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Discussion in 'Parallel Universe' started by FinTec, Dec 12, 2014.
He is out riding the beast. I think you will like what he did.
Sorry all for the lack of updates. Actually have a LOT of new pictures and just finished a major part of the project. Just need to find the time to sit down and go through it all and make presentable. I tell you, it is a lot of work to update a thread like this! I do enjoy it, and to have a "history" of the build is fantastic, but the amount of work it takes is more than you think. All the respect to those who have done great build thread here at ADV.
So coming up, the air box and intake that really makes MechanicO who he is.......and the fuel system that nearly killed him.....
He he he he....... Ya gonna have people knocking on ya front door Fin.....
It is a lot of work to document builds or rides well. So thanks.
Fin, this thread is absolutely incredible! I just binge read through the whole thing, and I'l dying for more! Thanks for doing this, I love to watch from the sidelines!
I also started and finished in one sitting. I really enjoy people who are just so badass at something I have no concept of. I did pick up a few tips to try on minor mods. Thanks for taking the time to post this and I can't wait to see the final reveal!
Jaw's on the floor at this. Completely and utterly gobsmacked. Talked about a craftsman at work.
Just make sure you get more than 704 miles out of it, @Fin333!
I'm going through withdrawals. It's my own fault for binge reading. Maybe I should buy a block of aluminum and watch it in hopes it magically turns into something cool.
OK, time to get this thread really moving...
Lets talk about the intake of the F800GS and where it makes its power. Currently the F800GS is rated at 85hp at 8500 rpm and 61 ft-lbs of torque at 5750 rpm. Overall great numbers and a great motor. Built by Rotax who, in my opinion, know motors as they build them for airplanes and those cannot fall out of the sky.
However, the issue is when you start adding "hop-up" parts like free flowing air cleaner, larger diameter exhaust, and other basic bolt-on items you will gain some HP but it will end up further down the rpm band and you will also (probably) shift the entire power band to the right (definition: when I say right or left, I am referring to a dyno chart where you see where the HP/Torque in relative to the RPM: less RPM is to the left, more RPM to the right). On bikes like these, that does NOT help us out all all. We want max power as early as we can get it. And not just power, but the torque as early as we can get it.
Torque is what I strive for in my engine designs. Torque is:
Rear wheel spinning
Smile on your face when you twist the throttle
Anything and everything that is fun on a motorcycle
HP is great too, but it is usually focused on too much. Think about it, yea, we have 85hp but at 8500rpm. Who hell goes to 8500 rpm!
HP ratings sell bikes, torque makes them worth riding.
Do yourself a favor, next time you go for a ride, both off and on-road, take note of your tach. If you are like me, you spend a HUGE amount of your day below 6000rpm. And even then above 6000rpm once in a rare while to maybe pass a car. My bike with its current gearing will do 68mph at 5000 rpm. So in my opinion, I want all the torque I can get under 6000 rpm. In otherwords, I want to shift the power curve to the left as much as possible. I'll take a hit on total HP to achieve this, but that is OK with me. And that is what we are going to build next, MechanicO the torque machine!
So how do we do this with what we have? You can change major parts of an engine to do this like the cams, or compression ratio (higher), but that is VERY intrusive and honestly, the base engine is fantastic and I do not want to go that far with this build. However, we can use something called "resonance tuning". Some also call this Pulse Tuning or using the Helmholtz theory. This is a concept where you adjust the length is the intake track to put the power band where you want it. There is a ton of information and articles on this on the web such as:
The VERY basic concept is this: air is traveling down the runner at a certain velocity. All of a sudden the intake valve slams shut. This creates a pulse or a sonic wave that then travels back up the intake tube. When it exits out the end of the open tube it expands, or pops. Part of this expansion travels back down the intake track towards the intake valve. But the intake valve is still closed because this wave happens at the speed of sound and the motor is still in its compression/combustion phase under the intake valve. So this wave/pulse bounces back up the track to once again expand at the end and come back down again. Each one of these round trips is called a "wave" and with each wave pass it gets a little weaker. Eventually the pulse comes down the intake track and low and behold, the intake valve is open. Now this wave/pulse acts a boost of a sort and the volumetric efficiency of the motor at the point goes up significantly. Think of it as free built in super charge affect. Issue is it only happens at a relatively narrow rpm range. But you can control where that narrow range happens with resonance tuning. And you do this by varying the length of your intake track.
