spin1r6 wrote:well the math seems logical and all, but i dont think it would relate to tb size as the post would make you believe. my interpretation is that the cylinders need 256 cfm, and while a 50mm tb can flow that cfm, it is close to max flow thru that tb. meaning that a 50mm tb wont flow any more than 260 cfm or so without boost. if you put a 60mm on, it could get that 256 cfm to the cylinders withg less effort, which would make more power. up to a point where too big would lose velocity. it seems you would want a happy medium rather than the bare minimum.
with 60mm, you already lost velocity.... the 52 would be able to flow the 256 + a surplus and then since the plenum of the intake manifold is so large, you already have a reserve area....
59;s bad enough, virtually no velocity and no punch off the line.... sure you may get peak numbers in hp gain, but if you;ve lost the race off the line, its hardly feasible you will make it up in the end being N/A without some other power adder.
i dont care, the 59 matches the 60 mm opening on my s/c very nicely
-----------------------------------------------------------------------
-----------------------------------------------------------------------
- Sold my beloved J in April 2010 -
The math that describes VE accounts for changes in atmospheric pressure. If a change in altitude changed VE, then an engine with 0% VE at sea level would have negative VE at 5000 ft above.
If greater than 100% VE is not possible in NA engines, some type of magic must be helping F1 and IRL 3.0L NA engines to produce excess of 700hp. That's 233hp per liter, NA.
Lots and lots of good reading in the NACA papers. For a definite answer on VE and altitude, check the 3rd page of text in this paper:
THE TESTING OF AVIATION ENGINES UNDER APPROXIMATE ALTITUDE CONDITIONS.
-->Slow
Slowolej F1 engine run a ton of compression and spin the engines to around 20,000
rpm THATS how they can get the horsepower numbers they do. V.E. is the measure of how full the cylinder can be made on an intake stroke. Now unless you force air into
the cylinder how can it be filled to more then 100%? It can't.
Nascar engines also produce between 600 and 700 hp out of a 355 cubic inch engine
No forced induction there. And they run about 95% V.E. so how do they make that kind of power? Magic? no its again called R.P.M. and compression.
Look at an engine in a top fuel dragster they produce 1000hp from 500cubic inches
but when you see how its done its amazing. The big ass blowers you see on then
actualy take over 600hp to even spin! But there boosting the air and fuel into the cylinders at just below hydrostactic lock. The 2 spark plug per cylinder magnetoes
create more spark energy then a plasma cutter does on its highest settings. And if you've ever seen them run at night you've seen the blueish white flames coming from the exhaust well thats not fire it the air being turned into superheated plasma.
The ONLY way to exceed 100% V.E. is thru forced induction. Even the F1 engines you sight are prob running around 98% - 99% V.E. You can not change physics.
Semper Fi SAINT. May you rest in peace.
Quote:
You can not change physics
Physics is math. I've tried to show you how the math and the physics are set up but you're not interested in hearing it. It's frustrating.
If a 5.7l engine produces 700 hp at 95% VE, and a 3 liter engine produces 700 hp with almost half the V, E has to increase more than 4%! If a 4% increase in VE equated to a 90% increase in power per liter, we'd all have 300 hp engines with just bolt ons. You are not looking at _all_ of the physics. You are not considering the relationship between the different individual things you know.
-->Slow
Frustrating is right. You are not understanding what I'm talking about and you insist on argueing. V.E. is how full you can get a cylinder of an engine. Think of it like a glass on a table, If its filled all the way to the top with air that is 100% V.E. Now how do you propose to fill a cylinder beyond its 100% capisity without forced induction? You can't
its just IMPOSSIBLE. Now throw in a couple valves, blow by, intake runner design, restrictive exhause systems and this is how you winde up with a V.E. in the 80's and
90's. V.E. does not directly equate to horse power either. Unfortunatly I'm at work so
I'll try to explain it to you when I get home.
