Ok heres some math for everyone to get in on, etc...
Volumetric Efficiency. for those that are new to this term, heres a small definition and background.
Quote:
Volumetric efficiency (VE) is used to describe the amount of fuel/air in the cylinder in relation to regular atmospheric air. If the cylinder is filled with fuel/air at atmospheric pressure, then the engine is said to have 100% volumetric efficiency. On the other hand, super chargers and turbo chargers increase the pressure entering the cylinder, giving the engine a volumetric efficiency greater than 100%. However, if the cylinder is pulling in a vacuum, then the engine has less than 100% volumetric efficiency. Normally aspirated engines typically run anywhere between 80% and 100% VE. So now, when you read that a certain manifold and cam combination tested out to have a 95% VE, you will know that the higher the number, the more power the engine can produce.
Basically, volumetric efficiency is effected by your carb, intake manifold, headers, and cam specs. All of these items effect how much fuel/air will flow into the cylinder. But remember, the more fuel/air that gets into the cylinder, the more power the engine will produce. This is where software programs such as Engine Analyzer, and Engine Analyzer Pro can be a big advantage. All of these programs calculate volumetric efficiency for different engine configurations that you enter into the software. This allows you to do your own testing without having to buy the parts until you get the right combination.
now with that being said, this should also be helpful in selecting throttle bodies for said engines since there is an equation Gary Howell posted a while back.
the throttle bodies available STOCK on 3rd gen vehicles are:
2200 / 2.2L 52mm
2.4L 52mm
2.3L 56mm
Ecotec 2.2L 58mm
now garys post (see following) was done for a 122cubic inch neon engine, so i'll redo the specs for a 134 cid 2.2 ohv engine.....
Quote:
49mm TB flows 252 cfm
52mm TB flows 283 cfm
55mm TB flows 317 cfm
60mm TB flows 377 cfm
At 8200 RPM a 122 cubic inch engine will need 290 cfm at 100% volumetric affiance, using the formula ((Max RPM/2)*Displacement)/1728. Rule of thumb is to go 10% over because a naturally aspirated engine can go above 100% volumetric efficiency because of cam overlap, header design, etc. Go above that and you kill low end because of reduced velocity, go below that you starve the engine for air at top end. 110% is volumetric efficiency is 319 cfm."
2.2 ohv specs
http://www.ny-jbodies.org/library/engine/2200/2200.htm
rev limit is 6000rpm
so basically the equation is ((Max RPM/2)*Displacement)/1728
which would mean (( 6000/2 ) x 134 CID) / 1728
(3000 x 134 cid) /1728
402,000 / 1728 = 232.63 or 233cfm
add the 10% ...10% of 233 is 23.3 so
the total 110% cfm would be 233 + 23 equaling 256 CFM
256 cfm is the 2.2 OHV or 2200;s 110% value of volumetric efficiency...
with the chart posted above on how much cfms certain TB flows, it would be higher than a 49mm, but lower than a 52...
however as one pointed out in the suspension forum, the same OIL FITLER the 2.4 uses, its the same thing on a CORVETTE, a much larger engine. so gm basically compensates with their parts, hence the reason for basic boltons we really dont have to do any upgrades as the computer and parts, compensate.
so theres the equations... anyone else wanna double check em or correct me if i am wrong on it, feel free to do so.... hopefully we can get some decent discussion out of this...
also so its said, when you add mods like cams, intakes, port and polishes, the value can change, but not much until the engine itself can take in more air... going larger
well i can post a link to it in the FAQ, but it seems like no one has any views????
Good info, basically says the 2.2/2200 can have all the boltons in the world and the stock 52mm TB is still plenty of airflow for the engine.
Well im getting trady to remove the 2.3 56mm TB and put the stocker back on, so maybe ill see a differance.
Mike
1992 GMC Sonoma GT #492. Oh, Its just a stock V6!
1999 Cavalier Coupe, daily driver, 2200/M5. Mods and pics are in my registry.
+
That pretty much says it all.
Support the site that supports your habit, Go Premium.
^ that's what I was thinking. The 2.3 got a really big Tb. I know it flow alot but still. Look like the guy with the Eco should buy smaller Tb other than buying the 60 or 62mm tb's
Gilles
2.3 Ho
Event only one small problem........ Even the most efficent engines in the world cannot operate above about 80% volumitric eff due to the limits placed upon it by atmospheric
presure. The only way for ANY engine to surpass this is to add forced air induction,
Turbo or Supercharger. This is why they make power by altering the amount of volumetric eff or stuffing in more air and gas.
