Sunday, August 28, 2011

Exhaust Questions

Since I started to build supermonos I have been curious as to the science of 4-stroke exhaust tuning, especially now since compromises can be covered up with idealized jetting.  However, in taking a look at the EX650 exhaust, it is so unlike anything I have seen before that Kawasaki either finally figured out how to properly create an exhaust, a "lightbulb moment" after 40 years of racing, or, more likely, it is a packaging or aesthetic compromise.  Basically, the whole system appears far too short in length.  The primary headers snake around a bit in order to find some length, and the old Leo Vince slip on system does a full 360 with the tailpipe in order to get some length...
Take a close look at this pic and you can see the tailpipe turning full circle!

In doing the reasearch, I stumbled across this website that is based on the famous tuner A. Graham Bell.  If you go there, you can plug in information about the characteristics of your engine (single to multi) which will then spit out the ideal header length and diameter; proper collector length; and the length of the tailpipe PRIOR to fitting a muffler or slip on.  I punched in some scnearios and proofed it against Bell's book, and it did check out.
So, how did the EX650 do?  After getting the BBDC and ATDC figures, and putting the idealized hp peak at the 9000 rpm mark here is what is suggested ( based on 1 of the 2 cylinders):

Header length:  27"
Header ID:  1.5"
Collector Length: 6"
Tailpipe Length: 18"
Tailpipe ID: 2"

Sounds pretty typical.  I went out the to the EX and this is what I measured (based on the Muzzy exhaust system I currently have mounted:

Header length:  26.75"  CLOSE!
Header ID:  1.5" (note this is the OD, but CLOSE again!)
Collector Lenght:  4" (a bit short)
Tailpipe ID:  2" (again, this is OD, but a negligable difference)
Tailpipe Length:  2" (YIKES that is short) -- that is the length of the tailpipe before it begins to expand into the megaphone exhaust.

As you can see, the exhaust is quite stubby; according to the tuning guru, I need an additional 16" of tailpipe, over 1', before the muffler should even be added.  Makes for some interesting concepts for experimenting.  Would it make a difference?  Again, with proper tuning, it should.  A smaller tri-oval muffler could be tucked away, mounted close behind the RHS peg for ground clearance.  Perhaps a project for the winter?  We'll see.

Friday, August 26, 2011

Round 4 Results

Another decent weekend -- sorry no vids as the batteries died in the camera.  AJ was out taking pics, so there should be his usual good stuff to come shortly.


Practice went well; interstingly, I went faster Saturday morning than I did all weekend (by fractions of seconds).  Happily, I got into the 1:09s on the mono -- a 1:09.288 -- actually the 12-fastest bike out in that session -- not bad.  It was a goal to get into the single digit times and I'm happy I did.  Another goal I set for myself was to get into the 1:05 bracket on the 650 -- my onboard timer indicated a 1:05.988, but mylaps claims it was actually a 1:06.083.... next weekend, then.  Most importantly, I could string together a series of 1:06s so that lowered my overall race distance time is much faster.

Race 1:  Cdn Thunder GP:  15 laps

An eventful race:  in 4th on lap 3, and 4th place rider goes down in turn 3.  His bike started to spin, and I actually glanced off the front windscreen taking evasive action.  Missed the rider and the bike itself, but had to take to the grass.  Luckily the race was red-flagged, rider was OK.  On the restart, got a great start and was in 3rd when Wilson went down behind me try to pass (he got a bad start).  Left me alone in 3rd... part way through the remaining laps, my clutch cover guard fell off and smacked me in the leg -- I spent a few laps trying to figure out what happened and lost some time.  However when I realized the issue wasn't major, I put my head down and consolidated my podium with a 10 second gap to 4th.  Happy result!

Race 2:  ULGP #1:  12 laps

Another uneventful race, except for the crazy wind.  Blowing so hard that my lap times were negatively affected -- a huge headwind down the front straight, but I still beat the other experts, although the bloody rs250 got me again.  1st expert however.

Race 3:  ULGP #2:  8 laps

Shortened due to horrible weather -- gale force winds and intermittent rain, no fun on slicks.  My main competition for the title parked his slick-shod bike, so I went out, tiptoed around to 2nd place, and therefore locked up the ULGP expert championship with 1 round to spare.  Mission accomplished.  Hopefully the Husky is a match for the 250 two-strokes next year!

Race 4:  Cdn Thunder #2:  10 laps

An awesome race against Jason.  I feel really comfortable racing against him in close quarters -- ran 1:06s nearly the entire race, and actually turned faster lap times, but he just beat me for 4th by 0.230 of a second.  Woulda loved to get that one on video -- will remember to check the batteries next round!

