I guess I'm just trying to get out of having to build a manifold from scratch because I've got two RB headers already(one collected & one dual). The only real difference I can see is I would need a scavenge system for the turbo oiling because of it's low location relative to the oil pan. The big question is will the extra length of the header require a different turbo housing? It seems like the rest of the parts would basically be the same... injectors, ECU, fuel pump, intercooler & piping. Am I so wrong here? So is it easier to fab a whole manifold or hack up what I already have and buy a few extra pieces & go where no man has gone before?

My '88 brochure talks about the turbo as follows:

"A split chamber was invented to channel exhaust gases to the turbine in two stages; and a new "impact" turbine was developed to utilize both the initial impact and the expansion of gases to generate quicker boost, and more of it, through out the RPM range.
Hence: At low RPM, only the smaller primary chamber is open; exhaust gases are accelerated and concentrated at right angles upon specially contoured sections of the turbine blades to produce incredibly quick boost-even at a low 1500 RPM, when most other turbines are just beginning to generate boost, the RX-7 turbo already generates 22% more torque than the regular 13B rotary produces at its peak of 3500 RPM! Above 2500 RPM, the secondary chambers open to expand a broader exhaust flow over the entire turbine's blade surfaces throughout the RPM range-in fact, between 1500 and 7000 RPM, the turbo rotary's torque never falls below 145 lb.-ft."

Is this effect going to be so greatly diminished by the length of the header as to make it not worth doing?

I think that is the real question that I need answered & I don't have the knowledge or experience to know the answer. Does this make sense?

Ramses666

 

The twin scroll flapper is integrated into the exhaust manifold. There will be no easy way for you to use the system if you remote mount the turbo.

 

OK... well I guess thats what I needed to know... So now I'll need to figure out what turbo to use and the right hot side. Any suggestions?

Ramses666

 

I don't think anyone has pointed this out.

What about the AFM?
You'd have to go run 2 "coldside" pipes(one in, one out), lengthen the AFM wires from the ecu to the connector, or go standalone.

 

I was thinking about a megasquirt & then just tossing the AFM in the junk pile.

Ramses666

 

Something with a similar compressor to the stock turbo (any smaller and it's pointless) but a few points smaller on the hotside. This is uncharted so I can only guess. Somewhere in the 0.60 range?

 

Mitsubishi 14b.

Its cheap and its easy to find.

If it doesnt work you can resell it and try higher or slower. Mitsu 16g or the one under 14, I think its either 12 or 13 c

Once you decide which one you like you can go to greddy and tell them you were using a 14b, and need one slightly larger or smaller on the exhaust side, with a larger compressor side.



BC

 

Well, That sounds like an honest opinion. The STS guys said it was 2 sizes smaller... whatever that might mean...? Mitsubishi 14 B I'll see if I can find one.

Ramses666

 

Let me tell you my theory on their sizing.

The LS1 is a 5.7L engine. They use a 60-1 turbo for the LS1 rear mount. That turbo is an appropriate size for a traditional mount on a 3.8L L67 which is about 66% the size of a 5.7L engine. So the fuzzy approximate math says that a turbo designed for an engine 66% smaller is a good place to start.

Going from there I found, when looking at compressor maps to possibly do this when i was driving my GTP, is that a mitsu 14b was a decent place to start. It wont be right, but for how cheap you can get them I could experiment without breaking the bank. since the 60-1 is a decent upgrade for a 13b it stands to reason that the 14b would be a decent place to start as well. Again, its highly unlikely that it will be perfect, but it is cheap, so you can experiment.

thats why I keep pointing you to the 14b. You can get them at a junkyard for next to nothing, or on ebay for anywhere from $60-$100. Compared to many hundred for a new turbo thats not a bad price. You will probably find that it is inappropriate, but then you can get a Big 16g from an evo for a couple hundred, or go to the 2nd gen DSM stock turbo which is smaller than the 14b from the first gen.

Obviously this is all about guessing. I dont have their formula to work off of, so I just made some correlations. They arent exact, but its a place to start. This doesnt even take into account A/R ratio or anything of the sort, so again, its all guess work that may need to be fine tuned through experimenting.

BC

 

Well... I saw one on ebay for 175$ I just hope some people with real experience can help out. That's what the forum is for. I think I need some various opinions. But I thank you for yourss.

Ramses666

 

keep searching. They pop up on there all the time for less than $100.

