I like the idea of the STS system just for the fact that if you hide the pipes right, its hard to see. I mean hell, you could say that those pipes are for some funky rotary thing, and people would be like...ooooooh, I get it now!

Anyways, I think that mounting them outside the engine bay helps with the absorbed heat off of the engine block, and helps remove a heat source/collector from under the hood. Both of those are good things, and definitely nothing to complain about. The other thing I like about this system is that if you match the compressor wheel to the exhaust flow that you have at the tail end of the car, lag would be about the same as if it were in the front. How does fluid pressurize? Thats right you chemistry wizards, all at once!

So your entire pipe is going to pressurize at the same time, albeit a little slower because of the volume that you are pressurizing. But honestly, when you really race your car, and you have it up towards 8k rpm, and you shift, does it really have lag when it drops back down to say...6ish? I think not. Saying that it creates lag isnt a valid argument, since under high rpm driving (road course, drag race) you wouldnt ever notice.

Even though this system is kinda expensive (7k for a low end kit I believe) I think that it has its place among the car community. That, and it replaces mufflers.

 

Oh I know....but really I might be that bored at my job later. So maybe.....

I was referring to intial lag from a zero boost condition to full boost, not an inbetween shifts or on/off acceleration in the upper RPM range. There you would have enough momentum on the turbine already


PS. Chemistry wizards?......

 

STS states that on their remote mount turbos they run an a/r housings about 2 sizes smaller than if the turbo was mounted conventionally. This makes perfect sense. You have lost energy in the exhaust system. Heat has been expelled out the pipes along the way. The actual volume of air is the same but it's density has changed due to a decrease in temperature. It is cooler and has slowed down by the time it gets to the rear. You use a smaller a/r housings to keep gas speed through the turbo high. This doesn't mean it's more restrictive than the larger a/r housing mounted at the engine. It's not. Remember the total energy going through each one is different.

The intake piping length need not be a concern as front mount intercoolers have some pretty damn long piping. If done properly a rear mounted turbo performs quite nicely with minimal lag compared to any other system. The nicest thing about them is that the turbos run much cooler which means they should last longer and are less likely to coke the oil.

Yes there are disadvantages to rear mounting a turbo but there are advantages and disadvantages to every setup. This can work just fine for a street car. I say go for it and report back with the results.

 

After some time & thought about this I think maybe I should try the cheaper approach of using some stock items instead of going out & buying a bunch of expensive stuff. So I'll look into picking up the required stock TII items - turbo, intercooler, injectors, ECU, extra oil cooler & lines and some gauges, fuel pump and something to control fuel pressure. Maybe I can figure out a way to make it work. My '88 NA is running good at the moment, but could use a rebuild to freshen it up. So maybe I'll try it and blow it up real good!

Anyone wanna get rid of some old parts let me know. I wonder how the turbo will work with an extra 2.5 ft of dual pipe in front of it. Maybe the extra length will offset the higher compression ratio of my NA. I guess an A/F gauge is gonna be a good idea too.

Ramses666

 

First thing you must do is dyno. This thread is worthless without a before and after dyno. If you can't find the money for this in the project, don't do it.

Man Law: There is no butt-dyno allowed for the RMRT.

 

+1, Real chassis dyno #'s before and after are absolutely necessary if you're gonna compare it to conventional setups.

BTW, you can use an electric scavenger pump to pump the oil back to the oilpan. And although I don't particularly care for them, you could use a non-watercooled turbo, to simplify the install. After, w/ the much cooler temps back there, you wouldn't really need water cooling.

 

Good Idea; just don't get your feelings hurt when someone criticizes your 'hacking'.

Bad idea, you don't have to break it.

I don't think distance or piping length is the issue. I think the key is the internal VOLUME. For example, if you look at a front mount setup, there is quite a bit of air volume in the end tanks and core. This equals volume of air that must be compressed before the system attains a certain pressure. If this is more volume than the additional piping in the RMRT, the front mount may have more lag time before the combustion chamber sees boost. Note this is not accounting for any charge temperature differences. Can you say water injection? I knew you could!

