93PONY

How to calculate VE's given duration, LSA, & ICL:
Example cam 230/236 112LSA 108ICL

IVO = ((intake duration/2)-ICL)
Ex: ((230/2)-108)= 7 BTDC (negatives indicate ATDC)
IVC = ((-IVO) + intake duration - 180)
Ex: ((-7) + 230 - 180) = 43 ABDC
ECL = ((2 * LSA) - ICL)
Ex: ((2 * 112) - 108) = 116
EVC = ((exhaust duration / 2)- ECL)
Ex: ((236 / 2) - 116) = 2 ATDC (negative indicates BTDC)
EVO = ((-EVC) + exhaust duration - 180)
Ex: ((-2) +236 - 180) = 54 BBDC
Overlap = ((intake duration + exhaust duration)/2) - (2 * LSA)
Ex: ((230+236)/2) - (2 * 112) = 9

J-Rod

93Pony. Sorry, I should have been a bit more specific. In my original post I covered the math required to calculate the valve events themselves. I guess what i was getting at is the forumlas to determine what is optimal, or more optimal than something else.

Here is the origianl quote on calculating VE.

Ok, now this is my understanding of things. There are four timing parameters that define how your engine will operate. These are intake valve opening (IVO), intake valve closing (IVC), exhaust valve opening (EVO) and exhaust valve closing (EVC). It is relatively easy to derive these parameters from the specs supplied by camshaft vendors (lobe center angle (LCA), intake centerline (IC), intake duration (ID), and exhaust duration (ED)) assuming all these parameters are specified.
IVO = ID/2 – IC
IVC = ID – IVO – 180
EVO = ED – EVC – 180
EVC = ED/2 – 2*LCA – IC


But, thanks for adding the calculation for Exhaust Centerline and overlap. I am putting all this into spreadsheet for everyone to use.

J-Rod

Ok, I used yours, as the formulas I had seemed to be missing a few parts of the calculation. Here is the spreadsheet with your formulas. I left your example in...

Quick and Dirty VE calculator Spreadsheet

93PONY

No real formula for this.... Really depends on the combo & what the owner wants out of it as to what VE's are best. Just gotta know what works with what & why.... Every motor is different. What works well in one application may be totally wrong in another. Too many variables to post all the little things like this that go into designing the correct profile. This is where an experienced Pro is needed.

Reboot

iTrader: (5)

Based on the spreedsheet my C1 Hammer cam is dead on the money as far as the valve event with a 112LSA and 108 ICL and so is the TR224 114 LSA 110ICL.

BYBYC5, it looks like you got you IVC and EVO numbers transposed. If that's the case your VE's fall in line as well.

J-Rod

What do you use as a determing factor in this, and is there a hard and fast relation ship you use in this determination
I will assume from your previous posts more overlap=more power. Conversely more overlap= more fugitive emissions (do I want to pass smog or not). Any ranges your tend to go with? Any determining factors you use in coming up with the ammount of overlap you choose. I notice you tend to go with lots of overlap though.
Same question as before. Any determing factors, or rules of thumb you use? Are these things you choose, or are they a byproduct of the previous "points" you have selected?
that makes sense. Just more curious on the selection criteria used to come up with the inital portions of this which govern the values used in the VE calculations.

I gathered some of this from your previous comments, and I think these are all factors in determining cam selection. Flow is probably the most important and determining factor. I/E percentages are obviiosly something to look at. The other things, N2O, racewieght, gearing, etc, etc. are all important considerations.

Nitrous is probably one of the bigger questions. Do you tend to up the exhaust side and run a wider LSA when selecting nitrous cams. The conventional school of thought is to go htis route on nitrous cams. I wondered if you concur with this.

I would agree with this statement. Just not too far past...

I guess thats what I was getting at. What do you feel those are?

Agreed to a certain extent but as you have already stated. Long runner EFI applications like Mustang motors or LS1s are no differnet in that the same things work in both.

I agree that here are a lot of varialbes to take into consideration. I am simply looking for a way to narrow some of them down.

93PONY

I'll try to answer some of your questions here....sorry if I don't get all of them....too much info in the wrong hands... I hope you understand. Can't give out all my secrets!

