900 HP motors flow about 250 exhaust. Having big exhaust ports is more of a phallic validation than engineering necessity. Huge exhaust numbers are unnecessary in 600HP motors and less. Only people who get off on numbers and know little about how a motor works worry about exhaust numbers being large, engineers don't. The fact that a small block head flows 200 plus on a dry bench (in and of itself a useless measurement) adds nothing to performance.

I am currently talking to 4 highly qualified engineers who are well versed in fluid dynamics and whose area of specialty is specifically related to this specific arena. They are not EEs or Civil Engineers. They all had the same response about exhaust flow over 200 on a small block, a chuckle...bordering on a laugh.. wholly irrelevant at any of the power levels discussed here. Well, hell look at this motor, even at THAT power level seems unimportant. Wouldn't you say? Or you can assume Sonny doesn't know WTF he's doing.


The short, sweet answer is that the exhaust port is always at a lower pressure than the cylinder so the exhaust gases get blown through the exhaust port as the piston moves upward on the exhaust stroke. Also, the exhaust system design plays a HUGE role in flow through the exhaust port due to wave harmonics sucking the gases out of the chamber.

Hope it helps.

 

JSUP,

Interesting thoughts but far from reality when we are discussing street/strip pump gas engines that run full exhausts (some with catalytic converters) and camshafts that are night and day different in their design (Sonny Leonard mountain motors have zero in common with anything we are discussing that could be of any real benefit to those reading this). This is the kind of post that starts the spread of bad information on these message boards....

In the real world your 200 CFM exhaust port will work "OK" on a 270 CFM intake port but will not cut the mustard on a higher flowing 300 CFM intake port unless you crutch the crap out of it with a huge exhaust to intake split in the cam design. And that's no free lunch because it increases overlap, reduces low/midrange TQ (as soon as you crack that exhaust valve your cylinder pressure working on the piston goes bye-bye) and dirty's up the idle quality and fuel economy as well.

And I have to chuckle at your expert assessment (concerning flow numbers) that dry bench flow values are now a useless measurement

Aaaahhh.....the power of effective marketing/advertising. Lets not forget you have thirteen parts air (to every ONE part fuel) moving thru those intake ports and combustion chamber. Design an efficient high speed port that moves alot of air and for the most part proper fuel atomization takes care of itself (a problem with ported stock heads that need much more volume to achieve the same flow a well design clean sheet aftermarket approach can accomplish with less). Ultimately its the airflow your engine is capable of processing that's going to hinder or determine how much power the engine is able to generate. Focus on effectively moving alot more of it and watch the dyno numbers swing higher and your ET slips move in the opposite direction.

Speaking of other tools you might consider useless, have you made it to the dyno yet to verify your actual accomplishments and try to tune and optimize the package at the same time? Its money well spent as the proper dyno tune can not only produce more power but also improve the reliability of the package you just invested a ton of dough in...

-Tony

 

Hey tony,

FYI, those words aren't mine.

They are from a forum member who is an Engineer for 25 years designing shocks. He is the expert in fluid dynamics.

I simply cut and pasted from a private email I received.

So, perhaps 25 years of engineering in this exact science isn't enough...he must be wrong.

He's also a racer and builds his own engines....so, again, it's not my analysis I never claimed to be an engineer.

The fact that an F16 and a Cessna have little in common does not negate the laws of physics and aerodynamics..they fly for the same reasons, simply different renditions of the same principles of physics. In other words, I dismiss the "that's racing" argument.

Thanks

 

[B]unless you crutch the crap out of it with a huge exhaust to intake split in the cam design[/B]


i definetly agree with Tony 1000 PerCent

 

i see your 4, and raise you 3.....b..a bay, b..i bo, b i bicky bo..be....

 

 

 

Speaking of dyno numbers how close are your's Jim?

PM me if you like

Tony

 

My bad Tony......I've been meaning to start a thread outlining my build. I'll try and get that done tonight. I've been driving it for the past few days, put on about 200miles but according to my wideband and the black smoke out of my exhaust, she's running a little rich (13:1@ idle).

I have sent a chip to PCMFORLESS and datalogs to get it reflashed.

It feels like a freakin monster I can tell you that much however I'll feel better when I have some more miles on her to confirm my oil consumption issues are gone. I'm hoping to dyno it next week with the new chip.

Alvin, do your thing!!

 

I'm shocked..

You take marketing, I'll take an engineer versed in fluid dynamics....your choice.

 

Should I put names to those three?

