ribs

Since no one appeared interested in my topic I posted earlier, instead of bumping it I will just change the title and hope more people click on this one....Here is what I posted before:

Whats up guys? I'm new to this forum...where to start....

I've had 2 RX-7's before (81 GSL-SE w/ 89 n/a engine and an 88 TII), so I know a bit about these cars, but was thinking of doing a project car, and wanted to start to gather data before delving into this thing head first.

I have just gotten into doing my own wrenching recently (I couldn't afford my 86' 944 turbo otherwise), and am getting ready to sell my 90' celica all-trac to free up some funds and car storage space...but I will never get rid of the porsche...I want to be buried in it....

My idea for the project: 87-91 rx-7 turbo cab...errr...convertible (no porsche talk here ). I would want to find a convertible in fair condition with a blown motor for cheap, and then find a suitable donor engine to go into it.

Now the questions...

Is there any difference between the 2nd gen turbo motor and 3rd gen turbo motor internally (by which I mean port sizing, port positioning, materials used for the rotors and rotor housings, apex seals, compression ratio, etc...I know that the induction system is completely different (simple single turbo vs. complicated as hell sequential twin turbo) and the FD engine obviously has more fuel coming into it, but internally) and could the 2nd gen turbo motor take as much abuse as the 3rd gen (i.e. lots of boost and CFM of air) if you had the fuel to match?

Does the n/a FC motor have a higher compression ratio than the turbo II motor? How is this accomplished with a rotary engine? It looks like you would have to change the geometry of the rotor (i.e. curve on the side) to increase compression ratio, but I am still trying to learn this stuff.

If I were to do this project, I would probably want to rebuild the motor before I dropped it into the convertible body. I have been told that the rotor housings on rotary engines have some sort of polished nickel/chrome plating on them that wears off with time, leading to blow by, compression loss, accelerated apex seal wear, etc...can this plating (if it does in fact exist) be re-applied? How expensive would it be to get done?

What is involved with installing 3mm apex seals in the rotors? How much more bullet proof would this make the engine? What is the pricing for 3mm apex seals?

Why are the turbos prohibitively expensive for 2nd gen rx-7's? I was looking to replace the turbo on my old TII with something "juicier", but the cheapest aftermarket turbos I found for the car were over $2000...I can get a nice T04E hybrid turbo for my porsche for less than $1000, and add $300 for ball bearings...how hard would it be to fit a turbo like that up to the stock turbo plumbing?

What kind of air metering does the FC turbo and FD engine use? I am guessing vein/AFM for the FC and MAF for the FD...anyone know?

That is enough questions for now...my fingers are getting tired from typing...I am sure I will think of some stuff later. Thanks in advance for your replies.

Here's my car:

ribs

Oh...and here is a picture of my old turbo II that I photoshopped and made it look like it was flying through the air or something:

vaughnc

Just a though, try dual posting this in the tech forum and here.

rx7_ragtop

Good idea.

Quote:

Now the questions...

Is there any difference between the 2nd gen turbo motor and 3rd gen turbo motor internally (by which I mean port sizing, port positioning, materials used for the rotors and rotor housings, apex seals, compression ratio, etc...I know that the induction system is completely different (simple single turbo vs. complicated as hell sequential twin turbo) and the FD engine obviously has more fuel coming into it, but internally) and could the 2nd gen turbo motor take as much abuse as the 3rd gen (i.e. lots of boost and CFM of air) if you had the fuel to match?

Actually, there are 3 different motors... early 2nd gen, late 2nd gen, and 3rd gen. (assuming we are talking about US-spec turbo motors...) The earlier motor has a bit lower compression. The rotors are heavier, so the motor is balanced differently. The late 2nd gen and 3rd gen rotors are different part numbers, but are physically interchangeable. The end housings and center housings are different for each of the 3 series. The early and late rotor housings are also different in spark plug location, and hence timing. The later irons (end housings) are stronger, and will take more abuse... however, it has to be a pretty potent motor (upwards of 400 HP) before you need to worry about that. 3rd gen motors mount differently, and require significant adaptation to fit in the FC chassis. (Although Ted/K2RD make adapters/mounts for a bolt-in fit) Then you have to worry about controlling it. Manifolds (intake) don't really interchange between 2nd and 3rd gen- a bit different.

Quote:

Does the n/a FC motor have a higher compression ratio than the turbo II motor? How is this accomplished with a rotary engine? It looks like you would have to change the geometry of the rotor (i.e. curve on the side) to increase compression ratio, but I am still trying to learn this stuff.

Yes, the compression is higher. The dish in the rotor face is smaller.

Quote:

If I were to do this project, I would probably want to rebuild the motor before I dropped it into the convertible body. I have been told that the rotor housings on rotary engines have some sort of polished nickel/chrome plating on them that wears off with time, leading to blow by, compression loss, accelerated apex seal wear, etc...can this plating (if it does in fact exist) be re-applied? How expensive would it be to get done?

