Why can't we turbocharge a 3s-ge?, Compression ratio related Options

[dudeofchaos]

I know that the 3s-ge engine has a higher compression ratio than the 3s-gte (which I guess means that the pistons' head are thiner right?), but what does it change so that we can't (or shall not) turbocharge the 3s-ge?
Is it because it would (I don't know) be too much compressed exhaust gases for the turbo to hold?

BTW: what does the last number in the compression ratio mean? (Like in 10:3:1)

This post has been edited by dudeofchaos: Jun 26, 2011 - 10:51 PM

[ST205WRC]

so basically stay with the red top for the 6th gen. now how much different are the valves in the black top vs the red top? could we use the 6sp black top valves in the red top as an upgrade? are the other demensions of the valves the same other then the diameter of the valve itself? i think it would be a worthwile upgrade stronger, lighter and bigger.

[Edophus]

the blacktop intake valves are 35mm vs 34.5mm for the redtop (all previous 3s engines are 33.5mm), i'll need to check the exhaust i cant remember off the top of my head. The blacktop valves are titanium and apparently half the weight of redtop valves. The difference between the redtop/blacktop are more a combination of slightly larger valves, and slightly more compression, the difference in power isnt great but the blacktop is setup to make its power slightly higher up the revs, hence more compression and bigger lighter valves, peak power is 600rpm higher, unlikely to gain much in the way of power from using a blacktop but the end product should show better results than the power difference would suggest. In either case both blacktop/redtop respond very well to an aftermarket ecu so its always the best place to put your money first imo.

There is nothing to stop you shoving a blacktop head on a redtop engine, the head casting is the same, except for the water ways, and thats easy to account for with a small blanking plate, and just drop the exhaust vvti controller for a solid cam gear. Although as usual you'd have to weight that up against just having some headwork done to the redtop head.

Ultimatly there is little to gain from starting with a blacktop, or even using the blacktop at any point, it'll be better, but by how much and how much extra pain did you need to go through lol. I'm not going any further at the moment with mine as i'm satisfied its going to work, but really want to build it for boost, so its sitting ready to be torn down again when i can afford some nice forged internals for it. I had it in and running to the point i could drive around, but had issues with the fueling and the throttle body, so no power over 3000rpm, both of which i'm sure some more time/money investment would solve, but as i want to run aftermarket ecu in the long term they wont be a problem at that point.

the setup i used was

blacktop head and block, complete with blacktop water ways and head gasket
redtop oilpickup, windage tray and sump.
redtop inlet manifold and throttle body
redtop tensioner and idler pulley

I was able to retain the blacktop water ways as i had the room for the pipes, if you have to convert to redtop water ways then you also need to change the blacktop head gasket for a redtop, as the gasket alters the water flow through the block. Really you end up using so many redtop parts, it will probably cost you twice as much as just doing a redtop, and thats a lot of extra cash that could have been spent upgrading the redtop, i managed to do mine for about the same cost as a redtop, simply because i was lucky and paid peanuts for the blacktop, but i've never seen another that cheap since, they are all two and half times the price i paid for mine, so it kind of made sense to have a go, but i wouldnt recomend it!. If your going beams with the intent of turbocharging, then its reallly hard to see past a greytop beams, the only difference between it and a redtop is the greytop exhaust manifold has pre cats built in, but your chucking it away anyway, so doesnt matter.

This post has been edited by Edophus: Aug 11, 2011 - 10:09 AM