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Cylinder Head Flow Ratio. . .

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Discussion starter · #42 ·
formula fastech said:
I'm not looking for an argument. You made the statement that cam companies just want to sell cams. So why is Chris any different? He wants to sell cam specs correct?
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Zone,Formula, Zimm. . . .
Your wrong on the statement I just want to sell cams. If there is room for improvement of 10% or greater in power then I tell the customer this. If a cam change is going to net less then that I suggest the customer doesn't do it. I have had told several people after comparing the numbers a cam change is not worth the $$ spent. Kaama was one of them, I told him what he had was within 3% of the best choice.

Chris
 
#43 ·
Kidnova said:
I think it's time for CFM to post a smiley, referring to a wedgey :D
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I actually can't find a wedgey. Must be a first I can't find one.

How about lighting someone's butt. it's a little more painful probably. :laugher: :laugher:

<a href='http://www.smileycentral.com/?partner=ZSzeb008_ZNxdm006YYUS' target='_blank'><img src='http://smileys.smileycentral.com/cat/10/10_1_128.gif' alt='Hot Butt' border=0></a>
 
#45 ·
Kidnova said:
Mr. smiley should make use of his methane gas :eek:
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It's all in the timing, I just can't get it synched right. :dead:

<a href='http://www.smileycentral.com/?partner=ZSzeb008_ZNxdm006YYUS' target='_blank'><img src='http://smileys.smileycentral.com/cat/10/10_15_6.gif' alt='Fart In Face' border=0></a>

<a href='http://www.smileycentral.com/?partner=ZSzeb008_ZNxdm006YYUS' target='_blank'><img src='http://smileys.smileycentral.com/cat/10/10_1_128.gif' alt='Hot Butt' border=0></a>
 
Discussion starter · #46 ·
smittyseng said:
So Bob,would you add the i/e ratios at each point of measured lift and then divide it to get a average OR is there a certain lift point where i/e is most important that you would add then divide on a smaller scale,Smitty
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Smitty,
Can't speak for Bob but the way I figure it is find what my max lift is going to be the ratio I am using. I then plot the I/E ratio at seat, .050, 100, 200, 300. This gives me the lobe profile I am looking for.

Chris
 
#47 ·
cfm said:
It's all in the timing, I just can't get it synched right. :dead:

<a href='http://www.smileycentral.com/?partner=ZSzeb008_ZNxdm006YYUS' target='_blank'><img src='http://smileys.smileycentral.com/cat/10/10_15_6.gif' alt='Fart In Face' border=0></a>

<a href='http://www.smileycentral.com/?partner=ZSzeb008_ZNxdm006YYUS' target='_blank'><img src='http://smileys.smileycentral.com/cat/10/10_1_128.gif' alt='Hot Butt' border=0></a>
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synched :eek:
 
#48 ·
formula fastech said:
I'm not looking for an argument. You made the statement that cam companies just want to sell cams. So why is Chris any different? He wants to sell cam specs correct?
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He routinely stays with the customer to find out exactly how things worked out.

Send me the dyno sheet.

Tell me how it ran.

What was the improvement or loss on how it runs.

Etc, etc, etc.

All this goes into the knowledge bank for the same customer and customers to come.

======================================
Primary questions are much more involved including the exact customer wants and needs.

Off the shelf cams can make real good power if chosen correctly. I don't think that's the issue we are going against.

Do you want to make some more power ? Do you want your engine to do more of this vs this ? What is more important to you ? etc, etc, etc, etc.

Does a vehicle computer programmer like Hypertech or Superchip know exactly what someone is looking for? No. They come up with a program that they feel the most people will be happy with. Chances are a custom programmer that will interview you will make your vehicle drive the best it can according to YOUR wants and needs. Transmission shifting, converter lock-up, grades of gas, what kind of driving, easy on throttle or hard on throttle, added weight on bed, towing, other mods, etc, etc, etc.
 
#49 ·
cstraub said:
I have had told several people after comparing the numbers a cam change is not worth the $$ spent. Kaama was one of them, I told him what he had was within 3% of the best choice. Chris
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Just so everyone has got it straight....when my 565cid engines came back from Jack Bailey/Budah they had a 220*/220* .560"/.560" lift on 112* lobes in them. We removed them when disassembling the engines and had them spec'd out on a Cam Doctor and decided not to use them as they were obviously way too small for the RPM's I wanted to run up to (about 5500rpm or so).

