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Just spent quite a lot of time reading through the whole thread. Will definitely be watching it.

Proper impressed here.
 

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That's awesome! He's one hell of a fabricator. Having access to that cnc has got to be nice too.

I'm not sure he'll be making much more power though. He's basically forcing twice the air/fuel into half the displacement. All other things equal, that'd be a wash. Since most of our little mc engines achieve >100 volumetric efficient through ram effects, he might even make a little less power. It might rev higher and hold the powerband better though. Interesting experiment no matter what.
 

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I'm not sure he'll be making much more power though. He's basically forcing twice the air/fuel into half the displacement. All other things equal, that'd be a wash. Since most of our little mc engines achieve >100 volumetric efficient through ram effects, he might even make a little less power. It might rev higher and hold the powerband better though. Interesting experiment no matter what.
Check out this Ducati, dude did the same thing & got 15 more hp
http://thekneeslider.com/archives/2009/01/12/ducati-v-one-twin-to-supercharged-single-conversion/
 

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That's awesome! He's one hell of a fabricator. Having access to that cnc has got to be nice too.

I'm not sure he'll be making much more power though. He's basically forcing twice the air/fuel into half the displacement. All other things equal, that'd be a wash. Since most of our little mc engines achieve >100 volumetric efficient through ram effects, he might even make a little less power. It might rev higher and hold the powerband better though. Interesting experiment no matter what.
There is no ram air affect on a GS500 in fact there isn't on most bikes just some of the more modern sport bikes. None of the current Triumphs other then the Daytona has ram air. Even with the RAM air on the Daytona it never achieves positive air box pressure. As for the GS500 you clearly haven't ridden one. They start out with about the same performance as a Ninja 250 so the bike has acres of room to grow.
 

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I've never been on a GS500. I also didn't know we never get positive with our ram intake? Even up at high speeds? Good point though, the GS500 wouldn't have that advantage.

Nonetheless, conceptually, there shouldn't be much of an improvement, correct? In the end, the power is directly related to the amount of air/fuel, and how well it can be burned. The non-real-world physics says it'd be the same power. Would an intake/exhaust and good tune/timing result in nearly equal power gains on a normally aspirated 500?

I don't know if there's any way to do direct comparisons, since the two scenarios are quite different. Is there an innate advantage to having a pressurized system, from a fuel burning standpoint in the chamber? It'd be interesting if we could see the maximum power ever achieved by a 500 versus this style forced 250.

I know, a lot of questions. :laugh:
 

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Absolutely, and he's doing it with a lot of style at that. Those are great looking pieces for being first runs.

I'm personally just kinda curious about the performance. :whistle:

BTW, from what I know, you can achieve >%100 volumetric efficiency with either a well designed intake/port tuning and cam or a ram intake (or both). I hear the great engine builders in the buildoffs can get up to like %140 with normally aspirated engines on the dyno (no ram). Hence the reason Yamaha started doing the variable trumpets. I don't think that would show up with the pressure sensors. I don't really know about ram effects though. I've not done that much tuning with modern normally aspirated engines, and never with realistic airflow.
 

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if you're intersted in the guy's theory, go to his blog, crecca.wordpress.com . he put some cycles up and some calculations.
 

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This shit is AWESOME.

Also, as a person with access to a CNC shop, I can't believe the thought never occurred to me to make my own rearsets, haha. I wish I was doing something like this for me senior project... it'd be way more fun than the crap in the medical field I'm currently doing. :p
 

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Yes, you are absolutely correct. I got hung up on the ram air being the key part. Yes nearly all motors achieve a greater dynamic compression ratio then the calculated cylinder volume compression ratio. This has as much to do with air having a mass and thus maintaining momentum despite the cylinder reaching the bottom of the stroke as it does with the intake efficiency.

That said as you said on a really well designed motor even RAM air you're never going to double the efficiency. With this compressor setup for every combustion stroke of the main cylinder it's going to receive twice the cylinder volume of air from the second cylinder. This is why he's using the reed valves on the compressor side and removing the valves. By doing that the compressor side compresses on every stroke where as a 4 stroke motor as the other cylinder still is only compresses every other stroke. Add that into the fact that the efficiency of the GS500 motor is about that of a riding lawnmower and you can why I believe that despite losing a cylinder and dropping to a 250 I bet he achieve as much as 50% more power out of that one cylinder then the motor was achieving stock with both cylinders.
 

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Huh, ok. I guess cars probably have more to do with intake ports because the intake tract is usually more obscured. Motorcycles have a pretty clear line from trumpet to cylinder.

I'm not sure on your math though. If that 500 is achieving say even %110, then creating an arbitrary unit of power, it could achieve 550 superponies (10 superponies is aproximately 1 horsepower). The blown 250 at %200 would achieve 500 superponies, which is less than 550.

I get your point though, and it sounds like the 500 engine has a real conservative cam and loose compresssion, so it probably isn't even seeing %100. That would definitely put the blown version ahead, since those are prime conditions for forced induction.

We also aren't giving consideration to the whole powerband. Even if there isn't much extra horsepower, he'd probably gain some more torque down low, if what I know about cars carries over. A much more appealing powerband overall.

Now I'll go see what he has to say :rofl2:
 
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