When you think about it the main difference between any 2 engines is intake design. I mean, head flow is head flow. The valves are all in generally the same place & at nearly the same angle. Same combustion chamber design for the most part. Longtube headers are all basically the same. Bore & stroke can vary, but not to any drastic extent as to change the fundamentals of a motor. So a lot of the same technics in making power can be used.

I favor reverse-splits on all EFI motors. Hell, from the factory the 4.6 mustangs come with reverse-splits (192/184 114LSA). HP per cube on this motor is not bad at all.

On juiced motors I do fatten up the exhaust lobe a bit. Not to the extent others do as there's really no need unless a larger shot it used (over 150wet). With the added cylinder pressure in the combustion process there is higher velocity during the exhaust stroke....& therefore more flow. I don't automatically add 8 degrees of exhaust duration if that's what you're asking. It depends on the shot used & rest of the combo as to how much intake or exhaust bias to use.
For instance, with a stock LS1 spraying a 200 shot what I generally do is have the ramprates of the lobes the same. But certain applications I may use a softer ramp on the intake....or a reverse-split at .050, but a standard split at .200. There's are so many different combinations of lobes that will perform differently in any given combo. As for LSA with juice...sure I may increase it a bit, but I'd probably use larger lobes too. I generally don't decrease the overlap much with an N2O cam....but again, depends on the combo. A motor that is to pass smog can only have so much overlap anyway...so why decrease it if their using a shot. No need....there's hardly any overlap in the profile anyway. Raw N2O isn't gonna shot out the tailpipes on a setup like this. Now, larger profiles that want max power N/A & use the occassional shot I may or may not decrease the overlap. Depends on the customer needs & the combo....

I really don't mean to talk in circles here guys. But just about every factor in designing a bumpstick is combo/customer specific.

For my cams I shoot for -4 to -3 degrees of overlap on the smogable grinds. (once I get emissions figures on a few of these I may put in more, but for now this is safe.) On non-smogables....all the way up to 10 degrees on the stock longblock will fit if placed correclty. More on strokers & pistons with valve reliefs.

J-Rod

I understand, and I don't necessarily want all your secrets, but some working parts of your theory would be nice.

I would have to disagree with you on that. I think there are greater differences than simply intake design. I think things like number of valves, valve angle and several other factors make for quite a few differences.

Yes and no. I mean, I post a spreadsheet with flow numbers of most of the major head porters. But, I also know that a set of heads from vendor X may flow less than vendor Y, but still make more power on the car. A flow bench measures air movement in a very rudimentary way - steady-state flow at a constant depression (vacuum). Obviously the conditions that exist inside a running engine are quite different. The flow bench can't simulate the effects of the pistons going up and down, the reversion pulses as the valves open and close, the sonic waves that resonate inside the runners, the inertia of the fuel droplets, and all of the other phenomena that influence engine performance in the real world. When you flow test a cylinder head, you are simply measuring how far you can move the liquid in a manometer.

The bigger you make a port, the more it flows. That's hardly shocking news. Bolt a sewer pipe onto a flow bench and it will generate terrific flow numbers. So should we use ports as big as sewer pipes on our race cars? The flow bench says we should - the time slip says something completely different.

If airflow were everything, we would all use the longest duration camshafts we could find - after all, more duration means more flow. In fact we know that there is a finite limit to how long the valves can be open before performance suffers. That is because the valve events have to be in harmony with the rest of the engine.

The same principle applies to cylinder heads. Simple airflow capacity should never be the first consideration in evaluating cylinder heads. Characteristics that are far more important include air speed, port cross section, port volume and shape, and the relationship between the size of the throat and the valve seat. If these attributes are wrong, you can work forever on the flow bench and not overcome the fundamental flaws.

I will have to respectfully disagree here also. Valve angle has a huge effect on cylinder heads by affecting the "angle of attack" on your entry into a port. Let me cite a simple example from the SBC world. Regular SBC heads have a 23 degree valve angle. Whats one of the things you see racers do on 23 degree heads. They angle miss the snot out of them to do two things. Roll the port over, and decrease combustion chamber volume. Look at a Buick head. The valve angle there is about 15 degrees. Chevy liked this design and in the 80's took the buick desing and started building "Buick" heads for the SBC. These heads come with a 15 degree angle. When you are done with them they have about a 10-11 degree valve angle. All this has a big effect on flow and velocity, which has a huge effect on power.

