Twincharging camshaft

bentwrench wrote: This assume the turbo is the flow limiting factor. I think the roots will be the strangle point even though you're spinning the dog doo out of it. The end fed design is going to limit airflow me thinks. Force feeding it will certainly help. Logging pressures will provide answers. As long as the bearings and rotors in the blower are up to 12k rpm (with some overhead). I expect you have already looked into this aspect before getting this far.

The roots will not be a stangle point. It simply takes what ever is presented to it's inlet and compounds it.. be that atmospheric pressure or air already under pressure. I changed the needle bearings in the eaton so it's in half decent shape!

This assume the turbo is the flow limiting factor. I think the roots will be the strangle point even though you're spinning the dog doo out of it. The end fed design is going to limit airflow me thinks. Force feeding it will certainly help.

Regardless of what type of setup it is, the area of the air inlet will always be a hard limit to how much power something can make because even turbo cars are only fed air by atmospheric pressure. So whatever the size of your air inlet is, the amount of air that will flow through that orifice at ~14.7psi of pressure differential is a hard limit to how much power you can make (assuming all your oxygen is coming from atmosphere and not partially through a nitrous system etc). Even then it's not actually that much air flow because while there is usually ~14.7psi pushing air in, there's never 0psi behind that inlet so the actual pressure differential causing airflow into your engine is less. There are plenty of setups with other limiting factors besides how much air can be pushed into their air inlet, so this is rarely the weakest link. I'm just throwing info into this thread for anyone who's interested in compound turbocharging. The HX35 on this build has something like a ~58mm diameter air inlet which works out to something like a 600hp ceiling.

As far the roots blower, how much air the atmosphere can push into their inlet actually IS frequently their weakest link. A Thunderbird SC m90 like the one i got for my never-started compound build can only suck <400hp worth of air into its inlet, maybe even as little as low 300s. But, if you feed it air that's already pressurized you multiply its 'power potential' by the same amount, so taking a 300hp supercharger and feeding it air at 1.5x atmospheric pressure makes it a 450hp supercharger. This is a critical concept in compounding because the smaller turbo (or the blower in this case) could almost never flow enough air at atmospheric pressure to make the power the setup makes. That's why the big turbo actually comes first in airflow. The big turbo is your big inlet and your big power potential. The smaller turbo sucks air coming out of the big turbo, and while the small turbo spools first the only reason it doesn't limit the engine to lower power limits is because when the big turbo spools up it pressurizes the air going into the small turbo, thus increasing its 'power potential'.

One interesting problem with compound turbocharging that won't be present with this turbo+roots setup is wastegating the small turbo. Usually if you have a 300hp turbo you have a turbine side that can flow 300hp of exhaust, and when it does so the turbo is set to 'kill'. Once you start pushing 600hp worth of air through the exhaust you have to have a wastegate that can flow 300+hp worth of air AROUND the small turbo and still be able to effectively control it.And, you can't just dump that flow out screamer pipe style because you still need it to spool the SECOND turbo, so it has to be merged back in with the turbine exhaust after the small turbo! Since you are only getting part of your PR from the small turbo, you don't want it set to kill. So you may have only 25-30% of your exhaust going through your small turbo and 70% going around it through your (first) wastegate! Definitely not something you see in a single turbo setup, and luckily not necessary with the roots blower.

Vigo. This is the reason I signed up to this forum. Very informative. You should get your project on the go.

Fun project! I used to have essentially the same engine with an HX-35, and an antilag system that used a couple pipes with automatic solenoids in them to bypass the throttle body, run using a megasquirt 3. I ran it on E85 to try to keep it together and commuted to school in it a 100 miles round trip for a year and a half, autocrossed it a couple times. It was my daily driver. One of the issues I had even with E85 was that the stock HX-35 wastegate wouldn't flow enough to keep boost below 27 or so IIRC. The antilag worked perfect (I used some ECU tables that some rally racer was using) but it was super antisocial (huge backfires while off throttle) and difficult to drive smoothly with crazy torque available and stock terrible fox body rear control arm nastiness. My Hx-35 was off my 12 valve 5.9 Cummins, not 6.0 Ford. Jcamper

Ha. Nice. Sounds a blast that! The internal wastegate of the hx35 is tiny. I have a 44mm external wastegate that should deflect enough gasses to control boost. . I really don't need much boost from the turbo. Maybe 12 psi as a start. Then say 7 from charger should compound to approximately 25psi. Wish me luck!