hellbents10

iTrader: (10)

Something is not correct on that 670whp dyno run. Being the dyno or the boost gauge has a kink in the line going to it.

LT1-7

as far as peak hp, I wouldn't imagine you would see too much loss going rear mount. Where you would see some major changes is spool time. I mean you put two cars on the dyno both running 10psi. Both cars will put out about the same to the ground. But that's just with a small turbo. Try sticking a T88 or even a T76 back there. You might not even be able to reach full potential boost. That's why all the rear mount turbos have p-trim exhaust wheels.

We built a hot parts kits for a customer who has a rear mount kit with a T70. He wanted to use the same turbo just with our hot parts. His full boost came from 5000rpms to about 2000rpms.

Like Jose said, good for a low hp/street setup. Anymore than that and you just won't be happy with it

MNC5

Actually all other things being equal the turbo being powered by lower temp air would make more power.

Heat doesn't power the turbo

F8L Z71

IMO HP PEAK would be the same...


Now which would be faster at the track? Probably the front mount unless the rear-mount had a 4000rpm stall, then it could be equal

True heat alone doesn't spool the turbo but it sure does help A LOT!! If my truck is cold I can't even boost over 3psi off the line when i can normally get 6-7psi.



BTW, thanks Jose. You know I'll be giving you a call if my current setup doesn't produce the #s I want and I need to put the turbo up front.

LT1-7

Obviously heat alone does not make anything spin. The hotter the exhaust gasses the more velocity it has. The more velocity it has, the faster it can spin a turbine wheel. So no, heat does not power a turbo. It just makes everything move faster.

mzoomora

iTrader: (36)

Another part of the heat thing to consider is that hot air is less dense, therefore has a larger volume. I would think that if you had a larger volume of air(less dense) passing thorugh a turbo it would help it spool faster. The bad part would be all that extra heat tranferred to the cold side of the turbo.
Also, if you look at a lot almost all cars being produced now they all hae the muffler as far back as possible because it poses the least amount of backpressure there due the more dense air. I would also think that the turbo would also pose less of a restriction when in the rear also.
I am just speculating, but it all makes sense to me.

89FormulaLS2

iTrader: (1)

That makes a lot of sense to me, also.

Dustin Mustangs

Um, sorry...you just failed thermodynamics. The volume of air coming out your exhaust port is much greater then the volume of air going in your intake port. If it wasn't for this fact a turbo would do nothing but be a restriction to flow (ala the conservation of mass principle).

Why is the volume greater on the way out??

HEAT

The closer these two temps are to each other the less of an effect a turbo will have on power production. So, actually both statements you made were wrong. If you aren't following I'd be glad to dumb this up even more for you.

SINISTER

iTrader: (16)

x2
sounds like alot of bench racing to me...

BrNoUt377S10

if you were going to do a comparison between 2 turbos 1 powered by cold air, another by the regular 1200 deg exhaust gases, the regular turbo on the exhaust manifold will perform better because of the hot air since it is much less dense than cold. You are correct Dustin Mustangs but the way you came across with your information you made it sound like just regular hot air, like if it was 1200 Deg outside that it would spool the turbo. Heat alone will not power it, it just greatly increases its efficiency to make power. Is that not correct?

Cyborg

iTrader: (8)

2 STS GTO's ran 11.092@122mph and 11.098@127 mph respectively at E-Town last weekend. They were both booted for no cage and didn't get to show what they can do. It's only March- these cars aren't even dialed in yet (obviously since they didn't have cages)....and people continue to say the STS is only good for the street and can't perform at the track. People just ignore the results I guess...people just believe what they want to believe...funny stuff

ktmrider

I think everyone is right, but the statement by Dustin with (mainly) is kinda generic. Sure, a front mount is ultimately more efficient under most conditions but not like he makes it sound. The boost "delay" from the compressor housing to the intake is like 0.05 seconds on the longest model. Also when you are talking low boost levels ( like us street V8 folks running less than 10psi ) most of the exhaust energy is being diverted thru the wastegate anyways.
Thanks for "dumbing" things up for yourself and others there Dustin, especially with 27 posts at this time....course the Mustang in your signature explains a lot.

Dustin Mustangs

Sorry, I didn't realize that your post count is how people judge your intelligence around here. What was I thinking? Hold on, let me go crumple up and throw away my engineering degree.

And what mustang are you talking about?? Last time I checked I didn't have one. I didn't even attach my sig to this post, wtf??? And by the way, nothing I said had anything to do with delay. That's a whole other story.

People, our engines are just glorified air pumps that make use of what they pump on the way through. The better they can pump air the more power they can make. All they do is move air into the combustion chamber, use the oxygen in the air to burn what ever fuel your running, and then move it out to make room for more. The combustion that happens on the way through makes the power but also adds heat which increases the volume of said air. If this didn't happen a turbo would do NOTHING but slow you down. Around 1/3 of the energy released by combustion is lost out the tail pipe. What form is this energy in?? Heat!! The only other form of energy in your exhaust is the kinetic energy due to its velocity. But remember, if the air wasn't heated on the way through, this kinetic energy would be the same in as out. So I am just wondering how you are going to add more energy to a system then is available?? Oh don't forget about the inevitable flow restrictions and parasitic drag.