Tho your math is enough to make my head spin it's impossible to acceave let alone surpass 100% unless a turbo or blower is added.
Sorry dude 1st year engine class stuff but its nice to see someone useing there head for something more then a hat rack.
Semper Fi SAINT. May you rest in peace.
The 2.3 Tb seem to be "perfect" even with a build 2.3.
The max displacement of a 2.3 with .040 over is 141 CI.
With the best chip available, you can rev up to 7500rpm.
So 7500 / 2 = 3750
3750 * 141 = 528750
528750 / 1728 = 305,99
305,99 + 10% = 336,49cfm
witch is pretty much what a 56mm Tb flow. I know the cam will do a big difference but I'm talking about Ho cams and .040 over pistons.
Gilles
2.3 Ho
As usual Event... Excelent and very useful info.
Thanks,
___________________________
MAKING MY DREAMS A REALITY
Visit my cardomain site !!!
ELIOT. Now.....boosted.
I'm gonna complicate things.
VE will rarely reach 100% VE on a stock engine, even with bolt ons. Maximum VE occurs at the torque peak, not at maximum rpm. Stock 2.2 VE is much closer to about 66% at torque peak (about 5200 rpm for the engine data I'm looking at now), and it decreases as rpm increases after that. Some simple estimating can check this value. Using a modified version of the formula above to estimate cfm:
(( RPM/2)*Displacement)/1728
5200 / 2 * 133 / 1728 = 200 cfm
Corrected for 66% max ve:
209 cfm * .66 = 132 cfm
Now using Chevrolet's published torque number for this 1994 engine we find peak torque listed at 130. Calculating hp from torque looks like this:
torque * 5252 / rpm = 130 * 5252 / 5200 = 131 hp.
I can't find the saved formula I had here to estimate CFM from horsepower, so I used a java calculator located at
http://www.hotrodder.com/Z28_454/math.html. Using a desired 131 hp, the calculator determines we need 127 cfm per cylinder. Recognizing that the margin of error for both CFM calculations is probably fairly high, the two figures falling within 4% of each other is not too bad.
Here's a table of VE and needed CFM values for a stock 94 engine:
RPM VE% CFM
400 54 8.31
800 55 16.93
1200 55 25.39
1600 55 33.86
2000 56 43.10
2400 59 54.49
2800 59 63.57
3200 59 72.65
3600 61 84.51
4000 63 96.97
4400 64 108.37
4800 65 120.06
5200 66 132.07
5600 62 133.61
6000 61 140.85
6400 61 150.24
I'd say the throttle body is sized quite well for this engine.
Also remember that plenum size makes a large difference in engine performance.
Engines draw air in bursts. Just like the exhaust pulses you feel at the tailpipe, the intake pulses are fairly strong. At the beginning of the intake stroke, the intake valve is only beginnign to open and piston speed is fairly slow. The throttle body can flow more than enough air to meet the demand. As the center of the intake stroke approaches, piston speed is reaching a maximum and the intake valve is fully open. Air demand is at maximum. And because it's not a 1 cylinder engine, another cylinder is also beginning to draw air through the intake. For the smallest amount of time airflow through the throttle body may not be enough to meet the demand of the cylinder. The plenum acts in part as a reservoir of air to feed the cylinder. As the piston slows down approaching TDC, the next piston in the firing order has not yet reached maximum speed. Now, air demand is low enough for the TB to recharge the plenum. The magic # for plenum volume seems to be 1.5X to 2.0X engine volume. So a 133 ci engine should have 200 to 266 ci of volume. I believe the the Hogan sheet metal intake I've seen pictured here has a large plenum.
Jackalope... with all due respect, lots of folks say 100%+ VE does happen on well tuned NA race engines. Proper headers, good cylinder scavenging, tuned length intake runners, and matched cam all work together to generate exceptional cylinder filling. Nascar power levels are a good example. An engine of 353 ci generating 700hp at 8000 rpm has a VE of about 95%.
-->Slow
Quote:
As the piston slows down approaching TDC
Should have said BDC, not TDC.
cool thats pretty much what i have
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
slowolej wrote:I'm gonna complicate things.
VE will rarely reach 100% VE on a stock engine, even with bolt ons. Maximum VE occurs at the torque peak, not at maximum rpm. Stock 2.2 VE is much closer to about 66% at torque peak (about 5200 rpm for the engine data I'm looking at now), and it decreases as rpm increases after that. Some simple estimating can check this value. Using a modified version of the formula above to estimate cfm:
(( RPM/2)*Displacement)/1728
5200 / 2 * 133 / 1728 = 200 cfm
Corrected for 66% max ve:
209 cfm * .66 = 132 cfm
Now using Chevrolet's published torque number for this 1994 engine we find peak torque listed at 130. Calculating hp from torque looks like this:
torque * 5252 / rpm = 130 * 5252 / 5200 = 131 hp.
