LanceD

where are you going to get two matching top turbos that spin opposite of eachother?

turbos10

Direction of rotation is not really a factor. If it did anything I think it would most likely enhance flow into the secondary turbine due to canceling out the spin at the Y pipe. Highly turbulent spinning air is why a slightly large downpipe tapering to a smaller pipe helps spool time a bit. It allows the air to expand right after the turbo and then gain velocity through the transistion to the smaller pipe as it begins to cool.

Number47

so when is the national meet to make one of these setups?? The winnings from the truck pulls goes to the site right??

johnsjas

Now the next step is to do a flow analysis and try to cut down on turbulent flow.

XLR8R

Yeah - somebody fire up your CFD software!

HOHN

IMO, the spin of the flow as it exits the turbine won't be mitigated effectively by the counter-rotation of the turbos. I'd expect the turbulence to be even worse.

That's why I like AlpineRam's idea of using a divorced runner housing on the primary, plumbing the secondary turbine outlets to a respective runner on the primary inlet. This would be far less turbulent and preserve far more pulse energy than merging the turbine outlet flows to an open plenum primary inlet.

The swirling effect is best mitigated by accelerating the flow. That means that you'd want the secondary outlet to be the largest cross-sectional area in the flow conduit, tapering to the smaller area of the primary inlet runner (assuming the divorced runner configuration).

I only wish I had access to some CFD goodies.

Maybe I'll get to use it in some future job, but not yet.

JMO

crawleroc3

Hi, new member here, actually closet reader for a while now. I have been very interested in doing twins, as long as I can fab them up on the cheap. I read in another thread where Hohn has been working on a spread-sheet. I have been working on my own. From a thermodynamic standpoint, I have wondered why nobody runs a intercooler between first and second stage to lower the intake temp, and the benefit of building a triple. So I have done this in my spreadsheet, and I am now trying to figure out the "effective" airflow in Lbs/min the secondary has to compress. Getting to the P ratio for the secondary is easy, but getting to the effective mass flow is where I could use some help.

So this is my contribution to the group. I think I am ready to get the excel file out here for some constructive criticism, but can't download it. I have spent quite a while at the squirrel turbo site, and the calculations seem to be working, but on paper, when I find a properly sized primary, the secondary is always off to the bottom right of the compressor map for our HX35 sized turbo's. When I looked at much smaller sized compressors in parallel like Hohn mentioned, presto, looks much better.

Thanks

David

Tate

When I did my spreadsheet, I just used the secondary effective mass flow from the primary's divided by the primary PR. So if the primary is flowing 90 lb/min at a PR of 2:1, I used 45 lb/min as the effective secondary mass flow. Now if this is correct or not, I'm not too sure. It usually puts me in the left side of the map for the secondary.

An intercooler would be a good idea, but I think the main reasons would be extra complexity (especially if its air to water), extra money, extra volume to fill, and more room being taken up in the engine bay. Whenever I get to my 12v Ford project, I may look into it. Lots of room in the engine bay of a 79 F-150.