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Discussion Starter #1 (Edited)
Hey Guys,

I spent some time searching and I cant seem to find definitive numbers, not that are conclusive at least.

The closest I found was an old report for a Y8 that had a broken link and the host didnt exist anymore, or in the Y8 Vs Z6 comparison thread a link that wasnt all there and never actually got the URL Transfered.

I have this, but I have some issues with it.
Y8 head with professional 3 angle valve job and DIY porting - improved flow by 7-8% across the board with max corrected flow in the 205 cfm range at max lift.

Z6 head with professional 3 angle valve job and DIY porting - improved flow by 5-6% across the board with max corrected flow in the 210 cfm range at max lift.
First thing is Im looking for CFM on a STOCK Y8 and Z6 Head. and
"at max lift" does Not tell me a DAMN thing.

I'm looking for,
At 0.100" Lift, 53 CFM is generated. Creating an air curtain of 0.5906 square inches with an efficiency of 89%, measurements taken at 28 In/Hg.

I saw some information that was taken at 10 In/Hg.

I also saw this,
a stock Y8 head flows about 190 cfm on the intake side and 160 cfm on the exhaust side.
That tells me absolutely nothing...just with whatever lift they chose, with whatever valves, and god knows what in/hg they got 190cfm...

and then also this crap

Here's the baseline Y8 data Joe Alaniz sent me, measured at 10'' of H20:

.100 43cfm
.200 83cfm
.300 99cfm
.400 106cfm
.500 109cfm

On the other hand, here's the data I have for my ported Y8 head (intake) measured at unknown depth of H20:

.100 81cfm
.200 148cfm
.300 181cfm
.400 201cfm
.500 204cfm
Unknown depth...really...It kinda helps to know what they're using for pressure.

And also, who in there right mind takes flow bench readings at 10 in/hg!!!!!
25 is the industry standard, however 28 in/hg is the most accurate.

And no one seems to go until the head stalls....so you dont really know where to stop... Not seeing anyone out at .600 and .700 lift.
I want to know where the head stalls.

All I need is the lift/CFM readings, I can figure out the curtain myself and the efficiency.
So either someone with access to the proper equipment or USEFUL readings...please give me some information.
 

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Discussion Starter #2
End of day bump.

Has no one really had their head flowed???

You mean to tell me that all you guys are throwing these nasty Crower/ZEX/Bisimoto cams in your head's without even knowing how the head flows???

It may be personal opinion, but I think thats probably the dumbest thing possible...throw a gnarly cam with .400+ Lift in your head and you dont even know where the head stalls....
 

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I don't think most of them on here are using the big cams. I my self, If i was ever to really build one of these little beast I would get the head flowed. Knowing what the head flows will help you pick cams and or tell you what cam will be best at what rpm. It will help to match your parts better so you get the most out every little bit. There are so many pluses to flowing your head. I'm sure BISI flows all of his stuff.
 

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End of day bump.

Has no one really had their head flowed???

You mean to tell me that all you guys are throwing these nasty Crower/ZEX/Bisimoto cams in your head's without even knowing how the head flows???

It may be personal opinion, but I think thats probably the dumbest thing possible...throw a gnarly cam with .400+ Lift in your head and you dont even know where the head stalls....
Mike @ Hi Flow Heads in alsip will be doing my head AND flowbenching it, however, I'll be running the bisi 3.6 cam without flow information....what kind of issues do you see with that?
 

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So either someone with access to the proper equipment or USEFUL readings...please give me some information.
Hmm.. I go halfs with you on a custom fabricated adapter plate for Hi Flow Heads flow bench. Could be 100-200 bucks; and I was going to do it anyway next season for my second build.

Then we can get some flow infos.
 

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Formerly 95RedVXCivic
95 VX, 88 S/C MR2
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interested in more info...
 

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Discussion Starter #8
Mike @ Hi Flow Heads in alsip will be doing my head AND flowbenching it, however, I'll be running the bisi 3.6 cam without flow information....what kind of issues do you see with that?
Elaborate on doing your head? Im going to assume you mean a port and polish job? in which case damn right he better flow it before P&P!!! anyone who ports and polishes a head without flow data is nothing more than a farmer with a dremel.

