Dulimon

Good evening Spin…what is the characteristics/curves comparing this cam to others you have suggested? You have put out proven cams with drivability/power but would you mind giving info regarding RPM operating ranges or to a degree simplifying? Nothing specific but similar to what most of us are use to viewing when looking for a cam such as RPM operating ranges, Valve to piston interference, compatible A6 or M6, Street or low torque to Street/Strip applications and preferred gearing/stall.

Examp.
1800-6200 RPM LSA, Street/Strip, A6/M6, Stall speed, Gearing, LS# V/P contact issues, ect..

Most entry level modders when looking on manufactures web sites look for basic info to start...granted there is still a great room of consultation but it gives them an idea to start. You give good specs but most have no idea regarding how lift, duration, LSA, ICA etc interacts with the intake, heads, compression and headers. I know you have several good posts explaining cams and have addressed some of the above questions but to some they just might not get it and some basic info would help many and perhaps save you some late nights.

SpinMonster

You have to understand that the combo you use the cam with greatly changes the result. You also need to understand that I'm not selling cams and cant possibly run through every combo such as the intake manifold used. A stock LS2 unit peaks at 5800rpm and the FAST 92 forces a peak at 6300rpm. This cam has been installed in various configurations and all of the results say it pulls to 6800rpm. Low end results will vary with header size and compression with up to a 30rwtq difference at 4000rpms.

I answer 98% of the PM's I'm sent but the 40+ a day is now closer to 50 asking for install geometry and I have to at some point put the responsibility of build specs on the guy you hire to install the cam.. If you dont know these things its too adavanced a project to DIY and the final liability of checking for install p/v clearance, Spring installed height, and cam grind verification is the liability of the installer. No one takes on liability like that if its not his business income hence why you get paid to do a full install geometry. Asking me for pushod length and installed heights on XYZ milled heads with comp R lifter with RST gasket thickness is a bit involved. I need to get through all PM's in about 1/2 an hour.

Much of what you are asking is already covered in this thread and other threads including info on auto cars. It isnt compatible with a stock stall due to its min idle speed which will in most cases be over 800rpm and closer to 900rpm.

Its use at the drag strip is covered in other threads if you search. It traps 129 in a stock LS3 headed car. The title of the thread is 501rwhp with great driveability.

http://forums.corvetteforum.com/c6-t...ivability.html

The search button is your friend.

Dulimon

You are a busy man...thank you.

MrDrezzUp

On top of all the PMs, Spin also has a crazy guy from Canada calling him.

Spin's willingness to so unselfishly spend his time and energy helping so many people is amazing.

Jay J

Which cam's are best for a Daily Driven LS3? Something that can also pass emissions?

SpinMonster

Emissions; another reason to avoid big splits/overlap.

I think this cam will make it. 4 degrees overlap. Since lots of people say it drives fine, its a great daily driver cam.

My 228/232 114 passed the sniffer in NY and that was 2 degrees overlap. You can make this one a 2 degree overlap cam by going with 230/234 115+3. Still peaks about the same rpm.

jdwk

Is it possible (or maybe it's already done) that lobes are shaped steeper on intake valve opening and exhaust valve closing, making more area under the curve while minimizing overlap. So even with 4 degrees of overlap, it's not really overlapping that much volume. Actually, you'd probably want both sides as steep as possible to maximize the area under the curve.

I wish you could get a plot of valve lift for a cam. I know there's some software out there, but I don't know how it would factor the actual lobe shape without a very high resolution cam file which I would be surprised any shop would give.

Also, I am little confused at how overlapping allows and benefits from higher compression. When the intake charge is actually compressed, both valves should be completely closed, unless you had some ridiculous durations and separations.

The only real benefit I see to overlapping is the longer durations that cause it. The longer durations will be more likely let charge out during the compression and power strokes, thus lowering your actual compression, but also lowering the amount of pressure on the piston.

I think in a perfect world, you would want the intake valve wide open from TDC to BDC on the intake stroke, and closed completely for compression and power, and similar for the exhaust side. Unfortunately, the valves can't travel instantaneously and we are forced to sacrifice some of the pressure to get enough air in and out to make power.

The more I learn about internal combustion engines, the more I think there is room for improvement, but we'll most likely all be driving with batteries before automotive technology allows an ideal engine.

jdwk

Stupid interwebz, double posting.

HC Mechanic

Nothing personal...but keep learning, we are pretty close to ideal already.

Ragtop 99

Yes different lobe families ramp up at different rates so those are available, they just need better springs. Most of the .600+ lift lobes are fast rate. Spin has suggested the faster rate lobes when he lists "XFI" for example.
You can compare lobe rates by visiting Comp's website. In addition to the .05 spec being discussed here, they will list the duration .006 and .200. Combine that with peak lift and you can get a good feel for which lobes are faster and which have more overlap above .050.

Many shops provide cam doctor data when you buy a cam from them to verify that you got the cam you ordered. Valve events can be fairly guarded secrets by many shops, but off the shelf lobe profiles made by comp cams and others are not.

You can try searching for "cam doctor graphs" or "cam doctor results" (or similar terms) on this forum and C5 tech; maybe you'll find a few plots, or at least the data at .05 and every .1 thereafter. I've seen them posted, but not recently since most of the lobes discussed have been out for a while.

Overlap bleeds off compression so the more overlap a cam has, the more you need to make up for it with higher static compression. All cams have overlap and without it an engine would make far less power. I'm struggling to interpret your points, but I think you are missing the fact air has inertia and it needs to keep it moving and the higher the rpm, the more overlap can help that process. Anyways, it is beyond the goal of this thread which is practical application within a fairly narrow band of overlap, at least as measured at .05.

