outcastcat

Hopefully this post works this time.

I came across a system known as remote mount turbo. Its where the turbo is mounted in the rear of the car, and the intake piping goes back up the length of the car to the engine in the front. As I brainstormed i thought that this might be a good system to mesh into a custom RX-7 N/A turbo kit or a replacement turbo system for turbo RX-7s.

The major advantage too the system is cooling. Since the system draws from underneath the car far from the engine it picks up nice cold air, and since the intake piping runs along the bottom with this nice cold air you end up with a natural intercooler. Thus the system is able to offer intercooler or better intake temperatures, even without the intercooler. It also does not fight the radiator for cold air up front.

Since the RX-7 is notoriously hot and heat is the enemy of performance I thought this system could mesh well. The reduction in temperature would allow more fuel/air and would cool the engine naturally, perhaps allowing you to lean out the rich fuel/air mixture without risking deadly detonation. If not it would still provide a lower risk boosting option for N/As and a performance gain (even at same Psi) for already turboed systems. With the addition of a real intercooler, intake temps for boosted air could fall below 100 degrees F in somewhat cool weather (below 70 ambient).

Because It doesnt remove any stock emissions stuff it is also helpful to those of us undergoing mandatory emissions tests.

So what do you guys think on this techno post. Its an interesting performance idea so post your (intelligent) comments.


I learned of remote mount turbo in a review of the STS system for Type R integras by Hot Compact and Import, they had little to no lag problems or throttle response problems. It also won the 2004 Best New High Performance Product award at SEMA. So its not as bad as the idea might suggest in terms of doability and turbo lag. So please limit discussion to what the advantage might be for RX-7s over a normal turbo.

Houstonderk

iTrader: (3)

I saw that peice on ebay. Don't get rear ended.

SonicRaT

iTrader: (6)

To begin with, there's little to no room to mount the thing anywhere, also, running oil and coolant lines that far back would get a bit on the expensive side (not to most oil drains are gravity fed, how the hell do they get that oil back?). Next comes the immense piping, which doesn't do much good for cooling since there's so little surface area contact between the air and the piping that it doesn't cool it like most people like to think (if it were the case, there wouldn't be intercoolers, just pipes running accross the front of the car). The idea is to make a lot of surface area to dissipate the heat, and spread the air out through that area to dissipate it further. Also, for a turbo, you WANT the heat and the strong pulses of the rotors to help spool. This has come up many times before.

geek

without causing an arguement, I would like to point out that these systems work very well on other vehicles. I'm not pro or con on this but I do think its quite interesting. http://www.ststurbo.com/home

J-Rat

iTrader: (2)

Can you actually have a REPOST in the 2nd gen section?

uRizen

iTrader: (2)

I think the worse problem would be finding room to run all the piping. Our center tunnel is pretty packed as it is, and I don't think you'd want your charge pipe running along the exhaust.

SonicRaT

iTrader: (6)

Of course it works well on cars without a turbo and they can show off lots of good numbers. But does it work better than the same car with a standard mounted turbo? The answer is almost always no.

fc3stom

Worst thread of the day...

outcastcat

It might work better than a standard turbo on the RX-7 because of heat. The intake piping increases in length enough from the back so that yess u can cool close to a intercoolers amount. And you can coat the exhaust to maintaing heat. Plus since you dont have all that exhaust piping and muffler behind you, the pressure drop is equal. Its not pressure in front of the turbo that causes it to spin, but the pressure difference between the two sides.

However the idea wasn't for a stock turbo RX, but the N/A version. It is expensive, but its simpler than the engine swap. The kits run 4000$, but i assume it could be built MUCH cheaper. Find as good of a turbo as you can, and you can do the intake piping yourself. If your woried about still being to hot, u can fin the piping, and you dont get the pressure loss associated with the bends and holes of the intercooler (much like running straight back exhaust, it decreases pressure lost). If you used a used turbo, it and the intake piping as custom exhaust not be too expensive.

Im wondering of the reliability of the system. Obviously serious tuning would haveta be done, but for me I knw a place that works with rotories exlusively. However the detonation usually associated with increasing the amount of air would be instantly deadly, so thats the real advantage of this system. Not so much power, but heat. And with the less heat, you can run more boost. It picks up colder air, the turbo is cooled more, and u get at least as much intake cooling.

If you haveta change rotors or even ma ybe apex seals to 3MM, its probably not worth it. Its still probably 1000-2000$, and some custom work , plus extensive tuning (not to mention u need engine manigement and a new electronic knock sensor).

staticguitar313

iTrader: (2)

gay

rotarygod

iTrader: (1)

There's nothing wrong with this type of system. It's just different from normal and is criticized because of it. You also need to size the turbo differently for rear vs front mounting which is another reason why many say it can't work good. That being said, the 2nd gen isn't the best car to do it on. There isn't alot of room to put it unless you place it where one muffler would be. The only place you would really have room to run the piping back to the engine would be right next to the insanely hot exhaust pipe. This would be counterproductive to power. Yes you would need long oil lines and a return pump but even a Porsche 911 turbo uses a return pump since it's turbos are mounted so low to the ground. Water is not needed if you don't use a water cooled turbo. No surprise there. The idea is just fine. It just may pose some piping issues in an RX-7. Then of course you'll still need some form of fuel management. You will always have the people that will tell you to just swap in a T-II engine or buy a T-II instead since it would be easier. Forget the fact that good ones aren't easy to come by anymore.

