After market intakes

[insane147]

Can someone tell me why every after market intake manifold i have seen so far only goes for large plenum area and higher flowing runners instead of also tuning for a higher return wave. as you shorten the runner length, your return wave gets weaker, so in reality it should be longer, like the ram jet engines of the CAN-AM era? this tuning has been known to provide substantial gains when matched to cam and exhaust primary lengths of the right combination. my thoughts were that there is just not enough room in the engine bay, but even in the top level where RWD opens things up considerably short runners are still used??

 

[TheSh111t]

I know what your saying about the "Return wave" or intake resonance and while it did/does work on naturally asperated cars, it is not nearley as big a deal on forced induction cars. The intake manifold is under pressure, so the "Wave" is not going to have nearley as big of an effect on the cars performance as it would a N/A car. 2 stroke engines (I.E. dirtbikes snowmobiles ect.) use an expantion chamber on the exhaust to do much the same thing. But if you have ever looked at a turbocharged Yamaha Banchee or other turbocharged 2 stroke engines, you'll see that expantion chambers are not used. I understand that this is a differant application of resonance, but the principle is the same. The resonance is used to "Bounce" air into an engine at a given RPM, or I should say a narrow band of RPMs, but when you force air or air&fuel into an engine with a turbocharger or supercharger the effect of the "Wave" is farr less effective. Just my 0.02

 

[insane147]

makes sense considering the lack of cam overlap the turbos have.

 

[Big Woo]

THEsh111T summed it up quite well. Reasonance tuning is still alive and well in N/A motors, and forced induction engines as well. Plenum size is a function of displacement with most using volumes from 50% to 200%.
Generally speaking smaller plenum better throttle responce, less top end power, larger plenum vice-versa.

Yes the glory day of big can/am engines are over, and if you compare what they were doing with what is being done today there is no comparison. Short and variable length inlet trumpets are the norm today in the no holds barred, money is no object, in formula one today. Chech out some of the engine manufactures, such as Cosworth, Illmor, Ferrari, BMW, Renault, There are some some other good infor sites as well, f1mech.com, f1-live.com. Some very interesting tuning going on here if you would like to see what the best in the world can do with an unlimited budget.

 

[JAYTEE]

To insane147 and TheSh111t,
The resonance referred to is actually the sine wave of the tonewhich is generated by the valve opening and closing. This action acts as the
reed in an open end organ pipe. It creates the interuption in the pipe
(runner) which becomes the tone of the runner based on runner length
and diameter. When properly "tuned" the length will be equal to an even
multiple of the full wave length. i.e. 1/8, 1/4, 1/2, wave length. This
concept was applied by the "Ramchargers" racing team in the late 50's
and early 60's. In 1964 Dr. Blair, of The University of Arizona, published
a considerable piece on the open end organ pipe and susequent methods
for tuning an engine with these principles. Forced Induction engines are
not effected by these ram principles. They are effected by the overall
volume of the intake plenum and runners, however. Wat to complicated
to go into in detail here. There are simply too many factors and variables
to cover, but you guys are on the right track.

 

[insane147]

you are entirely wrong. it is a FINITE AMPLITUDE WAVE. check it out some time. the organ pipe is a long time myth that has been positivly displaced by science now. length is determined by this formula
2nd pulse length: 108,000/RPM
3rd pulse length: 97,000/RPM
4th pulse length: 74,000/RPM
5th pulse length: 54,000/RPM
i posted this elsewhere, so its just easier to copy it here for an explanation..

first......its not just manifold tuning.....its the whole system, from air filter to exhaust tip that counts, including the cam, all are intertwined so much you cant change one without making a problem somwhere else. the reason is very long. yet i will explain. ready....