Again I don't necessarily agree. You have wedge, hemi, pent roof, and a whole host of others. The shape of the combustion chamber also has a significant impact on performance. A conventional chamber with deep reliefs around the valve seats and a relatively flat valve seat angle can produce terrific flow at .200 to .300-inch valve lift. Today a state-of-the-art chamber typically has 55-degree valve seats and steep walls that guide the air/fuel mixture into the cylinder to enhance high-lift flow. This doesn't mean that every racer needs state-of-the-art Pro Stock cylinder heads - along with the high maintenance they require. The heads have to match the application. Conventional combustion chambers and 45-degree valve seats are just fine for a dependable, low-maintenance racing engine that will run a full season between overhauls.

One of the things Craig Gallant @ GTP is fantastic at in his cylinder head program is maximizing cylinder head flow with the carefult slection of valves. On a recent set of heads we use ina class where unported heads are required, he picked us up 40 CFM with just the careful selection of valves, and careful selection of valves angles. No porting whatsoever...

Back to my point about combstion chambers. Lets look at the Hemi. The classic Hemi combustion chamber is capable of producing impressive flow figures, but it's not going to make impressive power. Engine technology in all forms of motorsports is converging around smaller, high-efficiency combustion chamber designs. You can see the result in lower brake specific fuel consumption (BSFC) numbers, which indicate improved engine efficiency. Twenty years ago, a racing engine with a .48 BSFC was considered very good; today's competition engines produce BSFC numbers in the neighborhood of .35. This means that a given quantity of fuel is being atomized and burned more effectively to produce more power. A cylinder head's combustion efficiency can't be measured on a flow bench, yet it has a huge impact on performance.

Just like camshafts, header design is an art. Look at the design of just the collectors from someone like Burns. Heck look at their header theory page.

http://www.burnsstainless.com/TechAr...ry/theory.html


They want just as much information about the motor as any custom cam grinder does to help select the best way to get those burned gasses out of a motor. The concept that maximum power is obtained by zero pressure in the exhaust is only partially true. There should be absolutely no back-pressure from the collector rearward, but the diameter of the system beginning with the exhaust valve is a compromise. The highest efficiency for the system requires a minimum speed for good exhaust gas velocity to insure that gas does not "back up" into the chamber during overlap at low engine speeds, and that the "suction" (negative pressure pulse) effect of a resonant (tuned length) and/or collector (overlapping exhaust pulses) system is optimized.

To predict what primary size will be best for a specific motor, you must know where you want the engine to develop peak torque. If the existing torque peak is at bit lower RPM than you prefer (typical in under-cammed or stock motors), it can be "bumped" a bit by increasing the primary diameter. If the torque peak is too high (motor is "peaky", with no range and poor recovery from gear changes), the peak can be adjusted down by using a smaller pipe. A change of 1/8" in the primary diameter will raise or lower the peak torque RPM by 500 or so.

This factor slightly overlaps the effect of primary pipe length, but the pipe length generally will not change the peak torque or the RPM at which it occurs. A length change has the effect of improving the torque on only 1 side of the peak by "borrowing" it from the other side. A shorter pipe improves the torque after the peak (reduces it at lower RPM), preventing the curve from flattening out so quickly as speed increases. A longer pipe extends the torque curve backwards to improve the engine's flexibility, at the expense of after-peak torque. Less stall speed is required, and the motor will pull taller gears; this re-tunes a 4-speed motor for better operation with Torqueflite, etc.

