rotorocks

How much faster? Do you realistically know? is it going to give me an extra pound of boost? at 4K rpm? 2 extra pounds?
I look at things from a practical point of view, while you are trying to be a perfectionist. I don't care how much pressure is run, what's important for making power is how much air, is pushed into the engine. ant the high PSI is not necessarily the answer to that. And what engine are you running 30 PSI of air on? I bet if you direct that charge at your skin, it'll peel off from how hot it is. It sure isn't a Renesis you run that on, But that is not the topic of this conversation, so forget I even asked.

In a hypothetical example that you mentioned:
If you set up two manifolds with exactly the same turbines on them, and start pressurizing the the manifolds with gas at while maintaining exactly the same pressure inside the manifolds, but one manifold is pumped with 1500F gas, and the other with cool gas, the cold one will spool faster.
It will because while everything else is the same (gas pressure, manifold's physical attributes...) speed of the gas as it is pushing the turbine will be the same, the energy transfered to the turbine will be greater as the volume is higher. More mols (as Static said), doing more work. Don't believe me? try it. Just make sure that exhaust manifold pressure is maintained at the same level.

The only "laggy" side of remote turbo, as I personally discovered, is a very slight (measurable in fractions of a second) delay which occurs at the very instant you would quickly floor the gas pedal and the moment the boost begins to accumulate, which occurs due to the length of the exhaust and charge pipe. It takes maybe a half a second to pressurise the system. But believe it or not, people who drove in my car, found this actually very pleasant, and really complimenting to the rx8th smooth nature. As it really makes the car Zoom, and when driven aggressively, is delicate on the tranny. When driven aggressively, this does not even register.


P.S I just read you other post. ^
I take it back, you are not a perfectionist, you are just another stubborn and rude jerk that wonders into this forums once in a while, picks a stupid fight with one of the members and gets banned eventually. My conversation is over here. i hope you sleep well a night. Have a nice day.


...No soup for you!

evilbada

Dude, you are helpless.

If one turbo spools faster than the other, why the hell would it give you additional psi over what your waste gate is set at?

1 extra psi at 4K rpm? 2 ? What the... You clearly do not know what you're talking about.

To clarifiy your misunderstanding,,

My turbo has 61mm compressor wheel coupled with 52mm turbine wheel wrapped in .63A/R housing. It flows nicely and doesn't choke until 35+ psi.
Besides I have a very efficient 3.5" core intercooler that has 10fins/inch.
You said you want to bet the air coming out of the charge pipe will burn my skin huh? How much you want to bet? I can come up with factual data done by AMS and Buschur racing that have 8 sec Evos when they were doing Intercooler testings with ambient inlet and outlet temps.

Now onto your comparison. If two manifolds EGTs are different, how can the pressure be the same if other things are equal?

How practical is putting your turbo all the way behind the exhaust?

It maybe less than 200rpm difference in spool , but that is in fact more lag!
I dont' care how SMOOTH your car drives, and how VIOLENT it is when you floor it.

I'm just stating the fact here, and not my driving experience.
I'm pushing almost 500whp. I dont' need to tell you that.

evilbada

"If you set up two manifolds with exactly the same turbines on them, and start pressurizing the the manifolds with gas at while maintaining exactly the same pressure inside the manifolds, but one manifold is pumped with 1500F gas, and the other with cool gas, the cold one will spool faster. "


Wrong again, which manifold are you talking about here?
It sounds like you are talking about intake manifold.

Colder gas will spool faster??????

Are you talking about intake side?

You clearly confuse me by talking out of your @SS.

I've gone through 3 different turbochargers: stock turbo, GT3076r, and now PT6152r.

Of course if you step on the gas, it will start to pressurze!!

Its how much time it takes to build a certain amount of boost pressure that counts!

rotarygod

Your exhaust a/r would need to change based on your turbo location. The farther back it goes, the smaller it needs to get. This doesn't mean it is more restrictive though.

