Compounding vs Twin

[jaluhn83]

Why would a HY flow more than an HX? From what I've see it's the same compressor but a smaller turbine and housing. So I'd expect it to be better for a lower flow and quick spool time, but not make as much on the top end and probably be pretty restrictive on the exhaust side at high flow.

Why did they use this unit on the automatic 24 vlvs and the HX on the manual?

 

[FordGuy100]

The compressor wheel is more efficient. Flows something like 5-10% better

*Edit* of course now I cant find the source of this info, just a bunch of forum jockies talking



Or find yourself some non VGT HE351 turbo's off of 5.9 common rail cummins. 9cm housings and flow much better than a HY35 or HX35 (same exhaust housing size as a HY)

 

[jaluhn83]

Huh? It's the same compressor as the later hx. 7 blades & same diameter. I guess the earlier 8 blade hx might be less efficient than the 7 blade and hy, but I've also seen that it spools better and flows better low end.

Don't forget too that it's more than just flow at one rpm - really you need turbo maps to do it right. Course they're not exactly easy to find unfortunetly.

 

[FordGuy100]

Huh? It's the same compressor as the later hx. 7 blades & same diameter. I guess the earlier 8 blade hx might be less efficient than the 7 blade and hy, but I've also seen that it spools better and flows better low end.

Don't forget too that it's more than just flow at one rpm - really you need turbo maps to do it right. Course they're not exactly easy to find unfortunetly.

Thats what it looks like. Cant trust forum jockies . That is right though, the 7 blade flows more than the 8 blade. Seems most like the HX just because of EGT reduction from a bigger exhaust housing. If your running twins, I would pick it over the HX.

 

[justinray]

I'm not sure it would matter if the two turbo's would need to be an exact duplicate setup, etc. The backpressure differences are lottle to none, and would make no difference, look at the difference in the Y-pipe, and look at the old gas burner trucks running a turbo on only one bank, it doesn't effect things THAT much.

 

[79jasper]

Might also be worth looking into a variable vane turbo (late model PSD / Cummins) and fitting that and some sort of a custom control system. I'd bet you could get similar results and much more flexibility, just have to do some research.

I second that. You're practically getting two turbos in one. A big one and a smaller one. I believe some duramax's had them also.

 

[tanman_2006]

I second that. You're practically getting two turbos in one. A big one and a smaller one. I believe some duramax's had them also.

04.5 and newer Dmax has vvt turbo. Fleece makes a good controller.

 

[79jasper]

04.5 and newer Dmax has vvt turbo. Fleece makes a good controller.

Yep. I've looked into those. Pretty good price too.

 

[Hyde]

You can do either, and if you want to just to say you did, cool. But the same performance could be had out of a properly sized single. In the "just to say I did" category, my buddys old 6.2

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[88 Ford]

There is some positives of twins versus a single. They do spool slightly quicker and also can make more power than a single due to the fact that you can use two big compressors and a smaller turbine side. Granted there are always exceptions to the rule...

 

[Hyde]

There is some positives of twins versus a single. They do spool slightly quicker and also can make more power than a single due to the fact that you can use two big compressors and a smaller turbine side. Granted there are always exceptions to the rule...

In high performance applications yes, compounds can have an advantage, I know a dozen people that run compounds, I know a lot that run singles. From 400-1200hp trucks, highest single being just over 800 on a single on fuel. Being as I dont see a lot of high performance around here, should probably focus on making the most of a single. No offense, compounds are cool, but not needed in this stage of our game.

 

[88 Ford]

I define understand your stance. A single does work for most people for sure. I would say the biggest advantage of compounds over a single other than higher boost, is much lower egts. But again it just all depends what a person wants from there system...