 

Wow, between the statements I keep hearing over in the C3 section (where they are even less aware of what's going on inside an engine) and in threads like this I'm glad the engines I build go to professionals. Tony, nice post; where was the part that actually showed the difference between the engines that I build (that evidently don't operate in the real world...even though many of them have full exhaust systems without cats) and the ones that people are trying to build here? Explain and enlighten me as to how putting some more piping and a low restriction muffler on the end alters what a well tuned exhaust system is suppose to do (because most race engines have a low restriction muffler)? Then bring me to the top by showing how the flow number of the exhaust port affects the exhaust systems ability to do such. Then lets get real deep into it; show me how that has any relation with how much the intake port flows?

As I read your post (and I'm not the shock absorber guy either so don’t even come back with that) I couldn't help but ask, where are the factual points? You mentioned over cam’ing the crap out of the exhaust side since the port didn't flow enough right? Are you implying that the engine can't push the exhaust out? Because my understanding of the physics involved in PULLING every last bit of exhaust out and PULLING a little intake charge in (what we’re shoot for on every engine we design and that makes more hp than the other guys catalog hot rod) comes from the physical dimensions of the exhaust SYSTEM being optimized for the particular operating environment (note the word system)...things such as the temp, the velocity, the length of the primary tubing so on and so forth. These are things that we look at when we come up with a combination and they seem to be competitive. So let me ask one more question. If a 200 CFM port is good enough for a 270 CFM intake but not for a 300 CFM unit I take it you need something that flows more correct? How much is enough on a head that say flows 435 CFM on the intake? Your statements lead me to believe that your method is an exact science, so tell me exactly how much flow I need. I will bet that the amount of flow actually used (in my sector) is much less than anything you post (because there are two answers you can give me and both won't work) and supports a ton of hp.

Now when typing this I noticed it just doesn't sound right that the laws that govern what’s happening during engine operation just don't apply on the street and that only works in the racing world; where's the difference? What is it, which happens on my big ticket engines, that doesn’t happening in a similar, albeit smaller scale on a street unit? That's really the only argument I hear either in these posts or in other sections of the forum. I get told repeatedly that I'm in this little "world" of my own because my engines are built solely to abuse and go fast... I guess this is the reason that when I mention to other engine builders that I post on a forum they look at my funny and ask why (I always thought it had more to do with spreading knowledge that makes us money). Here I am all over this board trying to justify aspects of engine design that go into every engine that I build, while some guy that built an engine is his basement tells me I'm completely wrong. You know maybe I should just keep to building race winning engines; if you don't want to know what goes into making the class leading packages that I produce I guess you will just be that much slower than you could have been.

 

I thought that was a joke at first. If it was, it was funny. You got 'em a hook, line, and sinker.... and now the thread is trashed.

If you were being serious, welcome to the world of being a ricer. Isn't that the number one arguement for how awesome Hondas are? Hp/liter?


Good grief



Since when do cylinder heads flow fluid thru the valves? Last time I checked they flow air...which AFR's have done a good job of on a dry flow bench. Do you disagree?

How many cylinder heads has your shock absorber designer engineered? I think we all know the answer to that. Remind me how he is a qualified expert again. I personally would rather take the word of a guy who designs cylinder heads for a living and has been very sucessful doing so.


You continue to call it "marketing?" Are you saying AFR heads don't perform well? If you do try to make that statement, your last shred of credibility will be lost and you are nothing but a mouthpiece of AFR hatred. Youre acting just like the people you claim to dislike in PR&C...ignoring ALL facts b/c you simply don't like something and want to push your agenda. I really don't care if you think another product is better but to discount one that is PROVEN to perform and call it "marketing" is sheer stupidity.

Jsup, when you design your own cylinder head that out performs an AFR, then you are qualified to debate Tony on the topic. Engineer buddies who tell you something but haven't designed a set of SBC heads carry no qualifications to be experts on that topic. Period.

You guys, both AFR side and Anti-AFR side, are acting like a bunch of school girls bantering back and forth constantly over AFR vs XXX heads. Grow up already...hasn't this been played out???

Here is my take....

If built a motor and everyone thought XXX head was best and I thought I could make more power using YYY head...why would I try to get everybody on my side?? At the end of the day when my car is faster or makes more power, I'll be able to look back and say "told ya so."

Jsup, Im not even sure why youre so sensitive about this. You actually HAVE a running motor, and a strong one at that, and all of the guys who you are into arguements with DON'T(with the exception of Tony from AFR).

I really just wish every time I click on a thread in this forum I wouldn't have to read why AFR sucks or why AFR is best, and then watch the thread deteriorate into name calling and the childish behavior we've all seen for the last 6 months on this topic.

 

Yes, in physics and engineering, air is a fluid.