Or maybe even a wide-band?

 

Wow. You are an impressive debator. You go from one topic to another with no correlation, and then somehow attempt to insinuate a lack of knowledge.


for the record: Since I was getting rotors and pads for a foreign car on which I have never installed brakes I was being careful. My experience with brakes is limited to only GM cars. I was being certain that I didnt pay for something that I needed to get accomplished to be as safe as possible when going to Deals gap in two weeks. I couldnt afford to have the wrong parts shipped to me, just to send them back and have to wait for new rotors.


So, unless you have an argument to make concerning exhausts you need to just step back, be a man, and admit you have no idea what you are talking about. Perhaps ask a question instead of offering false information to which you dont have the correct answer. You know, like saying 'Solid rear rotors will literally look like a solid piece of metal, and the vented will look like two pieces of metal with vanes in between them correct?...' when you dont know for certain.

Admitting when you are wrong and asking for help is called being an adult instead of playing the hardass and proving to everyone that you are just an idiot.

BC

 

Since I am already picking on you:

1) The system is already partially pressurized because the engine is running. Its not like you are filling a vacuum and THEN needing to pressurize the system. there is already exhaust being backed up by the turbo.

2) Your concerns have already been addressed by people who have done this and arent theorizing. They have shown that the initial lag is only a couple hundred RPMs higher than in a conventional setup. This is simply because there is a greater amount of exhaust to pressurize. Its not like we are talking about 500rpm or greater. A couple hundred in first or second gear will be all but unnoticable compared to a standard turbo setup. In third gear or higher the rpms increase so slowly (relative to 1st or 2nd) that the lag is even further reduced if you are measuring time in rpms.


BC

 

Well, I found most of the parts in the for sale section that I would need and found some oil scavenge pumps for around $250. I'll have to save my lunch money & see what I can afford.

I was thinking about using an oil filter pedestal riser to tap an oil feed line for the turbo and the scavenge pump could maybe return to the oil filler neck. I was also thinking that I could tap the coolant line from the throttle body and run that to the turbo.

I saw a plug-n-play megasquirt with wideband unit in the 4 sale section also & figured that would help with the tuning. So I'm looking at about $1500 or so to get all the pieces I think I might need. Does that seem like a reasonable price to Turbo an NA?

The only real fabrication would be hacking up my presilencer with the turbo inlet & outlet flanges and the intake piping. Also some oil & coolant lines and some minor wiring. I found all the flanges & gaskets at Mazdatrix. I have a great relationship at an awesome fab shop (they did $20K worth of custom fab on my powerboat) so I can get pretty much anything welded or fabbed-up if I need some covers or heat shields or whatever.

I checked the STS site about their universal remote turbo kit. It was like $3000 for basically a Turbo, a scavenge pump and some hose and hose fittings and some flanges with wiring for the pump. It seemed pretty pricey to me until I looked at Mazdatrix's prices for stock parts. Holy $H!T! parts are expensive! So I guess $1500 isn't too bad a price to have a turbo conversion with a standalone ECU & a wideband. That's about it for now.

Ramses666

 

If you have problems finding out where to mount the turbo why just dont you seal of the entire back of the car (behind the rear seats), make some airintakes at the rear and put the turbo under the hatch? That would be cooool!!!! Then EVERYONE can see your turbo spinn and you dont need a airfilter (besides from the ones in the air intake).

I just got my mind rolling on the question about loong IC piping.. Has this anything to saay at all? Lets say i got 11L of intercooler and piping but how mutch doesnt a rotary use at 5000rpm? I guess its ALOOOT more than 11L..

Sindre

 

I think he is going for making this as simple as possible... not for as complicated as possible by puttin ghte turbo IN the car.


I would give STS a call and see how they have their scavenging setup. When oil comes out of a turbo it is very frothy and a mess. I would think that a small catch can under the turbo would help to settle the oil out to a liquid and make pumping it easier on the pump.


