nasty9er

ok well i did some math and i wanted to see if i am on the right track. i used the equations from this site http://www.chrysler300club.com/uniq/.../ramtheory.htm altho this is for 30 inch runners i changed a few thing

pressure wave travels at the speed of sound. A good estimate for the speed of sound is 1,125 feet per second.
For the web camshaft, the intake valve is open for 254* of crank rotation.
The engine rotates twice (720*) for the intake to open once.
720* minus 254* = 466* of crank rotation that the intake is closed.
At 4,000 RPM, 466* = .0194 seconds. (See below)



4000 rev/minute divided by 60 seconds/minute = 66.66 rev/second
66.66 rev/second X 360*/rev = 24,000*/second
466* / 24,000* per second = .0194 seconds.



This .0194 seconds is the critical time factor. During this .0194 seconds that the intake valve is closed, the pressure wave is moving at 1,125 feet/second and travels 21.825 feet.
At resonant conditions, the pressure wave has to travel 21.825 feet to arrive at the intake valve when it is open. Since the pressure wave spends this time going up the runner AND going back down the runner, the runner length is actually only half of 21.825 feet, or 10.9125 feet, which is equal to 130.95 inches.


this is where i start to get lost


runner lenght in feet(variable) divided by 1125 speed of air in feet = time it take for air to flow from runner to valve this needs to happin (variable must be even number) times to add up to a total .0194 seconds and 130.95inchs

if you devide the total time and the total leagth by an even number it should tell you the length of the runners so my first attempt was this
.0194/14=.00139 seconds per bounce 130.95/14=9.35 inch runner from vlave seat



any input at all would be great

Paulyy

https://rennlist.com/forums/944-turb...-manifold.html

on the last few pages there's 2 different runner length formulas. and some good info along the way

LP944

On my car I am debating whether to put on a GT scoop over the airbox, cut a hole in the top and seal it so it is "in theory and in my hopes" a ram air. (to match my front header panel and my future front bumper)

(Both concepts will have Miller MAFs)

My other plan consist of getting custom tubing and extending it from the MAF into a MAF trap from Lindsey and install the ducted headlight covers.

V2Rocket

neither of these ideas will work much if at all. the 'ram air' concept doesn't really do anything until you approach the speed of sound, and you'll need a turbine engine on your 944 to get anywhere close to that.

the headlight cover ducts are in a low pressure spot which isn't good to draw intake air from. where the OEM snorkel draws from is a high pressure spot at bumper height and really is about as ideal as it gets.

what i would like to see is a butterfly-valved double-length intake. one side would be a loooooooooong set of runners because the 944 needs torque desperately. the other side would be short for higher rpm power. with all the cars in junkyards now finding small butterflies shouldnt be a problem.

or....VTEC

nasty9er

thx pauly read throw it but it seems it is all about turbo apps and i am going to work on a N/A trying to get better midrange power gains............ i have a book being shipped to my place now called "Scientific Design of Exhaust and Intake Systems (Engineering and Performance)" so i will read threw it and relay the info i pick up ..... good news is i have two buddys one is a airplan engineer and the other owns a hot rod shop with a full machine shop, flow bench, and dyno they have made turbos and intakes for many apps but most are for new doges. once i walked in his shop and he was working on a twin undercarrige turbo kit for a challanger srt8 that was sick............... so if i do all the leg work i can do some testing for pretty cheap


y does every one like the miller MAF is it cuse it is cheaper and less work to install? it seems more restricted then the LR hot wire setup.

nasty9er

the speed of sound is the waves not the speed on intake air. and i dont think chrysler 300 moved at the speed of sound in the 60's


V2 you sound like you like to shoot ideas down befor they even get started.

MAGK944

The NACA ducts in the headlight cover draw air from the boundary layer by breaking it up and creating fast moving vortices. Doesn't matter that it's in a low pressure zone, boundary layers exist in high and low pressure areas.

The snorkel is in a low pressure zone.

Long runners do not increase torque, they do however lower the rpm of peak torque.

V2Rocket

im all for innovative ideas so long as they are actually checked for scientific basis before attempting. the idea behind 'ram air' is that youre trying to jam so much air into the engine that it backs up on itself and over-pressurizes for a sort of supercharging effect. but what really happens at much below sonic speeds (i am aware of the intake resonance you were talking about, this is different but speed of sound governs many things) is that air will jam into an opening to a point and then excess air will flow around it. only when you get going reaaallly fast will the air still jam in, like in the case of ramjets/scramjets. you are going forward faster than the air can bounce out/around.

what the old muscle cars did with 'ram air' is make a scoop big enough to create a sort of wall for air, building a high-pressure spot which did actually work for air intake. the 944 aerodynamics are far removed from a dodge challenger though. as soon as air rolls above the front bumper it is low-pressure until the cowl, so it wouldn't quite as well for an air intake. the sheer quantity of air required to make power (stock engine ~150hp peak, which requires ~230cfm air) just isn't there in that area at 70mph or whatever you're driving. a scoop there worked for the 924cgt intercooler because that is a different quantity of air required.

what i want to say is that it would probably work for normal power levels, but wouldn't turn out to be worth anything compared to stock. although it would look pretty cool.

try looking into making a manifold similar to the 968 "harmonic resonance" intake. the idea would be to basically force the air with a mini-supercharging effect (this is where the ram-air idea comes into play, inside the manifold) to overfill the cylinders by slightly pressurizing it. the standard US 944 motor is sitting around 90% VE at peak power ((((151 ci*5500rpm)/2 pops per rev) /1728 ci/cfm) = 240cfm/1.5 cfm/hp = 160hp, standard rated output is 143hp...143/160 = ~0.895)

if you can get to 100% or higher VE, which is definitely doable, then you can see noticeable power gains. there are other ways to do that besides intake mani though. cleaning up the intake system (smoothed out vs the ribbed 135* j-bend, square AFM inlet..etc), modding headers to keep velocity up but reducing restrictions, etc...before you even touch the engine internals.

nasty9er

thx for explaining the flaw in the ram theory in this app. so you say 230cfm for peak so my question is how is the flow in the nose panel scoop? now this idea is for a 88 942s that has a front bumper like the early 944 although i have a fiberglass bumper that stick out about 2 inch's past nose panal.... what i am getting at is with a blunt nose would that shift the initial pressure close to the nose panel.

Paulyy

are you talking about the euro bumper vs the US. (the US is longer with chunkier rubber then euro)

924/924s have the same bumper the 944 bumper is similar, the rubbers are slightly different.

nasty9er

its the euro bumper from http://www.944hybrids.com/Fiberglass.html but recessed a good bit

944CS

I have a good bit of technical info I will be able to contribute to this thread in the next few weeks with before & after dyno data, showing the benefits of:

Miller MAF conversion on a stock car
Sport camshaft on stock car
ported/polished cylinder head with bigger valves vs. stock

nasty9er

great thats the same set up that i will be working with. cant wait to see what comes out of it more info the better

thx

LP944

Would a custom bend pipe running from the AFM to an LR MAF Trap work with the ducted headlight for an NA? keep in mind of the Miller MAF replacement.

I was hoping that the scoop idea would work because it seemed like it would,, and it would look cool. Might still attempt it in some form, but I still intended to keep the snorkel coming from the airbox to the wheel well

Paulyy

Can't wait for that info.

and yeah that will work, you can make your own maf trap with fiberglass pre-made sheets.