Once the engines were remachined and being assembled, on my own I solely decided on a Reed Cam 232*/238* .578"/.578" lift on 112* lobes. These were being used in conjunction with the AFR 357cc cnc ported heads at the time. It was during this time I was confering with both "cstraub"/Chris and "rmbuilder"/Bob and that's when Chris basically said that he felt it was close enough. However, things changed from there and found myself talking with rmbuilder/Bob more, and more and I decided to use a smaller head, and didn't end up using the 357's because I felt they were too large for my application and RPM range I wanted to run so, while the engines were still in the assembly room I had my builder remove them and the Reed cams, and went with the smaller 315cc AFR heads and wanted "rmbuilder/Bob" to tweek the cam specs and experiment with something a little different---besides my engine builder and I weren't real confident with the core material that Reed was using, and wanted to use a cam with a better core material/finish quality that I trusted, so we ended up going with a different cam manufacturer/profile than Reed.

Anyway, I asked rmbuilder for his help on the project and the cams I chose (ended up with) were originally NOT Bob's frist choice in duration for a 565cid marine engine, but he pledged that he would work with me for what I personally wanted to do with the engines with the size of heads I was using, etc. I told him that the FIRST prioirty was a smooth/low RPM idle with excellent shifting/drivability, etc and still be able to make power up to about 5500-5600rpm, then torque/throttle response---HP was last on my priority list although I knew it would make a decent amount of HP. It was kind of an experiment, and wasn't the easiest thing to accomplish as we were trying to go in two different directions with the cam design and still give it a profile that was easy on the valve train, but even so, we still had fun with it. I could have used either Chris or Bob, but I felt Bob was the right man for the job and was great to work with. He engineered the head, and cam combination and I am thrilled with the results---can't argue with success. :)
 
Discussion starter · #50 ·
Kaama,
Thanks for the post. I don't look at a sale as $$, I look at it as something that can solve a problem. "You need more power to go faster?" Okay lets see what the best plan is and make it happen. That's how I approach things and respect Bob and Scott because they do the same thing.. . .solve the customers problem.
 
#51 ·
KAAMA said:
Just so everyone has got it straight....when my 565cid engines came back from Jack Bailey/Budah they had a 220*/220* .560"/.560" lift on 112* lobes in them.
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These cams where used with the CNC 357 AFR's ?
Where you told this was the cam being used ?

Sounds weird, thus my interest is peaked.
 
#52 ·
cfm said:
These cams where used with the CNC 357 AFR's ?
Where you told this was the cam being used ?

Sounds weird, thus my interest is peaked.
Click to expand...
CFM,

Yes, the 357cc AFR cnc ported heads were being used with a 220*/220* hydraulic roller cam in my 565cid engines.

No, I was NOT told cams of this duration (220*/220*) were being used. I was originally told that the cams were a custom grind for my application---at least that is what I was led to believe, and paid for. Even after we pulled the engines down I was finally told what the specs were, but ultimately found out they were still something way far apart. The cams had the I.D. numbers, etc ground off the ends so, the only way I was going to really know was by having both cams spec'd out on a Cam Doctor here at a local machine shop.

I was told one engine made 787hp @5800rpm and the other something like 792hp with the above cam/heads with 9.3 comp ratio, on my pair of naturally aspirated 565cid marine engines with a single carb---which sounds a bit far fetched to me. There just ain't no way!!! I never did get the dyno sheets. I never did install those engines the way they came either. It was a mess....and we had to tear them all the way down and start all over. It's a long story--------water over the dam.

I needed to find people I believe I could really trust ----AND know what they're doing. My engine builder (Dave at WESCO) rebuilt my engines. He, and Bob Madera/"rmbuilder" worked together on my project. I believe they are people of integrity.
 
#54 ·
smittyseng said:
So Bob,would you add the i/e ratios at each point of measured lift and then divide it to get a average OR is there a certain lift point where i/e is most important that you would add then divide on a smaller scale,Smitty
Click to expand...
Smitty,
I actually have 3 programs I use to evaluate heads, one I wrote and two were supplied to me.

The first has data input for flow depression /valve size/airflow from .100" - 1.00" lift that calculates and graphs flow/discharge coefficients/effective flow area/Actual flow area at all points and then averages the totals.

The second plots/graphs/overlays flow curves for up to 4 cylinder heads for comparative purposes.

The third inputs, port size/flow/I/E ratio at all points/averages the totals/measures flow per unit of port size, then graphs and overlays them.

Your question about "most important lift point" is widely debated. One of the best summations I have seen is by Bret Bauer (Engine Masters Competitor) and Darin Morgan of Reher-Morrison.

