Longevity of Direct Injection Engines

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Dear Motorhead,

I’ve been a SUPERTRAX reader for 16 years now, and your magazine is the BEST. Thank-you!

My question is regarding modern 2-stroke longevity. I’m aware that in order to produce less emissions, more HP and better fuel mileage, leaner fuel mixtures and hotter running temps are required.

This makes me question the longevity of these engines compared to the 2-strokes of old, which ran much richer and ran at least 6000-7000 miles without any required maintenance (top-end rebuilds, etc.) DI and CFI engines are relatively new, and my next purchase will be 2-stroke powered.

Do we have reason for concern?



Thanks for your email!

You are right in your assumption DI 2-strokes run hotter. However, current Rotax E-Tec mills (600 and 800) both use liquid cooled crankcases – something not required with carbs as fuel was actually doubling as coolant.

Combustion temps are up however current DI E-TECs have very sophisticated piston coatings to disperse heat. CFI and SDI engines are not that much hotter running than carbed models. It’s really DI which is taking 2 strokes to new limits.

So, will these engines last? According to the info we received just last week at Snow Shoot in West Yellowstone, Montana, Ski-Doo claims we can expect at least 10 to 15 K miles out of E-TEC engines without any reliability problems.

To make this a little more understandable look at the record of reliability the current crop of Evinrude E-TEC mills have earned.

DI’s can use way, way less injection oil because they do not wash oil out of the crankcases – with fuel entering the combustion cycle at 15 degrees before TDC after the exhaust port is closed there is almost no opportunity for fuel to wash down cylinder walls, rings and certainly not the bottom end where only air is being scavenged.

Time will tell for sure but I don’t think you should fear DI 2-strokes. Remember this – even 4 strokes can break and what type of motor would you much rather pay to fix?

Motorhead Mark

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