Horsepower/torque gains - KTM Duke 390 Forum
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post #1 of 25 Old 10-21-2016, 02:52 AM Thread Starter
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Horsepower/torque gains

As I value the collective knowledge of this forum, I would like to know what is the best route to achieve maximum horsepower gain or torque of the Duke 390? I don't care about smoothness or exhaust note, I'm talking power. Most if not all aftermarket pipes provide no real measurable horsepower gains for the money, and power commander/piggybacks do smooth out the leaness and jerkiness but also have only a small effect on horsepower for the money. I LOVE the little Duke but just want a bit more usable HP and ideally more torque. And yes I know I could have bought a 690, but at twice the price I just couldn't pull the trigger. I am willing to spend up to 2K on mods. Thanks for your time.
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post #2 of 25 Old 10-21-2016, 02:58 AM
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I had Chad Wells of Commonwealth Motorsport freshen mine up. Thinner head gasket,hotter KGK plug, air box mod w/K+N filter. Cam tensioner, intake runner clean up and ECU. Stock exhaust. Runs soooooo much better now! Check out the Dyno sheets from his builds. Smooth torque curve!
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post #3 of 25 Old 10-21-2016, 05:33 AM
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Realistically we can gain 8% to maybe 10% by spending in between 500USD -1000 USD ( Piggy back ECU , air filter and exhaust system ) Anything above you are looking at major transformations like the full engine kit from Chad Wells who seems to get and impressive 49 BHP onto the rear wheel : But for that you are looking at well over 2000 USD .
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post #4 of 25 Old 10-21-2016, 06:26 AM
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If you wanted to keep it all in warranty the Akrapovic exhaust and fuel mapping plus K&N officially develops 5bhp more.
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post #5 of 25 Old 10-21-2016, 07:15 AM
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I'm very satisfied with the gains realized from the PCV purchased from Chad at Commonwealth plus DNA filter and open lid, with just the stock exhaust. Well worth it - huge difference in power delivery. Peak power gains are not as significant as the boost through midrange where you will notice it the most.

I added the GPR Ghost for sound primarily but the significant weight savings cannot be ignored - less weight = more hp/lb.
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post #6 of 25 Old 10-21-2016, 07:32 AM
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Quote:
Originally Posted by CDN Duke View Post

I added the GPR Ghost for sound primarily but the significant weight savings cannot be ignored - less weight = more hp/lb.
Yes , that or a couple of pizza's , soda's and ice creams a week less for the rider
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post #7 of 25 Old 10-21-2016, 07:41 AM
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At the end the useful gain will be a more smooth torque line on low/mid ranger.
If I want a more powerfull bike with so much money I would exchange it in a bigger bike like MT-07/09, BMW F800R, MV Brutale...
IMHO make more sense in spend money but the power and torque of Duke is more than enough for now.
Guys it is just my opinion...
Luis
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post #8 of 25 Old 10-21-2016, 10:39 AM
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There is an almost philosophical dimension to these discussions. In some ways trying to extract a few more horsepower out of a small engine is a little like putting lipstick on a pig. The improvement is so incremental that it's hardly worth the bother. But for some there is a great deal of satisfaction in maximizing the potential of the machine, no matter that for the same money you could probably get a lot more performance out of another bike entirely.

I suppose I'm a "tweener" on this question. I don't mind spending a little time and money in small (and practical) improvements, but balk at big ticket items. A $500 exhaust system on a $5K bike makes little sense to me. But I certainly understand the desire to make it better, and everybody has their own calculus on cost vs. benefit. You can't put a dollar value on satisfaction, after all.

It was REALLY crazy over on the KLX250 forum. Some owners put a couple thousand dollars into a bored-out top end, exhaust systems, flat-slide carbs and all kinds of other things to get from 18 hp all the way up to 22-24. Yippee!
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post #9 of 25 Old 10-21-2016, 11:19 AM
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Originally Posted by Mikebet View Post
There is an almost philosophical dimension to these discussions. In some ways trying to extract a few more horsepower out of a small engine is a little like putting lipstick on a pig. The improvement is so incremental that it's hardly worth the bother. But for some there is a great deal of satisfaction in maximizing the potential of the machine, no matter that for the same money you could probably get a lot more performance out of another bike entirely.

