Exhaust lobes and the magic cams

[1FSTRK]

It seems that the latest talk in magic cams is exhaust lobes. I can't help but wonder just how big a controlling role they play. Take a look at these two graphs.  Both are over achievers and both make 100lbs of tq around 2800 rpm with peak hp above 6200 rpm.  Both motors are 10.5 to 1 compression and both have high end heads that flow very well. Throttle bodies are 57 & 58mm and both have proven exhaust systems that perform well on many motor combinations. Here is where the cams come in, with the motors having similar power curves and performance levels for their size you could not have more different cams.

So maybe there is no such thing as a magic cam that will suddenly transform any motor into a monster, maybe these two graphs show that a lot of testing until the proper combination of port work and cam is found will always produce the best curve.




107 with the compression set @ 10.5:1 with the new S&S 635HO cams, R&R Stage V heads, S&S 58mm T/Hog with 5.3 injectors, and a Fuel Moto XXX 2-1-2 exhaust.

[Cracked Head]

You have learned well grasshopper.I think David Carradines(RIP) old martial arts master used that statement frequently,in the old kung fu tv show.Do not take offense just a simple statement.

[bulldog]

Words from No Cents(Ray) "So you guys know me...I'm just 8-up enough to give them a try and set my curiosity to rest.
As soon as the weather breaks I'm going to ride it as it sits...then I'll swap the cams and let Jim tuner up again. I will have my end cap ready for my pipe by then so we can see what difference it makes also"

Hope you don't mind me quoting you Ray, but this will truly be the test of the 635 cams, same motor and tuner. Thanks for being the guinea pig!!!

[1FSTRK]

I think Ray's bike will be an excellent back to back comparison but at this point It will be a comparison of how the cams work with his heads. I doubt if we were to switch the cams in the two motors above that either one would reproduce the results we see here.

It seems the high average producers like the tw-37, tw-8, TR-662-2 and some others,are cams that work well in their perspective range in most motors. When we get to the really high achievers we see cams that are more picky about the ports and valves when it come to reaching their potential or so it seems to me. This is where I see a lot of threads on motors that are looking to make a HP goal start into the cam switching game.

[gordonr]

I think Rays with the 635 cam will out accelerate in a head to race with his current cam but wont make the peak numbers he has now.

[1FSTRK]

I think Rays with the 635 cam will out accelerate in a head to race with his current cam but wont make the peak numbers he has now.

So you are predicting more area under the tq curve with the 635 over the 662-2?

[Admiral Akbar]

So maybe there is no such thing as a magic cam that will suddenly transform any motor into a monster, maybe these two graphs show that a lot of testing until the proper combination of port work and cam is found will always produce the best curve.

You forgot intake and exhaust systems  It's not just cams cams and ports.. 

I think the first thing one should note is that both of these Dynos happen to be on the generous side.. How much.. Don't know.. I do know that Roland mentioned to me that one of his builds made 125 HP on his dyno and one to others it made 112 and 122.. He decided his number was more accurate due to his population count of 3.. Now one thing that will occur is that people with happy dynos will make more than just good numbers when they get the right combo.. They are probably also doing extra tricks to bring out more HP.. Like cooling the heads before the last run and not sitting on the bike.. 

OK.. So if Dyno to dyno calibration is off.. What can be said?? Well.. If we assume these numbers are 10% above the normal population, IMO, they are still very very good. So what makes them special?  Not sure if you are trying to say that one has low exhaust duration while the other is high so the heads make more difference than the exhaust pipe and duration?   One thing to note is that the pipes are different. One uses a  1 3/4 head pipe and the other is stepped.. I think that you'll find that WT cams operate better with a higher exhaust velocity (and pressure) than the longer cams like the SnS. The same goes for the intake.. The WT heads use a smaller port and valve to increase velocity and keep cylinder fill up even with a longer duration cam. The RnR runs at a larger intake port that is not as efficient as the WT heads.. The stepped exhaust works well with the longer cam as flow cannot reverse as easily so scavenging is good and it's larger size keeps pumping losses exhaust pressure low.. Less intake duration helps to up the velocity on the SnS cam some but still provides sufficient fill to make HP up top.

Roland's build is more along the lines of a high performance street bike like a Ducati.. The FM build is a little more traditional for HD..
Both are excellent builds for producing high peak numbers and I sure a lot of time went into both before the build in the form of experience with other builds and during build with different pipes being tested. They are 2 different philosophies in making numbers.. Both are valid IMO..

