Has anyone tried rear mounted turbo?

[Wanggot]

Saw this ISF using a rear mounted turbo. I'm not a turbo fan. But kinda interested how the system works. Your comments are most welcomed. Thank you.

Lexus ISF Twin Turbo In Car Drive Loud Revs SICK!! - YouTube

Check out this manufacturer

STSTurbo.com: Why Rear-mount Turbo

 

[Keninshiro]

I checked out STS's web site for more info on the new turbo mounting position... the application left me with a lot more questions than answers.

Although rear mounted turbo have its benefits of being exposed to the elements (lower running temperature, faster cooling time etc) but what puzzles me more is that does this application only suitable for very dry places? Like Vegas? Reason being I'd hate to drive under heavy rain or light flood for the fear of the turbo housing cracking from extreme temperature changes (What about snow? Rain fall in winter?). What about the air filter? From STS web site it looks like it's located under the under carriage as well? What happens if you drive over a large pool of water? Malaysia is known for its fierce raining season and having the turbo under your car doesn't really help. Further more, locating the turbo unit and air filter under the car expose them to A LOT OF DIRT... I'd hate to think a small pebble somehow found it's way into your turbo housing... BOOM! What about cars that are lowered? Scrapping turbo... anyone? Don't forget that regular roads are not your race track... there are a lot of stones ranging from all sizes that constantly bombards your under carriage... imagine a large stone got suck under and whacks your expensive turbo or your piping or your waste gate? More dangerously, damaging oil lines for your turbo... alamak! :D Last but not least, there are a large amount of pipe length to fill up to build enough pressure for the boost to kick in... by then your opponents Vtec already long kicked in and gone yo!

Don't get me wrong... I like innovation and forward/fresh thinking of doing things but there ARE reasons why things are done in a certain way... because they work! Mounting the turbo behind feels like reinventing the wheel. :p

Just my 2 cents.
Eric.

 

[TitanRev]

Very nice and interesting....wish to see it in real and try the performance....

 

[4gbanger]

this is crap.. just a gimick.. u have to do the intercooler pipe all the way back to front. i'm sure the lag is like the end of rpm.. hehe

 

[l2s_turbo]

It's really new to me... how come intercooler piping so long.. no lag meh???

 

[LittleWhiteWagon]

this is crap.. just a gimick.. u have to do the intercooler pipe all the way back to front. i'm sure the lag is like the end of rpm.. hehe

It's crap, a gimmick, but everyone running it says it's good. Must be something wrong with Malaysian's la.

You make it sound like they chose turbos the size of a head for each bank of cylinders and as if the gas coming into it is ice-cold and coming out the same. Exhaust gasses (i'm saying this without the variables of weather include) will always remain hot. Hot gas = less dense than cold gas. You think or not the gasses will be hot where the turbo is being used instead as a muffler?

You imagine la instead of a S-Flow or Straight through muffler where the gas can finally escape you put the turbo's hot side there ngam ngam blocking the whole flow from your exhaust port through the exhaust and right to the back of the car. Even when the engine starts there will always be pressure on the hotside inducer. Instead of just a short turbo manifold trying to spool a turbo you now have a manifold that it's only job is just to flow as much gas straight to the rear and within the whole exhaust it is now gas filling. The whole length of the piping is now full of gas from front to back due to the hotside blocking the last remaining exit. You're saying that there will be less gas in total volume than 4 runners of a super short manifold?

And lag don't tell me la there's only one diameter size in the world for intercooler piping right... If you use a smaller diameter gasses fill the surface area faster, and through thermal dissipation where heat exits through the walls of the long return pipe due to the whole thing being exposed to air under the car, you really think there is going to be tons of lag?

However the vulnerability of it lasting and being exposed to weather, that I can completely agree on. Like water and stones. But smacking into it... the majority of pictures there are on the internet they're mounted deep in the chassis, same level as the bottom of the spare wheel area where a muffler sits. Return pipes are the along the chassis rails which I agree will be smashed if the car is into stance. Return and feel oil and water lines how big are they la really? 3" in diameter? Last I remember -4AN feed and -12 return lines not being that hard to mount them at the same height as your solid brake lines or higher than the chassis rails which... I highly doubt any forumers here have bottomed out on their brake lines consistently, or even at all.. The hotside pipes are well kept in the tunnel meant for origanal twin pipes (if it's used on a V engined car), the only thing that dangles rather low from just glancing at pics is really just the coldside piping.

