Sunday, January 31, 2010

Cleaning the carbs

So it's winter and it's been especially cold these last couple of weeks. We've hit -21 degrees Celcius before the wind so working outside on the cars is a little bit unrealistic. Burger is off designing our custom jackshaft which he will be posting CAD drawings of shortly. For the rest of us the next logical step would be to work on the snowmobile engine and get it running smoothly. Well a broken bolt lodged in one of the cylinders has put a stop to that, so all that's left to work on is the carbs.

Now, I honestly don't know when the last time the engine on the snowmobile ran or how long it sat since it was disassembled. The truth is that everything looked like it had been stashed in a barn for a few months. There were clumps of dirt, grass, and other strange and wonderful bits of nature covering the parts.

I had to set up shop inside the house since it's freezing outside and my garage is a mess. I took a shot of my setup in my basement so you could get a laugh.
I had the laptop on my desk with a "how-to" guide for cleaning these carbs. I have cleaned mikuni carbs before for my 6.5 hp honda engine on my racing kart, but I've never tackled one for a snowmobile, let alone 4.

The guide I used was here:
A big thanks goes out to the VMax4 forums for posting this article.

I first read through the carb cleaning article and it talked about resetting some tuning settings if your engine is having idling problems. Since we've never actually run our engine, I tried not to mess with these too much. I did notice that all of the fuel adjustment screws were set at a different level. All of which were significantly different than the recommended "reset" settings listed in the article. For now, I've left them as-is and if we have idle problems when we get the engine fired up, then we can play with them then.

For the most part, the entire experience was uneventful. I only had to remove the float bowl on the bottom of each carb to do the cleaning and I didn't have to mess with the reeds at all.

Cleaning a carb can be basically broken down into a few short steps:
  1. Remove the float bowl
  2. Remove and clean the pilot jet and fuel tunnel
  3. Remove and clean the fuel screw and fuel tunnel
  4. Remove and clean the main jet and fuel tunnel
  5. Remove the floats and check the status of the float pin
All of the main jets were quite clean and shouldn't give us any problems *fingers crossed*. 3 of the pilot jets were in pristine condition. One was clogged. I tried for a long time to open up the jet using a thin strand of brass wire. The guide said to use copper, but I figured it wouldn't matter. The wire entered the jet quite easily, but could not break through the dirt. I eventually went and got some copper wire from a recently disassembled computer power supply and noticed that it was a thinner wire. Of course, one poke with it and the dirt came right out. Let this be a lesson to all of you, always follow the guide ;)

The fuel screws were all set to different levels in each carb. The guide specifies that these should be reset to "1.25 turns past the point where it just gets snug". For these carbs, that was between 13 and 14 turns of the screw (from not being threaded at all). I returned the screws back to their previous depths which were anywhere from 14.5 turns to 17 turns. These values may cause problems for us, but thankfully this screw can be adjusted when the float bowl is on and the engine is running.
The last portion of cleaning came to the floats. These had some dried gas residue on them and needed to be scrubbed with a carb cleaner soaked paper towel. They came out much shinier and hopefully will not mix too much old gas with the new stuff we throw in. Here is where another tuning piece came in. As you can see in the picture, the floats are made up of 2 plastic floats and a metal "hangar". In the middle of the hangar is a small tab. This tab is what pushes down on the rubber needle in the carb. Now, the guide specified that the floats should be aligned with the machined base of the carb body. All of the floats were at significantly different angles to the machined body and I did adjust them to be closer. I'm not entirely sure what this does, but hopefully the adjustments I made will help the carbs flow smoother.

After cleaning and reassembling all the carbs, I cleaned all the rubber pieces that attach to them and installed them for visual effect. As far as I know, the carbs should be good to go as soon as we get the broken bolt out of our cylinder.

Monday, January 18, 2010

Saturday Firefly engine removal

Since there was a break in the weather, and temperatures got to nearly above freezing, it was decided to remove the engine from the Firefly (that's the super cool blue car). This would allow us to get a better look at the transmission bellhousing and hopefully help with measuring and figuring things out.

I had posted on the Team Swift forums a question on how to go about this. The reply was just to unplug everything, then unbolt the engine and manhandle it out, since its only about 100lbs. I suspected that the manual was a bit more explicit, but what the hell could go wrong? I'll let another team member explain the engine removal procedure:
  • Drain coolant and oil
  • disconnect everything (hoses, wires, etc.)
  • unbolt transmission from engine and frame
  • wiggle engine using hands and a jack under the oil pan
  • go to the pub for lunch and beer
  • wrap straps around the engine and around a 2 by 4
  • get 2 guys to stand on the engine bay's cross members and hold on to the 2 by 4
  • jack the engine up as the guys lift the wood beam
  • continue until engine comes out
  • hand off engine to a few more guys
  • put engine on ground

It's that simple!

