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Discussion Starter #1 (Edited)
Just got back from the bookstore and noticed a new type of turbo on the cover of Turbo magazine (don't scoff, it caught my eye)...there is a company experimenting with mounting the turbo under the car off of the exhaust, right before the muffler...not under the hood/engine cover. The company is STS and the website is http://www.ststurbo.com/how_it_works
Many have stated that the engine/firewall/header locations all could prevent effective turbocharging. Well, no manifold is necessary and it looks like it could be a pretty clean installation. Not arguing the merits of the kit, but it looks like it could really work. Maybe this has been around for a while, but it is the first time I have seen it in my 31 years! Just thought I would throw this out there and see what people thought (high CR , "weak rods" and warranty aside of course)!
 

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I believe somebody here (OneFastLotus, maybe?) had posted pictures of a turbo mounted under a car before. You would certainly want to make sure that you don't park your car where there are dry leafs laying around. :eek:
 

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Not much space under the car, plus it'd have to fit and still allow mounting the undertray.

As I recall Nick at the LA show said cooling was a big issue with turbocharging the car, and they'd had to really beef up heatshielding just going to the yota motor.
Chris
 

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Discussion Starter #6
Why so much lag? The piping could be made pretty short considering the mid-engine design. I would also think that this setup would require less associated piping length due to the fact that there is no intercooler to pass through. Well, less than a normally mounted turbo with intercooler in a Miata would. With the right turbo and boost, there really should not be that much lag.
 

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Two things are important when considering turbo mounting locations:

1. The turbo must be mounted above the oil pan so that oil exiting the turbo can flow downhill back into the pan and not pool in the lines. Oil exiting the turbo is not pressurized--it depends on gravity to flow.

2. The turbo should be mounted as closely to the exhaust ports as possible. Heat drives the turbo, so the closer to the exhaust ports it is, the more heat is present in the system.

AFAIK, physical location and orientation don't matter too much as long as the above rules are followed.

Jim
 

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Isn't the 2zz-ge a returnless fuel system anyway, making turbo aplications even more difficult?

I think the only available power added is a supercharger, and so far, three isn't one that will work. Darn it!
 

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Discussion Starter #9
jtanner said:
Two things are important when considering turbo mounting locations:

1. The turbo must be mounted above the oil pan so that oil exiting the turbo can flow downhill back into the pan and not pool in the lines. Oil exiting the turbo is not pressurized--it depends on gravity to flow.

2. The turbo should be mounted as closely to the exhaust ports as possible. Heat drives the turbo, so the closer to the exhaust ports it is, the more heat is present in the system.

AFAIK, physical location and orientation don't matter too much as long as the above rules are followed.

Jim
The first issue is solved by using an electric oil pump to send the oil back to the engine, not the pan. And regarding the second statement...exhaust gases spin the turbo, not heat. I don't really understand this point.
 

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petergibbons said:
And regarding the second statement...exhaust gases spin the turbo, not heat. I don't really understand this point.
Very simply, as the exhaust gas cools, its pressure drops. Lower pressure = less work done by the turbo. The heat of the exhaust is a source of energy. The more heat lost to cooling and expansion, the less there is that gets used to run the turbo.
 

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Discussion Starter #11
Okay, got it. I had read this on the website:
No, heat doesn't create velocity. Heat creates volume. If you look at any of the physics laws for gasses, you will find that pressure and volume and heat are related. PV=NRT is a popular one, The V isn't for velocity, it is for Volume.
The turbine housing is what creates the velocity. The scrolling design that reduces the volume of the exhaust chamber as it scrolls around causes the gasses to have to increase in velocity and pressure to maintain the same flow rate.

Hotter gasses have more volume, thus requiring a higher A/R which in effect means that it starts at say 3" and scrolls down to approximately 1". Lower temperature gasses are denser and have less volume, so they require a lower A/R housing which would start at the same 3" volume, as the turbine housings use standard flanges, and scroll down to say 3/4".

I read it a little too quickly.
 

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THis system looks like it would work just fine (don't know that there would be room in the Elise), but as an earlier poster said...
L A G ! ! !

Probably a great addition to a truck used to haul stuff at higher altitudes (think Denver) where you have a steady need for power.

Scott
 

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the only advantage I see to this is that because it is located behind the catyltic converter, it's slightly more legal than modifying the bits between the exhuast ports and the cat (which is illegal in funny states like California).

other than that, I see no advantage to a system like that, other than maybe a location for the snail outside of the cramped engine bay.

fun to think about though. ;)
 

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This is a laggy setup. Similar approaches are used in some fixed, steady RPM setups where a certain RPM is maintained - hence no lag. Airplanes, trucks, water pumps might be such applications.
 

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petergibbons said:
The first issue is solved by using an electric oil pump to send the oil back to the engine, not the pan. And regarding the second statement...exhaust gases spin the turbo, not heat. I don't really understand this point.
The first issue is not just about getting the oil to return to the pan--you also don't want the oil to pool. If it pools, it might coke. Also, if it pools in the turbo itself, it will exert additional force on the seals and they will fail prematurely.

Otherwise, I think you've basically got it. A/R is Area/Radius. 'A' is the area of the housing (cone) where exhaust gasses exit onto the turbine. 'R' is the distance from the turbine shaft to the center section of the cone. You're right when you say that a smaller A/R ratio increases the velocity of the gasses. What you didn't mention is that it also creates backpressure at high volumes, which is why turbos with a smaller A/R are choked off at higher rpm.

Mandatory Lotus-related content: I would expect that if something got forced induction, it would be the Exige--there's just a lot more room around the engine to work with.

Jim
 
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