Couple quick questions that I couldn't find anywhere else.

When choosing twin turbos, do I split the lbs/min in half that both turbos will be running with the engine?

e.g. (60lbs/min = 30lbs/min per turbo = find 30lbs on the compressor map?)


The other question is how do I figure out if I will be past the surge line at lower lbs/min? Is there an equation to figure this out?

Thank in advance.

 

1) Yes, exactly.

2)There isn't really an equation for a specific combo to figure it out beyond knowing the lb/min and compressor PR at various points, but if you have a good idea of how much air your engine will flow (roughly translating into how much power it will make) at certain boost levels, you can probably plot on the map pretty close as to if and where you would fall into surge.
In the real world you'd typically fall into the surge area if the compressor side is too big, and if the turbine side is also too small. I don't think you'd have much of a problem with this on a 5.0-5.7l engine unless you were to completely mismatch the turbos with the engine.
Are you looking to do twins? What do you have in mind for a power goal?

 

Dang, I don't know how I let this one slip me by. Thanks for replying.

I'm looking for 720-750 on a forged 383. I believe that two T04E 60" turbos would be sufficient enough. If I'm reading the compressor map correctly, then this should be just fine as well as pretty efficient.

Am I reading the compressor map effectively?

I will be running 2.02 PR and 35-37 lbs each turbo. I figured this from running a 75% efficiency turbo, 14.4 atmospheric pressure (adjusted for where I live, 600ft above), and a 70% intercooler efficiency.

I just don't want to purchase something that I'm not able to use. From everything I've read, this seams to be ok, but I wanted to see if I could get a confirmation.

 

The compressor map:

 

Bump.

Just need to make sure that I'm reading the comp map correctly.

 

I’m not positive what you’re asking, but that spot is about 36lbs/min @ a PR of 2.1… As twins on a 350 at about 85% VE that’s about 5750 rpm and 780hp. Real world somewhat less because I doubt you won’t loose some pressure/flow through ducting, IC…

 

I'm just trying to figure out if those turbos are going to be properly matched to a forged 383 cid or if I need to start looking around for more. I was afraid that I was reading the map wrong and choosing a turbo that would not spool up at a decent time.

 

the map has nothing to do with spool time.