Dual pattern cams...Black Magic or Legit?

[DSGcoupe]

I have looked at that manifold several times and it would be cool. According to the data I have, it would be close on height with dual plenums, but would fit. I was actually considering something along these lines
Would fit, could use a manifold that I already have, and would be efi. I have used efi a lot and sequential injection is very nice when fine tuned. It would add to the cool factor, but would definitely lose the period correct look.

Sorry for the HUGE pic, couldn't get site to let me resize.

[Dominik]

Last time I read about those all out WOT V8s (in the 90s), they had what felt like 14 different compression ratios across the 8 cylinders, as many rocker arm ratios and even took cam twist into account, meaning front cam timing was ahead of the rear.

All that when I considered "timing" my 496 cui cam (discarded that idea because of above and put it on "zero")

I poured another whisky after.

Technically, if you have variable cam timing today for each valve and measure efficiency in each exhaust (make up a value for "efficiency" here, perhaps a combination of heat, speed, AF ratio, pressure...), then you get more out of your mill.

Buy better tires instead. Helps more.

[NROTOXIN]

Originally Posted by eschaider

If my memory serves me correctly, there is a pic of this style manifold on multiple engines somewhere here on the site. I have been unable to find it despite my best efforts. I did find a picture out on the net. This is what it looks like;

The manifold is built from components; my guess would be to allow fitment to more engines w/o the effort and expense of building limited demand, engine-specific manifolds.

The beauty of the design is the uniformity of runner design from cylinder to cylinder, which speaks directly to the intake runner length issue you were looking to mitigate. A nice spinoff of the design is that it appears low enough to fit under a Cobra hood.

If you employed a Viper-style air box model and built two box-style air plenums over the air horns for each bank, sort of like a Viper uses, it would have a high under-hood wow factor — but it would not be exactly period correct. The bling factor, cool factor, and corrected runner metrics could possibly offset some of the period-correct angst ...

Another oh-by-the-way sort of issue that needs to be considered is that it would force you to EFI.

There are several cars in the SF Bay Area running this manifold. It absolutely rocks the engine compartment.

https://www.morrisonoz.com/FordManifolds.html

[eschaider]

Thanks for the heads up nrotoxin! I can't believe those guys are right here in our own backyard!

Your link takes the viewer right to the manufacturer's site. The range of products and configurability is impressive in the extreme, especially for the SBF.

Your observation about the WOW factor when you open the hood is spot on. I have not seen anything that is more visually impressive, including the blower on my own engine. The baseball left the ballpark when that intake was designed.

Absolutely stunning visually and, more importantly, stunningly configurable!

[DSGcoupe]

Originally Posted by eschaider

I can't believe those guys are right here in our own backyard!

That is one thing I miss from being stationed at Travis AFB. There, many options for cars guys to get parts or services and generally the same day. Here, pick a direction, drive 4-6 hours just to hear them say they can order it for you.

[1795]

Just get a set of Webers with direct induction individual runner manifold and be sone with it. Can't get more period correct than that.

Jim

'

[Gaz64]

I think this needs to get back on topic.

The REASON for 4 PATTERN CAMSHAFTS IS for single central located EFI or carburetor V8.

Individual runner, webers, Autolite inline, MPFI etc is not part of this equation. Unless for some stupid reason the runners have some crazy length differences.

A statement from Comp Cams:
To make the most power from your engine, you need to optimize the air ingested and captured by avoiding valves closing too soon or too late. COMP Cams 4-pattern hydraulic roller camshafts are the first series of cams designed to accommodate a difference in runner length and avoid valves closing at the wrong times. Any conventional center-layout single throttle body or carbureted V8 intake manifold features longer outboard runners and shorter inboard runners, meaning that each valve event should occur at a different moment. COMP Cams has designed a series of cams that optimizes valve events and features a large increase in both area under the curve and stability at high rpm. They feature four different lobe patterns with one intake and exhaust design for outboard runners and another intake and exhaust design for the inboard runners. While the four central cylinders are all the same grinds, the outboard exhaust openings are two degrees earlier, with outboard intake closings coming two degrees later. NASCAR has been utilizing this technology for years. COMP Cams is now applying this same knowledge in street vehicles to balance air/fuel ratio per cylinder. These cams are CNC-ground from steel billet cores. They feature cast iron distributor gears and utilize a series of lobes with over .600 in. valve lift and stability up to 7,500 rpm, all while providing more consistent cylinder to cylinder torque. They also feature tight lobe separation for both excellent power and a throaty sound. Designed for small block Chevy, big block Chevy, and small block Ford carbureted or fuel injected applications, the design is exclusive and unique to COMP Cams.

