Yessir
Are you talking about the compressor side? Why would you want the 55 to outflow the 42s? The 55 is the secondary, it is being fed by the 42s. If it was able to outflow them, they would just be a restriction.
Anybody else have any insight into this setup?
I don't see how there is enough spread between turbine flow. 2 week work binge has my mind mush too though.
Makes for a nice layout.
IIRC, without looking at the maps, two GT4202's are around 190 lb/min. GT5541 was around 170-180 lb/min. Hardly any compounding. I'd imagine the two GT4202's would outflow the GT55 a bit on the turbine side of things. I'd be curious how it works, if its any better than running a single 55 or twin 42's alone.
Agree with all. I am curious as well. I don't see how it could be better than if he ran either stage alone. The 42's have a very restrictive muffler behind them in the gt55 turbine, and the gt55 will be recieving cooled expanded exhaust gases.
What is really strang to me is how will the gt55 e able to do anything at all? As far as I can tell he is asking the gt55 to perform high pressure boost while receiving low pressure exhaust. even if the turbo's were sized normailly for compounding how can you expect the low pressure side of the exhaust to produce such a high overall PR?
My guess is the set won't last long and will be replaced by a more conventional set, but if I am wrong, cool. We will get to learn something new.
I think it would depend on the turbine wheel profile used as well. Does Garrett make a high pressure turbine like Borg's 83/74 wheel? I'm just kinda thinking out loud here.
I think any turbine that can receive 50 psi and power the compressor to put out 100 psi would be quite revolutionary.
Im not saying it will or wont work but we normally gate around the secondary in a "normal" set of compounds. Who is to say without a little more knowledge on the turnbine/housings that there wont be enough heat/flow to push the GT55 hard enough. I see a lot of guys running a PR on the secondary that isnt all that high, so it may work by that line of thinking. Push the Primaries hard and leave to rest to the secondary(gt55)??? Just kind of thinking out loud
I was actually reffering to the 4202's having a wheel similair to the 83/74 from Borg.
Im not saying it will or wont work but we normally gate around the secondary in a "normal" set of compounds. Who is to say without a little more knowledge on the turnbine/housings that there wont be enough heat/flow to push the GT55 hard enough. I see a lot of guys running a PR on the secondary that isnt all that high, so it may work by that line of thinking. Push the Primaries hard and leave to rest to the secondary(gt55)??? Just kind of thinking out loud
Edit: im curious how well the gt42s "push" air through the GT55 if they lite faster(which id think they would)
You're assuming that 80 psi drive pressure into one charger is needed for 80 psi out of that same charger. Look at it in terms of pressure ratios. My twins generally run at less than a 2:1 PR on the secondary, be around 3.5-4:1 on the primary. So the 42's will be using the hotter, higher pressure exhaust to do most of the work building that pressure ratio. The GT55 gets the cooler, lower energy exhaust to produce the much lower 1.8:1 (hypothetical numbers) PR. This makes great sense to me. Put the energy to what needs it the most, the primaries.
Its the flow rates that cock it all up. The smallest housing Garrett lists for the GT42 is around 37 lbs/min. Largest is 44 lbs/min on the big housing. GT55 is 60 and 68, respectively. So best case scenario, the 42s still outflow the GT55 by 6 lbs/min, potentially as large as 28 lbs/min.
Based on the level and quality of fabrication shown in the pictures, something tells me that he knows what he's doing.