I am building a 406 and have recently decided to go with aluminum heads. Will probably be just below 10:1 compression, turbo 350, and I haven't picked any actual components yet. I want to be atleast at 12 flat in the quarter but this will be mostly a street car. I love throttle response, and don't like vacuum secondaries. Any suggestions on getting the throttle response I'm looking for? (no slicks with blower haha) How much more crisp is the vac over the mech carb? Any suggestions on gears carb? In doing a search I learned that the holley DP's have great throttle response. Is there anything else that I haven't mentioned that plays a big role? Is there anything that I would be giving up in order to achieve this? If so please explain.
Thanks in advance,
Darren

The keys to throttle response would be a well thought out, proper "combo" for your intended usage, and good tuning. I agree with your choice of a dp carb. Long ago, I ran a 650 dp on a 400, with a very mild street combo, response and low end torque were out of this world. Tuning the engine to stay out of ping and run right on the edge took an entire summer.

Some things not to do: 220cc ports and 300 degree cam with 3.08 gears will typically leave a bit to be desired.

Some things to do: tune tune tune. Be prepared to spend a LOT of time changing jets, power valves, timing curves, etc. Do some reading and learning. Whnile there is an "order" to this stuff, there is also a lot of interaction.

An engine with good street manners and response will be tuned right on the edge, as lean as you can reliably get it, as much compression and advance as the fuel will stand. It will take much time and patience to get the jetting, pump, pv, and vacuam and mech curves just right.

That's a really good question actually :thumbsup:

I think there are a few factors that affect throttle response. There are things that effect velocity in the induction and exhaust systems, then there are things that effect the quality of the air/fuel mixture and speed of the burn.

On the induction and exhaust side of the equation, cylinder head intake ports that are properly sized help keep velocity high. Same on the exhaust -- headers with the proper sized primary tubes (both diameter AND length) and a collector with the correct dimensions will help keep velocity high. There is a point though where velocity gets "too high" (or actually stops getting higher at all and is just maxed) and power production will fall flat at higher RPMs.

Camshaft timing is probably the single most important factor in throttle response. Besides needing to be matched to your compression ratio, longer duration cams will tend to cause reversion at low RPMs. When reversion occurs, burned gasses from the cylinder actually push their way back into the intake during the overlap phase. When this happens your intake charge gets diluted and goes lean -- this makes for a rough idle and sluggish response.

Intake manifold design plays a key role as well -- a single plane manifold will perform better on the top end and a dual plane will tend to perform better on the low end. A dual plane manifold tends to have longer (and usually smaller diameter) runners that tend to keep velocity high at lower RPM.

Now the advantage of having high velocity intake and exhaust flow is that tiny fuel droplets will tend to stay in suspension and make it into the cylinder to fully burn. In addition air flow has more turbulence and swirl, helping to keep a good even mixture inside the cylinder.

Now good velocity and burn quality are related, but there are other factors that affect the quality of the burn too. A proper ignition advance curve will help a lot. A strong spark will help throttle response too since a strong spark is needed to consistently fire lean mixtures at cruise and idle. I'd set up yuour distributor for a curve that has 34* total timing all in by 2800-3000 RPM.

Now that I'm done rambling (sorry about that) I'd look for heads with 190-200cc runners, a cam with mid-220's duration @ .050, a conservatively sized double pumper carb (like a 650), a Performer RPM manifold (non-air gap), and a set of 1-5/8" tube headers. This will make a power band of just off-idle to 5700-5800 RPM with great throttle response. Some carb tweeking may be needed to get that "fuel injection" type response but you won't have any problem.

PS. freeway gears and tight TQ converters tend to make an engine feel sluggish - a looser converter and a performance gear ratio will let the engine rev faster with less low-rpm load.

Buy a DP carb with annular boosters and you will have all the throttle response you want. These annular booster carbs are very responsive. Yeah it really is that simple. I didn't believe it until I tried it myself. Of course the rest of the combo has to be close and tuned decent. There really is a difference.

