Twin Turbo / Supercharger System
 

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.
http://img407.imageshack.us/img407/3...jpegjb3xk9.jpg

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............:bat:
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

holy mother of god chris. you gotta get this things going now. i gotta see it. this is going to be something else!!

dude has way too much time on his hands!! I WANT TO SEE PICS!!!

http://img512.imageshack.us/img512/6...lleljpemf7.jpg

I figured I'd better post an updated drawing of what I was talking about in the earlier post. Also note the jackshaft pulley design on the super's drive. To get a 6:1, it would take a huge crank pulley, with the jackshaft, a regular sized pulley can be used on the crank, and the overdrive ratio is compounded through offset pulley sizes on the jackshaft. For the Throttle Bodies, I'm using good ol' Chevrolet 3" TB's. They also have a mass air sensor built in to them that I plan on leaving in place. Once I get a friend of mine to make the board to read them, I'll be able to monitor air MASS that the engine is injesting. Just another cute by-product of the GM MAF/TB assembly.

As far as time on my hands....I used to have alot more, but not anymore. Which is why this hasn't come to fruition yet!

i wish i had the means to do a mock up of this set up

why not look for a sponsor?

The trick that I employ to build this kind of stuff is just to use what you have on hand. I don't spend the bucks to build what others are buying off the shelf. My compounds consist of a marine S3A off a John Deere marine engine I R&R'd, my BHTB3 is a $400 OEM application, the supercharger will be a take off from a lightning or cobra that has been upgraded to a whipple or turbo. All the plumbing is exhaust pipe and off the shelf tight radius stuff that I cut to the right angles. I have spent no more than a couple 3 grand on this engine in the last 4 years....I'm not the richest, and I am a family man. It can be done though without a second mortgage. Time invested?? Countless hours....and crunching numbers and searching for the right parts, but that has a benefit as well right? So don't be afraid to experiment, go outside the box, and even fail once in a while to get it right. It's really where a lot of the fun is in this hobby. It's another reason I'm a 12 valve kinda guy.

So a little more tech on this thing now that I have some time.....The trick with tuning this set-up is going to be phasing the throttle bodies. Because the super will be at 5 or 6 thousand rpm at idle, it will be breaking the positive pressure point before you even tip the throttle. As soon as you do, the ratio will ramp up the super very quickly and provide 10 to 15 pounds of boost right off idle. This will allow a pretty agressive pre-boost fuel curve because the air will be there to burn it. The by-product is alot more exhaust energy as well, which will get the turbos into spool much quicker too. So when the super is peaking it's pressure we want to start phasing the throttle bodies through adjusting the actuator (a take-off turbo wastegate actuator) with a controller that's the same as used on the turbos. The secondary turbo should also be in early spool at this point as well. Ultimately, we want supercharger pressure to be about equal to turbo pressure when we start to phase the throttle bodies. This should provide a seamless transition into turbo pressure. Once the throttle bodies have completed the intake tract switch, the super will be pumping against a closed TB, which will trip it's internal bypass and take it pressure ratio to zero, causing no parasitic load on the engine, nor create any excessive load wear on it. The important thing here is that your chosen super has a bypass, if not, you have no way of "turning it off" so to speak, short of an electric clutch drive which carries a bunch of it's own challenges. So while the super's TB is shut, the turbo's TB is wide open, leaving an un-obstructive intake tract so that they operate as normal.

So what happens at part throttle...say cruise power when you're only making 6-8 pounds of boost? Well, because the TB actuator is dynamic with manifold pressure, and adjusts in a linear fashion, The super AND the turbos may be operating in parallel with the TB's allowing both systems to feed the engine. The pressure ratios will balance and therefor not be a problem, as soon as you tip the go pedal a little more, the turbos will make more pressure than the TB actuator will allow the super to see, and consequentle cut it off from the loop by phasing the TB's completely....but talk about some instant passing power right?

So anyway, that's the way all the numbers crunch....in practice we'll see if it pans out, but it should. Just a matter of tuning the TB actuator, as well as adjusting the bellcrank that connects the two of them together.

Oh and some of you might notice double CAC's on the turbos but no CAC on the super. Firstly, cooling the outlet air from the primary before it gets to the secondary makes huge gains in efficiency for the secondary's compression stage. I don't think a CAC is really needed for the super because in reality, it's duty cycle is so short, and low in the rpm range, it just won't matter enough to try and figure out WHERE to put a 3rd cooler! I estimate the super will be contributing air to the engine for a maximum of 10-15 seconds (and more than likely a lot less) from a hard throttle stand still before it's bypassed and the turbos take over. And under normal driving, pressure ratios aren't high enough to generate alot of heat to get rid of anyway.

Chris

cummins express
 

I see you are still alive! Let me know if you need any help fabricating this thing. Give me a call some time

James

the only problem with those "stock" blowers is that they need a manifold to set on, if you use a paxton or vortech "sealed" unit i think it would be easier to mount and work with even though the price wont be as low. i would think that big charger would force too much air past the small charger and over spin it causing bearing damage, a good thing is that it will actually start to scavage exhaust at higher rpm cause the small charger will begin to spin faster than the exhaust can drive it, this will start a sucking effect and "clean" the cylinders for the fresh air........i could also be way over in left field with all this too.....

6v92,8v92.... still just a blower. just mounted on top...
a blower and supercharger have different tolerances from the rotors to the case.
i know people refer to gas engines as "blown" with a blower on top.

to me when a blower has been modified to make more power on a gas engine it then becomes a supercharger. just my awkward way of thinking.
you can go here
http://www.blowerdriveservice.com/contact.php

they are really cool when answering questions.