[eschaider]

I think the reason this type of camshaft helps in a true race application is it allows the four middle cylinders to run at AFRs that more closely approximate the four corner cylinders, thereby providing a better AFR or lambda behavior on track. That may (I don't know) translate into better race mileage because those cylinders no longer run as rich as before.

One of the immutable facts, or as I like to call them, universal truths, is that a cylinder with a compromised (doesn't matter how it happened) air inlet will always produce less power than the same cylinder with an optimized air inlet, other metrics being equal — always there are no exceptions.

Now someone is going to say, "yeah, but what if I give it a squirt of nitrous?" The moment you do that (or anything similar), the whole game changes. More importantly, the racing association rules prohibit it, and the PITA rules of street car design, building, and operation significantly discourage it — so we shouldn't go there either.

If the cylinder ingests less air because the inlet is compromised compared to the other inlets that cylinder will produce less power. As luck would have it, it takes 10 lbs of air per minute (in round numbers) to make 100 FWHP. If the compromised port can only process 9 lbs of air per minute, it will only make 90 FWHP no more, no matter what, nitrous style enhancements excluded.

If stretching or reducing cam duration can move that additional air to bring that cylinder back to 10 lbs of air per minute, then that begs the question, why did you not further optimize the cam profile for the cylinders with the good ports and make even more power — this is after all a race engine reaching for optimum power. The answer is it is not possible (those universal truths things again). You might be able to clean up the AFR and improve fuel consumption but that is about it. The cylinders hampered by less effective runner architecture will continue to be wimpy powerwise.

You can not tune horsepower back into a cylinder that is being choked off for air. It is impossible without using something like nitrous to add the additional oxygen necessary to burn the fuel.

[DSGcoupe]

eschaider- This is why I agreed in an earlier post about having a common plenum with tuned length (or equal length) runners. Design the ports/runners to work the same across the board, efficiency will follow (this I can prove from flow bench and dyno testing I have done over the years). I know there is a bit more science and math that goes into it though.

Gaz64- I had read that before which started my curiosity about how they may or may not work on a more street oriented motor. I can see the application in a CUP motor that runs 7k-8k for laps and laps, but had my doubts about a street motor that lives in the 2.5k - 5k area. Seemed like it was more of a pain than an asset.

1795 - I have a blue thunder weber manifold in the shop. Love the idea, but don't like not having filters on them where I live (middle of Corn fields). I have yet to find a solution that I liked how they looked. I may use it as a base for an idea I have floating around in my noggin however.

[eschaider]

Originally Posted by DSGcoupe

eschaider- This is why I agreed in an earlier post about having a common plenum with tuned length (or equal length) runners. Design the ports/runners to work the same across the board, efficiency will follow (this I can prove from flow bench and dyno testing I have done over the years). I know there is a bit more science and math that goes into it though ...

I wasn't attempting to rag on you, DSG. I was speaking to the Comp representations in the link to the Motor Trend article. I should have been more clear, my bad. If you are not a critical reader, the write-up sounds like the engine can produce more power with the four-pattern cam. In fact, it does, but not for the reasons nor at the levels the reader might intuitively attribute to the statement.

Because the airflow to the weak cylinders is reduced, they suffer a power reduction in two dimensions;

Dimension #1 Ve

Because the air flow to the cylinder is reduced by the compromised runner metrics for those four cylinders, The cylinder has less oxygen to use in burning (oxidizing) the fuel present. Less air means less horsepower. It is a linear 1:1 relationship.

Dimension #2 AFR

Because the cylinder has less air and relatively speaking, more fuel per unit of air, it will run rich. A rich tune is a lazy tune, down on power because of the overly rich mixture. If you find a way to correct the AFR for the air present in the cylinder, then you should expect an increase in power compared to the lazier, richer mixture that was previously made available.

Even though you may find a way to "normalize" the AFR with the other cylinders (hard with carbs much easier with sequential EFI) the "weak" cylinders will still be burning a smaller intake charge than the good cylinders. Anytime you burn less fuel and air you get less power — guaranteed.

[DSGcoupe]

No worries eschaider, I didn't take it as you ragging on me. Just saying I agree with you and have data to back up what was discussed. The 4 pattern cam seems to have a place in engines that live at high rpm and the end user is worried about squeezing every ounce of power and fuel economy(relative) out that they can within the confines of rules. Not so much for what our cars are used for.