For best effect, the gas speed in the primary tube at the peak torque RPM should be about 240 feet per second. The formula to calculate pipe size is:

Area of Primary Pipe = RPM × Cylinder Size ÷ 88,200

This determines the pipe's cross-sectional area, from which we can calculate the ID. Typical exhaust pipes are 18ga. (wall thickness of .049"), so the OD will be .098" larger. From this we can construct a formula for an 8 cylinder motor, and factor in the 18ga. wall thickness:

Area of Primary Pipe = RPM × Motor Size ÷ 705,600
Pipe ID^2 = RPM × Motor Size ÷ 705,600 ÷ .7854
Pipe ID^2 = RPM × Motor Size ÷ 554,177
ID = (RPM × Motor Size ÷ 554,177)^.5
OD = (RPM × Motor Size ÷ 554,177)^.5 + .098"

Length (in inches) = (CID x 1900) ÷ (rpm x pri.OD^2)


True to some extent but bore and stroke have an effect on shrouding of the combustion chamber. Effective rpm range of a motor, etc... Lets look at two 35x cu inch SBC's One is the conventional 4.00 bore x 3.48. The other is a 4.155x3.25. I have both in my shop. One is much differnet in performance and application than the other.

Is this on ALL EFI motors or would it be fairer to classify it as EFI motors with "long" intake runners. What would you do with a shorty ram, or something with a modified intake (a Victor Jr with injector bungs). Lets say someone threw a sheetmetal manifold on an LS1 would you favor a reverse split on that?

Ok, so its fair to say you go with conventional thinking here, you may just not put as much lobe on the cam as many folks do. I was curious since your theories tend to differ twith folks to some extent on regualr N/A designs if your application for power adders or nitrous applications differed.

Agreed, but what is the mentality behind these decisions?

I agree with tuning for a combo, just trying to determine what you are doing and why

Ok, how about this. Can you post some of the grind you have done that are "public" so that we can see what you are doing? Possibly a bit of commentary on what they are doing, and why you selected them?

Here is a little chart I dug up. Does it fit in with your theories?

93PONY

Yes, all those things add up in a motor. & they do affect cam design. But generally speaking all of these motors respond the same way to longtube headers....all respond to opening up the intake the same way...opening up the exhaust. Etc, etc. All motors I've slapped reverse-splits in have generally responded the same. Idle is much more stable, AVG power across the RPM band is increased....this compared to standard splits of the same size.
I look at the camshaft as the end of the intake runner & beginning of the exhaust runner.

I really don't know what you're getting at hear, so I'll go ahead & post a cam that will be tested against a known proven LS1 cam.
There'll be dyno, track, & emissions testing on this cam....along with any drivability issues....& any other issues will be noted & compared.

Hammer cam: 222/222 112LSA 108ICL .566/.566
VS
224/222 113LSA 113ICL .581/.566

The exhaust lobe on my cam is the same as the Hammer. the only difference is a larger, more agressive intake lobe & a slightly wider LSA for passing emissions testing....oh & different VE's.

These are both LS1 Comp XE lobes. No tricks on this one.
Specs on the 2 lobes:
222:
.006 - 275
.050 - 222
.200 - 140

224:
.006 - 273
.050 - 224
.200 - 145

Plot the VE's for all these lift points on both cams & you will see exactly what I did. By the theories I've posted in this thread & others you'll should be able to figure out why I moved the VE's the way I did & why I went with a more agressive intake lobe.

J-Rod

Ok, I think I understadn what you are getting at with that, it just you have been very specific about cam design, and you were making a bunch of generalization about the rest of an engine which were not completely accurate. I was just trying to illustrate that many of the thing in an egine are just as important as cam design. Everything is a system, getting components to work together is the key.

Ok, I expanded the quick and dirty VE calculator a bit to do both cams at all three lift points, and compare the deltas.

Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 275 222 140
Exhaust Duration - ED 275 222 140
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 29.5 3 -38 BTDC (- indicates ATDC)
Intake Valve closes - IVC 65.5 39 -2 ABDC
Exhaust Valve Opens - EVO 73.5 47 6 BBDC
Exhaust Valve Closes - EVC 21.5 -5 -46 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 116 116 116
Overlap 51 -2 -84 degrees

0.006 0.050 0.200

Intake Duration - ID 273 224 145
Exhaust Duration - ED 222 222 222
Lobe Center Angle - LCA (also known as LSA) 113 113 113
Intake Centerline - ICL 113 113 113


Intake Valve opens - IVO 23.5 -1 -40.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 69.5 45 5.5 ABDC
Exhaust Valve Opens - EVO 44 44 44 BBDC
Exhaust Valve Closes - EVC -2 -2 -2 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 113 113 113
Overlap 21.5 -3 -42.5 degrees

0.006 0.050 0.200

IVO delta 6 4 2.5
IVC delta -4 -6 -7.5
EVO delta 29.5 3 -38
EVC delta 23.5 -3 -44
ECL delta 3 3 3
Overlap 29.5 1 -41.5


I'll crunch on it a bit and post up later. You can tell me if I totally have it wrong...