Semper Fi SAINT. May you rest in peace.
I'm going to have to chime in and agree with slowolej. Atmospheric pressure or altitude does not alter VE in any way. VE is the efficiency of the combustion chamber being filled with whatever gas, pressure or density, is surrounding it.
Here's a good engine science link.
http://www.auto-ware.com/combust_bytes/eng_sci.htm
Further more, it may not be practical, or simple, but it is possible in theory to achieve greater the 100% VE in a N/A motor. How you ask, well think of it this way, there is weight to air just like water or any other mass, once you get a mass moving it has inertia. So if you keep the air moving through the motor with a good amount of velocity, then whoops the exhaust valve closes, all the air traveling behind it will keep moving until something stops it. Its like pile up on the on the freeway, all the air moving through the intake side piles up in the chamber, and if you close the intake valve before the air equilibrates back to atmospheric pressure, you've effectively squished a little extra air into the chamber. This would require very exact pulse timing. And I'm not saying that you should go try this either, I'm just say that in theory its possible. Also then getting the exhaust back out of the motor with no overlap is gonna be another problem, so it might only be possible on every eighth stroke of the piston, 1 combustion cycle with no over lap for using the inertia in the intake to squeeze in more than 100%, the next combustion cycle would need a little over lap to get the exhaust gas moving and to get the intake inertia moving again.
Whoops, I've just gone cross-eyed thinking about that cam design.
So if I did my math right, the throttle body on the 2.4L is just a tad too small. as in 1 or 2 MM. Interesting.
I'll make this as easy as I can for you guys. Sit a empty glass out on the counter, How
full is it of air? Its 100% full, correct? Now how can you "overfill" it with air unless you presureize the air? You cannot. I'm not gonna stand here and argue theretical physics with you guys when you simply CAN NOT grasp the concept. Dis - agree all you want to till your blue in the face if you like but you can not acheave greater fill then
100% unless you force in the air PERIOD end of discussion it is impossible. Now
please do yourselves a favor and go read up on this before you try and argue it with someone who knows what hes talking about.
And as for altitude changeing V.E. and subsequently engine output then why is it when you drag race in the rockies you get a time that is "corrected" for altitude? Or why it is that they need to ricen up the fuel mixture on the cars?
Guys please I'm not here to fight or name call but this stuff is evidently out of your league and you have NO IDEA what your talking about.
Just tell me how YOU think you can get more then 100% of the glasses air volume into it without compressing it?
Semper Fi SAINT. May you rest in peace.
Did you read my post? I'm not trying to argue, this is a public forum for DISCUSSION.
And I agree with you there, the air must be compressed to achieve anything over 100% VE, but you don't necessarily need a SC or TC to do that. In my example, ^^, its the inertia of the air moving through the intake towards chamber when the exhaust valve closes that could cause some small amount compression. Please re-read carefully.
100% volume of thin, high altitude air, or 100% of dense, sea level air, is still 100% volume.
I'm not going into why there's adjusted times when drag racing at high altitude or richened mixtures, as I'm sure everyone understands that concept.
Nobody is name calling, but I do think your a bit closed minded on this matter, and unwilling to even attempt to see the other side of the discussion.
^ He's right as far as being able to squeeze more then 100% air into a glass, In a chem, class we had a smoke machine and a fan and a capsule. There was a valve that was powered by a solenoid and when left open you got 100% no more no less obviously. Now when the fan was kicked on and allowed to flow in one end of the capsule and out the other it gained inertia then when the bottom was closed it contiued rushing in and when it was full the valve was instantly shut leaving 101 and some change left in the capsule. Now as far as an engine with valves, heat , oil and tons of varialbes I do not know but as far as filling something with more then 100% with out fi and just inertia it is possible.
Now after I read this whole post and my head hurts I have one question I have been trying to get answered and have had nothing but yes here no there maybe you guys can help me out.