I suppose I'm a "tweener" on this question. I don't mind spending a little time and money in small (and practical) improvements, but balk at big ticket items. A $500 exhaust system on a $5K bike makes little sense to me. But I certainly understand the desire to make it better, and everybody has their own calculus on cost vs. benefit. You can't put a dollar value on satisfaction, after all.

It was REALLY crazy over on the KLX250 forum. Some owners put a couple thousand dollars into a bored-out top end, exhaust systems, flat-slide carbs and all kinds of other things to get from 18 hp all the way up to 22-24. Yippee!
Agreed - there's only so much worth doing before switching up to a bigger bike. However, that said, I do think the PCV at US$360, a free flow filter of your choice for $50 and the airbox mod (free) are definitely worthwhile as they make such a significant difference. Less than $500 for huge gains.

The aforementioned would be requisite upgrades. Anything further is simply icing on the cake with only marginal gains to be had.
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post #10 of 25 Old 10-21-2016, 01:40 PM
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The preceding comments by LNICK and Mikebet - two guys with many years, many bikes, many miles/kms on their moto resumes - largely reflect my views on the question of hot-rodding the 390 engine for more power/torque.

Certainly, it is possible to extract more power from the motor: Many competition-minded RC owners do extensive (and expensive) modding to make their bikes faster; a Full-Monty engine makeover from Chad Wells, plus a carefully-mapped fuel controller, airbox mods and high performance air filter, along with one of the (few of many) aftermarket exhausts that can actually make fractionally more power than the stocker - all of this can reportedly raise output to the vicinity of 50 HP, along with increased torque. The total bill will set you back somewhere in the neighborhood of $3k. For 7-8 additional peak horsepower and better mid-ran ge torque. For some, this investment is entirely worth the cost. On the Duke side, there are a few who go for the full power upgrade, but most focus more on smoothing out power delivery, seeking to eliminate the low-range power roughness that many perceive as a product of the lean factory fuel mapping. Whatever the degree of power enhancement, the per-HP cost is high.

To my mind, the KTM engineers did an admirable job of designing a sub-400cc motor that delivers class-leading power. The bike is satisfyingly quick and fast for this category - If more power and speed is required, it is far more cost-effective to simply buy a bigger, faster bike. I have studiously kept my engine completely stock: motor, intake, air filter and exhaust are as delivered. It starts, idles, runs well throughout its power range, never stalls and overall is a very entertaining (and to date, entirely reliable) little powerplant. Does its job. Delivers a consistent 61-63 Miles per US gallon. It's not perfect - could be smoother, but it's a single - but I am happy. KTM's engineers did an excellent job, and I don't feel particularly compelled to second-guess them.

I like this little engine so much, in fact, that I want it to last a long time. Any mods I would do to the engine/intake/exhaust system would be in the interest of reducing thermal/dynamic stress and prolonging engine life. The engine is already mapped, for emissions purposes, with a borderline lean AFR: In addition, its per-liter power output is phenomenal, and would cost a fortune to replicate in an automobile. This is where a fuel controller may eventually come into the picture for me: I can see the logic in reducing the engine's thermal stress by enrichening the AFR. A little fatter mid-range torque curve as a by-product would not be unwelcome, but I am wary of significantly increasing the peak power output of an engine already so potent from the factory. My principal objective is cooler running.

One of the most entertaining aspects of owning a Duke is that - as capable as the bike already is as delivered - it is endlessly amenable to modifications of every sort. For me, modding the bike has been almost as much fun as riding it. I don't begrudge anyone who wants to modify the bike's engine/intake/exhaust system. I just don't feel the need, and I think seeking more power from this mill has a very questionable cost/benefit ratio: big bucks for small gains.

When you are a card-carrying old fart like me, you have the privilege of being annoyingly opinionated. As Mikebet puts it, I should not be taken seriously.

Cheers, Will

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