Yes, this is true, and no, it cannot be re-applied to my knowledge. Replace the housings.

Quote:

What is involved with installing 3mm apex seals in the rotors? How much more bullet proof would this make the engine? What is the pricing for 3mm apex seals?

Precision machining of the apex seal groove is required... but let me ask, WHY do you want to do this? Folks are making well over 500 HP on 2mm seals. The bigger seals MAY give a LITTLE more protection against blowing a badly-tuned motor that experiences detonation... but the real solution is to tune it properly. The only real reason to use larger apex seals is to "salvage" rotors in which the apex seal groove is worn beyond spec.

Quote:

Why are the turbos prohibitively expensive for 2nd gen rx-7's? I was looking to replace the turbo on my old TII with something "juicier", but the cheapest aftermarket turbos I found for the car were over $2000...I can get a nice T04E hybrid turbo for my porsche for less than $1000, and add $300 for ball bearings...how hard would it be to fit a turbo like that up to the stock turbo plumbing?

You are looking the wrong place. You can have your stock turbo "upgraded" with a bigger compressor and a clipped turbine wheel for around $700. You could put a full T04B setup on there for under $2000.

Quote:

What kind of air metering does the FC turbo and FD engine use? I am guessing vein/AFM for the FC and MAF for the FD...anyone know?

The FC uses a flapper-door type AFM on the early cars, and a slightly different but conceptually similar one on later cars. I don't know the FD, can't tell you... but the computers are not compatible.

Quote:

That is enough questions for now...my fingers are getting tired from typing...I am sure I will think of some stuff later. Thanks in advance for your replies.

hehe

Brad

ribs

Alright...I have done most of my posting in the lounge, but I am now getting to that point where I am considering getting another FC (I had an '88 turbo II for a year and a half until I let a friend drive it and he blew up the motor). I have a '90 celica all-trac that I have a buyer lined up for (the deal should be sealed within a week or two) and will have probably around $1500 or $2000 left over after I sell it, and I need to buy a second car since I don't like driving my porsche every day. I was thinking about getting an n/a this time as I am unlikely to find a turbo in decent shape for less than $2000. I am pretty familar with these cars as I have owned two rx-7's ('81 w/ an '89 n/a motor and my turbo II) and did a little work on my turbo, and since then I have more or less rebuilt my 951 from the ground up, so I am mechanically apt as well and will do my own work.

So...now with the questions...

1. When I go to look at prospective cars, I will at the very minimum be jacking the front end up looking for leaks, checking all of the suspension and brake components for wear and play, and doing a compression check on the engine. I know most of what to look for, but what should the compression #'s be? What are some other bad spots to look for on the n/a's?

2. Upgrades...I eventually plan to do a few go fast parts and some suspension and brake work. I was wondering what the turbo II's had better than the n/a's (like sway bars, brake calipers, etc.) as far as suspension and brake parts go, and how easily interchangeable these parts are.

3. Transmission...I remember that shortly after I bought my turbo II all of the syncros on the trans started to go bad (I did run it pretty hard, but not that hard)...are the n/a trannies weaker than the turbo trans (like smaller pinion, etc.) and are failed syncros a big problem? Which models/trims came with an LSD? What type of LSD was it?

4. Repairs...I wasn't too skilled of a mechanic when I owned my turbo II so the extent of my work involved changing belts, hoses, thermostats, spark plugs, etc., but never anything major. I am now comfortable changing a clutch, opening the bottom end of a piston motor up or pulling the head, replacing suspension parts, etc., so if I got an rx-7 I would do all of my own work. I was wondering if there are any big huge pain-in-the-*** jobs for these cars specific to them like the hose from hell on the MR2 or doing rod bearings, clutch work, torsion bars, etc. on my 951. Is there anything that is that bad, or is it pretty straight foward on the n/a's?

5. Motor/trans swaps for the future...I know that 146 or 160 HP isn't gong to hold my interest for too long, and eventually after I get the body (I have access to a very nice paint booth and kind of know what I am doing, so this car is going to get a paint job), suspension, and brakes up to snuff or upgraded, I plan to do transplant something turbocharged into this car. The last 3 cars I have owned were all turbocharged, so I doubt I will be going back to n/a permanently. Do the 3 rotor cosmo motors bolt into this chassis without a lot of modifications unlike the 3rd gens, or do they require shortened driveshafts/relocated steering rack/etc to make them work? Are the axles and driveshaft for the turbo II trans the same as the n/a? How much of a PITA is it to do silly swaps like a 3 rotor or j-spec turbo II mtor? Would there be a ton of wiring involved, or do the harnesses match up for the most part with additional lines like knock sensors and boost control needing to be run for turbo motors? What is the OBD situation with the 3 rotor motors?