BC

 

Yeah, I thought about some sort of catch can or maybe an oil cooler after the turbo and before the scavenge pump... I saw some different check valves also.. a 1 psi check valve after the turbo so that there can't be a back-flow issue & a 25 psi check valve in front of the turbo so there isn't an oil blow-by issue with the turbo bearings. I was gonna mount the pump, cooler & check valves on a plate with a vented cover for protection with a oil pressure sensor & alarm.

Ramses666

 

You're right you got me. You are tougher on the internet than I am. Unfortunately, I wasn't using that phrase as much of a debate. Hence me saying "how do you go from this to this?" and not "you're a dummy head because you asked about brakes." It was more or less trying to work out how you post the information above to, having no idea what the difference is between a solid and vented rotor. How silly of me to have thought that some one spewing out information on turbocharging might know a thing or two more about brakes. I guess that sort of thing seems trivial to me when i'm debating something like a pressurized system.

1) I realize that, but you still have to pressurize a greater volume. Your turbo isn't spinning at 100,000 RPM All the time.

2) Ok.

 

Thats a good idea. I'm interested in seeing how that turbo is mounted as far as how it is mounted to the exhaust/intake, etc.

 

That frame notch continues to bite me in the butt. People complain about it without knowing the circumstances under which I made the decision, and I should have come up with a better solution.

If you don't want to notch the frame, there are many options:

1. Remote mount the actuator and use bicycle gear cable to connect to the wastegate. This is probably the easiest.

2. Make a new bracket to hold the actuator up higher and then cut and extend the actuator rod with a little bend in it. 2nd easiest solution.

3. Use an external wastegate between the engine and manifold on the spacer. This is relatively easy, but expensive.

Of course the best solution is to just build a custom manifold. This is easily done using the stock turbo since all you need to do is space it up and out a little. It's very small and will easily fit.

I don't understand the obsession with space. There's loads in the FC engine bay. The turbo I am mounting in there now puts the stocker to shame as far as size goes, and there are plenty of others running larger turbos.

My system had no issues with reliability.

I'm not trying to discourage you but am trying to point out the potential problems. If you make a manifold (which is going to be the equivalent work as far as fab goes) then you don't have issues with where the turbo fits. I did the spacer because it was quick and dirty.

Also, have you looked at this?

http://www.aaroncake.net/rx-7/naturbo.htm

It's a proper writeup that covers things with a lot more depth then the original thread.

And there's also these, which are my current setup:

Stripping and pulling the engine, engine disassembly
My Winter Project
Painting the engine bay, cleaning and prepping the engine, porting the irons/housings, painting the engine and starting to shave the lower intake of all emissions stuff.
Finally! Pictures and Status Of My Turbo-NA-Bridgeport
Assembly of the 6 port high compression bridgeport engine. Also lower intake emissions removal and shaving.
Pics and Status Of My Turbo-NA-Bridgeport Engine Build
Porting the intake manifold and turbo wastegate, wiring the battery relocation, some minor rust repair, engine mockup and oil pan modifications for turbo oil drain.
Progress Of My Turbo/NA/Bridgeport Project (Project Tina)
Engine and transmission installation, undercoating with POR-15, creating the new wiring harness, building a battery box.
Pics and Status Of My Turbo-NA-Bridgeport Project (Project Tina)
Building an upper intake manifold from scratch and fabricating coolant pipes.
Latest Pics and Status Of My Turbo-NA-Bridgeport Project (Project Tina)
Building the fuel system, oil cooler lines, coolant pipes, and exhaust system. Also installing the upper intake, making the metering oil lines and installing the driveshaft.
Midsummer Update On My Turbo NA Bridgeport Project
Fabrication of the intercooler, intercooler piping, gauge installation, some wiring and the first startup on the new setup (video included)
It Runs! Pics and Vids Of My Turbo-NA-Bridgeport Project

People are indeed constantly worried about heat, but I think that's primarily because people don't apply proper heat shielding. Look at Mazda's OEM setup: EVERY part of the exhaust is shielded, especially the turbo and manifold. Put similar shields on underhood turbo stuff and the heat reduction is dramatic. Just by wrapping my turbo and downpipe, my underhood temps fell to less then they were when the car was NA (as judged by my hand). In fact after getting off the highway I could lay my hand on the turbine housing (wrapped of course) for approximately 10 seconds before feeling any discomfort. And if I do say so myself, I did a pretty crappy wrapping job.