the air-and-fuel and exhaust gasses that move within the passages of theinternal-combustion (IC) engine behave in an UNSTEADY manner. in other words the gasses are constantly changing pressure, temperature and velocity throughout the four cycle process of induction, compression, expansion and exhaust. to analyze and simulate these actions, we must rely on the discipline of UNSTEADY GAS DYNAMICS.the sounds we hear are actually small pressure disturbances in the air. we call these pulses "acoustic waves".the pressure amplitude (volume)of these waves is very small. as an example, the volume at which you will begin to experience pain is 120 decibles and creates a peak pressure of only 0.00435psi above the ambient, the undisturbed air. since sea level air pressure is about 14.7psi, then the pressure ratio at which sound becomes painful is:
Pr= P/Pa
where
P= 14.7 +0.00435
= 14.70435 psi
so:
Pr= P/Pa
=14.70435 / 14.7
=1.0003
or three one hundreths of one percent increase over ambient pressure! very loud acoustic waves create very small pressure disturbances. there are waves that produce substantially higher pressure ratios than even loud sound waves. they are calle FINITE AMPLITUDE WAVES. pressure disturbances of these higher intensities can be found inthe induction and exhaust of the IC engine. prssure ratios of 2.5 can be measured (thats 10000 times louder than 120db!). this enormous diffrence in intensity between acoustic waves and finite amplitude waves gives you some idea why acoustic theory (still commomly used) for calculating the optimum tuned lengths of intake and exhaust passages is misleading. finite amplitude waves take two forms in an IC engine, compression and expansion.the compression wave is a positive pressure disturbance that will always have a ratio greater than one. the expansion wave is a strong drop in ambient pressure, and will always have a pressure ratio less than one (negative). expansion waves are also known as as "rarefaction waves" and "suction waves" . compression and expansion waves behave in similar- but uniqely diffrent- ways as they move through the IC engine passages. picture a positive pressure wave traveling from left to right in a pipe. as the pressure wave travels rightward, they drive gas particles in the SAME rightward direction. however the velocity of the gas is considerably slower than that of the wave. the same as a ripple in the water pushing a piece of wood as it passes. now picture an expansion wave traveling left to right, however, as it passes through gas particles in the pipe it propels them in the OPPOSITE direction. in this case leftward. the same way as when you take in a deep breath the oxygen fills your lungs but the sound of the rushing air travels in the opposite direction. both types of waves change their character when they encounter sudden transitions in area. area changes within engine ducting occur at an open end, or an closed end, or at an transition to smaller or larger diameter passages. such as header pipes going into a collector or intake tubes into a plenum....what happens when a finite amplitude wave reaches one of these areas? picture a compression wave mving right down a pipe, as it comes into the larger diameter pipe the compression wave is refracted as an expansion wave back DOWN the pipe. this has fascinating implications for particle movement. initially when the compression wave moves to the right it propels the gas particlesin the same direction,toward the end of the pipe. when the expansion wave is created and it begins its leftward movement, it continues to drive gas particles to the RIGHT (remember particles travel the opposite of an expansion wave), it helps propel gas particles in the same direction, out of the pipe. these pressure waves were a phenomena, particularly as they apply to the exhaust system, were not understood until the 1940s. until that time it was assumed that a high pressure "slug" moved through the header pipe and created a vacum behind it that helped draw out residual gases. despite the fact this theory(Kadenacy theory) was conclusivly proven to be incorrect nearly 60 years ago, itis still believed by some engine "experts" to this day. the goal of the HIGH PERFORMANCE engine builder is to tune the lengths of IC engine passages so that the reflected waves reach the cylinder at the most effective times, either assisting exhaust gas outflow or induction charge inflow.there are many factors that would affect the arrival of these waves. a short list would be valve timing, cam profiles (lift and duration), piston speed, pipe lenghts, valve discharge coefficients and cylinder blowdown pressures.. to make things worse, the peaks of finite amplitude waves travel faster than the base of the waves, causing wave profiles to distort as they travel throught the engine passages. this can cause the wave to "tumble" over itself forming shock waves and converting their energy in to heat. the first part of effective intake tuning begins with good exhaust tuning. when the exhaust valve opens it generates a powerful positive pressure wave that travels down the header pipe and returns to the cylinder as a strong expansion wave. when the timing is right, this suction wave will arrive during valve overlap and draw out burnt gases while starting the inflow of fresh charge. this scavenging effect lowers cylinder pressures just before the exhaust valve closes, early in the intake stroke. after evc, the piston begins to move rapidly down the bore and when it reaches maximum speed, between 73 and 82 degrees after tdc, the rapid increase in cylinder volume will "yank"down the already low pressure in the cylinder.this will occur at between 433-442 degrees and is usually the lowest point in the cylinder pressure trace. this sudden pressure drop creates a strong suction wave that travels toward the open end of the intake runner where it is reflected as a positive compression wave. depending on the lenght of the intake runner and the speed of the engine, this compression wave will return to the cylinder just before the intake valve closes. this has two benefits, first as the wave moves through the port it ushes particles in the same direction, helping to fill the cylinder. when the compression wave reaches the intake valve just before IVC, the positive pressure 2) ovecomes the build up of pressure in the cylinder created by the piston, now moving up the bore on the early part of the compression stroke.this forces additional charge into the cylinder while delaying charge reversion until just before the intake valve closes (ram tuning). if the timing of any of these events is off, your #@%#@%#@%#@%ed, you get fuel reversion, flatspots, backfires...etc.....there is soo much more but my hands are tired, if you wanna borrow the book, let me know.

