porting s/t 20v 4age chamber?

[mattysshop]

morning, toying with the idea of a s/t 20v turbo.. stock internals.. not a great deal of boost (under 10psi for sure)

the chambers pictured below (thanks to bill, from a previous thread)

blacktop to the left, 16v (unsure small/bigport) middle, and smallport right..



would it be silly to clean up the edges right round the s/t chamber to shape it more to the b/t head.. i know this will increase the cc's but even if not to port it right out, just to smooth them out.. surely a sharp edge like that isn't good for warning off pre-ignition..

OR.. i should just try and source a b/t head? lol.. (i think everyone will say this!)

[Ben Wilson]

With a decent ECU, you should be OK with a standard head and low boost.

[mattysshop]

i realise that, but if i try and remove some of the floors in the s/t head it might be better off.. plus increase in chamber volume would slightly decrease the CR..

i know lots of people have run 8-10psi on a stock silvertop, i'm just trying to increase the reliability at said boost..

i'll be running an adaptronic, and probly 440cc, 3SGTE injectors

[Sam_Q]

I think the squish ares in the silvertop chambers are a good thing and me personally would prefer lower boost than lose those. Don't want to just fit 4agze pistons? As matty said stock internals are fine providing the tune is right

[mattysshop]

fair enough ill see how we go.. i was kinda waiting for you to get into here..

i would like to keep compression there for good off boost response.. it's just a little streeter.. nothing crazy.. prolly run a TF035, or TD04L..

[Sam_Q]

install acl (mahle/ross?) pistons despite their figures they give about 10:1 comp, best of both worlds if you ask me

[mattysshop]

see that costs money.. lol.. if i melt a piston... then i'll put some slugs in her and run 18psi.. he he he..

c56..... meh she'll be right.....

[Sam_Q]

see that costs money..

so do broken engines, sounds like a fun experiment

[The Last Streetfighter]

With the Adaptronic, a good tune, good fuel, good intercooling 6-8 PSI should be quite reliable.
IMHO, if you clean up the head/ports you'll lost a beesdick of compression but may allow 8-10 PSI quite OK.
With a VF35 will you ever be off boost?
Oh, and technically porting out the head will not increase the cc's because it is not swept volume. It only reduces the clearance volume efficiency of the engine.

[mattysshop]

it will increase the cc's of the head trev think the silver tops are around the 38cc mark??

and it was a TF035 - gt forester turbo.. still capable of 220+hp on a wittew 4efte.. and reasonably responsive.. so on a hi-comp 1.6... well.... should be interesting to say the least..

[The Last Streetfighter]

Yes, VF - TF was a typo. I just meant those little TFs would be quite responsive.
Yes it will increase CCs in the head. But it just looked like you meant it would increase the ccs of the engine i.e. displacement. Which it won't.

[af300e]

Have a look on Meridian Motorsport's website. They have built a high comp super charged 2zz exige.
11.5:1, 6 or so psi, 190rwkw and a dyno plot as flat as Rwandan comedy.

High comp/low boost for the win. Use a computer with good resolution and get someone who knows their shit to tune it.