93PONY

You have 222/222/222 for all lift points on the exhaust of my cam. It should be 275/222/140

J-Rod

Ooops

Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 275 222 140
Exhaust Duration - ED 275 222 140
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 29.5 3 -38 BTDC (- indicates ATDC)
Intake Valve closes - IVC 65.5 39 -2 ABDC
Exhaust Valve Opens - EVO 73.5 47 6 BBDC
Exhaust Valve Closes - EVC 21.5 -5 -46 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 116 116 116
Overlap 51 -2 -84 degrees

0.006 0.050 0.200

Intake Duration - ID 273 224 145
Exhaust Duration - ED 275 222 140
Lobe Center Angle - LCA (also known as LSA) 113 113 113
Intake Centerline - ICL 113 113 113


Intake Valve opens - IVO 23.5 -1 -40.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 69.5 45 5.5 ABDC
Exhaust Valve Opens - EVO 70.5 44 3 BBDC
Exhaust Valve Closes - EVC 24.5 -2 -43 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 113 113 113
Overlap 48 -3 -83.5 degrees

0.006 0.050 0.200

IVO delta 6 4 2.5
IVC delta -4 -6 -7.5
EVO delta 3 3 3
EVC delta -3 -3 -3
ECL delta 3 3 3
Overlap 3 1 -0.5


Is that better?

J-Rod

Ok, I am reviving this thread. I haven't had much time lately to devote to this, but here is some stuff I threw together out of this thread.

Ok, so 93Pony. You:

Select EVO based on IVC, then overlap, then EVC and IVO...

So, looking at your cams:
IVC/ EVO
45/ 44
47/ 43

49/ 48
50/ 49

The other cams they were compared to:
IVC EVO
39/ 47
41/ 52
44/ 56


There are definitely some trends there, I was just wondering if you wanted to comment on the "why"...

J-Rod

Just wondering out loud here... Looking at where you like to have your Valve events, if you were to design a standard split (I know, you don't like them) using the LGM G5X2 lobes a s a references. I know, the first thing you would do would be to swap them around. Anyhow, that aside I tried to mimc your valve events for IVC and EVO, here is what I came up with.

Intake Duration - ID 281 232 153 3726 lobe
Exhaust Duration - ED 289 240 161 3730 lobe
Lobe Center Angle - LCA (also known as LSA) 108 108 108
Intake Centerline - ICL 112 112 112


Intake Valve opens - IVO 28.5 4 -35.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 72.5 48 8.5 ABDC
Exhaust Valve Opens - EVO 68.5 44 4.5 BBDC
Exhaust Valve Closes - EVC 40.5 16 -23.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 104 104 104
Overlap 69 20 -59 degrees

0.006 0.050 0.200

IVO delta 5 5 5
IVC delta -1 -1 -1
EVO delta -1 -1 -1
EVC delta -7 -7 -7
ECL delta 3 3 3
Overlap -2 -2 -2


Anywhere close?

93PONY

Why? This is the key...& that is why I will not post that info.

As for your standard split cam using modified VE's. Well....there is now another problem with your VE's. The ovlerap VE's are no where near ideal. So, basically a standard split is a comprimise between IVO/EVC VE's & the IVC/EVO VE's.
Another thing one should note.... ICL plays a factor in intake & exhaust bias. Retard the cam & it becomes less exhaust bias relative to TDC, Advance the cam & it becomes less intake bias relative to TDC.

So, you've made that cam less exhaust bias, but at the sacrafice of the overlap phase.

rmbuilder

93pony,
Is there any real world data that can be offered that will not reveal any "speed secrets" in your cam profiles? Are they for sale? If so where can we purchase one?
Thanks in advance,
Bob

93PONY

The real world data on my cams is slow coming. Only a few guys with LS1's have ordered. Just a matter of time I guess. Customer feedback will tell the tail.
But the concepts have been proven time & time again. On both LS1's & Ford's....& not only by me.
I sell LS1 customs for $450 shipped.