[Buddy Rawls]

I assume you are referring to camshafts with the lobes set up for specific cylinders. To make it work properly, not just to be a latest trick of the week, the complete flow paths of each cylinder would have to be flowed. This would require intake side to have intake manifold attached and the exhaust to have a full length header tube. Then you could see the cylinder to cylinder differences and what changes specific cylinders would require. Then a camshaft ground to those needs would need to be a full custom machined camshaft, all lobes and positiongin, Not just a specific intake and exh lobe and LSA. But rather this intake lobe and this exhaust lobe on very specific centerlines for cylinder 1, then so on and so on. this means that cylinder 1 might have a 110.5 LSA, and cylinder 2 might have a 110.25, etc and the lobes lightly different too.

You run a far better scenario of proper valve events by flowing all cylinders (full paths), then averaging all the intake flows and all the exhaust flows, then coming up with a conventional camshaft with an intake lobe and exh lobe, used throughout on each cylinder, set up on a specific Lobe Sep Angle (to match the openings and closings that were calculated to give the lobes that match).

If this is not what you are talking about, then explain, and I will address it from your questioning.

I think you are truncating the above thoughts to use end cylinders as same intake and exh lobes and LSA, and the center cylinders as a different set of lobes and possibly slightly different LSA. But in my first scenario of quantifying every cylinder, you an see that unless all center cylinders flow identically and end cylinders flow identical, its not near perfection.

In closing if you cannot run the motor a group of single cylinders, whats the point??? grouping center cylinders that do not flow identically and end cylinders that dont flow identically is not accomplishing anything. sure it may help. but the better solution is to average the cylinders, first get the flows as equal as possible, and go from there.

[twobjshelbys]

So I read back and the summary of these is that you gain an almost undetectable (to the typical user) increase in HP/TQ, but a number that I have seen is lost in run-to-run dyno variances anyway. If my DVM gave me voltage measurements that varied as much as a dyno it would be a useless tool.

[DSGcoupe]

Originally Posted by Buddy Rawls

I think you are truncating the above thoughts to use end cylinders as same intake and exh lobes and LSA, and the center cylinders as a different set of lobes and possibly slightly different LSA.

This is what started my curiosity. Assuming someone was using a typical single plane intake, the cams that I have seen advertised recently have one set(inside runners) of in/ex lift and duration numbers and another set (outside runners) with different in/ex lift and duration numbers. It seemed like snake oil to me for the reasons you posted above but I thought I would ask anyway. I understand that there is a lot more that goes into a camshaft grind and I tried it (spec'ing cams) with about a 40/60 success rate. But in the long run, it was easier for me to have someone do it that deals with it everyday. Unfortunately, my local guy for cams has passed on. Mr. Lykins will be filling that spot soon I hope.

In conclusion, it seems to be common consensus that this idea is just "the next best thing" and not more than a marketing ploy for ~95% of us.

[eschaider]

Originally Posted by Buddy Rawls

... You run a far better scenario of proper valve events by flowing all cylinders (full paths), then averaging all the intake flows and all the exhaust flows, then coming up with a conventional camshaft with an intake lobe and exh lobe, used throughout on each cylinder, set up on a specific Lobe Sep Angle (to match the openings and closings that were calculated to give the lobes that match)...

Assuming someone wanted to attack that windmill, the easiest way is with EFI, wideband oxygen sensors, individual cylinder fuel metering, and EGT sensors. You only have the cost of the sensors and EFI which you will be continuously reusing, and it will allow you to optimize each cylinder.

That said you still need the intake in post #20,

[Buddy Rawls]

Originally Posted by eschaider

Assuming someone wanted to attack that windmill, the easiest way is with EFI, wideband oxygen sensors, individual cylinder fuel metering, and EGT sensors.

that has zero to do with the airflow thru the motor. runner differences and flow parameters are a flow issue, not a fuel and air matching to compensation. you are talking about tailoring cylinder to cylinder A/F needs as a swap for flow differences. thats not a swap, thats a compensation to the flow differences.

[eschaider]

Actually, it has everything to do with eliminating the flow imbalances, Buddy.

If you read the first page of this thread, the OP is curious about using different cam profiles by cylinder to correct for the different (mass) airflow characteristics of the cylinders, which were fed with short vs long runners.

The OP was curious if it was possible for the cylinders with the lower (mass) air flows to improve their processed (mass) airflow by compensating with different cam profiles for those affected cylinders, leaving the intake runner differences untouched.

