Motorcycles

KTM releases full details of new two-stroke engine

KTM releases full details of n...
The 2018 KTM 250 and 300 EXC TPI enduro models enjoy a wide power band, fuel consumption that can compete with four-strokes, and comply with modern emission caps
The 2018 KTM 250 and 300 EXC TPI enduro models enjoy a wide power band, fuel consumption that can compete with four-strokes, and comply with modern emission caps
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KTM breathes new life to the two-stroke engine with the new 250 and 300 EXC TPI
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KTM breathes new life to the two-stroke engine with the new 250 and 300 EXC TPI
Only the 2018 graphics, or a careful look at the fueling system behind the cylinder will reveal that this is a next-gen fuel injected KTM EXC TPI
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Only the 2018 graphics, or a careful look at the fueling system behind the cylinder will reveal that this is a next-gen fuel injected KTM EXC TPI
KTM suggests that the new two-stroke EXC TPI enduros deliver as wide a power band as the four-stroke models
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KTM suggests that the new two-stroke EXC TPI enduros deliver as wide a power band as the four-stroke models
The application of a fuel injection system to the KTM EXC TPI models had a minimal impact in its total weight, adding less that a couple of kilos
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The application of a fuel injection system to the KTM EXC TPI models had a minimal impact in its total weight, adding less that a couple of kilos
The 2018 KTM EXC TPI is equipped with a new exhaust system
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The 2018 KTM EXC TPI is equipped with a new exhaust system
The 2018 KTM 250 EXC TPI is visually identical with the 300
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The 2018 KTM 250 EXC TPI is visually identical with the 300
The 2018 KTM 250 and 300 EXC TPI cylinder makes use of proven tech like an exhaust powervalve
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The 2018 KTM 250 and 300 EXC TPI cylinder makes use of proven tech like an exhaust powervalve
Behind the fuel tank of the 2018 KTM EXC TPI sits the new engine management system, as further behind a 12V 2Ah Li-Ion battery provides juice for the electric starter
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Behind the fuel tank of the 2018 KTM EXC TPI sits the new engine management system, as further behind a 12V 2Ah Li-Ion battery provides juice for the electric starter
The rear view of KTM's EXC TPI fuel injected two-stroke engine
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The rear view of KTM's EXC TPI fuel injected two-stroke engine
The new two stroke engine of the KTM 250 and 300 EXC TPI is equipped with both a kickstarter and an electric starter concealed below the throttle body
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The new two stroke engine of the KTM 250 and 300 EXC TPI is equipped with both a kickstarter and an electric starter concealed below the throttle body
The oil tank of the 2018 KTM EXC TPI models sits under the main frame beam and houses a pump that injects precise amounts directly into the throttle body. Its filler cap sits right behind the steering head
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The oil tank of the 2018 KTM EXC TPI models sits under the main frame beam and houses a pump that injects precise amounts directly into the throttle body. Its filler cap sits right behind the steering head
The left hand side of the two-stroke engine of the 2018 KTM EXC TPI houses a 196 W generator, the same as the one used in the four-stroke EXC-F models
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The left hand side of the two-stroke engine of the 2018 KTM EXC TPI houses a 196 W generator, the same as the one used in the four-stroke EXC-F models
The throttle body of the 2018 KTM 250 and 300 EXC TPI engine is made by Dell'Orto and is equipped with an idle adjustment knob
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The throttle body of the 2018 KTM 250 and 300 EXC TPI engine is made by Dell'Orto and is equipped with an idle adjustment knob
The KTM 300 EXC TPI in action
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The KTM 300 EXC TPI in action
KTM suggests that the use of an electronically controlled fuel injection makes the two-stroke engine of the EXC TPI enduros automatically adaptable to any riding conditions
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KTM suggests that the use of an electronically controlled fuel injection makes the two-stroke engine of the EXC TPI enduros automatically adaptable to any riding conditions
The 2018 KTM 250 and 300 EXC TPI enduro models enjoy a wide power band, fuel consumption that can compete with four-strokes, and comply with modern emission caps
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The 2018 KTM 250 and 300 EXC TPI enduro models enjoy a wide power band, fuel consumption that can compete with four-strokes, and comply with modern emission caps
KTM's long standing off-road tradition continues with the new generation of 2018 EXC TPI enduro two-strokes
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KTM's long standing off-road tradition continues with the new generation of 2018 EXC TPI enduro two-strokes

As promised back in March, KTM has unveiled a fuel injected two-stroke engine that's expected to give four-strokes a good run for their money. Available in 250 and 300 cc capacities, the new single-cylinder motor promises the best of both worlds, all the while satisfying the strictest emission standards.

Austrian motorcycle manufacturer KTM made its name in the heyday of two-stroke off-road competition machines and it seems poised to honor this legacy, even if that means swimming against the stream. The company characterizes its new engine as a paradigm shift, although it didn't really need to reinvent the wheel in the process of designing oil-burning strokers that can easily fit into the environmentally friendly mold administered by modern legislation.

In fact, the new 250 and 300 EXC TPI enduro bikes that showcase the engine are based heavily on last year's two-stroke EXC range, with only the main parts that handle the breathing and fueling aspects of the motor changed.