FWIW: Turbos do NOT need heat to spool up. Not at all. Not even close They only need airflow. Hotter air takes up more space than cooler air though and this is why you need a larger a/r when the turbo is at the engine vs the rear of the car. This is what confuses people. A properly sized turbo by the engine and a properly sized turbo at the rear will have the exact same amount of backpressure and spool rates as each other even though the a/r ratios are different due soley to the amount of space the exhaust gasses take up at different temperatures. Cooler air takes up less space and needs a smaller a/r and vice versa. If a turbo ran off of heat at all, you could stick it in the oven and get it to spin. You can't. You can get it to spin off of an air compressor with cold air though.

R-apid-X-haust-7

i would not do it on my rx7, cause doing the n/a conversion right now is pretty easy, but i do think that the kit for my 05 quadcab HEMI would show my truck some ditches , being its already a speed deamon. but i would never pay 5Gs for a kit like that when it could be peiced together way cheaper and i could just throw it up front or put a SC on it.

uRizen

iTrader: (2)

I just thought of another advantage to this kit. If you pulled it off right, you could have a bitchin' sleeper.

Even better, how well would it fit on a FB?

SonicRaT

iTrader: (6)

Unless you cut a hole in the floor, there's almost nowhere else to stick it.

Boost Lee

iTrader: (3)

Ok, lets say you do put a turbo in the rear of the car... what does that do for lag? Don't you end up having to pressurize a chamber the length of your car? Intercooling is gonna be a bitch to say the least, and that's just adding more volume to pressurize before in addition to the intake manifold. Pressurizing takes time.... which means lag but if you've got 3 T25's on there, you can make good boost and have it spool pretty reasonably.

CompuBob

i would never do it, but i did think up a solution for the whole no room thing.. in the rear bin, behind the pasenger seat, weld in a thick steel box, cut some holes for the piping and put the turbo in there, it would be closer to the engine and no one will notice it

SonicRaT

iTrader: (6)

Haha... you'd definatly be able to tell when it spools! (And hope to god there's never an exhaust leak!)

uRizen

iTrader: (2)

Holy crap, quick, someone try this. I want to see some in-car videos. Hehe, you'd have a pretty warm cabni for those chilly winters as well.

rotarygod

iTrader: (1)

Take a look at the Greddy front mount intercooler piping length and try to tell me it is any shorter than a pipe running from the back of the car. That kit has some very long pipes to it in addition to the intercooler.

Also remember how much faster a turbo will spool up with a free flowing exhaust. Get rid of the cat or muffler after a turbo and it spools up a whole lot faster than stock. The rear mounted turbo is sized to take advantage of the strength of the pulses that reach it. There is no exhaust restriction after it. You always size a turbo based on the flow before it. Some people use a certain turbo for a while and then only change exhaust manifolds and find they have to do some slight a/r change on the turbo. This is still independent of any restriction after the turbo. The rear mount is no different in this regards. If you still use a cat, it is sized based on the strength of flow after the cat but still has no muffler behind it. It should spool up very fast. Definitely fast enough to make up for the several feet of exhaust pipe gain before it.

Check out the LS1 forums sometime. LS1.com and LS1tech.com Go look at the owners reviews of their systems. They are very popular. The argument that they have V-8's is irrelevant. We have stronger exhaust pulses than they do and the turbos are sized for each application anyways.

SonicRaT

iTrader: (6)

The greddy unit has about 7-8' of piping. From the rear muffler area (the only place it would fit), to the front of the car (if you had a front mount) would be around 10 feet or more (depending on the bends), then another 4 or so to get back. That's almost twice the piping length if you were to use a FMIC. Unless you're planning on just using the pipes to cool the air (since most of the heat is from compression, and not directly sucked off the heat of the turbo), I don't see how you can argue the pipe length, (and yes, people do notice the difference of the top mount to the greddy intercooler.)

outcastcat

Pressure in exhaust systems doesnt have that much to do with the Size of the exhaust so much as how straight and how hot it is. But remember since you have less space behind you the pressure behind you is less. So in a sense, yes the pressure in front of the system is less, but so is it behind the system, so the effect is the same.

The system I'm imagining is a bit of a sleeper, which is aided by the fact that the turbo acts as its own muffler. So as a matter of fact you can put it in place of the muffler, which would also be the easiest way to do that (you could even get a high flow cat back exhaust without the muffler, so you dont haveta custom fab it, then just get it treated to reduce heat lost).

The pipes themselves do act as the intercooler. Since they are exposed to outside air rather than engine air for most of that length, they should cool the air itself. This is the way the STS system is designed to work, however I doubt they will ever make an RX-7 kit, and at 4 grand it would be cheaper to build it yourself.

SonicRaT

iTrader: (6)

Pipes by themselves still don't cool as well as an intercooler.

outcastcat

Of course, but their extra length gets them close enough. Combined with cooler intake air and a cooler turbo, it should be about equal. Fin the pipes and you wont lose pressure only temperature.

Any difference in temperature could be made up for by the increase in PSI because of the lack of bends and intercooler piping, but heat is the biggest object here because of detonation.

RotaryEvolution

iTrader: (30)

leave the turbo where it is and move the engine to the back!

SonicRaT

iTrader: (6)

Most of this heat is generated simply by compressing the air (which no matter where it's located does it pretty much equally).