Hope this helps.

sxeC7

Overlap is the reason racing engines with 13:1 or higher compression can be readily started and have to idle at 1000 rpm. With a big overlap cam much of the compression is bled off by the large overlap of the exhaust valve closing and the intake valve opening. This, also, dilutes the incoming air/fuel charge with exhaust gases and the reverse for the exhaust which reduces low rpm power. To offset some of the loss, the compression is increased. As the rpm increases the interia of the gases takes effect and the longer valve open event creates better cylinder filling thus building greater power.

BrianH

I've got about 50 miles on the C6 with the 230/234 14+2.

Along with kooks 1 & 3/4 catted, airraid, 180 therm, hptuners, the cam I was able to put down 485/445 on a safe tune. I was able to get higher numbers, but I didn't want an aggressive tune on the car, at least not on a tank of winter gas that's been sitting four months. We'll see what happens when summer comes around.

As far as first impressions go, I couldn't be happier that I chose this route. I was originally really worried about doing a cam, I've seen it ruin great cars and I'm pleased to say that this did just about nothing to my car aside from add some power =D Through hte cats and the stock exhaust the note is very quiet, but sounds very mean when you get on it. The car drives great and isn't far off from its stock manners. . . I'm very pleased that I took this route.

duff70

on the 230/234 114+2 cam, what rpm did you set your idle at ?

bosco 08

I would really like to see your set-up if you can spare the time. I can come to you or you're welcome to drive to Montgomery. Thanks.

BrianH

Pming you.

bosco 08

Thanks for stopping by your car looks and sounds great.

SpinMonster

The most recent forum meber result with this cam got 504rwhp/461rwtq.

8850

Great numbers if it would only work with the auto tranny. With my stock converter it only likes to idle about 600-650 rpm before it's pulling a little too hard for my liking. I'm afraid that 224/224 at 700 might be a tad fast for everyday driving in traffic.

rskrause

Anyone care to comment on this cam for a 421ci LS3 stroker in a light car? Static CR = 11:1

Comp LSL lobes 13017/13018
227/231 @ 0.050"
116 LSA/112 ICL (4 degrees advance)
0.614/0.617" at the valve
AFR 225cc heads

Richard

glass slipper

Overlap has zero impact on compression or how much you can run. On the compression stroke, the exhaust valve has been closed since shortly after the beginning of the intake stroke and the intake valve is closing as the piston is coming up to compress the mixture. That makes the intake valve closing (IVC) as the sole variable determinant of how much compression you can run in a given engine with a given fuel and you see it in the dynamic compression ratio (DCR) formulas. I read all of the posts in this thread and saw no reference to compression and overlap so I'm not sure how you came to the conclusion that overlap has an affect on compression. In fact, when comparing the intake and exhaust lobes on two cams, they can have the exact same duration/lift but the cam with less overlap will be able to run more compression. The reason is because the cam with more overlap has a lower lobe seperation angle which makes the IVC point happen earlier in the compression stroke. The DCR formula dictates a lower static compression ratio with earlier IVC.

The later IVC allows better cylinder filling at higher RPM due to the momentum/inertia of the mixture flowing through the intake port resulting in more HP. The two components of the momentum and inertia equations (MV and ½MV² respectively) are mass and velocity so for a given mass (volume of the cylinder*density), velocity is the component that increases momentum. As RPM increases, the velocity of the column of air/fuel mixture increases which increases the momentum/inertia allowing the "column" to continue filling the cylinder even as the piston is travelling towards TDC on the compression stroke. That's why Spinmonster says a 235cc head flowing 330 CFM is better than a 260cc head flowing 330 CFM...the 235cc head has a higher average velocity for increased momentum/inertia of the column promoting better cylinder filling at all RPMs within the cams power range and will make more HP under the curve. Pretty simple concept actually, people just get hung up on the wrong numbers as the intake port volume is a "static" number they can see while the momentum/inertia number is a "dynamic" number that is just as obvious but you can't "see" it.

We have a long way to go before we get to the ideal gas engine but I also believe it'll be a long time before electric cars completely displace gas powered cars. Electric car battery technology is progressing fast but still has a ways to go to get the range and "refueling" time acceptable. We're decades away from the infrastructure needed to support refueling "all electric" powered cars. The best alternative is a "quick change" battery pack that can be swapped out at a "service station" in less than 5 minutes but then you need the electrical infrastructure to recharge all of these batteries quickly without causing problems to the "grid". We also have a good supply of oil (in spite of reports to the contrary) which will cause a slow change to electric. We have many nuclear power plants that need to be built to support this change and none are presently permitted (that I know of).

Edit: Here's an animated PV diagram of the Otto cycle engine (spark ignited gas engine):
http://techni.tachemie.uni-leipzig.de/otto/index_e.html
You'll note the intake and exhaust valves open and close at TDC and BDC instantaneously (as you noted in your post) and spark/combustion happens almost at TDC which of course doesn't really happen in the real world but is actually useful to analyze what happens as valve events are moved from those points.

Here's some more links if you're interested in learning more and seeing what's going on to get closer to the ideal Otto cycle:
http://www.mechadyne-int.com/vva-ref...sses-si-engine
http://www.mechadyne-int.com/vva-ref...ing-strategies
http://www.mechadyne-int.com/vva-ref...oad-strategies
http://www.mechadyne-int.com/vva-ref...otion-for-EIVC
http://www.mechadyne-int.com/vva-ref...less-operation
You can continue through that website for hours reading about new things on the horizon including HCCI engines.
Here's a few more for HCCI engines...neat stuff:
http://www-erd.llnl.gov/FuelsoftheFu...es/hccirtc.pdf
https://www.llnl.gov/str/Westbrook.html