I can't find the saved formula I had here to estimate CFM from horsepower, so I used a java calculator located at http://www.hotrodder.com/Z28_454/math.html. Using a desired 131 hp, the calculator determines we need 127 cfm per cylinder. Recognizing that the margin of error for both CFM calculations is probably fairly high, the two figures falling within 4% of each other is not too bad.
Here's a table of VE and needed CFM values for a stock 94 engine:
RPM VE% CFM
400 54 8.31
800 55 16.93
1200 55 25.39
1600 55 33.86
2000 56 43.10
2400 59 54.49
2800 59 63.57
3200 59 72.65
3600 61 84.51
4000 63 96.97
4400 64 108.37
4800 65 120.06
5200 66 132.07
5600 62 133.61
6000 61 140.85
6400 61 150.24
I'd say the throttle body is sized quite well for this engine.
Also remember that plenum size makes a large difference in engine performance.
Engines draw air in bursts. Just like the exhaust pulses you feel at the tailpipe, the intake pulses are fairly strong. At the beginning of the intake stroke, the intake valve is only beginnign to open and piston speed is fairly slow. The throttle body can flow more than enough air to meet the demand. As the center of the intake stroke approaches, piston speed is reaching a maximum and the intake valve is fully open. Air demand is at maximum. And because it's not a 1 cylinder engine, another cylinder is also beginning to draw air through the intake. For the smallest amount of time airflow through the throttle body may not be enough to meet the demand of the cylinder. The plenum acts in part as a reservoir of air to feed the cylinder. As the piston slows down approaching TDC, the next piston in the firing order has not yet reached maximum speed. Now, air demand is low enough for the TB to recharge the plenum. The magic # for plenum volume seems to be 1.5X to 2.0X engine volume. So a 133 ci engine should have 200 to 266 ci of volume. I believe the the Hogan sheet metal intake I've seen pictured here has a large plenum.
Jackalope... with all due respect, lots of folks say 100%+ VE does happen on well tuned NA race engines. Proper headers, good cylinder scavenging, tuned length intake runners, and matched cam all work together to generate exceptional cylinder filling. Nascar power levels are a good example. An engine of 353 ci generating 700hp at 8000 rpm has a VE of about 95%.
-->Slow
i likes!
so wait the older second gen 2.2;s had a max rpm/rev limit of 5200?
its starting to seem more than just moving powerbands around with TB;s, intake plenum design seems to be more the thing to look at with N/A cars.
Quote:
so wait the older second gen 2.2;s had a max rpm/rev limit of 5200?
No, no. Max rpm was way higher. But the VE (and torque) peaked at 5200. Max VE always follows the torque peak.
Intake design moved into a new era with port fuel injectors. The large plenum trick as known for years, but with carbs a large plenum ruins street performance.
Intake runner length should be adjusted if possible to move the powerband. The length of the runner affects cylinder filling by "resonance." The incoming air will "bounce" off the intake valve as it closes, then "bounce" off the higher presure air in the plenum, and just about the time it's going to "bounce" off the intake valve again, the valve opens. It's called cheap supercharging.
This formula for intake length is taken from a page that quotes a book "Tuning For Speed" by Phillip H Smith.
90/rpm (in thousands) = intake runner length in inches
So for best resonance at 5200 rpm, 90 / 5.2 = 17.3 inches. I think that's a little longer than the older 2.2 runner, but it's close.
-->Slow
Eliot, thanx brah, just tryin to help out
slowolej wrote:Quote:
so wait the older second gen 2.2;s had a max rpm/rev limit of 5200?
No, no. Max rpm was way higher. But the VE (and torque) peaked at 5200. Max VE always follows the torque peak.
Intake design moved into a new era with port fuel injectors. The large plenum trick as known for years, but with carbs a large plenum ruins street performance.
Intake runner length should be adjusted if possible to move the powerband. The length of the runner affects cylinder filling by "resonance." The incoming air will "bounce" off the intake valve as it closes, then "bounce" off the higher presure air in the plenum, and just about the time it's going to "bounce" off the intake valve again, the valve opens. It's called cheap supercharging.
This formula for intake length is taken from a page that quotes a book "Tuning For Speed" by Phillip H Smith.
90/rpm (in thousands) = intake runner length in inches
So for best resonance at 5200 rpm, 90 / 5.2 = 17.3 inches. I think that's a little longer than the older 2.2 runner, but it's close.
