Recently ive been leaning away from my m90 plans in favor of a compound turbo arrangement...not sure if anyone has tackled this yet on a slant..but i believe its a good candidate for this unique turbo pairing..

Im not talkin twins..or sequential..im talkin compounds...ive got a couple turbos layin around that may spark this whole deal depending on the packaging in reguards to the room i have in a slant six powered geo tracker crawler build..(not much)

Ive run many calculations and spoke with a few facebook engineer/turbo buddies..one which has a tripple turbo 6bt that makes 65psi@1900..the beauty of the compounds is a huge torque bubble that never falls off..and in this case..to take full advantage of a huge powerspread on a engine with a limited rev ceiling..obviously resluts could be made with any t3/t4..or various combos of small twins..(considering a pair of ko3s)..but im different..and like to tinker..and just cant see throwing away 60 hp to drive a m90 @ the boost levels i want to run..

So..with that said..i may pair a single ko3( i have a couple) and a to4b(52mm/.96ar open scroll)..the ko3 flows between 9-12lbs/min @ best efficiancy on its map..and become hair driers much beyond 200hp..the to4b will do about 45lbs/min or 425-450hp..on my 273..my to4 would make boost around 3k and was all in at 3600..a bit laggy for 225"...in the same token..my 1360cc tracker with the ko3 would spike 10lbs at 3k as fast as you could move the old right foot..

Im guessing a ko3 as a secondary(first turbo in exhaust path) would light up around 1800-2k with 225"..t4 would be used in primary..SO..
in order of exhaust flow..it would go ko3 with its factory wg and a 50mm auxilary gate dumping into the to4b hotside with its own 50mm wastegate to controll its speed...thebig units compressor feeds the ko3 and would be aftercooled post second stage.

The ko3 turbine housing would be bypassed once the first 5-7 psi were made and that to4b would come online and handle the rest..up to 20 ish psi in my case..the thermal loads are halved..the drive pressures are lowered..and both units can be efficiant at low pressure ratios..

there are several great examples on yellowbullit and a few others out there..one being a pal of mine with a saturn sky with a gt2871 & gt42(4298?)..800 hp and full boost at 3k holding to 8k..its amazing..somewhat complex..but the results cant be ignored..a 225 making full boost my 2k and holding to 5500 while making enough wind to generate 400whp is truely having your cake and eating it too....

http://www.youtube.com/watch?v=bINtzDBl ... ata_player

http://www.youtube.com/watch?v=aEONH8hU ... ata_player

Not really looking for any guidence in the matter..just sharing something different and thinking outloud to generate open minded discussion. At this point..im well aware of shakers build as well as the "other" fast boosted slants..just thought this may. Open some new doors with a 1960s design....i will be posting as i go..we shall see if this materializes..

Fwiw..i found data on the ko3 turbine and it is just way to small..anything in a .48ar would be better imo

Ummm wow.....
Never even thought of that

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Richard (aka Fingers)

Sounds exciting. It sounds like you are not afraid of the complexity and working until it works... That is the key in this kind of endeavor. Note that 400 WHP has been made with <15 psi, but not with low RPM spool up.

I had not heard of the "small turbo to spool up big turbo, then bypass small turbo to get big flow" idea - nice.

Lou

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Home of Slant6-powered fun machines since 1988

^true story haha..i dont let the "what ifs" stop me..never have..love to put my foot down on new builds..thats the best part! Thanks..our slants are robust enough in my mind to easily handle boost and super low revs..such is the case with roots chargers anyhow..and turbo sizing is always a compromise i dont want to have to make..i may look for a jy t3 in good shape to use for the "firestarter" like a saab or volvo unit..or even a ford .42/.48...basically the lil guy flows whatever the big unit will..(it sees incresed density)..only bottleneck is in the hotside of the lil guy..most jy t3's are .48ar which suits a low VE low reving slant just fine.

Doesn't a variable vane turbo do the same thing with only 1 turbo?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

No. Vnt turbos use defectors in the turbine housing to affectively cange its a/r..its still stuck between two set a/r on both the small and large end of things. Not sure if anyone has developed a stand alone controller to adjust vanes variably..infinently..also..a vnt compressor has a non variable fixed compressor...

On my j-piped gt37 vnt slant i had...the ar closed was aproximately .50ar-wide open was approx 1.0ar in t4 terms..also..compounds pressure ratios are multiplied. Not additive.

Btw..on the gt37 powerstroke unit..i had placed a fixed length rod inside of the vnt hydraulic cylinder to limit piston travel and essentially made it a fixed..but easily varied ar turbine housing..in factory default..the vanes are closed in that unit with oil pressure alone..a electronic solinoid controlls oil flow into the cylinder that actuares the vanes.

From my compound pal..hes a expert on the matter and one of a handfull of working awsome compounded gas jobbers...

What's your power goal?

If 0nly 400whp, k03 which flows about 26-27lb/min. Might be a good size to spool fast around 2000rpm

What's the lb/min of tdo4b? 36lb/min or higher?

If it's only 36lb/min, it might not be enough to get 400whp.
Compound sizing rule of thumb is kinda like this. The small turbo should be at least half the lb/min of the big turbo.

So if u want 400whp, the ko3 as a small turbo, is big enough since it flows about 26lb/min

For the big turbo, u should get a turbo that flows at least 40lb/min

And more...

gt28 for a small turbo for your 400whp goal will work, but I think it's too big and it will spool slow compared to a ko3 or ko4..
Ko3, you'll be spooling fast. Maps will be totally different in compound set up