Remote mounting works just fine if done properly. Sure there are disadvantages but there are many to conventional mounting as well. Why people don't remember that I have no idea.

rotorocks

Apparently you are not following. I refer to faster spool, thus producing higher

pressure relatively to a fixed RPM and engine load.


There is a HUGE difference between running out of turbines efficiency rate and

choking the turbo by overspinning. Ever thought that maybe if you run a bigger

turbo, and a compressor, you wouldn't have to push so much boost, and still be

able to reach your HP?

And they were doing the tests with undersized turbos trying to flow enough air to produce 500+ WHP? that's laughable.
Why don't you post your charge temperature at the torque pick?

Simple, you build a test bed, and you pump the gas into them while maintaining the set pressure through a valve.

I listed about 5-6 if not more practical reasons, all of which you chose to either rudely discredit, or ignore.



Now this is totally impractical. This sort of differences may be easily offset through choosing to use a turbo with better bearings, or different oil.
You have nothing else to add and just spinning in your chair.

I couldn't even follow this blabber. Read the conditions of the test again.



yes, and in practical world, with properly sized turbo the difference is either negligible, or nonexistent.

You should read more on the topic of turbo charging.

MazdaManiac

iTrader: (3)

Boost is boost.
For any give air mass (on either side of the CHRA), there is an appropriate A/R, trim and wheel size to produce equivalent results.
The biggest problem with a remote turbo (well, the second biggest after oil scavenging), is the energy lost through radiation from the exhaust system.
And that, like any other problem has a solution or two.

rotorocks

Exactly!!!

Thank you Jeff.

staticlag

Hmm, make the exhaust diameter smaller?

ivory8

rotor rocks, are you not worried about road debris destroying your turbo since its completely exposed under the car. and what about tire smoke. lets say you do a burnout like they did in the video....i know that filter cant filter out all that tire smoke, its just a very thin sponge.....im confused as to why people's turbos aren't being ripped out from the undercarriage...

edit: sorry, im referring to the picture you posted on page one

staticlag

Your right, I'm right.

I'll admit that we need both flow and pressure

staticlag

I don't think tire smoke would hurt anything anymore than doing a burnout in a front wheel drive car.

staticlag

Roto, I like the setup, I think its a good design. I like the simple to install factor and the originality of a rear mount.

I think that if you wanted to solve any lag issues it would be no problem to slap a smaller turbo on the other side of the setup and have it setup as a twin turbo. The only real downside to a twin turbo setup is the cramped engine bay. But in the back you have tons of room to fit any combo of turbos.

Think of it, the low end torque of the greddy kit, with the top end of the mazsport kit!!!!

rotorocks

Your have as much risk damaging the turbo as damaging the muffler, or less. If you can see the muffler from the back without bending down, the turbo you can't. It hangs higher.

rotorocks

Static
there is no need for the second turbo
Well other than for the bragging rights...
there really isn't much delay or lag.
Sometimes I am in like 5th gear, and too lazy to downshift after having to slow down, so I just let her pull from like below 2K RPM. By 2K it starts making boost. Like a couple of pounds, by 3K it is at 5+ PSI and is starting to pull hard...

rotarygod

I really do think it's laughable when people argue against remote mounting when they obviously have no idea how it actually works. Especially when arguing with a person who has actually driven one! Then what's even funnier is someone who claims to have nearly 500 hp talk about lag! If this 500 hp is on a large V8 engine then lag isn't an issue. If it's on a small engine of any kind, there is definitely lag. If there is high boost there is most certainly lag. On a street car, high boost and small engine equal laggy peaky power. The funny thing is that when you talk to the people that own these cars, they deny there is any drivability issues at all. Funny how that works. Low to moderate boost on a remote mounted turbo sized for moderate power gains would probably boost very quickly by comparison. System design is everything but there is so much to think about.

