real hp gains from simple intake mod

[94awdcoupe]

today I swapped out intake manifolds so I could get a dual rail mounted to my shaved manifold. then I got this idea. why not port the temporary manifold and if it works I can do the same to my shaved mani. I suspect when you buy porting service for a manifold 90% or better of the gains come from this tweaking. you are in effect shortening the runners and making the plenum larger. I think porting the runners is a complete waste of time. flow gains come from making it easier for air to get into the runners. only going by but dyno. seems to have gained everywhere but really cleaned up power from 6-7500rpm.

this is the evo 1 manifold from my evo 1.

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[Purple_Demon]

Very nice, just taking the rough casting imprefections off will help. In the honda community we do alot of DIY porting, if you can afford to cut the top of the plenum off and port down into the runners you can get even better gains.

Just make sure you have it cleaned thoroughly before installing it, dont want any of those pesky metal shavings in the engine!

 

[romeen]

Just curious, weren't you using a modified Cyclone dual runner IM?

 

[94awdcoupe]

Just curious, weren't you using a modified Cyclone dual runner IM?

my yellow car with 35r uses a cyclone.
I havent run the cyclone on my blue car since the hta 73 install over two years ago.

 

[lowell]

I've only done this on 1G manifolds but it definitely works. (tested on our Mustang dyno)

 

[bastarddsm]

Out of curriosity, what is the runner length, and the plenum volume of that manifold.

 

[alex209]

Looks good ,what gains did you see ..

 

[yukiz]

just wondering, where did you get your carbide bits??

 

[josh408]

just wondering, where did you get your carbide bits??

You can get them on eBay. I got one about 3 weeks ago. It's gets the job done.

 

[94awdcoupe]

I've only done this on 1G manifolds but it definitely works. (tested on our Mustang dyno)

how much did you remove? and what were the gains?

I only removed 1/4 inch and I would estimate the power increase at 21psi went from 425 to ~445. I am very pleased with the results. havent driven enough yet but my initial impression is its spooling up a bit quicker as well. no negatives. just gains everywhere.



i dont know the dimensions of the evo 3 manifold. compared to 1g/2g the runners are about 3 inch shorter.the plenum has less volume. pretty much 65mm round tube like plenum.


I have vast collection of carbide bits. came from e-bay, jc whitney, wholesale tool, and used tools shops.

 

[spawn87]

i looked at the pictures but not sure i understood how the porting was done if anyone can enlighten me i appreciate it since i might do it to my evo3 mani .

 

[94awdcoupe]

only bit really needed is the round one that is on the extension. very important to round the edges after the walls are cut down. I used cardboard as gauges to be sure I was cutting an equal amount off each wall. I use a plastic tube over the long shaft so I could steady it while cutting. keep bit and tube oiled for smoother cutting. an air regulator would make job much easier as well. bit should not be turning fast. the sanding drum was helpful in getting things rounded out but not really necessary. an inspection mirror also needed to see how rounded backside of wall is.

then clean with soap and water, let dry clean with gas, the cleaned a third time with engine spray cleaner with a rag tied to long probe to clean well inside runners.