"Hyd Roller over .600 lift (.630 range) medium sized duration, sub 7500rpm and a "street motor"

.000-.100 68 degs 22%
.100-.200 40 degs 13%
.200-.300 26 degs 8.5%
.300-.400 34 degs 11%
.400-.500 32 degs 10.5%
.500-.600 60 degs 20%
.600 + 44 degs 14.5%

Now making a negative change in that motors flow curve from .200-.400" lift of 4.4% nets less than a 1% loss in max power and about .4% in average power. Now if you killed the flow at the top end (.600+) 4.4% you would see a 1% loss in average power. This is with big changes in flow of 15-20cfm at the top end. That's 150% more loss in average power.

To add a little more to this the lowest pressures seen in the port (highest vacuum) at the max VE occur between .420-.520" lobe lift (opening) and the highest pressures occur between .150-.020" lift (closing), from lowest vacuum to highest pressure there is roughly a 15psi change in pressures. The highest average velocities occured for 84 degs at lifts over .500". The more flow you have in that lift area will raise the amount of duration that the motor pulls that high of a velocity given the same sized port.

So you can see the time when the port is filling the motor the fastest is around max lift, and the time it's filling it with the most pressure is around valve closing while the piston is coming up the bore.

Bret"

Looks like the valve spends:

35% of it's time below .200"
30% of it's time between .200-.500"
35% of it's time between .500-.630"

So just in time/duration (they are the same things when talking about a cam) the midlift area of the curve is the part where the valve spends the least amount of time. It's suprising that the valve spends 35% of it's time in the top .130" of travel on that camshaft. Even if you limit the valve to .600" lift on a standard LS1 setup the valve spends a significant portion of it's time there. That's a lot of time devoted to a small area of lift. It's also the most common place for a LS style head to go turbulent at very high depressions. (which you say you have seen) So MOST guys aren't filling the port effectively in that area. This is mostly due to lack of attention to the short side radius.... too much velocity in the port at this point. That's a bad thing when the highest velocities and volumes are moved thru the port at these lift points.

The problem most people don't get is that the wave tuning effect of length and cross section on a port add a natural supercharging effect "resonance tuning" to a NA motor. This will make the pressures in the head port much higher than atmosphere (5-7psi) vs. the vacuum on the port will ever reach.

Originally Posted by Darrin Morgan
There are many proponents of the " flow curve must match the camshaft lift curve" theory but I am not one of them. Some people still believe that if the camshaft has a maximum of .700 lift that the area under the flow curve must be maximized in this area as well and anything that happens to the flow curve after .700 lift is of no consequence. Nothing could be more incorrect I assure you! Its like that old theory about 30 degree seats. They flow more down low ( .050 to .350 lift ) so they should make more power for cam profiles at or slightly above .400 lift because they maximize the area under the curve in that area,right? Wrong. You can put a properly designed 55 degree seat and chamber, decrease the flow at .050 to .400 lift and make more power with cams with only .400 lift. You have to design the thing correctly and its tricky. You cant just throw steep angle seats in any head and have this work. You must have convex chambers and good pressure recovery in the chamber or its disastrous. The steeper the seat angles and the larger the throat area, the more important the chamber design becomes.

You turn the air less, use less energy doing so.
You maximize the potential flow in an area more conducive to flow from a piston speed stand point.
You have proper pressure recovery in the chamber ( Equal exit velocity around the entire circumference of the valve head. A controlled deceleration of the air like a venturi divergent angle.)
You get more air fuel mixture in the cylinder.
It makes more power.

That's my theory and I am sticking with it until someone can come up with a better one.LOL

I bet thats more information than you bargained for, but it's good reading!
Bob
 
#55 ·
rmbuilder said:
Some people still believe that if the camshaft has a maximum of .700 lift ......and anything that happens to the flow curve after .700 lift is of no consequence. Nothing could be more incorrect I assure you! Bob
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I'll keep reading the rest to fully understand and sink in, but HV talks about the above all the time to me. There are several Brodix BBC heads that make good #'s to a lift point - point being where a lot of cams reach - but then suddenly level out and/or drop a little. He doesn't like this characteristic at all and spends a lot of time (ie: porting and thus customers $$$) to change it.

Thus part of the reason why the Can's flow the way they do. :bigsmile:
 
#56 ·
CFM,
Great point! If a head starts backing up (up to .100"-.150") past peak lift it can significantly hurt power even though you are well short of the "back up point" with your cam. I worked an engine project with a gentleman who had his heads flowed at Katech and each port was noted where it went turbulent. Thats why their Katech!
Bob
 
#57 ·
rmbuilder said:
To add a little more to this the lowest pressures seen in the port (highest vacuum) at the max VE occur between .420-.520" lobe lift (opening) and the highest pressures occur between .150-.020" lift (closing), from lowest vacuum to highest pressure there is roughly a 15psi change in pressures. The highest average velocities occured for 84 degs at lifts over .500". The more flow you have in that lift area will raise the amount of duration that the motor pulls that high of a velocity given the same sized port.