The 2nd gen RX-7 turbos can't pump out more than about 275 rwhp max and are mounted right on the manifold. Lag central! That turbo is very hard to spin. You can blow through it as hard as you can and it won't turn at all. Modern large turbos will spin just from a passing breeze. These old RX-7's were fun to drive though and many RX-7 owners still love them. Then they install front mounted intercoolers with insanely long piping which increases lag. Many people admit it yet they don't hate it. Using modern turbo technology and proper sizing both on the compressor and exhaust sides, there is no reason why a remote mounted turbo can't work just fine. There are many that do have it on other cars and I don't want to hear the bs argument about how V8's can spool them up but small engines can't. That's a crap argument.

As was already pointed out, yes there are downsides to it. There are just as many downsides to conventional mounting too. There is no one right way to install a turbocharger and there is no one right place to install it. There is a right way based on where it is mounted though and that is what needs to be well thought out. I would personally have no issue whatsoever with a remote mounted turbo system. Then again I also wouldn't care if it were mounted in front of the engine or next to it. I also wouldn't mind supercharging. The key is that any of them need to be well thought out.

MazdaManiac

iTrader: (3)

Today, when I shut my motor off in the garage, I blipped the throttle like a cold-shutdown.
As the motor stopped, I could hear the turbo still spinning.
And spinning.
And spinning.
And spinning.

It continued to rotate for almost 20 seconds after the car was off. Why?
1) It is an extremely well built, well balanced, ball bearing turbo.
2) The EGTs were still high and radiation continued to turn the turbine - even in the absence of any flow at all.

Brettus

iTrader: (2)

fixed

rotarygod

Jeff heat does not spin turbos. Airflow does. I know we can get the textbooks out and say that technically there can be no airflow without a change of temperature but let's not go there. For functionality sake, it's flow. Will your turbo spin in the oven? If it doesn't, it's not heat doing the work! Yes that's a perfectly relevant test! Radiation did not spin your turbo. It was inertia.

MazdaManiac

iTrader: (3)

I understand that it is inertia.
But the presence of high heat in the manifold and cold air outside of it keeps it spinning longer than it would otherwise.

evilbada

(I'm not the one who said "Will faster spool give an extra pound of boost?" Right?)

evilbada

Its funny how some people who is as knowledgable about turbocharging as you just assume that I said my car creates no lag at all just because I talked about it.

In fact, my small 2.0L 4g63 takes forever to spin my big turbo. 24psi by 4800rpm.
One thing you don't know is my car is peaky ,but still have large area under the curve due to my supporting mods.

If you put the same 2nd gen rx7 turbo on the rear without changing anything, would you still expect the same spool rate? I didn't think so.

I understand now that remote mounting could work just as well, but if you're dealing with two SAME turbo and two different placement, the one on the manifold will spool faster. And that's the fact.

rotorocks

That is not what I sad.

What I said is this: "How much faster? Do you realistically know? Is it going to give me an extra pound of boost? at 4K rpm? 2 extra pounds?"

What is so complicated about this question?
Oh don't tell me that an extra question mark left in there by mistake threw your train of thoughts off its tracks.

Just forget it. you have issues with remote turbos? don't do them. vote fore the one mounted on the manifold. It is that simple. And quit picking fights you can't win. I am sure you are a capable modder, but this sort of thing... It makes you look bad.

staticlag

I will comment on this.

Force and Mass are two different things.

In the manifold example, of two different temps. yes it is possible, but only if you used different masses of gas. Using something like hydrogen in one and something like Xenon in the other.

Imagine this.

The lighter gas is like a BB. Lets say you wanted to close a door with this BB. In the first trial you throw the BB underhanded at the door. It 'barely' moves. This is because very little energy was imparted into the BB (low temp), now shoot the small BB at 2000fps at the door, what happens? The door moves.

Now imagine that you have a heavy gas, 'xenon'. Which is like a book. Now rest a heavy book against the door, and what happens? It will move. Throw the book at the door and we have even more energy imparted.

The point is that the same amount of force can come from something that is exponentially less massive (BB) than something else(heavy book).

