HugoW

Well, another quite basic conversion. The car is a 1998 NB with 1.6 engine, of course I try to keep the cost down and I am not aiming for 600 whp. We’ll see where I get to, 200 whp would be amazing.I have some steps in mind:

1. Fit external regulator to the alternator
2. Replace ECU and necessary wiring
3. Tune the ECU (and learn how to do that)
4. Fabricate my own manifold and downpipe
5. Fit turbo set-up with intercooler, run at low boost (5 PSI?)
6. Tune ECU some more
7. Pull, rebuild and refit engine with stock internals with the exception of forged rods
8. Tune some more while turning up the boost to 1.000.000.000 PSI. At least.

So I bought the car, it’s rust free and runs decently for a car that did 250k kilometres. I bought an alternator regulator kit and received it, needs to be soldered before I can implement it. I came in contact with James Brandon of DIY-EFI(.co.uk) and he made me a nice offer on a fairly complete package:

1. Speeduino MX5 NA6 PNP - Built & Tested with 2.5 Bar sensor
2. Spartan2 Wideband Kit
3. BMW e36 TPS with BMW TPS Adaptor
4. IAT sensor & plug
5. Silicone Hose
6. Boost Solenoid & plug
7. USB Cable

So I paypalled the cash and that should get me going for steps 1, 2 and 3.I found a once-fitted but unused Garrett GT2554R on the Dutch version of Graig’s List (marktplaats) and bought it. The gaskets are off course missing but it is clean and nice. I also bought a Torsen dif on ebay UK, but shipping doesn’t seem to happen yet. I’ve opened an issue on ebay, hope either I get the thing or at least my money back…Oh, and last but not least I am rebuilding the house we just bought, which takes priority over building the car. I think the car will be driven and enjoyed more than tinkered on this summer. But if there is progress or if I have questions, I will be here.

Cheers,



Hugo

DaWaN

Sounds like a reasonable plan and props for learning how to tune before going to boost.
Nevertheless, I have a few comments.

If you would like to put in forged rods at some point, it makes sense to prepare everything in front.
In that case you will really need upgraded fuel injectors and an upgraded clutch as minimum.

The electronics for the NB and NA are not the same. Your NA ECU will not be plug and play, the NB has other ECU plugs.
Also the triggers are different from the NA CAS as the NB has a cam/crank trigger like the 1.8 NB.
The NB has a variable TPS from the factory also.

As for the manifold: Kraken has a cast 1.6 T25 manifold. I think you will not match durability of that manifold with a fabricated manifold and given that you are also doing some construction on your house, I would not even bother with making your own manifold personally.

As for the diff: do you know which car it was taken off? Later 6 speed NB's in the UK have the Super Fuji diff which you do not want. Also 3.6:1 diff ratio for the 5 speed may be something you do not want either. Also remember that the NB 1.6 has exactly the same diff size as the 1.8 (NA/NB).
So you do not have to worry about the diff breaking. If you are not a super aggressive driver you might be OK with the standard open diff for a while.

HugoW

Thanks for all the info. The seller says it does plug in and TPS and such are needed, but I will investigate further after your warning before he ships.

Why would I upgrade anything else in the engine, apart from an overhaul, if only the rods are the week point before 300 whp? What else would make sense?

Making the manifold is a hobby of mine. True, better items are readily for sale but I love the puzzle, the cutting and welding, and having my own home-brew manifold. I made my first one 20 years ago for a BMW E42 motor, and some more for Minis later. I just like doing it, I have all fall and winter to do so. I am not in a hurry. For me, the build is just as important or maybe more than the result.

Clutch is of course a must-have, forgot that on the list, and injectors I presume I should do as well. I have considered a rising rate fuel pressure regulator, worked great on my Minis, but I don't know if the ECU gets that and bigger injectors seems the proven method.

Cheers,

Hugo

Caterpillar

Hey Hugo,

Nog meer Nederlanders hier!

I have a few comments on your plan!

1. Speeduino MX5 NA6 PNP - Built & Tested with 2.5 Bar sensor
   There is a difference in ECU connector between the NA and NB. If you want a plug and play solution you should be searching for a NB ecu.
   I also thought that Ithe Speeduino ECU was not very accurate when it came to spark angles... Should be here on the forums. (Searching is easier through google: Search for the topic and add site:miataturbo.net
2. Spartan2 Wideband Kit
   If this one is secondhand, you might want to think about a replacement wideband Sensor to replace the used one. (Just the lambda sensor, not the controller). Wideband sensor get old and will give false readings.
3. BMW e36 TPS with BMW TPS Adaptor
   You already have a working TPS. This is only necessary for NA 1.6 cars.
4. Pull, rebuild and refit engine with stock internals with the exception of forged rods
   I would think a bit longer about this step. If you want to have more than 250 RWHP you need to upgrade a few parts.
   Block: I would start with a 1.8 and even better the VVT option because of the better spool and response. Only rods would be sufficient but if you have detonation you will break a piston. Next step would be pistons and BE oil pump to be save.
   Gearbox: The 5 speed gearboxes can only hold 250ft.lbs (about 330NM). The same as the stock rods. So if you want to run more you should also upgrade too a 6 speed box. This box has a shorter gearing so you also want to have a longer diff.. Last time I checked prices were around 1000 euro for a diff and gearbox.

I think if you search for the topics you can find some more information. If can't find anything send me a pm.