If you want the ultimate throttle response, think about installing an EFI unit.

JimM Did you ever run that mild combo with the 650 in the quarter? If not what is your estimate? And what heads and cc runner did you have?

Eric When it comes time to buy exhaust and cam I will be here asking advise again. Good point on gear and converter. I have a couple intake manifolds so it will be fun to experiment with both. How much do you think I will be hurting my quarter time by focusing on throttle response?

Camaroman I will probably be getting a DP with annulars, just not sold on whether to get the 650 or 750 yet. Oh and I don't know what annulars are haha

GMRanch I asked my wife if she wanted to trade the efi off her trail blazer for a nice carb set up, but I guess she's learned enough about cars not to fall for it.

Thank You all for your time,
Darren

Well its all about compromises, if you keep the combo optimized it should have good throttle response regardless of whether its a mild street combo or a little more radical.

Speaking of intake port sizes... I came across a post on another site which seemed pretty interesting... about how port size isn't important really, but rather port cross section is.

Where the post says "EXAMPLE" the guy had uploaded some dyno graph pics.

Anyway... here is the post.



"there seems to be a HUGE mis-understanding about port size and how it potentially effects your engines torque range,
port size should be thought of more as a restriction to reaching necessary flow than a benefit to making a significant torque curve PROVIDED your matching the total engine component list to the intended rpm range and expected hp peaks the engine will be expected to produce and run at!
its not port size but the ports cross sectional area and length matched to the other components like the engines displacement,compression, cam timing and bore/stroke ratio PLUS the exhaust systems designed scavage effiecincy range at any give RPM level has a major effect on results, the size of the ports in your cylinder heads are one of the least> THATS RIGHT I SAID THE LEAST important of the factors that determine where in the rpm range your engine builds its best power, while its true that smaller port cross sectional areas due cause the airflow speeds to increase,its also very true that the runner length and cross sectional area of the intake used, the compression ratio and the cam timing and the design of the header primary tubes are at least two to three times as important simply because they control the airflow thru the cylinder to a much greater extent, and the engines stroke and total displacement are extremely important, changing JUST the displacement and cam timeing has a HUGE EFFECT on WHEN and HOW the airflow in the ports gets its vacuum signal and how the port responds to that change in pressure.
you can build a torque monster engine with large ports in the cylinder heads, quiet easily if the other factors are carefully matched

notice that the 180cc AFR heads which are known for torque production have basically the SAME cross sectional area as the TRICKFLOW 195 cc heads and that the differance between the AFR 180cc haeds and the 210cc heads is only approximatly a 6% increase in size so the true air flow thru a 210cc head will be only approximately 6% slower on the same engine.........swap to a 383 from a 350 which is approximately 8% larger and you quickly see where the smaller heads can become more of a restriction than a benefit to the combo!

know I know from experiance building engines for years that a rought guide to matching hp to the intended engine port flow requirements can be guessed at fairly closely useing these formulas below, play with them then measure the port cross sectional area in your engine at its narrow point, and don,t forget the cam lift your restricted too and the valves curtain areas in the combustion chambers

"Fortunately for our purposes, these complex calculations can be broken down into a very simple formula that is useful for us as speed crafters.
Intake Runner Area = Cylinder Volume X Peak Torque RPM 88200
This formula takes into account the best theoretical speed that air can move down the runners, to give the best volumetric efficiency. Peak Torque occurs in an engine at the RPM where the engine is enjoying its highest volumetric efficiency. "





below youll find some things to read/play with

http://www.n2performance.com/lectures/airflow.pdf

http://www.rbracing-rsr.com/runnertorquecalc.html

heres a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some comon cross sectional port sizes
(measured at the smallest part of the ports)
...........................sq inches........port cc
edelbrock performer rpm ....1.43.............170
vortec......................1.66.............170
tfs195......................1.93.............195
afr 180.....................1.93.............180
afr 195.....................1.98.............195
afr 210.....................2.05.............210
dart pro 200................2.06.............200
dart pro 215................2.14.............215
brodix track 1 .............2.30.............221
dart pro 1 230..............2.40.............230
edelbrock 23 high port .....2.53.............238
edelbrock 18 deg............2.71.............266
tfs 18 deg..................2.80.............250

