Twin Turbo / Supercharger system

Chris Foogle



Okay so I'm at it again...trying to break the mold. The twins are being renovated a little after the recent dyno numbers. The secondary was a bottleneck and the dyno showed it. It's getting swapped out for a much larger Schwitzer S-3A, which should allow the primary to breathe alot deeper, and in dropping the pressure ratio, make a lot cooler and increased air mass. However, more lag is going to come with this, which I need to counteract. My recent objective is to lose the smoke, especially pre-boost smoke from alot of unused fuel, which can't be tuned out of this mechanical engine without sacrificing perfromance curves downline. So my idea is this....add a belt driven supercharger to handle the off idle air supply shortage, and control it with an electric clutch managed by a pressure switch monitoring MAP. Sounds easy enough, overdrive the charger quite a bit to have boost right off idle, then knock it offline when MAP reaches 12-15 psig, at which time the turbo system will be spooled to take over the air delivery. The problem is how to plumb the supercharger so that it doesn't inhibit performance once it's not needed, but when it is needed to provide the majority of the required air for the engine. I think I've got it figured out though, I spent quite some time crunching ideas and drawings until I came up with the idea that I have drawn below. A bypass valve will either close loop the charger when it's called for, or bypass intake air around the charger and directly to the turbo system from the air filter. When the charger is energized, it will feed the primary turbo which will send it downline throught secondary, then the IC and finally to the engine. I think I'm going to actuate the bypass valve with a vaccum diaphram / solenoid on a bellcrank....now if I could only find a 5" throttle body to use for this purpose to save having to fab one up!!

After studying many charger maps, and entering cost into the equation, I think I have decided on an Eaton M90 or M112, just like what is found on several OEM apps from Ford and GM to name a few. So anyway, all your thoughts are welcome, pro or con.

 

did he ever get this going?? if there's one guy that could it'd be chris.

 

I dont think so..........he checks in here on occasion so we need to ask when he gets back.....damn guy works way to much

 

The old detroit diesel 2-stroke engines came with a supercharger and a turbocharger, have you considered a blower off one of those old engines. If you didn't bybass the blower and kept in spining couldn't you get more air in, with out negatively effecting air flow? If you already finished your turbo/supercharger post some pics...please

 

oh stop it............
they where blowers not superchargers.
they where used to push air in to the cylinder and push exhaust out.
they where not originally intended for performance.

also a m90 or m62 are easy to mount just about any where.

 

Yeah, I know the blowers were used to scavenge the exhaust out of the cylinders..but last time i checked the superchargers and turbochargers move air just the same.

 

the "blowers" on 2 stroke Detroit's are modified to be put on a gas engine.

what i consider a "true" supercharger like a 6:71, 4:71 or 8:71
force both air and fuel.
the paxton like superchargers just force air. so basically they are a belt driven turbo.
in that case they take power from the engine to make power.
where a turbo just uses the exhaust to make power. seems like the better way to go.

 

yeah...I understand where your coming from, I would stick with turbocharging and plan too..but those old detroit screamers sound cool!!...the college that Im going to has a 6v92T..so you dont consider it a supercharger unless there is fuel going threw it.

 

looking at that diagram why is the supercharger there? would it work better after the output of the secondary before the intercooler? my thoughts are on twins the secondary helps spool the primary. and the secondary is after the primary turbo on the incoming airflow. so why isn't the supercharder before the secondary in the same mannor as it'll help spool the primary. correct me if my theory is flawed......i'm thinkin' out loud here.....

 

Yes I'm still working on this, but it hasn't been high priority, and I'm still collecting parts. The purpose for the super is purely off idle for streetability. I have a rather large secondary, and therefor spool-up is slower. The super is only there for the "street" factor and as such is on an isolated loop so that it doesn't hinder the operqtion of the turbos when they phase in. I have updated the design just a little. Instead of a butterfly valve where it is now, I have designed two 3" throttle bodies that are hooked to one another, but out of phase. This leaves two seperate intake tracts...one for the super and one for the turbos. The throttle bodies are controlled by a wastegate actuator and as boost climbs above 10-15psi ADJUSTABLE), THE SUPER PHASES OUT AND THE TURBOS SUPPLY AIR. tHE TWO tb'S ARE ADJUSTABLE TO ONE ANOTHER SO AS TO FINE TUNE THE CROSSOVER (oops sry for the yelling) A late M90 or 112 has an internal bypass so parasitic loss is nill once out of the loop. I overdrive it by 6:1 for instant pressure and the redline of the super matches that of the engine so as not to overspeed the super, yet eliminate the need for electric clutch drives. Again, this add-on makes no more power, just burns pre-boost fuel efficiently for blistering off idle power. I intentionally did not plumb thre super in with the turbos for the sinple fact that it can not handle the pressure ratios, nor the flow of the compounds in full spool, either on the intake side of them, or the pressure side. A super that could would be too large to accomplish the reason for it being there.

Chris