Well, not quite! A few things, if you wanted to keep your engine nice, it is likely that you'd use a crane instead of the jack to better protect the oil pan. Also, if you can remove the pulleys, it would give you way way more clearance with the frame, and make this much easier. We cheated, since the engine is FUBARed we just forced it out with the jack.

Friday, January 15, 2010

What's the deal here... Summary, Overview, and Technical BS

DISCLAIMER:If you're reading this, a fair warning: This is a long-winded post about how we plan to get this all put together, if you're not interested in such details then please skip this entry.

Firstly, a few things about our engine. Snowmobile engines are two-stroke, and for our Yamaha V-Max 750, produces about 140hp (when new and running). They rotate in the "conventional" direction, same as most cars (except old hondas, I'll get back to this later). It drives another shaft through a set of gears which runs the primary sheave (or pulley) for the belt drive. Here's a picture so you get the idea:

The sheave here is on the left hand side of the picture. This runs a belt to another sheave, mounted on the jackshaft, which is just a regular shaft with a sheave on one end, a couple of bearings in the middle, and essentially what is the "final drive" on a snowmobile the details of which aren't important here.

In order to retain the CVT function of the snowmobile engine, we're planning to couple the jackshaft end of things to the car's transmission. This will mean making a new "jackshaft" which can couples to the splines on either the clutch or the input shaft of the transmission. Yes we haven't quite worked out the details here either.

If you're with me so far good. Now the engine drives the cvt, which drives the gearbox. Why retain the whole gearbox? We'll, for one its less machining, and less expensive stuff. Secondly, it allows us to retain the original differential and axles from the car. Since this is a budget build for an endurance racer, we're trying to minimise unproven and untested components. There are downsides too, which we'll have to deal with eventually.

The question has been asked if we're planning on shifting the transmission's gears as we drive. Likely not, we want the car to drive with the cvt as much as possible. Maybe we'll shift from one ratio to another, to give us a high-low range type of arrangement. Because the CVT effectively acts like a disengaged clutch when you're off the throttle, we probably won't need a clutch to shift gears. If we do retain the clutch it is for other reasons (which will be discussed eventually). This arrangement also gives us a reverse gear.

Now, for those of you who can visualise all of this with your head, congratulations. There is an design compromise to be made here with rotational directions here and how we choose to mount the engine. If we wanted to just take the front end of the Firefly and stick it in the back of the Geo (imagine a rear-end collision of sorts), then the snowmobile engine would have to be mounted offset from the center of the car, meaning it would have to be placed outside on the passenger side. obviously not a good thing. This has to do with how the car's transmission is placed. Look inside your hood (for a FWD), the engine is roughly on one side of the car, and the engine is on the other. In the case of our car, the engine is on the passenger's side, and the transmission on the driver's, everything being split roughly down the centerline of the car.

The way we will overcome this, is to place the firefly subframe backwards. Meaning that we're cutting the front of the Firefly and placing it back to back in the Geo. This allows us to keep the engine within the confines of the car body. Yes, everything should look "normal" from the outside. We have plans for the radiator and fuel tanks as well.

Now before somebody decides to put my idea to paper and see for himself/herself, this does mean we are going to be running the transmission in a reverse rotation as it would normally. Another way to put this is if your car engine were turning in the opposite direction as it would normally. If you've read this far I'm amazed. There are two points to be made about this.

Firstly, we could of used an old Honda, because they had everything backwards from the conventional positioning of things. This would have allowed us to run the transmission in it's normal orientation. However, we decided not to pursue this on the basis that even an old civic hatch (1991) is 4" wider than a Geo, this we feel would negate handling A LOT!

Secondly, for those of you who may know a thing or two about gears, is what exactly does it mean to run a transmission backwards. Well, helical gears produce thrust loads, axial to their shafts. This thrust load's direction is dependent on the rotational direction of the shaft. This affects bearings inside the transmission. Long story short, and you may feel free to ask me about it if you need clarification, but we need a transmission with thrust load capacity in both orientations. Picture below is from a 4 speed Swift transmission. Notice the tapered roller bearings at both ends.

