Kraftwerks 06-13 Miata Supercharger on 1.8 EU Spec MX5 NC1 with stock internals
 

Hello guys – Greetings from Greece!

First of all, my respect, you have got a great forum and a great source of info.

I own a 2008 European spec 1.8 MX5 NC1 and I’m planning to install this kit : 150-10-0613 - Sport Compact - Supercharger Systems - KraftWerks USA which is designed to work with the 2.0 MX5 NC with stock internals.

Kraftwerks is reporting 250Whp /180 Ft/Lbs @ 7400 rpm for the 2.0 lt engine with a 85mm pulley.

The two engines are ‘almost’ identical (if you know any kind of component wise difference e.g. stronger metals etc please comment):

1.8
123 lb.ft @ 5000 RPM
124 bhp @ 7000 RPM
bore x stroke 87.5 x 83.1

2.0
138 lb.ft @ 5000 RPM
158 bhp @ 7000 RPM
bore x stroke 87.5 x 83.1

There are several installations of the Eaton MP62 SC the ex Cosworth system now sold as FM SC or BBR SC in Europe on 1.8 engines.
There are at least two well known tuners (BBR in UK and SPS in Germany) that have installed these kits on 1.8 with stock internals and they working without issues.

BBR is reporting 176 lb.ft and 217 bhp and SPS is reporting 196 bhp (some difference may occur from different components thought, like exhaust etc).

Both tuners are using larger pulleys on the MP62 to reduce boost to 6-7 psi, since MP62 is puting stress on the rods early on at lower RPM.

A larger pulley (95mm) on the Rotrex to bring boost down, is not an option – I have checked with Kraftwerks - because the torque and power output are moving north of 5000 RPM.
On the other hand Rotrex is a very different animal from the Eaton MP62.

Taking all the above into account, I come to the conclusion that since torque will not be higher than 176 lbs.ft (as per BBR kit, already reported by KW 180 lb.ft for the 2.0) and will be outputted in higher RPM due to Rotrex operation and power will not exceed 200 bhp, my 1.8 engine will be safe to run with this kit and stock internals.

Not sure is the 10psi boost will affect anything, though.

As you understand I would like to avoid rebuilding the engine with forged parts since the cost is not justifying the results and I'm not planning to build a racing miata or go above 200hp.

I would appreciate your comments – suggestions, from your experience on SC/Turbo NCs with stock internals before I make my final decision and deposit the cash for the Kraftwerks kit.

You'll probably be fine if your main concern is torque breaking/bending rods as the Rotrex makes so little torque. You can always make a restrictor to reduce power if you are worried.

Is the block on the 1.8 the same as the 2.0? You should be sure so the mounting brackets/plates all line up.

I'd be most concerned about Kraftwerks and their (bad) reputation for quality and customer service. Might be hard to get support being in Greece and on a slightly different motor than the kit was made for.

Yes the block is the same, but our local workshop has a certified Mazda technician with a lot of experience in engine upgrades, so this is my last concern if there is any kind of issue there.

So far communication with Kraftwerks is OK they seem keen to help; I have not seen any complaints for quality about this kit from people that bought it in the US (at least in the related miata forums).

Sounds like you are good to go then... My only complaint problem with Kraftwerks has been their denial of belt issues on the kit that I have been working with (early NA kit). In any case- if the NC kits have good reviews from other users, and the blocks are the same I'd say go for it. I think the Rotrex unit is excellent.

Thanks for the feedback, very helpful