Naturally Aspirated tuning, what next?

Technical Area Engine, Transmission, Exhaust etc
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  1. My model of MX-5 is: 1990 1.6

hi all, I have a hankering to do some naturally aspirated tuning. I have a 421 stainless exhaust all the way back, some upgraded HT leads and Spark plugs and a K&N cone filter. But what can I do next to get to around 150hp? Cams? Port and polish?

Any recommendations would be great!

Thanks

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I used to have an MX5 racing team a couple of miles up the road who would do some work on my 1.6 Eunos if they had time.
When I asked them what they did to their cars for race days they told me they didn’t do the timing mod as the power was the same as stock, just lower down the rev range - pointless for red line race conditions. They skimmed the head and ran a standard air box but with Piper Cross filters.
I think that was all they were allowed.

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Did the 421 exhaust & K&N make much of a difference?

Have you considered individual throttle bodies as the next move, as well as porting etc?

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Well, i havent actually fitted the 421 manifold as i havent had time, so I will let you know! I have the matching cat-back already fitted and that made a tiny difference

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which system did you pick? I’m thinking of Gravity Performance. Did the catback make noticably louder? Hoping to not be too ‘Max Power’ with the exhaust noise!

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It was definitely louder with a great zingy stailess steel sound. I had to get rid of the cat last minute so got a de-cat pipe instead which I think has made it too loud.

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I would say next step is cams. But I would consider the power/torque profit vs the cost. Are you willing to spend 600-1000 for 15hp extra power? Because you will also need a new map. I don’t think the 1.6 is the right engine to spend a lot of money on. Maybe you could swap it out for the 140hp 1.8.

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Decat pipe?
It may well introduce a very tiring boom-resonance period between 60-70 in top- (3200 rpm to 3700 ish)
Every engine has it’s what I call “wow wow wow” resonance period…
It was so prominent on the Cologne Capri 2.8V6, it could actually eat the part fibre chain sprocket cog.
You will never notice it in saloon / big cars due to the engine’s isolation, engine mounts, and sound proofing.
See how it goes…but TBH if it’s the one I’m thinking of, it’s NOT a silenced by-pass, but pretty much straight through. It’s just not worth it really.

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