Turbo a 1st Gen without sticking it under the hood.
 

Okay, I don't know how many do, and do not, know what I'll be talking about, but I figured I'd drop it by everyone to see what they had to say. And, I'm not trying to sell this as if I worked for them. ;)

I know a lot of people love to turbo up their rotaries but sometimes they'll just want to stick in a 2nd Gen's motor to make it simpler (I'm still not familiar with ease of turbo on a stock 1st Gen 12A or 13B but follow me on this one), but have any of you heard of STS Turbo?

I've learned about this company quite a few months ago but just now has this question come to my mind to ask everyone else. For those that have not heard of STS, they're a company that provides remote mounted turbo kits. The turbos don't go under the hood but actually under the vehicle, away from any engine bay heat source. You can check out the website for more details, but I've been through the website a few times and seen an install of a turbo kit onto a C6 Z06 'Vette on Horsepower TV. Quite frankly, really bitchin' the power that car made afterwards.

You'd have a clean(er) engine bay, and while you may be wondering just how can you still get power with pipes being routed from the rear to the engine bay, yes, you'll lose 1psi but with the turbos being away from the engine, that'll be 100 degrees cooler, which will mean more dense air and easily net you 50HP because of that, so that's a give-and-take that's worthwhile.

So, I figured, for those of you that HAVEN'T heard of STS Turbo, but would like to turbo their car, would you consider going this route? I gotta admit, while I wouldn't want to turbo my 1st Gen, this would be a neat thing to do.

for a rotary the lag would be a issue

I think that atop of the whole loss of 1 psi that it would create a really bad boost lag as well, which would be really bad as well. I don't think I would go that route of turbo if/when I turbo my FB. I think the majority of people go with the turbo being in the engine bay for a reason - it creates the best boost response time. If you want to lower the temperature of the compressed air, you can always heat wrap everything as well to cure some of that problem.

just going front mount ic on a 2nd gen you can notice a little more lag.

Actually, I should've mentioned it in my previous post, but there was no turbo lag, at least not on that 'Vette, and its wheelbase is of course much longer than the RX-7. Tho, it was a dual turbo setup, but I still don't think lag would be an issue for the rotary. I guess the only real way would be to call STS up and find out, but from what I've read, and mostly saw, it's not going to do much. But, hey, what do I know? I'm just throwing this idea out from what I saw and read. Still, when you think about it, wouldn't it be the same? Say you (don't jump on my back over this, I'm not a turbo know-it-all so my numbers may/will be off, but this is just for reference) have an engine mounted turbo producing (I don't know) 200HP at 13psi. And, from what I've heard, at 2000 RPM with..was it 8 or 10?...psi there's hardly any lag, providing you keep the revs up. Now, go with this STS stuff, you could still make the same, maybe even more, power (due to that whole give-take thing) at around the same psi and it still be the same as if it was engine mounted.

I'm not an expert, I may just have to call STS on Monday to get the full details, but I think it'll still be the same, regardless, in my opinion.

i think u should call and find out all the details

I watched the same episode this morning. Anyways I personally think its a pretty dumb setup, I can understand that there is no engine bay room. But it seems foolish to run intercooler piping all the way from the rear, need a oil pump for the turbo oil return, it just seems like the setup has too many weak links. I'm not trying to say its not possible, im just saying I don't think its a as good setup, especially when you have the room in the engine bay for the turbo.

Also I should mention that I don't still fully understand how the setup works. Turbo impellers don't work like windmills, they are positioned close to the exhaust ports so that its the fact that the gas is quickly expanding that spins the impeller...

I agree here... Also something to keep in mind is the EGT temps, so you'll have an extra hot pipe running all the way under the car, next to the fuel lines, etc... Not to mention what would happen if you happened to find yourself in a mud puddle?

I'm trying to figure out the extra hot pipe. The turbos go into the existing exhaust pipes, then you have the pipe leading from the intake, and the third pipe that's producing the boost. Does a boost pipe really get that hot from the air it'll be forcing into the engine?

Well the compressed air is quite hot before reaching the intercooler, which would be all the way at the front of the vehicle... The one advantage I do see is the ability to dissipate more heat before the intercooler finishes the job... I still wonder what would happen to a superheated turbo if it were exposed to a mud puddle... Also I must agree with a rotary the lag factor would be horrendous...