Also, you want to try and use the "soonest" wave you can as they get weaker as go up in count. For example, NASCAR motors are designed around using the 3rd wave.
So do we need to lengthen or shorten the intake track to get torque sooner? There are several websites that have online calculators for this. But my favorite and easiest to use and just do some quick analysis with is this one:
You do need to know a few data items on your motor (like cam duration and intake diameter) but after that you can plug away and see what you get.
So I started with the stock motor to see where that put us at first. I measured the intake track at around 16.25". This is essentially from the back of the intake valve to inlets of the plastic inlet horns in the air box. This picture roughly shows the the stock plastic intake horns and the next pic is a side shot of the side of the motor with the horns in the throttle bodies showing the entire side profile of the intake track:
From some other research (and help from this forum) we also have a cam duration of 182 degrees. I used the diameter of the throttle bodies as the base for intake diameter for now at 49mm (1.92in).
So using the online tool from the website above I get these results:
The stock intake track of 16.25" gets a 3rd wave at 7200rpm (below)
Now, if I add say, 10" to the stock intake track I get a 3rd wave at 4500 rpm
WAY lower on the rpm range than the stock runner length of 16.25". Torque sooner, the goal.
The conclusion is longer intake tracks add power sooner, short intake tracks add more power, but later in the rpm's.
So bottom line is I need to lengthen the intake track of this motor from stock. And my goal is to try and make it 10" longer than stock. But there lies the trick how to make it all fit in this bikes frame work.
However, the first step is to prove adding 10" will in fact have the gains I am shooting for. Dyno time.
Getting ready for a dyno run on any vehicle take a lot of time. It costs you money to be there so you want to do all your prepping and set-ups before your dyno day. Be organized and ready. A dyno shop loves nothing better that to charge you for time as they sit there and watch you find an intake leak or figure out why the vehicle is not running right. Organized and efficient on dyno day is the rule.
So along those lines I wanted to test my 10" extensions before the big day and make sure they fit and the bike ran. I first made these extension from some aluminum tubing that was perfect in diameter.
Then I duct taped them to the ends of the plastic intake tubes and using some small tubing extended the idle air control valve hose so it would idle. Looked like this and it started and ran
So with that concluded I scheduled my dyno run.
I used Boulder Motor Sports in Boulder, CO. Let me just state this, these guys are top notch and pros. The tend to favor the Ducatis but they welcome all motorcycles. Brian (the owner) was VERY patient with my 20 questions even before the visit. When I arrived, they where ready for me and Brian gave me two hours of his full attention. And I mean that, he never took a call, never looked at his phone, never left the dyno room for the entire time. The shop looked like you could give birth on the floor or counters and be hospital clean. These guys are the real deal. I highly recommend them.
So here is a shot of the shop from inside the fully enclosed dyno room
So we wheel in MechanicO and strap him down and get him warmed up. I was also logging along side Brian with my laptop and GS911 unit to get as much data as possible.
So I had four configurations I wanted to get dyno readings for:
Fully stock: not changes at all (stock air box, filter, exhaust, no enrichment items, etc)
No Nothing: entire airbox removed, no intake horns, just straight throttle bodies
Intake Tubes Only: no air box but the intake tubes installed into throttle bodies
10" Extension: same as above but with my 10" aluminum tube extensions on the stock intake tubes
Another nice touch for the dyno operator is take your list of what you want and print it out in big-ass fonts and then tape it on the wall near him. Then he knows the schedule and what you want and what he needs to do. Again, be efficient.
In this shot you can see we have already done the first three and are now testing the 10" extensions. Yea, pretty hack with all the duck tape, but it only needs to last about 20 seconds
One note: it is always a thrill to be in a small room, standing next to your bike as it is essentially screaming at the top of its lungs right up to it's rev limit. Wakes you up big time. And don't forget to bring your ear protection!
So after 2 hours, I get the results.......
Fin, couple of questions!
Does the shape of the extension tubing make any difference?
You´re now testing with straight tubes, but does a curved tube change the performance(thinking it wont look very pretty with tubes shooting out of the frame)?
Can I do this mod together with different headers or do I need to do more mods to make it work?
Incredible project Fin. Thanks so much for taking the time and sharing with us mere mortals.
WTH, you got me hanging on my seat for the report. How much does diameter play into it?
Ha ha ha ha ha.........
How do you keep dozens of arseholes in suspense?