J-Rod

Well, I had to take a swag at it. Again, I know you aren't fond of reverse splits. I alos know you prefer the lobes to do the work, and not to use advance ground into the cam. I have noticed for instance, on one of your cams, mentioned before in this thread:
Valve events comparison:

Looking at your valve events on that cam.

IVC: 50 ABDC vs IVC: 41 ABDC = 9 degrees later (ABDC meaning After Bottom Dead Ceter)
EVO: 49 BBDC vs EVO: 52 BBDC = 3 degrees later (BBDC means Before Bottom Dead Center)

You also favor a lot of overlap, and in many cases your cams have a lot more than many other cams. With many of the cams on the market today tighter LSAs reduce drivability, raise emissions, and play havoc with untuned computers. One of the things you alluded to was that you feel it is not so much the cams themselves as where the VE's are placed, and that you could use a bigger cam if the valve events were a bit more ideal. (Correct me if any of this is wrong).

One things in racing engines that has been learned that is low-lift flow is relatively unimportant. In a racing engine: From the point when the valve first moves off its seat until it reaches mid-lift, the piston is either going the wrong way (that is, it is rising in the cylinder) or it's parked near TDC. The piston doesn't begin to move away from the combustion chamber with enough velocity to lower the pressure in the cylinder until the valve is nearly halfway open. Consequently it is high-lift flow that really matters in a drag racing engine. Now, thats racing... We're talking about street motors. So, your theories may or may not be based on that.

I think low to mid lift flow in the head is important to assist in cylinder filling, and blowdown. Also that port velocity is important. I agree to a certain extent that huge ports with good flow are not nearly as important as small ports with good flow. But I don't necessarily agree with you about the idea of stock heads being better than ported ones. I will be interested to see wha thte AFR heads do with a intake port as small as stock with 40CFM more flow than a ported head with 20cc more volume.

I guess one of the things I am wondering is if you are so concerned with EVO and IVC specifically, or where it put the valve later on in the intake and exhaust cycle.

Ok, like I said before, I know you aren't a fan of standard splits. And I know you don't like a ton of advance ground into a cam. So, I'll change things up a bit. Lets do a G5X2 clone but in a reverse split. We'll keep the intake the same and simply put on a smaller exhaust.

Ok, intake lobe first.

# 3726 lobe 232@.050 / 153@.200 / 281 Advertised. .595 lift

Now, for the exhaust side. Looking at your format, I am torn between 3 lobes

# 3724 lobe 228@.050 / 149@.200 / 277 Advertised .588 lift
# 3718 lobe 230@.050 / 147@.200 / 283 Advertised .573 lift
# 3725 lobe 230@.050 / 151@.200 / 279 Advertised .592 lift




Ok, so lets look at all three. Now let me preference this first. Theis is a clone or a SWAG at the G5X2 specs. THESE ARE NOT Lou's specs... I don't have Lou's specs in my back pocket. What I am assuming her eis if you call comp and you order the lobes that are similar to the G5X2 lobes, and you order it on a 112, comp will grinf it with 4 degrees in it unless you ask for something else specifically.

So, with that in mind, lets look at what I come up with....

Quick and Dirty Cam Calculator Spreadsheet
0.006 0.050 0.200
Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 281 232 153 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 34.5 10 -29.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 70.5 46 6.5 ABDC
Exhaust Valve Opens - EVO 76.5 52 12.5 BBDC
Exhaust Valve Closes - EVC 24.5 0 -39.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 116 116 116
Overlap 59 10 -69 degrees

0.006 0.050 0.200

Intake Duration - ID 281 232 153 3726 lobe
Exhaust Duration - ED 277 228 147 3724 lobe
Lobe Center Angle - LCA (also known as LSA) 108 108 108
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 32.5 8 -31.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 68.5 44 4.5 ABDC
Exhaust Valve Opens - EVO 66.5 42 1.5 BBDC
Exhaust Valve Closes - EVC 30.5 6 -34.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 108 108 108
Overlap 63 14 -66 degrees

