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Hypothetical Oddball
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Author:  sixinthehead [ Thu Jun 01, 2006 10:30 am ]
Post subject:  Hypothetical Oddball
OK folks, this is why I chose my screen name; I've always got this stuff floating around in there. I just wish I had the funds to try it!

Take your average slant, and split the exhaust manifold (Dutras will do nicely).
Hang a turbo on the back one, and, get this, a throttle body on the front one.
Plumb the compressor through an intercooler to the throttle body. Block off the carb pad on the intake manifold (or maybe hang a fogger bar down through it :twisted: ).
Have a cam ground to turn the front three cylinders into a pump inhaling through the exhaust valves and exhaling into the intake. Run the rear three on the Miller cycle (delayed intake closing event to shorten the compression stroke, ok with forced induction - see Mazda Milennia S).
Three fuel injectors on the rear cylinders, and grind every other tooth off of the reluctor in the distributor.

This fell out of my head last night and I couldn't go to sleep for three hours.
Now, I just have to figure out how to run it as a two-stroke to get six power stokes back!

Probably, the only thing all this would accomplish is emptying my pockets, but it would be cool to see people try and figure it out when I opened the hood!
Author:  dart64rg [ Thu Jun 01, 2006 11:03 am ]
Post subject:  Re: Hypothetical Oddball
Quote:

This fell out of my head last night and I couldn't go to sleep for three hours.
Now, I just have to figure out how to run it as a two-stroke to get six power stokes back!
To theoretically make it a 2-stroke you would have to have dual lobes on each lifter per valve, much shorter durations, and figure out the right amount of overlap.

I am not sure the front cylinders would create enough boost to not be a drain on the turbos efforts. Everytime the the front intake(now exhaust with your plan) are open the turbo would try and force air in as the cylinders are trying to force air out.

I think the idea of converting to a 2-stroke could work, with lots of money and engineering experience, and a lot of trial and error.

But in the end would it net an improvement over a turbo 4-stroke?


By the way I like the idea, just not sure if it would be worth it in the end.
Author:  sixinthehead [ Wed Jun 14, 2006 11:10 am ]
Post subject:  The storm intensifies...
Obviously, a lot of thinking will have to go into the cam design, but the idea is to use the front cylinders as a positve displacement pump.
If the former exhaust valve opens at TDC, let's say, it will see pressurized air from the turbo, which should actually help drive the piston down. Nearing BDC, the former exhaust valve would close and the former intake valve would open, allowing the piston to push the air into the intake manifold as it rises.
Events for the former intake valve will have to be carefully timed to avoid reversion between "pump" cylinders, i.e. you probably wouldn't want two valves open at the same time.
Let's say this is a 170 engine.
With the rear cylinders operating on a four-stroke cycle (displacing 85 c.i. with two crank revolutions) and the compressor cylinders working on every upstroke (displacing 85 c.i. with each revolution), the "pump" front cylinders will be moving twice as much air as the rear cylinders (ignoring the turbo for the moment).
My question is; Still ignoring the turbo for a moment, what kind of boost will be created in the intake? It's basically like a Roots blower, creating boost by cramming in more air than the engine can use. Will the boost plateau or rise exponentially with RPM?
Knowing and managing this boost will detemine how crazy to get with the turbo.
This thing has the potential for uncontrolled boost levels; it might turn into a diesel before I'm done :shock: !
Author:  AndyZ [ Wed Jun 14, 2006 12:55 pm ]
Post subject: 
I am not sure that I fully understand what happens here but;
When the compressed air coming out of the "compressor" cylinder enters the intake, wont it re-expand as the "engine" cylinder reaches the bottom of it's intake stroke defeating the the purpose and maybe even heating your charge more and possibly robbing power? I am not saying it won't work, just that I dont understand. Interesting thought though.
Author:  Matt Cramer [ Wed Jun 14, 2006 2:02 pm ]
Post subject: 
Theoretically, without the turbo, the piston compressor would give you a 2:1 pressure ratio. In practice, you'd have a few pumping losses, bringing it down a little, but it should still be 13-14 psi. If you put a turbo on this, the boost could easily get out of hand - 8 psi of boost on the first stage would translate into 30 psi of boost, total! Two stage compressors can generate more boost than anything other than a diesel can really use.

It is kind of interesting for creativity, but I think the overall power would be a little less than if you used all six cylinders for making power.
Author:  AndyZ [ Wed Jun 14, 2006 4:51 pm ]
Post subject: 
Quote:
Theoretically, without the turbo, the piston compressor would give you a 2:1 pressure ratio. In practice, you'd have a few pumping losses, bringing it down a little, but it should still be 13-14 psi. If you put a turbo on this, the boost could easily get out of hand - 8 psi of boost on the first stage would translate into 30 psi of boost, total! Two stage compressors can generate more boost than anything other than a diesel can really use.