I'm betting this is the same configuration found in our 5 speed. More research to be done on this soon...

Update: research suggests that the input shaft on the 5 speed has angular ball bearings, I hope this works.

What's the deal here... Part 4 ANOTHER CAR!

Well, After doing some measuring and checking, we have an issue. Let me explain. As I have stated before, we are intending on putting a snowmobile engine driving the rear wheels on a small hatchback. This is not an easy or intuitive thing to visualise, how do you actually get a drivetrain in the back. Firstly, I have no idea how this is all going to look like in the end at this point. Secondly, how to actually do this has been debated A LOT! We're trying something that is, I think, a new approach. There are certainly other ways of doing this, some may even be easier.

Back to my issue, the idea is to get the front subframe from another car, and stick it where the rear wheels would/should be on the Geo. Unfortunately, the Geo is a very small car, especially when it comes to width. Finding a donor car that is fairly narrow to fit in is no mean feat. We're pretty much limited to other small cars. Ideally we'd want something close to the same width to begin with, what better than the same car:

Behold, a 1992 Pontiac Firefly TURBO!!! 1litre of 3 cylinder turbocharged crap! Actually for sale, listed at 500$. We managed to get it for 150$. It doesn't run, is a complete rustbucket and would never, ever, no matter how much time/money you throw at it be restorable. It does have a few things of interest to us however:
  • A nice, still structurally sound front subframe, complete with axles, springs, dampers and an anti-roll bar
  • More wheels
  • Rear anti-roll bar
  • Great looking skirts, hood scoop and wing (this is really a joke, I don't like the look of this myself)
  • A functional 5 speed transmission and clutch
Yes, we did buy another crap car. Next post will be more technical on how this will all go together.

What's the deal here... Part 3 A CAR!!!

A short while after getting our snowmobile engine, and selling off bits from the wreck, we manage to recover our money. A free engine! There are a few issues, like one of the reed valve bolts snapped in the cylinder head. Somebody (previous owner) forgot to heat up the threadlocker used to keep it in place and was slightly overzealous with the wrench... Picture soon!!!

We had to take apart that cylinder, which is great because the whole engine has individual cylinder castings. Gotta love modular Yamaha design. Worst case we'll have to find a new cylinder casting.

Then came THE SCORE. Greg got us a wicked deal on a freeeeeeee 1994 geo metro with and autotragic transmission. It really was free, previous owner was junking it because its too expensive to fix.

The GOOD: Seems to have recently redone brakes, new lines, we even managed to get it started.

The BAD: Handbrake seized on us (we cut it). Driver's side floor is gone, the bottom of the rockers too and the windshield is cracked. Otherwise, its remarkably clean.

Conclusion, we've got a car, a non-running engine and no idea how to put it all together...

What's the deal here... Part 2! AN ENGINE!

Getting a better feel for the rules in these types of events. Generally, everything has to be safe, and in case it explodes (which it will), you should not die or be injured severely. Also, doing some research, we decide that both the GRM challenge and Lemons races tend to favour outlandish builds, ridiculous engine swaps and total mayhem.

The team discussions inevitably lead to small cars with powerful (big?) engines. I've personally always wanted to have a bike engined car. 900cc+ displacement, outrageous redline, lightweight, sequential gearbox, I could go on. Of course, being in Canada, finding a bike engine can easily, easily put us over the "500$" limit.

What we do have in Canada are snowmobiles, and lots of them. Some of the larger snowmobiles have engines producing 200 hp. These are also belt driven, through a CVT, which means they have no gears, which could be interesting.

We end up scoring a sweet deal on a wrecked and disassembled Yamaha V-max 750 for 100$. 140hp of two-stroke goodness, not running and in pieces.

What's the deal here... BEGINNING!

Alright, here's the first thought behind this madness: have you ever asked yourself what it would take to stuff an engine in the back of that crappy old hatchback you've been driving? Do you have dreams of powersliding rear wheel drive glory? Well I have, and have had for some time now.

Fast forward to late 2009, and I'm introduced to a magazine called Grassroots Motorsports and the GRM challenge . A few friends discuss this over beer, have a laugh and it pretty much ends there.

Later on, quietly on our own free time, we begin to research this crazy idea. Then pops up the 24 hours of Lemons. There's a good idea, a bunch of friends building and racing a ridiculous, cheap car. Perfect for us poor students/new homeowners...

A few weeks later I find myself seriously considering this.

For inspiration on the whole Lemons thing go here and here.