Jim R.

Mark,

I'm no tuning expert, and really hate to jump in here, but...

Suppose those spacers lean out a cylinder or two just enough to start a bit of knock. Just enough to light up the sensors, not enough to hear over the exhaust. The knock sensors pull back a bit of timing, and you lose 25 hp/30 ft-lbs.

Just a theory, and no real way to know what is going on there without being hooked up to the Sharktuner.

Jim

mark kibort

I am not either, but I would think knocks would cause the HP curve to have dips, but if it didnt, all 5-6 runs wouldnt look identical, would it? When Mark had the knock sensor issue, (bad sensor) he lost a bunch of top end, not mid range. knock sensors retard the timing, which is confusing, because you think that would increase high rpm HP. Maybe the level of retard kills high rpm HP.

Im sure anything is possible, but the mid range from the moment we went WOT, was 30ft-lbs down. Im sure there could be a few reasons for this, but it looks like fuel, at least for the first 1000rpm was not a major factor of it.

Sure, the shark tuner will be able to tell us much. obviously that will be the next step

mk

jon928se

Empirical basically means the application or use of experimental results with no consideration of the scientific theory behind those results.

You'ld be very surprised to know that in something as simple as structural engineering of statically determinate systems, empirical data is still used to verify and "correct" theoretically derived results, and that a significant proportion of the content of design codes used worldwide is still based on empirical data.

What this has to do with MK's intake I don't know - maybe MK is developing empirical intake theory from scratch, in which case a better starting point would be 8 individual 1.5" SU's followed by 4 pairs of 48DCOE's

hacker-pschorr

When I watch Todd inspect spark plugs he pulls out a somewhat powerful magnifying glass to look down into the spark plug. There is more to look at than the electrode.
On they dyno they also do a WOT burn then shut down the motor, pull the plugs ASAP to read them. After you've driven around a while, you are not going to get a good reading of WOT.

I'm not that advanced in my plug reading, I'm just looking for damaged porcelain

mark kibort

"Relying on or derived from observation or experiment: empirical results that supported the hypothesis."

In this sense of the word, scientific statements are subject to and derived from our experiences or observations, which is by definition, Emperical testing.

I have not only shown the results of the observations, Ive supported them with theories and staticstics . It is still a theory. More information and testing is needed before we have conclusive proof that what I observed as far as HP loss with the side plates was indeed caused by the altering of the intake chamber configuration. by going back to the dyno, i could prove that the HP was gained by their removal. Ive got times that support that Hp was restored in the mid range, and dont feel its worth going back to the dyno. However, as soon as one more person attachs the side plates on a stock intake and sees similar results on a stroker, we will then verify the theory.

We all know how critical system shape and configuration is to air flow. sometimes the littlest, intuitively non important stuff, creates HUGE problems for air flow. The harrier Jump Jet cant take off with screens on the intake, bell mouthed inlets vs straight edge inlets can reduced flow by 50%, etc.
Who would have thought that allowing the 928 plennum chambers to talk from 3700rpm to 5500rpm , that you would GAIN near 30hp and 30tf-lbs of torque???
Since we are now altering that shape and configuration with the plates, it seems to reason that the side plates can alter the effectiveness of that system.
Inlet guide vanes are very effective in guiding flow during curved paths. the stock side plates might effectively act as an inlet guide vane for air making more than a right angle turn up from the "U" area and into the runner.

Lots of questions, only theories right now based on emperical and some air flow theory

mark kibort

Ive done that many times as well. No only at the dyno, but on the freeway too

Ill do a 60 to 100mph run in 3rd and kill the engine and coast of the freeway and pull a plug, looking down the center electrode and insulation area. the outer ring showing black means RICH. If it is clean, it means lean. It should be a light coating. The insulation, with a magnifying glass, will show peppering of shiney material. this is detonation. I havent seen this.

