So, my engine is on her last legs. I dunno whether I want to do a Tii swap, or just have someone rebuild + port her out. So, what are the pros + cons of each. Also, what would I be looking for cost wise into a Tii swap? I found an engine + tranny for 1100 shipped, but what else should I look for besides either a driveshaft or a Tii rear end? Also oppinions are welcome.

 

I'd go NA for reliability and fun factor. Go Turbo for competition and performance, just my .02

 

What are your goals?

If it's all out HP, then you will have a hard time making 200HP with an NA without making compromises.

 

I agree with Aaron. You have to make a lot more compromises to get an NA to make the same power as a very mild turbo motor.

 

I put down 172rwhp with almost every normal n/a mod... that's what a stock T2 dynos. That's street port, exhaust, tuning, etc.

T2 swap with open exhaust and proper fuel setup should do over 200whp. just go for that if you really want power and torque.

 

Hmm... Good point.


I don't really wanna have HUGE Hp number's. To me that's just a pissing contest. That's also why I got a motocycle. Power/weight is MUCH better with those so I know I probably won't get close to that on the 7 without major mods.



Here's the thing. I know I'm going to have to rebuild sometime in the near future. I was looking at prices + it seems like the turbo swap would be cheaper. 1100 for engine + tranny, then I think the drive shaft that would hook up to the NA rear end is 500? I know I'll probably need an ecu, then a boost gauge too. So I'll say 3k all together (let me know if I forgot something)

For an NA rebuild, if I do it myself it will be anything from 1-2k depending on what I need. I'll probably need alot too, my compression is pretty low. Then there's porting. I got quoted 5k from two different people to take out my engine, rebuild it + port it.

Eventually one day I would LOVE to have a turbo car. I just mainly want some more pep in my FC though. Reliability isn't as big a factor as it used to be. Like I said I have my motorcycle + that's more reliable than anything (unless I mess it up hahah.) So If I can have something that I know I can fix then I don't mind if something goes wrong sometimes.

 

Take it for what its worth, because I'm a n00b...

But, I'm methodically working on an NA build up... Exhaust is done, emissions gone, Full Suspension Redo, & a GTU-s Diff. A Mariah Cold Air Box is next. After that, maybe an S-AFC.... trying to get whats available from this NA. If I'm not happy with that, I'm going to put in the rest of the Turbo chassis pieces.

Why?

So, when this motor finally lets go, I'll have a platform that's ready for a turbo'd 13b.

 

If you are going to Change the Power Plant,you may as well change the Drive line too.For What it is Worth you can find a TII Differential and the Driveshaft and the Axles ,(Used parts), for Pretty well what Mazdatrix Wants for Just a driveshaft to hook up the TII Transmission to the N/A differential..Also,the Sake of knowing that your *** end won't give out on you if you decide to drive the car agressively..Priceless!

 

Why a GTUs diff? You realize that a Miata T1 or T2 Torsen or the S4 clutch-type is better suited for track/race/performance?

 

Well this is kinda confusing b/c you said you don't need huge HP and you don't need huge reliability. So what do you want? Low price / effort? I dunno how hard it is to port your engine yourself, how much it would cost to pay someone to drop in the TII, or how much you'd pay someone to rebuild the N/A if you pulled it out yourself. Those could be factors. I mean you're looking at paying someone to do everything to your N/A vs. getting a TII and doing everything yourself. That's not the best comparison. I mean, if it's really that much cheaper then all the N/A people should skip the rebuilds and drop in a new engine. Heck you could even drop in the TII engine and get rid of the turbos, if it's that much cheaper.

I'd compare long term costs and benefits. First find out exactly how much you'd do yourself in each case (in hours) and how much it costs. Then guestimate how much extra maintenance and gasoline the TII will cost you (in hours and dollars). Then figure out how much power you'd want with the N/A (after upgrades) and how much you'd want with the TII (after upgrades). Count the costs of upgrades too. Derate future expenses by ~6% per year. $100 2 years from now is ony worth as much as $89 now, b/c you could invest that $89 and get $100 later. In the end you'll have 3 numbers for the TII: extra hours, extra dollars (perhaps a negative number), and extra horsepower. Figure out how much those hours are worth to you. Figure out how much that horsepower is worth to you. Add everything up. Is it positive or negative? Bamn! You have an answer.

I'm curious about the costs and time commitments myself since I don't know whether I'd rebuild my N/A or get a TII engine when that sad day finally comes.

EDIT: You're looking at about 175wHP on that N/A after basic upgrades or 200wHP on the TII after the same. Plus the TII has a lot more potential for future upgrades.

 

I went with the 13BT swap... I have spent WAY more money than I had planned, but I would do it over and over again. I am looking to make 300RWHP or maybe a bit more. I think a strong, reliable, decent HP N/A would be a good choice. I think the N/A rebuild and street port would be cheaper than a 13BT swap, but not as much power... obviously.

BTW... I bought my JDM 13BT from a place in Canada that imports Japanese engines. The engine was no good and I had to have it rebuilt. So, don't think you're going to buy a JDM 13BT and everything be perfect. Also, i you're going to get your N/A rebuilt and street ported you may want to go with Atkins... I noticed you're from Washington and they are from Puyallup, WA. I have bought parts from them and they are very understanding and great to deal with. I just want to say though, I had my engine built by Kevin Landers at Rotary Resurrection in Tennessee... I couldn't be more pleased with the great job that he did.

Here is Atkin's website: Atkins Rotary

Here is Rotary Resurrection's site also: Rotary Resurrection

 

GTU-s' Diffs come w/ a 4.30 ring & pinion... That, and clutches wear out.