Here's the relationship. For example, lets say I work for a speed shop, lets say. NightCats SpeedShop here in good ole Colorado. And I have a customer come in. lets say...Mr. D-Serious and he says to me

"Hey Dave, I have this car, its a civic with a sohc 1.6 engine in it, and I want to make 400whp." Or he says " I want to run an 11.5 in the quarter"

Well, first thing I do is the MATH. yes..MATH.

First thing, is to figure out what his airflow is in his cylinder heads. Lets say, on his stock head and stock ports, I flow it and at 0.500" Lift I see 210cfm. and then a 0.550" I see 205. I know at about 0.500" lift his head stalls.

Okay, now before I even suggest doing a valve job or port and polish on the heads, Im going to see how much CFM I need to generate 400hp.

So I use the following formula. Hp / 0.2575 / # of cyl. / .7

400/0.2575/4/.7
If this were a RACE ONLY motor, I would put it " on kill" and remove the .7 All that does is say were using 70% of the engines ability but NOT on a street/strip car do you run on kill. thats dangerous and highly stressful on the engine.

So...From our math we get 544.78 CFM.
If we were to run ON KILL being that it is a RACE ONLY motor, we would need 388.35CFM.

But seeing as it isnt, we're going to use 544.78 CFM.

I know that your head flows 210 @ 0.500" lift...well now we have a problem. I'm 334.78CFM short of having enough air flow to create 400whp.

So now I know, I should gather more data on the head. So what I'm going to do next is take your head over to my handy dandy flow bench and start getting some numbers. First thing I know off the bat after flowing it though is that we either need to Boost the hell out of it to make up our CFM difference, or Port and Polish it and still boost it. Or get some N20 in there.

Next I'm gonna flow your head again at all different valve lifts so I have an idea of how the head functions. I'll go in 0.100" increments for examples sake.

I'm going to want the following information.
0.100". Intake CFM, Intake Curtain Area, Intake Efficiency.
0.100" Exhaust CFM, Exhaust Relationship %, Curtain area, and efficiency.

From those numbers I see that maybe the efficiency is down on both sides, so I'm gonna start doing what I need to to raise that. And because we're going with a Forced Induced motor, I'm going to shoot for a 70-80% relationship.

and by relationship I mean the percentage different from your Exhaust CFM/ Intake CFM.

For FI you want about 70-80. Different engine builders go higher or lower, I chose 70-80%.

So...now I know what I need to do to get the desired air flow into the engine to make your power...now we have a Metallurgy issue.

Can you spin the engine high enough to get this desired air flow and NOT kick the rods out...does my client, Mr.D-Series have a forged rotating assembly, did he chose the right ring pack, what cam is going to use? now I need to know a whole lot more.

Regardless. YOU BUILD YOUR ENGINE AROUND THE FLOW BENCH.

Sweet dude!!! you have this awesome Darton sleeved block, 78mm CP Pistons, Crower Rods, GE crank, ACL Race bearings. All this great stuff and you have just an awesome bullet proof short block...

but your heads you just slapped some shit together cause some guy told you it will perform.

If we have an issue with your heads, say that your relationship is over 80%, meaning your exhaust flows more...well now I have to port your intake.

Because you let your idiot friend with a dremel start grinding away at your head to make it all shiny and look good, now means I have more work to do.

Your heads need to flow about 70% of your CID at a minimum. And generally no more than 90%. If you're over 90 then you'd really benefit from more displacement.

Regardless.....now I'm back to my other issue. you told me you want to bust off some 11.50's at the track! so I get to do some more math..

I have to look at what a car would ET at if they ran 11.50's. and note the MPH is nominal, its for the perfect conditions, you dig good, you dont have issues. we all know if you ET 11.50 and your MPH is like 140....you did something wrong. you spun out the hole, your car is too heavy, driver issues...etc.