If you accept the premise that individual (mass) air flows for cylinders of the same volume, vary in relation to intake runner size and volume, then obviously, making all intake runners the same shape and length eliminates the variable and the differentiation.

You should re-read the OP's original question. It will help you better understand the responses in the thread.

[Buddy Rawls]

Originally Posted by eschaider

Actually, it has everything to do with eliminating the flow imbalances, Buddy.

optimizing A/F has nothing to do flow parameter imbalances. optimizing A/F cylinder to cylinder is a compensation for those flow imbalances. You cannot improve flow of a motor by A/F compensation. it doesnt work that way. You are simply tuning the motor cylinder to cylinder, compensating for those for those differences cylinder to cylinder.

Ok, I see your issue. You wrote "If you accept the premise that individual (mass) air flows for cylinders of the same volume, vary in relation to intake runner size and volume, then obviously, making all intake runners the same shape and length eliminates the variable and the differentiation."

yes, that fixes the situation of needing different lobes by cylinder. But that is not the question. The question was, if differing lobes for the cylinders for a single plane intake manifold design a snake oil concept? The differing lobes on one cylinder to the next is used to compensate for flow parameter differences. When the question is about the reasoning for a multi pattern cam within its design parameter, ie the typical single plane manifold, your answer is, if it had an IR manifold it wouldn’t need such a cam. You’re basically agreeing that different flow cylinder to cylinder can benefit from a cam that address cylinder to cylinder differences.

If this was a class motor that had specific rules for intake manifolds, the answer is not use a different manifold. So is it snake oil? No it’s not. But if you go with an OTS camshaft that may not respond to the actual motors’ flow differences it’s junk.

[eschaider]

This kind of dialog is particularly unhelpful for the OP and most readers. That said, if this is what you want, let's explore a bit …

You said:

Originally Posted by Buddy Rawls

optimizing A/F has nothing to do flow parameter imbalances. optimizing A/F cylinder to cylinder is a compensation for those flow imbalances. You cannot improve flow of a motor by A/F compensation. it doesnt work that way. You are simply tuning the motor cylinder to cylinder, compensating for those for those differences cylinder to cylinder.

I don’t believe I said what you are taking issue with. That said, for the most part, what you are saying is correct.

In your post #36, in response to my post #35 you stated,

Originally Posted by Buddy Rawls

that has zero to do with the airflow thru the motor. runner differences and flow parameters are a flow issue, not a fuel and air matching to compensation. you are talking about tailoring cylinder to cylinder A/F needs as a swap for flow differences. thats not a swap, thats a compensation to the flow differences.

I was attempting to address a corrective solution for the OP, who was concerned about air charge differences between cylinders with differing intake ports and whether a creative cam design might help. The direct solution remains the correction of the (mass) air flow problem, which is the varying Intake runner size and length. The solution is achieved by using an intake that has identical inlet runners — like the one in the picture. Multi-pattern, multi-lift, and/or LSA cams do not correct for a bad intake runner design.

Once you make all the intake runners the same, you now need to equalize the fuel delivery to the cylinders. The easiest way to do that is with an EFI, which supports individual cylinder fueling control, and an EGT thermocouple at each exhaust port to measure exhaust temperatures under load. The EGT sensors are necessary because of variations in injector flow behavior (which can sometimes be significant) The EGT sensors allow for a significantly more precise calibration.

Originally Posted by Buddy Rawls

Ok, I see your issue. You wrote "If you accept the premise that individual (mass) air flows for cylinders of the same volume, vary in relation to intake runner size and volume, then obviously, making all intake runners the same shape and length eliminates the variable and the differentiation."

I have consistently found that reading words will significantly improve messaging, especially if the reader can understand the words.

Originally Posted by Buddy Rawls

yes, that fixes the situation of needing different lobes by cylinder. But that is not the question. The question was, if differing lobes for the cylinders for a single plane intake manifold design a snake oil concept? The differing lobes on one cylinder to the next is used to compensate for flow parameter differences. When the question is about the reasoning for a multi pattern cam within its design parameter, ie the typical single plane manifold, your answer is, if it had an IR manifold it wouldn’t need such a cam. You’re basically agreeing that different flow cylinder to cylinder can benefit from a cam that address cylinder to cylinder differences.

Snake oil can be relative, which is why process understanding is important here. The question was soliciting a yes or no opinion on a snake oil labeling for cams that use multiple profile cylinder by cylinder architectures/designs.

The significant issue here is that the lobe gymnastics do not fix the problem of differing power delivery from different cylinders. The OP accurately identified the phenomenon as resulting from varying cylinder-to-cylinder inlet manifold passage flow dynamics. If the problem is optimizing and normalizing cylinder power, the solution is absolutely not multi-profile cams.

