DTN

I thought it was short runners/big plenum for naturally aspirated engines and long runners/small plenum for forced induction engines.

I believe the mitsubishi Eclipse IM would suit boosted cars well for this reason. It's intake manifold bolts up to our head with minor modification to the holes and the vacuum lines. It's TB is in the same spot. It's plenum is the size of my fist. It has runners that go out from there to all the cylindars.

01tibby

opposite dude. with long runners you get the scavageing effect. air hits the valves when they close, and creates a void that allows the following air to rush into the cylinder more quickly. with a pressurized intake charge it will get in there just as fast anyway.

StrikeEagle

READ CORKY BELL!! I've done tons of research on this subject (both for my car and the student formula racing), and it's best summarized in his book. Please stop confusing people - long runners are for NA, short runners are for FI. End of story.

AdamW

<div class='quotetop'>QUOTE (DTN @ Apr 18 2008, 06:35 PM) <{POST_SNAPBACK}></div><div class='quotemain'>I believe the mitsubishi Eclipse IM would suit boosted cars well for this reason. It's intake manifold bolts up to our head with minor modification to the holes and the vacuum lines. It's TB is in the same spot. It's plenum is the size of my fist. It has runners that go out from there to all the cylindars.</div>

?
1g and 2g dsm intake manifolds are completely opposite ours. The TB is NOT in the same spot, in fact its on the other side of the engine bay entirely. I dunno if the IM bolts-up directly. Are you talking about the newer mitsu's? If so, they are not turbo, they are NA like the tib, so why would we convert to their IM if it's designed for a NA application?

I got lost by your post there, could you help me understand what you were talking about?

Ericy321

Someone said the neon (420A) manifold bolts up to ours. As for the earlier DSMs with turbo, they will not work at all.

radu_rd2

^^Strike: Here is an excerpt from Corky Bell:

"[...] higher speed engines will tend toward shorter intake runners. Low-speed and mid-range torque generally shows gains from longer runners. Turbo applications will generally find best results with long runners, which provide a broad, flat torque curve at low speeds, while the turbo keeps the top end strong."

daoust

the runner length

they must be tuned with the cam duration and the rpm you whant the power , also there is harmonic reflective wave . first harmonic is usually never used but it is the one who give the most torque , second harmonic and third are the most popular , they give a good torque and hp ratio .the first harmonic is the longest , the second is shorter , and the third is shorter than the second . . . the fourth harmonic start to give less torque and the fifth is even worst . . .

the plenum

the smaller you can go will give more torque but less power . Don t go lower than the 1/4 of you engine cc , so for a 2 liter , don t go lower than 500 cc
the bigger you can go will give more hp less torque . Don t go higher than the maximum cc of your engine , so for a 2 liter , don t go higher than 2 liter plenum

So it is not true a n/a engine need long runner , it s all a mather of tuning with cam duration , the rpm you whant the power and other variable .

mcorrales

Thank you for your comments... I see a lot of knowledge and creativity in this forum!!!

mcorrales

Update before the welding...

optimoprime

someone please start a service making IM. i dont know enough about P&P to do it on my own and even if i did i dont have any way to weld ALUM.