Well as the title says really, except im quite knowledgeable and want a bit of a technical explanation.
Essentially more flow is more power, but so is less heat and more boost (suppose these are directly linked to flow too).
What I would like to know is will a 20g make more power than an 18g or 16g even at the same boost level? After all they all have the same turbine housing

 

The compressor side also has an effect on power capabilities, the larger the compressor wheel the more power you will get for a said boost level.

 

are you talking about a TD05-20G or a TD06-20G ? Also billet or non-billet, the smoother operation of the billet wheel will allow quicker spool up and less heat generation so same as with the larger compressor side you generate more usable air that you can add timing to and make good power.

have a squizz here:
http://forums.nasioc.com/forums/showthread.php?t=578005

Though you've probably seen the compressor maps before I would guess? Comparing the 18g and 20g in that link you can see easily at 7000rpm your in a higher efficiency zone on the 20g so it's still making useful air. On the 18g you have to either reduce the boost or sacrifice timing/AFR to dodge the knock monster but then your leaving the power behind too.

 

Thanks guys, had to cut my first post short due to work there!
For example I have a big 16g, 1.6 bar at 3500rpm until 5500 where it tapers to 1.4 bar.
Running 14.5 degrees timing until 5000 where it ramps up to 17 degrees by the redline 7k.
If I put on a bigger compressor (same 7cm hotside) how would it make more power?
A; More top end boost?
B; More timing?
C: More flow at the same boost, same timing and boost only adjust fueling to suit flow?

I have a billet wheel that is of the same design as my cast wheel (6+6 blades) however it is taller and is also extended tip, would I expect this to either flow more at the same boost level or allow more top end boost? or both?
cheers Boosted

 

the billet wheel should come to life a little sooner and should be able to hold the boost at the same level without the need to taper off at higher RPM's. Going from a 16g wheel to a 20g wheel you should see a big jump in airflow even if you kept the boost level the same so your engine load figures would be higher and this may have a knock on effect to your timing/fuel tables that you'll have to look into.

 

So a 20g at 1.4 bar is flowing more than an 18g at the same boost? Does this only come into effect at higher rpms?

 

for example I had a Gt35R on my previous car at 1.4bar it made 530bhp, so in essence what you say is correct the 20G is flowing more air for said boost hence more power

 

yup - I think 1bar on the 16g is 512cfm, 18g is around 590cfm but on the 20g (looking at a TD06H-20g) will be around 640cfm. GT35r probably in the region of 900-1000CFM i would've thought?

 

Not a great example as the 35r has a massive turbine wheel and housing over a 20g, so the EMP will be a lot lower.
I'm particularly concearned with the TD05 7cm hot side and it's wheel, but with different compressors, will the EMP be less with a bigger wheel?

 

It will only flow if the turbine is clear though surley?

 

I have a TD05 20G with 8cm² hot side and also billet intake wheel, so power should be around or over 400bhp ? On wich engine will this turbo be the most of use ? 2.1 cdb 2.35 cdb or 2.5 cdb ? Going into a P1 with DCCD 6spd.

 

it's a bit of a how long is a piece of string type of question because there are other factors to be considered.

Heads and cams, avcs or none avcs will also play a major part in performance, in essence it's going to depend on spec and intended use as to which set up will meet your requirements.

On the flip side if you're just after numbers and response then the old saying "there's no replacement for displacement" comes to mind.

 

yeh and also if the engine can actually consume the air too, that's why the VF's can have a tendency to choke a WRX if you run the wastegate duty too high low down - airflow produced is just much higher than the engine can eat so it backs up.

 

Mostly weekend use and some 1-2 trackdays a year. (i have a different Scooby for that)
Atm i only have the turbo and now planning to get an engine build to match the turbo.
So no idea of the heads, has to have a v5/6 fitment. To run AVCS on a P1 will be needing Alcatek ecu ?

 

But andy forrest says that the 7cm td05 housing and wheel can flow 440 bhp no worries, and that the exhaust is not a restriction on these turbos.

 

16G not enough anymore?

 

Big 16g remember, almost same size as an 18g.
I like the responce from it, plus I have a billet wheel to go on it, should put it up about and SC38 performance wise.
If I were to change it I'd put on a proper turbo like a holset hy35 for around 450hp 👍😂
So can anyone actually tell me the MAF load increase between say a 16g and a 20g at same boost level?

 

I could do before and after logs, as I should think i'll be running the 20G at similarish boost levels.

 

Good man

 

Remind me nearer the time or I'll forget lol.

 

it will be difficult to compare them back to back - the 16g generally comes on a bit sooner and tails off at high RPM wheras the 20g will keep pushing the air out at higher RPM's too.

Normally I'd expect to see 3.0-3.2 engine load on a 16g (you could push a little more if the clutch was strong) and around 280g/s of air. On a 20g you should be able to push on around the 300g/s mark but the 20g will be providing that amount of air over more RPM's vs what the 16g will be offering.

 

My big 16g holds 1.4 bar to the reline (7000) where my small 16g would struggle to hold 1.2 at those rpm's.