Eaton M90 on miata?

Ive seen a few builds around the interwebs but was wondering if you guys had an idea how well an earon m90 would work on a 1.8 miata.

I have been wondering the same thing, as well as how to do it cheaply.

I would think it is too big for the 1.8

The M90 is apparently sized for 3.0-5.0 liter engines. I would think an M45 would be a better fit.

In reply to DeadSkunk:

Thats what ive read but at the same time people claim to have run them.

M62 would be a decent fit as well, I think. The M90 would work, but you'd probably have to spin it pretty slow unless you're planning on running a crapload of boost. Then again, that's not a bad thing, as spinning it slower would likely keep the heat down...

The M45 is what the old JR SC kits used,still running one on my 1.6 but its usefulness is marginal at best.I run it thru a massive intercooler now and its better than the water to air it had when I got it,the heat this thing makes its crazy.

Have a TD04 for cheap to replace it with when I have to time to fab the manifold and down pipe.

The answer(pun intended) is turbo every time for an affordable means of boosting a small displacement engine.

Seems like my best bet is to save the m90 for something later.

The M45 was too small for the 1.6, it's way too small for the 1.8. It's a 150-at-the-wheels kind of supercharger. The MP62 will do low 200s when set up properly, which is a pretty good place for a Miata to be -- a big upgrade over stock, but not so high that you start running into major problems cooling them or shattering transmissions on a monthly basis.

A bunch of people have talked about M90s/MP90s, there's one build thread on miataturbo.net about one, but not a lot of conclusions about how well it works overall. Most people who want more blower than the MP62 wind up with twin screws, I think.

Always a chance I may swap the engine in the miata to something else that this may fit on as well

I had an M62 on my 2.0L Focus. The kit was made by a subsidiary of Ford so I assume that it was the correct size for the motor.

On an older incarnation of this forum, I crunched all the numbers to run an M90 on my 1.6L Nissan Sentra.

To keep the boost down, you'd have to spin it so slow, it is totally out of its efficiency zone. To spin it efficiently, you'd be into stupid boost.

Some guy on the Nissan forum I was frequenting at the time did all the work to mount one on his 1.6L Sentra, didn't crunch the numbers, and didn't listen to my warning. He was making boost at idle, but it ~did~ limp its way back from the head-gasket-blowing trip around the block.

In reply to SkinnyG:

How,much boost are we talking

Fitzauto wrote: In reply to SkinnyG: How,much boost are we talking

Googling suggests the M90 has a 12,000 RPM redline and pumps 1.475 L per rev. If I remember how to calculate this properly, you want to pulley it for 1.66:1 so that 12K blower RPM is at 7200 engine RPM. That gives you 2.4L per engine rev, vs 900 cc/engine rev on the 1.8L Miata motor (it's a 4-stroke, so divide by 2). That's a theoretical 2.66x atmospheric pressure, or about 23 psi of boost at sea level.

In reply to codrus:

That is alot for the little miata

Fitzauto wrote: In reply to codrus: That is alot for the little miata

A stock motor, certainly. Mine has a built motor, I've run that much and it's fun. :)

So, how deep do you have to go to have a reliable 23lbs of boost? (this excites me)

Forged pistons, sure. Probably rods. Beyond that??

In reply to SkinnyG:

Im curious about this as well. If the motor could be built for it I dont see why I shouldnt do it.

In my motor I have pistons (Supertech), rods (Carillo A-beam), ARP studs (both head and main), and an ATI super damper. Stock crank, stock block (well, bored obviously). The head has been worked over as well, but that's more for flow than for reliability. I use a turbo, not a blower (GTX2863R), and I usually run it at 20 psi (235 kpa), I've had it up as high as 23-ish, but it pings enough up there that it's not actually making any more power after I retard the timing to stop the pinging. Should have gone with the 8.5:1 pistons instead of 9:1. :)

I have a build thread over on miataturbo.net (here) with lots of pics/etc. Most of the parts came from FM, Keith can give you lots of info.

The biggest reliability problem with making that much power on a Miata motor is the transmission. Well, that and the throttle body -- this is the second engine I've built because the first one broke the throttle body and ingested a screw at Laguna Seca a few years ago.

you'd probably be better off running an m62 off of an a pre-96 Buick Park Ave (least likely to have abuse on it)

In reply to codrus:

Keeping your compression as-is is probably fine to push a little more boost. Lower compression means slower spool, etc. so it's a last resort, IMO. Work on cooling the intake charge better (water/meth is an option if you can't get it cool enough with a good intercooler). And if there's cooling system mods you can do to the engine to cool the head better, that helps too.

If I end up going with a blower Ill probably try to find an m62 or a cebtrifugal. This m90 will probably go on another project thats in the pipeline.