 

[JAYTEE]

Obviously, you have done your homework. It's a good thing that the
internal combustion engine isn't as fussy about its diet and surroundings
as the books would indicate. If they were, we'd still be riding horses.
Interestingly, the Finite Amplitude Wave equation which you discussed
yields the correct runner length for the Chrysler Corp. short ram induction intake manifold. They must have understood these principles. In addition no mention has been made of the large number of bends, surface finish,variations in temperature(within the individual manifold, header, etc.), all of which are involved with hyraulic flow efficiency and the laws of Thermodynamics. Nothing likes to go around corners; fluids, gases, and sound waves are amoung these. This is due to inertia. Racers will scrub off speed by weaving the car left and right, which consumes energy and slows the car. It may be that my simplistic response to what appeared to be a couple of "bench racing" questions, by you and others was "entirely incorrect" as you put it, but the essence of what I described functions, within the understanding of most hot rodders or import tuners. I have been building street, circle track, drag, and marine engines for 44 years. I don't know all there is to know about building engines. In fact, like most builders, I have a limited knowledge about all of the possibilities involved in this science. This is the reason why "The Man to Beat" this year is next year's truck driver. New understanding of the many systems related to IC engines is being
exposed continously. Thanks for the offer of the loan of the book.
However, my thumbs are deteriorating with age and my engine work
is now limited to my own car, and my son's. By the time I absorbed all
the book had to tell me, I would be unable to play with it.

 

[insane147]

i had indeed said something about the other variances in my write up:
in the beginning of the 3rd paragraph. shortly, thats a whole other book . i was just explaining how the finite wave works to displace the organ pipe theory. keep in mind that if it were not for us "bench racers" that many things would not be understood, hence maybe not even made.
iti is the peolpe who want to know why things do what they do and try to improve that which has brought the modern engines so far. billions of dollars are spent on "bench racing" research. my original question was why doesnt any aftermarket intake maker seem to tune for this? the increase in efficency alone may well be worth it. but , like i said, i dont believe our engine bays have the room for the intake length it needs, so that must be the trade off.

 

[Big Woo]

Insane147 good post, I think I have a book sililar to the one your refering to.

If you use 7000 rpm as a tuning point then your runner lengths would be
15.42" 2nd pulse
13.85" 3rd pulse
10.57" 4th pulse
7.71" 5th pulse
using the formula shown above.

If you increase the rpm to say 9000 then the 2nd pulse distance shortens to 12".

