Miata 1.8L Swap Question - VVT?

There is a 2002 1.8L for sale locally for a price I'd be willing to pay. There's a 1990 Miata sitting in front of my house with no engine in it, as the 1.6L is in my garage and afflicted with various problems.

To get to the point, an aftermarket ECU isn't in the cards right now. Is there a quick and easy way disable VVT and use FM's 1.8L conversion to get this engine in my Miata and be back on the road?

There is but I am typing this from my phone and can't search for it, I believe I read something about it on Miataturbo.net. It is either do nothing, or minor wiring changes to keep the cam timing in one mode.

Thanks. Tonight, I suck at using Google for some unknown reason. I can't find anything, but I guess I'll dig up my Miataturbo.net username and password and see what can be found there.

Since my reading comprehension seems to currently be comparable to that of a 3 year old, I also have to ask, does anyone know if the DIYAutoTune VVTuner can be used with a stock '90 ecu?

IIRC there's a product called VVTuner out there that allows you to tweak the VVT control.

I'm pretty sure that you'll need an aftermarket ECU to run this engine, it's higher compression than the NA engines and I don't think it would be too happy to run via an NA ECU. Plus I doubt that the NB ECU would be too happy to run an NA, either.

There's someone on miata.net who's helping to develop a plug-n-play kit with ECU and everything but it's not looking cheap. I guess the best course of action would be something like VVTuner and maybe an MSPNP ECU.

The best course of action is a Hydra

If you just leave the VVT alone, it'll default to full retard on the cam. It's not a great option, but it's been done. I've also seen people hook it up to an RPM switch so that it's a binary thing - full advance or full retard. Also not ideal.

How easy is a 1.8 swap from a 99-00 NB?

I'd love to go to a Hydra (partly because I like your customer service and would call you with all of my problems) but right now I'm trying to keep cash outlay low and get the car on the road.

Will the compression ratio be too much for the 90 ecu? Is this being over thought at this point?

I'm alright with leaving a bit on the table for the time being as long as I can do this swap without worrying about something weird happening because I don't have a standalone.

I think almost all the NA sensors will plug into the same nb locations and the 2 that don't are the cas and the crank trigger, which are the 2cas things that the vvt controller plugs into. the vvt tuner can downconvert it to NA signal as well as independently control the vvt solenoid. Or at least I think so lol.

MG Bryan wrote: Thanks. Tonight, I suck at using Google for some unknown reason. I can't find anything, but I guess I'll dig up my Miataturbo.net username and password and see what can be found there. Since my reading comprehension seems to currently be comparable to that of a 3 year old, I also have to ask, does anyone know if the DIYAutoTune VVTuner can be used with a stock '90 ecu?

That's the idea; it sends a simulated NA CAS signal to the ECU.

MadScientistMatt wrote:

MG Bryan wrote: Thanks. Tonight, I suck at using Google for some unknown reason. I can't find anything, but I guess I'll dig up my Miataturbo.net username and password and see what can be found there. Since my reading comprehension seems to currently be comparable to that of a 3 year old, I also have to ask, does anyone know if the DIYAutoTune VVTuner can be used with a stock '90 ecu?

That's the idea; it sends a simulated NA CAS signal to the ECU.

Thanks for confirming that for me, Matt. Re-reading things this morning after a few cups of coffee, all of the info on your website is pretty clear.

Since I can swing the VVTuner on the budget I'm working with, I guess this is a go if the engine is still available.

You might have to dial back the base timing a touch with the 90 ECU, but it should work.

You can stick a CAS on an NB exhaust cam with little to no effort, but it sounds as if VVTuner would make that redundant.

As for the 1999-00 into an earlier car, that's cake. Stick that CAS on the exhaust cam and go. The one thing you could use is an RPM switch to flip the VICS over at around 5250 rpm - that IS a binary system that runs in one of two positions and gives a nice little bump to the torque curve. You can leave it in either the high or low rpm position without major problems, but it's worth the low effort to make it work.

Is there any power to be gained from the 99/00 engine over the earlier 1.8?

Better head design. Mazda claimed a jump from 133 to 142 even though they used a crappier manifold.

Keith wrote: Better head design. Mazda claimed a jump from 133 to 142 even though they used a crappier manifold.

Is there a less crappy manifold to use that would bump that even more?

Unless I find something wrong with the engine in question tonight, I'm going for it.

It's a shame this isn't nearly interesting enough for a build thread.

Waddayamean, it's not interesting enough for a build thread? Please post one as that's a swap I'm potentially contemplating myself sometime down the road (or sooner if I blow up the engine that's currently in my Miata).

z31maniac wrote:

Keith wrote: Better head design. Mazda claimed a jump from 133 to 142 even though they used a crappier manifold.

Is there a less crappy manifold to use that would bump that even more?

Other than a header? Yes, the 2001-05 stock manifold. Grab the EGR pipe at the same time and it bolts on. Even looks stock if you live in the sort of area that does a visual check of your engine bay for naughty modifications. In fact, if you live in that sort of area, you'll actually get rid of a really restrictive pre-cat with this modification on a 1999-00...

Oooops, when you said manifold, I assumed intake, not exhaust!

The 2001-05 intake manifold is pretty good, but you have to pull the restrictive VTCS butterflies out of it. The 1999-00 intake manifold works as-is. There's a highly touted JDM manifold out there that gives a bit more horsepower above 6000 rpm at the cost of power down below. Not something I'd choose on a street car.

Didn't they bump up the compression on the 2001-on engine too, or I am misremembering that?

I still have those bad dreams of a high-ish compression Miata motors on ITBs.

BoxheadTim wrote: Didn't they bump up the compression on the 2001-on engine too, or I am misremembering that? I still have those bad dreams of a high-ish compression Miata motors on ITBs.

I have those dreams too. This makes them that much more of a temptation, but for now, I'm working with a strict budget.

If you're interested, I'll post as I put this together. As a plus, everyone will get to make fun of my cluttered, dark garage and my stock suspension.

Dreams? Hmm, maybe I'll take Yolk home tonight. 11.4:1 stroker VVT motor with ITBs, about 175 at the wheels - basically the street car version of my old Targa engine in a cute little yellow wrapper...

Yup, 2001-05 got a compression bump. 1994-97 is 8.8 or 9.0, 1999-00 is 9.5, 2001-05 is 10.0. The MSM is either 9.5 or 9.0, I forget.

MSM is 9.5:1.

I'm dd'ing a 95 with 230k on the unopened stock motor, and the entire drivetrain out of an '01. This thread is relevant to my interests! My oil consumption has increased from high to borderline absurd. Besides removing the vtcs butterflies and getting a vvt tuner, what else should I do to prep for the swap?

Bump because I am at the point of needing a new engine. I am really thinking about this swap.