Keep in mind that many of these systems are designed for big V8s, which have ample low end torque. I've also seen videos both on and off TV (Horsepower TV did an install a few months ago) and the car makes virtually no boost in 1st gear. They had to power brake on the dyno in high gear to keep the boost up. This is a far cry from a turbo NA rotary setup which will do 5-8 PSI revving in neutral.

I think this is inviting disaster. You need to size the turbo smaller if you aren't mounting it at the engine, as mentioned earlier in the thread. The stock TII turbo is an old an inefficient unit, and it has a large hot side compared to what you would find on most production cars. Those things combined will probably make this setup lag city.

What doe this mean?

As in a wideband. And if you are going to remote mount, then EGT readings would be very interesting as well, both at the manifold and at the turbo.

It seems to me that you keep adding parts and points of failure on top of what you would need in a "regular" turbo setup.

 

there is a difference between 'knowing a thing or tow about brakes' and clarifying to save me a headache when i cant afford the headache.

You have yet to provide any information to support your statements regarding backpressure. Is this because you have accepted that you are wrong and are attempting to hide that by hanging on the fact that i asked a question about brakes, or is it because you are so tied up pointing out that I asked a question that you forgot to defend your argument?

The fact of the matter is that a turbo is in no way or shape helped by having any back pressure in the exhaust system. The turbine is spun because of the pressure differential between the engine side of the turbine and the exhaust side of the turbine. The greater that differential in pressure the faster the turbine will spool up. Under no circumstances will a turbo spool up faster, or will an engine produce more hp, if there is more backpressure in the exhaust system. Its that simple.

And those who have already done this have shown that the difference in spool time is so minimal as to be nearly undetectable.


BC

 

What?! Turbos DO need heat to spool up. If an engine did not produce exhaust heat, that is, the air temperature in was the same as air temperature out, the gas volume going through the compressor would equal to the gas volume going through the turbine. The turbo basically relies on gas being forced through the turbine to spin the compressor, and a difference in volume through the turbine versus the volume through the compressor makes driving the turbine wheel fast enough to create boost pressure.

The turbocharger works off the principle of thermal expansion. Air and fuel is burned in the engine and thus super heated. Conservation of mass states that the mass of gases going in is equal to the mass coming out. However, the volume is very much different due to the heat gained in the combustion process.

No kidding. A turbine doesn't work when there isn't gas flow through it.


That's correct. However, you'll find that the volume of air being moved by the compressor is, at the very best (100% efficiency) equal to the amount of air being forced through the turbine. Given that you have an air line capable of blowing a set CFM of air through the turbine, how would you get that compressor to be able to be able to move more CFM then you are blowing in? You need more volume forced through the turbine. But how do you get more gas volume out when you have only a set volume in? There must be some sort of way to expand your set volume of gases. That's right... HEAT! It has NOTHING to do with A/R.

 

Wow! I guess I must have struck a nerve with Mr. Cake. That was an extensive response from him. Which is what I was wanting after all. that's the reason for the forum - exchanging ideas, information & opinion.

With all that said... I'm not sure why, but I'm thinking about trying this just to try. Maybe I'm bored & should just get a life or something. You know.. it would be nice if there was a SIMPLE way to turbo an NA, but life isn't simple or fair. I'm trying to make lemons into lemonade.

I can hear it now... Just sell the damn thing & buy a turbo car... & that seems to be the most reasonable thing to do sometimes. I'd rather have a 20B, but I'm not that wealthy.

I've got what I've got... an NA & it just sux 'cause it should go faster & be more than it is. I'm just frustrated about the whole damn thing & want to make it better than it is. It's not trying to prove anyone wrong or that I'm a smart person or one way is better than another. I want my car to be better than it is & I'm trying to figure out how I can do it.

