True, I think it was also my fault for bringing the word turbo into the conversation.
Naturally aspirated by definition means atmospheric pressure.When the piston descends during a 4 stroke induction cycle air fills the cylinder at no more than atmospheric pressure.In the case of a two stroke the induction stroke doesnāt exist.It relies on the scavenging effect of the exhaust gases leaving the cylinder pulling in the new charge of air behind it and the blower blowing it in, instead.Itās still naturally aspirated there is no compression of the inlet charge above atmospheric pressure on induction.
A turbocharger doesnāt block exhaust flow it just harvests the energy contained within it to compress the inlet charge, which is a lot.
The S in Cummins NHS means Supercharged ( forced induction above atmospheric pressure ).Not naturally aspirated.
As opposed to Detroit where the N means naturally aspirated.Not supercharged ( forced induction ).
Proof of the difference between a blower v a supercharger compressor.
There is no such thing as a supercharged Detroit two stroke.Itās either naturally aspirated or itās turbocharged forced induction.
For the attention of Franglais there is more than enough energy, contained in the expanded exhaust gases leaving the cylinder, to drive a turbocharger or two.
Why do exhaust gases leave the cylinder? They move from an area of higher to lower pressure.
Why do they flow into the exhaust and not into the inlet? Because the inlet is higher pressure than the exhaust.
So if the exhaust is at atmospheric pressure, then the inlet must be above atmospheric pressure.
Turbochargers di indeed take energy from exhaust gases. In a 4T they are moved out by the rising piston. That is not the case in 2T diesel engines.
The energy harvested by turbo comes from slowing down the exhaust gases.
It must impede the flow of gas. If otherwise we could make a perpetual motion machine.
Now tell me thatās being choked to a stall by its turbo.
To add there is obviously a massive surplus in the exhaust gas flow energy relative to the amount of energy that the turbocharger takes out of it.To the point where the turbocharger compresses the inlet charge and with sufficient energy still left in the exhaust gas flow to still maintain scavenging of the cylinder, let alone blocking the exhaust.
For SDUs attention agreed we didnāt have as much familiarity with Detroit two strokes in the UK haulage sector v US/Canada/Australia.
But thatās comparing apples v oranges regarding our specialist/emergency vehicle manufacturing sector.Especially predominantly dedicated to the demands of export markets including the USA and even the East European bloc often preferred them to Tatra etc.Basically the things were as familiar to me as my first car.
The exhaust gases flow out of the exhaust and not into the inlet because the exhaust valves open before the inlet port is uncovered by the descending piston.Just as a 4 stroke exhaust isnāt going to spit back through the inlet valves unless the inlet valves and seats are knackered or valve timing is wrong or too much valve overlap duration.The tail end of the evacuating exhaust gasses and gassed aināt going to suddenly reverse direction through the later opened inlet they are just going to leave behind a sort of vacuum in the cylinder which the atmosphere then fills through the inlet port.Which is the definition of scavenging.
The blower is just there to help fill in for poor scavenging situations like start up etc.A two stroke works mainly by scavenging.
Forced induction in the form of turbocharging fixes the remaining flaws in volumetric efficiency between exhaust, induction and compression.
Carryfast youāre very adept at harvesting information from Google, then presenting it as your knowledge. This cyber plagiarism often results in you dragging the thread away from its initial course as you fiercely argue semantics. Your continued argument against opinions and facts in harmony with your plagiarized information, albeit presented differently, clearly demonstrates the Dunning-Kruger effect and how it so aptly applies to you.
You show the skills of a politician in avoiding questions, particularly those that demonstrate your lack of knowledge and others that would require you to admit that you had posted wrong information. The splitter in a 15speed RR, being a classic case.
Nobody on this board knows everything, including you, we pool our knowledge and as a community are wize. You are continually trying to substantiate that your knowledge overwhelms that of the community, Don Quixote springs to mind.
I have never suffered fools gladly, but then Iāve never considered a lack of knowledge as the mark of a fool, for none of us were born with knowledge. A fool is one who cannot accept that someone else has knowledge, that they are willing to share, as that would be admission that they alone were not the keeper of all knowledge.
I have nothing but the greatest respect and admiration for the members with the ability to merely roll their eyes and scroll on past your condecending input, trying to bully your way through the forum. I made a resolution a month ago, to try to take a leaf from those patient folksā book, alas, try as I did, I cannot abide fools.
Now, back to that fifteen speed RoadRangerā¦
Oh yes! Opposed piston 2T Deltic diesel. Piston ported and mechanical supercharger.
