I thought I would answer PM's to me via a a public post, as many others might be interested
First for the people that don’t know much about turbo charging....
Blow through: turbocharger is before the carb
Draw through: carb before the turbocharger
I believe the majority of the turbo charging you have seen on this site (Pristic and bens turbos) use a blow through turbo charging arrangement... There are pros and cons for each I will explain.....
Draw through is easiest, to put it simply. You don't really need to do anything special to the carb, just make sure it and the rest of the fuel system can supply your increased air/fuel demands (addition reference to the power valve, larger fuel inlet control needles, nothing huge). Oh and u don’t have a BOV.
In plain English: as far as the carb is concerned, when your turbo is all spooled up it's just hooked up to a big breathing engine.
The cons to a draw through system are that you can't use intercooling however the fuel aids to chill the air on a draw through, and some throttle response issues may arise because of the longer intake tracts. They also can be difficult during cold start ups because of the intake tract length (some setups have special diverter valves around the turbo system to help with this). You also need to make sure there is a special carbon face seal on the compressor so oil won't be sucked out of it into the intake tract under vacuum (evidently this isn't normally standard equipment, so you would have to request it when you order a turbo).
With a blow through system, you can use an intercooler, and they tend to have better response (and better cold startups) certainly recommended if you plan to run high boost which I don’t.
You have to modify a carb quite a bit for a blow through setup (unless you use a metro turbo carb). First, you'll need a pressure box/hat for the carb to make sure the float bowl is seeing the same pressure as the intake area. It will also take a little more work to get the carb jetted and set up correctly. You also need to replace certain parts (such as brass or plastic floats) with special nitrophyl type units that won't collapse under pressure. You could also run a BOV with this type of setup which you cannot on a draw through.
That being said here are my specs..
The engine the turbo is on in the photos is not the one it will be fitted to.
Block: fresh build .030 over bore (1302cc) rebuilt donk run in NA for 1000km... 8.5:1 com will run about 7PSI boost.
Head is a NEW import avonbar turbo application head 27.5cc (avonbars very own casting)
Turbo is a T25 high flow with M10 trim originally from a Nissan pulsar it is fully reconditioned with carbon seal (very important when running a draw through setup)
Fuel: 45DCOE Webber also fully reconditioned..
Here are some pictures....
Trial fit....