You'd have to put a heat shield, or weather shield under it in that case. I don't think it would be a good decision. I was watching television a while back where they added on one of those turbo kits to a Camaro SS and it only added like 45 horsepower or something like that at 12 psi, and claimed it to be some huge gain. I am not sure how long ago it was that I watched that, or exactly how much power it added but I just remember being very unimpressed with the numbers it produced over stock.

I think the idea would be great with a properly sized turbo (to account for the long distance) on an RX-8. Specifically since that car does not have too much room, and because it is difficult to mount a turbo to it due to the way the engine is secured.

I will stick to a normal turbo setup, it works fine. If you had room, why would you go with a less conventional, more comlicated system with more equipment needed for the same results?

If its not broke, don't fix it.

Bingo.

Ive seen these setup's on some street cars at the dragway, one transam and two vettes.

The ONLY reason this kit/style of turbo-charging is used is because of no real-estate in the engine bay (like dan has mentioned)

It *works* because, yes, its a turbocharger. But it will never, under any circumstances, funciton better (or as well as for that matter) a conventionally mounted turbo. The main reason beign that there is far too much distance for the air to travel on both the exhaust and compressor side.

It may be possible to make a rear mounted system on one car after changing various points of the setup function nearly as well as a conventional, but by that time you could have built a 550hp monster out of the money and time it would have taken.

Nothing against the the setup - it just doesn't make sense if you've got room for the turbo IN the engine bay.

They have been around for a while now,and when properly designed,the STS systems work fine.They do have their advantages,but there are also problems created by the setup,including oil plumbing/scavenging and space constraints.Seems like they are introducing more problems that would normally not be issues,by remote mounting the turbo.....just to fight heat soak and possible space constraints under the hood.

Personally,Im all for ingenuity.......,but there is little wrong with underhood mounted turbos.Everyone likes to bitch and whine about heat soak and thermal issues with turbos,but 99% of all turbocharged engines in the world are conventionally setup and they work just fine most of the time.....I know mine does.Ive never lost power due to heat,or had vacuum lines desintegrate from heat,or ran out of room for plumbing or any of that crap.

Saw the same e[isode. It is cool , especially when you have limited room in the engine compartment. For us, we have lots of room, but we do not have all the rooom and ground clearance for the extra piping. It is also very expensive, for what you would spend of this, you could get an aftermarket header and ball bearing turbo which combined would kill anything STS could sell. But for the born again kids that are 50+ with a vette and deep pockets, this is an easy sell.

Save it for your pickup truck.
 

Nobody here has mentioned that there is barely room for a stock exhaust in a 1st gen RX-7, where would you put this STS setup???? I think space constraints would make it a nightmare. Save the STS for your truck.

You can get a good, reliable, driveable 175-200 horsepower from a normally aspirated 13b, 4 or 6 port. If that is not enough, quit screwing around with this turbo fantasy and install a V8. Of course you would get a lot of flak from the clueless teenagers on this forum, but not from anyone who really knows and understands cars.

I have two FBs, one with a 150 hp ported 12a, and one with a V8. The rotary is fun around town, but on the highway, the V8 is king.

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 :D 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.
If you're going piston engined, get a decent engine. Put in a serious machine, from a serious brand. There are way better things around then an American engine designed some decades ago. Take a look ate what European cars have on offer ;)
The thing with turbo's and rotaries is that they are mae for eachother. And they will fit under the hood EASILY, so no point trying to put them elsewhere.

That's almost the dumbest thing I've read here for a long time.

You're calling others clueless when you clearly have no understanding or experience of turbocharged rotaries or turbos in general.

And then the flames begin. Just curious, if I remember my limited high school physics class, isn't pressure equal everywhere in an enclosed system? In otherwords, you have backpressure coming out of an exhaust port on an engine. It goes into the exhaust pipes. Now if there is no restrictions the exhaust gas has little pressure. I concure that traveling through a long pipe would take more time before being completely free than if it were coming out of the exhaust port into open atmospere. But a car has exhaust pipes, regardless so that doesn't matter. Now, with the engine bay mounted turbo, you have the exhaust impeller creating a restriction in the exhaust flow, and then further down the exhaust pipe, you have, cats(or not) and then finally the muffler(s) further creating exhaust restriction, before it is released to open atmoshere. In this setup, the exhaust gas is coming strait out of the engine, and therefore being very hot, heats the turbo which inturn heats the intake charge, nescesitating(sp) an intercooler to cool the intake charge.