If we increase it to 18,000rpm (ala F1) that distance shortens to 6" for the second pulse.

This is all very simplified, since we have not accounted for cams, intake, and exhaust port shape, size, surface finish, valve size, cam timing, exhaust tuning from port to atmosphere, intake from atmosphere to port, compression ratio, ect. ect.

Anyway this does show that the closest intake to the original question in this thread is the stock intake which has a port length of about 16" I think, but I can't remember the exact length for sure.

My .02 on why you don't see more intakes with alot of resonence tuning built into them.
1: too costly
2: to many factors will change the ideal runner length. So it would not be the best intake for tom, dick, and harry's cars since they all have slightly differing setups.

Question: does anybody remember what ended the big ram jet Can-AM engines dominence in Can-Am racing?

Awnser: It was small displacement turbocharged Porsche's running 60+ lbs of boost. Its ture check it out.

 

[insane147]

porsches take out most of the compition because of their reliability and refinement over the years also.....lets not forget big engines need big chassis', so a small motor with the same power ina lighter car will rule.

 

[jltcat]

Hey insane to make an intake manifold to fit "your" car would not be worth it to the manufacturer because they have no way of knowing the parts (engine) combinations that "you" have. To make one to fit your car requires them to know exactly what "your" component parts are and what "your" goals for "your" car are.

" " = general public

 

[insane147]

this could be done very easily in a round about way....take for intance the holley and edelbrock lines for the v8s. not gonna be perfect but damn better than one thats gonna be way off. they could make a line that goes from one power range to another and have basic guidlines or kits to follow....for each step. ie: performer, performer plus, performer rpm, victor jr, victor...they do their testing on all those intakes, cams, exhaust etc......just shows you how far our engines really have left to go on terms of refinement.

 

[GTM]

Originally posted by insane147
porsches take out most of the compition because of their reliability and refinement over the years

Hi all:

Lots of great posting here with a wealth of first hand info.

Having been around the block more than once and my finger prints exist on some 15,000 cars over more years than I care admit including Porsche, I'm not convinced of any singular product's superiority over another. One maker may have the edge for a year or so with one particular series which may not available for general sales distribution. Were I a car collector and an unlimited budget I'm sure there would be room for a 904.

With such a wide diversity of members with limited budgets a $600 water pump does not mean it's going to last any longer than another product. My point is be an informed buyer especially when selecting a used vehicle knowing you can't obtain parts at realistic prices should something fail. As best I can tell the DSM is a decent vehicle at affordable used price giving an awful lot of bang for the buck and enough competition in after market parts to keep things running without the kids going barefoot. I can remember back in the days of air cooled Porches ('60's) when crankcases were too soft and cylinder studs and case bolts stretched enough to require adjusting valves once a week unless you didn't mind the $28 each when they burned yet buy the same valve at VW for $4.00...

It is this DSM cost attractiveness which has brought about the interest, you don't find this as true for example within the collective Porsche owners. The initial outlay and replacement parts prevents this exploration given the same elbow grease energy level. I have no stats on cost per mile for any product but my guess is the DSM series would fair better given the same attention to routine maintenance.

I'm not intentionally trying to be contrary, just a little leary of blanket product endorsments with a such wide diversity of readers. When they make the perfect machine we will all own them.


Cheers,
GTM

 

[insane147]

this type of situation has been talked about for a long time.....the one where the car or engine has been around for a while, gets better every year with refinements, only to be shelved for the newest and greatest technology and the learning process' starts all over again on a new design. alot of people believe that if if its working reliably and has room for improvement, there is no need for drastic changes, and from everything ive seen or read, porsche is one of them. i wonder how far our drivelines will grow before being skipped over for the latest and greatest from mitsu (when and if). i hope they continue well into the future with the 4g63, continuing to refine an already great overall package, just needs a worthy tranny.

its hard to have supiority in racing when you have 3.6l ? going against 7.xL? corvettes and 8.xl? liter vipers (lemans). the rules make it fun...most times.