-->Slow
ok i gotchya....
so for the 2200;s example, 135 torque peaks at 3600 rpm...
by doing the equation you setup where 5200 was where your engines torque peaked,
it would be as follows for a 2200:
((3600 / 2)* 134 )/ 1728
(1800 * 134)/1728
139.58333333 Cfm * .66 = 92.125 corrected cfm....
tried to get to the page you linked, but i get
Quote:
HotRodder.Com
--------------------------------------------------------------------------------
Our apologies...
The page you requested cannot be found.
The document you requested is not available. It's possible that the page has been moved, you typed the address incorrectly, or that the page no longer exists.
Please check the URL, if you believe you have received this message in error, please
let our Webmaster know at info@hotrodder.com, Thank you.
but let me know if i messed up on any of that so far....
Remove the period from the end of the url. It's not supposed to be there. I just used that page to check that the VE table #'s were close to corect.
You're right on the math. But 66% is only a guess for the 98+ engine. I actually used the VE tables from a 1994 calibration, but I don't have anything for the 2200.
-->Slow
Event, I realize that this is info you were given by a local shop, BUT there infomation is wrong. No engine can see 100% vol. eff. without the use of a forced air induction system. Its imposible. Now I'm willing to believe between 85% and 95% due to how eff. engine oppereate today as opposed to even 10 years ago. But 100% would mean the cylinder is filled 100% by the intake charge and like I said without forced air this can not happen. You need to look at how an engine works internaly, now I'm not saying you don't know. You have such things as valve overlap which bleeds off cylinder presure into the exhaust and all engines have this to a degree. You also have the intake valve and exhaust valves themselves to consider, they take up space and restrict air movement by there very design. To say a throttle body is CAPABLE of supporting a certain engine to 100% of its vol. eff. is one thing but to acctualy claim the engine will run at 100% is a dream that physics will not let come true. Unless you use forced air induction of one kind or another.
Sorry Event but who eber is telling you they can get your engine to run at 100% vol. eff.
is B,Sing big time.
Semper Fi SAINT. May you rest in peace.
jackalope wrote:Event, I realize that this is info you were given by a local shop, BUT there infomation is wrong. No engine can see 100% vol. eff. without the use of a forced air induction system. Its imposible. Now I'm willing to believe between 85% and 95% due to how eff. engine oppereate today as opposed to even 10 years ago. But 100% would mean the cylinder is filled 100% by the intake charge and like I said without forced air this can not happen. You need to look at how an engine works internaly, now I'm not saying you don't know. You have such things as valve overlap which bleeds off cylinder presure into the exhaust and all engines have this to a degree. You also have the intake valve and exhaust valves themselves to consider, they take up space and restrict air movement by there very design. To say a throttle body is CAPABLE of supporting a certain engine to 100% of its vol. eff. is one thing but to acctualy claim the engine will run at 100% is a dream that physics will not let come true. Unless you use forced air induction of one kind or another.
Sorry Event but who eber is telling you they can get your engine to run at 100% vol. eff.
is B,Sing big time.
not saying it is true or not, but a few places do say its possible...
for example...
Quote:
CFM and Cylinder Heads: Usually, cylinder heads are the limiting component in the whole air flow chain. That is why installing only a large carburetor or a long cam in a stock engine does not work. When it is not possible to replace the cylinder heads because of cost, a better matching carburetor, manifold, cam and exhaust can increase HP of most stock engines by 10 to 15 points. To break 100% Volumetric Efficiency, however, better cylinder heads or OEM “HO” level engines are usually needed.
http://www.edelbrock.com/automotive/math.html
and like this site
http://www.buicks.net/shop/reference/carb_cfm.htm
where it makes the statements
Quote:
Most factory, normally aspirated engines have an efficiency of about 80%. High performance tuning can increase it to close to 100%. To go beyond this requires a pressurised induction system like supercharging or turbocharging...........Notes: Most Street engines are capable of achieving only about 80% VE (Volumetric Efficiency). A modified street engine with ported heads, headers, intake and carburetor can achieve about 85% VE. With extensive head and valve work and a new cam an engine may reach 95% or even more. It's normally not possible to achieve VE's over 100% without some form of forced induction.
and the pulse ordeal slowolej was talking about, the "cheaper supercharger method" just from the idea, seems to support the possibility of it happening.
on our engines, i def agree. its not there, but there has to be some engines that it does occur without FI. especially when it says "its normally not possible" but there has to be an exception to every rule, especially if they arent wording it as "it NEVER CAN occur"
but for me, no one has said MY engine will do 100%, my engine shop def remains realistic, hence the reason i chose them and the transmission shop
Not argueing with you dude I hope you know that. But I would love to see what engine can do this without forced air induction of some sort.