6. Anybody know of any decent 2nd gen rx-7's (preferably '89+) in nothern virginia, maryland, southern pennsylvania or delaware for sale in my price range?

I guess thats about it for now. Sorry for writing so much...I guess I just had a lot of questions. TIA,

RETed

Compression number should be even - all 3 per rotor and front to back.&nbsp It is more important to have even "readings" versus one side high.

Leaks are common on high mileage FC's.&nbsp Keep a sharp eye on the oil cooler lines (possible sign of bursting) and oil leaking off the oil filler pedestal (drips on coolant heater hose below which will cause sudden loss of coolant!).


Depending on the model, some of the NA's have identical brakes and suspension.


NA drivetrain components are not as strong as their Turbo II counterparts, period.&nbsp This includes clutch, transmission, driveshaft, read diff, and half shafts.&nbsp '86-'88 FC's that do have LSD's are all clutch-type LSD's which wear out very quickly (30k miles is not unheard of) - assume any original LSD to be worn-out by now.&nbsp '89-'91 FC's with LSD's were all viscous LSD's which should never wear out due to their design.&nbsp Basically, all Turbo II's, GXL's, and "special models" (i.e. '88 GTU, '89-'90 GTUs) come with LSD's.

Transmissions with "grinding" problems can sometimes be minimized (or eliminated) by using a good synth transmission fluid.

Everything is pretty much straight-forward.&nbso Very high mileage cars would require an engine rebuild soon - this is not a small job by any measure and prepare to have several thousand dollars in your budget to do a proper job.&nbsp Other than that, about the only "high labor" repair you might run into is a pilot bearing failure - this basically requires the trans/engine to be separated.


Don't even bother...unless you're willing to swap out the entire drivetrain.&nbsp The typical response is - get a Turbo II first.

Sorry, but there are several web sites that specialize with car searches...
http://www.cars.com/
http://www.autotrader.com/
http://www.thepartstrader.com/
http://www.ebay.com/
Check out all the "big" web search engines to see if they got a classified section (i.e. Yahoo, Hotmail, Google, etc.)


-Ted

ribs

Thanks ted!

A couple of questions from your comments...
My old turbo II had something like 90-90-60 psi in the rear rotor and 110-105-110 in the front rotor. Obviously something was awry (chunked apex seal probably and more wear overall in the rear rotor)...I was just wondering what were normal compression #'s for an n/a motor, and how low would indicate even wear over the whole motor and time for a rebuild.

Cool stuff. Now I have to ask...do FD calipers (I think they are 4 piston calipers) bolt up, or are the bolt holes different, shims/adapters required, etc.? My guess is no (the one thing I love about my porsche is that anything off of a newer model like a 968 can be put onto an older model like mine with little or no modification)

Thats what I figured...its pretty universal amongst most turbo vs. n/a models. I always wondered why my turbo II was able to spin one wheel and have the otherone planted even though it had an LSD...The clutch type wearing out would make sense. So...I'll be shopping for an '89+ LSD trans if whatever one I end up with takes a **** on me.

Yeah...I watched a friend rebuild a 13B...it didn't look like too much fun, but definitely something I would like to do as much of myself as possible (don't you need to have apex seals pressed in or something? Its been so long since I read up on this stuff I forgot) when the day comes, not to mention I would like to do a bridgeport or something whacked like that.

Ha! You would never guess what the first thing we say to someone on the 924/944/951/968 forums whenever they ask about transplanting a 951 engine into their n/a or turboing their n/a motor...it goes like this..."SELL IT AND BUY A 951!!!". I'm still curious about how hard the 20B engine is to fit into an FC chassis...I was under the impression it was much easier than doing it in an FD.

Yeah...I know. I've been looking at cars.com and autotrader for the last couple of weeks, as well as this forums (and other forums) classified ads. The only trouble is that a lot of times there is a really great car that somebody knows about for sale locally to them even though it may be 150 miles away from me, and they could go check it out and drive it (who doesn't enjoy flogging cars that aren't yours on a test drive to give someone else an idea about the car?) for me...I've driven and looked over 3 or 4 cars for people across the country on car forums before, and usually had fun doing it.

Thanks a lot Ted!

Josepi

20B -> FC

http://fc3s-pro.com/TECH/20B/20b.html

Beat Ted to his own game

vaughnc

ribs,

It boils down to this. Buy another Turbo II (89-91) or the convertible.

The convertible does a good job with reliability, the TII (for me) is a weekend / showcar.

If you are thinking of a 20B, 13b-re, 13b-rew, or 13bt transplant, the only NA worth the $$$ to convert is the convertible.

If you want to race in SCCA, then a 1991 GTU or GTU-S is the way to go.

rogan

iTrader: (7)

Also they didn't make a GSL-SE in '81. Only in '84 and '85.

Icemark

Threads merged... please don't start additional threads on the same subject