Potential HP based on Airflow (Hot Rod, Jun '99, p74):
Airflow at 28" of water x 0.257 x number of cylinders = potential HP
or required airflow based on HP:
HP / 0.257 / cylinders = required airflow
NO!ITS NOT FOOLPROOF! BUT ITS A VERY GOOD TOOL!
what tends to make me crazy is guys that insist on running vortec or similar small port heads and a dual plane intake for max low rpm torque, when I or someone elsae builds thier engine,who then come back and want thier 383-421 sbc to run the big hp/tq numbers and pull hard at 6000rpm and above where those small ports are far past there effective air flow limits
Ive built some KILLER engines useing the 215cc and 230cc IRON EAGLE heads and SIMILAR larger port heads that made great torque in the low and mid ranges, a dual plane intake,with long runners and a 600cfm-750cfm carb helps, as does a cam thats designed for the midrange torque, and full length headers , with 1 5/8" primairies,its NOT the port size in the cylinder heads ALONE that determines the results! its the COMPLETE MATCHED COMBO and the thought that was put into makeing the components match the intended power curve, and matching the cars rear gear and stall speed to that power curve, sure you might be running slightly higher average rpms, to get the best power ,but youll be making a whole lot more power at the rear wheels too!
if you want to get good mileage and decent torque and limit yourself to 1500rpm-3500rpm the small port vortec type heads work great on a 350,thats what G.M. spent the money researching the design to do! ,they are after all TRUCK HEADS!
but increase the displacement to 383 or more and spin the engine to 6500rpm and they become a huge restriction!
while a larger head can give up very little if anything down low in the rpm range but pull far bigger numbers on the hp/tq up higher in the rpm range simply because its still able to flow the necessary voluum of air the engine needs, G.M. knows that! but they also know that 90% plus of the time EMISSIONS and GAS MILEAGE and smooth just off idle low rpm torque is where most engines are used, so they build to fit MOST users expectations

http://www.rbracing-rsr.com/runnertorquecalc.html


play with the calculator,, notice the vortec heads 1.66 are would peak the torque at about 3100rpm on a 383, while a dart 215 cc with its 2.14 port only moves it up to about 3950 rpm AND THATS ASSUMING the larger port head has a matching larger intake runner the whole way to the carb venturies, if you stuck the same intake and other mathing components on BOTH cylinder heads the differance in rpm ranges would be more likely to be in the 300rpm range

EXAMPLE

http://cgi.ebay.com/ebaymotors/ws/e...7965364790&rd=1

BTW notice the 215cc heads and the strong torque curve????? its fairly obvious from the dyno chart this combo is UNDER CAMMED to make good low rpm tq at the sacrifice of potential top rpm power,

power/tq starts to fall off at about 3700rpm,while thats a good idea in a street engine, you could pick up some mid and top rpm power by swapping to a slightly wilder durration cam [b]PROVIDED THE REST OF YOUR COMBO, like the trans stall speed and rear gear allow it
just some info
a 10.3:1 cpr 383 with 215cc alunminum heads [b] if its matched to a 3000rpm stall converter and 3.73-4.56 rear gears makes a really nice power curve with a cam similar to the CRANE 114681 or lunati voodoo 60104 or for that matter most cams with a 235-245 intake duration and about a .510 or greater lift on a 110-112 LSA
swapping to a cam like that would boost power significantly (40-50hp)_but also make it less street driver friendly in that it would require the drivetrain changes above ans sound like a race engine at idle and would be unlikely to pass emmission testing

"Is there any problems with an “under cammed “ engine? "


no! not if low and mid range torque and NOT peak horsepower is the goal.....but Id like to point out again that the 215cc ports size makes very good low an mid range rpm torque if the compression and cam used are designed for very good low an mid range rpm torque, the comon crap you always hear about port size being very critical to low rpm torque is just that ( mostly CRAP), its just not as important as displacement, compression or cam timing to the results and small cross section ports restrict high rpm power far more than large ports hurt low rpm torque IF THE OTHER COMPONENTS in the combo are DESIGNED to produce mid range tq/power

