35hp gx200, or 50hp gx390

Lets see if I remember this right: runner cross section area X 88,200 divided by the cylinder volume = the rpm of peak torque. (?) The McFarland formula I think its called. Now getting an accurate cross sectional area of the runner is the sometimes tricky part. Just try to do it on a dual plane small block intake. That should keep you busy. LOL.
 
Did you just mention cross section??? That's not a common conversation when it comes to these engines.. unfortunately.


Most kart guys are not engine savvy. Not many have a flow bench and dyno. Your knowledge is at the top of the food chain when it comes to these motors. Your flow numbers and hp numbers are impressive.
 
Lets see if I remember this right: runner cross section area X 88,200 divided by the cylinder volume = the rpm of peak torque. (?) The McFarland formula I think its called. Now getting an accurate cross sectional area of the runner is the sometimes tricky part. Just try to do it on a dual plane small block intake. That should keep you busy. LOL.

Calculating the RPM that you will make peak torque requires allot more than what your intake cross section is.
 
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Calculating the RPM that you will make peak torque requires allot more than what your intake cross section is.

Im aware of that. Hence the insertion of the question mark in my post. With all things remaining contant, something such as a cam profile change can move torque numbers though "cross section" remains the exact same. Not to mention header primary length. When Jim came up with the formula in question it was to help purchasers of intakes choose which one of many to buy and , more importantly, help in intake research and devlopement at Edelbrock. Clearly, cross section and its inclusion in the formula (which is incredibly accurate by the way) alone wont determine peak torque rpm but it does go a long way in doing so. Just trying to add to the discussion banter. Not trying to proclaim any absolutes.
 
With these small single cylinder 200cc engines all you need is 100cfm or less. Most and I mean like 98 percent of the builders on this or any website AINT GETTING 100cfm. So when I speak about 100-160cfm its beyound what most have experience with to even know what flow is to much.

Now, my 117cfm head will go perfectly with my 244cc motor. It will love every cfm
 
With these small single cylinder 200cc engines all you need is 100cfm or less. Most and I mean like 98 percent of the builders on this or any website AINT GETTING 100cfm. So when I speak about 100-160cfm its beyound what most have experience with to even know what flow is to much.

Now, my 117cfm head will go perfectly with my 244cc motor. It will love every cfm

Please explain if you can what happens when you get to much flow that hurts hp. I think not.
 
100 CFM is probably a lot more than a 212cc motor needs. You can calculate how many CFM a particular sized engine will use with this calculator. http://wallaceracing.com/intakecfm.php You would want to exceed this amount by a bit but the minimum Cross sectional area of the port if you assume a CD of 1 (which is max and you won't see it) can support a maximum CFM dependent on the CSA. To get flow over about 75-80 CFM you have to enlarge the Area of the port (CSA) and when you do that you will reduce port velocity. Depending on the skill of the porter he may enlarge the port more than it needs to be for X amount of flow. The reduced port velocity affects low speed torque as well as inertia efftect. (Ram Tuning) and also fuel atomization, all can contribute to lower average power.
 
Please explain if you can what happens when you get to much flow that hurts hp. I think not.

PD is who said that
But it is possible to get to much flow. But you're not gonna do it with a stock cast head. It's only hard to understand to people who have never done it before. But what happens is poor velocity, so bad it hurts TQ and HP.
If you don't understand velocity, you just need to do your homework.
 
Ole4 the key word in your post in "Probably". A 212cc motor properly buit with all the other corect parts would love a 100cfm head. Maybe even a little more as well. But because the majority of builders open heads flow 90cfm or less they will never know if they engine will take more.

I been running 100cfm a very long time ago, before there was a such thing as a predator or even clone.
 
What I have found in my testing is where and when the flow begins...
Example I can make a 14cc head flow 85cfm but that is a a peak lift of .350-.400 lift.
But from .50-.250 is not so great.
A 22cc head I can make flow great from .50-.250 then it levels off from .250-.400 lift. At 75-78cfm

The 22cc head has a broader torque and hp curve and develops power sooner than the 14cc head.
The 14cc head is more of a "peaky" torque and hp curve... And develops its power later in the power band, but is sort of flat in the lower area of the curve...

This is just my findings with the work I have done anyway..
 
What I have found in my testing is where and when the flow begins...
Example I can make a 14cc head flow 85cfm but that is a a peak lift of .350-.400 lift.
But from .50-.250 is not so great.
A 22cc head I can make flow great from .50-.250 then it levels off from .250-.400 lift. At 75-78cfm

The 22cc head has a broader torque and hp curve and develops power sooner than the 14cc head.
The 14cc head is more of a "peaky" torque and hp curve... And develops its power later in the power band, but is sort of flat in the lower area of the curve...

This is just my findings with the work I have done anyway..

