When I floor it after cruising for a while in the A8 it blasts soot out to the point I can see it behind me for a second. I'm sure it would fail testing if you drive it hard and metered it

 

Boost PSI has ZERO correlation with turbo size, it entirely depends on air flow volume vs pumping resistances. You can flow 1000 CFM in an engine design at atmospheric pressure aka "0" boost, or flow the exact same amount of air through a theoretical engine that is exactly half the size and all efficiency is assumed to be identical at 14.7 psi. Both engines are moving the exact same amount of air, the PSI increase is simply a result of increased resistance due to flow capacity being halved.

You can take an engine that runs on 20 PSI, port match all parts, resonance tune the intake, size match the plenum, mill the heads and unshroud the valves to increase flow and you will see a DECREASE in boost yet massively increased power at much lower IAT since the engine is now more efficient. Power output is mainly determined by CFM, a more effectively designed system and can flow air more easily thus requiring less boost pressure resistance to flow a given amount.

Similarly you can have a massive turbo like a 80mm fail to hit 4 psi trying to pressurize a 30L boat engine. It just isn't flowing any airmass past 1500 cfm.

 

The Mercedes DELA 30 M276 puts out the same amount of boost and the turbos aren't huge there either. The Hurricane is a pretty compact engine for an I6 by design.

My NA cars dumped a lot of soot near redline.

Always good to hear a technical explanation too!

 

Glad it was useful lol!

That's also why extremely powerful NA engines are absolutely insane when given even slight boost. A R8/Hurrican V10 running "mild" boost of around one BAR gets you from 600hp to over 1200 and a 3.1 second 60-120. Or stock internals viper V10s getting 1100 HP easily and up to 3000 with a build for boost.

That's one reason I would rather buy a massive engine without boost vs a turbo one making the same power, the turbo engine is maxed out already since it's using 20 psi from the get go. There is nothing more hilarious than taking a 5.9L 50s designed engine, refining it to 480hp....then forcing 12psi into it for 825.

 

I've gotten 26 psi from my 2018 Civic Si's tiny little turbo (TSP stage 1 tune), so it's possible

 

how many cars do you have?

 

I don't have the 2018 Civic Si anymore. I bought it to replace my 2006 Camry SE I gave to my daughter, found it just wasn't the car for me and sold it a year later and bought my current IS350. I currently have 5 cars...the Camry is my daughters but It's still under my name, I pay for the registration, insurance and maintenance, so technically it's still mine . Two of the 5 are leases (Polestar and Ioniq)

 

I would wait several years before I bought something with this engine I was going to keep for more than 50k miles, knowing Chrysler.

 

yet another reason to not be interested in these new engines, at least for a few years for all the wrinkles to get ironed out