i ported from 6m to a 7 cm, manifold and turbo

[thilaksharma]

I would like to see the 18g compressor mated to the td05h turbine wheel in an 8cm^2 housing. That would be a nice combination. It may flow the same or better at a lower pressure ratio (before turbine / after turbine = PR) than a td06sl2 7cm^2 combination. Lower PR is lower backpressure

But negating backpressure is best done with twinscroll, to which mitsubishi and all the other auto manufacturers have migrated.

so in other words you mean that a t3 .82 twin scroll would have less backpressure compared to a single entry ? would just to know your theory on it

 

[habitatguy187]

Man I want one of these for my bastard 20g.

 

[turbo addict]

so in other words you mean that a t3 .82 twin scroll would have less backpressure compared to a single entry ? would just to know your theory on it

no. a divided will have more backpressure than an open housing because they dont count the material in the divider. This is only a fraction more backpressure though. But you can usually get away with a bigger or next size up in the housings and have the spool characteristics of a smaller housing. So when using the larger housing that is divided you spool as fast as a smaller housing and have flow similar to the larger housing.

Hope that makes sence, its early for me.

 

[dsm-onster]

Well kind of. . .

Lets look at this scenario. An 18cm^2 twinscroll holset turbine housing has a critical area very close to a .63 a/r garrett housing. Assuming the turbine wheel is the same, each pulse sees the same flow as a .63 a/r housing and is presented with presure pushing it back equal to what a .63 a/r housing would do. And thus presenting to the turbine wheel the same work potential per pulse.

With the above in mind. . .

Factor 1: Each volute sees half the total flow (only from 1 & 4 or 2 & 3). It will take twice as many rpms to see the same flow backup to a certain backpressure.

Factor 2: NONE of that pressure ever bleeds into the next cylinder in the firing order, because overlap events are isolated from one another. Also, you can get closer to the full work potential per pulse. This increases spool speed even though each pulse is seeing the same critical area that .63 a/r presents. More of the potential work is utilized.

Outcome: Higher total VE and thus flow because the backpressure never impedes during overlap. And, higher total VE and thus flow because it takes twice as many rpms for backpressure to reach a certain point as pressure against the exhaust stroke.

You can get away with smaller individual volutes to spool quite a bit faster than a larger open scroll and yet flow just as much because of the the above two outcomes.