Plus i'm sure the people who designed this have the common sense to actually calculate the flow rates of everything before slapping a kit together to sports cars. Don't la condemn things so quickly without actually analyzing it critically. Not everyone has enough space to mount front mounted turbos.

And if the owners want to go through the hassle of installing all the things needed why not? An external oil and return pump for the oil & water, mounting all the brackets, people like STS use try to innovate something instead of just throwing the whole idea away unlike the majority of us (myself included) where would normally just copy an ancient way of doing things just because we don't fully understand it, but we want something.

Anyways i'd like to conclude by saying if you don't understand the science behind it, there really isn't any harm is learning a bit without dismissing the idea entirely. It's not the 80's anymore where computers are still inefficient and where engineering is a course in a college where only a few can take. I used to be a very skeptical person also until I started to do my own research on why & how things work.

 

[Keninshiro]

Indeed mechanical engineering is not something you need to major in order to understand how things work but there is this little bit where you missed out... common sense. There's no denying STS folks have came out with something "interesting" rather than ground breaking... honestly, no one knows how well this will pick up... if it does, you can laugh at us who posted negative remarks... but if it fades, what's next? Seriously, do you think big boys in DTM, BTCC, JGTC have not ponder on this yonks ago?

OK, let's talk engineering now. Here's a simple analogy to your long essay... which straw fills up water quicker? Long or Short? The fastest cars have the shortest turbo housing route because the shorter the length, the quicker the reaction... no need to explain all those mumbo jumbo large and small diameter piping. Ever heard of scavenging effect? Hot gasses speeds up velocity. By having a long pipe length underneath the undercarriage cools down the returning spend gas needed to spool the turbo... the effect is more apparent during rain or in cold weather country. Your explanation of how gas accumulates in the pipe left me speechless... Turbo lag regardless has everything to do with the length/diameter of the pipes hence why twin turbo back in the days and twin scroll turbo now were invented to counter that effect. Air volume is the determine factor for turbo lag, just like the comparison of long and short straw. Btw, how many cars have you encountered have deep undercarriage area for you to mount that much piping under? Or this set-up is only for a selected few?

Everyone can be sceptical and rightly so until proven other wise... and that applies to you as well.

 

[LittleWhiteWagon]

Indeed mechanical engineering is not something you need to major in order to understand how things work but there is this little bit where you missed out... common sense. There's no denying STS folks have came out with something "interesting" rather than ground breaking... honestly, no one knows how well this will pick up... if it does, you can laugh at us who posted negative remarks... but if it fades, what's next? Seriously, do you think big boys in DTM, BTCC, JGTC have not ponder on this yonks ago?

OK, let's talk engineering now. Here's a simple analogy to your long essay... which straw fills up water quicker? Long or Short? The fastest cars haweather country. Your explanation of how gas accumulates in the pipe left me speechless... Turbo lagve the shortest turbo housing route because the shorter the length, the quicker the reaction... no need to explain all those mumbo jumbo large and small diameter piping. Ever heard of scavenging effect? Hot gasses speeds up velocity. By having a long pipe length underneath the undercarriage cools down the returning spend gas needed to spool the turbo... the effect is more apparent during rain or in cold regardless has everything to do with the length/diameter of the pipes hence why twin turbo back in the days and twin scroll turbo now were invented to counter that effect. Air volume is the determine factor for turbo lag, just like the comparison of long and short straw. Btw, how many cars have you encountered have deep undercarriage area for you to mount that much piping under? Or this set-up is only for a selected few?


Everyone can be sceptical and rightly so until proven other wise... and that applies to you as well.

Well if it fades, at least we know how to turbocharge a car with a cramp engine bay! And no I don't really see the point of laughing at skeptics or not, I just wish it would be analyzed with more thought. But that's just me la.

Definitely a shorter straw fills up faster, but the diameter does play an affect as well. Scavenging is such a loose statement, how hot do you want the gas to be? Heat alone isn't all la.

Hot gasses don't speed up velocity, it just makes the air less dense than cold air. If hot air alone makes gas flow easily hot-air balloons should be the world fastest method of travel, but they don't, because they still rely on wind to blow them in the direction they want. That's where your point comes in, the design of the turbo. The same way 2 turbochargers of the same size but from 2 different eras can make 2 different power levels? Why? Engineering. I'm not a borg-warner or garrett engineer so I can't say what makes so much a diffference. I don't need to write mumbo jumbo about bi-turbo setups or compound charging or anything either.

