8v92 Superchargers

I feel blessed to see the information being shared and discussed here. I'll respond to earlier questions/comments and share some things I've come across. (Had some car troubles that kept me off the computer a couple days).

"The twin screw compresses the air internally between the rotors, the Roots just moves it around the outside of the rotors and "stacks" the air into the manifold to compress it."

This was my understanding as well. Since they are both positive displacement, I thought the higher efficiency of the twin-screw design would actually benefit the lower rpm range. So, (asking and thinking) does the roots-type provide a 'volume' of air that better suits this particular 2-stroke diesel application?

"The air box drains actually perform a dual purpose. They provide a means of draining the air box of any engine oil, but they also give the engine a way to “blow off” any excess air pressure.
If you ever get around a Detroit running just stick your hand under the drain and feel the air blowing out. It’s like a pressure relief or a bypass around the thermostat in a cooling system."


I hadn't come across this info at all, reading about the 8v92T. Thanks for sharing that.


"What exactly is the application you want to build one for? Working truck, sled puller, or just a toy…?"


One of the last two; Either a toy or sled puller.

I'll elaborate my passion for this. I've always loved motor sports and performance. Motorcycle road racing, Sled pulling, Monster Trucks ARGH, ARGH ARGH! "Time Allen"!! I love classic trucks, (1950's) and diesel engines. Most of all I love my wife and kids. I came from a broken home and never built anything with my dad. As my kids are getting older, I'm realizing I haven't done anything like this with them. So, if I'm going to tackle something that we can share and bond over, I want it to be with the things they know I enjoy and have shared with them.

The first time I heard a Detroit Diesel 8v92T,,,,,,, that became the sound I wanted our project to have. I don't care for any of today's electronics and although I know the budget for this is going to be high, I don't have unlimited funds. With those realities my initial plan is to rebody a 1995-2001 F550 with either a 58' Chevy Apache or a 56'F100 and of course an 8v92T.

I live in a very sandy area of South Texas and a drag strip not too far from where I live. I'll have options of having fun with whatever I build either way. I don't care about winning anything. I just want to build something with my kids that no one else has. That's always been a cool thing to witness.

Back to this topic, I've driven several supercharged vehicles so my initial thought of swapping out the roots for the twin screw "seemed" simple as an upgrade, but I can't find it having been done before. I'm going to start looking into the boat racing forums and events and learn what they are doing (why/why not).

I've found quite a few upgraded and twin turbo builds. Here's a monster one!


My current thought is that racing/high hp builds aren't needing or looking for increasing the low rpm (say 1500<) so, why bother with a more efficient supercharger for that range. Or, maybe sizing the turbos correctly negates using something like a twin-screw supercharger altogether. Fair enough. I'd like to build this for the memories and my kiddos and I to have created something different,,, or at least not common.

 

First, I could have sworn I replied to this the other night?!? No worries I probably didn't hit send and refreshed the page or something.

I will definitely be pondering “diligently”.


“Remember that in the Detroit application, the blower is only providing volume, with minimal boost. You also have to remember that when the 92's were common, the twin screw wasn't really available. The computer controlled machining tools that have made twin screws more accessible weren't readily available. So everyone who hopped up Detroits never considered that twin screw route.”



I have been overlooking this. Sometimes “if it ain’t broke don’t fix it” may simply be the reason why something isn’t done. And if there's no need to add cost for the low end "minimal gain" people may not have found a reason to bother with it.


“So it may be completely possible to get a twin screw to work, there are considerations. Yes, they are more efficient at producing boost, but at low power settings it would be producing internal boost when volume is what was needed. So it would inherently be less efficient at low power. That's not a problem if you're making a hot motor for a toy, it's not gonna spend much time at low power, but it would have to be considered.”


I’ll look into flow charts for roots and twin-screw chargers and see how much I can learn from the differences between the two. There may be something there along the point you make.



“The other thing I can think of is flow. It might be difficult to get enough flow at idle without running into overboosting at high rpm. I don't know enough about the twin screws to know for sure this would be a problem, but the fact they work in a different manner than a Roots makes me wonder. If one considers the clutched turbos on the big EMD 2 stroke Diesels (they use the same airflow pattern,) which spool up to much higher speeds above 1/2 throttle, it points to a need for variable blower ratios

Just points to ponder...”



Hmm. This will be an interesting avenue to look into as well. “If the twin-screw is focused on producing sufficient low-end volume, could it choke out up top or be ‘over-driven’?” (I believe this is what you are saying, please correct me if I’m wrong). I could see the potential issue there, if the twin screws don’t have the initial volume needed. Good stuff! Thank you for your thoughts and time. I’ll post up what I find from the flow maps.

 

Well, there's this,,,,!!!!

Supercharged Twin-Turbo 427 cid 7.1L Duramax - YouTube

 

If I can successfully put a twin screw into the this set up (or even single turbo) I'd be pleased. *Successful = safely running and not destroy itself


Twin Turbo Supercharged 2-Stroke Diesel Ratrod - YouTube