It is kind of interesting for creativity, but I think the overall power would be a little less than if you used all six cylinders for making power.
What I don't understand is how can the same amount of volume make a 2:1 boost? Thanks for explaining this to me. :oops:
Author:  Matt Cramer [ Wed Jun 14, 2006 6:50 pm ]
Post subject: 
Quote:
What I don't understand is how can the same amount of volume make a 2:1 boost? Thanks for explaining this to me. :oops:
It's the same volume, true. But the compressor set of pistons moves air with every revolution - it's just intake / exhaust, no compression or power strokes. The power set of pistons moves air every second revolution.
Author:  AndyZ [ Thu Jun 15, 2006 1:00 pm ]
Post subject: 
Quote:
Quote:
What I don't understand is how can the same amount of volume make a 2:1 boost? Thanks for explaining this to me. :oops:
It's the same volume, true. But the compressor set of pistons moves air with every revolution - it's just intake / exhaust, no compression or power strokes. The power set of pistons moves air every second revolution.
I figured that out while driving home last night thinking about it. Interesting idea. Hey, Why not bolt another slant six onto the other one as a compressor? Probably cheaper, Just run a 1:1 valve timing gear and a different cam on the compressor slant. But you would have to install it into a Duesenburg or something with a large engine bay!
I am joking.
Author:  sixinthehead [ Thu Jun 15, 2006 1:20 pm ]
Post subject: 
Thanks for the confirmation, Matt. I was figuring on the 10-15 psi neighborhood.
A while ago, Hot Rod bolted a Roots onto a crate Hemi. Their numbers showed about 431 ci displacement for the blower with each crank revolution, going into a 426 ci engine. With the blower slightly underdriven (90%?) they made 9 psi at 6000 rpm.
Now, back to the compound blower numbers; Are there basic formulas for calculating those figures that I/we would be able to understand without a degree in thermodynamics?
Thanks for the help and interest; this is really just a brain exercise for me at this point. I'm trying to challenge myself to learn more and have some fun at the same time.
BTW, Andy, can I borrow your Deusenberg? :D
Author:  AndyZ [ Thu Jun 15, 2006 4:01 pm ]
Post subject: 
I wish I really had one... An SJ!
I am presently fitting my 64 Dart with a Paxton. ~6-8 lbs. street car. I just finished up the drive pulley and now I can start on the brackets and then the plumbing. Should be fun! I am always interested in new ideas. That 3/3 compressor/engine was a new one for me. Would ithat configuration still work as a 2 stroke?
Author:  Matt Cramer [ Fri Jun 16, 2006 5:35 am ]
Post subject: 
Quote:
Now, back to the compound blower numbers; Are there basic formulas for calculating those figures that I/we would be able to understand without a degree in thermodynamics?
It's pretty easy if you're just calculating total boost: The trick is to think in terms of pressure ratios rather than boost levels. A pressure ratio works in absolute pressure - you add the atmospheric pressure to the pressure the boost gauge measures, and that gives you absolute pressure. The formula for a pressure ratio is simple:

Pressure ratio = compressor discharge pressure / compressor inlet pressure

For example, a turbo making 14.7 psi of boost where atmospheric pressure is 14.7 psi would be putting out 29.4 psi absolute, for a 2:1 pressure ratio.

When you have two compressors working in series, you just multiply the pressure ratios.
Author:  D150 [ Sun Jun 18, 2006 6:55 am ]
Post subject: 
sixinthehead .... I like your "way out in left field" thinking. Mopar guys are thought to be a little different anyways, but slant six guys, well.... If power was all we wanted, most would just put in a 383 or 440. But not us Slants!

8) COOL
Author:  sixinthehead [ Mon Jun 19, 2006 10:48 am ]
Post subject: 
Thanks for seeing it my way, D150.
And thanks for the insight, Matt. Now I've got some figuring to do...
Author:  sixinthehead [ Thu Jul 20, 2006 3:15 pm ]
Post subject:  Still brewing...
As my research continues, it turns out that the Millenia S runs 28 psi stock... :shock:


Maybe, just maybe :wink:
Author:  mpgmike [ Sat Jul 22, 2006 8:21 am ]
Post subject: 
How 'bout this one as a twist. 2 intake manifolds, 2 exhaust manifolds. HOWEVER, rear 4 cylinders run the engine, and the front 2 make boost. Run the intake charge through the intake (instead of the exhaust as initially mentioned), and run the back into the intake of the rear.

Have the cam modified so that the lobes on the first 2 cylinders are doubled (will open the intakes on every down stroke and the exhausts on every up stroke). Also, give them some serious lift. This should create some sane boost levels without the turbo.

Mike
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