So is the multi-profile cam snake oil? The answer is indeterminate without additional conditions and specifics. In particular, as you identified, if the manifold is not changeable (for class rules reasons). In that case, the multi-profile cam, might, be helpful. Most tests have shown the improvement to be at the noise level and very often inside the widow of repeatability (margin of error) for an inertia or water brake dyno. Sort of begs the question, why are we wasting money and time?

Let’s say the manifold is not mandated and is, in fact, changeable — sort of like on our cars and the OP’s car. Now, if we want to positively correct for the differing cylinder power levels that are being impacted by the differing (mass) air flows, we simply acquire the pictured manifold or a similar manifold. That intake manifold, along with a single or dual pattern cam suited to the engine and the car, will address the problem the OP was originally thinking about corrective measures for.

Back to the universal truths, two cylinders with the same charges of fuel and air, same c/r, same ignition will always produce the same power output, assuming the same fuel. Similarly, two cylinders with the same charges of fuel but differing weights of air, even with the same c/r, same ignition, etc., will always produce a different power output using the same fuel. It is inescapable!

Originally Posted by Buddy Rawls

If this was a class motor that had specific rules for intake manifolds, the answer is not use a different manifold. So is it snake oil? No it’s not. But if you go with an OTS camshaft that may not respond to the actual motors’ flow differences it’s junk.

Yes, it is snake oil! The improvement is down below the margin of error on virtually any inertia or water brake dyno. If the problem is important enough to the car owner to go chasing after it (I think it is foolishness), then the solution is identical inlet runners, EFI, individual cylinder fuel control, and EGT sensors. You will absolutely solve the cylinder-to-cylinder power level differences and spend a lot of money. You will also discover that the bang for the buck spent would have been much better had you gone to a driving school and diligently learned what the school instructor was attempting to teach about driving a road race car.

[Buddy Rawls]

“The significant issue here is that the lobe gymnastics do not fix the problem of differing power delivery from different cylinders. The OP accurately identified the phenomenon as resulting from varying cylinder-to-cylinder inlet manifold passage flow dynamics. If the problem is optimizing and normalizing cylinder power, the solution is absolutely not multi-profile cams“

The whole purpose of the original post was questioning what is special regarding the 4 pattern cams. The design basically uses differing valve events for the inner cylinders and for the end cylinders. The question was posed, Is it snake oil or legitimate? Flow differences from cylinder to cylinder when used on an open plenum intake that different port lengths (and flow and velocities) is where valve events that match the cylinders flow parameters do their work. But the valve events have to be right.

Your statement about lobe gymnastics not being able to fix flow problems is where we differ. As an engine modeler, I developed my valve event calculations in the 90’s and have been doing custom cams for 25 yrs. The doors (valve events and ramp rates) into and out of the cylinder are critically important. And the valve events and ramp rates are critically linked to the the flow parameters. Valve events can crutch short comings (restrictions, high velocities, or poor flow regions) as well as truncate the activity of over abundant huge cross-sections and low velocities. A camshaft is not a globally characterized component, although everyone tries to make it work like that. Given same cid geometry, the behavior of 270 degrees duration (for example) on large cross section inlet ports is drastically different than on a small cross section high velocity scenario. The exhaust positioning requirements vary greatly between the two as well.

Applying this to the multi patterned camshafts, in a situation of different flow parameters might look like: Cylinder A needs valve events that calculate to 270 deg seat duration on the intake on a 108 centerline. The exhaust might be 273 deg on a 113 centerline. Cylinder B with different flow might need 272 on a 107.5 intake and 273 on 112. These are a simplified look at the sort of differences that valve events tailored cylinder to cylinder might look like. Grinding such a cam would be a pita. Using an OTS 4 pattern cam, that may or may not match the needs of the motor’s flows is no diff event than any incorrect cam, except it has some good buzzwords along with it. Wrong is wrong. Correct is correct, and it can be thought of like a bell curve. Perfection with the airflow has some tolerance for sure.

Totally equal cross-sections and lengths exhibit very similar, if not equal flow parameters. And small differences can be perfected by the A/F delivery. But this does not change air flow thru the motor. This is utilizing what flow characteristics the cylinders have and optimizing A/F.

To me, it seems like you look at the A/F as the equalizer and power maker. I look at the engine flow parameters (controlled by the valve events) as the power maker, with A/F being a tuning tool to optimize thru the range.