Max
 

[gordonr]

Its my first thought. I might do a little work to figure it out sure when I have some time.

[1FSTRK]

Its my first thought. I might do a little work to figure it out sure when I have some time.

I will not hold you to anything. I know you are busy with your own builds, just wondering if that was the way you were headed.
I am always looking for insight on how others will look at the same information.
As I said in the OP at this level the actual test seems to be the way to the answer.

[Admiral Akbar]

Its my first thought. I might do a little work to figure it out sure when I have some time.

If you plan on using dynomation, would you have any problems sharing the files?

Max

[gordonr]

Its my first thought. I might do a little work to figure it out sure when I have some time.

If you plan on using dynomation, would you have any problems sharing the files?

Max

Sure

[strokerjlk]

I think Rays with the 635 cam will out accelerate in a head to race with his current cam but wont make the peak numbers he has now.

I would be betting with you .

[1FSTRK]

gordonr

Do you use the wave simulation?
I have not had much luck with Dynomation coming close on a cam change like this when so much actual flow, and cam lobe profile information is missing do you do something to get around this?
When modeling Harleys what do you specify for manifold type?

[gordonr]

I do use the wave forms. It is tough to read on the bagger exhaust systems. When you input lift at starting 0" lift then at .050" the program tries to figure out the lobe ramp or you can wing it on the scale up to 10 being the most aggressive. Then there's the small problem of .050" and .053". Depending on the cam, Ive seen around 2 to 2.5 degrees difference. So when inputing cam specs I will a make correction. The intake is tough as well. But there is ways to work around it.

[1FSTRK]

There will not be that problem with Ray's bagger exhaust pipe 

[No Cents]

I posted a pic of the 635HO cams in my 124 thread. They definitely have a typical looking intake lobe...but the exhaust lobe is a lot different in appearance, and has a very interesting shaped lobe.

[panic]

Depending on the cam, Ive seen around 2 to 2.5 degrees difference.

Boy, I hope not.

[Nowhereman]

"Potty mouth"k this "Potty mouth"... peak this peak that.
All that matters in a race is that one guy have more torque at shift points than the next guy.
Peak numbers are for bench racers.
First one to a 100 mph for my club wins the beer.

[Admiral Akbar]

"potty mouth! " this "Potty mouth"... peak this peak that.
All that matters in a race is that one guy have more torque at shift points than the next guy.
Peak numbers are for bench racers.
First one to a 100 mph for my club wins the beer.

I think you mean horse power.. Add Assuming it's measured at the crank..

Max

[1FSTRK]

Depending on the cam, Ive seen around 2 to 2.5 degrees difference.

Boy, I hope not.

So in your experience mapping Twincam Harley lobes how many degrees difference do you see between .050 and .053 lift at the lifter?

[mike jesse]

Might try running these questions by some of the smart fellows over on Speed Talk.

[gordonr]

Depending on the cam, Ive seen around 2 to 2.5 degrees difference.

Boy, I hope not.

So in your experience mapping Twincam Harley lobes how many degrees difference do you see between .050 and .053 lift at the lifter?

Its not all not that big a deal. When checking a cam with a degree wheel measure it at .050" and .053". Using cams taken at .053 can accurately be input into programs that support .050"

[1FSTRK]

Depending on the cam, Ive seen around 2 to 2.5 degrees difference.

Boy, I hope not.

So in your experience mapping Twincam Harley lobes how many degrees difference do you see between .050 and .053 lift at the lifter?

Its not all not that big a deal. When checking a cam with a degree wheel measure it at .050" and .053". Using cams taken at .053 can accurately be input into programs that support .050"

That is how we have always done it if a lobe trace is not available. I have seen between 1.5 and 2.5 degrees at the shop that does my motors.

[IronMike113]

I think Rays with the 635 cam will out accelerate in a head to race with his current cam but wont make the peak numbers he has now.

So you are predicting more area under the tq curve with the 635 over the 662-2?

My money's are on the 662-2's I'v been Wrong Before....

[PanHeadRed]

there is no such thing as a magic cam that will suddenly transform any motor into a monster, these two graphs show that a lot of testing until the proper combination of port work and cam is found will always produce the best curve.

I took the words so and maybe out of your sentence, it makes the sentence more accurate..........