EXAMPLE


heres a 427 sbc with 227cc port heads, that does not seem to be losing a great deal of low rpm torque do to its large ports"

However much debated, look at NHRA stock eliminator. Particularly look at the 305 combo in the 80's camaros H/SA and G/SA going 10.90's with ports that are roughly 160cc's and MUST remain untouched. No doubt these heads are touched, but the fact remains they're a small port!
Small ports are not the restriction that everyone makes them out to be.

If your goal is 12.00 with a 406, you dont need a Huge head to go 12.00

Take a look at my engine, what i do to SLOW IT DOWN TO 12.00 is Unhook the secondaries, and shift at 5800rpms. that makes it a 375cfm carb, hehe.

that makes it a 375cfm carb, hehe.

If you disconnect the secondaries and make a 2-bbl out of it , it's the same as a 500 cfm 4412. That's still hauling ***, though.

We're going the other way - putting a 750 on in place of a 500 2-bbl. It'll be interesting to see the dyno results. I did a circle track car last year that gained 30 rwhp swapping from a 4412 to a 4779.

[QUOTE=67CamaroD]JimM Did you ever run that mild combo with the 650 in the quarter? If not what is your estimate? And what heads and cc runner did you have?

Yes, I did, lotsa times. Car was a 67, with a t350, shift kit, stock converter, both 4.11 and 3.73 open rears, and L60-15 street tires. Car ran consistent 13.20's @ 108, and was VERY Traction limited. I'm talking pure smoke in first, loose again in second, and shifting into 3rd at the fiirst mph light @ 5800 rpm.

Later, I put the same engine in a 4 speed 69 vette, my favoite trick was to put my right foot on the dash, the shifter in third, and slide my foot off the clutch and putt up that 8% grade in front of my house... at 400 rpm in third gear!

Combo was: 400 sbc w/ flat top forged pistons, 64cc -186 heads (1.94 intake) Torker one, 650dp, crane blazer cam ~210 @ .050, .450 lift.

Car was very streetable, very quick, and a pure torque monster.

Down sides were too much compression (took a long time to get tuned right) and a propensity to eat starters, and break pinion gears right off the shaft (3, the last 2 were with a 12 bolt)

If I were to do another...

I'd use d-dish pistons, 64cc vortec style aftermarket alluminum heads with 190cc ports, perf rpm & 650dp or Holley efi, and more cam, shooting for 8.3-8.5 dcr and 10.5 static.

that makes it a 375cfm carb, hehe.

If you disconnect the secondaries and make a 2-bbl out of it , it's the same as a 500 cfm 4412. That's still hauling ***, though.

We're going the other way - putting a 750 on in place of a 500 2-bbl. It'll be interesting to see the dyno results. I did a circle track car last year that gained 30 rwhp swapping from a 4412 to a 4779.

I stand corrected, but appreciate the compliment! :D

I believe it, I pick up alot going back to the secondaries.

[QUOTE=boodlefoof]Speaking of intake port sizes... I came across a post on another site which seemed pretty interesting... about how port size isn't important really, but rather port cross section is.

I think this is a big part of the equation. A key to good response is keeping the velocity in the intake port high. Chevy has done this with current engines by making the ports tall and skinny. The "flow" will naturally be at the "outside of the curve" that's why every bend in every river is deep on the outside and a sandbar on the inside.

The current gen3 heads use the same exact intake port on a 250hp truck motor, a 400 hp LS6, and everything in between. It works because the tall skinny port keeps the velocity up. As flow increases due to demand, the port gradually fills from top to bottom, but the narrow cross section always keeps the velocity high.

