lobes.
LSK- Ultra aggressive lobes, not so popular.
LSL - Pretty much the same lobes as the LSK but with different lift rate.
LSR - Not a lobe family, but a compilation of popular custom cams ground on the LSL lobes.
Thumper Cams - For those wanting the "choppy" cam sound (tigher lsa).


crane
http://www.google.com/search?ie=UTF-8&o ... be+library

http://www.motionsoftware.com/lobeprofilelibrary.htm

http://www.motionsoftware.com/Dynomation5.htm


cam analyzer software
http://performancetrends.com/ca20.htm

http://www.auto-ware.com/software/eap/eap.htm

I think what your looking for is best served with this software.

youll obviously want some tools, and read thru these threads
viewtopic.php?f=52&t=90
viewtopic.php?f=50&t=3157&p=8449&hilit=dial+indicator#p8449

 

[Indycars]

sorry I don,t have that info on cams, because Ive never felt it was worth recording, because you really can,t change it other than by swapping cams but Ill look it up if I can

Once you bought the cam, then you're right you can't change most of the numbers. But this would help to evaluate the cam before purchase, to get an idea how aggressive the lobe design is or to compare against another brand. To also see how the area under the curve compares between two or more cams. Just a thought, but if you haven't recorded the data, this would be a long term project before there was much data to compare with.

The data would be obtained when someone installed the cam and was in the process of degreeing the cam in, one would have to record the lift every 5 degrees.