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Aftermarket Twin Cam CVO 110 Heads?

Started by Ohio HD, December 05, 2021, 02:15:02 PM

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Ohio HD

Ok, so what is the cfm rating? 198 @ 10" is about 332 @ 28". That seems more reasonable if that value in the calculation above is @ 10".

Barrett

That's a major factor that was left out. It was a question that I was asking because I don't know.
I hope it was 28. I might need a bigger bottle ;)
https://itstillruns.com/calculate-engine-cfm-intake-6393767.html

Ohio HD

After I thought about it, I think the article was presuming we knew it was @ 10". I think in some worlds that's the defacto rating. However I know just from what I've been told by those smarter than me, that a head porter may use several ratings through out the tuning of the ports process, but lists the finished product as @ 10" or it seems in our HD world @ 28".

I would think your in the neighborhood to make enough air passage for the motor.

Did you say bottle? As in NOS? 

Barrett

It's a 40 dryshot that I had collecting dust. I don't use it much, but it does give it a good kick.
It lets me know how much my tires suck.

kd

When I got my heads back from Dan Baisley they were tested and reported  10".  At that time I posted looking for the formula to convert it to 28" so I would have a comparison to what everyone seemed to use.  Max explained it. 

I was looking for torque numbers for a street engine frrom the head work.  I am thinking (but could be wrong) the 10" was used because of the cam specs and to test the lower VE to ensure the torque came in early.  The flow numbers were given to me at each .100" lift level up to .700"  . I will see if I can find the post with the explanation.
KD

Don D

December 08, 2021, 07:34:28 AM #30 Last Edit: December 08, 2021, 10:36:20 AM by HD Street Performance
You will have a hard time tying flow numbers to horsepower. Part of the reason is the bigger the barn door gets the airflow cfm goes up but the velocity goes down despite constant test pressure (very simplistic analogy with a lot of the nuances left out). Cross sectional area needs to be such that velocity is optimized to match the demand then you have satisfied the builds requirements. Displacement, VE, maximum rpm are a few drivers. A high flow slow port ends up with a pig of a build, when extreme, and is hard to tune. Then guys start searching for the "best" cam  :wink:

Pressure conversion is easy if you have 10" and want 28", √(28 ÷ 10)= 1.673. You will be comparing junk data when trying to see what a head flows from one vendor to the next in most cases for similar reasons dynos are not that easily compared. The fixturing matters as well as the test pressure and I am assuming the benches are accurately calibrated. Also standard test vacuum for carburetor CFM is 1-1/2 inches of mercury. This is 20" H2O. Another wrinkle that needs to be ironed out. Plus flow numbers generated for exhaust side are misleading and not easily tied to how well the port works or if it is properly sized. And another myth dispelled, high low lift flow does not increase low end torque.

Some references that can help anyone wanting to research more I suggest Engine Airflow by Harold Bettes ISBN 978-1-55788-537-1 and purchasing Pipemax software by Larry Meaux. Performance Trends software also helps with CSA sizing.

Ohio HD

There is an estimated result from CFM. There are certain assumptions being made, like that the motor is designed optimally as one of the five options shown on the calculator.

Plugging a few numbers into this that I know to be true, it's fairly close.



http://www.wallaceracing.com/calcafhp.php

kd

December 08, 2021, 01:30:22 PM #32 Last Edit: December 08, 2021, 01:49:29 PM by kd
I looked up my 120 w/  MVA heads flow sheet and did a calc. from the Wallace Racing (horsepower from intake flow) calculator.  I changed the numbers from the spec sheet (22" to 28") and entered them at 28" because that seems to be what everyone relates to. I think my numbers are correct.  Before the heads were worked on we had a deep discussion on what I was looking for, which  cams were being used, throttle body, pipe(s), gearing and how it will be ridden.  I was told very little would be done to the MVA's because they were already good for what I hoped to get back but springs, valve profiles and exhaust sizes were done along with some fine tuning in the ports and seats.

He had my manifold and HPI 62/64 throttle body for blending etc.. IIRC these heads were tested with the manifold and TB.


Intake at  .600 lift - 309.11 cfm = 147 hp with a RPM Range of 5,213 to 6,713
         
               .700 lift - 319.27 cfm = 151 with a RPM Range of 5,428 to 6,928

With 660SM cams .660 lift - 315.81 cfm = 150 with a RPM Range of 5,359 to 6,859You cannot see attachments on this board.


I would say the calculator is pretty darn close (at least in my combination).  You can see by the dyno sheet the pipe can make the difference or the RPM.  This one was clipped at 6200 and may have put out a little more.
KD

Don D

Somewhere in that calculation is a VE factor. The VE makes all the difference of whether the numbers will be accurate or not. Many factors can screw up the VE, kd, in your case you had all the right  combination to make a high VE. I am referring to actual VE not the factors used in the tuning software. This is not always the case however and pipes hold a high weight on achieving a high VE along with the other factors. Ages ago I had similar results with a 120r tuned by Jim Kennedy and the bike had a wegner 2 into 2 pipe. The mva heads are a lot like what I described,  needing changes but capable heads. My point however is there is no broad brush that all the heads get except for an initial evaluation.

Ohio HD

The actual motor VE% is something that most don't have the resources to find out. Estimates like the three listed below can be used for estimating the motor output potential.


  Engine Type                          VE%

Stock motor, modern design  85%

Slightly modified motor*        100%

Highly modified motor**        115%


*Slightly Modified = performance cam, upgraded induction, free flowing exhaust

**Highly Modified = aggressive cam, large upgraded induction, racing exhaust, heads ported for maximum output, compression 11:1 or higher

hrdtail78

85% is decent to use for our built engines.
Semper Fi

Ohio HD

I don't doubt that's true, this is data I took from a book several years ago.

Ohio HD

So this is somewhat close to what Jason stated. I think the wild card in this formula is knowing what the actual CFM used is. I don't think it's meant to mean what the heads / intake can give, rather what the motor is using.



VE = (cfm x 3,456) / (c.i.d. x rpm)



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Ohio HD

I changed the output to percent.


VE = (cfm x 3,456) / (c.i.d. x rpm)



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Don D

I have Dynomation software for simulations and I have found the same, ~85% is about what our engines are at when the combinations are not too far off from optimum and no power adders are used. Choosing the VE is empirical data based on builds I have analyzed and knew their results on a Dynojet 250I inertia dyno with their assumed compensation for drivetrain losses VS a water brake dyno and horsepower at the crank. RWHP VS Brake Hp. But can we interchange RWHP and DJWHP? It is a little bit of a quagmire, in my opinion.

hrdtail78

FWIW, I also add 15-20% to the BSFC in car injector calcs.  There is one built into a tuning program that seems pretty accurate as well.  My plan is an actual flow meter on a bike, but the equipment I know how to do this with are not on everyday street ridden bikes, so.......  Don't know how great the info will translate over to actual useful data.  I have always just went big and if idle had to be 1100 for control.  That's what it is.

My initial belief is the BSFC is lower on M8's than TC's, but don't really have enough data to be convinced of that.  Too many variables.

Apologize if this is way off topic but kind of thought it fit into same thinking process.
Semper Fi

Ohio HD

I grew tired of trying to find clean used 110 heads. I snatched this set of NOS MVA heads without the original box. They just didn't get used for what ever reason. The sad thing is I bought these for a little less that the highest priced used 110 heads I had found.

These are just in case heads, I don't have any plans for them.




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rigidthumper

Ignorance is bliss, and accuracy expensive. How much of either can you afford?

HighLiner

There is a shop near me that is working on a new set of heads just not sure if they based them off the CVO style or not