However much debated, look at NHRA stock eliminator. Particularly look at the 305 combo in the 80's camaros H/SA and G/SA going 10.90's with ports that are roughly 160cc's and MUST remain untouched. No doubt these heads are touched, but the fact remains they're a small port!
Small ports are not the restriction that everyone makes them out to be.

If your goal is 12.00 with a 406, you dont need a Huge head to go 12.00

Take a look at my engine, what i do to SLOW IT DOWN TO 12.00 is Unhook the secondaries, and shift at 5800rpms. that makes it a 375cfm carb, hehe.

But Brian, how much faster do you think these guys would go with bigger port heads? ;) I know a guy that played the stock elim game back in the 80 and 90's and he would search forever to find an X casting (larger runners), "some" would acid dip (illegal but hard to detect) and pull all kinds of tricks to make their ports bigger and their cars faster.

I agree with you that small port heads are not always a restriction (especially on a small cube motor), but in this hobby there always seems to be folks that like the extremes . . . bigger is better for most, then the knee-jerk reaction "smaller is better" crowd. LOL

There are ways to calculate how big/small a port minimum cross-section should be. I think this is a great tool when in doubt about port size and have actually put it into an Excell spreadsheet -- just email me if anyone is interested.

Not arguing or attacking BTW . . .

PS. One of these days I'm going to have to unhook my secondaries just for grins . . . LOL Wonder if I could still run in the 11's . . .

You should still be in the 11's with a 2BBL. I know that Red Camaro is going 10.90's this season i bet.

I know what your saying, and Putting the Correct port on the engine is the best Idea, however while most favor of the large port, in my opinion i'd rather choose a port on the small side, especially if he Loves good throttle response.

My suggestion for his 406, and since he only wants to go 12.00 is a 200cc head with Bowl Work done. that will be plenty for that 6000rpms 406 and on the large side.

The down side of a Large Cross Sectional Area is the need to turn alot of RPMs to get the thing Moving. Again i'll make a reference to Stock Eliminator to put things in perspective.
Take the 396/375HP combo with Factory aluminum heads factored to 395HP i believe. The Cowl Hood/Holley Carb combos.
They have a head that starts off at a 300-310cc Intake port, and they Need to turn 8000+rpms to Move them. With a 5.13 gear at 3500lbs. However the good ones go 10.50's and quicker.

Obviously Much Different then a 406 small block, but worth taking into consideration.

As we say in NJ.....I'm just sayin' is all :D

I agree Brian with your pick on this 406 -- a good 190-200 cc head would be about perfect.

My point though is that a 200cc head could have a minimum cross-section of 2.1 sqin, or 1.9 sqin, or anywhere in between depending on where in the port the volume is at (ie: in the bowl, in the runner, etc). 1.9 sqin would be a little small and would result in a flat power curve above peak TQ.

Usually the pushrod tube is the bottleneck on a hot SBC head and depending on how the port is designed (or ported) a 200cc head could be too big or too small on a particular combo.

I bring this up only because I found that my TFS 23* heads in there stock form had a minum cross-section of only 1.93 sqin. This was good to 6000 RPM in my 383. I did some bowl work on the heads initially and the heads didn't respond well. Eventually I pulled them again, measured the minimum cross-section and opened up the opening by the pushrod buldge. This all by itself resulted in a measuable flow increase especially at higher lifts, and more importantly it resulted in some ET improvement.

You're exactly right about the BBC H-stock or G-stock motors . . . giant ports need way more R's -- one of these days I'm going to measure the port cross-section of a rectal port BBC casting and play with the numbers.

BBC's and SBC's are soo odifferent IMO -- the SBC started with the tiny little 265" motor in a compact package and as a result ports tended to be undersized when the the mouse grew up. The BBC also started small, but fortunately there was ample room in the big block package to make ports that were "reasonably" sized LOL

interesting discussion -- I always liked this topic :D

. . . as they say in certain parts of Michigan, "das wuz hapnin" LOL

The 69' camaro BBC 396/375 3500lbs factored at 390 or 395hp (i forget which) is B/SA.
The 305 Mid 80's camaro Combo is H/SA and G/SA

All in all i think what he wants is what we're leading him too, and thats a 6000-6200rpms 406 Small block, although a 385 would work as well.

