Law of diminishing returns on an NA6?

llmoose · Postby **llmoose** » Sun Feb 15, 2015 7:37 pm

I'm wondering what sort of gains can be made on an NA6 without breaking the bank and going silly.. What gets best bang for buck?

I was considering forced induction and would really love too but the resale/legal repercussions are just too much to worry about it.

Is there a decent guide to getting good naturally aspirated power out of the 1.6? I figure they sit around the 70rwkw from the factory, would 100rwkw be attainable without a rebuild? The car is a weekender so I don't necessarily need it to be civilised but don't want a track pig either...

Magpie · Postby **Magpie** » Sun Feb 15, 2015 7:56 pm

Best bang for buck is a good alignment, decent tyres at the correct pressure and suspension mods.

For power read this http://forum.miata.net/vb/showpost.php?s=5caa4f206f8c252c74b7202188becab1&p=5704021&postcount=24, it is written for LHD cars and a BP engine but is still relevant!

I can give you an idea on what needs to be done to get about 150 RWKW naturally aspirated from a BP motor.

llmoose · Postby **llmoose** » Sun Feb 15, 2015 8:02 pm

Excuse my ignorance but what is a BP motor?

smy0003 · Postby **smy0003** » Sun Feb 15, 2015 8:31 pm

1.8l motor from the later 5s.

Postby **NitroDann** » Sun Feb 15, 2015 8:37 pm

You need to turbocharge.

Its actually a simple, reliable and easy process, easily reverted and you will not regret it. But yeah its not a pod filter and a muffler.

Read this thread to see just how simple it can be, its a very detailed walkthrough. This car made 105rwkw at the end of the thread, and now makes 135rwkw with an intercooler and better intake.

viewtopic.php?f=81&t=58863

llmoose · Postby **llmoose** » Sun Feb 15, 2015 9:01 pm

The more I read, the more that makes sense. I really didn't want to do it but idk maybe it is the way to go once I've got everything sorted. Cost isn't really an issue tbh I just don't want to have to cut and drill anything. I don't want any signs at all that the turbo kit was there...

project.r.racing · Postby **project.r.racing** » Sun Feb 15, 2015 9:43 pm

If cost isn't an issue, why buy a 70kW car? Buy something with power...

As for the next owner, I'm doubtful they will care about provenance or a turbo fitted, as they are buying a sub $4K car.

llmoose · Postby **llmoose** » Sun Feb 15, 2015 9:50 pm

1. It was cheap and I was looking for a manual, RWD car that I can slap on club reg and mess about with.

2. I drive much more expensive and powerful cars daily so there is no need for speed. Simply a hobby.

davekmoore · Postby **davekmoore** » Mon Feb 16, 2015 7:23 am

The factory's accountants and engineers worked out where returns started to diminish, and stopped at that point.

NitroDann's is the other correct answer.

sailaholic · Postby **sailaholic** » Mon Feb 16, 2015 9:56 am

I made a 131 hp from my 1.8 which is pretty close to your 100 kw. I didn't touch the bottom end but did do the following. Full cylinder head, chambers 1 mm oversize valves, port polish, light skim, reground cams as big as I could fit without welding. Mazda speed quad throttles, rx8 injectors, maxim works headers into a 2.25 full exhaust and standalone ecu and a low temp thermostat.

Others have apparently made more with less. That could be differences between dynos as the one I used I found out is a known heart breaker. Tuner was fairly impressed and a naturally bda cosworth made only another 20-30 hp threw week before.

I suspect the head is probably a bit too much for a three stock bottom end as I don't have a lot of torque below about 3500 rpm.

Rough costs from memory
Cyc head and cams 2000-2200ish. It was supposed to be 1500 but needed new valves, lifters and then freight Brisbane to Melbourne added up,
Throttle bodies 2000
Ecu and wideband 1700
Throttle body set up and tune 700
Exhaust Inc headers and new cat. 1700 odd

Add to the the supporting things like timing belts, head studs, coolant reroute, gasket set thermostat and there is close to another 1000.

Cost benifit is a very personal thing but I'd say a 100 kw NA b6 is part the cost benifit cut off. Looking back at the results it would have been past mine and I'm a naturally aspirated tragic.

Ice88 · Postby **Ice88** » Mon Feb 16, 2015 6:48 pm

Any build can be cheap (or cheaper really), providing you have the skills and access to the knowledge to make it possible.

Im about 5.5k in and about 184hp on a hub dyno. Some of that money got chewed up with being given the wrong head bolts, requiring disassembly, block to be helacoiled and then reassembled.

There is no sound better then a highly strung NA engine revving its tits off at least IMO.

Magpie · Postby **Magpie** » Mon Feb 16, 2015 7:13 pm

184hp for $5.5k naturally aspirated PLEASE EXPLAIN!

project.r.racing · Postby **project.r.racing** » Mon Feb 16, 2015 9:11 pm

Magpie wrote:184hp for $5.5k naturally aspirated PLEASE EXPLAIN!

does some of the work himself.
2.0L engine, not a 1.6L.
hypoid gearbox fwd car, not rwd car with heavy tailsaft.

Magpie · Postby **Magpie** » Mon Feb 16, 2015 9:47 pm

My bad I thought this was about either a NA6 or a BP engine. I guess it was also 184HP and not 184 HP at the wheels.

Ice88 · Postby **Ice88** » Mon Feb 16, 2015 10:06 pm

project.r.racing wrote:
Magpie wrote:184hp for $5.5k naturally aspirated PLEASE EXPLAIN!

does some of the work himself.
2.0L engine, not a 1.6L.
hypoid gearbox fwd car, not rwd car with heavy tailsaft.

As Ryan said, using an FS engine (2.0).

Had the short block assembled. (Rods, bearings, pistons) Rest I assembled myself save money and its fun

Magpie wrote:My bad I thought this was about either a NA6 or a BP engine. I guess it was also 184HP and not 184 HP at the wheels.

Its measured at the wheels just not on a rolling road. So your usual drive terrain losses minus wheels.

174 whp was what I got at the wheels using 30lb tyre + rim.