0.006 0.050 0.200

IVO delta 2 2 2
IVC delta 2 2 2
EVO delta 10 10 11
EVC delta -6 -6 -5
ECL delta 8 8 8
Overlap -4 -4 -3

Cam # 2

Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 281 232 153 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 34.5 10 -29.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 70.5 46 6.5 ABDC
Exhaust Valve Opens - EVO 76.5 52 12.5 BBDC
Exhaust Valve Closes - EVC 24.5 0 -39.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 116 116 116
Overlap 59 10 -69 degrees

0.006 0.050 0.200

Intake Duration - ID 281 232 153 3726 lobe
Exhaust Duration - ED 279 230 151 3725 lobe
Lobe Center Angle - LCA (also known as LSA) 108 108 108
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 32.5 8 -31.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 68.5 44 4.5 ABDC
Exhaust Valve Opens - EVO 67.5 43 3.5 BBDC
Exhaust Valve Closes - EVC 31.5 7 -32.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 108 108 108
Overlap 64 15 -64 degrees

0.006 0.050 0.200

IVO delta 2 2 2
IVC delta 2 2 2
EVO delta 9 9 9
EVC delta -7 -7 -7
ECL delta 8 8 8
Overlap -5 -5 -5


Cam # 3

Intake Duration - ID 285 236 157 3728 lobe
Exhaust Duration - ED 281 232 153 3726 lobe
Lobe Center Angle - LCA (also known as LSA) 112 112 112
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 34.5 10 -29.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 70.5 46 6.5 ABDC
Exhaust Valve Opens - EVO 76.5 52 12.5 BBDC
Exhaust Valve Closes - EVC 24.5 0 -39.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 116 116 116
Overlap 59 10 -69 degrees

0.006 0.050 0.200

Intake Duration - ID 281 232 153 3726 lobe
Exhaust Duration - ED 283 230 147 3718 lobe
Lobe Center Angle - LCA (also known as LSA) 108 108 108
Intake Centerline - ICL 108 108 108


Intake Valve opens - IVO 32.5 8 -31.5 BTDC (- indicates ATDC)
Intake Valve closes - IVC 68.5 44 4.5 ABDC
Exhaust Valve Opens - EVO 69.5 43 1.5 BBDC
Exhaust Valve Closes - EVC 33.5 7 -34.5 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 108 108 108
Overlap 66 15 -66 degrees

0.006 0.050 0.200

IVO delta 2 2 2
IVC delta 2 2 2
EVO delta 7 9 11
EVC delta -9 -7 -5
ECL delta 8 8 8
Overlap -7 -5 -3


Ok, this moved the IVC/EVO from 46/52 to 44/43 you gained several degrees more overlap @ .050, etc.... Is this any better?

ChrisB

This formula assumes that the lobes are symmetrical though? I though symmetrical lobes went "out of style" a long time ago - it would seem to make sense that the rates at which you can open and close the valves are *very* different (working with vs. against valvespring) - and so the corrolary would be if we are talking about symmetrical lobes aren't we leaving performance at the table?




Not trying to take this too far out of context, so correct me if I am, but this seems like a *far* to general statement.

Take a stock crossfire SBC, a stock LT1, a LT1 with 215RR AFR heads but a 3" exhaust, a supercharged through the cats LS1 - do you really think that they are all going to work best neccecarily with a reverse split camshaft?


What I would really like to see is what we are using for metric's here in determining what valve events one is looking for - e.g. take the cross sectional area of an intake port, determine a certain depression due to the rotating assembly configuration, etc.

93PONY

J-Rod,
Your posts are giving me headaches again. But you're on the right track with those lobes you chose. Just have to find the right ones for the right applications.

Funny thing about that cam you quoted from Norcal-LS1. The guy put in a MUCH larger cam (231/237 112LSA) & an M6 over the A4 & ran much slower at the track. He's told me recently he's buying his old cam back.

ChrisB,
The VE's are based on Comps specs of the lobes. It does not matter if they are asymmetrical or not.

I do Favor reverse-splits on EFI motor. But that does not mean I use them on every application...nor does it mean they'll work best on every EFI motor. Just that I favor them. & yes, it is a VERY general statement.
Every application is different.