Port Volume Reduction.

[Duk]

Has anybody ever successfully reduced the port volume/cross sectional area of the inlet ports in an engine?

Stating the obvious, the inlet ports in the big port 4AG(Z)E heads are absolutely massive for their cylinder volume and valve cross sectional area. At the head flange, the ports measure 1531mm square.
2 x 31mm inlet valves have a CSA of 1510mm square.

On another forum I'm a member of, there is a (crotchety old) bloke who has been building (Alfa Romeo) engines for ages. He claims, and backs up with engine dyno data, to be able to get 100hp/litre (at sane engine speeds with cams that he describes as streetable) from 2 valve per cylinder, Alfa 3litre V6 engines, with inlet runners no bigger than 39mm (1195mm square) in diameter, using modified original 44mm (1520mm square) inlet valves.

http://mototuneusa.com/homework.htm talks about filling ports with epoxy and reducing the choke point of the port down to 65% of the valve diameter (not CSA).

[Billzilla]

If the ports in the big port head are too large then just use the small port.
Also give Devcon a try for shrinking port sizes.

[Duk]

If the ports in the big port head are too large then just use the small port.
Also give Devcon a try for shrinking port sizes.

But are the small ports the right volume/cross sectional area?
Besides, I only have a big port .

[amichie]

I've tried fitting chokes/venturis/reducers or whatever you want to call them in the runners and managed to move the torque peak down the rpm range. The intake runners on my 7M were about 43mm in diameter and I fitted 36mm chokes.

[Duk]

I've tried fitting chokes/venturis/reducers or whatever you want to call them in the runners and managed to move the torque peak down the rpm range. The intake runners on my 7M were about 43mm in diameter and I fitted 36mm chokes.

Where abouts did you fit these 'chokes'? More often than not, 'chokes' refer to venturi's in carbies. The 'choke point' mentioned in the mototune articles refers to the smallest point just before the inlet valve.

[Casey-G]

run more boost

[Duk]

run more boost

I run plenty

[Casey-G]

can never run enough haha


The motors were always made to rev, formula atlantic series used the bigport head, even with turbos attached there is simply just not enough capacity to make it a low end baller engine.

[Duk]

can never run enough haha


The motors were always made to rev, formula atlantic series used the bigport head, even with turbos attached there is simply just not enough capacity to make it a low end baller engine.

"Assumptions are the mother of all fuck ups"

Thanks for your input, but simply quoting 'Formula Atlantic' doesn't give any real facts.
Read http://mototuneusa.com/the_2007_superbike.htm, you can see how much 'material' he could add to the high(!) revving motor bike engine's port without reducing the ports flow.

[JP]

Duk,

Send TK a PM over at Performance Forums, I'm sure he's filled ports in heads in the past. He's also in SA.
.
http://www.performanceforums.com/for...php?t=67252137

[Casey-G]

I just dont see any point in reducing port volumes. and i didnt quote "formula atalantic" i mearly stated a fact.

Devcon is just likley to fail IMO its just not worth it.
another thing to remember is its not a "motorbike engine" strokes are different length ect..


I was only highlighting the fact that if your going for more power/ higher flow / what ever it may be with these heads you could fuck around with port volumes as much as you want, but the research has been done, and what it all it really comes down to is the 20v blacktop is supirior to all the other 4a series heads. If your chasing the big numbers you cant go past it.

[Twisty92]

I was reading about this last night....someone had done this to a toyota starlet with a 4afe i think, its more reshaping to for some reason i can't remember like for inertia or something :/ i think this is better for N/a motors though? i might be wrong

[Duk]

I just dont see any point in reducing port volumes. and i didnt quote "formula atalantic" i mearly stated a fact.

But you didn't state a fact, you used Fomula Atlantic as a referance. There was no technical information about Formula Atlantic spec heads in your post. How do you know that they didn't reduce the port volumes?

Please re-read my 1st post where I said that other people have achieved 100hp/litre (NA) form ports that are no bigger than 39mm/1195mm square in CSA. A CSA that is significantly smaller than the big port heads.

Devcon is just likley to fail IMO its just not worth it.
another thing to remember is its not a "motorbike engine" strokes are different length ect..

Just as likely to fail as what?
I know it's not a motor bike engine. It's a twin charged road car engine, and any improvement in ALL area's of the engines torque curve is what I'm after.

[the_random_hero]

Your engine is boosted, I would be much more inclined to get more flow (rather than speed) as you already have something already pushing the air in.

[Billzilla]

But are the small ports the right volume/cross sectional area?
Besides, I only have a big port .

Depends on what you're trying to do, with regard to them being the right size. But there's a better chance they'll be right than a big port.
It'll be easier & smarter to find a small port head rather than modify a big port to have smaller ports.