Last I remember twin scroll turbos are designed to separate pulses of gas from colliding before entering the hotside, but oh well the debate isn't there. I'm not well versed on twin-scrolls anyway.

Looks like I didn't mention this in my 1st reply: To cars that come factory with V-engines and run separate exhausts per bank. Especially older American cars that STS seem to cater more towards that still uses chassis rails. I don't think I need to list how many cars have deep undercarriage areas because you can see it for yourself.

However if I said all this could be crammed under a kancil floorpan with no issues whatsoever than that's my fault la.

Lastly for DTM, BTCC, JGTC, do you really think they have issue in cranking power out of their engines, worrying whether the car can drive to 7-11 to buy milk and whether it can run pump gas? Yeah neither do I. They're free to do whatever they can within specified regulations. They're not road cars.

If were going to start comparing pure race cars of that caliber to a couple of V8 guys who turbocharge their cars, i'm leaving. Whole different ball game entirely.

 

[stupidcar]

At first I thought its a rear engined car something.
Hmm, we(Malaysians) are too ulu to know about this setup ahahha.

 

[LittleWhiteWagon]

At first I thought its a rear engined car something.
Hmm, we(Malaysians) are too ulu to know about this setup ahahha.

It's a pretty interesting subject though.

 

[Veloc]

Turbo needs high energy air to drive. High velocity which usually occurs with high temperature. Very much like exhaust gases that just escaped the combustion chamber. I have also heard of this remote turbo. I haven't tried it but honestly i have doubts from a theoretical point of view.

 

[stupidcar]

It's a pretty interesting subject though.

Yeap. Immediately Googled haha

 

[vr2turbo]

At first I thought its a rear engined car something.
Hmm, we(Malaysians) are too ulu to know about this setup ahahha.

Well, it depends. Would not say it is good or not, but then everything have it's pros and cons, right?
Well, like first mentioned, it is fitted because engine compartment got no space so this is the pros for this system, but then if you have space in the engine you would not use this system....

 

[Keninshiro]

LOL... I fail to see your argument on hot gases (or maybe it's just us Malaysians), especially with hot air ballon... that one was a classic. Hot air ballon's PRIMARY intention was invented as a means to go upwards, moving forward relies on wind! Propulsion is a totally different subject but even then, moving forward like a jet or rocket (the fastest mechanical thing on earth) still needs super hot air (velocity, remember?) burned by fuel to move them forward, no? Hence the topic of hot gases is VERY relevant when it comes to turbo setup. The hotter the air, the more velocity it carries hence spooling the turbo at much higher speed. How hot do we want the exhaust gas to be? Like you I'm no turbo engineer but I know each turbo design has their own specific optimum gas temperature to operate... too hot, you'll start melting the turbo blades... that is another engineering topic on tuning and metallurgy.

We don't have to be well versed on anything, but at least get the basic right. Internet is a very useful tool nowadays and a quick search on wiki can tell you the basic mechanical works of a twin scroll turbo (I know, my WRX sti uses one):

"Twin-scroll or divided turbochargers have two exhaust gas inlets and two nozzles, a smaller sharper angled one for quick response and a larger less angled one for peak performance.
With high-performance camshaft timing, exhaust valves in different cylinders can open at the same time, overlapping at the end of the power stroke in one cylinder and the end of exhaust stroke in another. In twin-scroll designs, the exhaust manifold physically separates the channels for cylinders that can interfere with each other, so that the pulsating exhaust gasses flow through separate spirals (scrolls). This lets the engine efficiently use exhaust scavenging techniques, which decreases exhaust gas temperatures and NOx emissions, improves turbine efficiency, and reduces turbo lag."

If the setup is for cramped engine bays (V6 and above), how did Nissan R35 cram so much in its bay and still be so powerful and efficient? Again it is about engineering and design... above all, what really works.

No we're not comparing race cars with daily drivers... I'm using race cars as an example of how race technology trickles down to actual production cars. A lot of car manufacturers uses race cars to carry their second or future technology research... hence my argument that if this rear-turbo is such a ground breaking design, it would have at least landed on 1 or 2 models many years ago but why aren't we seeing it? STS engineers are a lot smarter than all the motor industry put together? I think not. No doubt the rear-turbo is nice solution to a lot of turbo problems but it isn't with its flaws... so yeah, from an engineering point of view... a nice novelty idea... realistically, you tell me.

 

[D7zul]

Why rear mounted turbo? Because there's no space at d front