Dry flow bench numbers are meaningless. I refer you to this thread to learn a little something.

http://forums.corvetteforum.com/show....php?t=2158188

I will read the rest once you have the basic understanding down, let's just first agree that you're wrong about air not being a fluid then we can move on.

 

Fair enough, I am not claiming to be an expert like you. I could really care less. I could be wrong, but last time I checked all head manufacturers are usings dry flow numbers in advertising the flow of their heads. Thats called industry standard and thus is relevant.




Pussing out of answering the rest of my post? Typical. Can't stand the heat? ...deflect and run.

 

The specific area of expertise is far more complex in fluid dyanmics for a shock than a cyl head. So, yeah I'd consider him an expert. Much more so than someone who screws engines together and his hailed as an expert.

I never said such thing. I said that the facts and the marketing need to be separated...and that the knee jerk one size fits all reaction is based on myths.
I don't have to, people have already done it. Again, I am not a tech. I have to ask, why would you accept at face vale a position from somone who has a vested interest in the conversation? If Dodge came here and started telling us the Viper is far superior to the ZR-1 we'd laugh....no? I'm not saying there's anything wrong with that, I just wonder what's up with blind acceptance from a tainted source? Any source. Do you really beleieve that when Tony looks at a build he's trying to figure out how well a Brodix product will perform there? Of course not, and that's no slam, just reality. I would hope he would do that. I would also hope people would be smart enough not to lap it up, and even smarter not to repeat it as fact.

I am anit-nothing. I am simply trying to point out idiocy where I see it and blunt the mis information and mis conceptions that run rampant from people who have done far less research and have far less of an understating than I do about such matters, because I chose to learn about it.
Right, you're a smart guy, you should know that then information you are being fed is bogus and be given corrected information to make an intelligent decision. What's wrong with that. See, I don't consider magazine articles a good source, but that's just me.


Watch where the name calling comes from, it never starts with me.. I wasn't the one who mentioned any brand of anything here...I'm just pointing out the science, why is that a problem?

I think what threw everyone into a tizzy is that I had the nerve to point out that big flow numbers on the exhaust provide no benefit, and I backed it up, as Deakins solidified.

Would you prefer that the myth be perpetuated and ignorance be nurtured or that an alternitive view offered and facts laid out for YOU to decide? You tell me

 

May be relevant, but meaningless. Yes I said meaningless. If you ask Dart, they don't even post dry flow numbers. It is their contention that even with less flow they can more effectively pull air and fuel into the chamber because of the quality of the flow, it's all outlined in the link I gave you.

See, you ask me what bothers me, it's answers like this. I have taken the time to understand what dry flow numbers mean and how worthless they actually are in terms of measuring any performance. It is ONE METRIC in the countless items that determine performance. And, may I add, the least telling. Dry flow is an archaic technology which hand porters used to measure how much change they got after grinding. It has no place in the development of a head and has no reflection on the performance of a head. That is the myth.

Seems to me you bought into the position that dry flow is the be all to end all, and my hope is that I can educate people like you and once and for all dispell this myth and render it to the urban legend that it is..you're welcome.

Not pussing out at all...I just linked you to a world of information. How is that pussing out? See, this is where the attacks come from, just pointing it out.

Deakins just summarily pointed out the difference between science and marketing, and the question is, which do you want to understand? Marketing requires no thinking.

 

Did he tell you this?

Who? Tony? Deakins? Im not sure who youre talking about here.


Hang on...so you won't go on record to say that AFR heads don't perform well but then later in the post you say "information you are being fed is bogus." Which information is that?

Good one, you have waged a personal on AFR because everyone on the forum likes them, and you've set out as a non-conformist to prove they aren't the best. Why haven't you don't the same thing with Zaino and Valentine One?

When the TPIS miniram came out they advertised a gain of 95hp on a stock L98 over the TPI. What they weren't tell you is that gain was at 6500 rpm, well past what a TPI will flow. No one will say that the miniram fails to out perform a TPI. Does it give a true 95hp gain? of course not, no one revs a TPI to 6500rpm But it does consistent out perform through out. I see the AFR head advertisements in the same light. Does that mean they are not a strong performer or perform as advertised? Of course not theres just a bit of advertising sematics thrown in.

We'll agree to disagree about your engineer friends. My guess is that Tony's company has made a lot of money over the years. Probably a lot more than your friends who are engineers...if they build motors for a living and can design a better head they should be doing it, not talking a big game and falling back on pieces of paper to prove why they are right.

 

Holy crap... Youre not part of the business world are you?

 

Wanna win me over? Take an LT4 with a hot cam, Slap AFR, Darts whatever you want on the motor. Tune and Dyno....

That will win me over.