What would win in a race, a series 4 n/a or a series 5 n/a? Assume they have nearly identical mileage (compression). It just seems like the s4's are usually faster than the s5's, even though the s5's were faster when they were new.

a S5 should have more power. all things being equal a S5 should be faster although they weigh a little more

yeah, s5 should outperform s4.

what/how are they heavier?

the s5 has those damn seat belts, i dunno where the rest of the wieght comes from



mike

series 5 made more options standard; i.e. there were no manual steering series 5s. Some added bracing in the doors and dash area also I believe. The series 5 also had the added benefit of the VDI manifold and lighter higher compression rotors which account for its increased performance.

If that's so, can I get these parts from an S5 and put them in an S4? ('86 is s4 and '90 is s5, right?)

you can swap over the manifolds but it is not just a plug and play. The rotors would require an entire rebuild. Some people even choose to use the series 4 manifolds whem doing a large port job on an NA. I have no first hand experience with any of these swaps. I have just read about it.

yup, the cool thing about mazda is that they are lazy about changing things, so you can take your 86 and bolt all the 89 stuff on it



mike

Cool, if I ever get around to rebuilding this '87 engine I have, I'll look into that '89 stuff. My ultimate plan is to rebuild it (prolly years away, if my '86 dies), do everything that money will allow while I have that engine open (port, '89 parts), and put it in my '86. In my world, no ultimate plans have actually occurred yet, but as long as that '87 is wasting away in my yard the potential is there.