Ramses666

 

I am ALL for you trying this.

that being said: What are your goals and what are your capabilities. If you can fabricate and can afford to be buying a swapping turbine housings to find the right one then this may be your ball of wax.

Your goals also need to be taken into account. What do you want to accomplish? Looking for a straightline car? Looking for an AutoX car? just want somehting different?


BC

 

My goals are having a RX-7 that lives up to my expectations of speed & power from a true sports car with a real racing heritage. I don't race. I guess my expectations are a result of riding in a couple of rx-3's with rx-7 racing engines in them back in 1980. A couple of friends had them and it was absolutlely screaming fast. So 20 years later my Father gave me his "baby" when he got cancer and it was lame & disappointing. I love the way the car drives & handles but the acceleration sucks. My Mom's Honda Accord is Faster. Her old Park Avenue Ultra killed it.

I did a piston engine rebuild in 1984 when I was 16 and have and worked a little bit here and there since then. I have a good natural mechanical ability. I was taking things apart & putting them back together from a very young age. I made my own toys as a kid and my own guns & bombs as a teenager. I've been building my own compters since the early 90's. I've worked as an audio & lighting engineer designing, building & setup & operation of concert systems since 1985. I've restored 2 historical homes.

Been to Tech school twice. Once for industrial electronics & once for CAD/CAM. I refitted my 1971 20 ft. aluminum work boat from just an empty hull. I have an decent small set of mechanics tools. I have a nice garage to work in. I don't have any metal working tools (welders & such). I work part time now doing custom electrical & home improvement. So I think I have some decent abilities.

I've always been pretty stubborn & tried to do things people told me couldn't be done. I've succeeded mostly with good results, sometimes not so great. I've always tried to think things through as much as possible before committing to a project and to get as much info as I could.

Ramses666

 

go for it. You arent a 16 yr old talking about dreams he has for a F&F car that he can do mad crzy burnouts in, so I'd say you are ahead of the game.

I do agree with arron that the stock turbo is going ot be pointless. I would say a mitsubishi 14b from a 1st gen DSM would be a great starting point. You can get them for a snot filled tissue paper on ebay and if it doesnt work you have a nice paper weight.

the $3k 'univeral' system from STS is ridiculous but I wouldnt hesitate to call them and ask how they came to their turbo choice. Maybe talk to someone at a turbo manufacturing company. Might get some good thoughts there too.


BC

 

I can tell you are trying to use your chemistry class knowledge to impress this upon me as you are trying to get down to the molecular level with your response as to the scientific reasoning as to how engines work. I could quite frankly care less about getting into a thermodynamics argument on how an engine works and why but I can if you want to go there. From a functionality standpoint it's flow and not heat that do any work. If you don't keep things insanely simple and unscientific here, no one will understand you. If you really wanted to get technical you'd say that unless air is at 0* Kelvin, it is doing work as it's molecules are moving at any temperature above this and more heat is more molecular movement and hence energy to impart on a turbo.

That's all fine and dandy but it's not heat that directly affects a turbo spooling. It's flow through it. Heat just has an effect on the density of the air flowing through it. A hotter exhaust gas needs a larger exhaust wheel than a colder exhaust gas does to maintain the same spool characteristics. This isn't directly due to temperature though. By your own admission if there is no flow it won't spin. That means that temperature is not a contending factor on making the turbo spool. It is an indirect factor as it changes the characteristics of the air flowing through it and you need to compensate for it. It is not heat that spools a turbo. It is flow. Yes technically if you had absolutely no heat and were at absolute 0*K, you could have no flow. We aren't arguing that though so don't go there.

 

Yeah thats what I said, but you don't listen. Let me re iterate.


YOU ARE RIGHT

My previous response was limited due to things such as work, I get to type in machine code all day.

 

I'm not really trying to discourage you, but am trying to point out that taking a remote mount approach might not be as simple as you thought.

There is....Build a manifold (or pay someone to build it), bolt on the turbo, install larger injectors and an upgraded pump, set up the intercooler and then go have fun...It's fundamentally not more complicated then turbocharging any other car or doing a turbo upgrade to a TII. But because there are no kits, the fab work falls into your hands.