13b4me

I believe you have put the nail in the coffin sir...

imabyter

The Turbo on my Nissan 300ZX sits at the bottom of the engine with very little shielding it from the elements. Been running 21 years that way with no apparent problems. The lag issue still bothers me, but I've heard good things about this tail mounted setup.

SSRx7

Revhed, I see where you are coming from as far as the rising temps being related to pressure build up. I believe you are correct. But as far as the exhaust side cooling, doesn't air contract when it cools? Isn't this why cooler air is more dense which is why we want cool air in the intake? I would think that when air (exhaust gases) leave the exhaust port into the pipes, the cooling action would cause it to become more dense, which would mean more volume per cubic foot/inch/ whatever.

BigJeff, I agree with you in saying that it would take more air to fill the volume of the pipe. But since you already have exhaust gases in the pipe, it would not take alot more to put the boost on so to speak.

I am not trying to prove a point, I just like discussing stuff like this so that I get other peoples perspective on things and I can learn something. Don't take it as me disagreeing with you, rather just trying to look at it from a different angle and understanding it better.

I was actually looking at these turbo setups for my truck (1500HD crew cab 6L) The STS site has lots and lots of info on the benefits, however, I like to see what the negative side of a product is before I go spend my hard earned money for it. I wish people would be honest with their product and show the negative stuff as well as the positive. I would be more inclined to buy something from someone if they were to show me the shortcomings of their product and advice on how to overcome them.

Later,
Bill

mazdaman4

hey just joining in on the convo. I have a protege along with my gs and i was going to mount a turbo right after the cat. If you run around 7 pounds of boost you dont need to intercool it due to less heat because of where it is mounted. By the way i priced it all out and you could turbo most efi vehicles for around 500 dollars. That is if you do the work yourself. All you need to do is make a couple of flanges for the turbo to exhaust /charge pipe and make an exhaust, plum oil lines, and get a fuel pressurizer.

BigJeff

Colder air is denser than hot air at a given pressure.

When you compress air, however, the act of compressing (which makes the air denser) is a very forceful process and the air gets significantly hotter. Thus the reason for the intercooler.

It works the exact opposite for the exhaust gas. As the compressed gas expands, it basically uses up a lot of the heat in its expansion, and thus cools down. That's why compressed air shoots out of the can very very cold. It's using up all the heat it can as it expands, making everything colder.

A really corny example but a fairly accurate one, would be to imagine the gas expanding or compressing as a sponge, and the energy (heat) as water.

At room temperature your sponge is sitting full of water in a tub about the same size as the sponge. When you squeeze the sponge (air) a whole lot of water (heat) shoots out into the tub, meaning there is more water (heat) surrounding the sponge as opposed to inside the sponge. This is compression heating up the air. The more you compress it the more water (heat) shoots out, and thus the air gets hotter.

When you decompress the sponge (gas), it expands and water (heat) gets soaked up, and everything gets colder.

The colder air is denser idea is like putting a towel (intercooler) or other water (heat) soaking device on top of the sponge, taking away some of the water (heat), making the sponge a little smaller (denser).

And the point of all of it is that more air = more oxygen, which means more fuel can be burned.

85 FB

I think my head just exploded trying to put that into perspective.

stilettoman

iTrader: (1)

"AROUND th highway???? In a country where you aren't allowed to drive at proper speeds on highways??? Frankly, on a highway, you need neither a V8 or a rotary. You can get along quite well with 50hp. The only reason why you would need more power is to reach top speed FASTER. Which is rather pointless on a highway.
Now of course, overhere I'm close enough to the land of no speed limits to test our cars there once in a while, and there power makes sense
Now, seriously. A V8 in a REX is just pointless. And no, I'm not a clueless teenager."

I don't know what you use your car for , but you are obviously not driving in the kind of traffic I drive in. I use mine to commute to work in nice weather, 40 miles each way, much of it on freeways. I built the V8 car specifically for that kind of driving.