Now on the STS design, the turbo is mounted in place of the muffler, with the air filter/intake point being up under the rear of the car, with water sheilds. The intake air is pressurised by the turbo at the rear, and is routed back up front to an intercooler(or not on some models) to the intake manifold. In this situation, the exhaust gas has a chance to cool a little as it transfers back. But the exhaust gas pressure remains the same, just takes the initial extra moment to pressurise a larger volume of gas in the pipes. But since it is cooler once reaching the turbo, and also with the turbo getting fresh air cooling from under the car, the turbo is cooler resulting in an initial cooler intake charge. Since there is now no muffler, there is 'less' overall exhaust restriction so turbo lag is much less than one would expect. The turbo acts as a muffler in this case.

So you have the exact same hot pipe (exhaust pipe) and one other pipe that runs back up to the front that is alot cooler (picks up fresh cool air from the rear, cooler turbo, etc) for the intake charge, and a braided steel oil cooler line.

THe advantage is cooler temps for the turbo from fresh air cooling the exhaust pipes, and much lower under hood temps, as well as a much cooler intake charge.

I am not looking at this from an RX7 point of veiw, but from a technical point of view.


Now, if you had a turbo mounted to a v8 in an RX7........ :D :D

Later,
Bill

Well I have to disagree. This past Saturday I went to a road course test and tune and there were 2 FD's with twin turbos, a T2 FC , my NA 13B Vert, and a ford v8 powered FC.

We all ran the same track, and that v8 rx7 was faster than everyone of the other RX7's. Now I know my NA vert is not quick, but those FD's were quick and that v8 was even quicker. The only thing that I saw out there that may have been faster was a supercharged sbf AC Cobra. I would be very surprised if it wasn't.


I'm not knocking European machinery, but the LS1 wasn't designed decades ago and is one of the best v8's on the market. THere are better engines out there, but not for the price.


But if money is no object, then hey, have at em! BMW v12 is one of my favs but I like all kinds of performance and am not biased against any of them. My NA 13B rotary engine was one of the slowest cars there (of course alot has to do with the driver ;) ) but we all had a blast. Now if they would only get that 5 mile road course built here like they are planning!!

Later,
Bill

Mounting the turbo at the back of the car is a bad idea no matter what way you look at it.

The exhaust turbine on a turbo charger is not simply driven by the flow of gas. Most of the work is done by the high pressure gas expanding and cooling after it exits the engine and moves through the turbine. By the time the exhaust gas reaches the back of the car it has already had time to expand and cool down which means it will be far less efficient at driving the turbine. Plus you have the problem of the long intake plumbing which creates lag.

Also, the reason the intake air heats up is not because it's connected to the hot turbine housing. It's due to the laws of conservation of energy. Notice in the earlier paragraph I said the exhaust gas expands and cools as it exits the engine? On the intake side it's the opposite. When the intake charge is compressed it heats up. Generally, the more boost you run the hotter the intake air gets especially when you move outside the turbochargers efficiency range. That is why you run an intercooler.

If you decide to run and STS turbo you better not run catalytic converters... Rotaries like to chew converters up and spit chunks of them out the tailpipe, imagine what those chunks will do to the turbine wheel.

I bet an STS setup on a rotary will be exteremly laggy and very peaky with the added power(if there even is any).

Threads like these pop up in the 2nd gen section often and its usually concluded that rear mounted turbos are a waste of time and money for little to no gains and too many negatives.

Pressure, yes, I believe it is equal throughout. However the larger the volume of the container the longer it takes to compress, and actually get the pressure up into a useable range. Since a long piped turbo setup will have significantly greater volume to compress, your lag is going to go up by a lot.

For the twin turbo setup in the Vette, they may have used different sized turbos (I dunno, I didn't watch it), which would give low lag and still have good high end boost.

Also remember that the 5L engines of the corvettes will push out more exhaust faster than our rotaries, which helps the lag as well.