The rear view of KTM's EXC TPI fuel injected two-stroke engine
The rear view of KTM's EXC TPI fuel injected two-stroke engine

Replacing the Mikuni carburetor of the basic EXC models and introducing the patented Transfer Port Injection (TPI) system is the key to KTM's new tech. Th TPI feeds the cylinder via two downdraft injectors that spray atomized fuel in the transfer ports at the back of the cylinder, mixing it with the flow of air and oil that is supplied through a throttle body designed by Italian specialists Dell' Orto.

The whole system is regulated by a precise new engine management system (EMS) developed by Synerject. With the help of a series of electronic sensors, the EMS defines the exact amount of fuel to be sprayed into the ports at any given moment, while another injector in the throttle body mixes tiny amounts of oil with the incoming airflow to ensure the lubrication of the engine's moving parts.

According to KTM, this injection system does away with all the typical blemishes that condemned two-strokes as environmental hazards in the past. The single-cylinder EXC TPI engine promises wide power delivery, low fuel and oil consumption, easy cold starts and no need for adjustments for altitude.

The new two stroke engine of the KTM 250 and 300 EXC TPI is equipped with both a kickstarter and an electric starter concealed below the throttle body
The new two stroke engine of the KTM 250 and 300 EXC TPI is equipped with both a kickstarter and an electric starter concealed below the throttle body

The oil is contained in a small reservoir under the central frame beam. KTM says the new engine runs on an 80:1 fuel-to-oil ratio, whereas until now the typical two-strokes would require a ratio around 40:1 on average. In practical terms, the oil container's 0.7 l (0.2 gal) are good for at least five 9-liter (2.4 gal) tanks of fuel, thus reducing the amount of smoke coming out of the exhaust by as much as 50 percent over pre-mix systems.

For 2018 KTM will produce two EXC TPI variants, one at 249 and another at 293.2 cc, differing only in cylinder bore. Weighing in at 103 kg (227 lb) in full trim without fuel, their engine performance figures are yet to be disclosed.

In every other aspect, the new enduros are identical to the basic 2017 EXC models. They are built around KTM's signature 25CrMo4 (chromium-molybdenum) steel alloy double cradle frame and lightweight aluminum sub-frame, with WP Xplor adjustable suspension that includes inverted 48 mm forks and a PDS rear shock, as well as Brembo brakes. The standard equipment list also includes a six-speed transmission paired with KTM's DDS clutch, in which a damped diaphragm steel basket setup is used instead of the typical coil springs.

Only the 2018 graphics, or a careful look at the fueling system behind the cylinder will reveal that this is a next-gen fuel injected KTM EXC TPI
Only the 2018 graphics, or a careful look at the fueling system behind the cylinder will reveal that this is a next-gen fuel injected KTM EXC TPI

The two new enduros will start shipping in June. No pricing details have been released, but reportedly both EXC TPI models are expected to be in the same ballpark as their four-stroke counterparts.

For KTM this shift seems to represent an important investment that relates directly to a similar trend in the enduro racing world. Two of its star riders – three times World Enduro champion Christophe Nambotin and Jonny Walker in Extreme Enduro – are now racing two-strokes, and are both expected to switch to the new fuel-injected models for next year.

Both the 250 and 300 EXC TPI are Euro 4 compliant, proving that all it took was the application of simple, well established tech to bring two-strokes up to date – and, most importantly, the will to move in this direction. It will be very interesting to see the reaction of other manufacturers, as well as whether KTM rolls out two-stroke-powered models in other market segments.

Source: KTM

6 comments
VincentWolf
It's already obsolete. Any serious electric bike could eat it alive corner to corner.
guzmanchinky
Noise noise noise. Get rid of two strokes, and then when that company in another article here on newatlas who is inventing a battery that charges in 5 minutes perfects it then get rid of gas burning bikes altogether. The biggest problem we face as off road enthusiasts is closure of trails and riding areas. And the number one reason why people want those areas closed is... NOISE!
Future3000
I agree VincentWolf. Electric Motorcycles are the future. But I asked me why KTM choose Oil and Lubricant at 2 stroke engine. It's only to build a cheap old 2 stroke technology I guess! We developed different 2 stroke engines: opposite piston, 1, 2 and 3 parallel cylinder, gasoline, natural gas and diesel driven. All were planned for new exhaust laws (SULEV) by using carbon compound pistons and liners. No lubricant and no cooling system needed. This KTM 2 stroke engine will never reach euro 4 or 5.
DonaldWalklett
I disagree with the noise thing , modern motorcycles are quiet as standard , when the original silencers are replaced or modified then they become noisy . For me this is a step in the right direction , lower emissions and two stroke power delivery , can't wait to test one .
Giolli Joker
@VincentWolf Simply no. You can't (yet) pack enough power and batteries to compete with a 2 stroke engine like these, without ending up with something much heavier and way more cumbersome. Battery technology is getting increasingly more interesting in automotive applications, but on motorcycle, especially lean and mean off road bikes, it will take a while before they will catch up the gap. KTM however has already a foot in the electric motorcycle market.
amazed W1
Why not add a turbocharger and dump crankcase induction, to do away with oil in the fuel but get the scavenging effect? It would also reduce noise and emission of pollutants too. Don't ultra big diesels on ships do this already?