I think you will agree with me, when i say that a 200cc head will leave plenty of room for cam changes, and faster ET goals, as well it will be suitable for the current combo.

Larry Meaux is a good guy to talk too when it comes to this topic, i believe he holds a national record in his class in Super Stock.

As far as carburetors go, i'd look at a 750HP holley with mechanical secondaries.

My 2-cents please..

It's actually gearing b/c if your gearing AND tire size aren't matched to the cruise rpm of your cam, (which I figure is actually pretty close to just below your motors torque curve's peak), it won't have the grunt to accelerate like you want and are calling throttle-response..

A lo-po motor with a stock cam and factory gears will have good throttle response as will a 10 to 1 CR. motor with a 270/224 or 280/230 cam with 3.73's and 26" tall tires, (depending on motor size), again imho!!

AND tuning like said is very important BUT if you have a hi-po cam with 3.07's and 26" tall tires, no amount of tuning will pick it up UNTIL she come's "up on the pipe" as the 2-Stroke guys like to say!!

Been there, done that with my Strong-arm 406 SB motor years ago that's sitting on my motor stand now.

pdq67

Most of this I understand, and some I don't. Cross section? What is that? As I figured all the components of the combo must work together in order to achieve the throttle response Im looking for. I know I will be wanting to go faster and faster in the quarter eventually (the bug) so don't want to be limited, and I am glad to see it will be possible to run fast and still have my throttle response. I highly doubt I will buy a single component without checking here to see what you guys have to say about it. This site is the best. In less that 60 days I will be able to start ordering parts, and I can't thank you enough for your advise.

Darren

67CamaroD, minimum port cross-section is just the measurement of the smallest part of the port. Height times width at the smallest point. This is where air velocity will be the highest.

The theory is that velocity can only get so high before the engine starts pulling vacuum in the port downstream of the restriction; when the engine starts pulling vacuum in the port power production goes flat. The opposite happens when the cross-section is too big, low velocity allows for fuel to drop out of suspension resulting in poor mixture quality and poor throttle response.

The engine doesn't "pull" a vacuum, it creates it by the intake stroke and a closed throttle plate. The earth's atmospheric pressure outside is trying to equalize the vacuum.

I use a 3310-5 750 CFM with vacuum secondaries, with the lighest spring and the secondaries do not open.

Sure it will if there is a restriction . . .

For example, if you put a small carb on an engine and run it to 7 grand you will measure vacuum in the intake even though the engine is at WOT. Its the same thing in a port when velocity is max and the engine wants more air than what can come through the port . . . granted you won't be able to measure this at the plenum, but inside the port the pressure can definately be less than one atmosphere.

Maybe this is just semantics here and I'm missing your point ;)

PS. if your vac secondaries aren't opening at WOT / high RPM on a car running 11.90's something is wrong ;)

Agree with you 100%, but its the engine creating a vacuum and atomspheric pressure, the pressure, 14.7 psi absolute, of air we live in, is trying to equalize (shove air pressure into) the vacuum, a value less than the atmosphere.

If you have two air tanks, one pressurized to 100 Psi, the other at a vacuum. Connect them together via a hose and valve. When the valve is opened, the pressurized tank will unload into the vacuum to equalize the pressure in both. Its not the vacuum tank "drawing or sucking air," its the higher press tank equalizing the pressure in both tanks. Both of them will come to an equalized pressure, whatever it may be.

Yes, I know I could go faster. I just haven't dealt with it yet. I did drill out the orifice in the body to a #43 drill bit to increase the vacuum quantity to the diaphram. Haven't had a chance to try it out. I'm stuck working on the left coast.

Too many responses to read so here is my 2 cents. Perhaps it will jive with what others have said. Good throttle response comes from a few things. First, don't over-carb the motor. Second, use a vacuum secondary carb. Manual transmission setups will work fine with a mechanical secondary carb, but automatics work better with VS. But in any case VS works best for the street IMHO. Use vacuum advance. Don't cam the motor so much that you loose power below 1500 RPM. Use a head with 190cc or less of intake port volume. Use a double-plane intake. The port volume and double plane will keep the charge volocity up where it needs to be for street use.