I have an eco, looked into the larger TB but realized that it will hurt me in the low end (understood), I have N20 and spray a 75 shot. If I upgrade to say a 60 mm tb am I going to make up in the high endfor what i lost in the low end with in a 1/4 mile?
I'm really trying to figure it out b4 I go and spend the cash to answer my question any help would be great thank you.
oh yeah and as far as the altitude goes you loose the numbers and power simply because the air isn't as dense and it takes more time to fill a chamber 100% which is why the times are slower,
Not because of the pressure, I know that the pressure will make increase the density but bottom line it is density, ahh never mind I confused myself but maybe someone knows what I'm getting at prolly wrong but o well.
Ben, I'm not being closed minded at all I've asked how to fill a glass beyond its 100%.
Thats all, Now as for your exparament ( I was hopeing for this actualy, thank you ) Yes
in a labratory with controles it may be possible to actualy get over 100% with your fan
test you did. BUT on an engine you have several factors working against you on getting to 100% without the aid of forced induction. First you have your throttle body or carburator, by its very design it limits the amount of air entering the engine. Second
you have the runner design of the intake manifold and any over lapping areas that may interfer with the airs unrestricted folw. Then you have the intake valve that the air slams into comes to a dead stop and has to wait till the valve re-opens so it can start to enter the cylinder. And finaily you have blow-by where air passes between the spilt area of the rings and enters the crankcase. Once you throw in all of these vairibles you still have the exhaust and how rapidly it allows the burned exhaust to leave the cylinder. And if thats still not enough, well don't forget the good old E.G.R. system which is designed to recirculate burned exhaust gases back into the fresh air stream takeing up space so that the engine can not reach its full potential. Now why on Earth would car companies do such a thing as deliberatly take up valuable room in the cylinder with gases that can not burn and there for reduce the V.E. ? Its to lower the combustion chamber temperatures and there by reduce emisions. This is why I was saying that a street engine WILL NEVER EVER see 100% unless you use some kind of forced induction.
( DEEP BREATE !!! )
Now as for altitude effecting V.E. it does. True not a whole hell of a lot but it does. Let
me explain The higher up you go the lower the barometric presure drops just as
Fatalic pointed out. Now an engine is nothing more then a pump theat relies on vaccum
to keep it running with out vaccum you cant have compression no compression no way to move the piston up and down in its cylinder. Now how much vaccum an engine can produce is directly related to the amout of barometric presure pushing down on the enigine from all around. The less presure the less vaccum. With me so far? Good.
Now if an engines piston moves down in the cylinder and the intake valve is open then its fairly safe to assume that atmospheric presure is going to push / force air into the cylider up to the point of how much presure is all around the engine. Ok now say an engine is running at sea level there is a barometric presure of around 30 inches of mercury ( this is how barometric presure is measure in inches of mercury that are pushed up in a glass tube by the air presure being placed on it ) Ok the engine is running air is being pushed in by the presure around it and its opeating at about 90%
V.E. at 30 inches of merc. Now the air is fairly dence and the engine runs good.
Raise it up to the Denver area and now the presure has dropped to about 25 inches of merc. So theres less air presure pushing down on the engine less presure means less vaccum, less vaccum means that less air can be pulled into a cylinder meaning the engines V.E. has effectively been dropped. True not by much but it has been this is why the only people who even realize it are Drag racers because they have times from when the car was at sea level where the air is dencer.
( DEEP BREATH !!!! )
I hope this has helped explain why I was saying what I was. I also hope noone takes any of this as me being a smart ass as this was not my intent. I like to know when I make a mistake so I can fix it and I'm hoping I'm not the only one that fells this way.
If you guys have anymore questions at all please feel free to ask.
Semper Fi SAINT. May you rest in peace.
Fatalic CAVI wrote:i have a question 
Quote:
Now after I read this whole post and my head hurts I have one question I have been trying to get answered and have had nothing but yes here no there maybe you guys can help me out.
