Wednesday, July 25, 2018

Biodiesel Sportster Land Speed Racer - 96.8 MPH at the Loring Timing Association 2018

On July 11th, my friend Dan and I embarked on a 650 mile road trip to the Loring Timing Association's "Maine Event" in Limestone, Maine.


We loaded my beat-up, 220k mile truck, hitched the flat trailer with diesel Sportster, and began our journey with the traditional 2 hours of gridlocked NYC traffic.


After putting some mileage between us and the city, we stopped at the Red Rooster in Brewster, NY for burgers and fries. The food was delicious, but unfortunately this was where we discovered our first mechanical malady of the trip. 

After getting out of the truck, I immediately smelled gear oil, and noticed spray marks on the trailer. Upon closer inspection, I discovered that the rear differential was puking oil from the cover gasket and front seal. The fluids had been topped off earlier that week, so I chalked it up to overfilling, wiped it clean, and continued our drive. 




We arrived at our first destination around midnight, where some friends outside of Boston graciously let us crash in their guest room. By 7AM the next morning, we were back on the road, and digging in to breakfast at a Cracker Barrel.


I inspected the rear differential after breakfast, and it appeared that the leak had resolved itself. However, by Portland, Maine, the leak was worse than ever. Driving in the cool weather the previous night had only lessened the symptoms.

At a rest stop, I called my mechanic to diagnose the problem. He recommended that I inspect the axle vent, so we parked behind an Auto Parts store in Augusta to repair the issue.





Removing the vent released audible pressure, and the vent itself was fully plugged with rust. The store did not carry replacements or plumbing fittings that fit the thread, so I disassembled the vent, cleaned, and reinstalled it.



Once again back on the road, we made our way up I95 to Bangor, where we stopped for lunch at the truly excellent "Whoopie Pie Cafe". They have good lunch options in addition to dozens of varieties of Whoopie Pies, and I highly recommend the visit.



Leaving Bangor behind, we continued north to our destination in Presque Isle.
 





Friday dawned cool and partly cloudy, with a good tail wind and low humidity. Absolutely perfect conditions for racing, so we left the hotel early and rushed to the track. The bike breezed through tech inspection, and we attended the morning drivers meeting, set up our site, and wandered the pits admiring the other high-speed machinery on display.









































After prepping the bike, we rolled over to the staging lane and joined the queue. The first run went extremely well, and I beat the previous top speed by 7 mph. However, while riding down the return road, the engine started spitting oil out of the crankcase breather and coating the left side of the bike.

The engine was originally equipped with a system that directed crankcase gases into the intake, drawn by the vacuum. This system has to be disabled when an engine is supercharged, because there is now a positive pressure in the intake. I had installed a breather filter, but now discovered that this was insufficient at high power and rpm.

We quickly drove to an auto parts store in Caribou, and purchased 3/8in fuel line and zip ties. These supplies, combined with a used Gatorade bottle, make a halfway-decent crankcase catch-can. Tech inspection cleared the modification, and we rolled back out to the track.










During the next two passes, the Sportster performed flawlessly and achieved a maximum speed of 96.8mph! The drivetrain was geared to 102mph at a redline of 4200rpm, but the engine peaked at 3800rpm and couldn't go any faster.

The supercharger produced 7 pounds of boost and 150F at the intake, and the high-temperature exhaust coating burned off the headers, indicating an Exhaust Gas Temperature (EGT) well over 1000F. Typically, the EGT for diesel engines is limited to 1250F to prevent thermal damage, so the engine was performing very near its failure limit.

After the third run, we were confident that the bike was at maximum power, and any further runs would only risk causing engine damage. We packed everything up, loaded the truck, and watched other teams race the course before driving back to Presque Isle for dinner.











Having finished with the bike on Friday, we decided to spend Saturday as tourists. We returned to the track to watch more racing, visited the historical society for the airbase, and drove to the former ammo dump on the far north side of the facility, now converted into a wildlife sanctuary.














On Sunday morning, we began our journey home with a few obligatory tourist side-trips along the way, such as Stephen King's house in Bangor, and an excellent roadside seafood shack for lobster rolls. By dinner, we had gotten back to the outskirts of Boston, where we visited some other friends before bedding down for the night, and continuing home the next morning.













Despite falling slightly short of my goal of 100mph, this year's race was still a complete success. We set two new records for a 1000cc biodiesel motorcycle at 96.8mph, suffered no major mechanical issues, visited beautiful destinations, and found time to enjoy a thoroughly unique road trip. The bike survived the ordeal, and lives to be modified and raced another day. I'll treasure the memories for a lifetime, and wouldn't trade any of it for that extra 3.2 mph....no matter how much that number will annoy me!

Monday, June 4, 2018

KZ400 Diesel - Rebuilding A Wrecked Engine

During the construction of my KZ400 diesel motorcycle, many people had asked about the reliability and longevity of the Yanmar L70 clone engine. I had supercharged it, boosted the horsepower and max RPM, and taken it to the absolute limit numerous times.

