Turbo motor compression

[modnrod]

I love turbos.
A lot.
 

But somehow I've never turbo'd up a Beetle, not sure why now that I think of it.

Anyway, I'm not so much asking for an idea of one particular combo, that would have a thousand answers, I'm asking more about converting a NA engine and what compression/octane changes would be likely.

If I have a NA engine, spec doesn't really matter, that runs nice on RON91 octane, and then go turbo at low boost around 8lbs or so, I'm thinking that no compression ratio change is needed, but up the octane to RON98 for that package and it SHOULD be sweet. Or, still run RON91 but knock off a point or so and take out 4-6 degrees total.
Has anyone just thrown on a turbo on a basic package like this before, for a bit of trial and error?
A little bit of prior fiddling with the ratios and octane changes?

Thanks for any experience.

[BeetleBug]

Take a look here:

[modnrod]

Well, there you go! Thanks man!

So with a 8:1 NA comp + 8lbs pressure = equivalent comp of 12.4:1.
If I'm reading it right?

So then yes, probably, dropping 6 degrees of timing and upping the octane 6-7 points might actually work.
 

[modnrod]

OK, dumb VW question time! 

This guy has posted on here once (Splitdog), but I'm hoping he won't mind me quoting his post from another forum on here.
I would like to thank him for his knowledge-sharing, because his set-up is very close to what I had planned, only mine will be milder.



So, why does it seem that most of the turbo ACVW builds use turbos that would seem to be much bigger than ideal if using compressor maps to choose a turbo?
Is it that most guys are happy to have a bit of lag to get more top end, or because most are weekend cars where it doesn't matter?
Is there something magical about a flat 4 exhaust speed/volume that suspends the usual spooling times? 

My pick of turbo based on a stock 1584cc TP blow-through WAS going to be a GT1548 or possibly a GT2052 based on compressor maps and daily driving.
It LOOKS to be a solid pick, but.........

Any more experience others can share?
Thank you all again.
Dave

[Chip]

Take a look here:

Interesting to see how the multiplier changes the higher your starting compression is. I wonder why it's not consistent. I've always been of the mindset that higher compression gives a nice snappiness when off boost. But it looks like it definitely comes at a cost. Very interesting...

[Joel Mohr]

Here's our 1600 kit....stock 1600 makes 160 TQ, 120 HP...T25 with .48 exhaust housing, .42 compressor. I just built a 1672 (65x90.5) for my Puma. T 28, .64 exhaust housing, with a Web 218, 7.9 to 1, 40 x 35.5 heads ported by Clyde Berg. Made 200 TQ, 190 HP at 11psi...91 pump gas...I think the chart is misleading...Dynamic pressure is completely different...

[modnrod]

Gday Joel, how's everything going?
I was going to ask directly for a few details, but I didn't want to seem rude by then building my own!
It's your fault I'm even thinking about it! Haha! I need mine as stock-looking as possible, so I'm thinking blow-through via the hot-air tube to a sealed air filter housing, it's getting harder and harder to have fun nowadays..........  

A really good local (freight is really harsh to me here) option is an ex-1JZ-GTE Hitachi CT12a at 6-8lbs, comp 35/54mm exh 42/52mm stock and they spool up with a small puff, then maybe after testing build another with T3 "40" or "45" trim comp wheels into machined housings and go 10lbs max. End price fully rebuilt even without freight is less than 1/2 a new GT. Heaps of ex-Japan import turbos down here to pick from.

Thanks for your details Joel, shows me I'm looking at the right sizes.
Have a nice Christmas man.
Dave