Turbo BS Thread

So like...it just loses pressure, or what? Idk what that means...
VE drops? More exhaust stuck in the next combustion stroke?

 

Back pressure rises, VE drops. More pressure doesn't directly mean more power. The scale isn't 1:1 at least. An appropriately sized turbo may make 8psi and 285hp (example nums), a too small turbo may also hit that number but at 11psi but also dramatically increase the potential for knock because of the exhaust restriction and at a certain point you just can't flow more exhaust and it planes off at that higher RPM where the exhaust flow is key. I think the issue with turbo sizing is everybody focuses on the compressor side. But in a lot of cases you won't find restrictions there You're going to find them on the exhaust side first.

 

Nice. Makes sense, hard to quantify from provided manufacturer intel. Seems to be more of a trial and error thing here - so will definitely heed yours and Jon's advice. Thx

 

So with that in mind, potentially the G2 G30-725 could do with a 0.83 housing instead of Jon's recommendation of 1.06 (1.01) on his Gt3076r since they flow better? Or still go towards the larger?

 

At minimum a G30 with .83. If you are chasing high hp/drag race only stuff then do a G35 with 1.21 housing.

 

You already know which one, I still go g30-770 with the .9 housing

 

Fwiw I'll probably move to a gtx3576. Only because it will drop into the Tial housings i have. Probably the .82. Btw the Garrett housings are heavy! The Tial are thinner stainless.

 

@treyus30, how much power do you want to make now and and how likely is it that you're going to build the engine later? If you do, what will the power target be then? The turbo will have to be a compromise on one of them if the two goals are far apart.

Yes, both, largely from high exhaust pressure causing mixture dilution on the next intake stroke. One of the big advances in turbocharging and related controls is being able to get the turbine drive pressure down to a 1:1 ratio with boost so it acts more like an NA engine. In years and decades past it was common to see drive pressure 2.0-2.5x the boost pressure even on pretty high performance engines. The ones that got it a lot lower had horrendous boost thresholds.