A stock 1st gen RX-7 will go much faster than I have ever driven this car. It is not about top speed. I would guess my car would easily go 150 mph, but I am not stupid enough to do that on a public road (and I am too cheap to buy suitable tires for that!) My engine has about 300 hp, and yes, you can build a rotary with more peak horsepower. What I wanted was torque. Every day in traffic there are situations where I want to "make a move", press down gently on the throttle without taking my hands off the wheel and without shifting out of overdrive (4th). In less time that it takes to say "cubic inches", I go from 40 to 80 mph. Guys with V8s here on the forum will know exactly what I am saying.

Years ago here in the US, using the brakes was a good way to avoid trouble on the freeway. Now with all the idiots using cell phones, it is safer to use power to get out of trouble.

My Ford 5.0 will easily rev to 6500 with no strain, but it rarely sees over 4000, because it provides plenty of performance to outrun the Beemer in the next lane without working that hard. If he is driving an M5, he will think his car is faster than mine. Maybe it is.

Dan_s_young

iTrader: (1)

What on earth does this have to do with turboing a first gen??? You would feel right at home at torque central... No sense getting this thread closed, and causing a flame war when the inital question was a legitimate one...

anewconvert

iTrader: (1)

Porsche hasnt had any issue with turbos (hung essentially under the motor) being destroyed from contact with water.


Lag WOULDNT be horrendous. you all are operating under the assumption that when you floor it the exhaust has to be completely filled from a vacuum state. Its already under restriction, so it is already under pressure. When you open it up there would be SOME extra lag due to the need to compress the intake tract, which is under vacuum, but the exhuast will fill instantly. STS states the speed at which the exhaust tract reaches full pressurization, and I dont remember it accurately off hand, but its somewhere in the vacinity of less than a .1 seconds. Its FAST. The intact will take a moment to pressurize because you just opened up the throttle, allowing the intake to go under further vacuum.

Everyone seems to be under the impression that the systemis built with turbo that would be used in a traditional setup. It isnt. the turbo would be horribly undersized in a traditional setup, but in a rear mount the size helps keep the pressure up, and lag down. If the turbo is sized correctly then the spool lag will be no different than a stock turbo. Boost lag may be slightly incrased, but spool lag wont be changed.

I second the lack of a cat being necessary though. people have already fragged turbos from having cats break up.

BC

SSRx7

Actually this is because it is turning from a liquid state to a gas state. This is why air conditioning works so well, the freon goes from a high pressure liquid to a low pressure gas. The transformation from liquid to gas causes extreme cold temps.

I agree with you about the act of compressing air causing high temps. Any time you pressurize something heat is produced.

As far as exhaust goes, the exhaust gasses are not already compressed inside the combustion chamber as an aerosol can is. They are the byproduct of the combustion process, and it is pushed out of the chamber by the piston or rotor, depending on the engine. It is being pushed out mechanically, not self expanding as pressurized air would, just as the impellers of a turbo push air into the intake system, the exhaust stroke pushes exhaust gasses into the exhaust system. Each system has the compressor(impellor and piston/rotor), the chamber (intake system, exhaust system) and the restrictor (intake port closing and opening, muffler/turbo/cats/etc). On the intake side you are taking fresh cool air and compressing it into the intake system. On the exhaust side, you are taking hot exhaust gas and compressing it into the exhaust system......

wait a minute, where were we going with this again???? Good points to ponder.


Later,
Bill

BigJeff

The liquid in the container is made by compressing gas to the extreme of causing it to condense into a liquid. It is just significantly more compressed than in our little turbo system.

Actually, when the exhaust leaves the engine, it is still compressed. You are talking about what happens in a non-turbo engine. All of that is true, but in a turbo system what you are burning IS compressed air, and because it is compressed and so saturated with oxygen and fuel it is able to burn much more powerfully. When the gas moves to the exhaust chamber of the engine, it didn't decompress. It's now exhaust gas that is just as compressed as the intake gas. When it leaves the engine it is leaving as compressed air that is decompressing in the exhaust system, and then heading towards the turbo.

Somebody else said that they use a relatively small turbo, which would fix a lot of the lag issues, but then you're also using a smaller turbo, hehe.

So the bottom line is, if done properly it sounds like it defitely could work, but when you've got tons of room in the engine bay, why? In the end though it comes down to the same thing it always does, whatever floats your boat man!

n2318r

Compressed air in a cylinder or spray can is most definitely NOT in a liquid state.

Anyhow, there is no problem to be solved with this turbo.