twin charging / compound turbos

[Akauf587]

been reading up on this and looking at the results several here and else where have had with twin charging and compound turboing a small gas engine.

Something I've been wondering that I cannot find much about, other than some rough flow calculations, is if the twin charge set up can be as efficient as the compound setup. I'm seeing some results but not nearly enough to satisfy my curiosity.

The compound set up is great for getting two turbos working well with great pressure ratios. This got me thinking about whether or not a supercharger could improve response more without sacrificing too much top end. I'll make up to set ups to compare that I've been thinking about.

twin charged set up:
intake > turbo > IC > supercharger > IC > motor

Is it feasible for say an eaton m62 @ 1.6:1 to get a hta82 up to 1.9:1 by 3.5k rpm?

45 psi @ 3.5k with the kind of flow these two paired would generate would feel amazing. selecting a turbo with a nice fat map at this ratio should prove to make good top end power.

Compound set up
intake > hta82 > IC > fp white (hta68) > IC > motor

hta68 can hit 3:1 by 4k rpm so it should bring the hta 82 with it and with any luck (and help if needed) the 68 would move to 2:1 as the 82 reaches about 1.5:1. Possibly 45 psi in combo by 4.5k?

I could link some maps in if anyone desires though at the pressure ratios assumed the compound set up is flowing more and more efficient at high rpm as the supercharger would likely be near 50% efficiency at 8k rpm in this set up.
Its important to consider that pressure is not the same as volume and one of these set ups will make more power with less boost. Back pressure differences are important to consider as well.

anyone care to speculate or share their experience as to which set up sounds most desirable?

things to consider:

Can the twin charged combo out spool the compound by as much as 1k rpm in reality? If not, is it still worth doing as opposed to a compound set up?

How much will the lower efficiency and pressure ration of the super hurt the top end performance of the hta82? Will the hta82 take up the slack of the super as it would a smaller turbo in a compound set up.

How much will the hta82 slow the spool of the hta68 with its added back pressure and inlet restriction?


Its all hard to wrap my head around when air volume, back pressure, and thermal efficiency must be considered to determine the expected performance of these set ups.

 

[RWD4G63]

Centrifugal superchargers work great in a compound configuration. They do well at high RPM.

I can't find it right now, but I used to have a dyno sheet for a small displacement engine that used a turbo and supercharger. It was a pheonominal power curve. Basically instant power, very flat all the way across, and it made about 1000 WHP.

And I know compound prochargers have been done. That set-up set the new record for that class this year.

I'm guessing that engine had a lot of R&D and cash sunk into it. It takes a ton of money to make engines like that reliable. I'd definitely be interested in seeing the setup. Hard to think of a practical application for such a contraption besides bragging rights and highway pulls.

For us RWD guys, an LSX is a simple solution, and something I would consider if going for such crazy figures and needing torque that low in the rpm band.

I can't really see the point of compound centrifugal chargers, as "spool" isn't really anything to worry about. Maybe one has a lower drive ratio?

 

[Black-Out]

I heard he ended up getting rid of it and went back to big turbo and spray I believe.

Car was badass I got to see it in person, great work that guy does.

I can find out the details on that but unless he decided to really change up the pace he's never used spray....he's never needed it for roll racing. Only thing I've seen him do is go from an automatic to a 5speed manual from a non turbo mk4 Supra.....he picked up 70whp just off of the trans swap and acceleration was absurd....he did that on a 6262 back in the day....when he was bringing down around 650whp. the compound set up made way more torque over the entire engine speed range below 5000rpm and a little more torque to red line. The big difference was the way it pulled to redline......like a pitbull on crack chasing a burgler with a steak wrapped around his neck...

William-

 

[99gst_racer]

I can't really see the point of compound centrifugal chargers, as "spool" isn't really anything to worry about. Maybe one has a lower drive ratio?

Right, it wasn't really for spooling. But I'm sure it still yielded airflow sooner, torque sooner, and overall greater peak airflow. 3.972 @ 183.5 in the 1/8th as of August of last year.

 

[99gst_racer]

Here's a couple more to drool over.

Turbo feeding a centrifugal supercharger. No performance details.

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Centrifugal supercharger feeding two turbos. 4.2L engine. Testing incomplete. Kept snapping crankshafts on the dyno at 1800 HP, so they scrapped the project.

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[Black-Out]

^^^^^Drool.....^^^^

 

[spawn87]

If you're a member on dsmtuners, I'd suggest PM'ing a member there with the name of 99gst_racer. He has a compounded setup. I think he's using a 16g and a 60trim. He's putting down some decent numbers at a really good spool time. He can help you out a lot.

gata love those long days