Custom intake manifold discussion, change of plans...lol

teamliviD · Post by **teamliviD** » Sun Jan 28, 2007 1:30 am

thats what I though......but seriously, I would so swap you my full turbo set up for ITB's for my R/T!!

03blackrt · Post by **03blackrt** » Tue Jan 30, 2007 2:43 pm

a little food for thought... i was a little bored today so i crunched a few numbers for an intake to tune the intake pressure pulse. i came up with... [tuned for comp 400 cam intake duration and for peak power at 6850 rpm]

runner length ~ 8.12 inch [from valve face]

runner cross-section area ~ 2.03in^2

the length and area tunes off of the fundamental pressure pulse and optimizes port velocity for maximum efficiency [minimal energy loss].

all_motor_mike · Post by **all_motor_mike** » Tue Jan 30, 2007 9:22 pm

then it sounds like u want a short runner.

03blackrt · Post by **03blackrt** » Tue Jan 30, 2007 11:52 pm

that should be 8.9374 inch

not 8.12

turbodudey · Post by **turbodudey** » Wed Jan 31, 2007 1:36 am

03blackrt wrote:a little food for thought... i was a little bored today so i crunched a few numbers for an intake to tune the intake pressure pulse. i came up with...

I'm curious which method you're using for the running length calcs.

Helmholtz with or w/o volumetric considerations?

Intake ramming factor?

Or perhaps another method I'm not familiar with?

03blackrt · Post by **03blackrt** » Wed Jan 31, 2007 2:52 am

runner length can be simplified by...

L=[(EVCD*(1/2)*a)/(RPM*RV)]-[(IRA/4*Pi)^(1/2)]

where…

L= runner length
EVCD= effective valve closed duration ~ [720degree – (advertised cam intake duration-(~20 degrees)]
a= speed of sound [for simplicity 13543 in/s can be used]
RPM= desired rpm for pressure tuning
RV= reflective value [1= fundamental frequency, 2= first harmonic, 3= second harmonic....]
IRA= intake runner area
Pi= 3.14159265359.... [is it sad that I have memorized pi to 11 decimal places?]

you will have to tune the port velocity with the cross-section area. to get more detailed you will also have to take into account for compression of the air, temp change, speed of sound change, major/minor pressure losses ect….

This equation is just simplified applied theories of fluid dynamics [fundamental physics]. Helmholtz’s Theory takes into account a plenum and ram tube, runner length does not depend upon this. This theory would indicate a ram pipe length of ~9.838 inch and a plenum [aka Helmholtz resonator] volume of 61~73 in^3.

its 2am, so hopefully everything is correct

EDIT: RV... (1/2= first inharmonic, 1/3= second inharmonic...)

neon2ner · Post by **neon2ner** » Wed Jan 31, 2007 5:41 pm

is anyone interested in answering my question or...no? still awaiting a reply.

quicksilvr · Post by **quicksilvr** » Wed Jan 31, 2007 6:00 pm

neon2ner wrote:i notice guys, that all of these designs eliminate the 2 piece design of the stock magnum manifold. i realize that it would probably be more expensive and more of a challenge (as if these ones aren't challenging enough) to reproduce a better manifold while still retaining the 2 piece design of the stocker with the secondaries and all, plus possibly some clearance issues with the even larger plenum...

BUT, what about the people who want to run an aftermarket intake i.e AEM and 60mm TB with their new intake manifold, instead of getting a new intake fabbed up to still be a true cold air intake (given the inlet placement of all these prototypes, an aftermarket intake wouldn't work) or maybe they don't want a short ram. even further, they want to still have their secondaries and somewhat stock look and fitment. i realize that would be hard to make happen, but is it possible? would it be possible to produce a manifold without the secondaries, but locate the intake manifold inlet in the stock position so it could be used with the stock TB or 60MM tb, coupled to an aftermarket intake? in other words, having the throttle body in the stock position?

scott.

To answer your question, making a custom, dual plane manifold with working secondaries would be extremely expensive, and not worth the time or money. Like, more money than your car is worth. So that idea is out of the question.

Now, simply placing the inlet tube (or TB flange, depending on style) in a position and angle that is the same as stock...that's very doable, but it is more hassle and work. Bottom line is, 90% of the people that will buy a custom fabbed intake manifold and actually use the manifold to it's potential don't care if that can still use a particular aftermarket cold air intake. Hence, they're not made to specifically accomodate such intakes.

I'm sure for extra cash and time, AMM could make you one. But honestly, there isn't a real good reason to ditch the great design of the stock Magnum intake for a custom intake unless you're trying to make serious all-motor power with a huge cam and some timing control. Or you just have a bunch of money to spend....

white2000neon · Post by **white2000neon** » Wed Jan 31, 2007 7:40 pm

I'm using a aem cai with my box style.

quicksilvr · Post by **quicksilvr** » Wed Jan 31, 2007 10:07 pm

white2000neon wrote:I'm using a aem cai with my box style.

