common issues with engines in 1991 NA?

Discussions relating to Turbochargers, Superchargers, Induction, Engine Mods, Exhaust Mods, and other items specifically to make your MX5 or Roadster put out more power.

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Athom1991BRG
Hey. They are NOT Training wheels.
Hey.  They are NOT Training wheels.
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common issues with engines in 1991 NA?

Post by Athom1991BRG » Wed Oct 23, 2019 12:16 pm

Are there any common issues with the inline 4 engines in the 1991 mx5s? I heard somewhere that cooling can be an issue, but haven't been able to find anything. I am looking to start increasing the power of the inline 4 but don't want to destroy it in the process. If no big issues are there any easy HP/general running mods that would be a good starting point. Thanks.

Keith Jones
I count 5-s in my sleep
I count 5-s in my sleep
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Re: common issues with engines in 1991 NA?

Post by Keith Jones » Wed Oct 30, 2019 11:24 am

There are really no major issues to be worried about providing the engine has been well maintained - regular oil and coolant changes, radiator not blocked etc. The stock engine can be increased in power up to about 200 bhp before you need to look at improving cooling.
A quick mod that a lot of people do that doesn't require any component changes is to advance the ignition timing to 14 degrees BTDC from the stock 10 degrees. This provides a bit more mid range power but needs the use of 95 octane petrol. Beyond this you are looking at either forced induction or high compression normally aspirated, with new exhaust headers etc.
What sort of power increase are you looking at?

Athom1991BRG
Hey. They are NOT Training wheels.
Hey.  They are NOT Training wheels.
Posts: 2
Joined: Wed Oct 23, 2019 12:07 pm

Re: common issues with engines in 1991 NA?

Post by Athom1991BRG » Wed Nov 06, 2019 11:52 am

Keith Jones wrote:
Wed Oct 30, 2019 11:24 am
There are really no major issues to be worried about providing the engine has been well maintained - regular oil and coolant changes, radiator not blocked etc. The stock engine can be increased in power up to about 200 bhp before you need to look at improving cooling.
A quick mod that a lot of people do that doesn't require any component changes is to advance the ignition timing to 14 degrees BTDC from the stock 10 degrees. This provides a bit more mid range power but needs the use of 95 octane petrol. Beyond this you are looking at either forced induction or high compression normally aspirated, with new exhaust headers etc.
What sort of power increase are you looking at?
Ah that's good news! I'm looking at getting it up to around the 200bhp mark, would use of a turbo be the best option?

Keith Jones
I count 5-s in my sleep
I count 5-s in my sleep
Posts: 311
Joined: Thu Jul 06, 2006 6:30 pm
Location: Waiuku

Re: common issues with engines in 1991 NA?

Post by Keith Jones » Sun Nov 10, 2019 8:08 pm

You could go with either a turbo or a supercharger. You won't get anywhere near that power normally aspirated. MX5 engines don't have a good head design, unlike Toyota or Honda. You will need around 8 to 10 psi boost to get 200 bhp. Turbos are much more common, so there is a lot of info around on what to do.

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