I was reading the diesel power mag at work today and they have an article in there about Banks did a super/ turbo motor in a rig. It used a whipple twin screw that was fed by a turbo. I know people on here say the turbo boost will be restricted due to the supercharger. It does make sense, but why are they as well as others they reference able to do it and not us? Is it because it's a diesel?
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It's certainly doable. And it's a lot easier to do on a larger displacement engine like that, where you're going to make a lot more power on less boost. On smaller engines that people put in Fieros, it's a waste of time and money, because tuning it is a pain, and it's not cheap or easy to fit.
You have a much larger tuning "window" with something that big. You don't necessarily have to be incredibly precise on tuning to make power and potentially some corners can be cut or you can make a large amount of power gains, while still losing some potential gains and it not being a very big deal.
With a standard gasoline lower-duty engine like in most every car the tuning window is very small and typically dependent on very specific factors. By dependent, I mean that usually if you say have to push more fuel to a certain amount you have to have very specific supporting modifications for a very specific tunable range. Hence why these and others factors usually combine to make something like this be not only difficult but also potentially cost ineffective. The other thing to consider is one can make very strong power gains on just one specific application - turbocharger-specific or supercharger-specific. Tuning thus becomes focused on reaching a specific power value, and then advancing from there if such is desired to another window of tune-ability.
Detroit Diesel had an entire line of engines that were twin charged as OEM equipment... The twin charged concept has merits depending on the application.
Not sure the size of the engine is that important... historically it's the rev range (or lack thereof) that makes twincharging desirable... the bigger the rev range, the more desirable it is. VW has a production twincharged 1.4l, and has for many years, for example. High redline combined with relatively modest power goals and high responsiveness is about the ideal scenario for twincharging...
Why would tuning be any worse? I wouldn't mind as I have a turbo sitting on the shelf.
Its not.
There is some speculation that it helps to introduce a supercharger bypass as the turbo flow overcomes SC flow to increase the blower/turbo efficiency lambda. Under 500whp I doubt you would need to be concerned with this. The physics of twin charging is very forgiving and easy to calculate... That being the math shows favorable efficiency on both the turbo and the blower if you have a moderate to large sized turbo.
Why would tuning be any worse? I wouldn't mind as I have a turbo sitting on the shelf.
Its not.
There is some speculation that it helps to introduce a supercharger bypass as the turbo flow overcomes SC flow to increase the blower/turbo efficiency lambda. Under 500whp I doubt you would need to be concerned with this. The physics of twin charging is very forgiving and easy to calculate... That being the math shows favorable efficiency on both the turbo and the blower if you have a moderate to large sized turbo.
I was reading that in dealing with the heat issue of being twin charged, someone had suggested but no answer, lowering the boost at the supercharger from the stock 3.8 to a 4.0 and use a larger turbo. The theory is that there's less heat generated from 4 psi vs 8 psi. Here's the link
Ehhh.. He is pretty far off base for the most part.
The eaton blower doesnt "make boost" Its just a blower that doesnt let air back out of where it just put it... it makes compression inside of the lower intake manifold... so if there is no pressure to make, aka its 15psi above and below the blower, you effectively have zero load on the blower. The bigger pulley is just an idea that underdriving the blower may gain you a half a horsepower due to less rotating mass.
Eventually the turbo will be held back by the supercharger. It becomes a parasitic at high rpm.
Not necessarily true. It depends on several variables, and in any case where it is true, the blower is already a hindrance to performance at that RPM by itself, as it would be a restriction to air flow regardless of whether there's a turbo before the blower or not.
As long as the blower can flow enough CFM to fill the needs of the engine's displacement at any given RPM, it will not be a restriction or parasitic, regardless of whether it is compressing air. It will simply plateau and stop adding power. Turbochargers are also afflicted with compressive limits, and if the cold side is unable to flow enough air to meet the needs of an engine at a given RPM, will also become a restriction at that RPM.
Even a tiny turbo like the ones on a stock Eclipse or an Audi can hit about 25 to 30lbs of boost before they become inefficient. The same is not true for a supercharger either roots or centrifugal. I have heard of a 650 hp Lotus Elise that is twin charged. It's on YouTube.
Originally posted by Spiders1: Even a tiny turbo like the ones on a stock Eclipse or an Audi can hit about 25 to 30lbs of boost before they become inefficient. The same is not true for a supercharger either roots or centrifugal. I have heard of a 650 hp Lotus Elise that is twin charged. It's on YouTube.
PSI is irrelevant in terms of flow. 600 PSI or 10 PSI at 300 CFM is still only flowing at 300 CFM. If you're only capable flowing 300 CFM at any RPM where the engine needs more than that to remain efficient and make power, you're a restriction. For an engine to continue making power at higher RPMs, you need to be able to flow enough air into and out of the cylinder, for it to make that power (along with the fuel and spark requirements). The only thing adding PSI via boost does, is increase the pressure inside the cylinder, so that you make more power than you would at a lower cylinder pressure.
Eventually the turbo will be held back by the supercharger. It becomes a parasitic at high rpm.
Completely wrong. The blower works on pressure ratio, and as long as there is none, there is no blower. Its "parasitic" only in the form of rotating mass.
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As long as the blower can flow enough CFM to fill the needs of the engine's displacement at any given RPM, it will not be a restriction or parasitic, regardless of whether it is compressing air. It will simply plateau and stop adding power. Turbochargers are also afflicted with compressive limits, and if the cold side is unable to flow enough air to meet the needs of an engine at a given RPM, will also become a restriction at that RPM.
Wrong again. This is true of a dual compressor setup, but not this one. The blower "displacement" scales directly with the pressure coming into the turbo.. so technically at 14psi of boost, the blower has an effective displacement of an "m180" blower instead of a "m90".
When charging the supercharger with air from the turbo, you allow the super to work less harder in a sence claiming the loss in HP robbed from parasitic loss due to the belt.
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