6v92 350hp injectors / turbo

[Iceni John]

Is there such a thing as an electrically-controlled blower bypass valve that could be added to a non-bypass engine?   Then one could choose whether to have maximum blower output but at the expense of efficiency and fuel burn, or reduced blower output but with reduced power needed to drive it.   Does that sorta make sense?   Surely it wouldn't be that difficult to rig up such a valve.   Or is it a Rube Goldbergian exercise in futility?

My turbo boost gauge reads from the 1/4" port on the driver's side of the blower's airhorn, where my Quickstart ether injector used to be, and I see up to 26 PSI boost under full load.   I assume the engine's air galleries are not also getting 26 PSI after the air has passed through the blower.   What is the corresponding scavenge air pressure in the air galleries under full load?

John

[bevans6]

I became fascinated by the subject of how much hp it takes to power the blower on our engines and how that affects efficiency.  Google is obviously the front end to the greatest engineering library ever devised, and I quickly found a site with engineering equations for calculating all of the operational parameters of a roots blower in industrial applications (it's used a lot as an air pump in industrial air pressure and vacuum installations).  It turns out that an 8V71 blower takes right around 7 bhp per blower rpm at 6psi pressure differential.  My Detroit book says the pressure differential for an 8V71 is between 5 and 8 psi for most engines, so I used 6 psi.  That is 32 bhp at 2200 rpm, so if you took a notional 8V71 T engine that was putting out 350 bhp, which my engine happens to do, add a few percent of driveline losses to turn the blower, you see that the engine is using in the ballpark of 10% of it's output power to turn the blower.  You could therefore say that if the blower wasn't there, it would make 385 hp.  Or you could say that if you changed the parameters of the turbo and the fueling you could get the same 350 hp with around 10% more efficiency.  Now the question becomes how effective is the bypass feature of a bypass blower?  The blower on our engine is running around 2:1 crank speed, more or less, and is moving around .5 Cubic Feet of air per crank RPM.  The engine is 568 cubic inches, or .33 CF per rotation, so the blower creates an excess air volume of .17 CF per revolution.  At 2200 rpm, that's 374 CFM of excess air creating around 6 psi of pressure differential that needs to be bypassed to the intake side of the blower to perfectly equalize pressure on both sides of the blower and reduce the BHP needed to spin it to zero (in theory).  The engineering sites I found suggest that the size of the blower bypass can't pass that amount of air, so the bypass needs to be less than 100% efficient.  If it could reduce the pressure differential by half, the power needed to spin the blower would reduce by half, and you could expect a 5% improvement in efficiency if the engine requirements were optimized to achieve that.   

What happens at less than full power?  Lets say that my engine in my bus needs 150 hp to cruise at 60 mph at 1800 rpm (I don't know that it does, I'm just doing a what-if).  Blower power at 1800 rpm (at the same 6 psi pressure differential) is 25.8 BHP plus 5% for driveline loss make just under 30 bhp.  That is 20% of the power output of the engine.  If a bypass blower engine could reduce that loss by half, you'd gain 10% in real on the road efficiency, which is very close to what people report in real life.

Fun to think about this and try to work out an explanation.  I doubt that I am dead on with this theory, but I think that I am on the right track.  FWIW, a 6V71 blower (and maybe a 6V92 as well) is shorter than a 8V71 blower, moves about 10% less air per revolution, and requires about 10% less power to spin.

Brian

[luvrbus]

Detroit experimented with the centrifugal type blower on the 110 DD to take less HP it ran 9.8 times faster than engine rpm that didn't work to well in mobile applications.
There are 16 different blowers for the V DD engines,the best blower is the full bypass the mini bypass is ok it takes some pressure off to relieve the hp drain but not as effective as the full bypass for making power.
Those blowers have 5 different drive ratios and different lobes, some of the high HP 92 series in the marine world use a blower developed by Stewart and Stevenson design to pump more air with less hp       

[Darkspeed]

Do you happen to know the part number for a full bypass 6v92ta blower?

[Darkspeed]

Can someone with a 350HP 6v92TA please give me the exact part number on their turbo....Thank you!

[TomC]

Before the Series 60 came out, Detroit experimented with many different blower configurations in an attempt to extract more efficiency from the 2 stroke design. The most efficient design was the 3 wheel turbocharger. Picture a normal turbocharger with an additional turbine housing in the middle of the turbo that was powered by the oil pressure of the engine. The theory was that when turbo pressure dropped below 5psi, the valve would open on the oil turbine and spin the turbo keeping the turbo producing at least 5psi. When the engine accelerated, then the turbo would take over and the oil valve would close on the 3rd turbine wheel. It worked well-but engine response was considerably slower causing black smoke coming out to the point that Detroit felt performance was sub par and the project was abandoned.
Another was to use a mechanically geared turbocharger with over run clutch-exactly what they use on the big locomotive engines. Same principal, except they used the rpm of the gear drive versus the turbo speed. Was like a bicycle in that the engine powered the turbo until the engine accelerated and the turbo over sped the gear drive. But this had good response time-but was too big and bulky. Hence the full bypass blower was as far as Detroit went as to making the 2 stroke more efficient.
Now if only they used air to air intercooling (like my 8V-71) along with common rail electronic fuel injection....

[luvrbus]

Can someone with a 350HP 6v92TA please give me the exact part number on their turbo....Thank you!

Call Tom @Turbo Resource 928-505-4610 tell him what you after and let him build you a turbo that will make more boost,more power and less smoke.Pull your inter cooler and see how many passes it is 1,2 or 3 you may be chasing rainbows if the after cooler is not large enough.Right now you have a 250 hp engine and a 100 hp is huge jump plus $$$

[HB of CJ]

Great subject and thank you.