Your not getting the right shape in your port. Get Young Engine guy some pics of what you are doing. He has this head figured out and seems like a guy that wants to help. Raise the port and streamline your valve guide. Remove very little from the floor as you approach the seat. The radius approaching the seat is critical. The floor of the port needs to be somewhat wide approaching the seat. Remember how important your head is. Buy one from an experienced head porter and you will learn allot. My porting knowledge comes from seeing the very best work. Then learning from their shapes and countless hours on the flowbench and dyno.
 
PD is who said that
But it is possible to get to much flow. But you're not gonna do it with a stock cast head. It's only hard to understand to people who have never done it before. But what happens is poor velocity, so bad it hurts TQ and HP.
If you don't understand velocity, you just need to do your homework.


I have been working on a UAS motor the past two months. We put the existing and very powerful and winning motor on a chassis dyno. On the new motor we used a head that allowed larger ports to be cut and increased the intake valves {4 valve per cylinder 450 Honda} by 2 mm. Installed a larger cam and slightly larger header. We picked up 13 hp at the rear wheels at almost every RPM. We are better than 2.5 hp at the rear wheels. I suppose we flowed too much air. 320 CFM btw

Flowing too much air defies all logic to anyone that has serious engine knowledge. You are either getting your shape wrong or your cross section so large that you cannot keep your fuel suspended. The shape of the Honda head is very poor anyway and will have this tendency. You don't know what you don't know.

I must say, you do weld better than I do.
 
Ultimately the importance of potential flow, is very secondary to another set of factors. Name one....or two.

It's just too easy, to pick up on a point....like ultimate air flow....and elevate it to a position which it does not deserve.

The reason for doing that is that it is a lot easier to pick up a grinding wheel and remove material than it is to study at a professional level, the place and condition of air and fuel flow, particularly as it crosses the threshold from port to combustion chamber.
 
If you don't understand velocity, you just need to do your homework.
Correctomundo!!
See Smokey Yunick quote: "...there are 3 critical aspects to fuel/air flow in the heads of engines.
Those three factors are: 1.Velocity 2.Velocity 3.Velocity!!

Now Mr.Minibiker.......maybe it's time to concentrate of flow characteristics, and cylinder fill, and not so much
on flow! Remember, you can take a soup can, make it into a head port and have more flow than a blown Chrysler hemi.
It's like the little 3rd grade boy who kept pestering his little girlfriend to "reveal" herself. When she finally
succumbed he said: "...now that I got's it....what does I do with it."
So....you got a klillion gallons of air flow. Tell us more .... like...."what does you do with it?"
 
FWIW here is a formula I use in my excel spreadsheet that calculates airflow requirements based on size, RPM for peak power, VE. It came from Larry Meaux on the speedtalk forum. He also posted lots of other useful engune math formulas.

Flow = ( CID * RPM * .000978474 * Ve% ) / ( Cylinders * 127.5 )
where
Cylinders = Number of Cylinders
127.5 % Ve = theoretical VE possible at .60 Mach or 699-700 fps
Note=> that 127.5 theoretical Ve is also dependent upon piston speed
and that at lower piston speeds even if there is .60 Mach, its not possible to achieve 127.5 %, but much less

This is not a absolute but has worked well for me over the years. It does not care about low lift vs high lift flow or velocity but just tells you how much airflow is required thru the intake system, aircleaner thru valve to fill a cylinder of X size at a VE of X% at XRPM.
 
PD you aren't saying anything

Facts are facts, and I see nothing has changed over the years. Im the only guy "still" doing actual R&D.

Oh and a 450cc motor using all of that 320cfm. It's possible, because its 450cc.
 
PD you aren't saying anything

Facts are facts, and I see nothing has changed over the years. Im the only guy "still" doing actual R&D.

Oh and a 450cc motor using all of that 320cfm. It's possible, because its 450cc.

Do the math. That is 160 cfm for 225 cc. You don't have a flow bench or dyno and a somewhat limited understanding of a race engine. So you just assume that you are the only one doing R&D. I would love to make a living racing you. Where are all of these world beating motors? Your pictures show that you are not an accomplished head porter. You are a self promoter that has allot to learn.
 
Do the math. That is 160 cfm for 225 cc. You don't have a flow bench or dyno and a somewhat limited understanding of a race engine. So you just assume that you are the only one doing R&D. I would love to make a living racing you. Where are all of these world beating motors? Your pictures show that you are not an accomplished head porter. You are a self promoter that has allot to learn.

How do you know what I have?
And that design of a engine is totally different from a gx200 Honda. What you can do is build you a 225cc gx200 and bolt on a 160cfm head. Run it and then report back your findings.
 
The issue is if you get all those flow figures at the expense of velocity.
When you can fill in the bottom of the port and make no difference to flow figures you know you have to bigger ports.
If you velocity is to low your going to get reversion when the piston hits bdc and is starting to come up the bore.
I suggest you read up on david vizards stuff as well
 
I already know what works WAX. I make more power than anyone on this site building a gx200 motor. I have years of R&D behind what I post.
 
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