Another example of an engine that cannot work without having the spent gases pushed out of the cylinder by higher tham atmospheric pressure on the inlet side.
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The exhaust gases do not leave behind any sort of vacuum. The gases will move towards any lower pressure area. They do not know which port is open first or second.
If the exhaust gasses donāt know which port is open first then how does a 4 stroke not push itās exhaust out of the inlet valves on valve overlap and if the outgoing gasses donāt leave behind a lower pressure than atmospheric then how do you account for scavenging of a two stroke and in the case of a 4 stroke manifold exhaust extractor design which agIn uses the principle of scavenging.
Your ideas have no reference or place for exhaust scavenging which is how a two stroke works the blower is just there to augment it.The exhaust gas pressure is way above atmospheric pressure and the blower is not there to compress the inlet air charge above atmospheric let alone above exhaust gas pressure.
Itās working on the principle of exhaust gas scavenging as the way above atmospheric pressure exhaust gases rush out of the open exhaust valves also containing more thanbenough energy to spin up a turbocharger or two on its way.
Itās clear who is resorting to personal attacks to cover up lack of knowledge and it clearly aināt me.
You think that a Detroit two stroke blower is there to āāmove the exhaust gassesāā, not assist the actions of the scavenging effect of the exhaust gasses as they leave the cylinder and youāve got the nerve to call me a cabbage.
How bleedin so when the exhaust gasses are already well on their way out of the cylinder, through the open exhaust valves, before the inlet port is even uncovered and open.At which point when itās uncovered the cylinder contains a virtual vacuum dragging in the new charge, from the scavenging effect of the evacuating/evacuated cylinder.
So weāve got Franglais who thinks that a turbocharger will choke the exhaust flow and SDU who thinks that the blower is there to blow out the exhaust gasses.
Point 1: itās not personal attack, itās simply saying it like it is.
Point 2: I missesd the bit where he says which gears are split, please elaborate.
You cannot dig your way out of this with a random crap YouTube clip.
BTW, heās made that far more complicated than it needs to be, mind you itās probably impressed you as you have no idea how to properly use a 15, having never seen one.
So Mr. C, now you are reading, or more accurately misreading my mind.
For all intents and purposes it is, itās certainly not there for decoration. Since the inception of the discussion Iāve been waiting for you to mention the pertinent point, how the blower, pump, supercharger, call it whichever of the common terms used, actually removes the hot gas. Your failure to mention that it is the crankcase pressure that is increased clearly demonstrates that you are merely regurgitating Googled information, without really understanding it.
Now, before you go sulking off again, you forgot to tell us which Detroit product you actually used, as opposed to played with as a test pilot. 
Please dont say Allison, Iāll pi55 myself laughing. 
He didnāt make it complicated at all he just expects you to understand the difference between a range change and a splitter which you obviously donāt.
Just like you donāt understand the difference between naturally aspirated v forced induction two stroke, let alone having the slightest clue as to how a two stroke Detroit works.With the idea of the exhaust being more than capable of rushing out of the open valves without help and scavenging the inlet charge behind it obviously being totally unfathomable to you.
Have you used or even seen a 15 speed RoadRanger? Thereās your comprehension problem letting you down again. He made it more complicated than it is, is what I said.
WHICH GEARS ARE SPLIT?
Amazingly, you post random crap to muddy the flow of conversation, in an attempt to deflect from your chasm of knowledge or to evade embarrassing questions, to which you have no answer due to lack of knowledge.
**WHICH GEARS ARE SPLIT? **
Tell us more about the principle of how ācrank case pressureā supposedly has anything whatsoever to do with removing the exhaust gasses from a Detroit two stroke or for that matter bringing in the charge on the induction side.
The fact is in this case N means what it says.The exhaust isnāt assisted because it doesnāt need to be.In fact it rushes out of the cylinder when the exhaust valves are opened with sufficient energy to drive a turbocharger or two and pull in the new charge of air behind it in the evacuated cylinder when the induction port is opened by the piston.Yes the blower helps in that regard in situations of compromised scavenging effect.
The blower has nothing to do with driving out the exhaust gasses.
Define crankcase and what the zb it has to do with any of that.
You mean you chose to miss the bit where it clearly refers to the deep reduction side of the box being splitter controlled in the low range.
You say you drove a twin turbo Detroit two stroke.But you think that it was supercharged by the same blower which N variants have and which you also think iss also there to blow out the exhaust gasses.
While Franglais thinks that the turbos just bung up the exhaust flow created by the blower which you clearly donāt disagree with.