Ok let's assume a few things just for debate's sake. Let's assume one has an engine which is getting a bit weak and is looking to purchase either a)a Mazda reman or b) a used, low mileage Cosmo motor. Both have warranties that the compression is good just to equal things out a bit. There wasn't money for a full-on rebuild with all the goodies, ceramic seals, monster street port, cooling and oil mods, extra pins, etc...not just yet anyway. The rest of the engine package equation is full mods including front mount, full exhaust, and a large single turbo like a T78.

Here's what I'm thinking and please, give me a bit of feedback if I'm going in the wrong direction....

I'd rather go with the Cosmo. First, it's a factory -built engine and thus the tolerances and clearances will be better than a reman and thus should hold up a bit better.

Second, the induction side (intake manifold uppper/lower and intake ports) is more efficient on the Cosmo, ie. they're quite a bit bigger. Less restriction means more hp at similar boost settings versus that of the stock FD engine.

On the downside, some have suggested that it won't bolt right in, specifically one bolt near the starter mount won't line up on the bellhousing with the 5 speed setup. There may also be clearance issues between the hood and the upper intake manifold?

Additionally, the exhaust ports are smaller. Now spool-up with a stock motor on a T78 isn't exactly resonsive below 4K rpm :-) Would the smaller exhaust port size further increase lag due to restriction or are the smaller port shaped better for more velocity and thus would spool the turbo faster?

It was also mentioned that the sleeves could be removed and replaced with REW sleeves. Can this be done WITHOUT taking the motor apart? Are aftermarket sleeves offered that would work?

I've done a search and there seems to be lots of conflicting info on whether this would work or not. The local rotary specialist has an RE coming in within a week. Some say it uses a different crank sensor but one could swap the FD parts on without much effort correct?

Additionally, if I remember correctly, SR Motorsport's project car (the red 93) used a Cosmo motor instead of the original REW.
That's about it....what do you all think?
Michel

 

Oh an additional bonus for the Cosmo, no core charges.
Michel

 

Sounds like your really into your cars... know them pretty well... mabey the next step should be engine building??? if you redid the motor your self you should beable to rebuild it cheaper then a j spec 13b... and it would be stronger... as long as the rotor houseings are good and the rotors are good it should be ALOT cheaper to rebuild...

 

That would be an understatement! :-) I do want to build up an engine and I'll most definitely be purchasing a Pineapple motor. This is sort of to hold me over as I want to go all-out with the rebuild and do it right once and how I want it done. I don't want to skimp the first time and wish that I'd done things differently. I also thought it'd be an interesting experiment with the Cosmo engine, LOL. Just to see...but if it isn't going to work without tons of fabrication, then I'll opt out on the Cosmo motor.

Oh, for the crank signal issue, all you have to do is swap out the front covers.
Michel