Cool. See, some are made to work just fine...might take some tweaking...but that's what car guys and girls are all about. Tweaking.

neon2ner · Post by **neon2ner** » Thu Feb 01, 2007 10:06 am

i'd love to see some pics of that manifold if you don't mind.

and yes i realize if people want to make lots of all motor power, they don't really care. however, the flow of the AEM is very good, and that coupled with a better manifold would be a great combination for what i want. and i'm looking for bolt-on power, because i know i won't be keeping this car for a long time and i want to sell it in stock condition. something better will be here in a couple years.

scott.

white2000neon · Post by **white2000neon** » Thu Feb 01, 2007 5:56 pm

check out the thread in picture section labeled white2000neon and r/t wannab photoshoot theres a picture in there im pretty sure.

quicksilvr · Post by **quicksilvr** » Thu Feb 01, 2007 8:00 pm

neon2ner wrote:i'd love to see some pics of that manifold if you don't mind.

and yes i realize if people want to make lots of all motor power, they don't really care. however, the flow of the AEM is very good, and that coupled with a better manifold would be a great combination for what i want. and i'm looking for bolt-on power, because i know i won't be keeping this car for a long time and i want to sell it in stock condition. something better will be here in a couple years.

scott.

I completely understand what you're saying. But you're missing a key point. A custom manifold is absolutely no better for your car than your magnum manifold... if all you are doing to it are bolt ons. A custom manifold would probably feel worse to the butt-o-meter 95% of the time compared to the magnum. Sheetmetal intake mani's just won't do much for a "bolt-on" car. The stock Magnum intake is a great design....you're bolt-on's are not going to max it out. Do every bolt on in the book, and the magnum manifold will still not be a bottleneck.

white2000neon · Post by **white2000neon** » Thu Feb 01, 2007 9:03 pm

quicksilvr wrote:I completely understand what you're saying. But you're missing a key point. A custom manifold is absolutely no better for your car than your magnum manifold... if all you are doing to it are bolt ons. A custom manifold would probably feel worse to the butt-o-meter 95% of the time compared to the magnum. Sheetmetal intake mani's just won't do much for a "bolt-on" car. The stock Magnum intake is a great design....you're bolt-on's are not going to max it out. Do every bolt on in the book, and the magnum manifold will still not be a bottleneck.

True the key advantages to the box style are responsiveness and topend power. i did lose a lot of bottom and mid range with it. When i put the afx r ecu in i got it all back again and maybe some more along with the responsiveness. In 1st gear as low as 2k i can punch it and roast the tires without using the clutch. Amusing and annoying at the sametime. Unless your reving it up high or have a cam and ported head you wont need the box style.

kc2005ptgt · Post by **kc2005ptgt** » Sat Feb 03, 2007 1:44 am

ever gotten a dyno done on your car?? I would love to see your numbers and cruve )hp/tq curve) sorry - back ontopic

MXer · Post by **MXer** » Sat Feb 03, 2007 6:21 am

How do you find the intake runner area in the above calculation? I wanted to crunch the numbers for a Comp 400 and a Comp 200 with at peak HP at 6400 for the Comp 400 and peak HP at 6200 for the Comp 200

neon2ner · Post by **neon2ner** » Sat Feb 03, 2007 9:50 am

i guess i'm going to be looking into a computer and a 60MM TB. too bad howell doesnt make a magnum specific computer. all i see are non-magnum, and everyone seem to be using them on the magnum engine no problem. i figured maybe someone would make a computer for the magnum engine specifically, but i guess not. i digress.

scott.

white2000neon · Post by **white2000neon** » Sat Feb 03, 2007 1:19 pm

kc2002acr wrote:ever gotten a dyno done on your car?? I would love to see your numbers and cruve )hp/tq curve) sorry - back ontopic

No havent gone to the dyno looking to in the next couple of weeks though.

And you can use the afx r ecu on a magnum car its just that it wont control the butterflies in the IM

neon2ner · Post by **neon2ner** » Sat Feb 03, 2007 4:33 pm

it wont control the secondaries at all? or they'll still open at 5000 rpm like stock?

it would be interesting if there was a computer that opened the secondaries at wide open throttle, or at a lower rpm.

white2000neon · Post by **white2000neon** » Sat Feb 03, 2007 4:46 pm

It wont control the secondaries at all. It has been proven that at the stock opening point for the secondaries makes the most power. If you still wanted to fun a magum IM you could always get a window switch and tach adaptor.

neon2ner · Post by **neon2ner** » Sat Feb 03, 2007 10:20 pm

screw that, i'll just stick with bolt ons. plus, i dont wanna send it my computer to be redone. not only that, but ive had bad enough experience with howell that i won't go back again.

anomalous0 · Post by **anomalous0** » Wed Mar 07, 2007 1:46 am

What I would like to see would be a modified magnum intake manifold, with the secondary runners ported out a bit (there's room to add a good 2 mm each and still keep the stock butterflies, they're at a pretty big angle.) But more importantly, one could cut the bottom off of it, and weld some sort of box onto it to expand the plenum volume, and ideally have the inlet in the center facing downward. It would take a longer throttle cable, more than likely, and perhaps you'd have to extend the wires, but it might be pretty neat. No bends for the air to take on it's way in, and when the secondaries opened it would be almost like having ITBs as soon as you hit 4800 RPM, while keeping the midrange smoothness of a stock intake manifold