 

the driveshaft that you're looking for is only 288 at mazdatrix. thats what i did, and it works just fine. if you buy a TII "package", the only two things you'll need will be an AFM and Boost Sensor. many of the "packages" are starting to include these items.

go with the TII swap, you wont regret it. its too easy to do and not that expensive.

 

You want a reliable rx-7 with some power? Do the full TII SWAP and leave it bone stock, or at most intake and catback. You should be fine like that. My S4 TII with 155k that has been bone stock its whole life, has the same compression readings as my low mileage 60k s5 engine. So if you take very good care of it, the motor should not fail on you for a long time.

 

Some of these people should be ignored. A TII (13BT) swap is not easy nor cheap if you do not know what you're doing, don't have the tools, and if you keep getting some false information. I have heard of many people receiving a crappy JDM 13BT, including me. I would order a 13BT from either a reliable source or from someone on this forum. Always ask for a compression test also. It WILL cost you more to do the 13BT swap, depending on what you plan on doing to the N/A engine.

 

My experience:

I bought an unbelievably clean 91 coupe from a lady my wife works with. She bought it new in '90, and the car was/still is factroy clean, except the coolant seals were toast.
I wanted to do a TII swap the right way: TII all the way back. Engine, tranny, rear end, ect.

Once all the costs were factored in, I was looking at spending close to 5000 bucks on my FC.
I found an FD for 6 g's, and although it's nowhere near as clean as the FC was, I'm stoked on the new car. It's got stuff in it that no FC will ever have. The BOSE system sounds great, the twin turbos are pure fun, the suspension is much more track-friendly and IMO, an FD is just plain better looking than an FC.

Don't get me wrong...I LOVED my FC, and if the TII swap would have costed less, I probably never would have bought an FD. As it is, I keep looking out at my driveway...still drooling over my new car, even after almost a year.

 

I forgot to add... you CAN use the N/A harness on the TII engine and do what Natey wanted to do. Do the swap the "right" way. Meaning not only get the TII engine and tranny, but the whole drivetain also.

 

imho, i'd say you stick with the n/a. like you said, if you want power hop on your bike haha, but the tII are great motors, if properly taken care of it'll last a long time

 

You will never get the hp/$ of a turbo car in an NA. just wont happen. But what you can get, for a price, is throttle response better than any turbo engine can claim, with fun power. ITBs. thats the route im headed. 6pt Aux Bridge, full exhaust, standalone, and ITBs.

www.fuji-racing.com is the route I plan on going. Worth looking at if you have the desire to go over 200whp, but its not going to be cheap. Only reason I can afford it is because I bought my car with a fresh port from kevin landers. a port plus $1500 ITBs + $1000 standalone, PLUS $600-$1000 full exhaust is much more expensive than a solid TII swap.


BC

 

Oh, you're talking about the entire rear end......just the diff unit itself has no bearing on the ring and pinion.

Clutches wear out sure, but so does the viscous fluid. The anti-shearing characteristics of the fluid wears out over use and time. Plus the fluid isn't rebuildable. Clutch-type will last you a good 70k miles, if you don't clutch dump every launch. Viscous will go maybe 100k, 125k. I should know, I have a 140K GTUs. At least with the clutch-type, you can rebuild the diff to the lockup spec that you want by changing the plates.

I'm planning on going with a 5.12 Ring and Pinion with a Miata T2 Torsen diff, if I can find it (and afford it)

 

Right, & I agree w/ what you're saying. I still have the option of replacing the LSD to a clutch type later, if/when I deem it necessary.

I cant dump the clutch, because at this point, cuz I dont have one, It has an automatic tranny, which come w/ a 3.909 R&P. Really, I just wanted the gear, & was really more joking about the clutches wearing out. For the time being, the car is spozed to be a fun daily driver, so I was ok w/ a VLSD.

If I get to the end of this NA build up, & find I'm still hungry for more powah, this diff's going to get replaced anyway. I can say, jumping from 3.9 to 4.3 gear makes a noticable difference in highway driving, even w/ an auto tranny. Yes, a manual swap is one of the items that will be part of this build up.

 

Lots of different oppinions here, but thanks for them all.


I'm not sure about atkins. Someone told me that they were taken to court by several people because they didn't respect their own warrenties.


I got quoted by two different people 5k for removal, rebuild, street port + re-install.

I would really love to do the rebuild myself, but I don't have as many tools as I would like. I need some of those calipers + whatnot to measure warpage.


I could probably do the Tii swap. I would just need to rent an engine hoiset to pull everything out + put it back in. I'm not looking to get mod crazy. Maybe just an FMIC, BOV, exhaust. Nothing internal, no bigger turbo.


I already have some JIC coilovers, SAFCII, intake + a shitty header.



I KNOW for a fact that if I rebuild it, I'll need irons. I have a few stuck bolts that broke off in there. Also I have some leaks that are held by JB weld. Its ghetto, but I was in a pinch at the time.

 

what are the stock numbers for the s4 n/a they cant be as low as you guys make them sound i know there around 146 new and really you can get alot with just the port itself..i stick to the 1st gens and i bought a 2nd gen with a blown motor to try and fix...the old 13b i had could lay down over 200rwhp and that had a aggresive streetport steright pipe and the throttle body mod from the 2nd gen i cant see getting over 200hp being that hard?

 

I did a TII swap I had to replace the drive line, diferential and drive shafts. Not only that my car didn't have any where to bolt up the 5 speed tranny so I had to fabricate that myself. If your car is already a 5 speed you may not have all these problems, but its something to keep in mind. (my car was an auto)

 

it's not hard... it's the issue of cost

you can achieve more power from swapping a t2 as opposed to porting an NA

porting a NA will give you maybe the same power as a t2 but not the same torque.

and when you get past 200rwhp you would be spending the same amount of money as you would for 250-300 hp out of the turbo