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So, if I wanted to be able to rev the little M13A to higher RPMs reliably, what mods should I do?
I know these engines start to lose power over 5500 RPMs, or at least that's what I can feel while driving if I'm not mistaken, but I want to prepare the engine to be able to reliably be revved to 7000, any advice?
Peak engine power occurs at 6,000rpm (peak torque at 4,100rpm) and the engine redlines at 6,500rpm. Once you pass peak torque the engine feels as though it accelerates slower, once you pass peak power you need another gear. I am not sure what you hope to gain by going over peak power (6,000rpm)?
Let's just say you do want to rev to 7,000rpm, you probably want to change the valve springs, possibly the valves and pistons, that always assumes HD versions are available. You might also need to adjust the timing to avoid pre-ignition.
Then you might find that the con-rods or crank are not really suited to rpm greater than 6,500rpm.
Note sure if the Jimny has a rev limiter, I did see one spec sheet that said 7,000rpm, so you might need to raise this up a bit.
If it was me I would be happy to stick with changing up 6,000rpm and save a lot of money/blown engine.
2020 blue SZ5 (one of the last to be registered in the UK)
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog
For what I've seen, you're right, and the engine cuts spark at 6750 if I remember correctly, but I'm a sucker for high revving engines and since I'm trying to make my little car into a stupid replica of an old n/a rally car, I'd love to have the engine rev higher.
I already knew about springs but never thought about the crank not being able to sustain those levels of abuse
I don't really know if the crank/con-rods will take the extra revs, it's just push the power/rpm above the rated nearly always results in reduced engine life, sometimes dramatic/sudden.
Rather than rev the M13A engine higher why not look for a M15a/M16a, that wil give you a good power increase?
2020 blue SZ5 (one of the last to be registered in the UK)
Ex 2011 Blue Jimny SZ4
Northumberland Jimny Blog
I could get a 15 or 16 but I posed myself the objective of leaving the stock engine in the car, or at least not to swap it with a different engine type, even though one of the things I want to do in the distant future is to bore it out to 1.5 liters
M15 & M16 look just the same as M13 (only difference numbers stamped on side)
Head is same on all 3 so just fit M16A ~100bhp
OR spend 2.5k+ to gain 100rpm
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