Now, I have an answer for that. After 7 years of development, as well as:

-4 certified land speed records
-2500 miles of riding.
-Disabled speed governor
-Supercharged to 5psi
-Upgraded valve springs

...the crankcase split in half directly below the cylinder, nearly blowing the top end clear off...

 After careful examination, I was confident that the guts of the engine were fine, and the damage was limited to the crankcase. So, rather than simply swap engines, I registered an account with AliExpress and purchased a replacement crankcase to transplant as much as possible out of the blown motor.
 

After working through my backlog of projects, I put the bike back on the bench. The first step was to disassemble the drivetrain, clean the frame, and improve some of the mounting hardware and wiring.




I finished stripping the engine, and was able to examine the inner assembly for the first time. Overall, the components were in excellent condition, the only major issues being excessive carbon buildup in the combustion chamber, and wear on the output-side plain bearing.

I also inspected the camshaft, and found no evidence that the stronger valve springs had caused any damage to the lobes.


Next, I refurbished the original engine internals, deburred the new crankcase, and installed everything with fresh bearings, gaskets, and seals.



Finally, I brewed up some caffeine and locked myself in the garage for a marathon reassembly session!





Saturday, December 23, 2017

Biodiesel Sportster Land Speed Racer - Supercharger!

It's been three months since the last update...but you didn't think I was sitting around, did you? I've been welding, fabricating, and testing, all in the pursuit of straight-line speed. Here, just in time for Christmas, is the latest incarnation of the Biodiesel Sportster!

At Loring this past September, the Sportster maxed out at 86.5mph in the final pass. I'm confidant that we finally ironed out all the bugs, and any further improvements need to focus on the limitations of the stock naturally-aspirated engine. The engine is a 836cc v-twin by Kipor, rated for 20hp at 3600 rpm.

When dealing with a diesel engine, most upgrades for horsepower are pointless unless you correspondingly increase the air flow, either by super- or turbocharging. Fuel can only combust and produce horsepower in the presence of enough air. Once the intake air is used up, any extra fuel will just become smoke.

At first, I wasn't sure which method to use. There are numerous small turbo kits available, most with questionable quality and reliability. Regardless, I wasn't confidant that the engine's oil pump had spare capacity to feed a turbo as well as the crank. Alternatively, a supercharger builds lower boost pressure and consumes a bit more horsepower with the pulley system, but ultimately runs cooler and has a self-contained lubrication system. Eventually, I decided to use an AMR500 supercharger from a Japanese kei car.



I fabricated two brackets to suspend the supercharger on the left side of the bike, directly in front of the transmission primary. Then, I re-machined a pair of 4-inch V-belt pulleys from the hardware store to drive it.



The supercharger is rated at 500cc per 1 revolution (1000cc per 2 revs), and the engine displaces 836cc per 2 revolutions. Therefore, by using a 1:1 pulley ratio, the supercharger is providing 19.6% more air to the engine. Ignoring pumping and friction losses, this will allow the engine to produce about 4 more horsepower. In practice, it would probably be closer to 2.5-3hp. I will likely increase this later, but this is enough for testing purposes.

Next was the intake plenum, which I fabricated from 2inch steel piping.







The placement of the supercharge interfered with the original exhaust, so I welded a set of scrambler-style high pipes.




 

Finally, I had to increase the fueling to take advantage of the extra air. Information is limited for this engine, so I decided to open the governor housing to document the design and look for improvements. It's difficult to see through the small access hole, but after a few hours of tinkering, I drew this diagram:



- Lever "A" is the main pivot in the assembly. The governor pushes against it on the upper left, and it adjusts fuel on the bottom right.

- The throttle cable is attached to lever "B". Both pivot on the same shaft, and are connected by springs and direct contact as they rotate.

- The main spring to fight against the governor is attached to lever "B". There is a tiny spring attached between "A"and "B" that is too weak to have a anything to do with governing. I think it's just there to keep things held in place and prevent slapping.

- I noticed during examination that, when lever "B" is held at full throttle, lever "A" isn't held tight against it. The governor can push it back a bit before it comes to a rest against lever "B". This basically disables the upper 10-15% of throttle position at the injection pump, because there is nothing to hold it there against the governor.

- Lever "B" has a threaded hole that is missing some type of set screw. When at full throttle, without that set screw, the only spring fighting the governor for the top 15% is the tiny spring. Once lever "A" makes contact with lever "B", the main spring takes over.

To increase pump position and horsepower, I needed to purchase or fabricate a new set screw, then adjust it until there is no slop between the levers. Factory replacements are impossible to find, so I decided to make one. Unfortunately, it is a very unusual, and unavailable, thread (M14x1.0), so I had to special order threaded rod from China. Once it finally arrived (2.5 weeks of shipping!!), I made the screw.



Wednesday, September 13, 2017

Biodiesel Sportster Land Speed Racer - Loring Timing Association Sunday Pass (Video Post)



Onboard footage from one of the passes I made on Sunday. The weather was perfect and winds were favorable, and the bike managed an 86.5 mph pass.