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

[Edophus]

well the original questions was what is it about the 3s-ge that means you cant/wont turbo it, is it the compression? the answer to which is no, there is nothing to stop you turboing one, your just dealing with a different set of parameters so you'll get a different outcome, as for why you wouldnt well in most cases its simpler and cheaper to start with the 3s-gte version, and just a handfull of cases where you are better of starting with the na 3s-ge.

As for the compression ratio issue itself as i've tried to point out it will affect the maximum boost but it isnt strictly true its a direct relationship between psi and compression ratio as its a relationship affected by the cam timing, compressor efficiency, how effective your charge cooling is, what rpm's the boost is being made at, the weight of the car the engines in, even the gearing. So the results would be variable depending on a bunch of stuff. The rev 3 3s-ge may have a higher comp ratio of 10.3:1 but thats not directly comparable to the 8.5:1 of the rev 3 3s-gte because the na engines cam timing means your losing some pressure out of the cylinders due to later closing of the exhaust valves etc, hence when you calculate the dynamic compression ratio the picture starts to change somewhat, the actual amount of charge that ends up in the cylinder between the two engines is not comparable. The 2zz with its aggressive cams and 11.5:1 comp ratio is a good example of this, they boost well despite there high comp ratio, even 260bhp from the factory with no internal modifications. lol all that assumes you dont blow the headgasket first, which is entierly probable if you boost a rev 2 3s-ge, before you run into detonation problems.

none of that matters as soon as you open up the engine for forged pistons, i'd be more concerned at that point that i have block with decent wall thickness than which particular version of the engine it is.

think i'd prefer the st215 manifold over the acis intake given the option, and with the tvis heads preference would be not to use them and go for a small port head, but i think either the acis manifold or a st162 side feed manifold would be better than the stock tvis one.

This post has been edited by Edophus: Jul 20, 2011 - 5:42 AM