S5T2 replace with s4NA short block
 

After many months trouble shooting our S5T2 engine we still are not able to keep it running.
I found a complete S4NA engine/transmission locally that I bought really cheap.
Would it be better to just resale the engine and use the money to rebuild the S5T2 or disassemble the S4NA down to the short block and swap parts over or tear the S4NA down and the S5T2 down and use parts as needed.
Or maybe I'm getting ahead of myself. Maybe I should tear down the S5T2 first and just hold onto the S4NA for a bit.
The S4NA has around 85k on it and runs good.

I vote option 3.

Depends on whether or not the compression of the S5 engine is your actual issue. Check that before deciding on a path.

While not the best thread for this comment, I struggle with your plan to teardown an engine with good compression. Basically despite your laudable efforts to revive your TII, based on your other (family members?) thread, I suspect there is further diagnostic work to be done.

if you boost that Na motor on a stock ecu the timing will blow it.( that goes for the na rotors in the s5 turbo block as well)
sell the n/a block(which isnt on the high desire list despite being good)
and fix the s5 turbo.

or run the s4 block as is, port patch the manifolds and get an ecu capable of adjusting lead timing from the 22 or more it will run stock down to around 12.

find out what you need on the s5, you may could not need a rotor and housing( although very likely) but if not a set of apex seals is worth the s4na.

Thanks. I did a lot of searching and didn't see anything about the timing needing reduced.
We are definitely all amateurs here when it comes to the rotary.

Thanks.
I don't think we are actually to the point where we are getting ready to tear the S5 T2 down, although that has been suggested.

Motherfuc*ing this x 897898798798797.

People dick around for way too long on everything else before checking compression.

I would make it #1 on any troubleshooting list, including "my wipers don't work".

Seriously, it's so easy and quick to do, and compression affects everything. You could get air, fuel, spark and timing right, and low compression will make it run like sh*t.

Follow the trusted methods here and check. I haven't read the other threads, but you're saying 'trouble running', so I guess it's starting and running roughly? Maybe a link to all other relevant threads will help us.

Good luck, and just to be clear, my advice above is not meant for you specifically, just for all spending too much time running in circles (been there, done that).

edit: If compression is low and you open the S5 block and the seals are worn but the housings are ok, then I'd use the seals that are good from the S4, so I guess option 3? Using housings and rotors from the NA is not advised, unless you really know what you're doing and compensate for those changes. But swapping seals (and checking clearances) and such is not too bad. Just confirm that engine seals are the same (cuz off the top of my head I'm not 100% sure and embarrassed to admit it).

I'd say sell that s4 n/a motor. There is virtually nothing on it that will swap over and be of any benefit for your S5 TII. Then continue trouble shooting the TII, starting with checking compression as mentioned if it hasn't already been done.

The S5T2 is a new rebuild. It idled for 35 minutes and just shut off. For a long time (weeks), it would start but would not continue to run. Now, it won't even start.
Right after it died I did a compression test and all faces showed about the same compression.
As soon as possible I will get another compression check .

Thanks. I thought the rotors and housing were swappable.

K, I remember your thread now.

My daughter has a few posts also (alritzer). Her bf is a certified mechanic (not rotary) so he likes to throw his 2 cents worth in also.

Not really. At least not without jumping through a lot of hoops that imo wouldn't be worth the trouble. The s4 rotors are a different weight than s5 so you have to use front and rear counter weights from a s4. Since I saw in the other thread it is an auto you'll have both but you'll have to get a light weight flywheel to bolt the rear on to or a stock s4 flywheel since the rear counter weight is built into the stock flywheels. Now after all that they are higher compression which others mentioned brings it's own potential tuning issues. The rotor housings( and this applies to both s4 and s5 n/a) have diffusers in the exhaust ports that need removing. After that the housings don't have the water passages for the turbo open so those have to be drilled out. The other housings ports don't line up with the TII intake manifolds port though they will physically bolt to the engine. So though technically possible probably not worth the trouble.

S4 n/a replacing a s5t keg? Look up aaron cakes stuff with a 6port turbo set up? You can make it work not a crazy thing now and days there fairly common, i my self am 80% threw my s46port turbo build! Its not much more work, just need a solid standalone ecu and ur fine!

I must disagree with the above. They rebuilt an engine that ran fine for 35min. and haven't been able to figure out why it doesn't want to run now. I say this with utmost respect to all involved.

They're deep enough in it, and don't need to get into the world of 'NA modification for forced induction' and Standalones. What may be fairly easy for you or 'not much more work' may be worlds apart.

Seems to me they just have to double check compression on their S5 block, just to be sure that's ok, then they're just missing something small that's been overlooked.

OP, can you post links to all threads just for people to recap (as I asked before).

I agree. If you want to turbo your n/a using Aaron's write-up, putting all the turbo hardware on the 6p keg is fine. It doesn't sound all that difficult. Would like to do it myself one day. I just like you think it is the wrong solution to his problem This guy already has a turbo car with a fresh rebuild that just won't run for some reason. Leave the n/a stuff alone. It has the potential to just complicate things.

Only trying to tell the OP that if something is wrong and no longer wish to use the s5t that he can indeed use the s4 n/a block thats it thats all. Im not saying its the best option im not saying its the worst option, just giving him some info on possibilities.

you cannot run high comp rotors with a factory turbo ecu(let alone the N/a) the last three post have been horribly incorrect. your s5 ecu will not work with that motor( unless you just dont go into boost. ) I cannot state this enough!

it has been my experience that you can get any rotary to run, even blown/bad ones, so the fact that this doesn't run at all is a bit weird. i skimmed the "ran for 35 minutes" thread, but i would start over.

1. pretend its flooded, pull the plugs, unplug the cas/pull whatever fuse you want to disable fuel, and crank it.

2. compression. if you are a n00b, i'd use a tester, if you're not a n00b, then cranking it with no plugs should be good enough, or even cranking it WITH plugs. there should be 6 even pulses. if there are not, engine needs to come apart. if there are 6 even pulses go to step 3.

3. it is easiest to set timing. hopefully the front pulley is an original. unscrew the CAS cover, and pop out the little plastic plug, put the cover back in. rotate the engine, so it is on the leading timing mark, look in the CAS cover hole, you should see a CAS tooth about dead center. if yes, timing is close enough. if no, reinstall the CAS so it is.

4. fuel. i would pull the upper intake for this, but you may not have to. verify that the fuel line from the fuel filter goes to the primary fuel rail, and that the return goes to the secondary rail. next step is to make sure that the injector wires are on the correct injector. depending on which engine harness you have they are grouped differently. the S5 NA harness, has the two primaries together, and the secondaries together. the JDM T2 is front rotor and rear rotor. Mazda puts a little white tape on the #1 rotor wires.

5. other. the AFM needs to be plugged in, and any vacuum leaks between it and the engine block will cause problems.

6. charge the battery, or put it in a running car or somehow get a fully charged battery. put it in, and crank. if you're lucky, it'll run, and keep it running. if you're not lucky post, and we'll go to harry potter part 6 step 2

Thanks guys.
As soon as we get a break in this snow, I'll get another compression test. I'll really be surprised if it has bad compression but everybody is correct. The place to start is with a compression test.

I'll probably just resale the engine / transmission. I only paid $100 total for them.

Well if u read i did state with a "good standalone" didnt not say anything with a factory ecu. Thanks.

I beg your pardon. Nothing I have posted has been "horribly incorrect". I never said him using the s4 n/a keg was a good idea. If you go further up I even said " Now after all that they are higher compression which others mentioned brings it's own potential tuning issues." I never mentioned the stock ecu because I pretty much told him don't do it.