Remote mount turbo?

[vex]

Originally Posted by jerd_hambone

I wasn't trying to make a comparison. I just wanted to see if someone had done it.

And has already been answered.

I stated that it would be an effective way of giving an NA engine a bit of extra go. I said nothing about trying to get the most power out of an NA.

But then what about the turbo, manifolds, wiring harness, sensors, an exhaust to mate with the turbo manifolds, TII hood for going top mount, or a big front mount?

Nickle and dime, nickle and dime.

But look at it this way. Everyone used to say there was no way of getting power out of an NA FC. Everyone said it was impossible to turbo one without it blowing up within a few hundred miles.

But people still tried it and did it successfully.

Maybe the remote mount is the same way?

No one's saying that it won't work. It's the difference between less effective and effective. This exact thing was covered quite in-depth on my local forum.

Link Unfortunately you need to sign up to see that. For what it's worth here are some excerpts from it:

Obviously I'm going to say I'm not a fan, but they work. For a smaller engine like I have it wouldn't make much sense, but with a large engine it is allowable to have some loss, I'm sure it's still better than a supercharger. I guess I have a hard time believing things couldn't be shifted around to put the turbo up front, but I can't really say. I don't see how you can say they're super efficient though, depending on what you mean by efficient. You lose a lot of turbine-driving energy through the exhaust piping to the turbo which means you have to size the hot side smaller than normal to get the same spool, which therefore results in a more restrictive hot side. On the other hand, people report such good results with them that I can't down them.

HPBooks has a book out called "Street Turbocharging" written by Mark Warner, P.E. and it talks about rear mount turbos in a positive way. It's a decent book.

^Drives an SVO

Exactly larger engines have less loss from flowing exhaust air back 8 feet to the rear of the car than say an itty bitty 1.6 liter honda engine that can barely displace enough to spool a turbo right off the header. About all Ill comment on the subject till the end of the month.

^did a 600whp rear mount on a Vetter (C5 I think)

And where does this pressure differential pre-turbine and post-turbine come from? It come from expansion of the gasses.

Turbines are modeled as isentropic expansion devices. The energy in the exhaust is contained in the form of kinetic, heat (thermal), and a little bit of pulsations from each cylinder. Almost all the energy comes from heat--the expansion of the hot exhaust gasses in a turbine.

So maybe the turbine doesn't "care" if it is hot or not, but the energy spinning it's wheel is coming from the heat in the exhaust. Read a thermodynamics book instead of google.

^He's just an asshole... well, a smart asshole, but an asshole none-the-less

Jebus are you really that dense? Are you really implying that we are saying that egts entering a rear mounted turbo are the same temp as air entering the engine???

air enters at say 100F, exits at 1400F. So it cools down to 400F at a rear mounted setup. Heat is still being used to spin the turbo (and yes the turbo takes advantage of expanding gasses as heat energy as you said). Heat in the exhaust drives the turbo, but it really just complements the pressure that is already there.

Fuck...come take a ride in my turbo. I can spin up the turbo on a cold engine (using your "windmill" or whatever-you-call-it joke). Heat does play a major role...I'm just saying don't discount big airflow from big engines to small rear mounted turbos to overcome a moderate heat loss in a rear-mounted setup.

^Response to asshole, but raises some points one would need to consider.

I'm aware of that Semantics Man. What I was referring to was the fact that there's still a lot of free hydrocarbons in the exhaust that continue to burn (hence heating and expanding the exhaust) even after they've exited the exhaust ports. Some cars position the turbo so close to the head that there are still lots of free hydrocarbons in the exhaust even after it passes through the turbine, especially at higher rpm. This is wasted energy. Ideally you want to give the exhaust gas enough time to burn off all those hydrocarbons (hence "fully" expanding the exhaust) but not enough time to start to cool off, so the ideal place for the turbine inlet would be the hottest part of the exhaust stream where it would have the most available energy, both thermal and kinetic.

I'm not arguing this point anyway, all I'm saying is that if you can reduce the amount of heat lost through the piping, you can reduce the amount of energy lost by moving the turbo farther downstream. The turbo still works, and works well, just not AS well as having it at the optimum position farther upstream, but it's a compromise, just like everything else.

^He was the OP

Depending on the application, there's enough exposed piping on the trip back up to the engine to sufficiently cool a moderately compressed (say sub 6 psi) air charge. Some applications (like TT rear mount vettes) use a front mount intercooler because they don't have enough pipe, and enough air flow around that pipe, to cool it, but a lot of the truck setups do because they're longer and the pipe is run usually right beside the frame rail.

^OP Again

I'd take the faster spool over the increased top end any day, but if you have >3.0L chances are you have sufficient power until the turbo spools to start with.

Just to comment on the heat issue, the fastest spooling header setup for a WRX/STi is STOCK because of it being cast iron and maintaining heat better than any of the aftermarket designs. It doesn't make quite as much power up top as the equal length designs, but is does have much better spool (read: over 500rpm compared to some of the headers). So what have we learned children? In real life, where you burn engineering textbooks, heat effects spool, not overall power output. Now everybody go throw out your tampons and move on to a different aspect of this setup.