Quote:
I have an eco, looked into the larger TB but realized that it will hurt me in the low end (understood), I have N20 and spray a 75 shot. If I upgrade to say a 60 mm tb am I going to make up in the high endfor what i lost in the low end with in a 1/4 mile?
to be honest, only one way to tell, and its usually the name of friday night track racing....
"TEST AND TUNE"
alot of that will depend on when you spray, how you launch, etc.... so many variables...
Yea thats what I thought I just figured someone may know already if it worked for them or if there is one more of those mathmatical calculations in that book of yours that can tell me the answer lol. I just feel that shelling out that kind of cash for little to no gain in the 1/4 is going to be worth it.
i know what your saying muffins. i didnt literally mean 60 mm was ideal. i was just saying that it would seem that the ideal size would be somewhere between 49 and 62. i dont know what it would be, but i dont think the minimum would be ideal.
Don't steal, the government doesn't like competition
let me see if i might be able to understand whats going on.
VE shouldnt be affected at altitude because 100% air at sea level is going to be different than 100% in the mountains. 100% = 100% but because of the density of air 100% at sea will be more than at altitude. even though VE is the same in reality there is less air in the box. so it takes less air in the same space. and because less air means less hp.
reading threw this it seems that the space the whole intake (runners and plenum) need to be equated somehow because the tb has to flow enough air to fill the cylinder runner and plenum. just because the TB flows enough to fill the cyl doesnt mean it will flow enough to fill the whole 100% airspace at a given time. but if we get this far into it then since only 1 cyl is open at a time (to a point) then wouldnt the calculations need to be the best way to fill up the actual 100% of the cyl open, runners, and plenum? i might be wrong but who knows.
and i actually did get a headache from readin this post.
/\ /\ /\ /\ Thats right. Thank God someone gets it !! The things you named to play into the V.E. and how the air actualy flows into the cylinder. Thats why an engine can not acheive 100% V.E. unless the engine is boosted.
And yes this can give you a head ache sorry. But now do you see why 100% is impossible. There are just too many things to keep this from happening.
Semper Fi SAINT. May you rest in peace.
jackalope wrote:/\ /\ /\ /\ Thats right. Thank God someone gets it !! The things you named to play into the V.E. and how the air actualy flows into the cylinder. Thats why an engine can not acheive 100% V.E. unless the engine is boosted.
And yes this can give you a head ache sorry. But now do you see why 100% is impossible. There are just too many things to keep this from happening.
so explain why N/A race engines achieve it in indy and F-1.... just askin...
Dam-it Muffins (Event) wrote:jackalope wrote:/\ /\ /\ /\ Thats right. Thank God someone gets it !! The things you named to play into the V.E. and how the air actualy flows into the cylinder. Thats why an engine can not acheive 100% V.E. unless the engine is boosted.
And yes this can give you a head ache sorry. But now do you see why 100% is impossible. There are just too many things to keep this from happening.
so explain why N/A race engines achieve it in Indy and F-1.... just asking...
just a shot in the dark as seeing i'm not an Indy or f1 expert or engineer.
it they in fact make 100% VE maybe it is because it took a team of engineers lots of time, testing and money to develop the engine. and because they have the budget and time they can calculate down to very accurate levels of exactly how the engine works and the best way to fill it with air, and get it out. they have the time and resources to make the most efficient engine possibly.
further making me believe that the set of equations they use incorporate everything in the intake not just cyl. because i might be wrong but wouldn't the equation be skewed because of the variables included with runners, plenum, and the actual intake pipes (pre tb) ability to flow. and then also they have to be filled with air also etc.
i have no education at automotive engineering but i do know enough that if the equation is wrong so will the solution. and also can everyone at least keep an open mind to ideas?