Don't forget that aggressive intake valve opening rate and earlier intake valve open timing will have a major influence on throttle response. The throttle bore area or flow vs. total intake volume will also have a major influence.

But, just as with most things about the engine, barely enough is just right!

Yeah I see what you are saying Everett -- I guess its all relative . . . technically a vacuum is just 0 psia . . . LOL

I'm getting ancy . . . the track is opening tommorrow and the weather looks gorgeous :D

Eric, A vacuum is below 0 psia. Zero psia is more pressure than 29.96 in/Hg. at sea level. I agree with restrictions, NASCAR restrictor plate engines are running 15-17 in/HG at 9000 rpm.

True, R. Davis

Wish you luck at the track, Eric. You should run good, new valve springs, new gas delivery system, low humidity, mild temps.....most of all, Be Safe.......and one suggestion I found to be most important......."THINK"

Everett, sorry to disagree again, but 0 PSIA is 0 PSI Absolute which means a perfect vacuum. 0 PSI (not absolute, as read on most gauges) is actually equal to one atmosphere or 14.696 PSIA.

Another way to look at it is 0 PSIA = 14.696 PSI

1 atmosphere or 1 Bar = 29.921" HG or 14.696 PSIA, 0 PSI (as read on a presure gauge)


I hope I run good . . . the car feels good just cruising around -- hopefully it will fly at the track too !

Enjoy your weekend!

Have a good weekend yourself

Another way to look at it is 0 PSIA = 14.696 PSI

That is incorrect. Pressure is measured as psia or psig. psi should never be used because someone may think psia and someone else may think psig. 0 psia is a perfect vacuum. Atmosphic pressure is 14.696 psia, provided you live at sea level. 0 psig = 14.696 psia. psia = psig + 14.696. A pressure gauge reads 0 when it is not connected to anything, 0 psig, but we are under pressure, 14.696 psia; therefore, psia = psig + 14.696.

So if I am pulling 8 pounds of vaccum at 2000 feet of elevation with 200cc runners going down hill in a 3400 pound car my psia psig would be what?
Just kidding. This is turning into a very interesting and educational post for me. Every time I figure something out about going fast, I realize theres 3 more things I don't know. They say, "the smarter you get the more you realize how little you know." I should put that in my signature, LOL
Darren

GWBUTCH, now you are just nit-picking ;) unless you are dealing with engineers or scientists it is generally understood that PSI and PSIG are the same thing . . .

Well, I just happen to be an engineer, so that's why I want to clarify. :D

:D

I'm an ME too, and could care less....................

Picky, picky, picky!!!

pdq67

I'm an ME too, and could care less....................

I find that kind of insulting, Paul. I am not an ME. I am a ChE. :D

ChE? Danger!..............Danger!, Wil Robinson! Just kidding from an MfgE :>)

He, He!!

Good thread, imho..

pdq67

this was a good thread, till the initial gand took over!

this was a good thread, till the initial gand took over!

Define, please

The higher altitude, the lesser amount of vacuum indicated/obtained.

Unless otherwise noted, reading an PSI indication on a gauge is considered PSIG. Reading absolute PSI is done by either the gauge itself or the reader of the gauge .

this was a good thread, till the initial gand took over!

Its a good thread if you like engineering!!! :D :D ;)

I gotta do something about that keyboard... or is it the fingers?

meant "initial gaNg" as in ME. ChE, psia & psig...

He, He!!

Thanks Brian for spelling it out...

Let's continue.......

pdq67

Can someone provide a photo of measuring minimum cross sectional area?

Also since it takes both the velocity that comes from the runner and the flow as measured at the chamber (I think) has comeone come up with correspond info between the two.

It would be great to get a 2.16 sq.in. area with lift of about 250 at .400" lift...