Thats what happens when gasses are heated, the molecules are literally shot, one at a time, at very high speed at the turbine blades.

Another example:

1 gram of PETN http://en.wikipedia.org/wiki/PETN will probably destory more than 1 gram of crushed paper lit on fire.

Same masses, radically different amounts of foce.

rotarygod

You can't have a peaky powerband and still have a large area under the curve. You have one or the other. Apparently it's peaky. This is precisely the response that made me state that if you ask owners of these vehicles about their powerband that they'll tell you it isn't that bad. If you describe it as peaky, it apparently is that bad. You just don't realize it.

No! Duh! See detailed response below.

No actually you have no clue how it could work. There is a very good reason why the exact same turbo spools slower at the rear. There is less energy back there. As I've stated before you need to change the exhaust side of the turbo to account for this. You have lost alot of energy through the walls of the exhaust in the form of heat. It isn't the heat itself that spins the turbo though. The effect heat has on the system is that hotter air takes up more space than cooler air. There is the same amount present but since the molecules are more excited, their greater movement takes up more physical space. When you lose some of this heat, the air condenses into a smaller space. There is still the same amount of air present. It's just more compact. Since it's more compact, it takes a smaller exhaust housing to render the same spool effect. This doesn't mean that a smaller a/r is more restrictive though. It isn't because the cooler air requires less flow area.

What happens to turbo spool rate and potentially boost when a cat is removed? What happens to spool rate when a free flowing muffler is installed in place of a restrictive one? Lag goes down and boost goes up. So does power. If you remote mount a turbo with nothing behind it, there is nothing to slow it down such as a cat. If it's sized to spool up nicely you'd be shocked at how little lag there actually is.

Beind farther from the engine with cooler gasses going through it also means it isn't as hard on the oil flowing through it. That's a good thing. You are less likely to coke the oil in the turbo. If the turbo doesn't get as hot, that also means that it's less likely to hold and transfer heat to the intake side. I know people claim this doesn't really happen but it's worse than many think it is. Less heat on the intake side is more efficiency.

A big downside is oil scavenging. I agree that this is an issue. Fortunately since the turbo doesn't get as hot and is easier on the oil than a conventionally mounted turbo, there is a viable alternative. Install a small oil cooler and pump in a closed loop system that is dedicated to the turbo only. This isn't hard to do and would work quite nicely. No need to worry about taping into the stock oil system or running lines a long distance. If one can fab up a remote mount, making this setup would be simple.

I also agree that getting the intake piping back to the front would also be an issue. It takes space. As pointed out, there are downsides to remote mounting just as there is with any other system. EVERY system is a compromise.

You CAN NOT use the exact same turbo (on the exhaust side) for remote mounting as you do for conventional mounting. This is completely ignoring the system requirements. Typically you need to go down at least 2 a/r housing sizes when mounted at the rear. You will not have any greater restriction due to a difference in air density based on heat and will get benefits from the location that will nearly cancel out any lag that you'd get from remote mounting. Sure there is always a point of diminishing returns. Can't get around this. If you mounted the turbo down the street you'd definitely see lag. The back of the car just isn't as far as people make it out to be. Not at the intake and exhaust airspeeds that we are talking about. No I wouldn't use this setup at 24 psi on a race car. For a street car at low to moderate boost levels however this could easily be done with little to no discernable turbo lag. The reason why I wouldn't use it at high pressure levels on a race car isn't to say it sucks. It's just that each system has it's own strengths and weaknesses based on what is required of them. I'd never run a peaky 24 psi boosted engine on the street. EVER! That's a poor combination for the job. Then again that's just my opinion.

evilbada

Spool rate and peak boost pressure has nothing to do with each other.

You set your peak boost pressure with your boost controller.

If you boost controller is set at let's say 12psi. What the hell would faster spool give you extra pound or two pounds of boost?

That's exactly what you said.

I couldn't care less if it makes me look bad.