Fatalic Cavi, my take on the TB is this. Switching to a too large TB without switching to numerically lower gears makes a car feel slower on the street. It's not as much fun imo. You use nitrous because you can't get the airflow you want to make the power you want, and the TB alone isn't going to give enough power to allow you to quit using the N20. If you need more power look into a bigger nitrous shot. Personally, I'd save the $$ from the TB until I had an engine that needed it. Throw the cash into the next nitrous refill. Heck, throw the cash into the next fuel refill. It's probably about the same price by now.
Jackalope, here's the deal.
You're not giving me enough credit for what I do get. Everything you're talking about... less hp with elevation or atmospheric pressure, less fuel needed at elevation, less air density, I get. I've been racing at Douglass, WY, Great Falls, MT, and at Lebanon Valley and Epping. I've lived at close to sea level and 3500 ft above. I've seen it. I know damn well that you're right about what you see. But you're just as wrong wrong about what you call it.
VE is an engineering and physics term. It's set up as math. VE math is designed so VE doesn't change with atmospheric pressure changes. What you're calling VE isn't what engineers call VE. And since it was engineers, not Jackalopes, that made up VE, they get to set it up however they want. You've got the wrong name for the thing you're describing.
You said:
Quote:
Now if an engines piston moves down in the cylinder and the intake valve is open then its fairly safe to assume that atmospheric presure is going to push / force air into the cylider up to the point of how much presure is all around the engine.
That's it. Stop right there. That's all there is to VE. VE does not compare sea level air density to high altitude air density. You went on to say
Quote:
So theres less air presure pushing down on the engine less presure means less vaccum, less vaccum means that less air can be pulled into a cylinder meaning the engines V.E. has effectively been dropped.
Wrong name. That's not VE. The engine's VE isn't decided at sea level. The engine's VE is decided at whatever altitude it's at. Yes, there's less air in the cylinder. But there's less air outside the cylinder, and VE compares air in the cylinder to air outside the cylinder at whatever altitude the cylinder is at. It may seem like splitting hairs to you. people will think I'm beating a dead horse. I only wish someone had been able to point out some of the finer points to me when I was first starting out.
I can answer a question you've asked very easily.
Quote:
Sit a empty glass out on the counter, How full is it of air? Its 100% full, correct? Now how can you "overfill" it with air unless you presureize the air? You cannot.
This is easier than you think.
You pick up the table with the glass and lift it as fast as you can. For the smallest amount of time when the glass is accelerating, air will be compressed in the glass. The glass will be "overfull." And it's done without pressurizing the air in the room.
The difference is that the glass is moving, just like air entering a cylinder is moving. Air is like a spring. A spring sitting still isn't very exciting. It just sits. To make anything interesting happen with a spring, you need some type of movement. Stretch, compress, wind, bounce... some type of motion needs to be involved. Air is the same. Still air is boring air. Moving air has a lot more potential.
Quote:
You are not understanding what I'm talking about and you insist on argueing.
The hardest part of this is separating "what you've seen" from "what it's called."
I've gotta go do some tuning... and some relaxing.
-->Slow
Event, F1 cars come the closest to100% but they do not acheive it. How do they do this? Well if you had unlimited money to throw at an engine along with the best engineers in the world and areo-space materials then you could do it as well. But alass our lowly little 4 cylinder engines are not very high up on the food chain when it comes to the manufacturers throwing money at them. They were built to be cheep
transportation NOT race cars.
Slowloej, So good I'm glad we agree on what V.E. is now that I see you do know a little about what your talking about I don't feel like I'm talking to a brick anymore. And since
you understand what V.E. actualy is then you can also see why its just not possible to
go be able to accheive 100% let alone exceed it without the use of forced induction.
Glad we can all agree on this and a special thank you goes out to Event for starting this wonderfuly informative thread.
Event I hope you too can see now why acheiveing 100% just can not be done unless you force the air in somehow. I never said we shouldn't let this stop us from trying to make our engines better but since none of us has the budget of an F1 team please don't think your ever gonna see 100% unless you turbo or supercharge it.
Semper Fi SAINT. May you rest in peace.
