Whiteaw57

iTrader: (2)

Because I cant sleep and have been reading I want to ask a question. I love learnign more and more about cams and the theory behind them.

My question: When someone says EPS lobes, XE lobes, XER Lobes etc. What to they mean?

I know a lobe is a lobe. theres an up slope and a down. some more agressive than others due to the base circle that all makes sense. But what about say Geoffs EPS lobes are so different than another lobe. Is it in the timing? why does it make more power?

Thanks for any responses My curiosity is killing me and I know theres far more experience out there than I could ever have at 19.

oChristiano

iTrader: (6)

I always figured it was just what the lobe was made out of or coating/finish. Probably way off though..

Whiteaw57

iTrader: (2)

I have a feeling its pretty complicated. Something to do with ramp rate and valve timing maybe

01ssreda4

iTrader: (96)

While a lobe may appear to be a simple thing, it is actually complex in theory. It pushes the lifter up, then lets it back down. You would think they are basically quick, slow, or somewhere inbetween. And while that may be true to an extent, it is more complicated then that. But, Im no cam guru, and I think lobe design gets a little overplayed around here almost ALL the time. I mean we arent talking about 1000 horse motors here. You add a 224 cam to an LS1 and it doesnt really matter which lobe its on. Some will make a little more power, some will be a little easier on valvetrains and thats great. But lets be honest, there isn't that much difference at our levels. Anyone who tells you their lobes are super friendly yet make big power, watch out....they may have something to gain. And quite frankly that just doesnt make sense. I went with aggressive lobes from Cam Motion. I dont know the lobe profile but the cam is cut very small on the base circle which naturally makes the lobe more triangle appearing at the top. I figured i may gain a little hp and torque with these. I think this is ok for me bc A. I dont drive my car very much, B. I took the time to set-up my springs properly, and C. I dont plan to ever spin my motor over 63/6400 rpms. There are guys who could probably write a book on cam lobes but again at our level of 4-500 whp, its just not that crucial.

Whiteaw57

iTrader: (2)

Oh yeah I realize were not running 120% vol. efficient race motors. curiosity just got to me. Im in the opposite boat as you however. Im running XER lobes in my DD. Every time I see a 918 thread and people saying XERs are harsh makes me cry. I enjoy the power but would love to have a less agressive cam so I wouldnt worry as much. Really more than anything I was curious why people are so over protective of lobes though. Obviously theyre important and unique. But having basically a patent on your lobe design makes me think theres something to it.

01ssreda4

iTrader: (96)

Well its their lively hood, its how they put groceries on the table. They are the same way about tuning. Tuning secrets are very protected. In your case, if your valvetrain is setup right I wouldnt worry, just pull a spring ot two now and then and have the machine shop pressure check it. Or switch over to a PAC 1518 or a dual spring. Lots of options for you so you dont worry about it so much.

Whiteaw57

iTrader: (2)

I really want to go with those lunatis like you have, Im just afraid theyll add alot of stress to the stock lifters. And yeah when I say worried I dont guess im really that "worried" I just mean Im progressively interested and learning all about the springs while im waiting to hit the 100k mile mark when I will be changing springs. That will be 22k on the 918s

01ssreda4

iTrader: (96)

Have you ever pulled a 918 and had it pressure checked in 22k? You can do 2 cylinders at a time so thats 4 springs you could take in. I'd be confident if all 4 checked out. However, there are lots of people who run dual springs on stock lifters. Stock lifters seem to be pretty damn tough. Also though, the 1518 is a great single spring and good to .650 lift with the nitride coating and would be a nice replacement to the 918s if you wanted to keep with a single.

HoLLo

iTrader: (17)

You know I've always wondered the exact thing. I made a thread on it, but 01ssreda4 was the only responder! https://ls1tech.com/forums/generatio...-question.html

01ssreda4

iTrader: (96)

The technical prowess of tech declines To think the whole website reads and believes my theories on cam design is spooky. Seriously, we have some great knowledgeable fellows here, just getting them to chime in can be like pulling teeth.

Whiteaw57

iTrader: (2)

I actually haven't pulled any springs. Whats the process for that. I dont want to leave it hooked up to an air compressor and can only obviously do one at a time that way anyway

01ssreda4

iTrader: (96)

Going by the LS-how to site, you can get 2 cylinders at tdc at one time. That means you can pull those 4 springs relating to those 2 cylinders and take them with you. The valves will rest on top of the pistons forever as long as no one turns the starter over.

dudeiwin86

iTrader: (1)

i hear you on overplayed, but its for a reason.

i have seen repeatedly (on the late model hemi platform) certain Comp Cam lobes consistently outperform Crower lobes on nearly identical cam grinds (duration/lsa).

lobe profile is not something to be overlooked.

Whiteaw57

iTrader: (2)

oh yeah good call 01ssreda4, companion cylinders.

slt200mph

iTrader: (42)

To answer your question on what are EPS, LSL, EXR, XE, ect and ect. Those are the designations for identifing the profile for specific camshaft lobes by the camshaft manufacturer. They are just the name of the particular lobe. If you look at a Comp Cams catalog you will see the different lobes and the designations (name) and the specs for the lobes.

Whiteaw57

iTrader: (2)

yeah i follow that, my question was what makes each profile different from one another

Spellbound

You would need to compare ramp rates and the durations at specific lift points to get your answer.

Whiteaw57

iTrader: (2)

awesome thats the answer I was looking for. I thought it was probably a combination of base circle and valve timing

1SLwLS1

iTrader: (6)

Well a lobe that is wider in the same spot relative to another lobe, will give you a larger area under the curve, literally (lobe profile curve). That doesn't mean the valve is necessarily open longer (depending on duration), but if you have two cams with the same duration but different profiles, the more aggressive will be open more for that point and generally overall, which gives it a greater potential to fill the cylinder, assuming all other parameters are in check.

At the same time, what is this "aggressive" lobe you are worried about mean? Indirectly, it means impact, which is force/time. If the lobe profile you are analyzing has a more aggressive ramp rate compared to another lobe, it will reach lift X quicker (less rotation of the cam) or more lift in the same time (again, depending on variables). Because force equals mass x acceleration, the force on the lobe/lifter is the same, but in a shorter amount of time (camshaft has a fixed angular velocity depending on RPM), therefore more impact and more "aggressive" the lobe is. Think about the tangent lines of a circle, the wider their intersecting angle, the more aggressive or the greater the impact the lobe/lifters will feel as that cam rotates at speed.

Whiteaw57

iTrader: (2)

ironically being an engineering student and also currently taking physics I understood all of that. Thanks for the explanation, just dont tell my teachers im using the crap ive been saying id never use