However, any major pinging, mixture issues can really be seen on a plug just by pulling it. a really rich motor will have dark looking plugs. that electrode looks pretty white actually. The proof is in the plug, but I agree to get the full picture, you need to look down the plug with a special magifying glass.

Scots engine for example had a lot of carbon build up on his pistons with his rich mixture. (when we pulled the engine and looked down the plug holes) I dont see any of that on the pistons in the stroker motor as of 10 race days and some decent miles.

mk

mark kibort

As far as the plenum size is concerned. Porsche went though a lot of engineering to make sure the plennum size was correct for the flow of air air going though it. It would seem to me that, since the volume is a critical element of the resonance characteristics, that if it is changed, we could effect the efficiency of the design, or negate or even create opposite effects. I dont think you can just "tune" around a resonance effect. (a guess)
Again, this theory might be proved is someone else with with and without spacers can do a dyno run on a stroker.

Here is a little blurb on Helmholtz resonance:

Helmholtz resonance:

Applies to intake manifolds. This resonance effect on the intake filter system is negligible. Helmholtz resonance applies to IM and
is due to the intake valves opening and closing. This results in pressure build-ups and releases and air traveling back and forth
with into the intake manifold. The effect is comparable to a mass on a spring, oscillating up and down. Runner length (and area)
and plenum volume on an intake manifold are sometimes designed to effectively use this pulsating effect to increase efficiency in
certain rpm ranges. In the 1960’s Chrysler did a lot of research in the area of Helmholtz resonators. A quick little formula was
found to find the approximate area for this effect.

RPM ~ 88400 / L

It is found from the following.

Speed of Sound (V)
V=sqrt(Y * R * T)
Y= 1.4 (specific heat of air)
R= 286m^2/s^2/k (gas constant of air)
T=273.15 k (0 c)
V=340m/s=13400”/s (~15 c)
V=355m/s=14000”/s (~40 c)

D = Distance
L = Intake Length
V = Velocity
T = Time
F = frequency
N = Round trips
RPM = RPM of Peak Efficiency

D = Vt
T = D/V
F = 1/T
D = 2L * N
RPM = (V/D)*60
RPM ~ 84000 / L (5 return trips).

The shock wave or wave front from the valve events oscilates/bounces back and forth several times (5 times) between valve events.

Ideally at "resonance" the wave front hits the valve as it opens.

That is the theory behind the N = 84000 / L ~ (V/2L *5)* 60 (depending on V - seed of sound)

If your intake manifold runner length (to the valve) it is possible to hit multiple “resonance points”. With a runner length of 16”
resonance will occur at N-5,4,3 with peak efficiencies at ~ 5250, 6550, 8700 RPM. A change to 14” will produce peak efficiencies
at ~ 6000, 7500, & 10,000 RPM.

N is the ~ engine RPM of peak torque
L (“) is runner length from the IM plenum to the valve.

Short Intake Runners help high RPM torque.
Long Intake Runners help low RPM torque.

Tom. M

So..maybe those end plates on the S4 intake need to have a better "reflective" surface placed at each "runner port" so the pressure wave can travel much more efficiently to the opposing intake valve???

mark kibort

I dont know if thats it. it seems, like any "spring mass " system, you have a resonance frequency. the increased volume, changes the frequency. the pulses now, could be out of phase and there wouldnt be anything you could do to change that, unless you change the system. why it seems to work on the stock S4 is the puzzler.

I think if you optimize the system that is really designed to increase torque at the low end and increase torque at the mid range by opening and closing the flappy, you could find some volume and shapes that equal that performance. Im sure, as we have seen, it comes in a form that doesnt resemble our intakes. It would be REAL interesting to see an 85 intake on our S4 engines.
(or S4 heads on an 85).

maybe this exact resonance is critical to mid range torque. If you dont got it, sure you can get all sorts of big hp, but will never be able to capture the extra torque due to the resonance effect. (as seen with andersons and Fan's intake HP curves where they shed mid range for big High end HP gains.)

mk