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Coverting 1.6 to 1.8
FFMan - 11/4/21 at 07:26 PM

Just got my MX5 based 1.6 Locost out on track, and whilst i did have plans to go FI before it's first outing, I found that the balance etc was fun, and I don't think it needs 200hp, not sure it would actually improve it that much versus the cost and hassle and running.

So for a mild boost i thought i'd swap the 1.6 for a non-vvt 1.8. I found the excellent flying miata write up which is helpful.

I just wondered, are there any physical/dimension issues to be aware of that might make the swap harder ?

Will i need different engine mounts ?
Is the 1.8 taller ?

I saw recommended to use a Mk2 head on a Mk2.5 block, or could I just get the mk2 and deck/skim to improve compression ?

thanks

Nile_rt - 11/4/21 at 08:44 PM

I did a similar swap in my old mk1 mx5. Went from a 1.6 to a 1.8 vvt engine.

Mounts are exactly the same but the engine is longer at the front. The vvt head is a bit taller because of the vvt gubbins but if you can get it to fit and have an ecu for it, it's a lot better than non vvt.

FFMan - 11/4/21 at 09:00 PM

quote:
Originally posted by Nile_rt
I did a similar swap in my old mk1 mx5. Went from a 1.6 to a 1.8 vvt engine.

Mounts are exactly the same but the engine is longer at the front. The vvt head is a bit taller because of the vvt gubbins but if you can get it to fit and have an ecu for it, it's a lot better than non vvt.


thanks - i was planning on non-vvt to keep the stock ecu, plus research seems to suggest vvt is worth about 3 hp but was mainly to meet emissions. Might be better but not worth a new ecu type better by most accounts.

longer is ok, there is space for that

Does it mate to same gearbox ?

Nile_rt - 12/4/21 at 08:51 PM

VVT makes lots more torque in the mid rpm range compared to non vvt. You could use the standard ECU from a vvt car.

Yes the gearbox patterns are all the same. Any starter motor will work but the later mk2.5 ones (maybe mk2 too) are a lot smaller and lighter.