Race 5:  Cdn Thunder #3:  10 laps

A poor race for me overall -- went wide around another rider, couldn't make the pass stick, and Jason got by both of us on the inside.  Spent the remainder of the race trying to get by, but eventually gave up, lagged back, let the top novice racer by, and then tried to turn some quick laps in the end.  Not happy with myself, but I need to remember that a stupid risky pass is not worth a $2 trophy.

Other news:

Here is a pic of the paintwork as it continues on the Husky:
Also, I am now convinced that the total lack of aerodymics is holding me back in a closly-matched class such as Canadian Thunder. Gary from sold me a set of used bodywork, properly made by catalyst for the ex, and mimics the 636 fairing (even uses the 636 screen). Got the upper, lower, screen, and stay. Won't be here in time for the final round, but can spend the off-season mounting it and painting it to match.

The stainless J-bends came in and I dropped them off at Cycleboys -- just need the 2-1 piece and Brent can start fabricating.

Monday, August 15, 2011

waiting game begins

The "Mitovarna" is off to cycleboyz to get the header fabricated.  Doing some digging to get some of the stainless tubing -- a 1.38" j-bend in stainless is pretty rare, although I did find a 2-1 collector on ebay.  Muzzys actually sells some tubing, so I might get in touch with them... although cycleboyz might also get what they need from their source.  It gonna be weird to not have the bike to look at for awhile.  Oh well, timing is OK as I'm back to work soon, and there are 2 more races to go, plus a mancation in the works, which will keep me busy.
On another note, tail section is painted with one coat of clear, so I'm waiting on getting the stripes (NRG signs, who did the Luckystroke logo) to have those done for me.  Will apply to the tail and part of the tank, and then another coat of clear overtop.  They are also coming up with some retro-styled numbers as well, in an odd size to fit the round plates I have painted on.
Race this weekend -- round 4.  Will post results as soon as I can.  Wish me luck!

Friday, August 12, 2011

exhaust, more paint, and a wee trick part

Worked on getting the exhaust mounted up.  I just need to put the muffler and tailpipe in situ, and then drop the whole shebang off at Cycleboyz so they can do the hard part -- fabricate the 2-1 header.  Exhaust is an M4 off of ebay, for an R1.  80 bucks! Score!

Rear muffler hanger is a steel strap mockup, to be replaced with something much nicer in alloy when the time comes.  Not bad for a full carbon muffler, and should be quieter considering the likely bark of the big single.

Tank now has 2 coats of clear.  Tank protector is an old 916 carbon jobbie I had laying around.  Not sure if it will stay, as it is 98% there in terms of "perfect" fitment, but it is designed for the larger, although similarly-shaped ducati tank.

Lower fairing.  One coat of clear over the latex blue, and then the number plate was painted with krylon.  Next chance I get I'll put the second coat of clear on...

I'd seen a few specials with these new motocross rear master cylinders -- with an integral rear reseviour, kinda looks pretty cool in my opinion.  The mounting bolts won't line up with stock roadbike mounts, but since I am custom making my rearsets and m/c brackets, this should be simple.  On another note, the rear lower mount requires an m8x1.25 rose joint.  Unavailable in farmer-ville here -- standard threads only.  However I took one I had lying around, I think from dad's old aircraft stock, drilled it out (originally 1/4 fine thread) and then tapped it for m8.  Sorted!

Monday, August 8, 2011

more pics

Homemade rear stand -- made with 2 rollerblade wheels, some scrap tubing, and my mig welder.

Rearsets -- a bit lighter with some 'oles in 'em!

Tank sticker on, need to wait for a better day weather-wise to lay on the second coat of clear.

Sunday, August 7, 2011

mito updates

Have spent some time over the break mounting up a few things.  First, the radiator, from a KTM450 quad.  A bit overkill, and a tad wide, but cheaper than custom, and it had the water inlet and outlets on the same side as the husky engine.
I was able to fabricate some rad mounts, and the engine mounts do double duty as radiator mounts as well... looks somewhat stock!
I was able to determine the position of the rad by securing it in the top mount, and then removing the tops of the forks and collapsing the sliders completely, ensuring I had "just enough" clearance under full braking.

I also got some spacers made up for the shock lower mount...

And made some rearset plates out of the alloy plate I got. There will be some more work done to the plates themselves, and different pegs and shifters will be utilized.

And because the weather is decent, and there is nothing else to do right now, I've done some paintwork.  Using a simple latex-based rattlecan from Canadian Tire, only because the "Danube Blue" apes the Gulf Oil blue of the Lemans cars of the early 70s, with of course a coat of clear overtop.  OK stuff to work with, and less toxic, but being water-based, I don't leave much time between finishing the color and adding the clear to seal it up.

Tank, with the first coat of clear.  Will add a Gulf decal, and then put on a second, thicker coat.