^2007 SCCA Prosolo National Champion- D-Stock in a 2006 WRX

[vex]

Originally Posted by jerd_hambone

I wasn't trying to make a comparison. I just wanted to see if someone had done it.

And has already been answered.

I stated that it would be an effective way of giving an NA engine a bit of extra go. I said nothing about trying to get the most power out of an NA.

But then what about the turbo, manifolds, wiring harness, sensors, an exhaust to mate with the turbo manifolds, TII hood for going top mount, or a big front mount?

Nickle and dime, nickle and dime.

But look at it this way. Everyone used to say there was no way of getting power out of an NA FC. Everyone said it was impossible to turbo one without it blowing up within a few hundred miles.

But people still tried it and did it successfully.

Maybe the remote mount is the same way?

No one's saying that it won't work. It's the difference between less effective and effective. This exact thing was covered quite in-depth on my local forum.

Link Unfortunately you need to sign up to see that. For what it's worth here are some excerpts from it:

Obviously I'm going to say I'm not a fan, but they work. For a smaller engine like I have it wouldn't make much sense, but with a large engine it is allowable to have some loss, I'm sure it's still better than a supercharger. I guess I have a hard time believing things couldn't be shifted around to put the turbo up front, but I can't really say. I don't see how you can say they're super efficient though, depending on what you mean by efficient. You lose a lot of turbine-driving energy through the exhaust piping to the turbo which means you have to size the hot side smaller than normal to get the same spool, which therefore results in a more restrictive hot side. On the other hand, people report such good results with them that I can't down them.

HPBooks has a book out called "Street Turbocharging" written by Mark Warner, P.E. and it talks about rear mount turbos in a positive way. It's a decent book.

^Drives an SVO

Exactly larger engines have less loss from flowing exhaust air back 8 feet to the rear of the car than say an itty bitty 1.6 liter honda engine that can barely displace enough to spool a turbo right off the header. About all Ill comment on the subject till the end of the month.

^did a 600whp rear mount on a Vetter (C5 I think)

And where does this pressure differential pre-turbine and post-turbine come from? It come from expansion of the gasses.

Turbines are modeled as isentropic expansion devices. The energy in the exhaust is contained in the form of kinetic, heat (thermal), and a little bit of pulsations from each cylinder. Almost all the energy comes from heat--the expansion of the hot exhaust gasses in a turbine.

So maybe the turbine doesn't "care" if it is hot or not, but the energy spinning it's wheel is coming from the heat in the exhaust. Read a thermodynamics book instead of google.

^He's just an asshole... well, a smart asshole, but an asshole none-the-less

Jebus are you really that dense? Are you really implying that we are saying that egts entering a rear mounted turbo are the same temp as air entering the engine???

air enters at say 100F, exits at 1400F. So it cools down to 400F at a rear mounted setup. Heat is still being used to spin the turbo (and yes the turbo takes advantage of expanding gasses as heat energy as you said). Heat in the exhaust drives the turbo, but it really just complements the pressure that is already there.

Fuck...come take a ride in my turbo. I can spin up the turbo on a cold engine (using your "windmill" or whatever-you-call-it joke). Heat does play a major role...I'm just saying don't discount big airflow from big engines to small rear mounted turbos to overcome a moderate heat loss in a rear-mounted setup.

^Response to asshole, but raises some points one would need to consider.

I'm aware of that Semantics Man. What I was referring to was the fact that there's still a lot of free hydrocarbons in the exhaust that continue to burn (hence heating and expanding the exhaust) even after they've exited the exhaust ports. Some cars position the turbo so close to the head that there are still lots of free hydrocarbons in the exhaust even after it passes through the turbine, especially at higher rpm. This is wasted energy. Ideally you want to give the exhaust gas enough time to burn off all those hydrocarbons (hence "fully" expanding the exhaust) but not enough time to start to cool off, so the ideal place for the turbine inlet would be the hottest part of the exhaust stream where it would have the most available energy, both thermal and kinetic.

I'm not arguing this point anyway, all I'm saying is that if you can reduce the amount of heat lost through the piping, you can reduce the amount of energy lost by moving the turbo farther downstream. The turbo still works, and works well, just not AS well as having it at the optimum position farther upstream, but it's a compromise, just like everything else.

^He was the OP

Depending on the application, there's enough exposed piping on the trip back up to the engine to sufficiently cool a moderately compressed (say sub 6 psi) air charge. Some applications (like TT rear mount vettes) use a front mount intercooler because they don't have enough pipe, and enough air flow around that pipe, to cool it, but a lot of the truck setups do because they're longer and the pipe is run usually right beside the frame rail.

^OP Again

I'd take the faster spool over the increased top end any day, but if you have >3.0L chances are you have sufficient power until the turbo spools to start with.

Just to comment on the heat issue, the fastest spooling header setup for a WRX/STi is STOCK because of it being cast iron and maintaining heat better than any of the aftermarket designs. It doesn't make quite as much power up top as the equal length designs, but is does have much better spool (read: over 500rpm compared to some of the headers). So what have we learned children? In real life, where you burn engineering textbooks, heat effects spool, not overall power output. Now everybody go throw out your tampons and move on to a different aspect of this setup.

^2007 SCCA Prosolo National Champion- D-Stock in a 2006 WRX