The 16g from the evo's are probably pretty cheap as well when compared to a new turbo.

I doubt you will find real experience on this front. No one has done it to my knowledge. You would be better searching at LS2.com or LS1tech.com and talking to guys who have the STS remote mount kit. That or call a turbo manufacturer and get their input. The problem is that the rotary is so different from the piston egine as far as turbo sizing is concerned that you will likely end up having to experiment.



BC

 

Well... the price for new turbo's is pretty steep A used piece would significantly effect the budget by a factor of 10.

Ramses666

 

it would be interesting to say the least

considering the fact that we dont have a trunk, i dont know if it would work well on anything but a race-built rx-7

 

I'm thinking it could work well for any NA. If properly thought out & executed. I mean that's what I'm trying to do... come up with a way to easily turbo an NA. I mean most NA people already have a header... if we could just bolt up a turbo after the header under the car it would be very simple. AHHH very simple.... if only..... I wish... maybe someday...

Ramses666

 

why does a trunk matter?


Its hung under the car...



BC

 

Blah... Blah... Something relevant? Please? Can we stay with the subject here? what size turbo to run after the header for an NA? That is the really unknown factor at this point.

Ramses666

 

I dont know if anyone mentioned this or not because i did not read this entire thread BUT remote mount turbos are banned by the NHRA so if you plan on doing any drag racing with this set up you can forget about it if your local track uses NHRA rules and regulations.

To many people where oiling the track with long leaky oil lines for the remote mount turbos.

 

Holy smoke! I've been away for a few days and come back to find this thread on the top still! 7 pages no less!

Ramses666, it is time for action. You recieved a couple of thoughtfull suggestions for turbo's. Now do it. You will not be able to get a perfect answer for the perfect RMRT because you are a pioneer. It hasn't yet been done till now so no one really knows. Just do it!

Good Luck!

 

Well... I think I need to exploit the full benefit of experience that is available here on the forum before I take off into un-explored areas. My knowledge pales in front off the combined experience of those who have done much more than myself. I profess my ignorance to those who know better and pray for an answer to the unknown questiions that lay ahead. I bow in obeisance to those who have knowledge exceding my own & ask for a path to the salvation for the underpowered & weak NA community to try to find an answer to the question.... if I put a turbo after my header what size should it be???????

Ramses666

 

if its immediately after the header, not much smaller than stock. Gases are still hot, the header would just be like a long runner manifold. I fyou wrapped the header it would be close to the same temps. So the answer is a stock S5 turbo would probably spool a little later than in the traditional position, but not horribly later.


if its at the back of the car you are looking at a much smaller turbo.


How are you going to turn the downpipe from the turbo towards the rear of the car? Thats a question that needs answered if you are placing it there.

 

What you need to realize is that I have a 2.5 ft. header. If I wrap it & save the heat so to speak... that it is basically the same as being mounted on a normal turbo exhaust manifold?

Excepting of course the fact that I have lengthened the pipes... so do I need to calculate the length & volume of the header pipe for some kind of resonance frequency to determine the correct A/R hot side of the turbo? As we all know the rotary tends to defy the normal means of calculating the appropriate values. So...do I need something close to replacement value? Or do I need a turbo that has a smaller neck so-to-speak? I need some varied opinions here I think.

Ramses666

 

Its not going ot be the same, but it wont be as drastic of a difference as if it were at the back like I thought you were doing.

If thats where you plan on putting it then you might have a case for just TRYING the stock s4/s5 turbo and see what you get out of it.


that would be my opinion. Now Ill let others chime in.

 

OK... I've been looking at the stock turbo and the specifics of what it was designed for. Obviously the twin scroll - flapper thing has been debunked.....I need something else....the "normal" kinda thing is pretty much out the window. anyone have a recommendation? What about about a T35? Whatver that is. Just seems like some middle of the road kinda thing... I have no idea what it would be... need hot side recommendations Not sure about anything...

Ramses666

 

Two stupendously obvious points that seem to have been completely missed:

All the cars with these kits are large-capacity V8's. Obviously with all that capacity turbo lag is of little concern. Do you really think a 13B will fare so well?

All these kits also mount the turbo out the back in place of a large rear muffler. Anybody who thinks a you can replace the much smaller presilencer under the floor with a turbo needs a big dose of reality. You'll be picking your turbo up off the ground shortly into the first drive...