 

[hose101772]

Ok here we go.if you will notice,none of anyones formulas take into account applications for over atmospheric pressures.As sonic waves travel slower the denser air, also you will never have a vaccume in the exhaust, pressure differential yes,vaccume no-theres huge restriction 12" to 18" away-THE TURBINE.Thank you for letting us all know that headers need not be arranged in any particular manner as there is no vaccume created from exhaust pulse movement and for the same instance they need not be any particular lenth.Sounds good but ahhh no thanks.

 

[insane147]

in high end racing they dont use high back pressure turbine housings, lag is not a concern as much as crossover and VE. they do indeed tune for primary length. take a look at the lemans racers or top drag racers, they all have long primary tubes with low back pressure (higher a/r) turbine housings....

 

[89PROOF]

In respect to the original equipment manufacturers producing that 'perfect' intake manifold, well, patience. General Motors for one, and probably every other major auto manufacturer for that matter, has a development team working on it at this moment. I'll quote from the Feb. 2003 'Hot Rod' magazine that just came in the mail 2 days ago...<BR><BR>
"Every few years, GM Powertrain displays its wealth and bounty to select members of the enthusiast press...These powertrain products represent future RPO's, not experiments....<br>
Northstar 7.5L V-12<br>
...460 cubic inches... DOHC, aluminum 60 degree cylinder case... Technology included Displacement on Demand, direct fuel injection (into the cylinder rather than intake manifold runner), varible cam phasing, variable intake manifold, and rear chain timing drive."<br><br>
It goes on to tell of a production Twin Turbo Vortec inline six cylinder; a 4.2 liter fitted with air-to-liquid intercooler and a turbo setup that allows one to spool at lower RPM and pull off the line, and when it approaches its maximum output, the second larger turbo is spooling up to pick up where the smaller unit leaves off. Interesting, but more so the features packed into the Northstar V-12. I can only speculate on what Displacement on Demand will be capable of, but the variable intake manifold sounds precisely like an attempt to provide the perfect intake runner volume for different RPMs. I'm pretty certain this will interface heavily with the rest of the engine management sensors and provide the perfect intake runner for your driving style while fitting within the confines of an already cramped engine bay.<br><br>
Check out the intake manifold design on a flathead ford, a '50 chevy, a late-60's muscle car, an early 80's throttle body injected 4 cylinder, and then on a multiport injected Taurus SHO (for example) and you'll see how much the technology has evolved, and can speculate on just how much more room for improvement there may be. Then someone explain to me why spherical rotary valves haven't replaced camshafts and poppet valves? Sorry for quoting Hot Rod magazine in an import performance forum but I think this proves the OE's are still on their toes.

 

[mrmadmax]

Originally posted by insane147
...the goal of the HIGH PERFORMANCE engine builder is to tune the lengths of IC engine passages so that the reflected waves reach the cylinder at the most effective times...

So, you mentioned in your "book" that these are finite AMPLITUDE waves, but what about their speed of propagation? Do we still assume that they propagate with the speed of sound? If so, I get around 15" runner length or so assuming an RPM of 7000 and a crankshaft displacement of 200 degrees for the second wave (similar to yours), but what do we do when density is increased (under boost) and temperature becomes a huge variable that depends on intercooler efficiency, saturation, ambient flow and temp, etc; thus changing the velocity of sound?

My guess (and it's just a guess), as an answer to your first post, is that the aftermarket manifold makers are taking advantage of the 4th or 5th reflected wave (whether they know it or not) because the shorter lengths are less sensitive to all the variables and will give the best performance on the widest range of vehicles. They have likely come to this conclusion through dyno testing, where the versitility far outweighs the "optimum tune".

You could very likely come up with something far better if you truly understand the fluid mechanics and related esoterica you are quoting, but I think it would be suited best for your application, and perhaps less so for someone else. Try it, and let us know your results!!