MX5 Power Loss - How much over time?

[BeirutTaxi]

Just out of interest, If you've had your MX5 dyno'd, how much power has it lost in how many miles?

[Buff Mchugelarge]

I'm planning on putting my mx5 on a dyno to answer that exact question.
18 years and 200k miles my work mates reckon my 1.8 would struggle to make 100bhp,
I reckon it's good for at least 120bhp!

I think it's a lot to do with how the car has been looked after.

[Raify]

Not that much in my experience. I tested a 94 1.8 eunos in about 2008.

It had dropped from 130 to 113 (including being tested with a small hole in the exhaust).

[sbird]

One of mine lost 0.8 bhp in about 100,000 miles.

We ran a number of them on a dyno last year and the year before. My Mk1 was the only Mk1 1.6 to below the manufacture's spec. The rest had gained slightly.

[mcm87]

My '95 mk1 made 1bhp over stock with 100k miles on the clock.

There's no reason they will lose power if everything is properly maintained.

[MX-5 Lazza]

The real truth is that you just can't tell. You can't trust what any dyno tells you.
In reality, dynos aren't there to tell you how much power you have, they are an aid to tuning so that you can monitor the effect of any changes and make sure you get the best tune. Even the operators will tell you that while they do try to be accurate, it's only a guess.
As an example, a few years ago my car was tested at SRR where it made 226bhp. A few weeks later, with no changes at all and with similar weather it was tested at Austec where it made 253bhp. The true figure might be close to one of those or it might be lower than both (I very much doubt it was higher).

[MX-5 Lazza]

mcm87 said:

There's no reason they will lose power if everything is properly maintained.

There is plenty of reason. Components wear. Meters go out of spec.
A bit of wear in the rings & valve guides causing loss of compression, a bit of wear in the valves & tappets, the air flow meter often needs adjustment causing a rich AFR etc. Proper maintenance won't prevent any of those.

[BeirutTaxi]

MX-5 Lazza said:

mcm87 said:

There's no reason they will lose power if everything is properly maintained.

There is plenty of reason. Components wear. Meters go out of spec.
A bit of wear in the rings & valve guides causing loss of compression, a bit of wear in the valves & tappets, the air flow meter often needs adjustment causing a rich AFR etc. Proper maintenance won't prevent any of those.

Do you think refurbishing the cylinder head would help much?

Also, as an owner are there any extra steps aside from oil changes I can take to prevent any power loss?

Many thanks,

Matt

Btw, My Mazda owners manual says oil changes are every 9K, the Haynes restoration manual says every 3k and apparently in Japan it was every six, what is the most suitable do you think?

[Buff Mchugelarge]

It all depends on mileage an how you drive. I reckon I'll do mine every 3000ish, just for piece of mind really.
A race/ track will need more oil changes than a daily driver for example. 9k should be plenty for 90% of people though

[MX-5 Lazza]

Back when I had a Mk1 I used to change oil when the HLA tappets started getting noisy which was much less than 9k but not as low as 3k. Probably nearer 6k.
Now on my Mk2.5 I don't have a schedule at all. I tend to replace the oil after it's had some abuse which normally means a track day. The oil is getting heated a lot more with the supercharger though but the oil-cooler helps a lot.