8v92 Superchargers

Hello all. My apologies if this isn't the correct forum/section to ask this question but I've been reading trough for a couple days and not seeing anything answering my specific question. Can a twin screw supercharger or centrifugal supercharge be used on an 8v92T (TA) engine? I’m a general fan of motor sports and have been watching some super semi sled pulls and tractor pull events online and decided to look into the performance tuning of these classes. I’m guessing there’s a basic mechanical reason, but I’m unfamiliar with 2stroke diesels. At this level of performance, I’m sure “cost” isn’t an issue so if it’s no trouble, could you share some insight as to why a more efficient blower/supercharger isn’t or couldn’t be used. I'm seeing upgraded turbos and injectors quite often. Thank you for your time. Mike.

 

8v92ta is super charged ( gear driven ) turbocharged ( exhaust gas driven) with a aftercooler. All 2 cycle Detroit engines have a super charger, turbos add more intake psi so you get more oxygen into the cylinder but, at a cost , it heats the air so it’s thinner. Now you’re not getting as much oxygen so you run it through the aftercooler to cool the air and this makes the molecules closer thus more oxygen. OO 8v92 TA usually put out 440 hp , want more , change size of injectors. Can twin turbo and twin aftercooler, could put on a “ red rooster “ if it’s legal for the pull.

 

Technically they are not superchargers. They provided minimal boost if any, they are called "scavenger blowers"

 

As far as centrifugals, 2 stroke Diesels need the blower for scavenging, I would guess that gearing a centrifugal to move enough air at idle so the engine would run would result in overspeeding the blower at higher rpm.

I would guess that everyone sticks with the roots type because the blower doesn't make major boost in these applications, the turbo handles that.

Beat me to it!

 

Scavenger blowers, roots type which are referred to as positive displacement, are necessary for them to run. The exhaust valves open when the ports are open. The pressure from the blower pushes the exhaust out through the valves and provides fresh air.

All those superchargers you see on top fuel dragster are copies of those originally installed on 2 cycle Detroits. They still use the size of engine, ie 871 would be a blower off an 8v71.

 

Thank you all so much for the replies. Let me see if I’m unpacking the knowledge well.


"want more, change size of injectors."

I've come across that as one of the typical upgrades for the 8v92t's. My initial thought though, was that "upgrading the charger" would be a simpler bolt on upgrade. I'm aware that those types of upgrades can also require the fuel system to be upgraded but it still seems like upgrading the blower/charger wasn't/isn't done. Is it a "can't do it" issue?

"Technically they are not superchargers. They provided minimal boost if any, they are called scavenger blowers"

Is this why a twin screw charger isn't or could not replace the roots blower? Since they are both positive displacement, I'm not sure what would be the drawback. Too much Pressure?

"I would guess that everyone sticks with the roots type because the blower doesn't make major boost in these applications, the turbo handles that."

If I'm understanding the nature of these engines, the factory blower doesn't need to make "major boost" to scavenge. While seeking excess power numbers, I'm wondering why this particular bolt-on part seems to have been left alone. I guess I thought it would be often mentioned why competitors at these levers don't or can't change to a more efficient charger that "does" add more power while also providing the positive displacement for scavenging. *Twin screw - Twin Turbos*,,, why not?

"Scavenger blowers, roots type which are referred to as positive displacement, are necessary for them to run. The exhaust valves open when the ports are open. The pressure from the blower pushes the exhaust out through the valves and provides fresh air".


I've seen the internals of the 2stroke diesel, and I comprehend how the blowers are needed to force the exhaust gasses out. I've wondered if replacing the roots blower with a twin-screw supercharger would supply "too much" air in the lower rpms for this type of engine? I'll be honest and say I can't see that being a problem but again, I'm not seeing/reading a clear reason why this could be counterproductive.

I found some interesting builds of a twin charged Cummins. The first video has a roots blower and the second has an Eaton screw-type. I'm not comparing the Cummins to the 8v92t, just wondering if the same thing could be done to the 8v92t by replacing the roots with a screw-type charger.

Roots/turbo -


Eaton/turbo -

 

Little info here…. If you want to build more horses with a Detroit / GM diesel, you will need a bypass blower as well as the turbo and bigger injectors.

Not all 2 strokes have the bypass blower….

 

It's been a while since I've worked on a 2-stroker. I seem to recall they didn't build a whole lot of boost with a turbo anyway because the ports were almost covered by the time the exhaust valves closed.

What does a bypass blower do?

 

It allows the turbo to push air around the blower when the rpm’s drop to the point the blower is starving the engine for air. Basically at that point the engine is running mainly from the turbo like a 4 stroke.

If memory serves me, around 475 horse and beyond needs a bypass…

 

All the big industrial two stroke diesels use a gear drive to the turbo for startup then the exhaust takes over powering the turbo. Detroit Diesel was experimenting with this for the 92 series before they released the Series 60.