So you can see the time when the port is filling the motor the fastest is around max lift, and the time it's filling it with the most pressure is around valve closing while the piston is coming up the bore.

Click to expand...
Sorry to butt in again, but this particular part is what I've been looking for.

Gracious. Your helping me age graciously. :bigsmile:
 
#59 ·
This is a little above my level of knowledge, so I'm really interested in what's being discussed here. I'm also a, for the lack of a better term, "follower" of Larry Widmer. Here's something he wrote regarding ports and flow. I'd be interested to get your take on his ideas. It's a little more basic...not quitr in as much detail, but still covers a lot of what you were talking about.
Thanks in advance.
Now I'll address your head related questions: With the exception of blown applications, ports don't just flow one direction. Intake ports pulsate back and forth, and exhausts flow backwards too. This occors primarily at overlap, when the cylinder still has positive exhaust trying to exit the exhaust port ...where header back pressure is pushing backwards. Now the intake valve (which is larger in diameter) opens, and exhaust gasses seeking the path of least pressure take the easy way.....the intake port "exit". This is not a good thing because besides turning the intake port black "reversion" also contaminates the intake charge with inert gasses which will not burn again. My studies showed a direct correlation between low lift intake flow and reverse flow.....The better the low lift flow on an intake port, the better the tendency for reverse flow, or sucking exhaust. I designed my intake ports to not flow worth a **** at low lift, and also to not flow backwards. I'll not detail how, but the approach to the inlet valve seat, and its blend to the chamber are how it's accomplished....remember the seat is only the 45 degree angle that's ~ .055" wide. were not talking about the seat ring itself. The assymetric shapes I developed for that area and the last .5" of the intake port (the wierd valve job) are why the port doesn't dare flow backward, and as for low lift flow......study the piston velocity when the valve's at .150" or less. You'll find that it's so slow that the port's not being sucked on at all(relatively speaking), so big flow #'s at low lift wouldn't do you any good anyway. If I had known how to design an intake port that flowed 0 cfm. up to .150" lift, I would have, but all things considered my "weird seats" worked well for their time.
Exhaust ports: Read my Re. to RX first. I've never had much luck with performance of engines with no exhaust valves, so I've never been inclined to design exhaust ports without valves included. All I'll say is that the some flow attaches itself to the head and stem on the exhaust side, so the valve is somewhat like a guide for flow. The thing you're missing when flowing with no valve is that the valve stem represents part of the cross sectional area of the port, and, as previously stated areas are critical when dealing with velocities over mach 1. My port phylosophy has always been to calculate how much air a given displacement engine needs to run at a given rpm range (taking into account the many variables such as bore / stroke / rod length, and of course rules), and design a high velocity intake port that's not too large or so small that the velocities will cause separation of a well prepared air / fuel mixture. With valvetrain life in mind, I also attempt to achieve highest flow rates at crank angles where piston velocity is highest (greatest sucking power). If you can obtain 90% of your max. flow rate at mid lift, you don't need to run a cam with spring killing lift. As for the exhaust side, lalve lift and the additional heat kill springs, so the more you can flow, the less lift is needed, and if it's real good you don't need to open the exhaust valve before BDC on the power stroke, releasing that last bit of cylinder pressure pushing on the piston, and you can close it earlier too. Most "head experts" agree that the exhaust should flow 80% of the intake, and assuming that they're talking flow with the manifold / injector installed, and the header on the exhaust, that's ok. But if I can design an exhaust port that flows twice the intake port flow, I will, because it allows you to run less lift and duration which makes springs happy, and on an engine like the Ford BOSS 429 remember the exhaust rocker arm is about 5" long, and I don't care what you make it from, all that mass takes considerable spring to control, and the less you move it the longer all the parts last. Over the years I've had customers go in and **** up my ports so the flow will be less allowing them to run the same cam they used to. What a world
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#60 ·
steelcomp said:
My studies showed a direct correlation between low lift intake flow and reverse flow.....The better the low lift flow on an intake port, the better the tendency for reverse flow, or sucking exhaust. I designed my intake ports to not flow worth a **** at low lift, and also to not flow backwards. .........
......study the piston velocity when the valve's at .150" or less. You'll find that it's so slow that the port's not being sucked on at all(relatively speaking), so big flow #'s at low lift wouldn't do you any good anyway.
Click to expand...
Very interesting.

Super interesting when dealing with water in the exhaust too. :bigsmile:
 
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