I don't know why I am even bothering... all of these sts threads go down in flames the exact same way...but what do I know I only have 27 posts. Wait, make that 28, Booh-Ya!

Dustin Mustangs

You, unlike others, actually followed what I said. The only thing maybe I didn't convey to you clearly is that it isn't just the temp of the exhaust that powers the turbo, but how much hotter it is then what it's trying to pump. It's this temperature differential that sts owners loose a SMALL amount of. As all of them will argue to the death, it's not really enough to worry about for a street car.

mimic42100

gogogadgetcar

I think putting the turbo in the back is just being lazy J/K

if you can make boost off the line with a rearmounted system the lag probably isn't an issue durring drag racing, what I would be concerned with is if you wanted a peppy car on the sreet.

Those GTO's that are kick'n @$$ with the STS, are they both automatics? How well do the M6 cars 1/4 mile?

BrNoUt377S10

an STS on a regular, daily driven street car is great, makes great power for the use of the vehicle. But on a race vehicle yes, a conventional front mount would work the best if your looking for the performance/efficiency out of the turbo(s). STS is IMO, just a good healthy way of getting streetable HP out of your ride without taking all of the under-hood space and keeping the underhood temps down as well. The subject of STS vs conventional will always be around and people will always have differing answers, just like the chevy vs ford vs dodge etc.. etc... Every issue in the history of man has not been 100% totally agreed on by everyone and it never will since everyone will have a different point of view of everything.... just my .02

PurEvl

iTrader: (2)

there isnt a front mount setup im worried about ( in the same boost/turbo league) I have proven time and time again with various front mount graphs vs my graph that they infact peeked the same as me and some barely before. This is the deadest horse on the planet.

Foxxtron

iTrader: (1)

Not to further the argument of physics here, but from what I know in college physics, and what another website's information confirms, corresponds with what DustinMustangs said. Not heat alone, but rather the heated gas from the combusted fuel which creates this gas having lower mass over a higher volume (as compared to the standard air temperature of the outside air).

The force of individual moving particles in a space containing the gas would add up to considerable pressure. As the gas expands, its pressure decreases, since there are fewer particles in any given area to collide with anything. A gas applies much greater pressure when it is compressed into a relatively small space because there are many more particles moving around in a given area.The route from the outside of the exhaust valve through the exhaust tubing to the turbine blade before exiting the turbine is what compresses the gas, thus creates this higher pressure inside of the turbine chamber that the gas turbine needs to operate efficiently.

So basically if you were pushing standard atmospheric pressure air, or MUCH cooler exhaust gasses over the turbine, it wouldn't operate as efficiently. Heat is what makes the exhaust gasses expand, and the containment of the gasses pressurises the gasses.

http://auto.howstuffworks.com/turbo4.htm

then click on the link where they mention works like a gas turbine system:

http://travel.howstuffworks.com/turbine1.htm

From a scientific viewpoint, the target market for the rear-mount turbo is the aftermarket sector where people want to use less labour to install a turbocharger. If finance, downtime, and complexity aren't a major concern, then a reliable front mounted turbo would be the method with greater exhaust gas efficiency, but if you have to rely on expensive labour, then the rear-mount turbo would prove to be a considerable option.

BoostedToy

Like Jose stated, I believe the STS is a nice option for those on a budget and are not wanting optimal performance. However...I have a problem with the claims of the manufacturer (i'm not going to throw out the title of engineer in this case) of the kit.

STS happens to have some absolutely false claims on their website as well.
"A remote mounted turbo runs cooler, with no additional lag and requires no major modifications to your vehicle." http://www.ststurbo.com/remote_mounting___


"Denser exhaust gasses drive the turbo turbine wheel more efficiently."
-
Are you kidding me? Sure they are denser, by the time they have made it through 13' of piping to the turbine housing, they've lost 300-500 degrees of exhaust temperature. Along the way, losing a significant amount of spool energy. That logic is pure bunk. Sure it'd be nicer to have a little bit cooler (hence, more dense) intake/charge air temps, but on the exhaust side...sure, makes sense? Wouldn't you rather have 1150-1200F exhaust temps, and having them still expanding at the point of your exhaust housing? ---

Hmmm...maybe we should start throwing an intercooler in between our typical turbo kit headers and the turbine housing on our turbos to yield these seemingly beneficial "cooler, denser exhaust gases".


I've had a thermodynamics class and also understand some fluid dynamics. All I have to do is look at this...

http://www.ststurbo.com/inc/iview/461?idx=5&p=7547

That says more than I could ever explain as far as efficiency and the above claims.