So, perfect world, 11.50, you'll MPH at 118.5mph. Now I do some math..
and for this I need a vehicle weight, so unless you weigh the car I'm gonna use a nominal number close to the car. lets say 2500 lbs.

I now go, (118.5 / 234) (cubed) x 2500 = 324.67 hp
324.67hp is what is REQUIRED to accelerate a car weighing 2500 lbs to 11.50s in a 1/4 mile. Period!!

Next I need to figure out airflow for 324.67 hp.
(324.67 / .2575) / 4 / .7 = 450.31 CFM.

Now once gain, if your head blows 210...we have an issue. I'm shy 240.31cfm of being able to hit your goal. So we DEFINITELY need a power adder.

This is why you NEED a flow bench. Not to mention you need to work out your shift point to see what you need to tach out too...then you need to work your piston speed to see if your metallurgy can even handle it..

but yea....I think I made my point.



Flow bench readings are typically taken at 28" water, not 28" mercury. 28" mercury is an insane pressure drop.
I apologize, I meant to say water not mercury. Thanks for that!
 

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yay now I can get my head work done. shooting for 350-400 hp. with turbo
 

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Discussion Starter #10
yay now I can get my head work done. shooting for 350-400 hp. with turbo
What sort of set up are you looking at running? I'm at 376 @ 7k right now and looking to go to 415-420...its definitely easy to do.
 

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Uhh wow some guys take engine building on a Honda platform that's been around for 25 years waaaaay too serious. We don't need stinkin flow numbers on shit that we know works from YEARS of doing it. Sounds like you are trying to re-invent the wheel here when we don't have to. We know what works, what doesn't and going about it and worrying about numbers is meh...kinda pointless. Its been done over and over and over and over....


 

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The Great Weldini
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anyone who ports and polishes a head without flow data is nothing more than a farmer with a dremel.
well, i guess i'm a farmer.. woo hoo, i have my waiters on and you shure have a purrty mouth, son.
Uhh wow some guys take engine building on a Honda platform that's been around for 25 years waaaaay too serious. We don't need stinkin flow numbers on shit that we know works from YEARS of doing it. Sounds like you are trying to re-invent the wheel here when we don't have to. We know what works, what doesn't and going about it and worrying about numbers is meh...kinda pointless. Its been done over and over and over and over....


:bigrofl:
 

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Elaborate on doing your head? Im going to assume you mean a port and polish job? in which case damn right he better flow it before P&P!!! anyone who ports and polishes a head without flow data is nothing more than a farmer with a dremel.
NightCat, thanks for the informative post. I am looking to do some portwork, oversized valves, and a valvejob.

What happens if you shoot *over* the necessary cfm? Is that detrimental? You say it's higher for setting motors 'on kill'. Can I run an 'on kill' motor at a roadrace course and flog on it?

For my 700+whp goal for next season; some serious headwork is going to be required. Right now without sleeves I'm shooting for 450-500whp. Is it ok to account for the 700whp goal in my head build now?
 

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Uhh wow some guys take engine building on a Honda platform that's been around for 25 years waaaaay too serious. We don't need stinkin flow numbers on shit that we know works from YEARS of doing it. Sounds like you are trying to re-invent the wheel here when we don't have to. We know what works, what doesn't and going about it and worrying about numbers is meh...kinda pointless. Its been done over and over and over and over....


Come on man, the guy is handing out the kind of knowledge that takes quite a while to put together and understand. No need to call someone out for being too particular about his own builds or work.
 

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we need to see more stuff like this, its nice to see people who apply the theory before they go balls deep into everything,

i'm a big math guy as well, where did you get all these equations from? or what were the eq's you used
 

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D-serious--downside to overshooting is loss in velocity which is a much worse problem then not flowing enough air.

I had my intakes flowed. I'll see if I still have the sheet

-Luke
 

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nice post.
I take it you have put a few civic heads on the flow bench.

By chance would you be willing to share with us. The flow data for a stock Y8 head.
(And if your a smart marketing guy)
What you where to pull out of it after you ported it.

The head Im interested in is the Y8 head.
 
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