boost handling and turbz selection

[corolla_kid]

(hypothetical) on a 4age engine, 2nd gen bigport, 7rib block, std pistons but with a compression ratio of

A ) 9.3:1,
B ) 8.7:1

theoretically how much boost could this engine handle before caving in? What are the advangtages of changing the pistons (other than the later ones being ceramic coated) to alter the compression than other ways like H/G

[Zak]

I run 10psi on a standard silver top, so I see no reason you could not run about 14psi maybe more depending on your fueling.

[balistic]

..depends on how good the tuner is.

[mattysshop]

the GZE pistons have been proved they are indeed forged.. there is a huge toymods write up on them.. and one of the guys on there that works with metals and stuff has analysed one.. both versions of the GZE late and eary... are forged...

depends what you want.. shitty off boost driving (low compression).. but run big boost to make 200kw.. or.. higher compression very torquey even off boost.. with low boost to make 200kw..

[AmyC]

Whats going to be more reliable ?

[mattysshop]

depends entirely on tune..

i turboed a mates lexus IS200 a while back.. running 6psi.. makes 197rwhp... drives it everyday, goes out cruising every week etc etc..

there is also a guy on toymods that runs 30psi into a 4AGTE.. goes by the name of 30 PSI 4AGTE, and it's a factory motor, factory rods/pistons/bottom end etc.. but rebuilt and machined very well.. again good tuning.. even not turboing a car if the tune is bad it will kill itself..

[corolla_kid]

Thanks for your input guys, i want something steertable that isnt a dog to drive off boost, as it will probably be used almost everday as a daily, only want to run low boost, i wasnt planing to run much more than 8psi, just wondering what it could posibly handle without melting a piston or something, just for that extra kick in the pants is what for really, Also what would be the best idea to do with TVIS, is there some way i can wire a switch to on off or something or can i just leave it be so its still good for off boost, or should i remove the plate altoghether. and put shorter studs in the head - if i do this this would make it a dog off boost - becasue they put it there for a reason?

I think i'll run std compression for now, low boost, then if the time comes i want more, then start messing around with compression ratio's.

[Joel-AE86]

Ditch the TVIS. Having it there is too risky with boost, and it will serve no function anyway. Providing you use a decent size turbo (T25 or similar) boost will come on from 2500 or 3000 anyway.

With what you have stated, and if you want to run a reliable daily setup, I wouldn't push more than 8-9psi. For more boost, you will want to upgrade your bottom end for reliability.

[corolla_kid]

the turbo im lookin at getting is .50 intake housing 54 trim wheel
.63 exh T3/T4, or another but with a 57trim it sound like it should do the job alright from the reserch ive done, yeah i want it to spool up earyish, but again dont want it to run out of puff to much before the powerband drops off

Would there be much of a noticable differnce between the 54&57 - which would be a better choice

[AmyC]

Can you drive around on a engine like not floging it just putting around in 3rd at 4,000rpm max with out it shitting itself till i can afford a good and proper dyno tune ? Just for about 150 - 200km