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The gloves are now off
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Not to steal this thread too. :D But, why the hell did Mitsu make the plenium block the rear plugs!!?? They could have made a more efficient one that didn't block them!!
 

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GCtech Motorsports
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1,666 Posts
Our intake manifold is very restrictive for air flow, since is rough in the inside it does not allow good air flow , now it gets better since the design is what is called ''Non-Simetrical'' does not allow even air flow to each cylinders.
That one of the main reasons I re-design my manifold since for high horse power applications it becomes very restrictive....

Later
Gilbert
GtConcepts
 

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The Wizard Of Aaahhhhh's
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1,596 Posts
Our upper intake plenums are probably designed the way they are for a reason. Since our engines have a port fuel injection system and the long runners are seperate between the intake manifold and the intake valve, this allowed Mitsu to attemp some intake tuning.

During the engineering of our engines, Mitsu could change the length of the runners to move the power boost up and down in the RPM range of the engine, perhaps to fill a little "hole" in the power band, or to add a little more low end torque. They found a length that worked best, and went with that design.

This method is called sonic tuning and is very difficult to do. Mostly just the high end racers do it, where every ounce of horse power counts. A tuned intake and exhaust on a race engine can get better than 100% volumetric effeciency over a narrow portion of it's power band if it's done right. Kinda like a natural supercharging...you get more mixture in the cylinder than you could with engine vacuum.

Something to spaz out on when you get bored. :)


Chris
 

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Big Kid
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2,781 Posts
has any of our members ever had a custom intake made for a3S car? If so who and what were the results?
 

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hands drop, the BS stops
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772 Posts
I'm gonna let u guys in on something some of us have been doing.

ExtrudeHone your intake manifold! You'll find nice results.



-Ryan




(modded to hell VR4 Sold! :( )
 

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Big Kid
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2,781 Posts
I spoke with one member who had his manifold extrudehoned and it didnt make much differance at all.
 

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Badassical Baddage
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6,535 Posts
You'd have to give Brian at GT Pro a call as my memory just can't recall this informatin exactly, but I know that in Japan a different version of the Intake manifold was made. It is a little different shape, directly bolts on, but the flow pattern is different and, if memory serves, it creates a swirl in the air boosting the pressure up a bit and forcing it through...

It was specifically made for the GTO, but I can't rememebr what it is called and it's supposedly very rare...he had one in the shop at one point though!
 

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The Wizard Of Aaahhhhh's
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1,596 Posts
Sonic Tuning

JagdStealth said:
You'd have to give Brian at GT Pro a call as my memory just can't recall this informatin exactly, but I know that in Japan a different version of the Intake manifold was made. It is a little different shape, directly bolts on, but the flow pattern is different and, if memory serves, it creates a swirl in the air boosting the pressure up a bit and forcing it through...

It was specifically made for the GTO, but I can't rememebr what it is called and it's supposedly very rare...he had one in the shop at one point though!
Thats exactly what I was talking about above. That intake that you are descibing looks like Mitsu created a way to scavenge the air entering the cylinder more efficiently than you could with piston action alone.

Chris
 

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Big Kid
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2,781 Posts
WAT WOULD HAPPEN IF YOU JUST BUILT A LARGE OVEL PLENUM ON TOP OF THE INTAKE MANIFOLD LIKE THE OLD RAT ROSTER MANIFOLDS ON THE 426 HEMI ENGINES OR THE 440 MAX WEDGES. WOULD THAT TYPE OF INTAKE WORK FOR DAILY DRIVING. I KNOW THAT IT WOULD HELP TOP END.
 

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Senior Fanatic
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6,011 Posts
TTGTOonSteroids said:
Our intake manifold is very restrictive for air flow
Please explain how you determined this. How did you measure this "restriction"? Thanks.
 

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Big Kid
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jeff you would know if anyone has made a custom after market performance plenum for our cars. pics please
 

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Senior Fanatic
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There is nothing wrong that I know of with our intake plenum or manifold - which one <I>are</I> you guys talking about anyway? There are always, always, always compromises. Shorten the runners or fatten them up and high-flow performance can improve. Lengthen the runners or make them skinnier and low-flow performance can improve. I bit larger storage area near the TB would be nice. Making the insides smoother can't hurt.

I know I sound like a broken record, but all you guys looking for some magic mod to make you go fast are nowhere near the performance levels of the guys running mid to low 11's in the 1/4 mile. I think every one of those cars is using the stock plenum and manifold (maybe extrudehoned). Get your cars to the low/mid 11's like these other fellows did with "relatively" stock cars (at least standard-type mods) and then look for new advantages.

Talk to the speed shops that specialize in our cars about custom manifolds. Talk to Matt Monett at Dynamic Racing. He KNOWs how to go fast. He has PROVEN his skills and ability. (And he uses a stock intake manifold and plenum.)

If your car isn't fast enough for you, first do what Matt and Jack did to their cars and practice. Then try to improve on their stuff. Just my opinion. :)

One other thing. All these "improvements" to the manifold and plenum should be designed to flow more air. Well we (turbo cars) can already do that. We just increase boost (air density). The NA guys only have the option of increasing flow, not pressure.
 

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Life begins @ 30psi
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1,089 Posts
I gained 14 wheel hp after installing my Extrudehone intake manifold ON LOW BOOST! (13psi). Couldnt run more then that because it did a number on the stock 360's. I was @ 100% duty cycle @ 15psi. Thats why I went 450's never dyno'd again after that:(
 

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Fuddle-mental apparatus
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1,067 Posts
Jeff,
I know what you're saying, and this is in no way meant to start any kind of an argument here- but you have to understand that not all of us are looking for a "magical mod" to reach the levels of Matt & Company (in fact us N/A guys are very unlikely to reach anything near that).
What I look for, and am guessing that many others here do too, especially N/A people, are small inexpensive ways to enhance our cars' performance. Along with that it gives us something else to keep us busy working on our cars just for fun.
I don't know what Brainfood had in mind when he asked the question, but I would be interested in knowing if it would make any difference that I could tell just by driving. If so, it may be worth a few hours work on it, if not then i could think about other possible mods to do as busy-work.
So if anyone knows what it would actually do, it would be appreciated if they could post their thoughts. I simply must stay ahead of my cousin's 5.0 GT Stang :)
 

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Senior Fanatic
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6,011 Posts
Rich,

Statements like "I gained 14 hp" are almost useless. At what RPM range was the HP gained? Everywhere? Did HP decrease in any RPM range? No offense but, 14 HP is only 4.6% of of the stock 300 HP. I have heard that dyno measurements are only good (repeatable) in the 5% range.

Still, the Extrudehone process is one that should improve airflow at any air speed (RPM). The smoother plenum and manifold walls, the less pressure loss due to the walls that should be experienced. Whether it is worth the money (what $600 for plenum/manifold?) is another matter. I mean there is no way the Extrudehone process actuall increases the <I>volume</I> of the plenum/manifold, just the wall smoothness; and all that can affect is pressure loss. It seems a better course would be to add WI and up the boost a pint.
 
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