But lets just say an engine could hit 100% in an n.a. application. Ok now is this 100%
occuring at sea level with 30 inches of mercury for barometric presure? If so whats it gonna do at say 1000 feet above sea level and when the barometric presure droops
down to 22 inches of mercury? See this is the problem with trying to throw a blanket
over a statement, There are just too many veriables coming into play. Its like when a company says there intake will up your engines power out by 30 horses. Now we all
know an intake isn't gonna give us 30 hp. But the company can claim this because on one car out there it will. Its all B.S. trust me dude I've been building engines for a couple years now and dealing with all sorts of hi-performance stuff and this just ain't
happening.
Semper Fi SAINT. May you rest in peace.
Quote:
But lets just say an engine could hit 100% in an n.a. application. Ok now is this 100% occuring at sea level with 30 inches of mercury for barometric presure? If so whats it gonna do at say 1000 feet above sea level and when the barometric presure droops down to 22 inches of mercury?
This is a dang good question. VE will still be at 100% no matter what the elevation. Power levels will drop of course, but the VE won't change. Here's why.
Most descriptions of VE are oversimplified. They say something like "The ratio of actual CFM of air moved to theoretical air moved" or "the actual amount of air in the cylinder compared to the cylinder volume." The reality is, the cylinder is filled 100% with air on each intake stroke. Think about it: Does the engine displacement change? No. Does air somehow sit at the bottom, or top, or side of the cylinder? No. Air expands to fill the entire cylinder, and the piston travels through it's entire range, so it has to be 100% filled on each intake stroke.
What the VE descriptions should say is something like "VE is the ratio of air density within the cylinder compared to air density outside the engine." Because it's the density of the cylinder charge which is important, not the volume. When you think about this, 100% VE means the air in the cylinder is just as "thick" as the air around the engine. And with this in mind, it doesn't matter what elevation you're at, the VE doesn't change.
-->Slow
V.E. will change according to ellavation. just ask anyone who drag races accross the country. At sae level your faster then in the rockies because with a gain in altitude comes a drop in baro presure. Phsics can not be changed. At sea level air "weighs"
more then it does in say the rockies because there is less air pushing down on it. Less air presure means a drop in performance due to less air being pushed into the cylinders by atmospheric presure. Why do you think you see such things as horse power corrected in relation to altitude? Or quarter mile speeds for that matter.
I don't know if you guys are useing the correct terminology for what your talking about so
I'll just make sure were all on the same page here.
Volumetric effeciecy is the measure of how full a cylinder is on its intake stroke at bottom dead center at the closeing of the intake valve. Now V.E. is directly effected by
barometric presure when the baromiter is low like before a storm then there is less air entering the engine meaning less V.E. is being acheived. Altitude will also have an effect on V.E. being there is less presure the higher up you go. Now keeping this in mind I hope you can see where it is impossible to acceave 100% unless its a forced
air application
Any other questions youd like answered just feel free to ask.
Semper Fi SAINT. May you rest in peace.
jackalope wrote:Not argueing with you dude I hope you know that. But I would love to see what engine can do this without forced air induction of some sort.
But lets just say an engine could hit 100% in an n.a. application. Ok now is this 100%
occuring at sea level with 30 inches of mercury for barometric presure? If so whats it gonna do at say 1000 feet above sea level and when the barometric presure droops
down to 22 inches of mercury? See this is the problem with trying to throw a blanket
over a statement, There are just too many veriables coming into play. Its like when a company says there intake will up your engines power out by 30 horses. Now we all
know an intake isn't gonna give us 30 hp. But the company can claim this because on one car out there it will. Its all B.S. trust me dude I've been building engines for a couple years now and dealing with all sorts of hi-performance stuff and this just ain't
happening.
c'mon know... granted i;ve known you for only a few weeks, you know i;m not the type to
"get mad, take my ball and go home cause things dont go my way"
i consider this nothing more than discussion and learning while some others would call it "arguing/fighting"
will get back to ya... only on break from the part time...
I know you don't seem the type but I just like to make sure thats all.
Semper Fi SAINT. May you rest in peace.
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.
Don't steal, the government doesn't like competition
Ok now I see where you guys are going a little off with this. Your talking about the engines demands in relation to C.F.M. Completely different then volumetric eff. The formula is used to help determ how much flow a throttle body needs to have in order to accoidate the enigne at full throttle. Completely different then V.E. Carry on
Semper Fi SAINT. May you rest in peace.
